JP2013231137A - Substrateless double-sided pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrateless double-sided pressure-sensitive adhesive sheet with little adhering foreign matter and suitable for a touch panel by improving a yield in a production process by preventing damage to an electronic component due to peeling electrification generated in peeling a release film, and by preventing adhesion of foreign matter due to electrification of a film surface or a pressure-sensitive adhesive surface.SOLUTION: A substrateless double-sided pressure-sensitive adhesive sheet is formed by laminating each of release films having peel force different from each other on both surfaces of a pressure-sensitive adhesive layer 11 with a thickness of 100 μm or more, wherein a release film 32 having larger peel force is formed of a biaxially oriented polyester film 23 with a thickness of 50 μm or more, a coating layer 24, and a release layer 25 arranged in this order, surface resistivity of the release film surface is 1.0×10Ω or less, and the peel force is in the range of 20-100 mN/cm.

Description

  The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet, for example, a substrate-less double-sided pressure-sensitive adhesive sheet suitably used for a capacitive touch panel.

  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 substrate-less double-sided PSA sheet is first peeled off from the light release sheet, and one side of the exposed PSA layer is bonded to the object surface. The other side of the layer is bonded to a different object surface, thereby surface bonding between the objects.

  In recent years, the use of a baseless double-sided pressure-sensitive adhesive sheet has been spreading, and is also used for members for various optical applications. For example, a touch panel as an optical application is a laminated body in which members such as a transparent conductive film are laminated, and a baseless double-sided pressure-sensitive adhesive sheet is used to join the members.

  In particular, the capacitive touch panel has been expanded as an information terminal by a multi-touch operation in which a screen operation is performed with two fingers.

  Capacitive touch panels have thicker printing steps compared to resistive film methods, so a proposal has been made to cover the printing steps by thickening the adhesive layer, but if the adhesive layer is thicker, When the release film is peeled off, there is a problem that a part of the pressure-sensitive adhesive layer adheres to the release film or bubbles are mixed into the part of the pressure-sensitive adhesive layer transferred to the release film.

  In addition, when using the substrate-less double-sided PSA sheet for optical applications, not only the substrate-less double-sided PSA sheet but also the release film used for it becomes a more important problem than ever. Yes.

JP2010-168425A

  The present invention has been made in view of the above circumstances, and the problem to be solved is that when used for a capacitive touch panel, there are few defects due to deformation of the adhesive, and the surface resistivity of the release film is reduced. By preventing damage to electronic components due to peeling electrification that occurs when the release film is peeled off, and preventing adhesion of foreign matter due to charging on the film surface and adhesive surface, improving the yield in the manufacturing process, An object of the present invention is to provide a substrate-less double-sided pressure-sensitive adhesive sheet suitable for a touch panel with little adhered foreign matter.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be easily solved by a release film having a specific configuration, and has completed the present invention.

That is, it is a substrate-less double-sided pressure-sensitive adhesive sheet in which release films having different peeling forces are laminated on both sides of a pressure-sensitive adhesive layer having a thickness of 100 μm or more, and the release film having the larger peeling force has a thickness of A biaxially oriented polyester film having a thickness of 50 μm or more, a coating layer, and a release layer are formed in this order, and the surface specific resistance value of the release film surface is 1.0 × 10 ¹³ Ω or less, peeling force Is in the range of 20 to 100 mN / cm.

  According to the present invention, in the manufacturing process of the base-less double-sided pressure-sensitive adhesive sheet, until the base-less double-sided pressure-sensitive adhesive sheet is completed by reducing the surface low efficiency of the release film surface on the heavy release side to which the pressure-sensitive adhesive is applied. In this step, the adhesion of foreign matter to each member is suppressed, and at the same time, the thickness of the pressure-sensitive adhesive layer is increased as a capacitive touch panel by setting the polyester film as the base material of the release film to a specific thickness. Even the base material-less double-sided pressure-sensitive adhesive sheet has a good quality with few foreign matters for optical problems and problems in the production process, and the industrial value of the present invention is high.

Typical sectional drawing which shows the base-material-free double-sided adhesive sheet which concerns on embodiment of this invention.

  As shown in FIG. 1, the substrateless double-sided pressure-sensitive adhesive sheet 10 is configured by laminating first and second release films on both sides of a pressure-sensitive adhesive layer 11.

  The first release film 31 is a so-called light release sheet, and is formed by laminating a release substrate 13 made of a polyester film and a first release agent layer 14, and the first release agent layer 14 is an adhesive. It is temporarily attached to the layer 11 so as to be peelable.

  The 2nd release film 32 is what is called a heavy release sheet, Comprising: The application layer 24 and the 1st release agent layer 25 are laminated | stacked on the release film base material 23 which consists of a polyester film, and the 2nd release agent layer is comprised. 25 is temporarily attached to the pressure-sensitive adhesive layer 11 in a peelable manner.

  Examples of the polyester forming the base material used for the release films 31 and 32 include polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. Other examples include polyethylene isophthalate and poly-1,4-butylene terephthalate.

  Examples of copolymer components other than the above-described dominant component include propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, Diol components such as triethylene glycol, polyethylene glycol, polytetramethylene glycol, polyalkylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, Esterogenic derivatives such as azelaic acid, sebacic acid, diphenyl ether dicarboxylic acid and oxymonocarboxylic acid can be used.

  Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used. Examples of resins blended with polyethylene terephthalate include various copolymerized polyethylene terephthalates such as isophthalic acid copolymer, cyclohexanedimethylene terephthalate copolymer, polyethylene glycol copolymer, polyethylene naphthalate and copolymerized polyethylene naphthalate, poly Examples include butylene terephthalate.

  The intrinsic viscosity of the polyester film of the present invention is usually in the range of 0.40 to 0.90, preferably 0.45 to 0.80, and more preferably 0.50 to 0.70. If the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weakened. If the intrinsic viscosity exceeds 0.90, the melt viscosity becomes high, the load on the extruder is increased, and the production cost increases. Problems may occur.

  It is preferable to mix | blend particle | grains in the polyester layer which comprises the polyester film of this invention for the main purpose of provision of slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, it is possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the manufacturing process of the film raw material.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.05-5 micrometers normally, Preferably it is the range of 0.05-3 micrometers. If the average particle size is less than 0.05 μm, the particles tend to aggregate and the dispersibility may be insufficient. On the other hand, if it exceeds 5 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage of producing the polymer constituting each layer.

  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 blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 11, 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.

  The thickness of the pressure-sensitive adhesive layer is 100 μm or more, preferably 120 μm or more. When the thickness of the pressure-sensitive adhesive layer is less than 100 μm, when used as a member of a capacitive touch panel, a printing step becomes a defect, which is not preferable.

  The second release film 32 of the release film used for the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention is formed by providing the biaxially oriented polyester film 23, the coating layer 24, and the release agent layer 25 in this order.

The coating layer 24 has antistatic properties, and the surface resistivity of the film surface provided with a release layer on the coating layer is 1.0 × 10 ¹³ Ω or less, preferably 1.0 × 10 ¹² Ω or less. is there. When the surface specific resistance exceeds 1.0 × 10 ¹³ Ω, the antistatic effect is insufficient, and foreign matter is attracted by static electricity due to peeling charging that occurs when the release film is peeled off from the adhesive layer. When the adhesive layer thus formed is bonded to an electronic substrate, a part of the electronic circuit is damaged, which is not preferable.

  The antistatic coating layer of the coating layer 24 may be a coating layer that is applied to a film that has been biaxially oriented and then heat-fixed to complete crystal orientation, but in the middle of film formation, particularly longitudinal stretching is completed. At that time, after applying a coating agent diluted with a solvent mainly composed of water, drying, transverse stretching, and heat setting are performed to simultaneously perform orientation crystallization of the film and application of an antistatic coating layer, so-called inline Those coated by a method using a coat are preferred.

  In order to achieve the above-mentioned surface specific resistance value, an antistatic agent is added to the antistatic coating layer.

  As the antistatic agent, for example, as an anionic antistatic agent, an alkylsulfonic acid metal salt, and a quaternary amine salt, an alkylbenzenesulfonic acid metal salt, and a quaternary amine salt, a phosphoric ester metal salt, and a quaternary amine salt, Alkyl phosphate metal salt, and quaternary amine salt, polystyrene sulfonate metal salt, and quaternary amine salt, monomer having double bond capable of radical polymerization with styrene sulfonic acid (ethylene, styrene, acrylic acid, acrylic ester) , Methacrylic acid, methacrylic acid ester, vinyl chloride, vinyl acetate, vinyl ether and the like) and metal salts of oligomers and quaternary amine salts.

Examples of the cationic antistatic agent include alkylammonium chloride, alkylbenzeneammonium chloride, and a polymer containing either an ionized nitrogen or pyrrolidinium ring in the main chain. An ionene polymer is mentioned as a polymer containing the nitrogen atom ionized in the principal chain. Specific examples of the compound include JP-B-53-23377, JP-B-54-10039, JP-A-47-34581, JP-A-56-76451, and JP-A-58-93710. Examples described in Japanese Patent Laid-Open Nos. 61-18750, 63-68687, and the like. (Details are described in ALAN D. WILSON and HAVARD J. PROSSER (Ed.) DEVELOPMENTS IN IONIC POLYMERS-2 ELSEVIER APPLIED SCIENCE PUBLISHER, 1986), IONEN POLYMERS :, PROPERITERS. )
On the other hand, as a polymer containing a pyrrolidinium ring in the main chain, examples of specific compounds include JP-A-1-146931, JP-A-1-166326, JP-A-1-171940, and JP-A- No. 171985, JP-A-1-174538, JP-A-1-174539 and the like.

  In addition to these antistatic agents, a compound having an alkylene glycol polymer such as polymethylene glycol, polyethylene glycol, polytetramethylene glycol and the like and a molecular weight of usually 100 to 2000, preferably 500 to 1000 may be used in combination. it can. These alkylene glycol polymers can be added for the purpose of reducing the surface resistivity or reducing the humidity dependence of the antistatic performance.

  In order to improve the durability of the coating layer and the adhesion to the hard coat layer and the like applied thereon, it is possible to add an organic polymer binder in addition to the antistatic agent to the antistatic coating layer. preferable. As the organic polymer binder, it is preferable to use a polyurethane resin, a polyester resin, a polyacrylate resin, or a modified product or a mixture thereof because the adhesion to the hard coat layer is particularly good. When these organic polymer binders are used in in-line coating, in which water is the main solvent and is applied in the film formation process, the molecular weight of these organic polymer binders is such that they are dissolved or finely dispersed in water. A method such as copolymerizing an anionic, cationic, or amphoteric hydrophilic component or adding a water dispersing agent can be used.

  In the present invention, the antistatic coating layer contains an antistatic agent and an organic polymer binder, and the content ratio thereof preferably satisfies 1: 9 to 8: 2 (weight ratio). When the antistatic agent is less than 10% by weight, the antistatic property may be insufficient. On the other hand, when it exceeds 80% by weight, the coating film durability may be insufficient. When providing a hard coat layer etc. on a layer, adhesiveness may become inadequate.

  In addition, a crosslinking agent may be used in combination with the antistatic coating layer. Specifically, methylolated or alkylolized urea compounds, melamines, guanamines, acrylamides, polyamides, epoxy compounds, oxazolines Examples thereof include compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, and zirco aluminate coupling agents. These crosslinking components may be previously bonded to the binder polymer.

  Further, inorganic particles may be contained for the purpose of improving the adhesion and slipperiness of the antistatic coating layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like. Furthermore, an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, organic polymer particles, an antioxidant and the like may be contained as necessary.

  The thickness of the antistatic coating layer in the film of the present invention is usually from 0.01 to 1 μm, preferably in the range from 0.02 to 0.5 μm. When the thickness of the coating layer is less than 0.01 μm, the coating thickness becomes non-uniform or an effective antistatic effect cannot be obtained. On the other hand, when the coating is applied in excess of 1 μm, there are cases in which problems such as easy blocking of the films and reduced slipperiness may occur.

  The release layer of the 1st release film 14 and the 2nd release film 25 will not be specifically limited if the material which has mold release property is contained. 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 curable type, an electron beam curable type, and a solventless type can be used.

  Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, Dow, manufactured by Shin-Etsu Chemical Co., Ltd. -Corning Asia Co., Ltd. DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, Toshiba Silicone Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, Toray Dow Corning Co., Ltd. SD7220, SD7226, SD7229, etc. are mentioned. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  In the present invention, as a method for providing a release layer on the polyester film, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, or the like 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, a coating layer such as an adhesive layer, an antistatic layer or a coating layer may be provided on the surface where the release layer is not provided, and the polyester film is subjected to a surface treatment such as corona treatment or plasma treatment. May be applied.

  The peeling force of the second release film 32 corresponding to the heavy peeling side is preferably in the range of 20 to 100 mN / cm, more preferably 30 to 60 mN / cm. If the peeling force of the second release film is less than 20 mN / cm, when the first release film is peeled off, a part of the second release film is peeled off, which is not preferable. Moreover, when the peeling force of a 2nd mold release film exceeds 100 mN / cm, since problems, such as an adhesive remaining in a 2nd mold release film, arise, it is unpreferable.

  The peeling force of the first release film 31 corresponding to the light peeling side is 3 to 50 mN / cm, preferably 5 to 25 mN / cm.

  If the peeling force of the first release film is less than 3 mN / cm, it is easily peeled off, which is not preferable because the release film is peeled off by a slight external force generated in the manufacturing process. In addition, when the peeling force of the first release film exceeds 50 mN / cm, it is preferable that peeling called “floating” occurs between the second release film and the adhesive layer in the step of peeling the first release film. Absent.

  Even if the peeling force of the 2nd release film 32 is made low by suppressing the peeling force of the 1st release film 31, the peeling force difference of both the release films 31 and 32 can be enlarged.

  Further, by setting the peeling force of the first release film 31 to a certain value or more, the first release film 31 is unexpectedly peeled off from the adhesive layer 11 before use, or the first release film 31 is an adhesive. Floating from the layer 11 is prevented.

  In addition to the peeling force described above, the substrate-less double-sided PSA sheet of the present invention preferably provides a peeling difference between the first release film and the second release film.

  The peeling force of the second release film 32 is usually 2.0 times or more, preferably 2.5 times or more, more preferably 3.0 times or more of the peeling force of the first release film 31. When the peeling force of the second release film 32 is less than 2.0 times the peeling force of the first release film 31, the second release film 32 adheres when the first release film 31 on the light release side is peeled off. The phenomenon of floating from the agent layer 11 may occur, the adhesive may remain on the second release film 32, or zipping may occur.

  The thickness of the biaxially oriented polyester film used as the base material of the first release film 31 and the second release film 32 of the present invention is 50 μm or more, preferably 75 μm or more, more preferably 100 μm or more. When the thickness of the release film is 50 μm or less, the film is not loose, and the peeling angle increases at the boundary where the pressure-sensitive adhesive and the release film are peeled off when the release film is peeled off, so the pressure-sensitive adhesive layer is thick. In some cases, the adhesive remains on the release film or zipping occurs.

  In addition, when the release film is thick, it works as a protective film for the adhesive layer, and the surface of the substrate-less double-sided pressure-sensitive adhesive sheet comes into contact with unevenness or foreign matter or is strongly pressed in each manufacturing process However, it is possible to prevent the influence of the transfer to the pressure-sensitive adhesive layer.

  In particular, when the thickness of the pressure-sensitive adhesive layer is increased, unevenness and foreign matters are easily transferred, so that it is necessary to prevent the adhesive from being affected by a release film having a thick base material.

  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. 1.2 times or 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 floating that occurs at the interface between the second release film and the adhesive layer when the first release film is peeled off.

  In addition, when the adhesive is applied on the release surface of the second release film, in order to eliminate the influence of foreign matter and unevenness in the process, the influence of unevenness and foreign matter is more It is preferable to increase the film thickness of the second release film that is easily received.

  If the ratio between the thickness of the second release film and the thickness of the first release film is less than 1.2 times, the cost contribution tends to be reduced.

  When the thickness of the biaxially oriented polyester film used as the base material for the first release film 31 and the second release film 32 exceeds 300 μm, the manufacturing cost increases.

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

  That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. 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.

  Although the method in particular of forming a coating layer on the surface of a polyester film is not restrict | limited, The method of apply | coating a coating liquid in the process of manufacturing a polyester film is employ | adopted suitably. 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.

  Next, the present description will be further described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C.

(2) Average particle diameter (d50)
The average particle size d50 was defined as the particle size having an integrated volume fraction of 50% in an equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation.

(3) Surface resistivity value Yokogawa-Hewlett-Packard inner electrode 50mm diameter, outer electrode 70mm diameter concentric electrode 16008A (trade name) is placed on the sample in an atmosphere of 23 ° C, 50% RH, A voltage of 100 V was applied, and the surface specific resistance value of the sample was measured with 4329A (trade name) which is a high resistance meter of the company.

(4) Evaluation of release film release force (F) After applying one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the release layer of the sample film, cut into a size of 50 mm × 300 mm After that, 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.

(5) Practical properties / foreign substance inspection A base material-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides was observed and evaluated based on the detection state of foreign substances.
○: No foreign matter is detected, and the quality is sufficient for optical use. △: Foreign matter is detected, but there is no practical problem. ×: Many foreign matters are detected, which is inappropriate for optical use. Limited use

-Generation status of zipping When measuring the peeling force, the release status of the adhesive and the release film was observed, and the occurrence of zipping was evaluated in three stages.
○: Peeling extremely smoothly, no peeling streaking, no peeling noise △: Slight peeling streaks, slight peeling noise, slight zipping ×: Peeling streaks , Peeling sound occurs, zipping occurs

-Peelability of 1st, 2nd release film It evaluated by the condition of a 2nd release layer and an adhesive interface when the 1st release film of the light release side was peeled off.
○: The above is not observed at the interface between the second release layer and the pressure-sensitive adhesive. Δ: Slight floating is observed at the interface between the second release layer and the pressure-sensitive adhesive, but there is no practical problem. There is a clear float at the interface of the adhesive

-Deformation of pressure-sensitive adhesive The base material-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides was observed and evaluated based on the deformation state of the pressure-sensitive adhesive due to foreign matters.
○: Concavities and convexities are not detected and the quality is sufficient for optical use. Δ: Concavities and convexities are detected, but there is no practical problem. ×: Many concavities and convexities are detected, which is inappropriate for optical use. Limited use

<Method for producing polyester (1)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to the reaction mixture, 0.06 part of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm and 0.04 part of antimony trioxide were added, and 4 A time polycondensation reaction was performed. 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 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (1) was 0.53.

<Adjustment of coating layer>
-Coating liquid A (antistatic coating layer composition 1)
40 parts by weight of polyurethane resin (isophorone diisocyanate as isocyanate component, polyester polyol composed of terephthalic acid, isophthalic acid, ethylene glycol, diethylene glycol as polyol component, polyurethane mainly composed of 2,2-dimethylolpropionic acid as chain extender)
30 parts by weight of styrene sulfonic acid soda copolymer acrylic resin (antistatic resin copolymerized mainly with p-styrene sulfonic acid sodium salt, methallyl sulfonic acid sodium salt, N, N′-dimethylamino methacrylate)
15 parts by weight of polyester resin (copolyester containing terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid as dicarboxylic acid components, and ethylene glycol and diethylene glycol as diol components)
Melamine-based crosslinking agent 10 parts by weight (methoxymethylol melamine (degree of methylolation: 5-6))
5 parts by weight of colloidal silica A water-dispersible coating material having a solid weight ratio shown in the antistatic coating layer composition 1 was uniformly applied so that the thickness after film formation was 0.025 μm.

・ Coating layer B (antistatic coating layer composition 2)
Polypyrrolidinium resin hydrochloride 40 parts by weight Polyacrylic resin 50 parts by weight (copolymerization acrylic resin containing methyl methacrylate as a main component and containing N-methylolacrylamide and having self-crosslinking property)
Melamine-based crosslinking agent 10 parts by weight (methoxymethylol melamine (degree of methylolation: 5-6))
The water-dispersible coating material having a solid content weight ratio shown in the antistatic coating layer composition 2 was uniformly applied so that the thickness after film formation was 0.04 μm.

-Coating layer C (Easily adhesive coating layer composition 1)
65 parts by weight of polyurethane resin (isophorone diisocyanate as isocyanate component, polyester polyol composed of terephthalic acid, isophthalic acid, ethylene glycol, diethylene glycol as polyol component, polyurethane mainly composed of 2,2-dimethylolpropionic acid as chain extender)
20 parts by weight of polyester resin (copolyester containing terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid as dicarboxylic acid components, and ethylene glycol and diethylene glycol as diol components)
Melamine-based crosslinking agent 10 parts by weight (methoxymethylol melamine (degree of methylolation: 5-6))
5 parts by weight of colloidal silica The water-dispersible coating material having a solid weight ratio shown in the above easy-adhesion coating layer composition 1 was uniformly applied so that the thickness after film formation was 0.025 μm.

<Manufacture of polyester film>
・ Polyester film-1 (125μm)
Polyester (1) as a raw material is supplied to an extruder with a vent, 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. An amorphous film of about 1500 μm was obtained. This film was stretched 3.3 times in the machine direction at 85 ° C., and the coating solution was applied to a thickness of 0.06 μm on one side of the film, and then stretched 3.6 times in the transverse direction at 100 ° C. A biaxially stretched polyester film having a thickness of 125 μm was obtained by heat treatment.

・ Polyester film-2 (100μm)
Polyester (1) as a raw material is supplied to an extruder with a vent, 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. An amorphous film of about 1300 μm was obtained. The film was stretched 3.5 times in the longitudinal direction at 85 ° C., and the coating solution was applied to a thickness of 0.06 μm on one side of the film, then stretched 3.8 times in the lateral direction at 100 ° C., and 210 ° C. A biaxially stretched polyester film having a thickness of 100 μm was obtained by heat treatment.

・ Polyester film-3 (75μm)
Polyester (1) as a raw material is supplied to an extruder with a vent, 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. An amorphous film of about 1100 μm was obtained. This film was stretched 3.5 times in the longitudinal direction at 85 ° C, and the coating solution was applied to a predetermined thickness on one side of the film, then stretched 4.0 times in the transverse direction at 100 ° C, and heat treated at 210 ° C. Thus, a biaxially stretched polyester film having a thickness of 75 μm was obtained.

・ Polyester film-4 (50μm)
Polyester (1) as a raw material is supplied to an extruder with a vent, 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. An amorphous film of about 740 μm was obtained. This film was stretched 3.7 times in the machine direction at 85 ° C., and the coating solution was applied to a predetermined thickness on one side of the film, then stretched 4.0 times in the transverse direction at 100 ° C., and heat-treated at 210 ° C. Thus, a biaxially stretched polyester film having a thickness of 50 μm was obtained.

・ Polyester film-5 (38μm)
Polyester (1) as a raw material is supplied to an extruder with a vent, 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. An amorphous film of about 550 μm was obtained. This film was stretched 3.7 times in the longitudinal direction at 85 ° C, and the coating solution was applied to a predetermined thickness on one side of the film, then stretched 3.9 times in the transverse direction at 100 ° C, and heat-treated at 210 ° C. Thus, a biaxially stretched polyester film having a thickness of 38 μm was obtained.

<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.

-Release layer composition-1
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

・ Releasing layer composition-2
Curing type silicone resin (KS-774: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-4: manufactured by Shin-Etsu Chemical) 10 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

・ Release layer composition-3
Curable silicone resin (KS-723A: manufactured by Shin-Etsu Chemical) 100 parts Curable silicone resin (KS-723B: manufactured by Shin-Etsu Chemical) 5 parts Curing agent (PS-3: manufactured by Shin-Etsu Chemical) 5 parts MEK / toluene mixed solvent (mixed) The ratio is 1: 1) 1500 parts

-Release layer composition-4
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 95 parts Heavy release control agent (SD-7292: manufactured by Dow Corning Toray) 5 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

-Release layer composition-5
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 95 parts Heavy release control agent (SD-7292: manufactured by Toray Dow Corning) 3 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

-Release layer composition-6
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 95 parts Heavy release control agent (SD-7292: manufactured by Toray Dow Corning) 10 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

Example 1:
<Manufacture of second release film>
A release layer composition 2 was provided on the polyester film 1 having a thickness of 125 μm coated with the coating liquid A so that the coating amount was 0.1 g / m ² (after drying) to obtain a second release film. The characteristics of the obtained release film are shown in Tables 3 to 5 below.
<Manufacture of first release film>
A release layer composition 1 was provided on a polyester film 4 having a thickness of 50 μm so that the coating amount was 0.1 g / m ² (after drying) to obtain a first release film. The characteristics of the obtained release film are shown in Tables 3-5.
<Manufacture of substrate-less double-sided PSA sheet>
On the release agent layer of the obtained second release film, the acrylic pressure-sensitive adhesive solution was applied using an applicator so that the film thickness after drying was 150 μm, and then the applied film was The adhesive layer was formed by drying at 120 ° C. for 1 minute. 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 of Example 1 was obtained.

Examples 2-4, Comparative Examples 1-6:
Example 1 except that the polyester used in the release film and the release layer composition were changed as shown in Tables 1 and 2 below in the production of the second release film of Example 1 and the production of the first release film. In the same manner as above, a second release film and a first release film were obtained. Using the obtained release film, the substrateless double-sided PSA sheets of Examples 2 to 4 and Comparative Examples 1 to 6 were obtained in the same manner as Example 1.

* 1: Peeling force ratio means 2nd release film peeling force / 1st release film peeling force.
* 2: The film thickness ratio means the second release film thickness / the first release film thickness. The following Table 4 and Table 5 are also synonymous.

  The release film for a substrate-less double-sided pressure-sensitive adhesive sheet used for the capacitive touch panel and the like of the present invention has less foreign matter adhesion in the manufacturing process of the substrate-less double-sided pressure-sensitive adhesive sheet. It can suppress the bad influence of this, can suppress a manufacturing loss by the outstanding peeling characteristic, and can use it suitably as a release film for the base-material-free double-sided adhesive sheet used for a capacitive touch panel.

DESCRIPTION OF SYMBOLS 10 Substrate-less double-sided adhesive sheet 11 Adhesive layer 13 1st release film base material 14 1st release agent layer 23 2nd release film base material 24 2nd application layer 25 2nd release agent layer 31 1st release Type film (light release sheet)
32 Second release film (heavy release sheet)

Claims (1)

A substrate-less double-sided pressure-sensitive adhesive sheet in which release films having different peeling forces are laminated on both sides of an adhesive layer having a thickness of 100 μm or more, and the release film having the larger peeling force has a thickness of 50 μm or more The biaxially oriented polyester film, the coating layer, and the release layer are provided in this order, and the surface specific resistance value of the release film surface is 1.0 × 10 ¹³ Ω or less and the peel force is 20 A substrate-less double-sided pressure-sensitive adhesive sheet characterized by being in a range of -100 mN / cm.

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