JP2012161970A - Mold release polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release polyester film that can be suitably used in polarizing plate applications and the like, and can increase the peeling yield particularly during processing.
SOLUTION: One side of a polyester film has a primer layer obtained by applying a coating solution containing polyvinyl alcohol, the peel strength of the primer layer is 4000 mN / cm or more, and the other side of the polyester film A release polyester film comprising a silicone release layer.
[Selection figure] None

Description

  The present invention relates to a release polyester film suitable for optical use, for example.

  When the release film bonded to the pressure-sensitive adhesive or the polarizing plate is peeled off in a subsequent step, an adhesive tape or the like may be attached to the anti-silicone coating surface of the release film and peeled off from the pressure-sensitive adhesive or the polarizing plate. At that time, due to the compatibility between the release film and the pressure-sensitive adhesive, if the two films are strongly bonded to each other, a peeling failure such as the release film not being peeled off from the pressure-sensitive adhesive or being difficult to peel off may occur. Although it is required to increase the yield in such a peeling process, the current product is still insufficient.

JP 2006-187951 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is an inexpensive release polyester film that can be suitably used for polarizing plate applications and the like, and can increase the peeling yield during processing. It is to provide.

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

  That is, the gist of the present invention includes a primer layer obtained by applying a coating liquid containing polyvinyl alcohol on one side of a polyester film, and the peel strength of the primer layer is 4000 mN / cm or more. It exists in the release polyester film characterized by having a silicone type release layer on the other surface.

  ADVANTAGE OF THE INVENTION According to this invention, the release polyester film which can raise a peeling yield at the time of a process with the release polyester film which is cheap and has high productivity can be provided, The industrial value is high.

  The polyester film referred to in the present invention is a film obtained by stretching a sheet melt-extruded from an extrusion die according to a so-called extrusion method.

The polyester constituting the film refers to a polymer containing an ester group obtained by polycondensation from dicarboxylic acid and diol or from hydroxycarboxylic acid.
Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and diols include ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. Typical examples of such a polymer include polyethylene terephthalate and polyethylene-2,6-naphthalate.

  In the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing the occurrence of scratches in each step. 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, heat-resistant organic particles as 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, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  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. 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 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. When the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted. On the other hand, when the thickness exceeds 3 μm, transparency may be lowered due to the aggregate of the particles when the film is formed, and it is easy to cause breakage, which causes a problem in terms of productivity. There is.

  Furthermore, the content of particles in the polyester 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 a case.

  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 for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  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.

  Although the thickness of the polyester film in this invention will not be specifically limited if it is a range which can be formed into a film as a film, Usually, 10-350 micrometers, Preferably it is the range of 15-100 micrometers.

  Next, although the manufacture example of the polyester film in 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 preferable 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 is 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 90 to 140 ° C., preferably 95 to 120 ° 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 90 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.

  For the production of the polyester film of the present invention, a simultaneous biaxial stretching method can also be employed. 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 90 to 140 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. 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.

  Next, formation of the primer layer which comprises the polyester film of this invention is demonstrated. The primer layer in the present invention refers to an easy-adhesion effect to a pressure-sensitive adhesive such as a general tape, for example, a coating layer containing components such as polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, and acrylate resin. .

  Regarding the coating layer of the polyester film of the present invention, it may be provided by so-called in-line coating, which treats the film surface during the stretching process of the polyester film, or so-called off-line coating applied outside the system on the film once produced. You may employ | adopt and may use both together. In-line coating is preferably used in that it can be applied at the same time as film formation, and thus can be manufactured at low cost, and the thickness of the coating layer can be changed by the draw ratio.

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

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

  In the present invention, the primer layer is formed by coating on one side of the film, and the coating layer is formed by a coating solution containing polyvinyl alcohol.

  The content of the polyvinyl alcohol used in the coating layer is usually 10 to 100% by weight, preferably 20 to 90% by weight, and more preferably 30 to 90% by weight. By including the polyvinyl alcohol component, in addition to the effect of easy adhesion, there is an effect of preventing the precipitation of a cyclic trimer low molecular component called an oligomer from the inside of the polyester, thereby realizing a reduction in foreign matter. If the content of polyvinyl alcohol is less than 10% by weight, the oligomer sealing effect of the polyester film tends to be insufficient.

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

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

  The binder polymer used in the present invention is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). Is defined as a polymer compound having a film forming property of 1000 or more.

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

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

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

  Furthermore, the easily adhesive resin layer of the present invention may contain inert particles for improving the slipperiness of the coating layer, if necessary.

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

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

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

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 80 to 200 ° C. The heat treatment may be performed for 40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

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

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The primer layer of the polyester film of the present invention preferably contains a binder resin and a cross-linking agent in an arbitrary ratio, whereby the coating layer forms a barrier layer densely, and thus OL can be suppressed. For this reason, there is an effect that an oligomer (hereinafter sometimes abbreviated as OL) from a polyester film is not attached to the adhesive as much as possible and is not produced in the previous processing step. Therefore, the layer structure of the primer layer having the OL sealing ability of the polyester film of the present invention is preferably double-sided, and is applied to at least one side depending on the application.

  In the present invention, the release layer formed on the opposite surface of the primer layer is not particularly limited as long as it contains a material having releasability. Among them, the one containing a curable silicone resin is preferable because the releasability is improved. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used.
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.
Further, as described above, a silane compound having an amino group may be added to the release layer.

  In the present invention, as a method for providing the 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 coating amount of the release layer in the present invention is usually in the range of 0.01-1 g / m2.

  Moreover, drying and / or curing (thermal curing, ionizing radiation curing, etc.) of the coating film of the pressure-sensitive adhesive layer or the release layer can be performed individually or simultaneously. When performing simultaneously, it is preferable to carry out at the temperature of 80 degreeC or more. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. When the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is not completely cured, and the coating film tends to fall off, which is not preferable.

  In order to make the release layer of the polyester film in the present invention clean and strong, a transition metal catalyst is used. The transition metal catalyst content in the release layer is 0.5 to 5.0% by weight, preferably 1.5 to 4.0% by weight. When the content of the transition metal catalyst in the coating layer is lower than 0.5% by weight, there may be a problem such as deterioration of the surface condition due to insufficient peeling force or insufficient curing reaction in the coating layer. On the other hand, if the content of the transition metal catalyst in the coating layer exceeds 5.0% by weight, the cost is increased, the reactivity is increased, and gel defects are generated. End up.

  In the release polyester film of the present invention, the peel strength of the primer layer is considered as an index of tape adhesion, and one side of a double-sided adhesive tape (“Nitto Denko“ No. 502 ”) is attached to the primer layer surface of the sample film. It shows the peel force measured after 180 ° peeling under conditions of a tensile speed of 300 mm / min after being left at room temperature for 1 hour.

  The peeling force of the primer layer of the release film of the present invention is 4000 mN / cm or more, preferably 4050 mN / cm or more, more preferably 4100 mN / cm or more. If it is less than 4000 mN / cm, problems such as occurrence of zipping or occurrence of a phenomenon that is difficult to peel off may occur, resulting in poor production yield.

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

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

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

(3) Measurement of transmittance of polyester film According to JIS-K7105, the total light transmittance of the polyester film was measured with an integrating sphere turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Judgment is based on the following criteria.

(4) Haze (turbidity) measurement of polyester film The total light transmittance of the polyester film was measured with an integrating sphere turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K7105. Judgment is based on the following criteria.

(5) Measurement of heat shrinkage rate of polyester film The polyester film was sampled at an arbitrary length L (cm) in the longitudinal direction (hereinafter abbreviated as MD) and the lateral width direction (hereinafter abbreviated as TD). To do. Subsequently, the sample is heated in an oven at 160 ° C. for 5 minutes, and the sample is taken out of the oven and the length l (cm) is measured. This operation is performed three times, and the average value is adopted as the value of the heat shrinkage rate. The heat shrinkage rate can be calculated by the following formula.
Heat shrinkage (%) = {(L−l) / L} × 100

(6) Evaluation of release film release force (F) After attaching one side of a double-sided adhesive tape (Nitto Denko "No. 502") to the release layer surface of the sample film, cut into a size of 50 mm x 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.

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

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

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

(8) Evaluation of Adhesiveness of Primer Layer with Adhesive After applying one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the primer layer of the sample film, it was cut into a size of 50 mm × 300 mm. Thereafter, the peel force after standing at room temperature for 1 hour 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) Practical properties <Release properties>
The release characteristics were evaluated from the situation when the release film was peeled off from the laminated film having the adhesive layer.
○: 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

<Peeling characteristics when a double-sided adhesive tape is applied to the primer layer>
Double-sided adhesive tape (“No. 502” manufactured by Nitto Denko) is attached to the surface of the primer layer opposite to the release film from the laminated film having the adhesive layer, and the tape and the release film are determined according to the situation when the tape is peeled off. The peeling property with the primer layer was evaluated.
○: Peeling without problem, no problem ×: Zipping or phenomenon that is difficult to peel off

(10) Comprehensive evaluation An evaluation is performed in consideration of all film forming properties, productivity, and inspection characteristics. Judgment is based on the following criteria.
○: Even if it is produced, it can be sufficiently supplied as a product, and the yield is high. Δ: Productivity is good and the frequency of defects is low. ×: Productivity is poor. Trouble occurs frequently

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

<Method for producing polyester (b)>
In the production method of polyester (a), 0.2 part of silica particles having an average particle diameter of 2.0 μm dispersed in ethylene glycol was added, and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.61. A polyester (b) having an intrinsic viscosity of 0.61 was obtained using a method similar to the method for producing polyester (a).

Example 1:
<Manufacture of polyester film>
Mixing 77% by weight of polyester (a) and 23% by weight of polyester (b) as the raw material for the surface layer, using polyester (a) as the raw material for the intermediate layer, and supplying each to two vented extruders, After melt extrusion at 290 ° C., an unstretched sheet was obtained by cooling and solidifying on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., and then the following coating agent was coated on one side of the longitudinally stretched film so that the coating amount (after drying) was 0.030 g / m ² . After that, after guiding to a tenter and performing a transverse stretching of 4.3 times at 120 ° C. through a preheating process in the tenter, heat treatment was performed at 220 ° C. for 10 seconds, and then 4% relaxation in the width direction at 180 ° C. In addition, a master roll having a width of 4000 mm was obtained. A slit was made from the position of 1400 mm from the end of this master roll, and 8500 m was wound around the core to obtain a polyester film. The total thickness of the obtained film was 38 μm (layer constitution: surface layer 4 μm / intermediate layer 30 μm / surface layer 4 μm).

In addition, the example of a compound which comprises an application layer is as follows.
(Example compounds)
-Polyvinyl alcohol binder polymer having a saponification degree of 88 mol% and a polymerization degree of 350: A
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant) Binder polymer: B
・ Crosslinking agent Hexamethoxymelamine crosslinking agent: C
・ Particulate colloidal silica (average particle diameter: 70 nm): D
Solid content ratio: A / B / C / D = 30/24/42/4

A reverse gravure coat is applied to the surface layer on the opposite side of the primer layer of the obtained polyester film so that the release agent comprising release agent composition-A shown below is applied (after drying) to 0.1 g / m ^2. It is applied by a method, and the peeling force of the roll-shaped silicone coat surface is 21 mN / cm under the condition of a dryer temperature of 120 ° C. and a line speed of 30 mm / min, and the surface of the roll on the primer layer side under the condition of the line speed of 30 mm / min. The peeling force was 4121 mN / cm.

<Releasing agent composition-A>
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 20 parts Catalyst (PL-50T: manufactured by Shin-Etsu Chemical) 0.3 parts (1.5% by weight)
MEK / toluene mixed solvent (mixing ratio is 1: 1)

  In addition, when the double-sided adhesive tape was attached to the primer layer provided on the opposite side of the release surface of the polyester film and peeled off, the tape peeled off halfway or the tape stopped halfway, and the adhesive of the polarizing plate It did not cause zipping to the agent.

Examples 2-3:
In Example 1, it manufactured like Example 1 except changing the coating amount of a primer layer at the time of polyester film manufacture, and obtained the polyester film. The obtained results are summarized in Table 1 below.

Comparative Examples 1-3:
In Example 1, it manufactured like Example 1 except changing the coating amount of a primer layer at the time of polyester film manufacture, and obtained the polyester film. The results obtained are summarized in Table 2 below.

  The polyester film of the present invention can be suitably used, for example, as a release polyester film having a good production yield in a separator peeling process for pressure-sensitive adhesive processing such as a polarizing plate in demanding optical applications.

Claims (1)

It has a primer layer obtained by applying a coating solution containing polyvinyl alcohol on one side of the polyester film, the peeling force of the primer layer is 4000 mN / cm or more, and the other surface of the polyester film has a silicone release agent. A release polyester film characterized by having a mold layer.