JP2014177522A - Pressure-sensitive adhesive sheet for optical substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet for an optical substrate, which has functions of improving visibility, giving high transparency, preventing scattering, and the like when the sheet is used for optical purposes, and thereby, which is suitable not only for manufacturing components of various displays but also for various optical applications.SOLUTION: A pressure-sensitive adhesive sheet for an optical substrate includes a pressure-sensitive adhesive sheet layer on both surfaces of a film substrate core having a coating layer obtained by applying a coating liquid containing polyvinyl alcohol on both surfaces of a polyester film. When a float plate glass having 1 mm thickness is laminated to a surface of each pressure-sensitive adhesive sheet layer, the pressure-sensitive adhesive sheet shows transparency of 70% or more and image clarity of 85% or more. A release film is applied on both surfaces of the pressure-sensitive adhesive sheet layer, in which an intermediate layer excluding an outermost layer of at least one polyester film constituting the release film contains a laser marking compound.

Description

  Since the present invention has functions such as high transparency and scattering prevention when the pressure-sensitive adhesive sheet for an optical substrate is used for optical applications, for example, for producing liquid crystal components such as a touch panel, a liquid crystal polarizing plate, a retardation plate, The present invention relates to an adhesive sheet for an optical substrate suitable for various optical applications and the like, as well as for the production of various display components such as for the production of PDP components and for the production of organic EL components.

  Conventionally, various pressure-sensitive adhesive sheets for surface bonding between objects are known, and a base-less double-sided pressure-sensitive adhesive sheet is known as one of pressure-sensitive adhesive sheets.

  The substrate-less double-sided pressure-sensitive adhesive sheet is configured by laminating a light release sheet having a relatively low peeling force and a heavy release sheet having a relatively high peeling force on both sides of the pressure-sensitive adhesive layer, and removing the double-sided release sheet. The latter is a double-sided pressure-sensitive adhesive sheet that only has a pressure-sensitive adhesive layer that does not have a supporting substrate.

  The baseless double-sided PSA sheet is first peeled off from the light release release film, and one side of the exposed PSA layer is bonded to the object surface. Then, the other surface of the exposed pressure-sensitive adhesive layer is bonded to a different object surface, whereby the objects are surface-bonded. In the process of bonding to another object, the balance of the peeling force between the light peeling side and the heavy peeling side is important.

  In recent years, the baseless double-sided pressure-sensitive adhesive sheet is being used for various optical applications and the like. For example, when the electronic base material and the glass on the surface of the touch panel are bonded to each other as a touch panel member, defects such as a foreign substance of an adhesive remaining as a base material are more important than ever. Foreign matter reduction must be achieved for both the adhesive and the film substrate.

  In addition, in the process of bonding the substrate-less double-sided PSA sheet to the member, the release film with a light peeling force is first peeled off. However, when the release films on both sides have the same thickness, the release film made of a colorless and transparent polyester film Then, it has a problem that it is difficult to determine which surface has a release film having a light peeling force. In this case, a technique of using a colored film as a release film can be considered.

  Also, in such applications, one of the release films may be peeled off, and the foreign material, dirt, and scratches may be inspected when pasted to another member while leaving the remaining release film on the heavy release side. There is a case. At that time, if a colored film is used for the release film, there is a possibility that the transmittance and the visibility are lowered, and there is a high possibility that a defect is caused during the above inspection. Desirably, it is desirable to apply a technique such as coloring only under a certain condition, that is, coloring only the laser irradiation part, coloring only the UV irradiation part, or emitting only the UV irradiation part. There are many hurdles to overcome.

  One of the hurdles to be exceeded is that the color pigment or dye to be selected requires sufficient heat resistance during film production through the melting step. In order to maintain the optical properties of the film, an organic compound having a relatively low molecular weight is often selected. In that case, it decomposes immediately by heat applied in the melting process, for example, 200 ° C. or higher, or When passing through the melting process many times, if the deterioration is severe, it is not suitable as a material.

  Another hurdle to overcome is the bleeding out of the colored pigment or dye to the adhesive material that occurs when using the colored pigment or dye. The low molecular weight component used may pass through the polymer film and transfer to the adhesive material, thereby adversely affecting the adhesive material component. Such adverse effects become a problem in particularly severe applications among polarizing plates and touch panel members.

  Applying the technology of the base-less double-sided pressure-sensitive adhesive sheet shown above, and sandwiching it in a highly transparent film base, reduces the cost and thickness of the pressure-sensitive adhesive. Development is required.

  In the case of using glass on the outer surface of some touch panels, TVs, and the like, such an adhesive sheet for an optical substrate has a scattering prevention function. Moreover, in the case of the use which uses glass for outer surfaces, such as a touch panel and TV, such an adhesive sheet for optical base materials has an impact absorption function. Further, in applications where the pressure-sensitive adhesive has multiple functions, such as high transparency for the first pressure-sensitive adhesive, high refraction for the second pressure-sensitive adhesive, etc., it can be used as a variety-rich additional function pressure-sensitive adhesive.

  The technical barrier of the pressure-sensitive adhesive sheet for optical substrates of the above uses is in the optical properties of the film used as the film substrate (the role of the core), and compared with the sheet of pressure-sensitive adhesive alone, the light transmittance, haze and It is required that there is no significant optical loss or change in appearance due to the refractive index.

  Also, from the viewpoint of visibility, due to the influence of the lubricant used for the film substrate, the aggregation of particles often shows the original granular feeling under transmitted light. Many things are noticeable near the human eye. For this reason, the improvement in the visibility resulting from the graininess is one of the problems to be solved with a very high technical barrier.

JP 2000-338327 A JP 2009-161574 A Japanese Patent Application No. 2011-86860 JP 2009-220296 A JP 2009-214360 A JP 2006-305915 A Japanese Patent Application No. 2011-208327 JP 2010-189504 A JP 2010-174135 A JP 2010-174086 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is that when the pressure-sensitive adhesive sheet for optical substrates is used for optical applications, it has functions such as improved visibility, high transparency, and prevention of scattering. Suitable for manufacturing various display components, such as for manufacturing liquid crystal components such as touch panels, liquid crystal polarizing plates, retardation plates, for manufacturing PDP components, for manufacturing organic EL components, etc. It is providing the adhesive sheet for optical base materials.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problem can be easily solved by a polyester film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is a pressure-sensitive adhesive sheet having pressure-sensitive adhesive sheet layers on both sides of a film substrate core having a coating layer obtained by applying a coating liquid containing polyvinyl alcohol on both sides of a polyester film. The transparency of the pressure-sensitive adhesive sheet is 70% or more when the 1 mm-thick float plate glass is bonded to each surface of the sheet layer, the image clarity is 85% or more, and release films are provided on both sides of the pressure-sensitive adhesive sheet layer. And a laser marking compound is contained in the intermediate layer excluding the outermost layer of at least one polyester film.

  According to the present invention, by sandwiching a polyester film, it is usually less expensive, necessary transparency, and excellent in visibility than an adhesive of the same thickness. The pressure-sensitive adhesive sheet for an optical substrate having a preventive effect can be provided, and the industrial value of the present invention is high.

Typical sectional drawing which shows the adhesive sheet for optical base materials which concerns on embodiment of this invention Typical sectional drawing which shows the precursor of the 1st and 2nd base material less double-sided adhesive sheet layer which comprises the adhesive sheet 10 for optical base materials

  As shown in FIG. 1, the optical substrate pressure-sensitive adhesive sheet 10 is formed by laminating the first and second substrate-less double-sided pressure-sensitive adhesive sheets on both surfaces of a film substrate core 31. The The first release film 32 of the first substrate-less double-sided pressure-sensitive adhesive sheet 41 bonded to the film substrate core 31 having the film substrate coating layers 12 and 12 'on both sides is a so-called light release sheet, and is made of a polyester film. The release film substrate 14, the coating layer 15, and the first release agent layer 16 are configured to be laminated, and the first release agent layer 16 is temporarily attached to the pressure-sensitive adhesive layer 13 in a peelable manner. Furthermore, the second release film 33 of the second substrate-less double-sided pressure-sensitive adhesive sheet 42 bonded to the film substrate core 31 is a so-called heavy release sheet, which is a release film substrate 24 made of a polyester film, and a coating layer 25. The second release agent layer 26 is laminated, and the second release agent layer 26 is temporarily attached to the pressure-sensitive adhesive layer 23 in a peelable manner.

  As shown in FIG. 2, the first base-less double-sided pressure-sensitive adhesive sheet precursor 41 ′ is configured by laminating first and first ′ release films on both sides of the pressure-sensitive adhesive layer 13. The first release film 32 bonded to the pressure-sensitive adhesive layer 13 is a so-called heavy release sheet as compared to the first 'release film 32', and is a first release film substrate 14 made of a polyester film, and a first application. The layer 15 and the 1st mold release agent layer 16 are laminated | stacked, and the 1st mold release agent layer 16 is temporarily attached to the adhesive layer 13 so that peeling is possible. Further, the first 'release film 32' bonded to the pressure-sensitive adhesive layer 13 is a so-called light release sheet as compared with the first release film 32, and is a first 'release film substrate 14' made of a polyester film. The first 'release layer 15' and the first 'release agent layer 16' are laminated, and the first 'release agent layer 16' is temporarily attached to the pressure-sensitive adhesive layer 13 in a peelable manner.

  Further, as shown in FIG. 2, the second base-less double-sided pressure-sensitive adhesive sheet precursor 42 ′ is configured by laminating a second and second ′ release film on both sides of the pressure-sensitive adhesive layer 23. The second release film 33 bonded to the pressure-sensitive adhesive layer 23 is a so-called heavy release sheet as compared with the second 'release film 33', and is a second release film substrate 24 made of a polyester film, a second application. The layer 25 and the 2nd mold release agent layer 26 are laminated | stacked, and the 2nd mold release agent layer 26 is temporarily attached to the adhesive layer 23 so that peeling is possible. Further, the second 'release film 33' bonded to the pressure-sensitive adhesive layer 23 is a so-called light release sheet as compared with the second release film 33, and is a second 'release film substrate 24' made of a polyester film. The second 'application layer 25' and the second 'release agent layer 26' are laminated, and the second 'release agent layer 26' is temporarily attached to the adhesive layer 23 in a peelable manner.

  The film substrate in the present invention may be a polymer film characterized by high transparency and low haze as optical characteristics. In particular, in the present invention, it is particularly preferable to use a polyester excellent in the above characteristics, inexpensive and excellent in workability.

  The polyester film referred to in the present invention is a film which is melt-extruded from an extrusion die, and is subjected to stretching and heat treatment as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method.

  The polyester forming the base material used for the release films 32, 32 'and 33' is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. The polyester used may be a homopolyester or a copolyester. In the case of a copolyester, it may be a copolymer containing 30 mol% or less of the third component. Examples of the dicarboxylic acid component of such a copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more chosen from are mentioned. One glycol component includes one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  In the polyester obtained by the present invention, a weathering agent, a light-proofing agent, an antistatic agent, a lubricant, a light-shielding agent, an antioxidant, a fluorescent whitening agent, a matting agent, and a heat-stabilizing agent as long as the gist of the present invention is not impaired. You may mix | blend an agent and coloring agents, such as dye and a pigment.

  Examples of the particles to be blended in the film include silicon oxide, alumina, calcium carbonate, kaolin, titanium oxide, and crosslinked polymer fine powder as described in JP-B-59-5216. These particles may be used alone or in combination of two or more components. The blending amount of these particles is usually 1% by weight or less, preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the film. When the content of the particles is small, the film surface cannot be appropriately roughened, and in the film production process, there is a tendency that the surface is easily scratched or the winding properties are inferior. On the other hand, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large and the transparency is impaired.

  Although it does not specifically limit as an average particle diameter of the particle | grains mix | blended in the polyester film used for release film 32, 32 ', and 33', Usually, 0.02 micrometer-5 micrometers, Preferably it is 0.02 micrometer-3. It is 5 μm, more preferably in the range of 0.02 μm to 3.2 μm. When particles having an average particle size of less than 0.02 μm are used, sufficient slipperiness cannot be imparted, so that the winding characteristics in the film production process are inferior. On the other hand, when the average particle size exceeds 5 μm, the degree of roughening of the film surface increases and the haze of the film increases.

  On the other hand, in order to improve the transparency of the film, when a laminated film of two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers. The blending amount of the particles in the case of such a laminated film is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the surface layer.

  In addition, a sharp particle size distribution is preferably used. Specifically, those having a particle size distribution value of 1.0 to 2.0, which is an index representing the sharpness of the particle size distribution, are preferable. Here, the particle size distribution value is the particle size distribution value d25 / d75 (d25 and d75 are calculated by calculating the accumulated accumulation of the particle group from the large particle side, and the particle size (μm corresponding to 25% and 75% of the total volume, respectively) Is a value defined by When the particle size distribution value exceeds 2.0, the transparency becomes insufficient.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dL / g or more, and more preferably 0.40 to 0.90 dL / g.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, it is not specifically limited to the following illustrations.

  First, the preferable example of the manufacturing method of polyester used by this invention is demonstrated. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used. According to a conventional method, esterification from terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol is carried out, the product is transferred to a polymerization tank, the temperature is increased while reducing the pressure, and finally vacuum is applied. Under heating to 280 ° C., the polymerization reaction proceeds to obtain polyethylene terephthalate.

Next, for example, the polyester chip obtained as described above and dried by a known method is supplied to a melt-extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from the die, and rapidly cooled and solidified on the rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is stretched biaxially to form a film.
Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. Furthermore, it is also possible to perform simultaneous biaxial stretching of the unstretched sheet so that the area magnification is 10 to 40 times.

  The thickness of the release film of the present invention is not particularly limited as long as it can be formed as a film and can be processed as a release film, but is usually 10 to 300 μm, preferably 30. It is -188 micrometers, More preferably, it is the range of 50-75 micrometers. If the film thickness is less than 10 μm, the film is not stiff, a foreign matter in the process is transferred, and a trouble occurs in the process of peeling the release film. When the film thickness exceeds 300 μm, the productivity is lowered during film formation and processing, and the production cost increases.

  Although the manufacture example of the polyester film used as the base material of the release film 33 of this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.

  That is, in the case of a polyester film composed of three layers using the polyester raw material described above, a plurality of extruders, a multi-layer multi-manifold die or a feed block are used to laminate the respective polyesters, and the die A method in which a multi-layered molten sheet is extruded from and cooled and solidified with a cooling roll to obtain an unstretched sheet is preferred.

  In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the release film. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and stretch ratio. As an area magnification, it is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  The present invention is characterized in that a polyester film used for one release film laminated on both surfaces of a pressure-sensitive adhesive sheet is colored partially and when necessary by laser irradiation. The film of the present invention is characterized by being irreversibly colored by laser light.

  If you decide in advance whether to use a polyester film that is colored by laser light on the light release side or the heavy release side, there is no need to remove the release film from the adhesive sheet, making it easy to identify the release film, It is possible to prevent mistakes in the joining process.

  In the member joining step, conditions such as the speed at which the release film is peeled off are set in accordance with the peeling force of the release film.

  For the polyester film used in the present invention, it is preferable to use a method in which a compound that is colored by laser light (hereinafter referred to as a laser marking compound) is contained during the extrusion of the polyester.

  As a specific example of the laser marking compound, the metal oxide is preferably at least one selected from a copper compound, a molybdenum compound, an iron compound, a nickel compound, a chromium compound, a zirconium compound and an antimony compound. More preferably, it is at least one selected from compounds. In addition, supplementary use and use of inorganic metal compounds such as titanium oxide, zinc sulfide, zinc oxide, precipitated barium sulfate, barium carbonate and precipitated calcium carbonate and dyes such as carbon black, graphite and black lake, and leuco dye It is desirable to select and use it according to the environment.

In this invention, when a laser marking compound is kneaded in a film, content of the compound colored with the laser beam in a film is the range of 0.025 to 0.25 weight%. When the content is less than 0.025% by weight, the discoloration effect of the film is inferior. On the other hand, when it contains exceeding 0.25 weight%, a malfunction arises with the degraded material in a film.

  Next, examples of the method for incorporating the laser marking compound into the polyester in the present invention include a kneading method and a coating method. When the method of kneading into polyester is used, these compounds are preferably used as a masterbatch kneaded into polyester resin, but may be added directly to the polyester resin.

  Further, in the kneading of the laser marking compound into the polyester, the compound belongs to an organic compound or an organometallic complex, and is generally known to have low heat resistance around 300 ° C. In the present invention, it is necessary to appropriately select a compound having heat resistance that can withstand a high amount of heat at the time of forming a polyester film or at the time of heat history in raw material recycling. One of the features of the laser marking compound of the present invention is that it is excellent in heat history characteristics that repeats regeneration.

  Furthermore, about the polyester film in this invention, the layer structure of the laser marking compound knead | mixing to an intermediate | middle layer except an outermost layer is preferable. In that case, what is necessary is just to adjust content of a surface layer or an intermediate | middle layer so that it may become said content as the whole film. When kneaded into the surface layer, a double-sided pressure-sensitive adhesive sheet is formed, and when stored for a long time, the kneaded compound bleeds out and shifts to the adhesive material side. In the present invention, bleed out refers to a phenomenon in which a low molecular compound migrates to the film surface layer.

  In some applications, the release film used in the present invention may be subjected to a visual inspection of polarized light such as a scratch or a foreign substance or an in-line polarized light inspection after peeling the light release sheet and bonding it to a member to be used. In this case, in order to realize high inspection properties, the orientation angle of the film is required to have a low orientation angle. The orientation angle at this time is an index that qualitatively represents the direction in which molecular chains are aligned with respect to the longitudinal direction after stretching. In addition, as other elements for realizing high inspectability, there are few foreign matters inside and outside the film and low haze. The film haze is usually 10% or less, preferably 8% or less, more preferably 5% or less. The substrate-less double-sided pressure-sensitive adhesive sheet of the present invention is used for optics, so if there are defects such as foreign matter, it must be removed by visual inspection or an automatic defect detector, etc., but the film haze exceeds 10% Hinders the detection of defects in foreign matter and the like.

  In the present invention, it is preferable to use release films having different thicknesses on both sides of the substrate-less double-sided pressure-sensitive adhesive sheet. Specifically, the thickness of the second release film is the thickness of the first release film. Is preferably 1.2 times or more, more preferably 1.4 times or more. By reducing the film thickness of the first release film on the light release side, it is possible to prevent the floating that occurs at the interface between the second release film and the adhesive layer when the first release film is peeled off. The above phenomenon of floating refers to a phenomenon in which the peeling force is weak at the time of peeling, and part of the pressure-sensitive adhesive layer peels off, bites air or the like, and the appearance deteriorates.

  In addition, when the adhesive is applied on the release surface of the release film, it is more susceptible to unevenness and foreign matter when manufacturing costs are taken into account to eliminate the influence of foreign matter and unevenness in the process. It is preferable to increase the film thickness of the second release film.

  The ratio of the thickness of the release film on the light release side and the thickness of the release film on the heavy release side is preferably larger than 1.2 times, and if it is less than 1.2 times, the contribution to cost is reduced.

  In this invention, in order to prevent the compound added in order to give the laser coloring function mentioned later to bleed out, it is preferable to provide a coating layer in both outermost layer surfaces of the layer which consists of polyester. The coating layer also has an inhibitory effect on oligomers precipitated from polyester (hereinafter abbreviated as OL). In the present invention, an oligomer is defined as a cyclic trimer among low molecular weight substances that crystallize and precipitate on the film surface after heat treatment.

  In the present invention, a film having a structure in which a polyester having a low OL content is coextruded and laminated on at least one surface of a layer composed of a polyester having a normal OL content may be used. In the polyester film for release film obtained by the invention, the effect of preventing the bright spot due to the precipitated OL is obtained, which is particularly preferable.

  In the present invention, the method for forming the release film coating layers 15 and 15 'or the coating layers 25 and 25', and the film base coating layers 12 and 12 'for preventing OL coating are not particularly limited. A method of applying a coating solution in the process of producing a polyester film is suitably employed. Specifically, a method of applying and drying a coating solution on the surface of an unstretched sheet, a method of applying and drying a coating solution on the surface of a uniaxially stretched film, and a method of applying and drying a coating solution on the surface of a biaxially stretched film Etc. Among these, it is economical to apply a coating solution on the surface of an unstretched film or a uniaxially stretched film, and then simultaneously dry and cure the coating layer in the process of heat-treating the film. Moreover, as a method for forming the coating layer, a method in which some of the above-described coating methods are used in combination can be adopted as necessary. Specifically, a method of applying a first layer on the surface of an unstretched sheet and drying, then stretching in a uniaxial direction, and then applying and drying a second layer can be used. Use the reverse roll coater, gravure coater, rod coater, air doctor coater, etc. shown in “Coating Method” by Yuji Harasaki, Tsuji Shoten, published in 1979, as a method of applying the coating solution to the surface of the polyester film. Can do.

  The coating solution used in the present invention is usually preferably adjusted with water as the main medium from the viewpoint of safety and hygiene. As long as water is the main medium, a small amount of an organic solvent may be contained for the purpose of improving the dispersion in water or improving the film forming performance. The organic solvent is preferably used as long as it is dissolved in water when mixed with water, which is the main medium. However, if it is a stable emulsion (emulsion) that does not separate after standing for a long time, Alternatively, it may be used in a state where it does not dissolve in water. The organic solvent may be used alone or in combination of two or more as necessary.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  In the present invention, it is usual to use a binder polymer for the coating layers 15 and 15 'or the coating layers 25 and 25', and the film base coating layers 12 and 12 '. In accordance with the compound safety evaluation flow scheme (sponsored by the Chemical Substances Council in November 1985), a polymer compound having a number average molecular weight (Mn) of 1000 or more by gel permeation chromatography (GPC) measurement, and film formation It is defined as having sex.

  Analysis of the components in the coating layer can be performed by surface analysis such as TOF-SIMS.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  In order to achieve the above object, in the present invention, an OL precipitation preventing layer is formed on the film surface by coating, and the layer comprises 10 to 100% by weight of polyvinyl alcohol, preferably 20 to 90% by weight, more preferably 30 to 30%. It shall contain 90% by weight. If the content of polyvinyl alcohol is less than 10% by weight, the oligomer sealing effect is insufficient, which is not preferable.

  The polyvinyl alcohol used in the present invention can be synthesized by a normal polymerization reaction and is preferably water-soluble. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is 100 or less, the water resistance of the coating layer tends to decrease. The degree of saponification of the polyvinyl alcohol used in the present invention is not particularly limited, but a polyvinyl acetate saponified product that is usually 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is practically used. It is done.

  In the coating layers 15 and 15 ′ or coating layers 25 and 25 ′ and the film base coating layers 12 and 12 ′ in the present invention, a water-soluble or water-dispersible binder other than the above-described polyvinyl alcohol, if necessary. A resin may be used in combination. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, acrylate resin, and the like. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, vinyl resin graft polyurethane, and acrylate resin graft polyethylene glycol. The blending amount of the binder component is preferably 50 parts by weight or less, and more preferably 30 parts by weight or less in terms of parts by weight with respect to the coating layer. Furthermore, the coating layer of the film of the present invention may contain a crosslinking reactive compound as required.

  Crosslinking reactive compounds include methylolated or alkylolated urea, melamine, guanamine, acrylamide, polyamide and other compounds, polyamines, epoxy compounds, oxazoline compounds, aziridine compounds, blocked isocyanate compounds, silane cups Polyfunctional low molecular weight compounds such as ring agents, titanium coupling agents, zirco-aluminate coupling agents, metal chelates, organic acid anhydrides, organic peroxides, thermally or photoreactive vinyl compounds and photosensitive resins, and It is selected from polymer compounds.

  Crosslinkable compounds improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the easy-adhesive resin layer mainly by cross-linking reaction with the functional groups of the resin contained in the easy-adhesive resin layer. can do. For example, when the functional group of the easily adhesive resin is a hydroxyl group, the crosslinking reactive compound is preferably a melamine compound, a blocked isocyanate compound, an organic acid anhydride, or the like, and the functional group of the easily adhesive polyester is an organic acid or an anhydride thereof. In this case, epoxy-based compounds, melamine-based compounds, oxazoline-based compounds, metal chelates and the like are preferable as the cross-linking reactive compound. It is preferable to select and use a functional group contained in the easily adhesive resin and one having a high crosslinking reaction efficiency. Examples of the melamine compound in the present invention include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. .

  The cross-linking reactive compound may be either a low molecular weight compound or a high molecular polymer having a reactive functional group as long as the reactive functional group is always contained in two or more functional groups in one molecule. The compounding amount of the crosslinking reactive compound is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight or less in terms of parts by weight with respect to the easily adhesive resin layer. Furthermore, the easily adhesive resin layer of the present invention may contain inert particles for improving the slipperiness of the coating layer, if necessary.

Examples of the inert particles include inorganic inert particles and organic inert particles. Examples of the inorganic inert particles include silica sol, alumina sol, calcium carbonate, and titanium oxide.
Examples of the organic inert particles include fine particles containing a single or copolymer of polystyrene resin, polyacrylic resin, and polyvinyl resin, or organic particles represented by crosslinked particles in which these and a crosslinking component are combined. These inert particles preferably have a softening temperature or decomposition temperature of about 200 ° C. or higher, more preferably 250 ° C. or higher, particularly 300 ° C. or higher. The average particle diameter (d) of the inert particles is 1/3 ≦ d / L ≦ 3, and further 1/2 ≦ d / L ≦ 2, when the average film thickness of the easily adhesive resin layer is (L). It is preferable to select so as to satisfy the relationship.

  The coating layers 15 and 15 ′ or the coating layers 25 and 25 ′ of the present invention and the film base coating layers 12 and 12 ′ may be a surfactant, an antifoaming agent, a coating property improving agent, a thickening agent, if necessary. A small amount of additives such as an agent, a low molecular weight antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, and a pigment may be contained. These additives may be used alone or in combination of two or more as necessary. The coating layer of the film of the present invention may be formed only on one side of the polyester film or on both sides. In the case of forming only on one side, another type of coating layer can be formed on the opposite side as required, and further properties can be imparted. In addition, in order to improve the applicability | paintability and adhesiveness to the film of a coating liquid, you may give a chemical process, an electrical discharge process, etc. to the film before application | coating.

Respect polyester film of the present invention, the thickness of the coating layer provided on the polyester film is usually 0.002~1.0g / ^{m 2,} more preferably 0.005 to 0.5 / ^{m 2,} more preferably 0 The range is from 0.01 to 0.2 g / m ² . When the film thickness is less than 0.002 g / m ^2, sufficient adhesion may not be obtained, and when it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties deteriorate.

  In the present invention, the drying and curing conditions for forming the coating layers 15 and 15 ′ or the coating layers 25 and 25 ′ and the film base coating layers 12 and 12 ′ on the polyester film are particularly limited. However, for example, when the coating layer is provided by off-line coating, the heat treatment is usually performed at 80 to 200 ° C. for 3 to 40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  The polyester film coating layers 15 and 15 ′ or coating layers 25 and 25 ′ and the film base coating layers 12 and 12 ′ of the present invention are formed by blending a binder resin and a crosslinking agent in an arbitrary ratio. In this case, since the barrier layer is densely formed, the OL can be suppressed. For this reason, there is an effect that OL from the polyester film is not attached to the adhesive as much as possible and is not produced in the previous processing step. Therefore, the layer structure of the coating layer 15 or the coating layer 25 of the polyester film of the present invention is preferably double-sided, and it is necessary to apply to at least one side according to the application. However, the component contained in the coating layer inhibits the curing reaction during the release layer film formation. In the present invention, in order to eliminate this curing inhibition, the catalyst amount is adjusted to keep the release performance. Moreover, the polyester film used for the film base material of the present invention has a structure in which an adhesive is attached to both sides, and becomes a member that remains until the end of the product, and is particularly harsh on foreign matters. For this reason, the layer structure of the coating layer 12 needs to be coated on both sides.

  The release film used for the pressure-sensitive adhesive sheet for an optical substrate of the present invention is formed by providing at least a biaxially oriented polyester film (release film substrate) and a release agent layer in this order. In order to prevent production process contamination, it is preferable to provide a coating layer which is an OL sealing layer. In that case, the biaxially oriented polyester film 14, the coating layer 15, and the release agent layer 16 are provided in this order.

  When the coating layer is not provided, OL is likely to occur in the production process of the release film and the double-sided pressure-sensitive adhesive sheet, and in the process of bonding the pressure-sensitive adhesive sheet for optical substrates to other members. It is not preferable.

  In the substrate-less double-sided pressure-sensitive adhesive sheet used in the pressure-sensitive adhesive sheet for optical substrates of the present invention, for example, after the pressure-sensitive adhesive is coated on the release layer of the release film, the pressure-sensitive adhesive layer is formed by drying. Next, a release film having a different peeling force is laminated on the release layer, but when the coating layer is not provided, other process contamination is caused by OL generated in the manufacturing process. In addition, when the pressure-sensitive adhesive layer is bonded to the electronic substrate, it is not preferable because a problem occurs in the electronic component due to the influence of OL.

In the present invention, when the release film has a coating layer, after heat-treating those release films (180 ° C., 10 minutes), the amount of OL extracted from the release layer surface with the coating layer by dimethylformamide is: It is preferably 1.0 mg / m ² or less. When OL exceeds 1.0 mg / m ² , there is a process contamination, and when the adhesive is bonded, foreign matter is generated, resulting in problems such as a decrease in product yield.

  In addition, in the release film of the pressure-sensitive adhesive sheet for optical substrates of the present invention, in order to have a further surface function, the coating layer to be formed is an easy adhesion layer, an antistatic layer, or an antistatic easy adhesion layer. It is preferable to have.

  The release coating layers 16 and 16 ′ or the coating layers 26 and 26 ′ provided on the coating layer or film in the present invention are particularly limited as long as they contain a releasable material. It is not something. Among them, the one containing a curable silicone resin is preferable because the releasability is improved. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

  As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used.

  The silicone used in the film 32 on the light release side used in the present invention is based on the concept of light release due to the migration component of the silicone, and the realization of low release rate dependency.

  In the present invention, the migratory component is a low molecular weight silicone compound mainly having a molecular weight of 1000 or less, and indicates a silicone resin having an alkenyl group and an alkyl group as functional groups. Examples thereof are as follows. Is mentioned. That is, first, the curable silicone resin containing an alkenyl group is a diorganopolysiloxane having a trimethylsiloxy group-blocked dimethylsiloxane / methylhexenylsiloxane copolymer (96 mol% of dimethylsiloxane units, methylhexenylsiloxane units 4). Mol%, dimethylvinylsiloxy group-blocked dimethylsiloxane / methylhexenylsiloxane copolymer (97 mol% dimethylsiloxane unit, 3 mol% methylhexenylsiloxane unit), dimethylsiloxane with dimethylhexylsiloxy group blocked at both ends of molecular chain And methyl hexenyl siloxane copolymer (95 mol% of dimethyl siloxane units, 5 mol% of methyl hexenyl siloxane units). As the nohydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain both ends dimethylhydrogensiloxy group-blocked Examples include methyl hydrogen polysiloxane, dimethyl hydrogen siloxy group-blocked dimethyl siloxane / methyl hydrogen siloxane copolymer, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, etc. In addition to the former low-molecular-weight cyclic siloxane, a trimethylsiloxy group-blocked dimethylsiloxane oligomer at both ends of the molecular chain; The Shishirokishi group-blocked dimethylsiloxane oligomers may be mixed as necessary.

  Further, in the present invention, silicone oil may be added in addition to the above compound in order to impart migration. The silicone oil is a silicone oil called a straight silicone oil or a modified silicone oil, and examples thereof include the following. Examples of the straight silicone include dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, and the like. Further, as modified silicone oil, side chain type polyether modified, aralkyl modified, fluoroalkyl modified, long chain alkyl modified, higher fatty acid ester modified, higher fatty acid amide modified, polyether / long chain alkyl modified / aralkyl modified, Examples include phenyl modification, polyether modification at both ends, and polyether / methoxy modification.

  These silicone oils are preferably contained in the silicone resin in an amount of 0.1 to 5.0% by weight as a migration component. Both straight silicone oil and modified silicone oil are non-reactive, non-functional oils.

  The migration component contained in the silicone resin used in the present invention is in the range of 5 to 20% by weight, preferably 10 to 13% by weight. If the content of the transition component is lower than 5%, the speed dependency becomes high, and if it exceeds 20% by weight, the curability is remarkably lowered and the adhesion is also deteriorated.

  Specific examples of the curable silicone resin include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-manufactured by Shin-Etsu Chemical Co., Ltd. 62-2461, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210 manufactured by Dow Corning Asia Co., Ltd. YSR-3022, TPR-6700, TPR-6720 manufactured by Toshiba Silicone Co., Ltd. , TPR-6721, SD 7220, SD 7226, SD 7229 manufactured by Toray Dow Corning Co., Ltd., and the like. Further, a release control agent may be used in combination to adjust the release property of the release layer. Further, as described above, a silane compound having an amino group may be added to the release layer.

In the present invention, as a method of providing the release coating layers 16 and 16 'or the release coating layers 26 and 26' on the polyester film, a conventionally known method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, etc. A coating method can be used. The application amount of the release layer in the present invention is usually in the range of 0.01 to 1 g / m ² .

  In the present invention, coating layers such as an adhesive layer, an antistatic layer, and an oligomer precipitation preventing layer are provided on the surface on which the release coating layers 16 and 16 'or the release coating layers 26 and 26' are not provided. In addition, the polyester film may be subjected to surface treatment such as corona treatment or plasma treatment.

  Also, drying and / or curing (thermal curing, ionizing radiation curing, etc.) of the pressure-sensitive adhesive layer or the release layer coating can be performed individually or simultaneously. When performing simultaneously, it is preferable to carry out at the temperature of 80 degreeC or more. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. If the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is incompletely cured, and the coating film tends to fall off.

  In order to make the coated layer of the polyester film of the present invention clean and strong, a transition metal catalyst that promotes an addition-type reaction is used. In the present invention, the transition metal catalyst in the coating layer is preferably a catalyst using platinum. In addition to platinum, transition metals used as a catalyst include titanium, zirconium, chromium, nickel, copper, cobalt, iron, Manganese, molybdenum, palladium, ruthenium, rhodium, silver, gold, iridium and the like are preferably used.

  The platinum catalyst used in the present invention includes chloroplatinic acid, an alcohol solution of chloroplatinic acid, a platinum compound such as a complex of chloroplatinic acid and an olefin, a complex of chloroplatinic acid and an alkenylsiloxane, platinum black And platinum-supported silica and platinum-supported activated carbon. The platinum-based catalyst content in the release layer is in the range of 0.5 to 5.0% by weight, preferably 1.5 to 4.0% by weight. When the content of the transition metal catalyst in the coating layer is lower than 0.5% by weight, there may be a problem such as deterioration of the surface condition due to insufficient peeling force or insufficient curing reaction in the coating layer. On the other hand, if the content of the transition metal catalyst in the coating layer exceeds 5.0% by weight, the cost is increased, the reactivity is increased, and process defects such as generation of gel foreign matter are caused. End up.

  In addition, since the addition-type reaction is very reactive, acetylene alcohol may be added as an unreactive inhibitor in some cases. The component is an organic compound having a carbon-carbon triple bond and a hydroxyl group, and preferably 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol and phenylbuty It is a compound selected from the group consisting of nor.

  In the present invention, the release force of the polyester film having the release coating layers 16 and 16 'or the release coating layers 26 and 26' is a double-sided adhesive tape ("No. 502" manufactured by Nitto Denko) on the release layer surface. The value is shown by a value measured with a tensile tester when the tape is peeled off at an arbitrary pulling speed at a peeling angle of 180 ° after being pasted and left at room temperature for 1 hour. In the present invention, a method for adjusting a specific peeling force can be achieved by selecting a composition in the release layer, but other means can also be adopted, mainly of a release agent for the silicone release layer. It is preferable to change the type according to the desired peeling force. Furthermore, since the peeling force largely depends on the application amount of the release agent to be used, a method of adjusting the application amount of the release agent is more preferable.

  In the pressure-sensitive adhesive sheet 10 for optical substrates of the present invention, the first substrate-less double-sided pressure-sensitive adhesive sheet 41 having the first release film 32 that is a light release sheet, that is, the first substrate-less double-sided pressure-sensitive adhesive sheet precursor 41 ′. No. of the first release film 31. The 180 ° peeling force in a 502 tape, 300 mm / min speed range is usually 20 to 40 mN / cm, preferably 25 to 35 mN / cm. If the peeling force of the first release film 32 is less than 20 mN / cm, the peeling force is close when peeling the first release film 32 ′, so that zipping occurs. Moreover, when the peeling force of the 1st release film 32 exceeds 40 mN / cm, the peeling force with the 2nd release film 33 is the process which produces the optical base material sheet 10 and bonds it to another member. However, it is close, so that zipping occurs, or the peeling force of the second release film 33 must be increased, which causes cohesive failure of the adhesive 23.

  In the present invention, the first release film 32 of the first substrate-less double-sided pressure-sensitive adhesive sheet precursor 41 ′ has No. The 180 ° peeling force in a 502 tape, 300 mm / min speed range is usually 20 to 40 mN / cm, preferably 25 to 35 mN / cm. When the peeling force of the first release film 32 is less than 20 mN / cm, zipping occurs because the peeling force is close when peeling the first 'release film 32'. Moreover, when the peeling force of the 1st release film 32 exceeds 40 mN / cm, the peeling force with the 2nd release film 33 is the process which produces the optical base material sheet 10 and bonds it to another member. Because of the proximity, zipping occurs, or the peeling force of the second release film 33 must be increased, causing cohesive failure of the adhesive 23.

  In the present invention, No. 1 of the first 'release film 32' of the first substrate-less double-sided pressure-sensitive adhesive sheet precursor 41 'is used. The 180 ° peeling force in a 502 tape, 300 mm / min speed region is usually 3 to 50 mN / cm, preferably 5 to 25 mN / cm, and more preferably 10 to 20 mN / cm. If the release force of the first release film is less than 3 mN / cm, the release film is easily peeled off, so that the release film is peeled off with a slight external force generated in the manufacturing process. Moreover, when the peeling force of a 1st release film exceeds 50 mN / cm, the clearance gap which bites the bubble by peeling arises between a 2nd release film and an adhesion layer at the process of peeling a 1st release film.

  In the first 'substrate-less double-sided pressure-sensitive adhesive sheet precursor 41' of the present invention, the No. of the first 'release film 32' on the light release side is shown. The 180 ° peeling force in a 502 tape, 300 mm / min speed region is usually 10 to 20 mN / cm, preferably 12 to 18 mN / cm. When the peeling force of the first 'release film 31' is less than 10 mN / cm, the peeling force is low, and thus problems such as peeling off without permission occur. In addition, when the peeling force of the first 'release film 31' exceeds 20 mN / cm, the first 'release film 32' is peeled off from the adhesive when the optical substrate sheet 10 is produced. 1 The difference in peeling force from the release film 32 is small, causing a problem that peeling is not possible.

  In the first'substrate-less double-sided PSA sheet precursor 41 'of the present invention, the first release film 32 and the first'release film 32'No. The ratio of 180 ° peeling force in the 502 tape, 300 mm / min speed region is preferably 2.0 times or more on the heavy peeling side / light peeling side. When it is smaller than 2.0 times, the peeling abnormality as described above occurs.

  In the pressure-sensitive adhesive sheet 10 for an optical substrate of the present invention, the second substrate-less double-sided pressure-sensitive adhesive sheet 42 having the second release film 33 which is a heavy release sheet, that is, the second substrate-less double-sided pressure-sensitive adhesive sheet precursor 42 ′. The release force of the second release film 33 is that a double-sided adhesive tape (“No. 502” manufactured by Nitto Denko) is attached to the release layer surface and left at room temperature for 1 hour, and then the substrate film and release angle are 180 °. The value measured with a tensile tester when the tape was peeled off at an arbitrary tensile speed. The method for adjusting the specific peeling force in the present invention can be achieved by selecting the composition in the release layer, but other means can also be adopted, mainly the type of release agent for the silicone release layer. Is preferably changed according to the desired peeling force, and furthermore, since the peeling force largely depends on the application amount of the release agent to be used, a method of adjusting the application amount of the release agent is more preferable.

  In the present invention, No. 2 of the second release film 33 of the second substrate-less double-sided PSA sheet precursor 42 ′. The peel force for 502 is 300 mm / min, preferably 20 to 100 mN / cm, and more preferably 40 to 80 mN / cm. If the peeling force of the second release film is less than 20 mN / cm, the peeling force of the second 'release film 33' must be lowered to the limit. In this case, the second 'release film 33' is arbitrarily used. In the process of producing the pressure-sensitive adhesive sheet 10 for an optical substrate and bonding it to another substrate, there is a problem that a difference in peeling force with the first release film 32 is small and a peeling abnormality is caused. Arise. Moreover, when the peeling force of the 2nd mold release film 33 exceeds 100 mN / cm, the process of bonding to a polyester film, the optical substrate sheet 10 is prepared, and the process of bonding to another member is When the release film 33 is peeled off, problems such as cohesive failure of the pressure-sensitive adhesive occur because the peeling force is too heavy.

  In the 2 'substrate-less double-sided pressure-sensitive adhesive sheet precursor 42' of the present invention, the No. of the second 'release film 32' on the light release side is shown. The 180 ° peeling force in a 502 tape, 300 mm / min speed range is usually 20 to 40 mN / cm, preferably 25 to 35 mN / cm. When the peeling force of the second 'release film 33' exceeds 40 mN / cm, the peeling force of the second release film 33 is increased, so when the optical base sheet 10 is bonded to another member Furthermore, when peeling the 2nd release film 33 from an adhesive, the malfunction which raise | generates peeling abnormalities, such as causing the cohesive failure of an adhesive and a film not peeling from an adhesive, arises.

  In the 2 'substrate-less double-sided pressure-sensitive adhesive sheet precursor 42' of the present invention, the No. of the second release film 33 and the second 'release film 33'. The ratio of 180 ° peeling force in the 502 tape, 300 mm / min speed region is preferably 2.0 times or more on the heavy peeling side / light peeling side. When it is smaller than 2.0 times, the peeling abnormality as described above occurs.

  In the pressure-sensitive adhesive sheet for optical substrates of the present invention, the peeling force of the second release film 33 provided on the second substrate-less double-sided pressure-sensitive adhesive sheet precursor 42 and the first substrate-less double-sided pressure-sensitive adhesive sheet precursor 41 are provided. No. of the second release film 32 formed. The ratio of 180 ° peeling force in the 502 tape, 300 mm / min speed region is preferably 2.0 times or more on the heavy peeling side / light peeling side. When it is smaller than 2.0 times, the release film cannot be peeled off well when bonded to another member.

  The polyester film for the film substrate core referred to in the present invention is a film that is melt-extruded from an extrusion die, is a film that has been stretched and heat-treated as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method. is there.

  The polyester constituting the film for the film substrate core of the present invention is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. The polyester used may be a homopolyester or a copolyester. In the case of a copolyester, it may be a copolymer containing 30 mol% or less of the third component.

  The dicarboxylic acid component of the copolymerized polyester is selected from isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  The polyester for the film substrate used in the present invention includes a weather resistance agent, a light resistance agent, an antistatic agent, a lubricant, a light-shielding agent, an antioxidant, a fluorescent whitening agent, a mat as long as the gist of the present invention is not impaired. Coloring agents such as an agent, a heat stabilizer, a dye or a pigment may be added.

  Examples of the particles to be blended in the film base include silicon oxide, alumina, calcium carbonate, kaolin, titanium oxide, and crosslinked polymer fine powder as described in JP-B-59-5216. These particles may be used alone or in combination of two or more components. The blending amount of these particles is usually 1% by weight or less, preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the film. When the content of the particles is small, the film surface cannot be appropriately roughened, and in the film production process, there is a tendency that the surface is easily scratched or the winding properties are inferior. On the other hand, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large and the transparency is impaired.

  The average particle size of the particles contained in the film substrate is usually 0.02 to 5 μm, preferably 0.1 to 3 μm, more preferably 0.2 to 1.8 μm. When the particle size is less than 00.2 μm, the film surface cannot be made an appropriate rough surface, and the winding characteristics in the film production process are inferior. When the particle diameter exceeds 5 μm, when used as a polarizing plate release film, it becomes a bright spot and hinders foreign matter inspection.

  On the other hand, in order to improve the transparency of the film, when a laminated film of two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers. The blending amount of the particles in the case of such a laminated film is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.6% by weight, based on the polyester constituting the surface layer.

  The particle size distribution of the particles used is preferably sharp. Specifically, those having a particle size distribution value of 1.0 to 2.0, which is an index representing the sharpness of the particle size distribution, are preferable. Here, the particle size distribution value is the particle size distribution value d25 / d75 (d25 and d75 are calculated by calculating the accumulated accumulation of the particle group from the large particle side, and the particle size corresponding to 25% and 75% of the total volume (μm Is a value defined by When the particle size distribution value exceeds 2.0, coarse particles become bright spots, which similarly impairs foreign matter inspection.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  The polyester to be used may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dl / g or more, and more preferably 0.40 to 0.90 dl / g.

  In the present invention, it may be a film having a structure obtained by coextrusion laminating a polyester having a low oligomer content on the surface of at least one side of a layer composed of a polyester having a normal oligomer content. In the polyester film for release film obtained in the present invention, the effect of preventing bright spots due to the precipitated oligomer is obtained, which is particularly preferable.

  The thickness of the film substrate core 11 of the present invention is usually in the range of 12 to 75 μm. If the total film thickness is less than 12 μm, wrinkles will occur when bonded to the baseless adhesive sheet, and there will be problems such as inability to maintain stiffness, or the effect of preventing scattering when using glass will be impaired. Problems can arise. On the other hand, when it is thicker than 75 μm, when it is used as a member near the surface of the touch panel, the writing effect due to the cushioning effect of the pressure-sensitive adhesive is reduced, and the transparency as the pressure-sensitive adhesive sheet for optical use is impaired.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  First, the preferable example of the manufacturing method of polyester used by this invention is demonstrated. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used. According to a conventional method, esterification from terephthalic acid and ethylene glycol, or transesterification reaction between dimethyl terephthalate and ethylene glycol, the product is transferred to a polymerization tank, the temperature is increased while reducing pressure, and finally vacuum is applied. Under heating to 280 ° C., the polymerization reaction proceeds to obtain a polyester.

  Next, for example, the polyester chip obtained as described above and dried by a known method is supplied to a melt-extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is stretched biaxially to form a film.

  Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. Furthermore, it is also possible to perform simultaneous biaxial stretching of the unstretched sheet so that the area magnification is 10 to 40 times.

  If the film base material of this invention is a range which does not impair the effect of this invention, what is called an in-line coating which processes a film surface during an extending process can also be given. Although it is not limited to the following, for example, after the first stage of stretching is completed, before the second stage of stretching, improvement of antistatic property, slipperiness, adhesion, etc., secondary workability improvement, weather resistance, etc. In order to improve the property and surface hardness, a coating treatment with an aqueous solution, an aqueous emulsion, an aqueous slurry, or the like can be performed. Various coatings may be performed by offline coating after film production. Such a coat may be either single-sided or double-sided. The coating material may be either water-based and / or solvent-based for off-line coating, but is preferably water-based for in-line coating.

  The haze of the film substrate core 11 of the present invention is usually 7% or less, preferably 5% or less, more preferably 3 to 4%. In the pressure-sensitive adhesive sheet for an optical substrate, a haze as low as possible is good for improving visibility. If the film haze exceeds 7%, the field of view will become cloudy during transmitted light inspection, which will hinder the inspection, and the product will have poor visibility when manufactured. However, if it is 3% or less, the surface roughness of the film is low, scratches are likely to occur during film formation, and winding properties are inferior.

  Moreover, the surface roughness (Ra) of a film is 18-33 nm normally. When the film Ra exceeds 33 nm, the planarity of the surface is impaired, and the film becomes whitish, which may hinder the inspection. On the contrary, when Ra of the film is less than 18 nm, the film surface becomes extremely flat, and the winding characteristics in the film manufacturing process are inferior.

  In order to achieve the haze and roughness in the present invention, it is necessary to appropriately select the type, content and size of the particles.

  The release film used for the film substrate core and the substrate-less double-sided pressure-sensitive adhesive sheet in the present invention, in particular, on the heavy release side, the variation of the orientation angle in the measurement method described in the examples in the film is 8 degrees. / 40 mm or less, more preferably 6 degrees / 40 mm or less. When the variation in the orientation angle exceeds 8 degrees / 40 mm, it becomes an obstacle to stable inspection of the in-line polarization inspection camera in the process used when inspecting foreign matters and the like.

  The polyester film in the present invention preferably has a refractive index (nβ) in the direction perpendicular to the film in-plane direction of 1.6400 or less with respect to the main orientation axis. There is a tendency to increase the fluctuation of the angle, which not only becomes an obstacle to stable inspection of the polarizing plate, but also the formation of voids in the particles becomes prominent and easily visible as a bright spot during the inspection of the polarizing plate. Become.

  In order to achieve the above-described orientational elements in the present invention, it is necessary to appropriately adjust the stretching conditions, that is, the stretching ratio, the stretching temperature, and the like.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layers 13 and 23, an acrylic pressure-sensitive adhesive is usually used. The acrylic pressure-sensitive adhesive is composed mainly of an acrylic copolymer obtained by copolymerizing a functional group-containing monomer and another monomer such as an acrylic ester or methacrylic ester, and if necessary, a solvent , A crosslinking agent, a tackifier, a filler, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber and the like may be further contained.

  Examples of the functional group-containing monomer include carboxyl group-containing monomers such as acrylic acid and methacrylic acid. The functional group-containing monomer preferably includes 0.3 to 5.0% by mass as a monomer unit based on the whole monomer constituting the acrylic copolymer (100% by mass).

  By containing functional groups, acrylic copolymers can adjust the cohesive force by reaction with the crosslinking agent, and prevent the adhesive from sticking out from the base material and improve the adhesive strength and heat resistance. Can be made. There is no restriction | limiting in particular as a crosslinking agent used for an adhesive, It uses suitably selecting from what was conventionally used in the acrylic adhesive conventionally, for example, a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin , Dialdehydes, methylol polymers, aziridine compounds, metal chelate compounds, metal alkoxides, metal salts and the like, preferably polyisocyanate compounds are used.

  When processed into the pressure-sensitive adhesive sheet 10 for an optical substrate in the present invention, there is an operation of bonding to another member, but in order to distinguish a release film having a transparent light release and heavy release capability at that time, by laser irradiation Coloring is used as one method. Coloring in the present invention is a color change in the film appearance. Specifically, it can be expressed by the contrast ratio in the luminance measurement. Specifically, the relative luminance obtained from the ratio of the laser irradiated part to the unirradiated part is about 102 to 200, preferably 200 or more. Further, coloring can also be expressed by ΔE obtained from L * a * b * color difference evaluation, and the ΔE value is preferably about 0.5 to 6.0, more preferably 6.0 or more. is there.

  In the present invention, in order to achieve the above-mentioned value, a laser marking compound that is stable on film formation is appropriately selected, and the content is set so as not to cause haze reduction, poor color appearance, and sufficient coloring performance. Must be adjusted.

In carrying out the present invention, the laser light source and the irradiation method thereof are not particularly limited, and various known Nd: YAG lasers, CO ₂ lasers, various excimer lasers, and the like can be used. Among these, the effect becomes remarkable in the marking using the Nd: YAG laser.

  In the present invention, the strength of coloring by laser irradiation used for distinguishing a release film having light release and heavy release ability is that only an appropriate part can be colored at an appropriate timing and place. In addition, when a film with light release and heavy release ability has the same transparency and the same thickness, it is also epoch-making that it can be easily distinguished after laser irradiation by including a laser marking pigment in either of them. It is.

  In the pressure-sensitive adhesive sheet 10 for an optical substrate according to the present invention, the transparency means that the first release film 31 is peeled off and bonded to a 1 mm thick float glass, and further, the second release film 32 on the opposite surface is peeled off. The transparency value of the pressure-sensitive adhesive sheet for an optical substrate itself, which is obtained by subtracting the transparency value of the float plate glass from the transparency value measured when pasted on a 1 mm thick float plate glass. The transparency is 70% or more, preferably 72% or more, more preferably 74% or more. When the transparency is lower than 70%, the visibility of the final product is lowered, which is not preferable.

  In the present invention, the image clarity value of the film in the measurement method to be described later is determined by peeling the first release film 31 from the pressure-sensitive adhesive sheet 10 for an optical substrate and bonding it to a 1 mm-thick float plate glass. 2. The image clarity of the pressure-sensitive adhesive sheet for an optical substrate itself is obtained by subtracting the image clarity value of the float plate glass from the image clarity value measured when the release film 32 is peeled off and attached to a 1 mm thick float plate glass. Value. The image clarity value is 85% or more, preferably 90% or more. When the image clarity value of the film is less than 85%, when used as a polarizing film, the visibility is deteriorated, and when there is a defect inspection by transmitted light, the image is distorted, for visual inspection or automatic inspection. Problems such as troubles occur.

  In order to make the transparency and image clarity value of the above-mentioned pressure-sensitive adhesive sheet for optical substrates within the above-mentioned range, it is possible to cause phenomenon of pressure-sensitive adhesive particles and aggregates by filtering, but the device of the film substrate also has a great influence. . For example, it can be achieved by appropriately combining various conditions such as the kind of particles used for the film substrate, the particle diameter, the amount added, and the film production conditions (film stretching temperature, stretching ratio). In particular, the appropriate selection of the particle type can greatly reduce the voids caused by the particles in the film and suppress light scattering, thereby greatly contributing to achieving the transparency and image clarity required for the product. Moreover, the graininess at the time of seeing visually can be eliminated by not making a void. The void in the present invention refers to a gap that can be caused by the particles not being able to follow the inside of the film during film stretching.

  The technical advantage of the present invention is that when the optical pressure-sensitive adhesive sheet is bonded to a member, it can be visually observed without graininess. When there is a grainy feeling, the pattern of the particles appears as a bright spot, and the appearance of grains causes a problem of feeling stress when watching the video. The means for eliminating the graininess is required to improve the transparency and the image clarity value of the whole member as described above. In addition, the haze of the film substrate core between the adhesives is also reduced. It becomes an important factor. Even if transparency and image clarity are high, it can be used as a product, but if the film substrate core has a low haze, the final product will have a clear contrast ratio of light, giving a clear image. Things can be done and even better. Means for realizing the transparency, image clarity value, and haze reduction are various conditions such as the above-mentioned film base core particle type, particle size, addition amount, film production conditions (film stretching temperature, stretching ratio), etc. Ingenuity is necessary.

  Another technical advantage of the present invention is that when the surface layer of the film substrate core is provided with a layer having an OL sealing effect, it is possible to achieve suppression of foreign matters due to the film to the limit.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. It was dissolved and measured at 30 ° C.

(2) Measurement of average particle size (d50: μm) 50% integrated (weight basis) in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) The value was defined as the average particle size.

(3) Film haze According to JIS-K6714, the turbidity of the film was measured with the Nippon Denshoku Industries Co., Ltd. divisional turbidimeter NDH-20D.

(4) Measurement of amount of catalyst in coating layer Using SAICAS, the sample film was obliquely cut to expose the cross section. Then, the amount of catalyst containing platinum contained in the polyester film coating layer was determined using TOF-SIMS (time-of-flight mass spectrometry mass spectrum).

(5) Measurement of amount of migration component in release layer composition 0.02 wt% of platinum catalyst was added to 15 g of silicone resin (silicone of release layer composition) diluted with toluene to a solid content concentration of 4 wt%. After stirring, the mixture is placed in a box made of a sheet made of Teflon (registered trademark) and thermally cured at 150 ° C. for 1 hour (Sample 1). When adding a migration component (corresponding to Comparative Example 2 described later), 30% by weight is added to the solid content of the silicone resin. Sample 1 is immersed in toluene for 1 day, and the sample taken out is dried at 120 ° C. for 30 minutes and allowed to cool to room temperature (sample 2). The migration component amount was calculated from the following formula.
Migration component amount (% by weight) = (weight of sample 1−weight of sample 2) ÷ weight of sample 1 × 100

(6) No. of release film. Evaluation of peeling force with 502 tape After applying one side of double-sided adhesive tape (“No. 502” and “No. 31B” manufactured by Nitto Denko) to the surface of the release layer of the sample film, the size is 50 mm × 300 mm. After cutting, the peel strength after standing for 1 hour at room temperature is measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under the condition of a tensile speed of 300 mm / min. Judgment is based on the following criteria.

(7) Measurement of OL extracted from film coating layer surface An unheat-treated release film is heated in air at 180 ° C. for 10 minutes in advance. After that, the heat-treated film is brought into close contact with the inner surface of a box having a top and width of 10 cm and a height of 3 cm, and the box shape is obtained. When the coating layer is provided, the coating layer surface is set to the inside. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of OL in DMF, and this value was divided by the area of the film in contact with DMF to obtain the amount of film surface OL (mg / M ² ).

  The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing OL (cyclic trimer) collected in advance and dissolving it in DMF accurately weighed. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml. The conditions for the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(8) Measurement of OL extracted from product In advance, the first release film 32 of the first base material-less double-sided pressure-sensitive adhesive sheet layer 41 is peeled off, and a 2 cm × 5 cm × 1 mm thick float plate glass (manufactured by Sekiya Rika Co., Ltd.) In addition, the second release film 33 was peeled off, and was similarly attached to a 1 mm-thick float plate glass to prepare a sample. The prepared sample is heated in air at 180 ° C. for 10 minutes. Thereafter, the float plate glass is removed, and the heat-treated sample is brought into close contact with the inner surface of a box having a top and width of 10 cm and a height of 3 cm as much as possible to form a box shape. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then the adhesive is removed with tweezers to recover the DMF remaining on the film side. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of OL in DMF, and this value was divided by the film area in contact with DMF to obtain the amount of sample surface OL (mg / M ² ). The calculation of the amount of oligomer is the same as the above-mentioned “Measurement of OL extracted from the film coating layer surface”.

(9) Measurement of surface roughness (Ra) of film substrate core Using a surface roughness measuring machine SE3500 manufactured by Kosaka Laboratory Ltd., measurement was performed according to JIS B0601-1994. The measurement length was 2.5 mm.

(10) Measurement of haze of film substrate core According to JIS-K7105, the haze of the film was measured with an integrating sphere turbidimeter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.

(11) Measurement of image clarity value of pressure-sensitive adhesive sheet for optical substrate The first release film 32 of the first substrate-less double-sided pressure-sensitive adhesive sheet layer 41 is peeled off, and a 2 cm × 5 cm × 1 mm thick float plate glass (Sekiya Rika Co., Ltd.) In addition, the second release film 33 was peeled off, and similarly attached to a 1 mm thick float plate glass to prepare a sample. The produced samples were measured for the image clarity value of the film by the transmission method with a image clarity measuring device ICM-1 manufactured by Suga Test Instruments Co., Ltd. according to JIS-K7105. The value is read from an optical comb of 0.125 mm. At this time, the image clarity value of the pressure-sensitive adhesive sheet for an optical substrate was determined by the following formula using the image clarity value of the float plate glass measured in advance.
Image clarity value (%) = {(image clarity value of prepared sample (%)) − (image clarity value of float plate glass (%)) × 2}
Judgment is based on the following criteria.
○: 85% or more ×: lower than 85%

(12) Measurement of transparency of pressure-sensitive adhesive sheet for optical substrate The first release film 32 of the first substrate-less double-sided pressure-sensitive adhesive sheet layer 41 is peeled off, and a 2 cm × 5 cm × 1 mm-thick float plate glass (manufactured by Sekiya Rika Co., Ltd.) In addition, the second release film 33 was peeled off and similarly laminated on a 1 mm thick float plate glass to prepare a sample. The transparency of the prepared sample was measured using a transparency measuring instrument (TM-1D two decimal places: light source wavelength 546 ± 5 nm) manufactured by Murakami Color Research Laboratory. At this time, the transparency of the pressure-sensitive adhesive sheet for an optical substrate was obtained by the following formula using the transparency of the float plate glass measured in advance.
Transparency (%) = {(Transparency (%) of prepared sample) − (Transparency (%) of float plate glass) × 2}
Judgment is based on the following criteria.
○: 70% or more ×: Lower than 70%

(13) Evaluation of polyester film after laser irradiation The laser marking conditions are as follows.
Laser marking device: Keyence Co., Ltd. laser marker MD-V9900
Laser type: YVO ₄ laser (wavelength 1064 nm)
Irradiation method: XYZ 3-axis simultaneous scanning method (CW (continuous oscillation), Q switch frequency 1 to 400 kHz)
Marking power: 13W
Scanning speed: 1500mm / s

-Contrast evaluation of the coloring intensity after laser irradiation of the polyester film Using a luminance meter, the contrast ratio between the uncolored portion of the film before laser irradiation and the colored portion after laser irradiation was evaluated. Specifically, a sample is placed on a flat illuminator manufactured by Dentsu Sangyo Co., Ltd .: HF-SL-A48LCF, and further, using Konica Minolta Sensing Co., Ltd. CS-200, the measurement viewing angle is 1 °, and the distance between the sample and the luminance meter is measured. The luminance value (cd / m ² ) was measured at 500 mm. The relative luminance (%) was obtained from the following formula.
Relative luminance = (measured value of the laser non-irradiated portion) ÷ (measured value of the laser irradiated portion) × 100 Evaluation was made according to the following criteria from the obtained relative luminance value.
○: Over 200 (strong coloring).
Δ: 102 to 200 (colored).
X: Less than 102 (almost not colored).

・ L * a * b * Color Difference Evaluation of Coloring Strength after Laser Irradiation of Polyester Film About the obtained polyester film after laser irradiation, using a color difference meter, uncolored portions of the film before laser irradiation and after laser irradiation The L * a * b * color difference of the colored portion was evaluated. Specifically, according to JIS Z 8729, L * a * b * color difference values of the laser irradiated portion and the non-irradiated portion were measured using a color difference meter CR-410 (sample diameter 50 mm) manufactured by Konica Minolta. At this time, the light source was C / D65, the back surface was white, and measurement was performed by a reflection method. The measurement was performed three times, and an average value was adopted. ΔL * (irradiated portion L * value−non-irradiated portion L * value), Δa * (irradiated portion a * value−non-irradiated portion a * value), Δb * (irradiated portion b * value−non-irradiated portion) (Part b * value) was calculated, and ΔE value was calculated and evaluated.
The ΔE value was determined from the following formula.
ΔE = {(ΔL *) ² + (Δa *) ² + (Δb *) ² } ^1/2
Evaluation was performed based on the following criteria from the obtained ΔE value.
○: More than 6.0 (strong coloring).
Δ: 0.5 to 6.0 (colored).
X: Less than 0.5 (almost not colored).

(14) Practical properties <Releasability 1 of release film of base material-less double-sided PSA sheet and optical base PSA sheet> The ratio of peel force with 502 tape was compared and evaluated.
○: 2.0 times or more: No abnormality is observed at the interface between the second release layer and the adhesive, or the release film floats at the interface between the second release layer and the adhesive, and the adhesive has a pattern. Occurred but practically acceptable level Δ: 1.2 to 2.0 times: level at which no abnormality is observed at the interface between the second release layer and the pressure-sensitive adhesive, but slightly caught ×: smaller than 1.2 times: When the release film floats at the interface between the second release layer and the pressure-sensitive adhesive, a clear pattern is generated on the pressure-sensitive adhesive.

<Releasability 2 of Release Film of Substrate-less Double-Sided Adhesive Sheet and Optical Adhesive Sheet for Optical Substrate> At the stage of forming a sheet, the adhesive and the release film were peeled and evaluated.
○: Neither catching nor zipping occurs, and the surface shape is clean ×: Striking or zipping occurs, the surface shape becomes rough, or cohesive failure occurs

<Occurrence of zipping at the time of peeling of the release film of the double-sided pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet for optical substrates>
When measuring the peeling force, the peeling state of the pressure-sensitive adhesive and the release film was observed, and the occurrence of zipping was evaluated in three stages.
○: Peeling extremely smoothly, no peeling stripes, no peeling noise △: Slight peeling stripes are observed, peeling noise is slightly generated, and slight zipping occurs ×: Peeling stripes are observed , Peeling sound is generated, zipping is generated, and △ is a level where there is no problem in practical use.

(15) Comprehensive evaluation An evaluation is performed taking all of film forming properties, workability, functionality, etc. into consideration. Judgment is based on the following criteria.
○: Even if it is produced, it can be supplied as a product. Visual transmission, no graininess, good visibility Δ: Productivity is good, and the frequency of defects in optical inspection is low. Visual transmission, no graininess, good visibility. X: Productivity is poor, and defects in optical inspection frequently occur. Visually transparent, grainy and lack of visibility

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (a)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed for 4 hours.
That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.61 due to a change in the stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (a) having an intrinsic viscosity of 0.61.

<Method for producing polyester (b)>
In the method for producing polyester (a), after adding ethyl acid phosphate, an ethylene glycol slurry of synthetic calcium carbonate particles having an average particle diameter of 0.8 μm was added so that the content of the particles with respect to polyester was 1% by weight. Obtained polyester (b) using the method similar to the manufacturing method of polyester (a). The obtained polyester (b) had an intrinsic viscosity of 0.60.

<Production of polyester (c)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.45 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (c). The intrinsic viscosity of this polyester was 0.45.

<Manufacture of polyester (d)>
The intrinsic viscosity of this polyester chip was increased by a solid phase polycondensation method. After treatment in a preliminary crystallization tank at 170 ° C. in a nitrogen atmosphere for 0.5 hours, the moisture content becomes 0.005% at a temperature of 200 ° C. using a tower dryer that flows an inert gas. Until dried. Thereafter, it was sent to a solid phase polymerization tank and subjected to solid phase polymerization at 240 ° C. for 3 hours to obtain a polyester (d) having an intrinsic viscosity of 0.70.

<Manufacture of polyester (e)>
When producing the polyester (d), solid phase polymerization was performed in a solid phase polymerization tank for 5 hours to obtain a polyester (e) having an intrinsic viscosity of 0.80.

Example 1:
<Manufacture of release film 32, 32 ', 33'substrate>
As a raw material for the surface layer, 70% by weight of polyester (e) and 30% by weight of polyester (b) are mixed. As a raw material for the intermediate layer, 84% by weight of polyester (a) and 16% by weight of polyester (b) are mixed. Each was supplied to an extruder with a vent and melt-extruded at 290 ° C., and then cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., and then the following coating agent was applied to one side of the longitudinally stretched film so that the coating amount (after drying) was 0.03 g / m ² . Then, after guiding to the tenter, through the preheating process in the tenter, 5.1 times transverse stretching was performed at 120 ° C, followed by heat treatment at 220 ° C for 10 seconds, and then 4% relaxation at 180 ° C in the width direction. Was added to obtain a master roll having a width of 4000 mm. A slit was made from a position of 1400 mm from the end of the master roll, and the core roll was wound up 1000 m to obtain a polyester film. The total thickness of the obtained film was 50 μm (layer structure: surface layer 2.5 μm / intermediate layer 45 μm / surface layer 2.5 μm). However, in the case of the present invention, only when a coating layer (corresponding to 15, 15 ', 25, 25' in the figure) for OL sealing ability is provided, coating processing is performed after stretching in the longitudinal direction as necessary. It is assumed that stretching in the transverse direction is performed.

<Coating layer>
Examples of compounds constituting the coating layers 15, 15 ′, 25, 25 ′ are as follows.
(Example compounds)
-Polyvinyl alcohol binder polymer having a saponification degree of 88 mol% and a polymerization degree of 350: A
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant) Binder polymer: B
・ Crosslinking agent Hexamethoxymelamine crosslinking agent: C
・ Particulate colloidal silica (average particle diameter: 70 nm): D
Solid content ratio: A / B / C / D = 30/24/42/4

<Manufacture of release film 33 substrate>
Composite material of copper and molybdenum (CuO · xMoO ₃ : Dongguan Material Technology Co., Ltd.) which is a raw material in which 70% by weight of polyester (e) and 30% by weight of polyester (b) are mixed as raw material for the surface layer and laser marking pigment. ) Was mixed at a ratio of 99.96: 0.04 as the intermediate layer raw material, and the surface layer polyester B and the intermediate layer mixed raw material were respectively supplied to the two extruders at a ratio of 1: 9. Each was melted at 290 ° C., and then co-extruded in a layer structure of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set at 40 ° C., and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 2.8 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then the coating amount described above was applied to one side of the longitudinally stretched film. .03g was coated so as to / m ^2, then, introduced into a tenter, subjected to 5.1 times the transverse stretching at 120 ° C. through a preheating step in a tenter, subjected to heat setting at 225 ° C., the horizontal The film was relaxed 2% in the direction to obtain a transparent polyester film having a thickness of 50 μm (surface layer 2.5 μm, intermediate layer 45 μm). The obtained polyester film was a colorless and transparent film.

  In the release films 32, 32 ', 33, and 33', the stretching prescription and the thickness of the film were variously changed (see Table 2).

<Manufacture of release films 32, 32 ', 33, 33'>
A reverse gravure coating method in which the release agent shown below is applied to the obtained release films 32, 32 ', 33, and 33' in a polyester film so that the coating amount (after drying) is 0.1 g / m ^2. Then, a roll-like release polyester film was obtained under the conditions of a dryer temperature of 120 ° C. and a line speed of 30 m / min (see Table 2).

<Release layer>
A biaxially oriented polyester film obtained by the production of a polyester film is provided with a paint having a release layer composition shown below so that the coating amount is 0.1 g / m ² (after drying). Obtained (see Table 2).

-Release layer composition-1
Curable silicone resin (LTC303E: manufactured by Toray Dow Corning) 20 parts Addition type platinum catalyst (SRX212: manufactured by Toray Dow Corning) 0.2 parts MEK / toluene / n-heptane mixed solvent (mixing ratio is 1: 1: 1) )
Migrating amount of release agent composition-1: 15% by weight

・ Releasing layer composition-2
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 17 parts Peeling control agent (KS-3800: manufactured by Shin-Etsu Chemical Co., Ltd.) 3 parts Addition type platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 parts MEK / toluene / N-heptane mixed solvent (mixing ratio is 1: 1: 1)

・ Release layer composition-3
Curable silicone resin (X-62-5039: manufactured by Shin-Etsu Chemical Co., Ltd.) 14 parts Peeling control agent (KS-3800: manufactured by Shin-Etsu Chemical Co., Ltd.) 6 parts Cross-linking agent (X-92-185: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4 Part catalyst (PL-5000: manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part MEK / toluene / n-heptane mixed solvent (mixing ratio is 1: 1: 1)

-Release layer composition-4
Curable silicone resin (X-62-5039: manufactured by Shin-Etsu Chemical Co., Ltd.) 12 parts Peeling control agent (KS-3800: manufactured by Shin-Etsu Chemical Co., Ltd.) 8 parts Cross-linking agent (X-92-185: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4 Part catalyst (PL-5000: manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part MEK / toluene / n-heptane mixed solvent (mixing ratio is 1: 1: 1)

<Manufacture of polyester (f)>
Starting from 100% by weight of dimethyl terephthalate and 60% by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.64 dL / g due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (f). The intrinsic viscosity of this polyester was 0.64 dL / g.

<Manufacture of polyester (g)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, and 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C.
On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.45 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (g). The intrinsic viscosity of this polyester was 0.45.

<Manufacture of polyester (h)>
The intrinsic viscosity of this polyester chip was increased by a solid phase polycondensation method. After treatment in a preliminary crystallization tank at 170 ° C. in a nitrogen atmosphere for 0.5 hours, the moisture content becomes 0.005% at a temperature of 200 ° C. using a tower dryer that flows an inert gas. Until dried. Thereafter, it was sent to a solid phase polymerization tank and subjected to solid phase polymerization at 240 ° C. for 3 hours to obtain a polyester (h) having an intrinsic viscosity of 0.70.

<Manufacture of polyester (i)>
When producing the polyester (h), solid phase polymerization was performed in a solid phase polymerization tank for 5 hours to obtain a polyester (i) having an intrinsic viscosity of 0.80.

<Manufacture of polyester (j)>
In the method for producing polyester (f), after adding ethyl acid phosphate, the content of ethylene glycol slurry of divinylbenzene / styrene copolymer crosslinked particles having an average particle size of 1.0 μm is 0.6% by weight with respect to polyester. A polyester (j) was obtained using the same method as the method for producing the polyester (f) except that it was added as described above. The obtained polyester (j) had an intrinsic viscosity of 0.63.

(Manufacture of polyester (k))
In the method for producing polyester (j), after adding ethyl acid phosphate, the content of ethylene glycol slurry of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 1.4 μm is 0.5% by weight with respect to polyester. The polyester (k) was obtained using the same method as the production method of the polyester (j) except that the addition was made so as to be%. The obtained polyester (k) had an intrinsic viscosity of 0.62 dL / g.

(Production of polyester (l))
In the method for producing polyester (k), the additive particles are synthetic calcium carbonate particles having an average particle diameter of 1.0 μm, and the content with respect to the polyester is 2.0% by weight. A polyester (l) was obtained using the same method. The obtained polyester (l) had an intrinsic viscosity of 0.63.
Met.

<Manufacture of film base 31>
A mixed raw material obtained by mixing the polyester (f), (i) chip and the polyester (j), (k), (l) chip at a ratio as shown in Tables 1 and 2 below is used as an outermost layer (surface layer) and The raw material for the intermediate layer is supplied to two extruders, melt-extruded at 280 ° C., and then cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A sheet was obtained. Next, after stretching 2.8 times in the longitudinal direction at 100 ° C., the following coating agent was applied on both sides of the longitudinally stretched film so that the coating amount (after drying) was 0.03 g / m ² , After guiding to the tenter and performing a transverse stretching of 5.1 times at 120 ° C. through a preheating step in the tenter, heat treatment at 220 ° C. for 10 seconds, and then adding 4% relaxation in the width direction at 180 ° C., A master roll having a width of 4000 mm was obtained. A slit was made from a position of 1400 mm from the end of the master roll, and the core roll was wound up 1000 m to obtain a polyester film. The total thickness of the obtained film was 38 μm (surface layer 3 μm / intermediate layer 32 μm / surface layer 3 μm).

<Coating layer>
Examples of the compounds constituting the coating layers 12 and 12 ′ are as follows.
(Example compounds)
-Polyvinyl alcohol binder polymer having a saponification degree of 88 mol% and a polymerization degree of 350: A
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant) Binder polymer: B
・ Crosslinking agent Hexamethoxymelamine crosslinking agent: C
・ Particulate colloidal silica (average particle diameter: 70 nm): D
Solid content ratio: A / B / C / D = 30/24/42/4

<Manufacture of substrate-less double-sided PSA sheet precursor>
On the release agent layer of the obtained 1 ′ release film, the acrylic pressure-sensitive adhesive solution was coated using an applicator so that the film thickness after drying was 25 μm, and then the coating film Was dried at 120 ° C. for 1 minute to form an adhesive layer. The acrylic pressure-sensitive adhesive solution was prepared by adding polyisocyanate-based crosslinking to 100 parts by mass of a copolymer solution (solvent: toluene, solid content concentration: 40% by mass) having a monomer-based mass ratio of butyl acrylate and acrylic acid of 99: 1. It was obtained by adding 1 part by weight of an agent (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BHS8515”, solid content concentration 37.5% by mass). Subsequently, the release agent layer and adhesive layer of the 1st release film were bonded together, and the base material-less double-sided adhesive sheet precursor of Example 1 was obtained (refer Table 2).

<Manufacture of pressure-sensitive adhesive sheet for optical substrate>
The first 'release film 32', which is a light release sheet of the obtained first substrate-less double-sided PSA sheet precursor 41 ', was peeled off, and the exposed adhesive layer and one side of the film substrate were bonded together. Next, the second release film 33 ′, which is a light release sheet of the second substrate-less double-sided pressure-sensitive adhesive sheet precursor 42 ′, was peeled off, and the exposed adhesive layer and the above prepared (first substrate-less double-sided pressure-sensitive adhesive sheet 32). / The other side of the film substrate core 31 (of the polyester film 31) was bonded to obtain the target pressure-sensitive adhesive sheet 10 for an optical substrate. About the obtained adhesive sheet for optical base materials, YVO ₄ laser (Keyence Corporation: MD-V9900) light irradiation (1064 nm) was performed and the coloring performance was evaluated. Only the second release film was changed to a gray colored state. Was good. The obtained film had a relative luminance of 210% and ΔE of 5.73 (L * = 82.81, a * = 1.86, b * = 2.04). The obtained results are shown in Table 2.

When the release films 32 and 33 of the obtained pressure-sensitive adhesive sheet 10 for an optical substrate are peeled and bonded to glass having a thickness of 1 mm, the image clarity of the pressure-sensitive adhesive sheet is 90.2%, and the transparency is 74.5%. (Table 2).

Examples 2-4:
In the first, 1 ', 2, 2' release film of Example 1, change the presence or absence of a coating film at the time of production of the polyester film, and change the silicone composition when processing the silicone layer on the polyester film. A polyester film was obtained in the same manner as in Example 1 except that the coat thickness was changed. Moreover, in the 2nd mold release film, it manufactured like Example 1 except changing content of a laser marking compound, and obtained the polyester film. Subsequently, in the film base core 31 of Example 1, it manufactured like Example 1 except changing the polyester seed | species, the compounding quantity of polyester, and a layer structure, and obtained the polyester film. Finally, the obtained member was bonded to obtain a target optical pressure-sensitive adhesive sheet. The characteristic results of the obtained sheet are summarized in Table 2 below.

(* 1) There is no problem in terms of performance, but haze is low, the film is not rough, scratches enter the entire surface, and productivity is lowered.
(* 2) If a coating layer containing polyvinyl alcohol was not provided when the film substrate core was prepared, white bright spots were generated on the pressure-sensitive adhesive or became whitish during heating.

Comparative Examples 1-6:
In the first, 1 ', 2, 2' release film of Example 1, change the presence or absence of a coating film at the time of production of the polyester film, and change the silicone composition when processing the silicone layer on the polyester film. A polyester film was obtained in the same manner as in Example 1 except that the coat thickness was changed. Moreover, in the 2nd mold release film, it manufactured like Example 1 except changing content of a laser marking compound, and obtained the polyester film. Subsequently, in the film base core 31 of Example 1, it manufactured like Example 1 except changing the polyester seed | species, the compounding quantity of polyester, and a layer structure, and obtained the polyester film. Finally, the obtained member was bonded to obtain a target optical pressure-sensitive adhesive sheet. The characteristic results of the obtained sheet are summarized and shown in Tables 3 to 4 below.

  In Comparative Example 1, in order to use as a product, the haze of the film base material was low, and it was at a level with no problem.

  The sheet of the present invention is generally inexpensive and can secure the required transparency as compared with a pressure-sensitive adhesive having the same thickness. Further, in a configuration using a glass substrate, the pressure-sensitive adhesive for optical substrates has an anti-scattering effect. This is useful because it can be suitably used as a sheet, and there is no graininess when bonded to a screen and a member with high visibility can be produced.

DESCRIPTION OF SYMBOLS 10 Adhesive sheet for optical base materials 11 Film base material 12 Film base material coating layer 12 'Film base material coating layer 13 1st adhesive layer 14 1st release film base material 14' 1 '1' release film base material 15th 1 coating layer 15 '1' coating layer 16 1st release agent layer 16 '1' release agent layer 23 2nd adhesive layer 24 2nd release film substrate intermediate layer 24 '2' release film Substrate 24 ′ ′ second release film substrate outermost layer 25 second coating layer 25 ′ second ′ coating layer 26 second release agent layer 26 ′ second ′ release agent layer 31 film substrate core 32 first Release film (light release sheet; release force: 32> 31)
32 '1' release film (light release sheet; release force: 31> 31 ')
33 Second release film (heavy release sheet; release force: 32> 31)
33 '2' release film (light release sheet; release force: 32> 32 ')
41 1st base material-less double-sided adhesive sheet 42 2nd base material-less double-sided adhesive sheet 41 '1st base material-less double-sided adhesive sheet precursor 42' 2nd base material-less double-sided adhesive sheet precursor

Claims (3)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive sheet layer on both sides of a film substrate core having a coating layer obtained by applying a coating solution containing polyvinyl alcohol on both sides of the polyester film, and having a thickness on each surface of the pressure-sensitive adhesive sheet layer The transparency of the pressure-sensitive adhesive sheet when bonded to a 1 mm float glass sheet is 70% or more, the image clarity is 85% or more, each has release films on both sides of the pressure-sensitive adhesive sheet layer, and at least one polyester film A pressure-sensitive adhesive sheet for an optical substrate comprising a laser marking compound in an intermediate layer excluding the outermost layer. The pressure-sensitive adhesive sheet for an optical substrate according to claim 1, wherein the release film has a coating layer obtained by coating a coating liquid containing polyvinyl alcohol on a surface in contact with the pressure-sensitive adhesive sheet layer. The pressure-sensitive adhesive sheet for an optical substrate according to claim 1 or 2, wherein the release film contains 0.025 to 0.25% by weight of a laser marking compound.

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