JP2009199024A - Mold release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release film comprising a polyester film which acheives high accuracy without having such deficiencies that foreign matters or defects are likely not to be viewed or to be overlooked in the inspection of a polarizing plate by a cross-Nicol method. <P>SOLUTION: The mold release film has the mold release layer provided by a coating and drawing method on one surface of the polyester film having 11-25 nm surface roughness (Ra) and ≥90% image clarity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a polyester film which is an important characteristic in films for liquid crystal display applications, etc., has excellent optical characteristics, and can obtain a high degree of accuracy in defect detection in film inspection, and is particularly suitable for polarizing plates. Relates to a mold film.

  Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc. It is used in applications. However, as the application diversifies, the processing conditions and use conditions of the film diversify, and when used as a release film for polarizing plates, the particle component in the polyester film used for the release film when inspecting foreign matter. May become a bright spot, which may cause problems such as a decrease in inspection accuracy.

  In recent years, with the rapid spread of mobile phones and personal computers, the demand for liquid crystal displays (LCDs) that are thinner, lighter, consume less power, and have higher image quality than the conventional display CRT is growing significantly. There is also a remarkable growth in the technology for increasing the screen size of LCDs. As an example of increasing the screen size of an LCD, the LCD has recently been used for large TV applications of 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 addition, in a 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, There is a tendency that a minute size foreign matter which is not a problem at all in a low brightness type LCD is regarded as a problem. For this reason, while aiming at preventing foreign matter from being mixed in the manufacturing process, it is necessary to further 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 to ensure the slipperiness and winding properties of the film, and if the appropriate particle size and blending amount are not satisfied, the desired slipperiness is ensured. Since it is difficult, the winding characteristics are deteriorated and the productivity is deteriorated. However, when the particle size and blending amount are within the normally used range, as described above, when used as a release film for a polarizing plate, the added particles become bright spots in the foreign substance inspection process, which hinders inspection. Is a problem.

  For example, a visual inspection by the crossed Nicols method is generally used as a defect inspection of the polarizing plate, and an inspection by an automatic foreign matter inspection device using the crossed Nicols method is also used for a polarizing plate used for a large TV application of 40 inches or more. It is being implemented. In this crossed Nicol method, two polarizing plates are placed in an extinguished 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 visual defect inspection is possible. 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 problems, and the problem to be solved is to provide a release film made of a polyester film capable of realizing a high degree of accuracy in the inspection of the polarizing plate by the crossed Nicols method. It is in.

  As a result of intensive studies in view of the above problems, the present inventors have determined that a release film suitable for a polarizing plate can be obtained without deteriorating excellent film properties, according to a release film comprising a polyester film having a specific configuration. The present invention has been found out and can be completed.

  That is, the gist of the present invention is that a polyester film having a surface roughness (Ra) of 11 to 25 nm and an image clarity value of 90% or more has a release layer provided by a coating stretching method on one side. It exists in the release film for polarizing plates characterized by this.

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

  The polyester 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, the film surface may be flattened, and in the film production process, the surface may be easily scratched or the winding characteristics may be 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 2 μm, preferably 0.1 to 1.8 μm, more preferably 0.2 to 1.6 μm. When the particle size is less than 0.02 μm, the film surface becomes flat and the winding properties in the film production process tend to be inferior. When the particle diameter exceeds 2 μm, when used as a release film for a polarizing plate, it may become a bright spot and hinder foreign matter inspection. On the other hand, in order to improve the transparency of the film, when a laminated film of two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers.

  In the polyester film which comprises the release film in this invention, it is necessary to ensure a high degree testability for the purpose of the test | inspection precision improvement in a test process. Among them, as an index for preventing the deterioration of the inspection accuracy due to the reflection of the film, in the present invention, the image clarity value of the film is used as a substitute for practical characteristics.

  From such a viewpoint, in the present invention, the image clarity value of the film in the measurement methods described in the examples needs to be 90% or more. When the image clarity value of the film is less than 90%, when used as a release film for a polarizing plate, the image is distorted during defect inspection of the polarizing plate by transmitted light, and hinders visual inspection or automatic inspection. Become.

  Further, the surface roughness (Ra) of the film needs to be 11 to 25 nm, and more preferably 11 to 22 nm. When Ra exceeds 25 nm, the flatness of the surface is impaired, and the film becomes whitish, which hinders inspection. On the other hand, when Ra 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 surface roughness (Ra) of the film and the image clarity value of the film must satisfy the above ranges at the same time in order to improve the inspection accuracy in the polarizing plate manufacturing process, particularly in the inspection process. From such a viewpoint, it is preferable that the particles contained in the polyester contain calcium carbonate particles.

  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 chipped 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.

  In the polyester film of the present invention, the variation in the orientation angle in the film (the measurement method will be described later) is preferably 3 degrees / 500 mm or less, more preferably 2 degrees / 500 mm or less. 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 is an undesirable obstacle to stable inspection of the polarizing plate.

  The total thickness of the film of the present invention is not particularly limited as long as it can be formed as a film, but is usually in the range of 6 to 125 μm, preferably 9 to 75 μm.

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 is carried out, the product is transferred to a polymerization tank, the temperature is increased while reducing the pressure, and finally vacuum is applied. Under heating to 280 ° C., the polymerization reaction proceeds to obtain a polyester.

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

  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.

  In the polyester film of the present invention, as long as the effects of the present invention are not impaired, it is an essential requirement to apply a so-called in-line coating that treats the film surface during the stretching step. 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.

Next, formation of the release layer in the present invention will be described.
The required characteristics of the release film in the present invention include good film flatness for the purpose of reducing thermal wrinkles. Moreover, in the liquid crystal display, since it is necessary to further improve the screen collection efficiency as the screen size increases, a wider release film is required.

  As a method for simultaneously satisfying the above-mentioned required characteristics, the release film in the present invention is required to have a release layer provided on the polyester film by a coating stretching method (in-line coating). .

  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.

  In addition, the release layer constituting the release film in the present invention preferably contains an emulsion type curable silicone resin in order to improve the release property. It may be a type mainly composed of an emulsion type curable silicone resin, or a modified silicone type by graft polymerization with an organic resin such as urethane resin, epoxy resin, alkyd resin, etc. within a range not impairing the gist of the present invention. May be used.

  Specific examples of the emulsion-type curable silicone resin include Dehesive 430 and Dehesive 440 made by Asahi Kasei Wacker Silicone, Silicone 902 made by Arakawa Chemical, and the like.

  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 may be performed at a temperature of 3 to 40 seconds, preferably 200 to 280 ° C. for 3 to 40 seconds. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. 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 to 0.5 / ^{m 2,} preferably in the range of 0.005~0.2g / ^{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, in the case of thick coating exceeding 0.5 g / m ² , the coating film adhesion and curability of the release layer itself may be lowered.

  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 release force (F) of the release film in the present invention is preferably in the range of 20 to 200 mN / cm, more preferably in the range of 20 to 100 mN / cm. When the peeling force (F) is less than 20 mN / cm, the peeling force becomes too light, and there may be a problem such as easy peeling in a scene where it is not necessary to peel. On the other hand, when the peeling force (F) exceeds 200 mN / cm, the peeling force becomes too heavy, causing problems such as deformation of the adhesive during peeling or adhesion of the adhesive to the release film side. There is a case.

  ADVANTAGE OF THE INVENTION According to this invention, the release point film for polarizing plates in which there are few bright spots of a film as much as possible, and a foreign material inspection with higher precision can be provided can be provided, and the industrial value of this invention 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. In the examples and comparative examples, “parts” means “parts by weight”. 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) Measurement of Ra It measured according to JIS B0601-1994 using the surface roughness measuring machine SE3500 type | mold by Kosaka Laboratory. The measurement length was 2.5 mm.

(6) Visual inspection property under reflected light The inspector visually observed the polarizing plate with a release film under the reflection of a fluorescent lamp, and the visual inspection property under reflected light was evaluated according to the following criteria. 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>
○: Good inspectability (practical level)
×: Poor inspection property (practical problem level)

(7) 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. An inspector visually observed the polarizing plate for inspection, and evaluated whether or not a foreign substance 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.
<Criteria>
○: Good foreign body recognition (a level that is practically acceptable)
X: Poor recognition of foreign matter

(8) Evaluation of peeling force (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 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.

(9) Release characteristics The release characteristics were evaluated from the situation when the release film was peeled off from the polarizing plate with the release film.
<Releasing properties classification criteria>
○: The release film is peeled off beautifully, and the phenomenon that the adhesive adheres to the release layer is not observed.
Δ: The release film is peeled off, but the adhesive adheres to the release layer when peeled at a high speed. ×: The adhesive adheres to the release film. It is a level that can be used without any problems.

(10) Flatness evaluation of release film The flatness of the film was visually observed under a fluorescent lamp in a state where the sample film was suspended from the wall, and the determination was made according to the following criteria.
<Criteria>
○: Thermal wrinkles cannot be confirmed even when viewed at an oblique angle of 45 degrees with respect to the film surface (practically problematic level)
X: The presence of heat wrinkles can be confirmed when viewed from the front of the film surface (practically problematic level)

(11) Comprehensive evaluation The sample film was comprehensively evaluated according to the following criteria.
<Criteria>
○: Visual inspection, foreign object recognition, release characteristics, flatness are all “○”.
×: At least one item among the visual inspection property, foreign object recognition property, release property, and flatness is “×”.
Examples 1-6 and Comparative Examples 1-5

<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). The intrinsic viscosity of this polyester was 0.63.

<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.

<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.

<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.

<Manufacture of 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 and 2 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, after stretching 2.8 times in the longitudinal direction at 100 ° C., after applying a release agent composed of the following release agent composition so that the coating amount (after drying) is 0.060 g / m 2, After a preheating process in a tenter, the film was stretched 4.9 times at 120 ° C, then heat-treated at 190 ° C for 10 seconds, and then 10% relaxation was applied at 180 ° C in the width direction to obtain a polyester having a width of 3000 mm. Each film was obtained. The total thickness of the obtained film was 38 μm, and the thickness of each layer was 4 μm / 30 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>
Films other than Comparative Example 1 and Comparative Example 4 were coated with the following release agent.
(Releasing agent composition-A)
Curing type silicone resin (Dehesive 430: Asahi Kasei Wacker Silicone) 50% by weight
Curing type silicone resin (Dehesive 440: Asahi Kasei Wacker Silicone) 50% by weight
The resin was diluted with water to prepare a solid concentration of 5% by weight.

(Releasing agent composition-B)
Curing type silicone resin (Silicolease 902: Arakawa Chemical) 99% by weight
Platinum catalyst (Silicolyse 903: Arakawa Chemical) 1% by weight
The above was diluted with water to prepare a solid concentration of 5% by weight.

(Releasing agent composition-C)
Curing type silicone resin (Dehesive 430: Asahi Kasei Wacker Silicone) 30% by weight
Curing type silicone resin (Dehesive 440: Asahi Kasei Wacker Silicone) 30% by weight
Peeling regulator (CRA491: Asahi Kasei Wacker Silicone) 40% by weight
The above was diluted with water to prepare a solid concentration of 5% by weight.

Comparative Example 4
In Example 1, instead of applying the release agent by the coating stretching method, the application amount (after drying) of the release agent having the release agent composition shown below becomes 0.1 g / m ² by offline. Thus, a reverse gravure coating method was applied to obtain a roll-shaped release film under conditions of a dryer temperature of 180 ° C. and a line speed of 30 m / min.
(Releasing agent composition-D)
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

<Manufacture of polarizing plate with release film>
The acrylic adhesive shown below is applied to the polarizing plate so that the thickness after drying is 25 μm, and after passing through a 130 ° C. drying oven in 30 seconds, the release film is bonded, and the adhesive is interposed. Thus, a polarizing plate with a release film in which the release film and the polarizing film were adhered to each other was prepared. The laminating direction of the film was performed so that the width direction of the release film was parallel to the orientation axis of the polarizing film.

(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

※比較例１のフィルムはキズが多く、検査性を判定することができなかった。

* The film of Comparative Example 1 had many scratches, and the testability could not be determined.

  The release film of the present invention can ensure a high degree of accuracy in various inspection methods for polarizing plates, and can be suitably used as a release film for polarizing plates.

Claims (1)

For a polarizing plate characterized by having a release layer provided on one side of a polyester film having a surface roughness (Ra) of 11 to 25 nm and an image clarity value of 90% or more by a coating stretching method Release film.