JP2012025030A - Polyester film for base material-less double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a base material-less double-sided adhesive sheet which can easily detect a fault during inspection and can appropriately be used in optical applications, for example, a touch panel, a liquid crystal deflector, a retardation plate, etc.SOLUTION: In the polyester film for the base material-less double-sided adhesive sheet which is a release film having a coating layer obtained by coating one side of a polyester film with a coating liquid containing polyvinyl alcohol and a silicone release layer containing 0.5-5.0 wt.% of one or more kinds of a transition metal catalyst on the coating layer, the MOR value of the release film is 1.5-3.0.

Description

  The present invention relates to a polyester film for a baseless double-sided pressure-sensitive adhesive sheet for optical applications.

  Conventionally, various pressure-sensitive adhesive sheets for surface bonding between objects are known, and a base-less double-sided pressure-sensitive adhesive sheet is known as one of pressure-sensitive adhesive sheets. The substrate-less double-sided pressure-sensitive adhesive sheet is configured by laminating a light release sheet having a relatively low peeling force and a heavy release sheet having a relatively high peeling force on both sides of the pressure-sensitive adhesive layer, and removing the double-sided release sheet. The latter is a double-sided pressure-sensitive adhesive sheet that only has a pressure-sensitive adhesive layer that does not have a supporting substrate. The substrate-less double-sided PSA sheet is first peeled off from the light release sheet, and one side of the exposed PSA layer is bonded to the object surface. The other side of the layer is bonded to a different object surface, thereby surface bonding between the objects.

  In recent years, the use of a baseless double-sided pressure-sensitive adhesive sheet has been spreading, and is also used for members for various optical applications. For example, as the LCD member, peel off the release film with the lighter peeling force of the base-less double-sided pressure-sensitive adhesive sheet, paste the polarizing plate on the surface, and release the heavy release force on the opposite side. In order to facilitate the detection of defects such as foreign matter in the remaining release film during inspection using the crossed Nicols method, a proposal to reduce the tilt of the orientation axis of the biaxially oriented polyester film used for the release film (For example, Patent Document 1).

  As described above, when the substrate-less double-sided pressure-sensitive adhesive sheet is used for optical applications, not only the substrate-less double-sided pressure-sensitive adhesive sheet but also the release film used for it is more important than ever for defects such as foreign matters. ing.

  Further, as one of the causes of the generation of foreign matters, oligomers contained in the polyester film (hereinafter sometimes abbreviated as OL) are considered. OL, which is considered to be a low molecular weight sublimate of polyester, is deposited on the surface of the film within the production process and adheres to a roll or the like that comes into contact with the film to become a foreign matter. Moreover, in order to reduce a foreign material, although the operation | work which removes the oligomer adhering to a roll is performed, the problem that production efficiency worsens is also mentioned.

Japanese Patent Application No. 2010-121101 JP 2009-220296 A Japanese Patent Application No. 2010-132561

  The present invention has been made in view of the above circumstances, and the problem to be solved is when the substrate-less double-sided pressure-sensitive adhesive sheet is used in optical applications, for example, a touch panel, a liquid crystal deflecting plate, a retardation plate, etc., during optical inspection. Inexpensive polyester film for double-sided pressure-sensitive adhesive sheets that eliminates problems such as productivity and cost, and has a difference in peel strength between release films when bonded to pressure-sensitive adhesives. 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 is to have a coating layer obtained by coating a coating solution containing polyvinyl alcohol on one side of a polyester film, and at least one transition metal catalyst is added to the coating layer. A release film having a silicone-based release layer containing 5 to 5.0% by weight, wherein the release film has a MOR value of 1.5 to 3.0. It exists in the polyester film for sheets.

  According to the present invention, since it is possible to provide a polyester film for a base-less double-sided pressure-sensitive adhesive sheet that is easy to perform optical inspection, inexpensive, and has high productivity, its 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 about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 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 coating layer for the purpose of OL sealing which comprises the polyester film of this invention is demonstrated. Regarding the coating layer, it may be provided by so-called in-line coating, which treats the film surface during the stretching process of the polyester film, or may be applied outside the system on the film once produced, so-called off-line coating may be adopted, You 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 this invention, although the layer which prevents precipitation of an oligomer is formed by application | coating on the single side | surface of a film, it is necessary to form the said application layer with the coating liquid 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. When the content of polyvinyl alcohol is less than 10% by weight, the oligomer sealing effect 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.

  A water-soluble or water-dispersible binder resin other than the above-described polyvinyl alcohol may be used in combination in the oligomer precipitation preventing layer in the film of the present invention, 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.

  In the OL sealing layer of the polyester film of the present invention, the binder resin and the crosslinking agent are preferably blended in an arbitrary ratio, so that the coating layer can form a barrier layer densely, thereby suppressing OL. . For this reason, there is an effect that OL from the polyester film is not attached to the adhesive as much as possible and is not produced in the previous processing step. Accordingly, the OL sealing layer of the polyester film of the present invention preferably has a double-sided structure, and is applied to at least one side depending on the application.

  In the present invention, the release layer formed on the coating 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 a release layer on the polyester film, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, or the like can be used. The coating amount of the release layer in the present invention is usually in the range of 0.01-1 g / m2.

  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, and the polyester film may be subjected to corona treatment, plasma treatment, etc. A surface treatment may be applied.

  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 polyester film for substrate-less double-sided pressure-sensitive adhesive sheet of the present invention, in order to reduce the generation of foreign matter and light interference color by optical inspection of the process, etc., the optimum MOR_C value obtained by measuring the release film with a microwave molecular orientation meter Conversion is very important.

  The MOR_C value of the release film of the present invention is 1.5 to 3.0, preferably 1.8 to 2.7, and more preferably 2.1 to 2.4. When the MOR_C value is larger than 3.0, the release layer is not uniform, and in optical inspection, the light interference color is easily visible. When the MOR_C value is smaller than 1.5, there is a problem that the production yield of the release film itself is deteriorated.

  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 anchor layer surface In advance, an unheated release film is heated in air at 180 ° C. for 10 minutes. 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) MOR_C value measurement by microwave molecular orientation meter of polyester film Using a microwave type molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd., the MOR_C value was determined from the transmission microwave intensity pattern. Judgment is based on the following criteria.
○: 2.0 to 2.5
Δ: 1.5 to 1.9, or 2.6 to 3.0
X: Lower than 1.5% or higher than 3.0

(9) Practical characteristics <Visual inspection under crossed Nicols>
Taking the polarizing plate inspection into consideration, the width direction of the release film obtained by applying a release agent on the film and having a dryer temperature of 120 ° C. and a line speed of 30 m / min is parallel to the alignment axis of the polarizing film. In this way, the release film is closely attached to the polarizing film through an adhesive to form a polarizing plate, and the polarizing plate for inspection is superimposed on the attached release film so that the orientation axis is orthogonal to the film width direction. White light was irradiated from the plate side, visually observed from a polarizing plate for inspection, and visual inspection property under crossed Nicols was evaluated according to the following criteria. In the measurement, A4 size samples were cut out from a total of three locations in the center and both ends in the width direction of the obtained film.
"Criteria"
○: Inspection is possible without optical interference. Δ: Optical interference is present but inspection is possible. ×: Optical interference is present and inspection is not possible. ○ and Δ are at a level where there is no problem in actual use.

<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

(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 produced, it can be supplied as a product. Further, the OL amount is less than 1.0 mg / m ² .
Δ: Productivity is good and the frequency of defects is low. Further, the OL amount is less than 1.0 mg / m ² .
X: Productivity is poor. Many troubles occur. The OL amount is more than 1.0 mg / m ² .

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

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

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

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

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

Example 1:
<Manufacture of polyester film>
As a raw material for the surface layer, 70% by weight of polyester (e) and 30% by weight of polyester (b) are mixed. As a raw material for the intermediate layer, 84% by weight of polyester (a) and 16% by weight of polyester (b) are mixed. Each was supplied to an extruder with a vent and melt-extruded at 290 ° C., and then cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., and then the following coating agent was applied to one side of the longitudinally stretched film so that the coating amount (after drying) was 0.03 g / m ² . After that, after being guided to a tenter, subjected to a preheating step at 120 ° C. in the transverse direction at a temperature of 120 ° C. and subjected to a transverse stretching of 5.1 times at 120 ° C., heat treatment was performed at 220 ° C. for 10 seconds, and then at 180 ° C. 4% relaxation was added to a master roll having a width of 4000 mm. A slit was made from a position of 1400 mm from the end of the master roll, and the core roll was wound up 1000 m to obtain a polyester film. The total thickness of the obtained film was 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 release agent composed of release agent composition-A shown below was applied to the obtained polyester film 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. A release film having a roll peel strength of 21 mN / cm under the conditions of ° C and a line speed of 30 m / min, a MOR_C value of the polyester film of 2.3, and an OL amount of 0.82 mg / m ² was obtained.
<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)

  For the obtained polyester film, a polarizing plate was prepared by the following method, and visual inspection properties and peeling properties were evaluated under crossed Nicols. The obtained release film could be inspected without optical interference, and the polarizing plate was peeled off cleanly, and the phenomenon that the adhesive adhered to the release layer was not observed.

<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

Examples 2-5:
In Example 1, the polyester film was produced in the same manner as in Example 1 except that the draw ratio and film thickness during the production of the polyester film were changed or the transition metal catalyst content of the release agent composition was changed. Got. The obtained results are summarized in Table 1 below.

Comparative Examples 1-4:
In Example 1, the polyester film was produced in the same manner as in Example 1 except that the draw ratio and film thickness during the production of the polyester film were changed or the transition metal catalyst content of the release agent composition was changed. Got. The results obtained are summarized in Table 2 below.

※１）コストが高いため、生産性に問題がある。

* 1) There is a problem in productivity due to high cost.

  The polyester film of the present invention can be suitably used as a separator polyester film that is highly productive and can be easily subjected to process optical inspection in the field of substrate-less double-sided pressure-sensitive adhesive sheets in optical applications where demand is great.

Claims (1)

It has a coating layer obtained by coating a coating solution containing polyvinyl alcohol on one side of a polyester film, and 0.5 to 5.0% by weight of at least one transition metal catalyst on the coating layer. A polyester film for a substrate-less double-sided pressure-sensitive adhesive sheet, comprising a release film having a silicone-based release layer, wherein the MOR value of the release film is 1.5 to 3.0.