JP5717320B2 - Re-peelable adhesive sheet - Google Patents

Description

  The present invention relates to a re-peelable pressure-sensitive adhesive sheet, and more particularly, an uncrosslinked rubber having an unsaturated bond in the molecule, particularly an ethylene-propylene-diene copolymer rubber, and the presence of certain polyfunctional monomers and polymer plasticizers. The present invention relates to a re-peelable pressure-sensitive adhesive sheet having a rubber-based pressure-sensitive adhesive layer excellent in heat resistance and re-peelability, which is formed by irradiating an active energy ray below and cross-linking.

Generally, it is known that rubber-based adhesives are inferior in heat resistance. This is because the main polymer rubber is not crosslinked.
Conventionally, sulfur crosslinking, quinoid crosslinking, phenol resin crosslinking, etc. are known as rubber crosslinking methods, but these methods require heating at high temperatures for a long time, and production efficiency in the production of pressure-sensitive adhesive sheets There are problems such as lacking. Moreover, when producing a thin film, it is difficult to obtain a uniform and homogeneous thin film by a high-temperature crosslinking method.
As a conventional technique, for example, (1) a crosslinking method of butyl rubber characterized in that at least three of quinoid, organic peroxide, and acrylic monomer coexist and a crosslinking reaction is performed (see Patent Document 1), (2) In the presence of an organic peroxide and a polyfunctional monomer containing an electron-withdrawing group, and in the absence of another crosslinking agent comprising quinoid or sulfur, the crosslinking reaction of uncrosslinked butyl rubber is performed. A characteristic butyl rubber crosslinking method (see Patent Document 2) is disclosed.
However, these methods all require high-temperature heating, and are not suitable for the production of a thin rubber crosslinked body. In particular, olefin rubbers such as butyl rubber and ethylene-propylene-diene copolymer rubber have low crosslinking efficiency and require a long time for the crosslinking process.
In addition, in order to improve the heat resistance of the rubber-based pressure-sensitive adhesive, there is a method of using a styrene-isoprene copolymer, but since it does not have a crosslinked structure, sufficient heat resistance is still obtained. Absent.

JP-A-62-74934 Japanese Patent No. 3197068

  The present invention has been made under such circumstances, and an object thereof is to provide a re-peelable pressure-sensitive adhesive sheet having a rubber-based pressure-sensitive adhesive layer excellent in heat resistance and re-peelability on a substrate.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
An uncrosslinked rubber material layer comprising an uncrosslinked rubber having an unsaturated bond in the molecule, an electron-withdrawing group-containing polyfunctional monomer, and a polymer plasticizer provided on a substrate is irradiated with active energy rays. It has been found that a re-peelable pressure-sensitive adhesive sheet having a rubber-based pressure-sensitive adhesive layer excellent in heat resistance and re-peelability can be obtained by crosslinking.
The present inventors have found that the uncrosslinked rubber having an unsaturated bond in the molecule is particularly effective when it is an olefin rubber such as an ethylene-propylene-diene copolymer rubber.
The present invention has been completed based on such findings.
That is, the present invention
(1) A re-peelable pressure-sensitive adhesive sheet having a base material and a pressure-sensitive adhesive layer having a gel fraction of 60% or more formed thereon, wherein the pressure-sensitive adhesive layer is (A) unsaturated bond in the molecule An uncrosslinked rubber material layer comprising: an uncrosslinked rubber having a molecular weight; (B) an electron-withdrawing group-containing polyfunctional monomer; and (C) a polymer plasticizer having a number average molecular weight of 15,000 to 35,000. (A) Uncrosslinked rubber having an unsaturated bond in the molecule polymerizes 0.01 to 15 mol% of a monomer that induces an unsaturated bond in the polymer chain. (B) an electron withdrawing group-containing polyfunctional monomer is a (meth) acrylic acid polyfunctional monomer, and (C) a polymer plasticizer is liquid isoprene or liquid butadiene.・ Isoprene or liquid styrene A Puren, uncrosslinked rubber material layer, (A) with respect to uncrosslinked rubber 100 parts by mass having an unsaturated bond in the molecule, (B) an electron-withdrawing group containing 2 to 30 parts by weight of a polyfunctional monomer, ( C) the removable pressure-sensitive sheet which comprises a polymeric plasticizer in an amount of 50 to 250 parts by weight, 及 beauty <br/> (2) an active energy ray is ultraviolet ray, uncrosslinked rubber material layer The re-peelable pressure-sensitive adhesive sheet according to item (1) , further comprising a photopolymerization initiator,
Is to provide.

  According to the present invention, an uncrosslinked rubber material layer comprising an uncrosslinked rubber having an unsaturated bond in a molecule, an electron withdrawing group-containing polyfunctional monomer, and a polymer plasticizer provided on a substrate, By cross-linking by irradiation with active energy rays, a re-peelable pressure-sensitive adhesive sheet having a rubber-based pressure-sensitive adhesive layer excellent in heat resistance and re-peelability can be provided.

  The re-peelable pressure-sensitive adhesive sheet of the present invention is a re-peelable pressure-sensitive adhesive sheet having a base material and a pressure-sensitive adhesive layer having a gel fraction of 50% or more formed thereon, wherein the pressure-sensitive adhesive layer comprises (A An uncrosslinked rubber material layer comprising an uncrosslinked rubber having an unsaturated bond in the molecule, (B) an electron-withdrawing group-containing polyfunctional monomer, and (C) a polymer plasticizer having a number average molecular weight of 3,000 or more. It is characterized by being cross-linked by irradiation with active energy rays.

[Base material]
Although the base material used for the re-peelable pressure-sensitive adhesive sheet of the present invention is not particularly limited, it is appropriately selected according to the purpose of use of the re-peelable pressure-sensitive adhesive sheet. For example, various types of paper such as fine paper, art paper, coated paper, glassine paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials, various synthetic papers, aluminum foil, copper foil and iron foil Porous materials such as metal foil, non-woven fabric, and the like, polyolefin resins such as polyethylene resin and polypropylene resin, polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin, acetate resin, ABS resin, polystyrene resin, vinyl chloride resin, etc. Examples thereof include a plastic film, a sheet, and a plastic film or sheet made of a mixture or laminate of these resins. A base material sheet such as a plastic film or sheet may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.

The substrate may be colored or colorless and transparent. Moreover, when using an adhesive sheet for the purpose of printing and printing, you may perform printing, printing, etc. Therefore, the base material may be provided with a heat-sensitive recording layer, a print image receiving layer capable of performing thermal transfer, ink jetting, laser printing, and the like, a printability improving layer, and the like.
Moreover, when a base material is a plastic, in order to improve adhesiveness with the adhesive layer provided on it, surface treatments, such as an oxidation method and a roughening method, can be given if desired. Examples of the oxidation method include, but are not limited to, corona discharge treatment method, plasma treatment method, chromic acid oxidation (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and the like. Is not particularly limited, and examples thereof include a sand blast method and a solvent treatment method. These surface treatment methods are appropriately selected according to the type of the substrate, but in general, the corona discharge treatment method is preferably used from the viewpoints of effects and operability. Moreover, primer treatment can also be performed.

Depending on the type of base material, a sealing layer may be provided between the base material and the pressure-sensitive adhesive layer as desired. In addition to preventing the adhesive from penetrating into the base material, this sealing layer is used for the purpose of further improving the adhesion between the base material and the adhesive layer. It is provided for the purpose of giving. Such a sealing layer is not particularly limited, but for example, a styrene-butadiene copolymer, an acrylic resin, a polyester resin, a polyurethane resin, a polystyrene resin, etc. as a main component, and if necessary, clay And a layer made of a filler added with a filler such as silica, calcium carbonate, titanium oxide, and zinc oxide. The thickness of the sealing layer is not particularly limited, but is usually in the range of 0.1 to 30 μm.
The thickness of the substrate is not particularly limited, but is usually about 10 to 250 μm.

[(A) Uncrosslinked rubber having an unsaturated bond in the molecule]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, the uncrosslinked rubber having a saturated bond in the molecule used as the component (A) of the uncrosslinked rubber material layer is not particularly limited. For example, natural rubber, isoprene rubber, butadiene rubber, ethylene -Propylene-diene copolymer rubber (EPDM rubber), fluoro rubber, urethane rubber, butyl rubber, styrene-isoprene copolymer, styrene-butadiene copolymer, styrene-butadiene-butylene-styrene copolymer, styrene-isobutylene-styrene Examples include copolymers, styrene-isoprene-styrene copolymers, styrene-butadiene-styrene copolymers, chloroprene rubber, and acrylic rubber. Furthermore, the incomplete hydrogenated product of the styrene-isoprene-styrene copolymer, the incomplete hydrogenated product of styrene-butadiene-styrene copolymer, or the like can be used. These uncrosslinked rubbers may be used alone or in combination of two or more. Among these, natural rubber having an unsaturated bond in its molecule, isoprene rubber, butadiene rubber, EPDM rubber, butyl rubber, styrene-isoprene copolymer, styrene-butadiene copolymer, styrene-butadiene-butylene-styrene copolymer Styrene-isoprene-styrene copolymer and styrene-butadiene-styrene copolymer are preferable.
In the present invention, the uncrosslinked rubber is preferably a copolymer obtained by polymerizing about 0.01 to 20 mol% of a monomer that induces an unsaturated bond in the polymer chain, and is preferably about 0.01 to 15 mol%. A copolymer obtained by polymerization is more preferable. Specifically, olefin rubbers such as butyl rubber and ethylene-propylene-diene copolymer rubber (EPDM rubber) having an unsaturated bond of about 0.01 to 20 mol% in the molecule are preferable, and EPDM rubber is particularly preferable. is there.
Examples of the monomer that induces the unsaturated bond include isoprene, 1,3-butadiene, ethylidene norbornene, 1,4-hexadiene, and dicyclopentadiene, and ethylidene norbornene, 1,4-hexadiene, and dicyclopentane are particularly preferable. It is.

[(B) Electron withdrawing group-containing polyfunctional monomer]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, an electron-withdrawing group-containing polyfunctional monomer is used as the component (B) of the uncrosslinked rubber material layer. Examples of the electron withdrawing group in the polyfunctional monomer include groups such as —NO ₂ , —CN, —COR (R represents an alkyl group; the same applies hereinafter), —CONR ₂ , —CONHR, —COOR and the like. it can.
The electron withdrawing group is preferably in the vicinity of a carbon-carbon double bond (hereinafter referred to as a functional double bond) of the functional group in the polyfunctional monomer, and in particular, directly on the carbon atom constituting the functional double bond. Bonding is preferred.
Although there is no restriction | limiting in particular in the electron withdrawing group containing polyfunctional monomer used by this invention, From viewpoints, such as availability and reactivity, a (meth) acrylic-acid type polyfunctional monomer is preferable.

((Meth) acrylic acid polyfunctional monomer)
Examples of the (meth) acrylic acid-based polyfunctional monomer include tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, ethylene oxide-added bisphenol A di (meth) acrylate, and propylene oxide-added bisphenol A di (meta). ) Acrylate, 1,10-decanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, ethylene oxide-added 2-methyl-1,3-propanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, propylene oxide / ethylene oxide-added bisphenol A di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonane Di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ethylene oxide-added isocyanuric acid tri (meth) acrylate, ethylene oxide-added trimethylolpropane tri (meth) ) Acrylate, trimethylolpropane tri (meth) acrylate, propylene oxide-added trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ethylene oxide-added pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate , Propylene oxide-added pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate , Cyclohexanedimethanol di (meth) acrylate, ethylene oxide addition cyclohexanedimethanol di (meth) acrylate and ethylene oxide addition glycerin tri (meth) acrylate. In addition, (meth) acrylate means both acrylate and methacrylate.
In the present invention, these (meth) acrylic acid polyfunctional monomers may be used alone or in combination of two or more.

  In the present invention, the use ratio of the uncrosslinked rubber of the component (A) and the electron-withdrawing group-containing polyfunctional monomer of the component (B) is not particularly limited, and the required performance of the releasable adhesive sheet, Although selection may be made as appropriate in consideration of compatibility with the component (A) such as butyl rubber or EPDM rubber, the electron withdrawing of the component (B) is usually performed with respect to 100 parts by mass of the uncrosslinked rubber of the component (A). The group-containing polyfunctional monomer is used at a ratio of about 0.5 to 50 parts by mass, preferably 1 to 40 parts by mass, more preferably 2 to 30 parts by mass.

[(C) Polymer plasticizer]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, a polymer plasticizer having a number average molecular weight of 3,000 or more is used as the component (C) of the uncrosslinked rubber material layer. When the number average molecular weight is less than 3,000, problems such as transfer to the adherend occur. Examples of such polymer plasticizers include liquid isoprene, liquid butadiene, liquid butadiene / isoprene, liquid styrene / butadiene, liquid styrene / isoprene, polybutene, polyisobutylene, liquid terpene, liquid rosin, and paraffinic oil. Those obtained by hydrogenation are preferred, but not particularly limited. Moreover, it may or may not have a reactive functional group such as hydrosilylation, carboxylation, or methacrylate. The number average molecular weight is preferably 15,000 to 35,000. In this invention, the said polymeric plasticizer may be used individually by 1 type, and may be used in combination of 2 or more type.

In the present invention, the polymer plasticizer of the component (C) is usually about 30 to 300 parts by mass, preferably 50 to 250 parts by mass with respect to 100 parts by mass of the uncrosslinked rubber of the component (A). More preferably, it is used in a proportion of 100 to 200 parts by mass. When the amount of the component (C) is less than 30 parts by mass, the uncrosslinked rubber of the component (A) cannot be sufficiently plasticized, and is inferior in stickiness and the like. May be contaminated, making it difficult to obtain removability.
The number average molecular weight of the polymer plasticizer is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

[Photopolymerization initiator]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, an uncrosslinked rubber material layer is crosslinked by irradiation with active energy rays to form a rubber-based pressure-sensitive adhesive layer. From the viewpoint of economy and the like, ultraviolet rays are preferably used.
When ultraviolet rays are used as the active energy rays, a photopolymerization initiator can be used as necessary. In addition, when using an electron beam, it is not necessary to use a photoinitiator.
In the present invention, the photopolymerization initiator that can be used is not particularly limited. For example, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy 2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy- 1- [4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl] -2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2- Morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] Alkylphenone-based photopolymerization initiators such as -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethyl) Acylphosphine oxide photopolymerization initiators such as benzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis [2,6-difluoro-3- (1H-pyrrole-1- Yl) -phenyl] titanium and other titanocene-based photopolymerization initiators, 1,2-octanedione-1- [4- (phenylthio) -2- (O-benzoyloxime)], ethanone-1- [9-ethyl- Oxime ester photopolymerization initiators such as 6- (2-methylbenzoyl) -9H-carbazol-3-yl] -1- (O-acetyloxime), benzophenone, p-chloroben Phenone, benzoylbenzoic acid, methyl o-benzoylbenzoate, 4-methylbenzophenone, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 3,3'-dimethyl-4 Benzophenone photopolymerization initiators such as -methoxybenzophenone, 2,4,6-trimethylbenzophenone, 4- (13-acryloyl-1,4,7,10,13-pentaoxatridecyl) -benzophenone, thioxanthone, 2- Chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-methylthioxanthone, 2-isopropyl Examples thereof include thioxanthone photopolymerization initiators such as thioxanthone and 4-isopropylthioxanthone.

These photoinitiators may be used individually by 1 type, and may be used in combination of 2 or more type. The photopolymerization initiator may be used in combination with a photopolymerization initiation assistant such as triisopropanolamine or 4,4′-diethylaminobenzophenone.
The amount of the photopolymerization initiator used is usually from 0.001 to 30 parts by mass, preferably from 0.01 to 100 parts by mass, based on 100 parts by mass (solid content) of the above-mentioned uncrosslinked rubber (A), as the solid content. It is selected in the range of 20 parts by mass. When the amount of the photopolymerization initiator used is less than 0.001 part by mass, sufficient crosslinking cannot be performed. On the other hand, when the amount exceeds 30 parts by mass, decomposition of the main skeleton of the uncrosslinked rubber of component (A) occurs when irradiated with ultraviolet rays. Is promoted.

[Other ingredients]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, a tackifier can be added to the uncrosslinked rubber material layer as necessary for the purpose of imparting better adhesive performance.
There are no particular restrictions on the type of tackifier, such as rosin derivatives, polyterpene resins, aromatic modified terpene resins and their hydrides, terpene phenol resins, coumarone-indene resins, aliphatic petroleum resins, aromatic petroleum resins and Examples thereof include a hydride, a low molecular weight polymer of styrene or substituted styrene. This tackifier may be used individually by 1 type, and may be used in combination of 2 or more type. What is necessary is just to select the content of the said tackifier suitably according to the desired performance of a re-peelable pressure-sensitive adhesive sheet.
In addition, conventionally known additives such as antioxidants, ultraviolet absorbers, light stabilizers, inorganic / organic fillers, colorants, preservatives, and rust preventives can be appropriately added as long as the performance is not deteriorated. .

[Coating agent for forming uncrosslinked rubber material layer]
In the present invention, the above-mentioned uncrosslinked rubber of component (A), an electron-withdrawing group-containing polyfunctional monomer of component (B), a polymer plasticizer of component (C), and a photopolymerization initiator used as necessary And a coating agent for forming an uncrosslinked rubber material layer containing a predetermined proportion of other additive components. In addition, in preparation of this coating agent, you may carry out without a solvent and can contain a suitable solvent suitably as needed.

[Method for producing adhesive sheet]
The method for producing the re-peelable pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, when the non-crosslinked rubber material layer forming coating agent is solvent-free, the viscosity is reduced by heating, applied to one surface of the substrate by hot melt, and solidified by cooling to form an uncrosslinked rubber material layer. Let it form. Further, when the coating agent is diluted with a solvent and is in a liquid state, a conventionally known application means such as a knife coater, a roll coater, a roll knife coater, an air knife coater, a bar coater, An uncrosslinked rubber material layer is formed by applying and drying with a die coater, curtain coater, gravure coater or the like.
The thickness of the uncrosslinked material layer is not particularly limited, and is usually 1 to 200 μm, preferably 10 to 100 μm.

In the present invention, the non-crosslinked rubber material layer thus formed on the base material is irradiated with active energy rays to crosslink the material to form a rubber-based pressure-sensitive adhesive layer. As the active energy ray, ultraviolet rays are preferably used as described above. Ultraviolet rays are obtained with a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or the like. For example, in the case of ultraviolet rays, the irradiation amount of the active energy ray is about 100 to 5000 mJ / cm ² in terms of the amount of light. If necessary, a release sheet may be pasted on the uncrosslinked rubber material layer in order to protect the uncrosslinked rubber material layer. Alternatively, the base material may be laminated on the uncrosslinked rubber material layer after the coating agent for forming the uncrosslinked rubber material layer is applied onto the release sheet at an appropriate thickness and dried.
This active energy ray may be irradiated directly on the surface of the uncrosslinked rubber material layer, or may be irradiated through the substrate. Further, when the uncrosslinked rubber material layer has a release sheet to be described later, it may be irradiated through the release sheet. In this case, it is preferable that the substrate and the release sheet have transparency to the wavelength of the active energy ray. That is, when an electron beam is used as the energy beam, it may be opaque, and when an ultraviolet beam is used as the energy beam, it preferably has ultraviolet transparency. Moreover, when a base material has permeability | transmittance with respect to the wavelength of an active energy ray, you may irradiate an active energy ray from the base material side.
In the present invention, by irradiation with such active energy rays, the uncrosslinked rubber material layer forms a rubber-based pressure-sensitive adhesive layer having a gel fraction of 50% or more. When this gel fraction is 50% or more, when the obtained pressure-sensitive adhesive sheet is peeled off, a pressure-sensitive adhesive sheet is obtained which is less likely to cause adhesive residue, has excellent removability, and has good heat resistance. A preferable gel fraction is 60% or more. A method for measuring the gel fraction will be described in detail later.

[Peeling sheet]
In the re-peelable pressure-sensitive adhesive sheet of the present invention, a release sheet can be provided as desired on the rubber-based pressure-sensitive adhesive layer formed in this way. As this release sheet, for example, high-density base paper such as glassine paper, clay coated paper, kraft paper, laminated paper obtained by laminating polyethylene resin etc., or plastic such as polyethylene terephthalate, polyethylene naphthalate, polyolefin, etc. Examples thereof include a film in which a release agent such as a fluororesin or a silicone resin is applied to a dry mass of about 0.1 to 3 g / m ² and a release layer is provided by heat curing or ultraviolet curing. Although there is no restriction | limiting in particular about the thickness of this peeling layer, Usually, it is the range of 25-200 micrometers.

[Use of re-peelable adhesive sheet]
Specific uses of the re-peelable pressure-sensitive adhesive sheet include, for example, office use, logistics management labels for products, etc., for labels that can be repeatedly applied.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the gel fraction of the rubber-type adhesive layer obtained by each example and the adhesive sheet, adhesive force and holding power, and removability were measured according to the method shown below.
<Method for measuring gel fraction>
1) The mass of the SUS wire mesh is measured.
2) The re-peelable pressure-sensitive adhesive sheet is sandwiched between SUS wire nets and the mass is measured.
3) Immerse in toluene at 23 ° C. for 120 hours.
4) Take out a test piece with a wire mesh, dry under vacuum at 120 ° C. for 2 hours, and measure the mass after drying.
5) The gel fraction (%) is calculated from the following formula.
(Mass after drying−Mass of wire mesh) × 100 / (Mass before drying−Mass of wire mesh)
<Measurement method of adhesive strength>
The pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet is affixed to a stainless steel plate in an environment of 23 ° C. and 50% RH, and after 24 hours, in that environment, a 180 ° peel test is performed in accordance with JIS Z 0237 to measure the adhesive strength. did.
<Measurement method of holding power>
The adhesive layer side of the adhesive sheet is attached to a stainless steel plate so that the area is 25 mm × 25 mm, and a load of 9.8 N is applied in a 40 ° C. environment to measure the holding force of JIS Z 0237. In accordance with this, the time to fall was measured (maximum 70,000 seconds).
<Removability>
The pressure-sensitive adhesive sheet was affixed to a melamine-coated plate in an environment of 23 ° C. and 50% RH and left for 30 minutes. Next, it promoted for 168 hours in 70 degreeC atmosphere. Then, after leaving it to stand at 23 ° C. and 50% RH for 24 hours, the test piece was peeled off under the same environment, and the peelability of the peeled melamine coated plate was visually evaluated according to the following criteria.
A: Adhesive residue is observed in less than 2% of the sticking area.
B: Adhesive residue is observed in 2% or more and less than 10% of the pasting area.
C: Adhesive residue is seen in 10% or more of the pasting area.

Example 1
(1) Preparation of coating agent for forming uncrosslinked rubber material layer (A) As component, ethylene-propylene-diene copolymer rubber [manufactured by JSR, product name “JSR EP43”, polymerization ratio of monomer for inducing unsaturated bond 0 0.01 mol%] 100 parts by mass (solid content), 6 parts by mass (solid content) of benzophenone [manufactured by Tokyo Chemical Industry Co., Ltd.] as a photopolymerization initiator, and trimethylolpropane tri as an electron withdrawing group-containing polyfunctional monomer 10 parts by mass of acrylate [manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “NK Ester A-TMPT”] and liquid isoprene resin [manufactured by Kuraray Co., Ltd., trade name “Kuraprene LIR-200”, number average molecular weight: 25,000] 100 parts by mass (solid content) and toluene as a diluent solvent are added so as to have a solid content of 20% by mass, mixed and uncrosslinked rubber material layer The formation for the coating agent was prepared.
(2) Preparation of pressure-sensitive adhesive sheet The coating agent prepared in (1) above was applied onto a release sheet [manufactured by Lintec, trade name “SP-8LK2”] so that the thickness after drying was 25 μm, and 90 ° C. Then, after drying for 1 minute to form an uncrosslinked rubber material layer, ultraviolet light was irradiated from the surface of the material layer side (light quantity 200 mJ / cm ² ). Then, it was bonded to a polyethylene terephthalate film having a thickness of 50 μm to produce an adhesive sheet. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Example 2
In Example 1, the same operation as in Example 1 was performed except that the polymer plasticizer was a liquid isoprene resin [manufactured by Kuraray Co., Ltd., trade name “Kuraprene LIR-290”, number average molecular weight: 25,000] An adhesive sheet was prepared. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Example 3
In Example 1, the addition amount of the polymer plasticizer was 90 parts by mass (solid content), and an alicyclic saturated hydrocarbon resin [trade name “Arcon P-100” manufactured by Arakawa Chemical Industries, Ltd.] as a tackifier was used. Except for adding 10 parts by mass, the same operation as in Example 1 was performed to prepare an adhesive sheet. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Example 4
In Example 1, the amount of the polymer plasticizer added was 70 parts by mass (solid content), and an alicyclic saturated hydrocarbon resin [trade name “Arcon P-100” manufactured by Arakawa Chemical Industries, Ltd.] as a tackifier was used. Except for adding 30 parts by mass, the same operation as in Example 1 was performed to prepare an adhesive sheet. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Comparative Example 1
In Example 1, except for not irradiating ultraviolet rays, the same operation as Example 1 was performed, and the adhesive sheet was produced. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Comparative Example 2
In Example 2, an adhesive sheet was prepared by performing the same operation as in Example 1 except that ultraviolet rays were not irradiated. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Comparative Example 3
In Example 3, a pressure-sensitive adhesive sheet was prepared by performing the same operation as in Example 1 except that ultraviolet rays were not irradiated. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Comparative Example 4
In Example 4, a pressure-sensitive adhesive sheet was prepared by performing the same operation as in Example 1 except that ultraviolet rays were not irradiated. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.

Comparative Example 5
In Example 1, a liquid polybutene resin [manufactured by Nippon Oil Corporation, trade name “Nisseki Polybutene LV-25”, number average molecular weight: 390] was used as a plasticizer. This was done to prepare an adhesive sheet. About this adhesive sheet, the gel fraction, adhesive force, holding power, and removability were measured. The results are shown in Table 2.
The blending compositions of Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 1.

[note]
A-1: Ethylene-propylene-diene copolymer rubber [manufactured by JSR, trade name “JSR EP43”]
B-1: Benzophenone [manufactured by Tokyo Chemical Industry Co., Ltd.]
C-1: Trimethylolpropane triacrylate [manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “NK Ester A-TMPT”]
D-1: Liquid isoprene resin [manufactured by Kuraray Co., Ltd., trade name “Kuraprene LIR-200”]
D-2: Liquid isoprene resin [manufactured by Kuraray Co., Ltd., trade name “Kuraprene LIR-290”]
D-3: Liquid polybutene resin [manufactured by Nippon Oil Corporation, trade name “Nisseki Polybutene LV-25”]
E-1: Alicyclic saturated hydrocarbon resin [Arakawa Chemical Industries, trade name “Arcon P-100”]

As can be seen from Table 2, the pressure-sensitive adhesive sheets of the present invention obtained in Examples 1 to 4 each have a gel fraction of more than 60%, excellent holding power, and moderate pressure. The removability is A rank and excellent.
On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 5 all have a gel fraction of less than 50%, and cohesive failure occurs in the measurement of holding power. Moreover, in the measurement of adhesive force, cohesive failure or transfer occurs, and the removability is bad at C rank.

  The re-peelable pressure-sensitive adhesive sheet of the present invention is an uncrosslinked rubber comprising an uncrosslinked rubber having an unsaturated bond in the molecule, an electron withdrawing group-containing polyfunctional monomer, and a polymer plasticizer provided on a substrate. The pressure-sensitive adhesive sheet is excellent in heat resistance and removability, in which a rubber-based pressure-sensitive adhesive layer is formed by irradiating a material layer with active energy rays.

Claims (2)

A re-peelable pressure-sensitive adhesive sheet having a base material and a pressure-sensitive adhesive layer having a gel fraction of 60% or more formed thereon, wherein the pressure-sensitive adhesive layer has (A) an unsaturated bond in the molecule. An uncrosslinked rubber material layer containing a crosslinked rubber, (B) an electron-withdrawing group-containing polyfunctional monomer, and (C) a polymer plasticizer having a number average molecular weight of 15,000 to 35,000 is irradiated with active energy rays. , Which is cross-linked,
(A) Uncrosslinked rubber having an unsaturated bond in the molecule is an ethylene-propylene-diene copolymer rubber obtained by polymerizing 0.01 to 15 mol% of a monomer that induces an unsaturated bond in the polymer chain,
(B) The electron-withdrawing group-containing polyfunctional monomer is a (meth) acrylic acid polyfunctional monomer,
(C) The polymer plasticizer is liquid isoprene, liquid butadiene / isoprene or liquid styrene / isoprene,
The uncrosslinked rubber material layer comprises (A) 2 to 30 parts by mass of an electron withdrawing group-containing polyfunctional monomer with respect to 100 parts by mass of the uncrosslinked rubber having an unsaturated bond in the molecule, and (C) a polymer A re-peelable pressure-sensitive adhesive sheet comprising a plasticizer in a proportion of 50 to 250 parts by mass . The releasable pressure-sensitive adhesive sheet according to claim 1 , wherein the active energy ray is ultraviolet light, and the uncrosslinked rubber material layer further contains a photopolymerization initiator.