JP2009184269A - Release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a release film wherein high level accuracy in a test by a cross-nicol method of a deflection plate, and increasing production yield by a reduction of roll-cleaning and improvement of qualities by a reduction of foreign materials can be realized in a manufacturing process using a release film. <P>SOLUTION: The release film includes a releasing layer having a releasing force of 10 to 100 mN/cm in one surface side of a polyester film having 11 to 25 nm of an arithmetical mean of roughness (Ra) in a surface of the film and 90% or more of a mapping value, and the releasing layer includes a pressing adhesion rate of 70 to 95% and 0.10 to 0.28 of a friction coefficient between an opposite side surface of the releasing layer and a metal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a release film. Specifically, it is excellent in optical characteristics, which is an important characteristic in a film for liquid crystal display applications, etc., and can provide a high degree of accuracy in producing defects in film inspection. In a manufacturing process using a mold film, the present invention relates to a release film with very little roll contamination in the manufacturing process.

  A release film with a release layer on a polyester film typified by polyethylene terephthalate or polyethylene naphthalate has excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties. Because of its excellent cost performance, it is used in various applications. However, as the use diversifies, the processing conditions and usage conditions of the film become diversified. When used as an optical release film such as a polarizing plate, in the polyester film used for the release film in the inspection of foreign matter The particle component of the product becomes a bright spot, causing problems such as a decrease in inspection accuracy, or when oligomers present on the film surface come into contact with the roll in the manufacturing process and become foreign matter, causing product defects Or worsening the yield of the manufacturing process.

  For example, when an oligomer on the surface of a polyester film accumulates on a roll and enters the product as a foreign substance and is used for optical applications, it becomes a fatal defect as an optical product, and the line is stopped to remove the deposited oligomer. However, when the line needs to be cleaned, the yield may deteriorate, and it may not be possible to cope with a reduction in price.

  In recent years, with the rapid spread of mobile phones and personal computers, the demand for LCDs that are thinner, lighter, consume less power, and have higher image quality than CRTs, which are conventional displays, is growing significantly. The technology has grown significantly for larger screens. As an example of increasing the screen size of LCD, recently, LCD is used for large TV applications of, for example, 30 inches or more. An LCD with a large screen is often a bright LCD with a large screen by increasing the luminance of a backlight incorporated in the LCD or incorporating a film for improving the luminance into a liquid crystal unit.

  In such a so-called high-brightness type LCD, a small bright spot existing in the display is often a problem, and in a component such as a polarizing plate, a retardation plate or a retardation polarizing plate incorporated in the display, As a result, a foreign matter having a minute size, which has not been a problem in conventional low-brightness LCDs, has become a problem. For this reason, while preventing the entry of foreign matter in the manufacturing process, it is also important to improve the inspection accuracy so that even if foreign matter is mixed, it can be recognized as a defect.

  Conventionally, the particles in the polyester film are usually used for ensuring the slipperiness and winding characteristics of the film. If the particle size and blending amount are not satisfied, the desired slipperiness cannot be ensured. As a result, the winding characteristics deteriorate, and as a result, the productivity deteriorates. However, when the particle size and blending amount are within the normally used range, as described above, when used as a release film for polarizing plates, the added particles become bright spots in the defect inspection process, which hinders inspection. Is a problem.

  For example, as a defect inspection of a polarizing plate, a visual inspection by the crossed Nicols method is generally used. Further, for example, for a polarizing plate used for large TV applications of 40 inches or more, an inspection by an automatic defect inspection device using the crossed Nicols method is used. Is also being implemented. The crossed Nicols method is a method in which two polarizing plates are put in a quenching state with their orientation main axes orthogonal to each other, and if there are foreign matters or defects, they appear as bright spots, so that a visual defect inspection can be performed. Here, the pressure-sensitive adhesive layer is usually provided on the polarizing plate, and a polyester film provided with a release layer is used as the release film for that purpose. When a product having such a configuration is inspected, a crossed Nicols inspection is performed in a state where a release polyester film is sandwiched between two polarizing plates. In general, when a release polyester film is used for this, foreign matter and defects are difficult to see in the crossed Nicols inspection, and it may be easy to miss them.

  Regarding these, when a polyester film is sandwiched between two polarizing plates, an inspection property is improved when the retardation value is within a certain range (see Patent Document 1). Even if these are used at a level where quality is required, accuracy may be insufficient when inspection is performed to find defects reliably.

JP 2000-338327 A

  The present invention is intended to solve such a problem, the problem to be solved is that it is possible to achieve a high degree of accuracy in the inspection of the polarizing plate by the crossed Nicols method, and further, a manufacturing process using a release film In the above, it is intended to provide a release film that prevents the contamination of oligomers and the like generated from the release film, thereby improving the production yield by reducing roll cleaning and improving the quality by reducing foreign matter.

  As a result of intensive studies in view of the above problems, the present inventors have found that a release film made of a polyester film having a specific configuration is suitable for optical use without deteriorating excellent film properties. The present invention has been found out and can be completed.

  That is, the gist of the present invention is that the arithmetic average roughness (Ra) of the film surface is 11 to 25 nm and the peelability is 10 to 100 mN / cm on one side of the polyester film having a image clarity value of 90% or more. The release layer has a press adhesion rate of 70% to 95%, and the friction coefficient between the surface on the opposite side of the release layer and the metal is 0.10 to 0.00. It exists in the release film characterized by being the range of 28.

Hereinafter, the present invention will be described in detail.
The polyester film that is the substrate of the release film 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 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.

  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 content of the film layer to which these particles are added is usually 1% by weight or less, preferably 0.01 to 1% by weight, and more preferably 0.02 to 0.6% by weight. When the content of the particles is small, sufficient roughness cannot be given to the film surface, and in the film production process, there is a tendency that the surface is easily scratched or the winding properties are inferior. Further, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large, and the transparency may be impaired.

  The average particle size of the particles contained in the polyester film is 0.02 to 5 μm, preferably 0.1 to 3 μm, and more preferably 0.2 to 1.8 μm. When the particle size is less than 0.02 μm, sufficient roughness cannot be given to the film surface, and the winding characteristics in the film production process tend to be inferior. When the particle diameter exceeds 5 μm, when used as a polarizing plate release film, it may become a bright spot and hinder the defect 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.

  In the present invention, the image clarity value of the film measured by the method described later needs to be 90% or more. When the image clarity value of the film is less than 90%, when used as a polarizing plate release film, the image is distorted during defect inspection of the polarizing plate with transmitted light, which hinders visual inspection and automatic inspection. .

  Moreover, the arithmetic mean roughness (Ra) of a film needs to be 11-25 nm, More preferably, it is 11-22 nm. When the film Ra exceeds 25 nm, the flatness of the surface is impaired and the film becomes whitish, which hinders inspection. Conversely, when Ra of the film is less than 11 nm, the film surface becomes extremely flat, and the winding characteristics in the film manufacturing process are inferior.

  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 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 oligomer precipitation is obtained, which is particularly preferable.

  The polyester film according to the present invention preferably has a variation in orientation angle of 3 degrees / 500 mm or less, more preferably 2 degrees / 500 mm or less, measured in the method described in the examples. When the variation in the orientation angle exceeds 3 degrees / 500 mm, the transmitted light intensity varies depending on the position of the polarizing plate when inspecting the polarizing plate, which may be an obstacle to stable inspection of the polarizing plate.

  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 100 μm, preferably 15 It is in the range of ˜50 μm. If the film thickness is less than 10 μm, the film has insufficient elasticity and tends to cause trouble in the process of peeling the release film. When the film thickness exceeds 100 μm, the manufacturing cost increases, which is against the demand for lower prices.

  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 of dimethyl terephthalate and ethylene glycol, 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 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.

  The polyester film of the present invention can be subjected to so-called in-line coating for treating the film surface during the stretching step as long as the effects of the present invention are not impaired. 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 or water-dispersed for in-line coating.

  Next, formation of the release layer in the present invention will be described.

  The release layer constituting the release film in the present invention may be provided on the polyester film in the film production process such as the above-described coating stretching method (inline coating), and is applied outside the system on the once produced film. So-called off-line coating may be employed, and any method may be employed. The coating stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the first stage of stretching may be completed and the coating treatment may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

  Moreover, it is preferable that the release layer which comprises the release film in this invention contains a curable silicone resin in order to make mold release property favorable. 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, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62 -7213, GE Toshiba Silicones Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, SM3200, SM3030, Toray Da DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, SRX357, SRX211, SD7220, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, BY24-452, SP7265S, SP7265S , LTC1000M, LTC1050L, SYLOFF7900, SYLOFF7198, SYLOFF22A, and the like. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  Moreover, in this invention, in order to give slipperiness | lubricity to a mold release layer surface, you may mix | blend the migration component which consists of a nonfunctional siloxane.

  In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited. For example, when the release layer is provided by a coating stretching method (inline coating), it is usually 170 to 280. The heat treatment should be carried out at a temperature of 3 to 40 seconds, preferably 200 to 280 ° C. for 3 to 40 seconds. On the other hand, when providing a release layer by off-line coating, 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. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed irrespective of the coating extending | stretching method (in-line coating) or offline coating. In addition, a conventionally well-known apparatus and energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount of the release layer from the viewpoint of coating property, usually 0.005~1g / ^{m 2,} preferably in the range from 0.005 to 0.5 / ^{m 2.} When the coating amount is less than 0.005 g / m ² , the coating property is lacking in stability and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 1 g / m ² , the coating layer adhesion and curability of the release layer itself may decrease.

  In the present invention, when a release layer is provided on the coating layer, the film may be temporarily wound after the coating layer is provided, and the release layer may be provided again. After the coating layer is provided, the release layer is continuously provided. A mold layer may be provided on the coating layer, and any method may be adopted.

  Regarding the release film in the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided on the surface where the release layer is not provided, as long as the gist of the present invention is not impaired.

  Further, the polyester film constituting the release film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The peeling force of the release film in the present invention is in the range of 10 to 100 mN / cm, preferably 10 to 50 mN / cm. If the peeling force is less than 10 mN / cm, the peeling force may become too light and may cause a problem of easy peeling even in a scene where it is not necessary to peel off. On the other hand, if it exceeds 100 mN / cm, the peeling force Becomes too heavy, and the pressure-sensitive adhesive is deformed when it is peeled off, which causes a problem in a later step or the pressure-sensitive adhesive adheres to the release film side.

  In the present invention, the coefficient of friction between the release layer surface of the release film and the metal is in the range of 0.10 to 0.28, preferably 0.15 to 0.25. When the friction coefficient exceeds 0.28, the oligomer adheres to the surface of the metal roll in contact with the releasable layer surface, and the adhered oligomer accumulates on the roll and becomes a foreign matter, which is not preferable. In addition, when the friction coefficient is less than 0.10, the film is too slippery, so that a problem such as slipping of the nip roll occurs in the manufacturing process, or the film is displaced when wound in a roll shape. It becomes difficult to obtain a product.

  The present invention uses the property that silicon migrates to the opposite surface of the release layer when the release component used in the release layer is wound on a roll, thereby providing excellent slipperiness without changing the surface roughness. It is characterized in that both excellent optical properties and slipperiness can be achieved.

  Furthermore, in the present invention, in order to improve the slipperiness of the film and prevent the adhesion of the oligomer to the metal roll, the press adhesion rate is in the range of 70 to 95%, more preferably 85 to 90%. When the press adhesion rate exceeds 95%, the slipperiness of the film is not improved, and the oligomer tends to adhere to the metal roll, which is not preferable. If the press adhesion rate is less than 70%, the film is too slippery, so that problems such as slipping of the nip roll occur in the manufacturing process, or the film is displaced when wound into a roll, and the roll-shaped product is It becomes difficult to obtain.

  According to the present invention, it is possible to provide a release film made of a polyester film that can be used for optics such as a polarizing plate and a retardation plate, and has as few luminescent spots as possible and can improve the accuracy of foreign matter inspection. The release film has very little roll contamination in the production process, and as a result, the production process can be made more efficient and foreign matter in the product can be reduced extremely. According to the release film of the present invention, its industrial Value is high.

  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 measuring method used in the present invention 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) Measurement of variation in orientation angle in the film In the width direction of the polyester film, from the center position toward the both ends in the width direction, the sample at every 500 mm and the samples at the extreme ends are cut out, respectively, Oji measuring instruments Using an automatic birefringence meter (KOBRA-21ADH) manufactured by the company, the change in orientation angle every 500 mm in the film width direction was determined. When calculating the change in the orientation angle including the positions at the extreme ends, if the distance between the sample positions is less than 500 mm, the change in the orientation angle every 500 mm is calculated by proportional calculation. Subsequently, a 3 m length was cut out in the longitudinal direction of the film, and a sample was cut out from a total of 7 positions every 500 mm (including both ends) in the longitudinal direction from the center in the film width direction, and the orientation angle was determined. Thus, the variation of the orientation angle for every 500 mm in the width direction and the longitudinal direction was obtained, and the maximum variation value was set as the variation of the orientation angle of the film. Further, in the measurement, it is important to make the reference axis of the orientation angle the same in all samples, and the reference axis can be arbitrarily determined.

(4) Measurement of image clarity value According to JIS-K7105, the image clarity value of the film was measured by a transmission method with a image clarity measuring device ICM-1 manufactured by Suga Test Instruments Co., Ltd. The value is read from an optical comb of 0.125 mm.
(5) Arithmetic mean roughness (Ra)
It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F).
That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [μm].

Ra = (1 / L) ∫ L 0 | f (x) | dx

  The arithmetic average roughness was represented by an average value of the arithmetic average roughness of the extracted portion obtained from 10 cross-sectional curves obtained from the sample film surface and obtained from these cross-sectional curves. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(6) Measurement of coating amount of mold release layer Mold release under the following measurement conditions by FP (Fundamental Parameter Method) method using a fluorescent X-ray measurement device (Shimadzu Corporation "model" XRF-1500 "). The amount of silicon element on the surface provided with the release layer and the surface without the release layer of the film was measured, and the difference was taken as the amount of silicon element in the release layer. Next, the coating amount (Si) (g / m ² ) as a unit of —SiO (CH ₃ ) ₂ was calculated using the obtained amount of silicon element.

"Measurement condition"
Spectral crystal: PET (pentaerythritol)
2θ: 108.88 °
Tube current: 95 mA
Tube voltage: 40 kv

(7) Evaluation of peel strength (F) of release film Affixed with one side of double-sided adhesive tape (Nitto Denko "No. 502") on the surface of the release layer of the sample film, then cut to a size of 50mm x 300mm After that, the peel force 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.

(8) Evaluation of press adhesion rate << Press Adhesive Strength >>
The press treatment is performed under the conditions of 75 μm polyester film / measurement sample film / 75 μm polyester film, temperature 60 ° C., pressure 1 MPa, and time 120 minutes. After the press treatment, on the surface of the 75 μm polyester film that was in contact with the measurement sample film release layer surface, Nitto No. 31 tape is affixed and peeling force (A) 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.

《Basic adhesive strength》
To the same 75 μm polyester film used for the press treatment, Nitto No. A 31 tape is affixed, the peel force (B) is measured in the same manner as the peel force (A), and the press adhesion rate is determined based on the following formula.

Press adhesive rate (%) = (Press adhesive force / Basic adhesive force) × 100
The measurement is performed at 20 ± 2 ° C. and 65 ± 5% RH.

(9) Evaluation of residual adhesive rate of release film << residual adhesive strength >>
The surface of the release layer of the sample film is Nitto Denko (manufactured) No. The 31B adhesive tape is subjected to one reciprocating pressure bonding with a 2 kg rubber roller, and heat-treated at 100 ° C. for 1 hour. Next, the sample film was peeled off from the pressure-bonded sample. The adhesive strength of the 31B pressure-sensitive adhesive tape is measured according to the method of JIS-C-2107 (adhesive strength to stainless steel plate, 180 ° peeling method). This is the residual adhesive strength.

《Basic adhesive strength》
Using the same tape (No. 31B) as in the case of residual adhesive force, an adhesive tape is pressure-bonded to a stainless steel plate according to JIS-C-2107, and measurement is performed in the same manner. The value at this time is defined as the basic adhesive strength. Using these measured values, the residual adhesion rate is determined based on the following equation.

Residual adhesion rate (%) = (residual adhesive force / basic adhesive force) × 100
The measurement is performed at 20 ± 2 ° C. and 65 ± 5% RH.

(10) Coefficient of dynamic friction with metal (μd) (with illustration)
At least 20 films are peeled off from the surface layer of the roll sample stored for 2 weeks or more, and a sample for measurement is collected. A film is wound around a fixed hard chrome-plated metal roll (diameter 6 mm) and brought into contact with an angle of 135 ° (θ), a load of 53 g (T2) is applied to one end, and this is run at a speed of 1 m / min. The resistance force (T1 (g)) was measured, and the coefficient of friction during running (μd) was obtained from the following equation.
μd = (1 / θ) ln (T1 / T2) = 0.424ln (T1 / 53)

(11) Visual inspectability under reflected light 10 inspectors visually observe the polarizing film with a release film under the reflection of a fluorescent lamp, and the visual inspectability under reflected light is evaluated according to the following criteria. did. In the measurement, an A4 size sample was cut out from a position corresponding to a position of 50% with respect to the film width in the film width direction from the end of the obtained release film.
<Criteria for visual inspection under reflected light>
(Good inspection) ◎>○>△>×> XX (Inspection failure)
Among the above criteria, those above Δ are levels that can be used without any problem in actual use.

(12) Foreign matter recognition under crossed Nicols When creating a polarizing plate with a release film, 50 metal particles / matter of black metal powder (foreign matter) having a size of 50 μm or more between the adhesive and the polarizing film ² was mixed. A polarizing plate for inspection is superimposed on the polarizing plate release film mixed with the foreign matter thus obtained so that the orientation axis is orthogonal to the width direction of the release film, and white light is irradiated from the polarizing plate side. Ten inspectors visually observed from the polarizing plate for inspection, and evaluated whether the foreign matter mixed between the adhesive and the polarizing film could be found by the following classification. In addition, in the case of a measurement, it evaluated using the film of the center part of the obtained film.
<Foreign substance recognition classification criteria>
(Good foreign body recognition) ◎ ＞ ○ ＞ △ ＞ × (foreign body poor recognition)
Among the above criteria, those above ○ are levels that can be used without any problem in actual use.

(13) Release properties The release properties were evaluated from the situation when the release film was peeled off from the polarizing plate with the release film.
○: The release film is peeled off cleanly, and the phenomenon that the adhesive adheres to the release layer is not observed. Δ: The release film peels off, but the adhesive adheres to the release layer when peeled off at a high speed. : Adhesive adheres to the release film Among the above criteria, those above Δ are levels that can be used without problems in actual use.

(14) Roll contamination status When a laminated film having an adhesive layer was produced, each roll of the production apparatus was visually observed to evaluate the roll contamination status.
○: No deposits are observed on the roll surface after manufacture Δ: Slight deposits are observed on the roll surface after manufacture, but there is no problem in manufacturing ×: Deposits are observed on the roll surface after manufacture , Need roll cleaning

(15) Proper processing In the production of a laminated film having an adhesive layer, the production status was evaluated according to the following ranks.
○: Manufactured without problems. △: A problem occurred, but the product could be manufactured. ×: A problem occurred and the product could not be manufactured. It is a level that can be used without any problems.

(16) Roll appearance In the production of the release film, the appearance of the product roll of the release film was visually observed and evaluated. In particular, the deviation of both end faces of the roll was observed.
(Roll appearance is good) ◎>○>△> × (Roll appearance is bad)
Among the above criteria, those above Δ are levels that can be used without any problem in actual use.

<Manufacture of polyester (A)>
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 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip (A). This polyester had an intrinsic viscosity of 0.63 and an oligomer (cyclic trimer) content of 0.98% by weight.

<Manufacture of 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 2% 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 0.63 and an oligomer (cyclic trimer) content of 0.98% by weight.

<Manufacture of polyester (C)>
In the production method of polyester (B), the additive particles are the same as the production method of polyester (B) except that the synthetic calcium carbonate particles having an average particle diameter of 1.5 μm and the content with respect to the polyester are 1% by weight. Polyester (C) was obtained using the method. The obtained polyester (C) had an intrinsic viscosity of 0.63 and an oligomer (cyclic trimer) content of 0.98% by weight.

<Manufacture of polyester (D)>
In the method for producing polyester (B), the additive particles are the same as the method for producing polyester (B), except that silica particles having an average particle size of 2.2 μm and the content with respect to polyester are 0.6% by weight. Polyester (D) was obtained using the method. The obtained polyester (D) had an intrinsic viscosity of 0.63 and an oligomer (cyclic trimer) content of 0.98% by weight.

Examples 1-7, Example 9, Comparative Examples 1-6:
<Manufacture of polyester film>
A mixed raw material obtained by mixing the polyester (A) chip and the polyester (B), (C), and (D) chips in the proportions shown in Tables 1 to 3 is used as a raw material for the outermost layer (surface layer) and the intermediate layer. Each was supplied to two extruders, 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., then subjected to a preheating step in the tenter and subjected to transverse stretching of 4.9 times at 120 ° C., followed by heat treatment at 190 ° C. for 10 seconds, 10% relaxation was applied in the width direction at 180 ° C. to obtain 3000 mm width polyester films, respectively. The total thickness of the obtained film was 40 μm, and the thickness of each layer was 4 μm / 32 μm / 4 μm.

  In addition, since the film of Comparative Example 1 was extremely flat in surface shape and deteriorated in slipperiness, when the film after stretching and heat treatment was wound into a roll, the film could not be wound well, Scratches occurred on the entire surface of the film, and it was not a product.

<Manufacture of release film>
For films other than Comparative Example 1, a release agent having the following release agent composition was applied by a reverse gravure coating method so that the coating amount (after drying) was 0.1 g / m ² , and the dryer temperature was 120 ° C. A roll-shaped release film was obtained under the conditions of a line speed of 30 m / min.

(Release composition -A)
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part Polyether-modified silicone oil (KF-351: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent ( The mixing ratio is 1: 1) 1500 parts

(Releasing agent composition -B)
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part Polyether-modified silicone oil (KF-351: manufactured by Shin-Etsu Chemical Co., Ltd.) 3 parts MEK / toluene mixed solvent ( The mixing ratio is 1: 1) 1500 parts

(Releasing agent composition-C)
Curable 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

(Releasing agent composition-D)
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part Polyether-modified silicone oil (KF-351: manufactured by Shin-Etsu Chemical) 0.5 part MEK / toluene mixed Solvent (mixing ratio is 1: 1) 1500 parts

(Releasing agent composition-E)
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 agent composition-F)
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part Polyether-modified silicone oil (KF-351: manufactured by Shin-Etsu Chemical) 8 parts MEK / toluene mixed solvent ( The mixing ratio is 1: 1) 1500 parts

(Releasing agent composition-G)
Curing type silicone resin (KS-854: manufactured by Shin-Etsu Chemical Co., Ltd.) 100 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

(Releasing agent composition-H)
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part Polyether-modified silicone oil (KF-351: manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts MEK / toluene mixed solvent ( The mixing ratio is 1: 1) 1500 parts

Example 8:
In the production of the polyester film of Example 1, a release film was obtained in the same manner as in Example 1 except that the thickness of the film was 10 μm.

(Manufacture of laminated film having an adhesive layer)
Acrylic pressure-sensitive adhesive was applied to the surface of the release layer of the release film obtained in Examples and Comparative Examples so that the thickness after drying was 25 μm, and passed through a 130 ° C. drying furnace in a passage time of 30 seconds. Then, a 38 μm-thick polyester film was laminated to prepare a laminated film having an adhesive layer.

(Acrylic adhesive coating solution)
Acrylic adhesive (Olivein BPS429-4: manufactured by Toyo Ink) 100 parts Curing agent (BPS8515: manufactured by Toyo Ink) 3 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 50 parts

  The obtained results are summarized and shown in Tables 1 and 2 below.

  The film of the present invention can be suitably used as an optical release film, for example.

Claims (1)

A film having a release layer with a peel strength of 10 to 100 mN / cm on one side of a polyester film having an arithmetic average roughness (Ra) of 11 to 25 nm and an image clarity value of 90% or more. Yes, the press adhesion rate of the release layer is in the range of 70% to 95%, and the friction coefficient between the surface on the opposite side of the release layer and the metal is in the range of 0.10 to 0.28. A release film.