JP2013001817A - Base-less double-sided tacky adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-sided tacky adhesive sheet which allows easy handling and inspection and is suitable for a base-less double-sided tacky adhesive sheet having a thick adhesive layer such as that for an electrostatic capacitance type touch panel.SOLUTION: In the base-less double-sided tacky adhesive sheet, release films are layered respectively on both sides of an adhesive layer. In one of the release films, a release layer formed by a coating stretching method is arranged on one surface of a biaxially oriented polyester film, a film internal haze is ≤0.8%, and the maximum surface roughness (Rt) of the film surface where no release layer is arranged is ≥300 nm.

Description

  The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet, for example, a substrate-less double-sided pressure-sensitive adhesive sheet used for a capacitive touch panel, and is easily inspected and has good handleability in an inspection process involving optical evaluation. The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet.

  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 PSA sheet consists of a laminate structure in which a light release film with a relatively low peel strength and a heavy release film with a relatively high peel strength are laminated on both sides of the adhesive layer. After the removal, the double-sided pressure-sensitive adhesive sheet becomes only the pressure-sensitive adhesive layer having no supporting substrate.

  As a method of using the substrate-less double-sided pressure-sensitive adhesive sheet, first, the light release film is peeled off, and one surface of the exposed pressure-sensitive adhesive layer is adhered to the object surface of the other side to be bonded, and after the adhesion, the heavy release film is further peeled off, A processing step in which the other surface of the exposed pressure-sensitive adhesive layer is bonded to a different object surface, whereby the objects are surface-bonded is exemplified.

  In recent years, the substrate-less double-sided pressure-sensitive adhesive sheet has attracted attention because of its good workability, and its applications are expanding. It is also used for members for various optical applications such as mobile phones. In particular, a capacitive touch panel is rapidly expanding its application as an information terminal by a multi-touch operation in which a screen operation is performed with two fingers. Capacitive touch panels tend to have thicker printing steps than resistive film methods, so a proposal has been made to cover the printing steps by thickening the adhesive layer. In some cases, when the release film is peeled off, a part of the pressure-sensitive adhesive layer adheres to the release film, or air bubbles are mixed into the part of the pressure-sensitive adhesive layer transferred to the release film. Therefore, when using the baseless double-sided pressure-sensitive adhesive sheet for optical applications, not only the baseless double-sided pressure-sensitive adhesive sheet but also the release film to be combined is more severe than before, and release with fewer optical defects such as foreign matter There is a situation where a film is needed.

Japanese Patent Application No. 2010-56884 Japanese Patent Application No. 2010-121101 Japanese Patent Application No. 2010-97765 Japanese Patent Application No. 2010-97925

  The present invention has been made in view of the above circumstances, and the problem to be solved is, for example, suitable for a substrate-less double-sided pressure-sensitive adhesive sheet having a thick adhesive layer, such as for a capacitive touch panel, An object of the present invention is to provide a double-sided pressure-sensitive adhesive sheet imparted with ease of inspection.

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

  That is, the gist of the present invention is a substrate-less double-sided pressure-sensitive adhesive sheet in which release films are laminated on both sides of the pressure-sensitive adhesive layer, and one release film is applied to one side of a biaxially stretched polyester film by a coating stretch method. Substrate-less, characterized in that it has a release layer, the film internal haze is 0.8% or less, and the maximum surface roughness (Rt) of the film surface on which no release layer is provided is 300 nm or more It exists in a double-sided adhesive sheet.

  TECHNICAL FIELD The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet, and has a good releasability and has inspection ease in an inspection process involving optical evaluation. For example, the substrate-less double-sided pressure-sensitive adhesive sheet used for a capacitive touch panel And its industrial value is high.

  In the present invention, the polyester film constituting the release film may have a single-layer structure or a laminated structure. For example, the polyester film has a four-layer structure as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. Or more layers may be used, and there is no particular limitation.

  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. 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 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 polyester film constituting the first and second release films of the present invention is not particularly limited as long as it can be formed as a film, but is usually 25 to 250 μm, preferably 38 to 188 μm, More preferably, it is the range of 50-125 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.

  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 extending | stretching direction of the 1st step is 70-170 degreeC normally, and a draw ratio is 3.0 to 7 times normally, Preferably it is 3.5 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or 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 simultaneously in the machine direction and the width direction in a state of temperature control at 70 to 120 ° C., preferably 80 to 110 ° C. 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 known stretching method such as a screw method, a pantograph method, a linear drive method, or the like can be employed.

  Further, a coating layer is provided by applying a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step. By providing the coating layer on the polyester film by the 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, and a film suitable as a polyester film can be produced.

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

  The release layer constituting the first release film and the second release film in the present invention refers to a layer having releasability, and specifically, the peel force between the acrylic adhesive tape and the release layer. (F) is preferably 5 to 70 mN / cm for the purpose of the present invention, and more preferably 10 to 60 mN / cm. When the peeling force (F) is out of the range, problems such as zipping may occur when the release film is peeled off.

  The release layer constituting the first release film in the present invention is required to be provided on the polyester film by the above-described coating stretching method (in-line coating). The coating stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the first stage of stretching may be completed and the coating treatment may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

  Moreover, it is preferable that the release layer which comprises the release film in this invention contains a curable silicone resin in order to make mold release property favorable. It may be a type mainly composed of a curable silicone resin, 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 long as the gist of the present invention is not impaired. Also good.

  Below, the specific example of the emulsion type curable silicone resin composition which can be used suitably in this invention is shown. Examples include Dehesive 400E, V20 crosslinker system manufactured by Wacker Silicone, X2-7720, X2-7721 crosslinker system manufactured by Dow Corning.

  When an addition-type silicone resin is used as the curable silicone resin, it is preferable to add a curing catalyst to the coating solution in terms of reaction control of the cured film during the film production process. Specifically, platinum-based compound catalysts are suitable, such as platinum fine powder, platinum black, chloroplatinic acid, platinum tetrachloride, chloroplatinic acid olefin complexes, chloroplatinic acid and methylvinylsiloxane complexes, rhodium compounds, palladium. Examples thereof include compounds. The amount of the catalyst added is usually in the range of 0.1 to 500 parts by weight as a platinum-based metal with respect to 10,000 parts by weight of the curable silicone resin.

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

  In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited, and heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as necessary. In addition, as an energy source for hardening by active energy ray irradiation, a well-known apparatus and an energy source can be used.

From coating amount (after drying) a surface of the coating of the release layer, typically 0.005~1g / ^{m 2,} preferably from 0.005 to 0.5 / ^{m 2,} more preferably 0.01 to 0 .2 g / m ² range. If the coating amount (after drying) is less than 0.005 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 1 g / m ² , the coating layer adhesion and curability of the release layer itself may be lowered.

  Regarding the first and second release films in the present invention, coating layers such as an adhesive layer, an antistatic layer, and an oligomer precipitation preventing layer are provided on the surface where no release layer is provided, as long as the gist of the present invention is not impaired. It may be provided.

  Moreover, you may give surface treatments, such as a corona treatment and a plasma treatment, to the polyester film which comprises a 1st and 2nd release film previously.

The film internal haze of the first release film thus obtained needs to be 0.8% or less, preferably 0.6% or less, in order to ensure the ease of inspection in the inspection process involving optical evaluation. is there. When the range exceeds 0.8%, when an inspection with optical evaluation is performed from the obtained first release film side, the first release film must be peeled off at one end during the inspection. Cause a malfunction.
In the present invention, for the first release film, as a specific method for keeping the film internal haze within a predetermined range, for example, in the polyester film constituting the first release film, a laminated polyester film is used. In this case, the particle content of the intermediate layer is suppressed to substantially 0%, and the particle content of the surface layer is increased as much as possible while the polyester layer thickness of the surface layer is made as thin as possible. It is preferable at the point from which the 1st mold release film which has property is obtained.

  In order to satisfy the above range, when the laminated polyester film constituting the first release film is used, the thickness of the outermost polyester layer is preferably 5 μm or less on one side. When the polyester layer thickness is out of the above range, the content of particles in the laminated polyester film is excessively increased, and the film internal haze may exceed 0.8%.

  Furthermore, in the first release film of the present invention, the maximum roughness (Rt) of the film surface on which the release layer is not provided needs to be 300 nm or more in order to ensure the ease of inspection of the substrate-less pressure-sensitive adhesive sheet. Preferably, it is 400 nm or more. When Rt is less than 300 nm, problems such as blocking when the first release film is wound during handling are caused.

  Next, the pressure-sensitive adhesive layer constituting the substrate-less double-sided pressure-sensitive adhesive sheet in the present invention will be described below. The adhesive layer in the present invention means a layer composed of a material having adhesiveness, and conventionally known materials can be used as long as the gist of the present invention is not impaired. As one specific example, the case where an acrylic adhesive is used will be described below.

  In the present invention, the acrylic pressure-sensitive adhesive means a pressure-sensitive adhesive layer containing, as a base polymer, an acrylic polymer formed using an acrylic monomer as an essential monomer component. The acrylic polymer has (meth) acrylic acid alkyl ester and / or (meth) acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as an essential monomer component (more preferably as a main monomer component). ) It is preferably an acrylic polymer to be formed. Further, the acrylic polymer is particularly preferably an acrylic polymer formed using (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as essential monomer components. That is, the pressure-sensitive adhesive layer of the present invention is an acrylic pressure-sensitive adhesive layer formed using (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as essential monomer components. It is particularly preferred.

  In the case of including an alkoxyalkyl acrylate as an essential monomer component for forming an acrylic polymer that is a base polymer in the pressure-sensitive adhesive layer of the present invention, in addition to stress relaxation properties, the anti-foaming resistance of the pressure-sensitive adhesive layer is improved. Therefore, it is preferable. This is because of the effect of the alkoxyl group (alkoxy group) of the acrylic acid alkoxyalkyl ester, when the acrylic polymer is polymerized by cross-linking, moderate molecular chains are entangled with each other. This is presumably because the storage elastic modulus of the pressure-sensitive adhesive layer does not decrease even at high temperatures. That is, even when the gel fraction and storage elastic modulus (23 ° C.) of the pressure-sensitive adhesive layer are relatively low, the adhesive strength and storage elastic modulus at high temperatures are not excessively reduced, and stress relaxation and resistance Both foam peeling properties can be achieved.

  In addition, the monomer component forming the acrylic polymer that is the base polymer in the pressure-sensitive adhesive layer of the present invention further contains a polar group-containing monomer, a polyfunctional monomer, and other copolymerizable monomers. It may be contained as a polymerization monomer component.

  In addition, said "(meth) acryl" represents "acryl" and / or "methacryl", and others are the same. Although not particularly limited, the content of the acrylic polymer as the base polymer in the pressure-sensitive adhesive layer of the present invention is preferably 60% by weight or more based on the total weight (100% by weight) of the pressure-sensitive adhesive layer. Preferably it is 80 weight% or more.

  As an essential monomer component for forming the acrylic polymer, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group (hereinafter simply referred to as “(meth) acrylic acid alkyl ester”) may be used. ) Can be suitably used. Specific examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, (meth ) Isobutyl acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate , Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid Isodecyl, undecyl (meth) acrylate, dodecyl (meth) acrylate, (Meth) acrylic acid tridecyl, (meth) acrylic acid tetradecyl, (meth) acrylic acid pentadecyl, (meth) acrylic acid hexadecyl, (meth) acrylic acid heptadecyl, (meth) acrylic acid octadecyl, (meth) acrylic acid nonadecyl, (meta ) (Meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group such as eicosyl acrylate. Moreover, the (meth) acrylic acid alkyl ester may be used alone or in combination of two or more. Among them, (meth) acrylic acid alkyl ester having 2 to 14 carbon atoms in the alkyl group is preferable, and (meth) acrylic acid alkyl ester having 2 to 10 carbon atoms in the alkyl group is more preferable. In particular, 2-ethylhexyl acrylate (2EHA) is preferable.

  Moreover, (meth) acrylic acid alkoxyalkyl ester [alkoxyalkyl (meth) acrylate] can also be suitably used as the essential monomer component (more preferably, the main monomer component) for forming the acrylic polymer. Particularly preferred is an acrylic acid alkoxyalkyl ester [alkoxyalkyl acrylate]. Although it does not specifically limit as (meth) acrylic-acid alkoxyalkylester, For example, (meth) acrylic-acid 2-methoxyethyl, (meth) acrylic-acid 2-ethoxyethyl, (meth) acrylic-acid methoxytriethylene glycol, (meta ) 3-methoxypropyl acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, and the like. The said (meth) acrylic-acid alkoxyalkylester can be used individually or in combination of 2 or more types. Among them, 2-methoxyethyl acrylate (2MEA) is preferable.

  In addition, the content of the essential monomer component [(meth) acrylic acid alkyl ester and / or (meth) acrylic acid alkoxyalkyl ester] forming the above acrylic polymer is selected from the viewpoint of adhesiveness of the pressure-sensitive adhesive layer. The amount is preferably 5% by weight or more (for example, 5 to 100% by weight), more preferably 5 to 95% by weight, based on the total amount (100% by weight) of monomer components forming the polymer. In addition, when both (meth) acrylic acid alkyl ester and (meth) acrylic acid alkoxyalkyl ester are used as monomer components, the content of (meth) acrylic acid alkyl ester and (alkyl) alkoxyalkyl (meth) acrylate The total amount of ester content (total content) only needs to satisfy the above range. Among the above, it is preferable that both (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester are used as essential monomer components for forming the acrylic polymer. In that case, the content of the (meth) acrylic acid alkyl ester is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, based on the total amount of monomer components (100% by weight) forming the acrylic polymer. %, More preferably 65-80% by weight, most preferably 65-75% by weight. If the content exceeds 95% by weight, the adhesiveness may decrease, and if it is less than 5% by weight, the elastic modulus of the pressure-sensitive adhesive layer may be too high. Further, the content of the alkoxyalkyl ester of acrylic acid is preferably 10 to 45% by weight, more preferably 10 to 40% by weight, and still more preferably with respect to the total amount (100% by weight) of monomer components forming the acrylic polymer. 20 to 35% by weight, most preferably 20 to 34.5% by weight. If the content exceeds 45% by weight, the elastic modulus of the pressure-sensitive adhesive layer may be too high, and if it is less than 10% by weight, the adhesiveness may decrease.

  Examples of the polar group-containing monomer include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and other carboxyl group-containing monomers or anhydrides thereof (maleic anhydride, etc. ); Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate Hydroxyl group (hydroxyl group) -containing monomers such as vinyl alcohol and allyl alcohol; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-hydro Amide group-containing monomers such as ethyl acrylamide; Amino group-containing monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; ) Glycidyl group-containing monomers such as glycidyl acrylate and methyl glycidyl (meth) acrylate; Cyano group-containing monomers such as acrylonitrile and methacrylonitrile; N-vinyl-2-pyrrolidone, (meth) acryloylmorpholine , N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinyl oxazole and other heterocyclic ring-containing vinyl monomers; sodium vinyl sulfonate, etc. Sulfonic acid group-containing monomer of 2-hydroxyethyl Chestnut phosphoric acid group-containing monomers such as acryloyl phosphate; cyclohexyl maleimide, imide group-containing monomers such as isopropyl maleimide; 2-methacryloyloxy such acryloyl isocyanate group-containing monomers such as methacryloyloxyethyl isocyanate. The said polar group containing monomer can be used individually or in combination of 2 or more types. Among the above-mentioned polar group-containing monomers, carboxyl group-containing monomers or acid anhydrides thereof, hydroxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, heterocyclic-containing vinyls Monomers are preferable, and acrylic acid (AA), 4-hydroxybutyl acrylate (4HBA), N-vinyl-2-pyrrolidone (NVP), and N-hydroxyethylacrylamide (HEAA) are particularly preferable.

  The content of the polar group-containing monomer is preferably 15% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When it exceeds 15% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high. As a result, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered. If it is less than 0.01% by weight and too small, the adhesiveness may be lowered.

  Among the above, the content of the hydroxyl group-containing monomer is preferably 5% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When the content exceeds 5% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered. Content of polar group-containing monomers other than hydroxyl group-containing monomers (particularly carboxyl group-containing monomers, amide group-containing monomers, amino group-containing monomers, heterocyclic-containing vinyl monomers) Is preferably 15% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When the content exceeds 15% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered.

  Examples of the polyfunctional monomer include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol di (meth) acrylate. , Neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methanetri (meth) ) Acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate and the like. The said polyfunctional monomer can be used individually or in combination of 2 or more types. Among the above, as the polyfunctional monomer, trimethylolpropane triacrylate (TMPTA) is preferable.

The content of the polyfunctional monomer is preferably 0.5% by weight or less with respect to 100% by weight of the total amount of monomer components forming the acrylic polymer. When the content exceeds 0.5% by weight, for example, the cohesive force of the pressure-sensitive adhesive layer becomes too high, and the stress relaxation property may be lowered.

  Examples of copolymerizable monomers (other copolymerizable monomers) other than the above polar group-containing monomers and polyfunctional monomers include cyclopentyl (meth) acrylate and cyclohexyl (meth). (Meth) acrylates having an alicyclic hydrocarbon group such as acrylate and isobornyl (meth) acrylate, and (meth) acrylates having an aromatic hydrocarbon group such as phenyl (meth) acrylate and the like (meth ) (Meth) acrylic acid esters other than alkyl acrylates, alkoxyalkyl (meth) acrylates, polar group-containing monomers and polyfunctional monomers; vinyl esters such as vinyl acetate and vinyl propionate; styrene , Aromatic vinyl compounds such as vinyl toluene; ethylene, butadiene, isoprene, isobutylene, etc. Olefins or dienes; vinyl ethers such as vinyl alkyl ethers; and vinyl chloride.

  The acrylic polymer can be prepared by polymerizing the monomer component by a known or conventional polymerization method. Examples of the polymerization method of the acrylic polymer include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a polymerization method by active energy ray irradiation (active energy ray polymerization method). Among them, the solution polymerization method and the active energy ray polymerization method are preferable in terms of transparency, water resistance, production cost and the like, and particularly when forming a relatively thick pressure-sensitive adhesive layer, active energy ray polymerization (photopolymerization and Method), and an ultraviolet polymerization method by ultraviolet irradiation is particularly preferable.

Examples of the active energy rays irradiated in the above active energy ray polymerization (photopolymerization) include ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, and ultraviolet rays, among others. Ultraviolet rays are suitable for the use of the present invention. Further, the irradiation energy, irradiation time, irradiation method, and the like of the active energy ray are not particularly limited as long as they do not impair the gist of the present invention.

  In the solution polymerization, various common solvents can be used. Examples of such solvents include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane and methylcyclohexane Organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. A solvent can be used individually or in combination of 2 or more types.

  In preparing the acrylic polymer, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) can be used depending on the type of polymerization reaction. A polymerization initiator can be used individually or in combination of 2 or more types.

  The photopolymerization initiator is not particularly limited. For example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photo An active oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, a thioxanthone photopolymerization initiator, and the like can be used. The amount of the photopolymerization initiator used is not particularly limited, but is preferably in the range of 0.01 to 0.2 parts by weight with respect to 100 parts by weight of the total amount of monomer components forming the acrylic polymer.

Specific examples of the benzoin ether photopolymerization initiator include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one. And anisole methyl ether. Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). Examples include dichloroacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. . Specific examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzyl photopolymerization initiator include benzyl.
Specific examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Specific examples of the ketal photopolymerization initiator include benzyldimethyl ketal. Specific examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

Specific examples of the thermal polymerization initiator include azo polymerization initiators [for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis. (2-methylpropionic acid) dimethyl, 4,4′-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [ 2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-di) Methyleneisobutylamidine) dihydrochloride], peroxide-based polymerization initiators (eg, dibenzoyl peroxide, tert-butylpermaleate, etc.), redox Scan type polymerization initiators and the like. The amount of the thermal polymerization initiator used is not particularly limited as long as it does not impair the gist of the present invention, and may be any range that can be conventionally used as a thermal polymerization initiator.

  In the pressure-sensitive adhesive layer of the present invention, a cross-linking agent, a cross-linking accelerator, a tackifier (for example, rosin derivative resin, polyterpene resin, petroleum resin, oil-soluble phenol resin, etc.), anti-aging agent, filler, as necessary , Colorants (pigments, dyes, etc.), UV absorbers, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, etc., as necessary, as long as they do not impair the properties of the present invention. Can be used.

  The said crosslinking agent can control the gel fraction of an adhesive layer by bridge | crosslinking the base polymer of an adhesive layer. As crosslinking agents, isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents Agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, amine crosslinking agents, and the like, and isocyanate crosslinking agents and epoxy crosslinking agents can be preferably used. A crosslinking agent can be used individually or in combination of 2 or more types.

In the base material-less double-sided pressure-sensitive adhesive sheet according to the present invention, as a characteristic of the pressure-sensitive adhesive composition, for example, the pressure-sensitive adhesive layer itself tends to be designed hard for the purpose of preventing light leakage at the time of laminating a polarizing plate. As a specific index, for example, the storage elastic modulus (G ′) in dynamic viscoelasticity is preferably 2.0 × 10 ⁵ Pa or more, more preferably 4.0 × 10 ⁵ Pa or more. When it is out of the range, for example, light leakage prevention at the time of laminating a polarizing plate may be insufficient.

  The thickness of the pressure-sensitive adhesive sheet constituting the substrate-less double-sided pressure-sensitive adhesive sheet in the present invention is in the range of 50 μm to 400 μm, preferably 100 μm to 400 μm, and more preferably 150 μm to 350 μm. In the case of 50 μm or less, for example, the gap generated between the optical members becomes too large, and it may be difficult to fill the corners with the adhesive sheet. On the other hand, when the thickness of the pressure-sensitive adhesive sheet exceeds 400 μm, the thickness of the pressure-sensitive adhesive sheet becomes excessively thicker than the gap generated between the optical members, and there arises a problem such that the excess pressure-sensitive adhesive sheet component protrudes between the optical members. There is a case.

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

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester 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 diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Film internal haze measurement of first release film Filled with ethanol solution using haze meter device (model: HZ-2) manufactured by Suga Test Co., Ltd. based on JIS-K-7136 using sample film The haze value of the obtained glass cell was set to 0%, and the internal haze of the film was measured in a state where the test piece of the sample film was immersed in the cell.

(4) Maximum roughness (Rt) measurement of film surface not provided with release layer Non-contact surface measurement system using direct phase detection interferometry (so-called two-beam interferometry using Michelson interference) The maximum roughness (Rt) of the film surface on which the release layer of the sample film was not provided was measured by “Micromap 512” manufactured by Micromap. The measurement wavelength was 554 nm, an objective lens with a magnification of 20 times was used, 20 visual fields were measured, and the average value was adopted.

(5) Measurement of storage elastic modulus (G ′) of adhesive layer The separator was peeled from the double-sided adhesive sheets obtained in Examples and Comparative Examples, and only the acrylic adhesive layer was laminated, and the thickness (after drying) A laminate of 1.5 mm ± 0.1 mm acrylic pressure-sensitive adhesive layer was prepared and used as a measurement sample. The above measurement sample was measured at a temperature rising rate of 5 ° C./min in the range of −70 to 200 ° C. under the condition of a frequency of 1 Hz using an “Advanced Rheometric Expansion System (ARES)” manufactured by Rheometric Scientific. The storage elastic modulus (G ') at ° C was determined. In addition, the storage elastic modulus (G ') of the adhesion layer used by the Example and comparative example in this invention was 5.0 * 10 < ⁴ > Pa.

(6) Release force (F1 and F2) measurement of release film After applying one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the release layer surface of the sample film, the size is 50 mm × 300 mm. Cut and measure the peel force after standing at room temperature for 1 hour. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under a tensile speed of 300 mm / min.

(7) Zipping occurrence status (practical property substitution evaluation)
The following pressure-sensitive adhesive composition was applied to the second release film, heat-treated at 100 ° C. for 5 minutes, and then a pressure-sensitive adhesive layer having a thickness (after drying) of 150 μm was obtained. Next, in the substrate-less double-sided pressure-sensitive adhesive sheet in which the first release film was bonded to the surface of the adhesive layer, the peeling state was observed when the first release film was peeled off, and the occurrence of zipping was determined according to the following criteria. .
<Acrylic adhesive composition>
(Monomer composition)
2-ethylhexyl acrylate 70% by weight
2-methoxyethyl acrylate 29% by weight
4-hydroxybutyl acrylate 1% by weight
0.1 part of Nippon Polyurethane Coronate L was added to 100 parts by weight of the monomer composition to obtain an acrylic pressure-sensitive adhesive layer forming composition.
(Criteria)
○: Peeling very smoothly, no peeling streaks, no peeling noise △: Minor peeling streaks are observed, slight peeling noise is generated, or slight zipping occurs (problem is practically problematic) May have a level)
X: Peeling streaks are observed and peeling sound is generated. Zipping occurs (level that causes problems in practice)

(8) Evaluation of peelability of first and second release films (practical property substitution evaluation)
In the item (7), sensory evaluation was performed according to the following criteria for the situation of the interface between the second release layer and the adhesive layer when the first release film was peeled off.
(Criteria)
○: No abnormality is observed at the interface between the second release layer and the adhesive layer (practically no problem level)
Δ: Slight floating is observed at the interface between the second release layer and the adhesive layer (a level that may cause a practical problem)
X: Clear floating is observed at the interface between the second release layer and the adhesive layer (practically problematic level)

(9) Inspectability evaluation (practical property substitution evaluation)
The first release film side of the substrate-less double-sided adhesive sheet with release films on both sides of the adhesive layer is surface-observed with a digital microscope manufactured by HIROX, and the ease of inspection is determined according to the following criteria. It was.
(Criteria)
○: Easy inspection (practical level)
×: Since it is difficult to inspect, it is necessary to peel off the release film at one end (practically problematic level)

(10) Comprehensive evaluation (practical property substitution evaluation)
Using the substrate-less double-sided pressure-sensitive adhesive sheets produced in the examples and comparative examples, comprehensive evaluation was performed according to the following criteria for each evaluation item of zipping occurrence status, peelability, and testability.
(Criteria)
○: Zipping occurrence status, peelability, and easy inspection are all ○ (practically no problem level)
Δ: At least one of the zipping occurrence status, peelability, and ease of inspection among the zipping occurrence status and peelability is Δ (a level that may cause a problem in practical use).
×: At least one of zipping occurrence status, peelability, and testability is × (practically problematic level)

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
Production Example 1 (Polyethylene terephthalate A1)
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, after adding 0.04 part of ethylene glycol slurry ethyl acid phosphate and 0.03 part of antimony trioxide, the temperature reached 280 ° C. and the pressure reached 15 mmHg in 100 minutes. It was 0.3 mmHg. After 4 hours, the system was returned to atmospheric pressure to obtain polyethylene terephthalate A1 having an intrinsic viscosity of 0.61.

Production Example 2 (Polyethylene terephthalate A2)
In Production Example 1, production was carried out in the same manner as in Production Example 1 except that 0.3 part of alumina silicate particles having an average particle size of 0.035 μm was added to obtain polyethylene terephthalate A2 having an intrinsic viscosity of 0.61.

Production Example 3 (Polyethylene terephthalate A3)
In Production Example 1, production was carried out in the same manner as in Production Example 1 except that 0.6 part of silica particles having an average particle diameter of 2.5 μm was added, to obtain polyethylene terephthalate A3 having an intrinsic viscosity of 0.62.

<Manufacture of release film F1>
Two vented extruders with polyethylene terephthalate A1, A2 and A3 blended in proportions of 80%, 0% and 20%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material After being melt-extruded at 290 ° C., it was cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an amorphous film having a thickness of about 1500 μm. The film was stretched 3.3 times in the machine direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.6 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F1 having a thickness of 125 μm (thickness ratio = 2.5 μm / 120 μm / 2.5 μm).

<Manufacture of release film F2>
Two vented extruders with polyethylene terephthalate A1, A2 and A3 blended in proportions of 80%, 0% and 20%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material After being melt-extruded at 290 ° C. and then melted and extruded at 290 ° C., it was cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method, so A regular film was obtained. The film was stretched 3.5 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.8 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F2 having a thickness of 100 μm (thickness composition ratio = 2.5 μm / 95 μm / 2.5 μm).

<Manufacture of release film F3>
Two vented extruders with polyethylene terephthalate A1, A2 and A3 blended in proportions of 80%, 0% and 20%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 1100 μm. The film was stretched 3.5 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 4.0 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F3 having a thickness of 75 μm (thickness ratio = 2.5 μm / 70 μm / 2.5 μm).

<Manufacture of release film F4>
Two vented extruders using polyethylene terephthalate A1, A2, and A3 blended in proportions of 89%, 0%, and 11%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 1100 μm. The film was stretched 3.5 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 4.0 times in the transverse direction at 100 ° C., and heat-treated at 210 ° C. to obtain a release film F4 having a thickness of 75 μm (thickness ratio = 2.5 μm / 70 μm / 2.5 μm).

<Manufacture of release film F5>
Two vented extruders with polyethylene terephthalate A1, A2 and A3 blended in proportions of 80%, 0% and 20%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material After being melt-extruded at 290 ° C., it was cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an amorphous film having a thickness of about 740 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 4.0 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F5 having a thickness of 50 μm (thickness composition ratio = 2.5 μm / 45 μm / 2.5 μm).

<Manufacture of release film F6>
Two vented extruders using polyethylene terephthalate A1, A2, and A3 blended in proportions of 89%, 0%, and 11%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material After being melt-extruded at 290 ° C., it was cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an amorphous film having a thickness of about 740 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 4.0 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F6 having a thickness of 50 μm (thickness ratio = 2.5 μm / 45 μm / 2.5 μm).

<Manufacture of release film F7>
Two vented extruders with polyethylene terephthalate A1, A2 and A3 blended in proportions of 80%, 0% and 20%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 550 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.9 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F7 having a thickness of 38 μm (thickness composition ratio = 2.5 μm / 33 μm / 2.5 μm).

<Manufacture of release film F8>
Two vented extruders using polyethylene terephthalate A1, A2, and A3 blended in proportions of 89%, 0%, and 11%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 550 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.9 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F8 having a thickness of 38 μm (thickness composition ratio = 2.5 μm / 33 μm / 2.5 μm).

<Manufacture of release film F9>
Two vented extruders using polyethylene terephthalate A1, A2, and A3 blended in proportions of 89%, 0%, and 11%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 550 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.9 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F9 having a thickness of 38 μm (thickness ratio = 2.5 μm / 33 μm / 2.5 μm).

<Manufacture of release film F10>
Two vented extruders using polyethylene terephthalate A1, A2, and A3 blended in proportions of 83%, 10%, and 7%, respectively, as the surface layer material and polyethylene terephthalate A1 = 100% material as the intermediate layer material 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 amorphous film having a thickness of about 550 μm. This film was stretched 3.7 times in the longitudinal direction at 85 ° C., and the coating agent composition and the release agent composition shown in Table 1 below were each applied to a thickness (after drying) of 0.06 μm on one side of the film. Thereafter, the film was stretched 3.9 times in the transverse direction at 100 ° C. and heat-treated at 210 ° C. to obtain a release film F10 having a thickness of 38 μm (thickness composition ratio = 2.5 μm / 33 μm / 2.5 μm).

(Example of release layer compound)
Curing type silicone resin (A1): Dehesive 400E manufactured by Asahi Kasei Wacker Silicone
Curing type silicone resin (A2): X2-7720 manufactured by Toray Dow Corning
Cross-linking agent (B1): Asahi Kasei Wacker Silicone V20
Crosslinking agent (B2): Toray Dow Corning Co., Ltd .: X2-7721
Release modifier (C1): CRA491 manufactured by Asahi Kasei Wacker Silicone
<Releasing agent composition>
Curing type silicone resin (A1): 90% by weight
Curing type silicone resin (A2): 0% by weight
Cross-linking agent (B1): 10% by weight
Cross-linking agent (B2): 0% by weight
Peeling modifier (C1): 0% by weight
The coating agent was diluted with deionized water to adjust the coating solution concentration to 10% by weight.
<< Coating composition >>
・ Polyester resin (A1) Tg = 63 ℃
Acid component: terephthalic acid 50 mol%
Isophthalic acid 48mol%
5-Na sulfoisophthalic acid 2 mol%
Diol component: Ethylene glycol 50 mol%
Neopentyl glycol 50 mol%
Particle (B): Colloidal silica (Nissan Chemical: Snowtex “YL” average particle size 70 nm)
Coating liquid-A was prepared at a blending ratio of A1 / B = 95/5.

Example 1:
<Manufacture of first release film>
A release film F11 was used. The characteristics of the obtained first release film are shown in Tables 1 to 3 below.
<Manufacture of second release film>
A release film F1 was used. The characteristics of the obtained second release film are shown in Tables 1 to 3.
<Manufacture of substrate-less double-sided PSA sheet>
On the release layer of the obtained 2nd release film, after coating the coating liquid comprised from the following acrylic adhesive composition with an applicator, using a hot-air circulation furnace, 100 degreeC, 5 A pressure-sensitive adhesive layer having a coating amount (after drying) of 150 μm was obtained by heat treatment for minutes.
<Acrylic pressure-sensitive adhesive layer forming composition>
(Monomer composition)
2-ethylhexyl acrylate 70% by weight
2-methoxyethyl acrylate 29% by weight
4-hydroxybutyl acrylate 1% by weight
0.1 part of Nippon Polyurethane Coronate L was added to 100 parts by weight of the monomer composition to obtain an acrylic pressure-sensitive adhesive layer forming composition.
Next, the release layer and adhesive layer of the 1st release film were bonded together using the 2 kg rubber roller, and the base material-less double-sided adhesive sheet was obtained.

Examples 2-12 and Comparative Examples 1-2:
In Example 1, except having changed the combination of a coating liquid composition, a 1st release film, and a 2nd release film, it manufactured like Example 1 and obtained the base-material-less double-sided adhesive sheet. Tables 1 to 3 show the properties of the base-material-free double-sided PSA sheets obtained in the above Examples and Comparative Examples.

  The substrate-less double-sided pressure-sensitive adhesive sheet of the present invention has good releasability and has so-called inspectability that can be inspected with the release film attached in an inspection process involving optical evaluation. It can be suitably used as a capacitive touch panel member.

Claims (1)

It is a substrate-less double-sided pressure-sensitive adhesive sheet in which release films are laminated on both sides of the pressure-sensitive adhesive layer, and one release film has a release layer formed by a coating and stretching method on one side of a biaxially stretched polyester film. A substrate-less double-sided pressure-sensitive adhesive sheet characterized by having an internal haze of 0.8% or less and a maximum surface roughness (Rt) of a film surface not provided with a release layer of 300 nm or more.