JP2011213025A - Release film for base material-less double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film for base material-less double-sided adhesive sheet which is suitable for, e.g., manufacturing a liquid crystal constituent member of a touch panel, a liquid crystal polarizing plate, a retardation plate and so forth, for manufacturing a PDP constituent member, manufacturing an organic EL constituent member, manufacturing various kinds of display constituent members, and for various kinds of optical applications, the adhesive sheet using the release film with very little oligomer deposition on the film surface, and including little foreign matter caused by the oligomer on the adhesive layer, when the base material-less double-sided adhesive sheet is used for optical applications.SOLUTION: The release film is attached to both surfaces of the adhesive layer in use. The release film is configured by sequentially laminating an anchor layer having a thickness of 8 to 120 nm and a release agent layer, on a biaxially oriented polyester film. The amount of oligomer on the surface of the release agent layer when heated at 180°C for 10 minutes is 2.0 mg/mor lower for the release film for base material-less double-sided adhesive sheet.

Description

  The present invention relates to a release film used for a substrate-less double-sided pressure-sensitive adhesive sheet, and particularly relates to a release film that minimizes the amount of oligomer deposition on the surface of a release agent layer, and includes, for example, touch panels, liquid crystal displays (hereinafter referred to as LCDs). Substrate-less double-sided pressure-sensitive adhesive sheet used for optical applications such as plasma display panels (hereinafter sometimes abbreviated as PDP) and organic electroluminescence (hereinafter sometimes abbreviated as organic EL). The present invention relates to a release film suitable for use.

  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, when using a polarizing plate on one side of a substrate-less double-sided adhesive as the LCD member and a release film on the opposite side, it is easy to detect defects such as foreign matter when inspecting with the crossed Nicols method A proposal has been made to reduce the inclination of the main axis of orientation of a biaxially oriented polyester film used for a release film. (For example, JP2009-220696)
Thus, when using the substrate-less double-sided pressure-sensitive adhesive sheet for optical applications, not only the substrate-less double-sided pressure-sensitive adhesive sheet, but also the release film used for it is more problematic than ever with defects such as foreign matter. It has become.

JP 2009-220296 A Japanese Patent Laid-Open No. 6-16941 JP-A-7-3215

  The present invention has been made in view of the above circumstances, and the problem to be solved is that when used for optical applications, a pressure-sensitive adhesive sheet using a release film with a very small amount of oligomer precipitation on the film surface is the pressure-sensitive adhesive layer. There are few foreign substances due to oligomers. For example, for manufacturing various liquid crystal components such as touch panels, liquid crystal polarizing plates, and retardation plates, for manufacturing PDP components, for manufacturing organic EL components, etc. The present invention provides a release film for a substrate-less double-sided pressure-sensitive adhesive sheet suitable for applications and the like.

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

That is, the gist of the present invention is a release film that is used by being bonded to both surfaces of an adhesive layer, and the release film is formed on a biaxially oriented polyester film and an anchor layer having a thickness of 8 to 120 nm. The substrate-less double-sided pressure-sensitive adhesive having a structure in which the agent layer is sequentially laminated and the amount of oligomer on the surface of the release agent layer when heated at 180 ° C. for 10 minutes is 2.0 mg / m ² or less It exists in the release film for sheets.

  In the release film of the present invention, even when the oligomer contained in the polyester of the base material is heated in the manufacturing process of each member, oligomer precipitation on the surface of the release agent layer is suppressed, and the optical application For the substrate-less double-sided pressure-sensitive adhesive sheet used in the invention, foreign matters due to oligomers can be reduced, and the industrial value of the present invention is high.

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the release film in the present invention may have a single-layer structure or a laminated structure. For example, the polyester film may have a four-layer or a three-layer structure as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. It may be a multilayer having more than that, and is not particularly limited.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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 polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester that is usually 60 mol% or more, preferably 80 mol% or more of polyethylene terephthalate or the like which is an ethylene terephthalate unit.

  In the present invention, it is preferable to blend particles in the polyester layer mainly for the purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, during the polyester production process, it is possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed. On the other hand, the shape of the particles to be used is not particularly limited. Either a rod shape or a flat shape may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-1 micrometer. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and There may be a problem when a release agent layer is applied in the process.

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

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage of producing the polyester constituting each layer, but preferably a polycondensation reaction may be carried out after the esterification stage or after the transesterification reaction.

  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.

  The thickness of the release film of the present invention is not particularly limited as long as it can be formed as a film and can be processed as a release film, but is usually 10 to 100 μm, preferably 15 to 50 μm. Range. If the film thickness is less than 10 μm, the film may not be elastic, and trouble may occur in the process of peeling the release film. If the film thickness exceeds 100 μm, the manufacturing cost will increase.

  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.

  First, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, the extending | stretching temperature orthogonal to the 1st step | paragraph extending | stretching direction is 70-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. 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.

  The simultaneous biaxial stretching method can also be adopted for the production of the polyester film in the present invention. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows: The area magnification is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Furthermore, a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can.

  Next, formation of the anchor layer constituting the release film in the present invention will be described. Regarding the anchor layer, the above-described coating and stretching method (in-line coating) may be used, so-called off-line coating that is applied outside the system on a once produced film may be employed, and any method may be employed. .

  The present invention imparts oligomer sealing ability by containing an organic compound containing one or more metal elements selected from aluminum, titanium and zirconium in the anchor layer. Only one kind of these metal organic compounds may be used, or two or more kinds may be appropriately mixed and used.

  Specific examples of the organic compound having an aluminum element include aluminum tris (acetylacetonate), aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum di-n-butoxide monoethylacetoacetate, aluminum di -Iso-propoxide monomethyl acetoacetate and the like are exemplified.

  Specific examples of the organic compound having a titanium element include, for example, titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate; titanium acetylacetonate, Examples thereof include titanium chelates such as titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamate, and titanium ethylacetoacetate.

  Specific examples of the organic compound having a zirconium element include, for example, zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate and the like.

  Among them, it is preferable to use an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium, more preferably a chelate structure, particularly in that the oligomer precipitation preventing performance is good. Organic compounds are preferred. It is also described in detail in the “Crosslinking agent handbook” (Yamashita Shinzo, Kaneko East Assistant Editor, Taiseisha, 1990 edition).

  The anchor layer constituting the release film in the present invention is required to use an organosilicon compound in combination in order to improve the oligomer precipitation preventing property and the coating film adhesion between the release agent layer and the polyester film. The organic silicon compound is preferably represented by the following general formula (1).

Si (X) _d (Y) _e (R ¹ ) _f (1)
(In the above formula, X is an organic group having at least one selected from an epoxy group, a mercapto group, a (meth) acryloyl group, an alkenyl group, a haloalkyl group and an amino group, R ¹ is a monovalent hydrocarbon group, and 1 to 10 carbon atoms, Y is a hydrolyzable group, d is an integer of 1 or 2, e is an integer of 2 or 3, f is an integer of 0 or 1, and d + e + f = 4 )
The organosilicon compound represented by the general formula (1) has two hydrolyzable groups Y (D unit source) or three (T unit) capable of forming a siloxane bond by hydrolysis / condensation reaction. Source) can be used. In the general formula (1), R ¹ is particularly preferably a methyl group, an ethyl group, or a propyl group. As the hydrolyzable group Y, conventionally known ones can be used, and the following can be exemplified. Methoxy group, ethoxy group, butoxy group, isopropenoxy group, acetoxy group, butanoxime group, amino group and the like. These hydrolyzable groups may be used alone or in combination. The application of a methoxy group or an ethoxy group is particularly preferable because it can impart good storage stability to the coating material and has suitable hydrolyzability.

  In the present invention, as the organosilicon compound contained in the anchor layer, conventionally known compounds can be used, specifically, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycid. Xylpropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, 5-hexenyltrimethoxysilane, p-styryltrimethoxysilane, trifluoropropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiisopropenoxysilane Etc. It can be.

  In the present invention, it is an essential requirement to use a catalyst in combination with the anchor layer constituting the release film for the purpose of promoting hydrolysis and condensation reaction. Specific examples of the catalyst include organic acids such as acetic acid, butyric acid, maleic acid and citric acid, inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid, basic compounds such as triethylamine, tetrabutyl titanate, dibutyltin dilaurate, Organometallic salts such as dibutyltin diacetate, dibutyltin dioctate, dibutyltin diolate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (triethoxysiloxy) tin, dibutyltin benzylmalate, etc., KF, NH4 F Fluorine element-containing compounds such as The said catalyst may be used individually or may use 2 or more types together. Among these, organometallic salts are particularly preferable from the viewpoint of good coating film durability, and more preferably a tin catalyst is used from the viewpoint of long-lasting catalytic activity.

  Further, inorganic particles may be contained for the purpose of improving the anchoring property and slipperiness of the anchor layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

  Moreover, an antifoamer, a coating property improving agent, a thickener, an organic lubricant, organic polymer particles, an antioxidant, a UV absorber foaming agent, a dye, and the like may be contained as necessary.

  In the range not exceeding the gist of the present invention, only one type of organic solvent may be used for the purpose of improving dispersibility, improving film forming property, etc., and two or more types may be used as appropriate.

  The application amount (after drying) of the anchor layer provided on the polyester film constituting the release film in the present invention is in the range of 8 to 120 nm, preferably 10 to 50 nm. When the coating amount is less than 10 nm, the uniformity of coating thickness is insufficient, and the amount of oligomer precipitated from the anchor layer surface after heat treatment increases. On the other hand, when the thickness exceeds 100 nm, the coating film is brittle even if the oligomer sealing performance is obtained, and scratches are likely to occur in the drying step and the winding step after coating.

  In the present invention, the anchor layer can be provided by a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like. As for the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979.

  In the present invention, regarding the curing conditions when forming the anchor layer on the polyester film, it is necessary to heat-treat at 120 ° C. or higher, preferably 120 to 200 ° C. for 3 to 40 seconds, more preferably 120 to 160 ° C. Heat treatment is performed for 3 to 40 seconds as a guide. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. If the heat treatment is not performed at 120 ° C. or higher, the amount of oligomers deposited is increased, and the anchor layer is not sufficiently cured, resulting in a large fluctuation in the peeling force of the release agent layer.

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

  The release agent layer constituting the release film in the present invention refers to a layer having releasability, and specifically, the peeling force (F) between the acrylic pressure-sensitive adhesive tape and the release agent layer is 5 to 5. 500 mN / cm is preferable for the use of the present invention.

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

  Moreover, it is preferable that the release agent layer which comprises the release film in this invention contains a curable silicone resin in order to make mold release property favorable. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

  As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet curable type, an electron beam curable type, and a solventless type can be used. Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62 -7213, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, manufactured by Dow Corning Asia Co., Ltd. YSR-3022, TPR-6700, TPR-6720, manufactured by GE Toshiba Silicone Corporation , TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A277_ , XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, manufactured by Dow Corning Toray Co., Ltd. SRX357, SRX211, SD7220, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, etc. BY24-452 are exemplified. Further, a release control agent may be used in combination in order to adjust the release property of the release agent layer.

  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 agent 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 agent layer on the polyester film are not particularly limited. When the release agent layer is provided by off-line coating, it is usually 3 to 40 at 120 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. In addition, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation.

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

  In the present invention, when a release agent layer is provided on the anchor layer, the film may be wound once after the anchor layer is provided, and the release agent layer may be provided again, or after the anchor layer is provided, The release agent layer may be provided on the anchor layer, and any method may be adopted.

After the release film of the present invention is heat-treated (180 ° C., 10 minutes), the oligomer amount (OL) extracted from the release agent layer surface with dimethylformamide needs to be 2.0 mg / m ² or less, Preferably it is 1.0 mg / m ² or less, more preferably 0.7 mg / m ² or less. When the OL exceeds 2.0 mg / m ² , for example, when the liquid crystal component is manufactured, the adhesive layer is used for protecting the adhesive layer, the transparency of the adhesive is lowered, the adhesive strength of the adhesive layer is reduced, or optical evaluation is performed. There may be problems such as causing trouble in the accompanying inspection process.

  In the release film according to the present invention, the amount of metal element contained in the anchor layer is preferably 0.5 kcps or more, and more preferably 1.0 kcps or more so that OL satisfies the above range. When the amount of the metal element is less than 0.5 kcps, the desired oligomer sealing performance may not be obtained.

  In the present invention, “oligomer” is defined as a cyclic trimer of low molecular weight substances that crystallize and precipitate on the film surface after heat treatment.

  In the present invention, the substrate-less double-sided pressure-sensitive adhesive sheet is constituted by laminating release films on both sides of the pressure-sensitive adhesive layer.

  One of the release films (hereinafter sometimes referred to as a first release film) is preferably a so-called light release sheet.

  The other release film (hereinafter sometimes referred to as a second release film), that is, a so-called heavy release sheet is preferable.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, an acrylic pressure-sensitive adhesive is usually used. The acrylic pressure-sensitive adhesive is composed mainly of an acrylic copolymer obtained by copolymerizing a functional group-containing monomer and another monomer such as an acrylic ester or methacrylic ester, and if necessary, a solvent , A crosslinking agent, a tackifier, a filler, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber and the like may be further contained.

  Examples of the functional group-containing monomer include carboxyl group-containing monomers such as acrylic acid and methacrylic acid. The functional group-containing monomer preferably includes 0.3 to 5.0% by mass as a monomer unit based on the whole monomer constituting the acrylic copolymer (100% by mass).

  By containing functional groups, acrylic copolymers can adjust cohesion by reaction with cross-linking agents, prevent sticking of adhesives from the base material, and improve adhesion and heat resistance. Can be made. There is no restriction | limiting in particular as a crosslinking agent used for an adhesive, It uses suitably selecting from what was conventionally used in the acrylic adhesive conventionally, for example, a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin , Dialdehydes, methylol polymers, aziridine compounds, metal chelate compounds, metal alkoxides, metal salts and the like, preferably polyisocyanate compounds are used.

  The release film of the present invention is formed by sequentially providing an anchor layer and a release agent layer on a biaxially oriented polyester film. In the case of not having such a configuration, in the production process of the substrate-less double-sided pressure-sensitive adhesive sheet, the oligomer deposited from the polyester film migrates to the release film surface, and further, the oligomer migrates from the release film surface to the pressure-sensitive adhesive sheet and migrated. Since the oligomer becomes a foreign substance and becomes a defect in the final product, it is not preferable.

  The base material-less double-sided pressure-sensitive adhesive sheet is, for example, coated on the second release film release agent layer and then dried to form an adhesive layer, and then on the release agent layer. Produced by laminating the first release film, but when the anchor layer 24 is not provided, in the heating process of this production, from the biaxially oriented polyester film that is the substrate of the second release film The precipitated oligomer migrates to the surface of the release film, and the oligomer migrated from the release film surface to the pressure-sensitive adhesive sheet becomes a foreign substance and becomes a defect in the final product, which is not preferable.

  Further, when the baseless double-sided pressure-sensitive adhesive sheet is produced by a method in which the first release film is heated, if the anchor layer is not provided on the first release film, the same phenomenon as the second release film 32 Is not preferable.

  The peel strength of the first release film corresponding to the light release side with respect to the pressure-sensitive adhesive layer is preferably 3 to 50 mN / cm, more preferably 5 to 25 mN / cm.

  By keeping the peel strength of the first release film low, even if the second release film is lowered, the difference in peel strength between the two release films can be increased.

  In addition, by setting the peeling force of the first release film to a certain value or more, the first release film may be unexpectedly peeled off from the adhesive layer before use, or the first release film may be lifted from the adhesive layer. Is prevented.

  The peeling force with respect to the pressure-sensitive adhesive layer of the second release film corresponding to the heavy peeling side is preferably 10 to 100 mN / cm, more preferably 15 to 50 mN / cm.

  By suppressing the peeling force of the second release film to a low level, it is possible to prevent the adhesive remaining on the second release film, zipping, and the like that occur when the second release film 2 is peeled off.

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

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

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

(3) Heat treatment of film A4 size Kent paper and polyester film to be heat treated are combined. At that time, clip the four corners with a gem clip or the like so that the surface with the coating layer is on the outside, and stop the Kent paper and the polyester film. Under a nitrogen atmosphere, the polyester film is left in an oven at 180 ° C. for 10 minutes to perform heat treatment.

(4) Amount of oligomer on film surface after heat treatment The upper part is opened and the polyester film after the heat treatment is folded so that the area of the bottom is 250 cm 2 to create a square box. When the coating layer is provided, the coating layer surface is set to the inside. Next, 10 ml of DMF is put in the box prepared by the above method, and the DMF is recovered after being left for 3 minutes. The recovered DMF is supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer in DMF, and this value is divided by the film area in contact with DMF to obtain the amount of oligomer on the film surface (mg / m ² ). To do. 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 an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. The concentration of the standard sample is preferably in the range of 0.001 mg / ml to 0.01 mg / ml. The conditions of 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

(5) Evaluation of peel force (F) of release film After attaching one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the release agent layer of the sample film, the size is 50 mm × 300 mm. After cutting, 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.

(6) Practical properties <Roll contamination status>
When the release film was produced, each roll of the production apparatus was visually observed to evaluate the state of contamination of the roll with the oligomer.
○: No deposits are observed on the roll surface after manufacture Δ: Slight deposits are observed on the roll surface after manufacture, but there is no problem in manufacturing ×: Deposits are observed on the roll surface after manufacture , Need roll cleaning

<Foreign matter inspection>
The substrate-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides was observed and evaluated based on the detection of foreign matter.
○: Foreign matter is not detected, and the quality is sufficient for optical use. △: Foreign matter is detected, but there is no practical problem. ×: Many foreign matters are detected, which is inappropriate for optical use. Limited use

Example 1:
<Manufacture of polyester film>
Polyester as a raw material is supplied to an extruder equipped with a vent, melted and extruded at 290 ° C., and then cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method to a thickness of about 550 μm. An amorphous film was obtained. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., stretched 3.9 times in the transverse direction at 100 ° C., and heat treated at 210 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm.

<Manufacture of release film>
The anchor layer which consists of the following composition is apply | coated to the obtained polyester film 1 (a coating amount is described in a table | surface), it is made to dry, and a coating amount becomes 0.1 g / m < ² > (after drying) after that. Thus, a first release film and a second release film were obtained. The properties of the obtained release film are shown in Table 1 below.

-Anchor composition Organic compound having aluminum element (ALCH-TR) 20 parts Organosilicon compound (KBM-303) 10 parts Curing agent (PS-8S: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 part MEK / toluene mixed solvent (mixing ratio is 4: 1) 1400 parts

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

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

<Manufacture of substrate-less double-sided PSA sheet>
On the release agent layer of the obtained second release film, the acrylic pressure-sensitive adhesive solution was applied using an applicator so that the film thickness after drying was 25 μm. The adhesive layer was formed by drying at 120 ° C. for 1 minute. The acrylic pressure-sensitive adhesive solution was prepared by adding polyisocyanate-based crosslinking to 100 parts by mass of a copolymer solution (solvent: toluene, solid content concentration: 40% by mass) having a monomer-based mass ratio of butyl acrylate and acrylic acid of 99: 1. It was obtained by adding 1 part by weight of an agent (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BHS8515”, solid content concentration 37.5% by mass). Subsequently, the release agent layer and adhesive layer of the 1st release film were bonded together, and the base material-less double-sided adhesive sheet of Example 1 was obtained.

Examples 2-3:
A substrate-less double-sided pressure-sensitive adhesive sheet of Example 2 was obtained in the same manner as Example 1 except that the coating thickness was changed.

Comparative Examples 1-2:
A substrate-less double-sided PSA sheet was obtained in the same manner as in Example 1 except that the coating thickness was changed. The comparative example 3 obtained the base material-less double-sided adhesive sheet like Example 1 except changing heat processing temperature. The comparative example 4 obtained the base material-less double-sided adhesive sheet like Example 1 except not providing an anchor layer.

  The evaluation results of the films obtained in each example and comparative example are summarized in the following table.

  The release film of the present invention can be suitably used as, for example, a release film for a substrate-less double-sided pressure-sensitive adhesive sheet used for optics.

Claims (2)

A release film that is used by being bonded to both sides of an adhesive layer, and the release film is formed by sequentially laminating an anchor layer and a release agent layer having a thickness of 8 to 120 nm on a biaxially oriented polyester film. A release film for a substrate-less double-sided pressure-sensitive adhesive sheet, characterized in that the amount of oligomer on the surface of the release agent layer when heated at 180 ° C. for 10 minutes is 2.0 mg / m ² or less. The anchor layer is formed by applying and drying a coating liquid containing an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium, an organic silicon compound, and a catalyst. The release film for base-material-free double-sided adhesive sheets of Claim 12.