JP4836475B2 - Substrate-less double-sided adhesive sheet - Google Patents

Description

  The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet, and relates to a substrate-less double-sided pressure-sensitive adhesive sheet that can reduce the peeling force by external stimulation.

  Conventionally, various pressure-sensitive adhesive sheets for surface bonding between objects are known, and a base-less double-sided pressure-sensitive adhesive sheet is known as one of pressure-sensitive adhesive sheets. The substrate-less double-sided pressure-sensitive adhesive sheet is constituted by laminating a light release sheet having a relatively low peeling force and a heavy release sheet having a relatively high peeling force on both sides of the pressure-sensitive adhesive layer. The substrate-less double-sided PSA sheet is first peeled off from the light release sheet, and one side of the exposed PSA layer is bonded to the object surface. The other side of the layer is bonded to a different object surface, thereby surface bonding between the objects.

  Patent Document 1 describes a substrate-less double-sided pressure-sensitive adhesive sheet. The peel force in a heavy release sheet is 25 to 200 g / 50 mm, the peel force in a light release sheet is 5 to 80 g / 50 mm, and the difference between both peel forces is described. Is set to 20 g / 50 mm or more. In the substrate-less double-sided pressure-sensitive adhesive sheet, the difference between the two peeling forces is set within the predetermined range, thereby preventing the peeling failure that the pressure-sensitive adhesive layer follows and transfers to the light-peeling sheet when the light-peeling sheet is peeled off. The Furthermore, by setting the peeling force of the light release sheet to a predetermined amount or more as described above, it is possible to prevent the light release sheet from peeling off or floating from the pressure-sensitive adhesive layer before use.

Conventionally, an adhesive containing a foaming agent and a modified silicone resin is known as an adhesive for bonding two substrates (for example, Patent Document 2). In this adhesive, when two substrates are peeled off, the foaming agent is foamed by heating to reduce the adhesive force between the two substrates, so that the two substrates can be easily peeled off.
JP 7-41736 A JP 2003-238721 A

  By the way, in the substrate-less double-sided pressure-sensitive adhesive sheet, when the peel strength of the heavy release sheet is too high, the light release sheet is peeled off and the pressure-sensitive adhesive layer is adhered to the object, and then the heavy release sheet is peeled off. There may be a transfer failure in which the adhesive remains partially.

  Moreover, when the peeling force of a heavy release sheet is too high, when peeling a heavy release sheet, dipping may arise in an adhesive layer and an unevenness | corrugation may arise in the adhesive surface of an adhesive layer. On the other hand, the base-less double-sided pressure-sensitive adhesive sheet has been increasingly used in recent years, and may be used for bonding other members such as a film to the transmission surface of a polarizing plate. In such an application, when unevenness is generated on the adhesive surface of the pressure-sensitive adhesive layer, light is irregularly reflected on the adhesive surface, so that the light transmittance of the polarizing plate is reduced.

  That is, in order to solve these disadvantages when peeling the heavy release sheet, the peeling force of the heavy release sheet must be set low. However, if the peeling force of the heavy release sheet is set low, the difference in peeling force between the heavy release sheet and the light release sheet cannot be set large, and a peeling failure tends to occur when the light release sheet is peeled off.

  Further, the release force of the release sheet generally changes with time, and the release force of the heavy release sheet may approach the release force of the light release sheet. In such a case, if the peel strength of the heavy release sheet is low and the initial peel force difference between the two sheets is set to be small, the peel force difference between the heavy release sheet and the light release sheet is almost eliminated due to changes over time. Therefore, a peeling failure is likely to occur when the light release sheet is peeled off.

  Accordingly, the present invention has been made in view of such problems, and even when the peel force of the heavy release sheet is low and the peel force difference cannot be set large, the release sheet can be peeled off satisfactorily. The main purpose is to obtain a double-sided PSA sheet.

  The substrate-less double-sided pressure-sensitive adhesive sheet according to the present invention is a substrate-less double-sided pressure-sensitive adhesive sheet in which a first release sheet, a pressure-sensitive adhesive layer, and a second release sheet are laminated in this order. And the said 1st release sheet consists of a structure which has a support body and a 1st release agent layer at least, and the said 1st release agent layer peels with respect to the adhesive layer of a 1st release sheet by receiving external irritation | stimulation. And the reduced peel force is lower than the peel force for the pressure-sensitive adhesive layer of the second release sheet. In the base-material-less double-sided pressure-sensitive adhesive sheet according to the present invention, for example, the first release sheet is peeled after an external stimulus is applied and the peel strength of the first release sheet is reduced. Next, after the pressure-sensitive adhesive layer is adhered to the object surface, the second release sheet is peeled off.

  According to such a configuration, the peeling force of the second release sheet must be set low, and even when the initial difference between the two peeling forces cannot be set large, by applying an external stimulus, The peel force difference of the release sheet can be set to a predetermined amount or more, and a peeling failure when the first release sheet is peeled can be prevented. Here, the 2nd release sheet does not need to provide a release agent layer, when the material itself used for a 2nd release sheet has predetermined peelability with respect to an adhesive layer. When a release agent layer (hereinafter referred to as a second release agent layer) is provided on the second release sheet, the same release agent that can be used for the first release agent layer can be used.

  The first release agent layer preferably includes a release agent and expandable fine particles that expand due to external stimulation.

  The expandable fine particles have a shell wall and an expandable substance that is encapsulated in the shell wall and vaporizes when heated to a predetermined temperature or higher and expands the shell wall toward the outside. In this case, the shell wall preferably contains a thermoplastic resin.

  The average particle diameter of the expandable fine particles is, for example, 1 to 50 μm. The expandable fine particles are preferably 5 to 50 parts by weight with respect to 100 parts by weight of the polymer component of the release agent. Furthermore, the average layer thickness of the first release agent layer is preferably 0.5 to 15 μm, for example.

  The first release agent layer is configured to contain a release agent and a foaming agent. When the foaming agent has a shell wall and an inclusion substance contained in the shell wall, the shell wall of the foaming agent is generated by an external stimulus. It is preferable that the encapsulated material is released to the outside.

  Further, the second release sheet has a configuration having at least a support and a second release agent layer, and the polymer components of the release agents of the first release agent layer and the second release agent layer are preferably the same. . If the polymer component of the release agent is the same compound, the change with time of the first release agent layer and the second release agent layer can be made substantially the same, and even after a long time has passed, external stimuli have been received. The difference between the two peeling forces can be maintained at a predetermined amount or more.

  The external stimulus is preferably either heat or active energy rays. Therefore, the 1st release agent layer reduces the peeling power with respect to the adhesive layer of a 1st release sheet by heating above predetermined temperature, for example. Moreover, for example, the irradiation force with respect to the adhesive layer of a 1st peeling sheet is reduced by irradiating the active energy ray of predetermined intensity | strength. That is, the expandable fine particles may be fine particles that expand when heated to, for example, a predetermined temperature or higher. Further, the expandable fine particles may be fine particles that expand when receiving an active energy ray having a predetermined strength. Here, the active energy ray refers to an electromagnetic wave or a charged particle beam having an energy quantum, that is, an ultraviolet ray or an electron beam.

  It is preferable that the peeling force of the 1st peeling sheet before receiving external stimulation is below the peeling force of a 2nd peeling sheet. Thereby, the difference of both peeling force after receiving external irritation | stimulation can be enlarged and peeling defect can be made hard to occur.

  Moreover, it is also preferable to comprise a 1st peeling sheet in order of a releasing agent layer, an intermediate | middle layer, and a support body. It is possible to improve the surface smoothness of the first release sheet by incorporating expandable fine particles in the multilayer laminate structure of the release agent layer and the intermediate layer, and embedding the expandable fine particles in the multilayer laminate structure. . Here, the average layer thickness of the multilayer structure of the release agent layer and the intermediate layer is preferably equal to or greater than the average particle diameter of the expandable fine particles.

  According to the present invention, the peeling force of the heavy release sheet must be set low, and even when the difference between the peeling forces of the initial light and heavy release sheets cannot be set large, the difference in both peeling forces during peeling is a predetermined amount. It can set to the above and can prevent the peeling defect at the time of peeling a light peeling sheet.

  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. As shown in FIG. 1, the base material-less double-sided pressure-sensitive adhesive sheet 10 is configured by laminating first and second release sheets 30 and 31 on both sides of a pressure-sensitive adhesive layer 11. The first and second release sheets 30 and 31 have first and second release agent layers 15 and 16 on the surface in contact with the pressure-sensitive adhesive layer 11, and the first and second release sheet supports 12 and 13 respectively. It is constructed by stacking.

  The pressure-sensitive adhesive layer 11 is made of a rubber-based, acrylic-based, silicone-based, urethane-based adhesive, or the like. The supports 12 and 13 of the first and second release sheets are not particularly limited. For example, polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyethylene films, polypropylene films, and polyvinyl chloride films. , Polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyether ether ketone film, polyether sulfone film, polyphenylene sulfide film, polyether Imide film, polyimide film, fluororesin film, polyamide film, acrylic resin film, Bornene resin film, and a cycloolefin resin film. The first release agent layer 15 is composed of a release agent containing expandable fine particles that expand by heating. The second release agent layer 16 is similarly composed of a release agent, but the release agent does not contain expandable fine particles.

  The polymer component of the release agent constituting the first and second release agent layers 15 and 16 is, for example, a simple substance such as a silicone resin, an alkyd resin, a silicone-modified alkyd resin, or a long-chain alkyl group-containing polymer, or a mixture thereof. Is used. Here, as the silicone resin, for example, a curable silicone resin that is cured by light irradiation or heating is used. When the curable silicone resin is a thermosetting silicone resin, for example, it contains polydimethylsiloxane as the main chain, and is obtained, for example, by polymerizing polydimethylsiloxane having a vinyl group as a functional group. Further, when a silicone-modified alkyd resin is used as the polymer component, another resin such as an amino resin may be further contained as the polymer component. The release agent is constituted by blending various additives with the polymer component as necessary.

  The expandable fine particles are made of, for example, a shell wall formed of a thermoplastic resin and a thermally expandable substance or an active energy linearly expandable substance enclosed in the shell wall. Examples of the thermally expandable material include physical blowing agents using low boiling point hydrocarbons such as butane, pentane and hexane, inorganic blowing agents such as sodium bicarbonate, ammonium carbonate and ammonium bicarbonate, 2,2′-azobis (4-methoxy -2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionyl), 2,2'-azobis (2- Methylbutyronitrile), 1,1′-azobis (cyclohexanone-1-carbonitrile), 1-[(1-cyano-1-methylethyl) azo] formamide, 2-phenylazo-4-methoxy-2,4- Azonitrile compounds such as dimethylvaleronitrile, 2,2'-azobis (2-methyl-N-phenylpropion-amidine) dihydrochloride, 2,2'-azobis [N- (4-chlorophenyl) -2-methylpropionamidine ), 2,2'-azobis [N- (4-hydroxy Phenyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- (phenylmethyl) -propionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- ( Azoamidines such as 2-propenyl) propionamidine] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine Compound, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] Dihydrochloride, 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) propane] hydrochloride, 2,2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] diha Dourochloride, 2,2'-azobis [2- (5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis {2- [1- Cycloazoamidine-based compounds such as (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] pyropionamide}, 2,2'-azobis {2-methyl-N- [1, 1-bis (hydroxymethyl) ethyl] pyropionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2′-azobis (2-methylpropionamide) ) Azoamide compounds such as dihydrate, 2,2'-azobis (2,4,4-trimethylpentene), 2,2'-azobis (2-methyl) Lopan) and other alkylazo compounds, dimethyl 2,2'-azobis (2-methylpropionate), 4,4'-azobis (4-simevaleric acid), 2,2'-azobis [2- ( Organic foaming agents such as hydroxymethyl) propiononitrile, dinitrosopentamethylenetetramine, azodicarbonamide, paratoluenesulfonyl hydrazide, paratoluenesulfonylacetone hydrazone, 4,4'-oxybis (benzenesulfonylhydrazide) is there. These can be used alone or in combination of two or more. When the thermally expandable fine particles are heated to a predetermined temperature that is equal to or higher than the thermal expansion start temperature, the thermally expandable material is vaporized or decomposed to generate gas, so that the shell wall expands outward. It is done. The expandable fine particles may be a foaming agent. When heated to a predetermined heating temperature, the shell wall is broken, and the vaporized expandable substance or the gas generated by decomposition is released to the outside. good.

  The active energy linearly expansible substance is a photolytic compound that decomposes by, for example, ultraviolet rays to generate gas. Examples of the photolytic compound include a compound having an azide group or a diazo group. Examples of compounds having an azide group include p-azidobenzaldehyde, p-azidoacetophenone, p-azidobenzoic acid, sodium p-azidobenzaldehyde-2-sulfonate, p-azidobenzalacetophenone, 4,4-diazidochalcone, 2,6-bis (4'-azidobenzal) cyclohexanone, 2,6-bis (4'-azidobenzal) 4-methylcyclohexanone, 1,3-bis (4'-azidobenzal) -2-propanone, p-azidobenzal Acetone, sodium p-azidobenzalacetone-2-sulfonate, 1,3-bis (4'-azidocinnamylidene) -2-propanone, 1,3-bis (4'-azidobenzal) -2-propanone 2 '-Sulfonic acid, 4,4'-diazidostilbene-2,2'-disulfonic acid, sodium 4,4'-diazidostilbene-2,2'-disulfonate, 1,3-bis (4'-azidobenzal ) -2-Propanone 2,2'-disulfonic acid, 1,3-bis (4'-azide) 2) -propanone sodium 2,2'-disulfonate, 2,6-bis (4'-azidobenzal) cyclohexanone-2,2'-disulfonic acid, 2,6-bis (4'-azidobenzal) cyclohexanone-2 , 2-disulfonic acid sodium salt, 2,6-bis (4′-azidobenzal) methylcyclohexanone-2,2-disulfonic acid, 2,6-bis (4′-azidobenzal) methylcyclohexanone-2,2-disulfonic acid sodium salt, Examples thereof include 1-azidopyrene, 3-sulfonyl azidobenzoic acid, 4-sulfonylazide benzoic acid, 2,6-dichloro-4-nitroazidobenzene, and azidodiphenylamine. The compounds having a diazo group include p-diazodiphenylamine, 1,2-naphthoquinone-2-diazide-5-sulfonic acid isobutyl ester, 2,3,4-trioxybenzophenone 3,4-bis (naphthoquinone-1,2 -Diazide-5-sulfonic acid ester, 2- (naphthoquinone-1,2-diazide-5-sulfonyloxy) -7-oxynaphthalene, naphthoquinone 1,2-diazide-5-sulfanilide, naphthoquinone-1,2-diazide -5-sulfonic acid novolak ester and the like. These can be used alone or in combination of two or more. When the active energy ray-expandable fine particles receive an active energy ray having a predetermined intensity, gas is generated and the shell wall is expanded outward.

  In the first release agent layer 15, when the expandable fine particles are thermally expanded by an external stimulus, the contact area of the expandable fine particles with the pressure-sensitive adhesive layer 11 increases, and thereby the contact area of the release agent with respect to the pressure-sensitive adhesive layer 11 decreases. . Here, the reduction in the contact area of the release agent with respect to the pressure-sensitive adhesive layer 11 decreases the peeling force of the first release sheet 30 with respect to the pressure-sensitive adhesive layer 11. On the other hand, the second release agent layer 16 does not contain expandable fine particles, and the release force of the second release sheet 31 on the pressure-sensitive adhesive layer 11 is not reduced even when subjected to an external stimulus. As described above, in the present embodiment, when the baseless double-sided pressure-sensitive adhesive sheet 10 receives an external stimulus, the peeling force of the first release sheet 30 is made lower than the peeling force of the second release sheet 31.

  When the base material-less double-sided pressure-sensitive adhesive sheet 10 is used, the first release agent layer 15 reduces the peeling force of the first release sheet 30 with respect to the pressure-sensitive adhesive layer 11 by applying an external stimulus. 1 release sheet 30 can be peeled. Here, the peel force of the first release sheet 30 reduced by external stimulation is set such that the difference from the peel force of the second release sheet 31 is set to 20 mN / 20 mm or more. However, the peeling defect which transfers to the 1st peeling sheet 30 side does not generate | occur | produce. By peeling the first release sheet 30, the pressure-sensitive adhesive layer 11 is exposed, and the exposed surface of the pressure-sensitive adhesive layer 11 is bonded to the object surface. After the bonding, the second release sheet 31 is peeled from the pressure-sensitive adhesive layer 11, and the surface opposite to the surface to which the pressure-sensitive adhesive layer 11 is bonded is exposed. The exposed surface of the pressure-sensitive adhesive layer 11 is further bonded to a surface of a different object, and the two objects are bonded to each other as described above.

  In addition, before giving external irritation | stimulation, the peeling force with respect to the adhesive layer 11 of the 1st and 2nd peeling sheets 30 and 31 is set to 50 mN / 20mm or more, respectively. This is to prevent the release sheets 30 and 31 from being peeled off from the pressure-sensitive adhesive layer 11 before use. However, the peeling force of the second release sheet 31 is preferably set to 2000 mN / 20 mm or less. This is because when the peeling force of the second release sheet 31 is set low, a peeling failure in which the adhesive is transferred to the second release sheet 31 is less likely to occur when the second release sheet 31 is peeled off. Moreover, when the 2nd peeling sheet 31 peels, it is because a dipping does not arise in the adhesive layer 11, but an unevenness | corrugation does not arise in the adhesive surface of the adhesive layer 11. FIG. If there is no unevenness on the adhesive surface of the pressure-sensitive adhesive layer 11, irregular reflection or the like does not occur in the pressure-sensitive adhesive layer 11 when light is incident on the pressure-sensitive adhesive layer 11. Therefore, the base material-less double-sided pressure-sensitive adhesive sheet 10 is suitably used for attaching another member to the light incident surface, light emitting surface, light reflecting surface, or the like of an optical element (for example, a polarizing plate).

  Moreover, it is preferable that the peeling force with respect to the adhesive layer 11 of the 1st peeling sheet 30 before giving an external stimulus is below the peeling force with respect to the adhesive layer 11 of the 2nd peeling sheet 31. FIG. If the peeling force of the 1st peeling sheet 30 is set below the peeling force of the 2nd peeling sheet 31, when the peeling force of the 1st peeling sheet 30 is reduced by external stimulation, the difference of both peeling force can be enlarged. .

  The polymer component of the release agent constituting the first and second release agent layers 15 and 16 is not particularly limited, but a similar compound is preferably used. That is, for example, when a silicone resin is used as the polymer component of the first release agent layer 15, the silicone component is also preferably used as the polymer component of the second release agent layer 16, and the polymer component is composed of the same compound. Is more preferable. Furthermore, it is better that the composition of the release agent is the same. In this way, by approximating the release agents of the first release agent layer and the second release agent layer and making them the same, it is possible to approximate the change with time of the release force of the first and second release sheets with respect to the adhesive layer 11. Or the same. If the change with time of both peeling forces is similar or the same, the initial difference between the two peeling forces can be substantially maintained even if the changes with time are changed. Accordingly, even after the pressure-sensitive adhesive sheet 10 is left for a long time, if the peeling force of the first release sheet 30 is reduced by an external stimulus, the difference in peel force between the first and second release sheets 30 and 31 is 20 mN / 20 mm or more. Can be set.

  The expandable fine particles are preferably 5 to 50 parts by weight with respect to 100 parts by weight of the polymer component of the release agent. When the amount is less than 5 parts by weight, the peeling force cannot be sufficiently reduced when the expandable fine particles expand. On the other hand, when the amount exceeds 50 parts by weight, in the case where the polymer component of the release agent is polymerized or crosslinked on the support 12 of the first release sheet, inconveniences such as inability to polymerize or crosslink occur.

  The average layer thickness of the first release agent layer 15 is 0.5 to 15 μm, and preferably 1 to 15 μm. On the other hand, the average particle size of the expandable fine particles is 1 to 50 μm, preferably 1 to 20 μm. When the average particle diameter of the expandable fine particles exceeds 50 μm, it becomes difficult to fix the expandable fine particles to the release agent layer 15. The average particle diameter of the expandable fine particles may be equal to or less than the average layer thickness of the first release agent layer 15, or may be larger than the average layer thickness. The average layer thickness of the second release agent layer 16 is 0.1 μm to 15 μm, preferably 0.2 to 5.0 μm.

  FIG. 2 is a diagram schematically showing the first release agent layer 15. As shown in FIG. 2, when the average particle size of the expandable fine particles 20 is equal to or less than the average layer thickness of the first release agent layer 15, the expandable fine particles 20 are embedded in the first release agent layer 15. The interface between the first release agent layer 15 and the pressure-sensitive adhesive layer 11 can be made smooth.

  Hereinafter, a method for producing the substrate-less double-sided pressure-sensitive adhesive sheet 10 will be described. First, first and second release sheet supports 12 and 13 are prepared. Next, the release agent and the expandable fine particles are diluted or dispersed in a solvent such as toluene, MEK (methyl ethyl ketone), and the mixture is applied to the support 12 of the first release sheet, followed by heat drying. A first release agent layer 15 is formed on one surface of the support 12 of the first release sheet. However, the heating temperature in heat drying is set lower than the expansion start temperature of the thermally expandable fine particles. Further, when the polymer component of the release agent of the first release agent layer 15 is polymerized or crosslinked on the sheet after coating, it may be polymerized or crosslinked in this heat drying step, in this case, the heating temperature in heat drying Is set higher than the polymerization or crosslinking start temperature and lower than the expansion start temperature. Similarly, the second release agent layer 16 is formed by applying a release agent diluted or dispersed in a solvent such as toluene or MEK to the support 13 of the second release sheet and then drying by heating. The

  The pressure-sensitive adhesive layer 11 is formed by applying a pressure-sensitive adhesive on the surface on which one of the first or second release sheets 30 and 31 is formed. One release sheet on which the pressure-sensitive adhesive layer 11 is laminated has the surface on which the pressure-sensitive adhesive layer 11 is laminated bonded to the surface on which the release agent layer of the other release sheet is laminated. The adhesive sheet 10 is obtained. The substrate-less double-sided pressure-sensitive adhesive sheet 10 is usually wound up and formed into a roll shape. The release agent and the pressure-sensitive adhesive are applied by a known method using a Mayer bar, a roll coater or the like.

  A primer layer is laminated between the first release sheet support 12 and the first release agent layer 15 and / or between the second release sheet support 13 and the second release agent layer 16. May be. The primer layer is composed of, for example, a mixture of an organoaluminum compound and an organosilicon compound. As the organoaluminum compound, for example, aluminum tris (acetylacetonate) is used, and as the organosilicon compound, for example, γ-methacryloxypropyltrimethoxysilane is used. By providing such a primer layer, when the adhesion between the support and the release agent layer is poor, the adhesion can be improved.

  Moreover, a primer layer is comprised by the metal alkoxide and / or metal alkoxide partial hydrolyzate condensation polymer, for example. Such a primer layer has an antistatic effect, and can prevent generation of static electricity when the sheet is fed out from the roll-shaped baseless double-sided pressure-sensitive adhesive sheet 10.

  Furthermore, an intermediate layer containing expandable fine particles may be provided between the support 12 of the first release sheet and the first release agent layer 15. That is, the multilayer structure of the intermediate layer and the first release agent layer 15 contains and holds the expandable fine particles.

  In addition, as shown in FIG. 3, when the total average layer thickness of the first release agent layer 15 and the intermediate layer 21 is equal to or larger than the average particle diameter of the expandable fine particles 20, the intermediate fine layer 20 becomes the primer layer. 21 and the first release agent layer 15 are completely embedded, and the interface between the first release agent layer 15 and the pressure-sensitive adhesive layer 11 can be made smooth.

  Furthermore, the total average layer thickness of the first release agent layer and the intermediate layer is preferably substantially the same as the average particle diameter of the fine particles. When the average layer thickness and the average particle diameter are substantially the same, when the fine particles expand, the peeling force can be efficiently reduced. When the intermediate layer is not provided, it is preferable that the average layer thickness of the first release agent layer 15 and the average particle diameter of the expandable fine particles are substantially the same for the same reason.

  Here, examples of the material used for the intermediate layer include acrylic resins, epoxy resins, butyral resins, vinyl acetate resins, cellulose resins, alkyd resins, silicone resins, and synthetic rubbers such as NBR. Moreover, as an organic solvent that can be used to prepare a solution by dissolving these resins, it is a good solvent for the resin component, and is easily removed from the coating layer in a drying step after solution coating. There is no particular limitation as long as it can be used, and examples thereof include toluene and normal hexane. The intermediate layer is also formed by being applied in the same manner as the release agent and the pressure-sensitive adhesive. That is, a material in which thermally expandable fine particles are dispersed in the coating agent for the intermediate layer is applied to the support 12 of the first release sheet and formed. In this case, the first release agent layer is formed by applying a release agent containing no thermally expandable fine particles onto the intermediate layer. Since other manufacturing methods are the same as the case where the intermediate layer is not provided, the description thereof is omitted.

  The present embodiment will be described below using examples, but the present invention is not limited to the configurations of the following examples.

[Example 1]
As a support for the first and second release sheets, a polyethylene terephthalate (PET) film (trade name “T-100”, manufactured by Mitsubishi Polyester Co., Ltd.) having a thickness of 38 μm was prepared. Also, 1 part by weight of a metal catalyst (trade name: SRX212, manufactured by Shin-Etsu Chemical Co., Ltd.) is blended with 100 parts by weight of a thermosetting silicone resin (trade name: LTC1056L, manufactured by Toray Dow Corning Silicone Co., Ltd.). Then, it was diluted with toluene to prepare a coating solution having a solid concentration of 80% by weight. The thermosetting silicone resin was mainly composed of polydimethylsiloxane having a vinyl group as a functional group.

  20 parts by weight of heat-expandable fine particles (trade name: heat-expandable microcapsule M330, manufactured by Dainichi Seika Co., Ltd.) were added to this coating solution and dispersed, and the mixture was dispersed on the support of the first release sheet. Coated uniformly. The coating was performed with a Mayer bar so that the layer thickness after drying was 11 μm. The thermally expandable fine particles had an average particle diameter of 11 μm and an expansion start temperature of 104 ° C. On the support of the second release sheet, the above-mentioned coating solution to which no thermally expandable fine particles were added was similarly applied so that the layer thickness after drying was 1 μm. The first and second release sheets coated with the coating liquid were dried at 90 ° C. for 1 minute, thereby forming the first and second release agent layers on the supports of the first and second release sheets. . In the drying step, toluene as a solvent was vaporized and the thermosetting silicone resin was cured by heating.

  Next, on the surface of the first release sheet on which the release agent layer is formed, an acrylic resin-based pressure-sensitive adhesive (trade name: BPS5127, manufactured by Toyo Ink Co., Ltd.) with a Meyer bar has a thickness of 30 μm. After coating as described above, it was dried at 90 ° C. for 2 minutes to form an adhesive layer. Next, the surface of the first release sheet on which the pressure-sensitive adhesive layer was laminated was bonded to the surface of the second release sheet on which the release agent layer was laminated, thereby obtaining the substrate-less double-sided pressure-sensitive adhesive sheet of Example 1. .

[Example 2]
In Example 2, the coating solution used to form the first and second release agent layers was a mixture of a silicone-modified alkyd resin and an amino resin (trade name. KS-882, manufactured by Shin-Etsu Chemical Co., Ltd.). To 100 parts by weight, 1 part by weight of p-toluenesulfonic acid was added and diluted with a toluene solution to obtain a coating solution having a solid content concentration of 50% by weight. In Example 2, since the configuration other than the coating solution for the release agent layer is the same as that in Example 1, other description is omitted.

[Comparative Example 1]
The base material-less double-sided pressure-sensitive adhesive sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that the first release agent layer was formed with a coating liquid to which no thermally expandable fine particles were added.

[Comparative Example 2]
The base material-less double-sided pressure-sensitive adhesive sheet of Comparative Example 2 was prepared in the same manner as in Example 2 except that the first release agent layer was formed with a coating liquid to which no thermally expandable fine particles were added.

  About each said base-material-less double-sided adhesive sheet, it evaluated as follows. The evaluation results are shown in Table 1.

(1) Peeling force In measuring the peeling force, a substrate-less double-sided PSA sheet having a width of 20 mm was used. Each substrate-less double-sided pressure-sensitive adhesive sheet was allowed to stand for 2 hours under conditions of 23 ° C. and 50% humidity, and then heated at 125 ° C. for 1 minute to expand the thermally expandable fine particles, and to the adhesive of the first and second release sheets. The peel force was measured respectively. Moreover, after leaving each base material-less double-sided adhesive sheet for 2 hours on 23 degreeC humidity 50%, it measures also about the peeling force with respect to the adhesive of a 1st peeling sheet, without heating (before microparticle expansion | swelling). did.

  In the measurement of peeling force, the second release sheet of each base-less double-sided pressure-sensitive adhesive sheet is fixed, the first release sheet is peeled off at a peeling angle of 180 °, and the speed is 0.3 m / min. The peel force with respect to was measured. And about the base material-less double-sided pressure-sensitive adhesive sheet from which the first release sheet has been peeled off, the surface on which the adhesive is exposed is attached to the SUS plate, the second release sheet is peeled off under the same conditions as the peeling of the first release sheet, 2 The peel strength of the release sheet to the adhesive was measured. The peeling force was calculated by averaging 3 times. In addition, it measured similarly about the peeling force of the 1st peeling sheet before fine particle expansion | swelling. Moreover, the peeling force of the 1st and 2nd peeling sheet was measured using the tensile testing machine.

(2) Peelability test Each substrate-less double-sided pressure-sensitive adhesive sheet was allowed to stand for 6 weeks at 40 ° C in dry conditions (humidity 0%), heated at 125 ° C for 1 minute, and then the same conditions as in the above peel force measurement method. The first release sheet was peeled off. When the first release sheet was peeled off, the presence or absence of peeling failure was evaluated by the presence or absence of transfer of the adhesive to the first release sheet side.

  As mentioned above, in Example 1 and Example 2 which mix | blended 20 weight part of thermally expansible fine particles, the peeling force of the 1st peeling sheet after a heating is made low compared with the peeling force of a 2nd peeling sheet. I was able to. And both the peeling force difference was 20 mN / 20 mm or more in any case, and since it was possible to produce a peeling force difference of a predetermined amount or more, no peeling failure occurred in the peelability test. Furthermore, in Example 1, it can be understood that even when the peeling force of the second release sheet is 200 mN / 20 mm or less and the peeling force on the heavy peeling side is relatively low, no peeling failure occurs.

  On the other hand, since Comparative Examples 1 and 2 did not contain thermally expandable fine particles, it was not possible to cause a difference in peel force between the first and second release sheets. Therefore, in the peelability test, poor peel occurred.

  Furthermore, in the present invention, as shown in Examples 1 and 2, even when the first and second release agent layers have the same release agent composition, a baseless double-sided pressure-sensitive adhesive sheet having good release properties can be obtained. I understand that. Thus, if the release agent composition on both release surfaces is the same, the release force on both release surfaces shows the same change over time, so the first and second release agent layers even after standing for a long time. The balance of the peeling force can be maintained, and by applying an external stimulus at the time of use, the first peeling sheet can be peeled without causing a peeling failure by reducing the peeling force of the first release agent layer.

It is typical sectional drawing which shows a base material less double-sided adhesive sheet. It is a typical sectional view for showing the composition of the 1st release agent layer. It is typical sectional drawing for showing the composition of the 1st release agent layer when an intermediate layer is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate-less double-sided adhesive sheet 11 Adhesive layer 12 Support body of 1st release sheet 13 Support body of 2nd release sheet 15 1st release agent layer 16 2nd release agent layer 20 Expandable fine particle 21 Intermediate layer 30 1st peeling Sheet 31 Second release sheet

Claims (9)

The first release sheet, the pressure-sensitive adhesive layer, the second release sheet is a substrate-less double-sided pressure-sensitive adhesive sheet laminated in this order,
The first release sheet has at least a support and a first release agent layer,
The first release agent layer is configured to contain a release agent and expandable fine particles that expand by an external stimulus of at least one of heat and active energy rays,
It said first release agent layer, by receiving the external stimulus, has a function of Ru lowers the peel force to the pressure-sensitive adhesive layer of the first release sheet, the release force after receiving the external stimulus, the second the substrate-less double-sided pressure-sensitive adhesive sheet, wherein lower spoil it than peel strength to the pressure-sensitive adhesive layer of the release sheet. The first release sheet, the pressure-sensitive adhesive layer, the second release sheet is a substrate-less double-sided pressure-sensitive adhesive sheet laminated in this order,
The first release sheet has at least a support and a first release agent layer,
The first release agent layer includes a release agent and a foaming agent,
The foaming agent has a shell wall and an inclusion substance included in the shell wall;
The first release agent layer receives the external stimulus of at least one of heat and active energy rays, thereby destroying the shell wall and releasing the vaporized inclusion substance to the outside. It has a function of reducing the peeling force of the release sheet to the pressure-sensitive adhesive layer, and the release force after receiving the external stimulus is made lower than the peel force of the second release sheet to the pressure-sensitive adhesive layer. Baseless double-sided pressure-sensitive adhesive sheet.   The expandable fine particle has a shell wall and an expandable substance that is contained in the shell wall and vaporizes when heated to a predetermined temperature or more, and expands the shell wall toward the outside. 2. The substrate-less double-sided pressure-sensitive adhesive sheet according to 1.   The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the expandable fine particles have an average particle size of 1 to 50 µm.   The base-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the expandable fine particles are 5 to 50 parts by weight with respect to 100 parts by weight of the polymer component of the release agent. The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein an average layer thickness of the first release agent layer is 0.5 to 15 µm. The second release sheet has at least a support and a second release agent layer,
The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein the first and second release agent layers each contain a release agent, and the polymer components of the release agents are the same. The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein a peeling force of the first release sheet before receiving an external stimulus is equal to or less than a peeling force of the second release sheet. Wherein the first between the release agent layer and the first release sheet is further laminated an intermediate layer, said multilayer laminated structure of the first release agent layer and the intermediate layer may contain the expansive particle or blowing agent The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein

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