JP2013253180A - Base-less double-sided pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base-less double-sided pressure-sensitive adhesive sheet, which causes no troubles during peeling even when an adhesive layer is formed thick, to be used, for example, for an electrostatic capacitance type touch panel, and which has handling property and easy inspection property.SOLUTION: A base-less double-sided pressure-sensitive adhesive sheet comprises release films respectively layered on both surfaces of an adhesive layer. One of the release films has a release layer formed by a coating stretching method on a polyester film containing organic particles having an average particle diameter of 0.2 to 1.5 μm and a graininess distribution (d25/d75) of 1.0 to 2.0, and has a film inner haze of 0.6% or less.

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 easy to inspect in an inspection process accompanied by optical evaluation, and has a peelable, The present invention provides a double-sided pressure-sensitive adhesive sheet having good scratch resistance.

  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 a substrateless double-sided pressure-sensitive adhesive sheet for optical applications, not only the substrateless double-sided pressure-sensitive adhesive sheet but also the release film to be combined is much stricter than conventional ones and has fewer optical defects such as foreign matter. A release film is required. Therefore, in the base material-less pressure-sensitive adhesive sheet, it is necessary to be able to cope with an inspection process involving optical evaluation while the release film is bonded.

JP 2010-168425 A

  The present invention has been made in view of the above circumstances, and its solution problem is, for example, for a capacitive touch panel, even when the adhesive layer is thick, no problem occurs at the time of peeling. An object of the present invention is to provide a substrate-less double-sided pressure-sensitive adhesive sheet having inspection ease.

  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 has an average particle size of 0.2 to 1.5 μm. Yes, having a release layer provided by a coating and stretching method on a polyester film containing organic particles having a particle size distribution (d25 / d75) of 1.0 to 2.0, and the internal haze of the film is 0.6% or less It exists in the base-material-free double-sided adhesive sheet characterized by being.

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

FIG. 1 is a schematic cross-sectional view showing a substrate-less double-sided pressure-sensitive adhesive sheet according to an embodiment of the present invention.

  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 | grains to mix | blend is a particle | grains which can provide lubricity, and needs to contain an organic particle from a transparent viewpoint. As specific examples, 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.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles contained in the polyester film needs to be in the range of 0.2 to 1.5 μm. When the average particle size is less than 0.2 μm, the film surface is flattened and the winding properties in the film production process are inferior. On the other hand, when the average particle diameter exceeds 1.5 μm, the occurrence of bright spots due to the particles contained in the film causes troubles in, for example, foreign matter inspection in an inspection process involving optical evaluation.

  Moreover, the particle size distribution of the particles contained in the polyester film in the present invention needs to be sharp. Specifically, the particle size distribution value, which is an index representing the sharpness of the particle size distribution, needs to be 1.0 to 2.0, preferably 1.1 to 1.8. The “particle size distribution value” referred to in the present invention is a particle size distribution value d25 / d75 (d25 and d75 are calculated by calculating the integrated volume of the particle group from the large particle side and correspond to 25% and 75% of the total volume, respectively. It means a value defined by particle size (μm). When the particle size distribution value (d25 / d75) exceeds 2.0, due to coarse particles, foreign matter inspection is hindered in the inspection process with optical evaluation.

  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 for producing the polyester constituting each layer, but the polycondensation reaction may proceed preferably 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.

  Although the thickness of the polyester film which comprises the 1st and 2nd release film of this invention will not be specifically limited if it is a range which can be formed into a film, Usually, 25-250 micrometers, Preferably it is 38-188 micrometers. 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 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, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive 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 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 in the range of 5 to 80 mN / cm for the purpose of the present invention, more preferably in the range of 10 to 70 mN / cm. When the peeling force (F) is out of the above range, problems such as zipping may occur when the release film is peeled off.

  Furthermore, the peel force ratio between the first release film and the second release film in the present invention is preferably 2.0 or more. When the peel force ratio is less than 2.0, the second release film is peeled off when the first release film is peeled from the state of the substrate-less pressure-sensitive adhesive sheet in which the release films are bonded to both surfaces of the pressure-sensitive adhesive layer. There may be a problem such as floating at the interface between the mold layer and the adhesive layer.

  It is an essential requirement that the release layer constituting the first release film in the present invention is 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, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount (after drying) of the release layer is usually from 0.005 to 1 g / m ² , preferably from 0.005 to 0.5 g / m ² , more preferably from 0.01 to 5 in terms of coatability. The range is 0.2 g / m ² . When 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.

  With respect to the first release film and the second release film in the present invention, the surface on which the release layer is not provided, such as an adhesive layer, an antistatic layer, and an oligomer precipitation preventing layer, as long as the gist of the present invention is not impaired. An application layer 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 mold release film previously.

  The film internal haze of the first release film thus obtained needs to be 0.6% or less, preferably 0.4% or less, in order to ensure the ease of inspection in the inspection process with optical evaluation. is there. If the range exceeds 0.6%, the first release film must be peeled off at the time of inspection when the inspection with optical evaluation is performed from the obtained first release film side. Cause inconvenience.

  In the present invention, regarding the first release film, as a specific method for suppressing the film internal haze to 0.6% or less, for example, in the polyester film constituting the first release film, a polyester film having a laminated structure is used. When used, the particle content of the intermediate layer is suppressed to substantially 0%, and the particle content of the surface layer is increased with the polyester layer thickness being made as thin as possible. It is preferable at the point from which the 1st release film which has transparency is obtained.

Furthermore, as an additional requirement for satisfying the above range, in the polyester film constituting the first release film, the thickness of the outermost polyester layer is preferably 5 μm or less on one side. When the thickness of the polyester layer is out of the above range, the content of particles in the polyester film is excessively increased, and the internal haze of the film may exceed 0.6%.
In this invention, it is preferable that the internal transparency of the film in the measuring method mentioned later is 96.5% or more. When the internal transparency of the film is less than 96.5%, the transparency of the film may be lowered. In order to set the internal transparency of the film within the above range, for example, the type of particles to be used, the particle size, the amount added, the strengthening of the filter in the production line, the film production conditions (film stretching temperature, draw ratio), used in the film production line This can be achieved by appropriately combining various conditions such as smoothing the rolls to be rolled.

  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 force 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. 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 above monomer components by a conventionally 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.

Next, 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 polarizing plate bonding. 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) Average particle size (d50) and particle size uniformity (d25 / d75)
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. In addition, the ratio d25 / d75 of the diameter of the point having a weight fraction of 25% and the diameter of the point having a weight fraction of 75%, integrated from the large particle side, was used as the particle size distribution value.

(3) In-film transparency measurement of the first release film Measured according to ASTM D1746 using a transparency measuring instrument (TM-1D 2-digit decimal type: light source wavelength 546 ± 5 nm) manufactured by Murakami Color Research Laboratory. .
Specifically, the measurement was performed by setting the sample film in a glass cell and immersing it in ethanol. The internal transparency is defined by the following formula.
Internal transparency (%) = (light quantity when film is in ethanol solution / light quantity when film is not in ethanol solution) × 100

(4) Measurement of haze inside film 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 haze value in the film was measured in a state where the test piece of the sample film was immersed in the cell.

(5) Measurement of storage elastic modulus (G ′) of adhesive layer The separator was peeled off 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 attaching one side of a double-sided adhesive tape (“No. 502” manufactured by Nitto Denko Corporation) to the release layer surface of the sample film, 50 mm × 300 mm The peel force 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 a tensile speed of 300 mm / min.

(7) Evaluation of peelability of first and second release films (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 base material-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 determination was made 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)
○: 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)

(8) Evaluation of testability (practical property substitution evaluation)
A black metal powder (foreign matter) having a size of 50 μm or more was mixed at 50 / m ² at the time of preparing the pressure-sensitive adhesive composition, and a baseless double-sided pressure-sensitive adhesive sheet was prepared in the same manner as in the item (7). . Next, from the first release film side of the obtained substrate-less double-sided pressure-sensitive adhesive sheet, a pressure-sensitive adhesive layer is obtained with a digital microscope (model: KH-7700) manufactured by HIROX while the release film is still bonded. The foreign matter was observed and judged according to the following criteria.
(Criteria)
○: Foreign matter inspection of the adhesive layer is possible with the release film affixed (practically acceptable level)
×: Since it is difficult to inspect the adhesive layer with the release film attached, it is necessary to peel off the release film at one end (practically problematic level)

(9) Evaluation of scratch resistance on film surface (practical property substitution evaluation)
Taihei Rika Kogyo's exclusive jig (5cm x 7cm, 500g) is wrapped with sheet-like cotton (Bencot manufactured by Asahi Kasei Co., Ltd.), and 30 times (15cm long) on the film surface where the release layer of the first release film is not provided Range). Thereafter, the rubbed portion was visually observed under a three-wavelength fluorescent lamp, and judged according to the following criteria.
(Criteria)
○: Scratch occurrence frequency is 3 or less △: Scratch occurrence frequency exceeds 3 and 5 or less ×: Scratch occurrence frequency is 6 or more ○ is a level that causes no problem in practical use.

(10) Comprehensive evaluation (practical property substitution evaluation)
Using the substrate-less double-sided pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, comprehensive evaluation was performed according to the following criteria for each evaluation item of peelability, testability, and scratch resistance.
(Criteria)
○: Peelability, ease of inspection, and scratch resistance are all ○ (practically no problem level)
Δ: At least one of peelability, ease of inspection, and scratch resistance is Δ (level that may cause a problem in practical use)
X: At least one of peelability, testability and scratch resistance is x (practically problematic level)

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
Production Example 1 (Polyester 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 normal pressure to obtain polyester A1 having an intrinsic viscosity of 0.61.

Production Example 2 (Polyester A2>
In the method for producing polyester (A1), after adding ethyl acid phosphate, ethylene glycol slurry of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 0.8 μm is contained in the polyester in a content of 0.5. Polyethylene terephthalate A2 was obtained using the same method as the production method of the polyester (A) except that it was added in an amount of% by weight. The production method of divinylbenzene / methyl methacrylate copolymer crosslinked particles is as follows. A homogeneous solution of 100 parts of methyl methacrylate, 25 parts of divinylbenzene, 22 parts of ethylvinylbenzene, 1 part of benzoyl peroxide and 100 parts of toluene is dispersed in 700 parts of water, and then stirred at 80 ° C. for 6 hours in a nitrogen atmosphere. Polymerization was carried out while heating. The average particle diameter of the obtained crosslinked polymer granules having ester groups was about 0.1 mm. The produced polymer was washed with demineralized water and extracted twice with 500 parts of toluene to remove a small amount of unreacted monomer linear polymer. Next, the crosslinked polymer particles were pulverized with an attritor and a sand grinder to obtain divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 0.8 μm and a particle size distribution value of 1.6. Intrinsic viscosity was 0.62.

Production Example 3 (Polyester A3)
In Production Example 1, produced in the same manner as in Production Example 1 except that 0.5 part of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 0.5 μm and a particle size distribution value of 1.7 was added. Polyester A3 having a viscosity of 0.61 was obtained.

Production Example 4 (Polyester A4)
In Production Example 1, produced in the same manner as in Production Example 1 except that 0.5 parts of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 1.4 μm and a particle size distribution value of 1.9 were added. Polyester A4 having a viscosity of 0.61 was obtained.

Production Example 5 (Polyester A5)
In Production Example 1, produced in the same manner as in Production Example 1 except that 0.5 parts of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 2.5 μm and a particle size distribution value of 1.3 were added. Polyester A5 having a viscosity of 0.61 was obtained.

Production Example 6 (Polyester A6)
In Production Example 1, produced in the same manner as in Production Example 1 except that 0.5 parts of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 0.8 μm and a particle size distribution value of 2.5 were added. Polyester A6 having a viscosity of 0.61 was obtained.

Production Example 7 (Polyester A7)
In Production Example 1, produced in the same manner as in Production Example 1 except that 0.5 part of divinylbenzene / methyl methacrylate copolymer crosslinked particles having an average particle size of 0.12 μm and a particle size distribution value of 2.0 was added. A polyester A7 having a viscosity of 0.61 was obtained.

Production Example 8 (Polyester A8)
Polyester A8 produced in the same manner as in Production Example 1 except that 0.3 part of silicon dioxide particles having an average particle size of 2.3 μm and a particle size distribution value of 1.8 was added in Production Example 1, and polyester A8 having an intrinsic viscosity of 0.61 Got.

Production Example 9 (Manufacture of Release Film F1): Use of 50 μm PET Base Material Raw materials obtained by blending polyesters A1 and A2 at a ratio of 90% and 10%, respectively, are used as surface layer materials, and polyester A1 = 100% material is an intermediate layer. After being fed to two vented extruders and melt extruded at 290 ° C. as a raw material for the above, the thickness of the material is cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. An amorphous film of 1500 μm was obtained. This film was stretched 3.5 times in the longitudinal direction at 85 ° C., and a release agent composition shown in Table 1 below was applied to a thickness (after drying) of 0.06 μm on one side of the film, and then at 100 ° C. in the transverse direction. The film was stretched 4.3 times and heat treated at 235 ° C. to obtain a release film F1 having a thickness of 100 μm (thickness ratio = 2.5 μm / 45 μm / 2.5 μm).
(Example of release layer compound)
Curing type silicone resin (A1): Dehesive 400E manufactured by Asahi Kasei Wacker Silicone
Cross-linking agent (B1): Asahi Kasei Wacker Silicone V20
<Releasing agent composition>
Curing type silicone resin (A1): 90% by weight
Cross-linking agent (B1): 10% by weight
The coating agent was diluted with deionized water to adjust the coating solution concentration to 10% by weight.

Production Example 10 (Production of Release Film F2) to Production Example 15 (Production of Release Film F6)
In Production Example 9, a release film was obtained in the same manner as in Production Example 9 except that the kind of polyester and the blending ratio were different.

Production Example 16 (Manufacture of release film F7) 100 μm PET substrate used Polyester A1 and A8 were blended in proportions of 85% and 15%, respectively, as a surface layer material, and polyester A1 = 100% material was an intermediate layer After being fed to two vented extruders and melt extruded at 290 ° C. as a raw material for the above, the thickness of the material is cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. An amorphous film of 1500 μm was obtained. This film was stretched 3.5 times in the longitudinal direction at 85 ° C., and a release agent composition shown in Table 1 below was applied to a thickness (after drying) of 0.06 μm on one side of the film, and then at 100 ° C. in the transverse direction. The film was stretched 4.3 times and heat treated at 235 ° C. to obtain a release film F7 having a thickness of 100 μm (thickness ratio = 10 μm / 80 μm / 10 μm).
(Example of release layer compound)
Curing type silicone resin (A1): Dehesive 400E manufactured by Asahi Kasei Wacker Silicone
Cross-linking agent (B1): Asahi Kasei Wacker Silicone V20
Release modifier (C1): CRA491 manufactured by Asahi Kasei Wacker Silicone
<Releasing agent composition>
Curing type silicone resin (A1): 80% by weight
Cross-linking agent (B1): 10% by weight
Peeling modifier (C1): 10% by weight
The coating agent was diluted with deionized water to adjust the coating solution concentration to 10% by weight.

Production Example 17 (Production of release film F8)
Polyester A1 and A8 were blended in proportions of 85% and 15%, respectively, as the surface layer raw material, and the polyester A1 = 100% raw material as the intermediate layer raw material was supplied to two vented extruders and supplied at 290 ° C. After being melt-extruded, an amorphous film having a thickness of about 1500 μm was obtained by cooling and solidifying on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method. This film was stretched 3.5 times in the machine direction at 85 ° C., then led to a tenter, stretched 4.3 times in the transverse direction at 100 ° C., and heat treated at 235 ° C. to give a thickness of 100 μm (thickness ratio = A polyester film of 10 μm / 80 μm / 10 μm) was obtained. Next, offline, a release layer composed of the following release agent composition (C) was applied by a reverse gravure coating method so that the coating amount (after drying) was 0.1 g / m ² , and 140 ° C. A release film was obtained by treatment for 30 seconds.
<Releasing agent composition (C)>
Curing type silicone resin (manufactured by Shin-Etsu Chemical: KS-847H): 100 parts Curing agent (manufactured by Shin-Etsu Chemical: PL-50T): 1 part Peeling regulator (manufactured by Shin-Etsu Chemical: KS-3800): 40 parts Toluene / MEK = 1 : 1 mixed solvent: 1500 parts

Production Example 18 (Production of release film F9)
In Production Example 17, except that the release agent composition is different from the following release agent composition,
A release film was obtained.
<Releasing agent composition (D)>
Curing type silicone resin (manufactured by Shin-Etsu Chemical: KS-847H): 100 parts Curing agent (manufactured by Shin-Etsu Chemical: PL-50T): 1 part Mixed solvent of toluene / MEK = 1: 1: 1500 parts

Example 1:
<Manufacture of first release film>
A release film F1 was used. The characteristic of the obtained 1st mold release film is shown to Tables 1-3.
<Manufacture of second release film>
A release film F7 was used. The characteristics of the obtained second release film are shown in Tables 1 to 3. The characteristics of the first release film and the second release film are shown in Table 1 below.
<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 2-5 and Comparative Examples 1-3:
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 sheet | seat of this invention can be utilized suitably as a capacitive touch panel member, for example.

10 Substrate-less double-sided adhesive sheet 11 Adhesive layer 31 First release film (light release sheet)
13 Release film substrate 14 First release layer 32 Second release film (heavy release sheet)
23 release film substrate 24 second release layer

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. One release film has an average particle size of 0.2 to 1.5 μm and a particle size distribution (d25 / d75 ) Having a release layer provided by coating and stretching method on a polyester film containing organic particles of 1.0 to 2.0, and having a film internal haze of 0.6% or less Material-less double-sided adhesive sheet.

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