JP6145568B2 - Adhesive and adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive and an adhesive sheet that can be used for a touch panel and the like.

  Various mobile electronic devices such as mobile phones and tablet terminals in recent years include a display using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. Is increasingly becoming a touch panel.

  In the display as described above, a protective panel is usually provided on the surface side of the display module. With the reduction in thickness and weight of electronic devices, the protective panel has been changed from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate.

  Here, a gap is provided between the protection panel and the display module so that the deformed protection panel does not collide with the display module even when the protection panel is deformed by an external force.

  However, if there is a gap as described above, that is, an air layer, the difference in refractive index between the protective panel and the air layer, and the reflection loss of light due to the difference in refractive index between the air layer and the display module is large. There is a problem that the image quality deteriorates.

  Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer. However, a frame-like printed layer may exist as a step on the display module side of the protective panel. If the pressure-sensitive adhesive layer does not follow the step, the pressure-sensitive adhesive layer floats in the vicinity of the step, thereby causing light reflection loss. For this reason, the pressure-sensitive adhesive layer is required to have a step following ability.

In order to solve the above-described problem, Patent Document 1 discloses that the shear storage elastic modulus (G ′) at 25 ° C. and 1 Hz is 1.0 as an adhesive layer that fills the gap between the protective panel and the display module. × is at 10 5 ^Pa or less, and a gel fraction discloses a pressure-sensitive adhesive layer is 40% or more.

JP 2010-97070 A

  In patent document 1, it is going to improve level | step difference followability by making low the storage elastic modulus at the time of normal temperature in an adhesive layer. However, when the storage elastic modulus at normal temperature is lowered as described above, the storage elastic modulus at high temperature is unnecessarily lowered, causing a problem under durability conditions. For example, when high-temperature and high-humidity conditions are applied, bubbles may be generated near the step, or outgas may be generated from the plastic plate, which is a protective panel, and blisters such as bubbles, floats, and peeling may occur. To do. On the other hand, when the pressure-sensitive adhesive layer is hardened in order to improve the blister resistance, the step following ability is lowered.

  This invention is made | formed in view of the above actual conditions, and it aims at providing the adhesive and adhesive sheet which are excellent in both blister resistance and level | step difference followability.

  In order to achieve the above object, first, the present invention comprises (meth) acrylic acid ester polymer (A) containing 8 to 30% by mass of a monomer having a reactive functional group as a monomer unit constituting the polymer. And an adhesive composition containing an abietic acid ester-based tackifying liquid (B), wherein the pressure-sensitive adhesive has a gel fraction of 30 to 95%. Provided (Invention 1)

  In the said invention (invention 1), the wettability improvement effect by an abietic acid ester-type tackifying liquid (B), the reactive functional group of an (meth) acrylic acid ester polymer (A), and an abietic acid ester-type tackifying Due to the interaction of the ionic liquid (B), the adhesiveness of the adhesive to the adherend is improved and the blister resistance is excellent. In addition, the pressure-sensitive adhesive does not need to be hardened to improve blister resistance, and the gel fraction is within the above range, so that the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is excellent in step following ability. .

  In the said invention (invention 1), the said (meth) acrylic acid ester polymer (A) contains the hard monomer whose glass transition temperature as a homopolymer is 70 degreeC or more as a monomer unit which comprises the said polymer. Is preferred (Invention 2).

  In the said invention (invention 1 and 2), it is preferable that the said (meth) acrylic acid ester polymer (A) contains 2-ethylhexyl (meth) acrylate as a monomer unit which comprises the said polymer (invention). 3).

  In the said invention (invention 1-3), it is preferable that the weight average molecular weights of the said (meth) acrylic acid ester polymer (A) are 200,000-1,200,000 (invention 4).

  In the said invention (invention 1-4), it is preferable that the said adhesive composition contains a crosslinking agent (C) further (invention 5).

  Secondly, the present invention includes two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets, and the adhesive layer is the adhesive. A pressure-sensitive adhesive sheet comprising (Inventions 1 to 5) is provided (Invention 6).

  In the said invention (invention 6), it is preferable that the said adhesive layer is arrange | positioned between two patterned transparent conductive films, or between the patterned transparent conductive film, and a cover material or a display body module ( Invention 7).

  The pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention are excellent in both blister resistance and step followability.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing which shows one structural example of a touchscreen.

Hereinafter, embodiments of the present invention will be described.
[Adhesive]
The pressure-sensitive adhesive according to this embodiment contains a (meth) acrylic acid ester polymer (8) to 30% by mass of a monomer having a reactive functional group (reactive functional group-containing monomer) as a monomer unit constituting the polymer ( A pressure-sensitive adhesive obtained by crosslinking a pressure-sensitive adhesive composition containing A) and an abietic acid ester-based tackifying liquid (B) (hereinafter sometimes referred to as “pressure-sensitive adhesive composition P”), The fraction is 30 to 95%. The adhesive composition P preferably further contains a crosslinking agent (C).

  In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  The abietic acid ester-based tackifier liquid (B) is liquid at room temperature. The pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition P containing the abietic acid ester-based tackifying liquid (B) has improved wettability and improved adhesion to the adherend. In addition, the (meth) acrylic acid ester polymer (A) contains a relatively large amount of the reactive functional group-containing monomer as a monomer unit constituting the polymer as described above, so that the reactive functional group and abietin Interaction with the acid ester-based tackifying liquid (B) occurs, and the adhesion to the adherend is further improved. Thereby, the adhesive layer which consists of the said adhesive becomes the thing excellent in blister resistance. In addition, the pressure-sensitive adhesive does not need to be hardened to improve blister resistance, and the gel fraction is within the above range, so that the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is excellent in step following ability. . In other words, according to the pressure-sensitive adhesive according to the present embodiment, it is possible to achieve both the blister resistance and the step following ability that are normally in a trade-off relationship.

  Therefore, as an example, when the pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive is applied to the surface on the side where the level difference of the plastic plate is present, the pressure-sensitive adhesive layer follows the level difference, so there are no floating or bubbles in the vicinity of the level difference. It will be a thing. In addition, even when the laminate of the pressure-sensitive adhesive layer and the plastic plate is in a durable condition, generation of bubbles or the like in the vicinity of the step is suppressed, and even if outgas is generated from the plastic plate, bubbles, floats, Generation | occurrence | production of blisters, such as peeling, is suppressed.

(1) (Meth) acrylic acid ester polymer (A)
The reactive functional group-containing monomer contained in the (meth) acrylic acid ester polymer (A) as a monomer unit constituting the polymer includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer) and a carboxyl in the molecule. Preferred examples include a monomer having a group (carboxyl group-containing monomer) and a monomer having an amino group in the molecule (amino group-containing monomer). Among these, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferable, and a hydroxyl group-containing monomer is particularly preferable. By using a hydroxyl group-containing monomer, in particular, by using a combination of a hydroxyl group-containing monomer and an isocyanate-based crosslinking agent as a crosslinking agent (C) described later, the resulting adhesive has more excellent blister resistance. It becomes.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate in terms of reactivity with the crosslinking agent (C) of the hydroxyl group in the obtained (meth) acrylic acid ester polymer (A) and copolymerization with other monomers. Is preferred. These may be used alone or in combination of two or more.

  Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Of these, acrylic acid is preferred from the viewpoint of the reactivity of the resulting (meth) acrylic acid ester polymer (A) with the crosslinking agent (C) of the carboxyl group and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

  Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  As described above, the (meth) acrylic acid ester polymer (A) contains 8 to 30% by mass of a reactive functional group-containing monomer as a monomer unit constituting the polymer. When the content of the reactive functional group-containing monomer is less than 8% by mass, the interaction with the abietic acid ester-based tackifying liquid (B) hardly occurs, and the resulting pressure-sensitive adhesive is inferior in blister resistance. . On the other hand, when the content of the reactive functional group-containing monomer exceeds 30% by mass, desired tackiness cannot be obtained.

  When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content is preferably 10 to 25% by mass, In particular, the content is preferably 15 to 20% by mass. Moreover, when a (meth) acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content thereof is 8 to 25% by mass. It is preferable that it is 10-15 mass% especially.

  Here, when the touch panel or the like is placed in a high-temperature and high-humidity environment, moisture enters the pressure-sensitive adhesive layer, and when the touch panel or the like returns to room temperature, the pressure-sensitive adhesive layer is whitened and transparency is reduced. There is a problem of "humid heat whitening". When the (meth) acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above range, a predetermined amount of the reactive functional group remains in the pressure-sensitive adhesive layer. The reactive functional group is usually a hydrophilic group, and when such a hydrophilic group is present in the pressure-sensitive adhesive layer in a predetermined amount, even when the pressure-sensitive adhesive layer is placed under high-temperature and high-humidity conditions, The compatibility with the moisture that has entered the pressure-sensitive adhesive layer below is good, and as a result, whitening of the pressure-sensitive adhesive layer is suppressed, and the pressure-sensitive adhesive layer is excellent in resistance to moist heat whitening.

  The (meth) acrylic acid ester polymer (A) preferably contains a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. Thereby, the obtained adhesive can express preferable adhesiveness. In addition, the below-mentioned hard monomer is removed from the (meth) acrylic acid alkyl ester.

  Examples of the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, ( N-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate , Myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving adhesiveness, (meth) acrylic acid esters having 1 to 8 carbon atoms in the alkyl group are preferable, and n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are particularly preferable. More preferred is 2-ethylhexyl (meth) acrylate. According to (meth) acrylic acid 2-ethylhexyl, the dielectric constant of the obtained adhesive can be lowered and the response accuracy of the touch panel can be improved. In addition, these may be used independently and may be used in combination of 2 or more type.

  The (meth) acrylic acid ester polymer (A) contains 30 to 90% by mass of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. The content is preferably 40 to 75% by mass, more preferably 50 to 65% by mass.

  Further, the (meth) acrylic acid ester polymer (A) preferably contains a hard monomer having a glass transition temperature (Tg) as a homopolymer of 70 ° C. or more as a monomer unit constituting the polymer. By including the hard monomer as a monomer unit constituting the (meth) acrylic acid ester polymer (A), the resulting pressure-sensitive adhesive has improved cohesive force and is more excellent in blister resistance. In particular, when 2-ethylhexyl (meth) acrylate is used as the monomer unit constituting the (meth) acrylic acid ester polymer (A), the cohesive force tends to be low, so the hard monomer is used. It is preferable. The glass transition temperature (Tg) as a homopolymer of the hard monomer is preferably 75 to 200 ° C, and particularly preferably 80 to 180 ° C.

  Examples of the hard monomer include methyl methacrylate (Tg 105 ° C.), isobornyl acrylate (Tg 94 ° C.), isobornyl methacrylate (Tg 180 ° C.), acryloylmorpholine (Tg 145 ° C.), adamantyl acrylate (Tg 115 ° C.), and adamantyl methacrylate. (Tg 141 ° C.), dimethylacrylamide (Tg 89 ° C.), acrylamide (Tg 165 ° C.) and the like. These may be used alone or in combination of two or more.

  Among the hard monomers, methyl methacrylate, isobornyl acrylate and acryloyl morpholine are more preferable from the viewpoint of exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesion and transparency, and methacrylic acid. Methyl is particularly preferred.

  The (meth) acrylic acid ester polymer (A) preferably contains 10 to 45% by mass of the hard monomer as a monomer unit constituting the polymer, and particularly preferably contains 15 to 30% by mass. By containing the hard monomer in an amount of 10% by mass or more, an effect of improving blister resistance by the monomer unit can be expected. On the other hand, by setting the hard monomer content to 45% by mass or less, the relative shortage of other monomer units in the (meth) acrylic acid ester polymer (A) is prevented, and the pressure-sensitive adhesive obtained The adhesiveness and the step following ability can be made excellent.

  The (meth) acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. The other monomer is preferably a monomer that does not contain a reactive functional group so as not to interfere with the action of the reactive functional group-containing monomer. Such other monomers include, for example, (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and aliphatic rings such as cyclohexyl (meth) acrylate (meta ) Acrylic acid ester, (meth) acrylic acid N, N-dimethylaminoethyl, (meth) acrylic acid N, N-dimethylaminopropyl, etc. (meth) acrylic acid ester having acetic acid tertiary amino group, acetic acid Examples include vinyl and styrene. These may be used alone or in combination of two or more.

  The polymerization mode of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 200,000 to 1,200,000, particularly preferably 300,000 to 900,000, and more preferably 400,000 to 700,000. . In addition, the weight average molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  When the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is within a relatively low range as described above, a pressure-sensitive adhesive excellent in both blister resistance and step followability can be obtained. When the weight average molecular weight of the (meth) acrylate polymer (A) is less than 200,000, the blister resistance may be deteriorated, and the weight average molecular weight of the (meth) acrylate polymer (A) is 1,200,000. If it exceeds, step following ability may be deteriorated.

  In the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used singly or in combination of two or more.

(2) Abietic acid ester-based tackifying liquid (B)
The abietic acid ester-based tackifying liquid (B) in the present embodiment is an abietic acid ester having a melting point of 20 ° C. or lower. As a result, the abietic acid ester-based tackifying liquid (B) becomes a liquid at room temperature and is based on the above-described wettability improving action and interaction with the reactive functional group of the (meth) acrylic acid ester polymer (A). Adhesion improvement effect is produced and excellent blister resistance is achieved. From this viewpoint, the melting point of the abietic acid ester-based tackifying liquid (B) is preferably 0 ° C. or lower.

  As the abietic acid ester tackifying liquid (B) having the above melting point, for example, “Pine Crystal ME-G” (trade name) manufactured by Arakawa Chemical Industries, Ltd. can be used. In addition, 1 type may be used independently for an abietic acid ester-type tackifying liquid (B), and it may be used in combination of 2 or more type.

  The content of the abietic acid ester tackifying liquid (B) in the adhesive composition P is preferably 5 to 25 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). Particularly, it is preferably 7 to 20 parts by mass, and more preferably 10 to 15 parts by mass. When the content of the abietic acid ester-based tackifying liquid (B) is 5 parts by mass or more, the above-described adhesion improving effect is exhibited, and the resulting adhesive has excellent blister resistance. Moreover, when the content of the abietic acid ester-based tackifying liquid (B) is 25 parts by mass or less, the cohesive force of the obtained adhesive becomes preferable, and the obtained adhesive has durability. .

(3) Crosslinking agent (C)
The adhesive composition P preferably further contains a crosslinking agent (C). When the adhesive composition P is heated, the crosslinking agent (C) reacts with the reactive functional group of the (meth) acrylic acid ester polymer (A). Thereby, the (meth) acrylic acid ester polymer (A) is cross-linked by the cross-linking agent (C), and the resulting pressure-sensitive adhesive has improved cohesive force and is more excellent in blister resistance.

  The crosslinking agent (C) may be any one that reacts with the reactive functional group of the (meth) acrylic acid ester polymer (A). For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, and an amine crosslinking agent. , Melamine crosslinking agent, aziridine crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, ammonium salt crosslinking agent, etc. Is mentioned. Among these, when the reactive functional group of the (meth) acrylic acid ester polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent that is excellent in reactivity with the hydroxyl group, and (meth) acrylic acid When the reactive functional group which the ester polymer (A) has is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group. In addition, a crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferable from the viewpoint of reactivity with hydroxyl groups.

  Examples of the epoxy crosslinking agent include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl. Examples include ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like.

  It is preferable that content of the crosslinking agent (C) in the adhesive composition P is 0.001-10 mass parts with respect to 100 mass parts of (meth) acrylic acid ester polymer (A), especially 0. It is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 1 part by mass.

  When content of a crosslinking agent (C) exists in said range, blister resistance can be improved, without inhibiting the level | step difference followability of the adhesive obtained.

(4) Various additives For the adhesive composition P, if desired, various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, refractive index adjusters, antistatic agents, tackifiers, Antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillers, and the like can be added.

(5) Manufacture of adhesive composition Adhesive composition P manufactured (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) was abietic acid ester. It can be produced by adding a system tackifying liquid (B) and, if desired, a crosslinking agent (C) and additives.

  The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) can be performed by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like. Two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  When the (meth) acrylic acid ester polymer (A) is obtained, the solution of the (meth) acrylic acid ester polymer (A) is added to the abietic acid ester-based tackifying liquid (B) and optionally a crosslinking agent (C). The adhesive composition P (coating solution) diluted with the solvent is obtained by adding the additive and the diluting solvent and mixing them well.

  Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may be 10-60 mass%. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as a dilution solvent.

(6) Production of pressure-sensitive adhesive The pressure-sensitive adhesive according to this embodiment is obtained by crosslinking the pressure-sensitive adhesive composition P. The crosslinking of the pressure-sensitive adhesive composition P can be usually performed by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing the dilution solvent of the adhesive composition P, etc.

  When performing heat processing, it is preferable that heating temperature is 50-150 degreeC, and it is especially preferable that it is 70-120 degreeC. The heating time is preferably 30 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH). When this curing period is necessary, after the curing period has elapsed, and when the curing period is unnecessary, an adhesive is formed after the heat treatment.

  By the heat treatment (and curing), the (meth) acrylic acid ester polymer (A) is sufficiently cross-linked and can exhibit excellent blister resistance.

(7) Gel fraction The gel fraction of the adhesive which concerns on this embodiment is 30 to 95%, Preferably it is 40 to 80%, Most preferably, it is 45 to 70%. When the gel fraction is less than 30%, the cohesive force of the pressure-sensitive adhesive is insufficient and blister resistance is lowered. On the other hand, if the gel fraction exceeds 95%, the adhesive strength becomes too low and the durability is lowered or the step following performance is lowered. In addition, the measuring method of a gel fraction is as showing to the test example mentioned later.

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to this embodiment includes two release sheets 12a and 12b and the two release sheets 12a so as to be in contact with the release surfaces of the two release sheets 12a and 12b. , 12b and an adhesive layer 11 sandwiched between the two layers. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

(1) Adhesive layer The adhesive layer 11 is comprised from the adhesive mentioned above, ie, it is comprised from the adhesive formed by bridge | crosslinking the adhesive composition P. As shown in FIG.

  The thickness of the pressure-sensitive adhesive layer 11 (measured according to JIS K7130) is preferably 10 to 400 μm, particularly preferably 20 to 300 μm, and more preferably 50, depending on the height of the step. It is preferable that it is -250 micrometers. When the thickness of the pressure-sensitive adhesive layer 11 is 10 μm or more, good step followability is exhibited, and when the thickness of the pressure-sensitive adhesive layer 11 is 400 μm or less, workability is improved. The pressure-sensitive adhesive layer 11 may be formed as a single layer or may be formed by laminating a plurality of layers.

(2) Release sheet The release sheets 12a and 12b are not particularly limited, and known plastic films can be used. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene acetate A vinyl film, an ionomer resin film, an ethylene / (meth) acrylic acid copolymer film, an ethylene / (meth) acrylic acid ester copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluororesin film, or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  It is preferable that the peeling surface (especially the surface in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b is subjected to a peeling treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Of the release sheets 12a and 12b, one release sheet is preferably a heavy release release sheet having a high release force, and the other release sheet is preferably a light release release sheet having a low release force.

  Although there is no restriction | limiting in particular about the thickness of release sheet 12a, 12b, Usually, it is about 20-150 micrometers.

(3) Production of pressure-sensitive adhesive sheet As one production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and heat treatment is performed for adhesion. After cross-linking the composition P and forming a coating layer, the release surface of the other release sheet 12b (or 12a) is overlaid on the coating layer. When a curing period is required, a curing period is set, and when the curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

  As another production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12 a, a heat treatment is performed to cross-link the pressure-sensitive adhesive composition P, and a coating layer To obtain a release sheet 12a with a coating layer. Moreover, the coating liquid of the said adhesive composition P is apply | coated to the peeling surface of the other peeling sheet 12b, heat processing is performed, the adhesive composition P is bridge | crosslinked, an application layer is formed, and an application layer is attached. A release sheet 12b is obtained. And the peeling sheet 12a with an application layer and the peeling sheet 12b with an application layer are bonded together so that both application layers may mutually contact. When the curing period is necessary, the curing period is set, and when the curing period is unnecessary, the above-mentioned laminated application layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, it can be stably produced.

  For example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used as a method for applying the coating solution of the adhesive composition P.

(4) Haze value The pressure-sensitive adhesive layer 11 in the present embodiment preferably has a haze value (measured according to JIS K7136: 2000) of 3% or less, particularly preferably 2% or less. Further, it is preferably 1% or less. When the haze value is 3% or less, the transparency is very high, which is suitable for optical applications.

(5) Total light transmittance The pressure-sensitive adhesive layer 11 in the present embodiment preferably has a total light transmittance (value measured according to JIS K7105: 1981) of 90% or more, particularly 95% or more. It is preferable that it is 98% or more. When the total light transmittance is 98% or more, the transparency is very high and it is suitable for optical use.

(6) Use of pressure-sensitive adhesive sheet By using the pressure-sensitive adhesive sheet 1, for example, the capacitive touch panel 2 shown in FIG. 2 can be manufactured. The touch panel 2 includes a display module 3, a first film sensor 5 a laminated thereon via an adhesive layer 4 a, and a second film sensor 5 b laminated thereon via an adhesive layer 4 b. And the cover material 6 laminated | stacked through the adhesive layer 11 on it is comprised.

  The pressure-sensitive adhesive layer 11 in the touch panel 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1.

  Examples of the display module 3 include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper.

  The pressure-sensitive adhesive layers 4a and 4b may be formed by the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, or may be formed by other pressure-sensitive adhesives or pressure-sensitive adhesive sheets. In the latter case, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 4 includes an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyvinyl ether-based pressure-sensitive adhesive. However, among them, an acrylic pressure-sensitive adhesive is preferable.

  The 1st film sensor 5a and the 2nd film sensor 5b are normally comprised from the base film 51 and the patterned transparent conductive film 52, respectively. Although it does not specifically limit as the base film 51, For example, a polyethylene terephthalate film, an acrylic film, a polycarbonate film etc. are used.

  Examples of the transparent conductive film 52 include metals such as platinum, gold, silver and copper, oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide and zinc dioxide, tin-doped indium oxide (ITO), and zinc oxide-doped oxide. Examples include composite oxides such as indium, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide, and non-oxidized compounds such as chalcogenide, lanthanum hexaboride, titanium nitride, and titanium carbide. Among these, those made of tin-doped indium oxide (ITO) are preferable.

  One of the transparent conductive film 52 of the first film sensor 5a and the transparent conductive film 52 of the second film sensor 5b normally constitutes a circuit pattern in the X-axis direction, and the other constitutes a circuit pattern in the Y-axis direction. .

  The transparent conductive film 52 of the second film sensor 5b in the present embodiment is located above the second film sensor 5b in FIG. 2, but is not limited to this, and the second film sensor It may be located below 5a. Moreover, although the transparent conductive film 52 of the 1st film sensor 5a is located in the upper side of the 1st film sensor 5a in FIG. 2, it is not limited to this, The 1st film sensor 5a It may be located on the lower side.

  The cover material 6 is mainly composed of a glass plate or a plastic plate. The glass plate is not particularly limited. For example, chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass. Etc. The plastic plate is not particularly limited, and examples thereof include an acrylic plate made of polymethyl methacrylate and the like, and a polycarbonate plate.

  In addition, a functional layer such as a hard coat layer, an antireflection layer, or an antiglare layer may be provided on one side or both sides of the glass plate or plastic plate, or a hard coat film, an antireflection film, or an antiglare film. Such optical members may be laminated.

  In the present embodiment, the cover material 6 has a step on the surface on the pressure-sensitive adhesive layer 11 side, and specifically has a step due to the presence or absence of the printing layer 7. The print layer 7 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the cover material 6.

  The material which comprises the printing layer 7 is not specifically limited, The well-known material for printing is used. The thickness of the printing layer 7, that is, the height of the step, is preferably 3 to 45 μm, more preferably 5 to 35 μm, particularly preferably 7 to 25 μm, and preferably 7 to 15 μm. Further preferred.

  Further, the thickness of the printing layer 7 (height of the step) is preferably 3 to 30% of the thickness of the pressure-sensitive adhesive layer 11, particularly preferably 3.2 to 20%, and more preferably 3 It is preferable that it is 5 to 15%. As a result, the pressure-sensitive adhesive layer 11 can easily follow the step formed by the printing layer 7, and the occurrence of floating or bubbles in the vicinity of the step is suppressed.

An example of the manufacturing method of the touch panel 2 will be described below.
One release sheet 12a is peeled from the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 is bonded to the second film sensor 5b so as to be in contact with the patterned transparent conductive film 52 of the second film sensor 5b. To do. On the other hand, the pressure-sensitive adhesive layer 4b provided on the release sheet is bonded to the first film sensor 5a so as to be in contact with the patterned transparent conductive film 52 of the first film sensor 5a.

  Then, the release film remaining on the pressure-sensitive adhesive layer 4b is peeled off, and the exposed pressure-sensitive adhesive layer 4b is opposite to the surface on which the pressure-sensitive adhesive layer 11 is laminated in the second film sensor 5b (second surface). Both are bonded so that it may touch the exposed surface of the base film 51 of the film sensor 5b. Thereby, the laminated body by which the peeling sheet 12b, the adhesive layer 11, the 2nd film sensor 5b, the adhesive layer 4b, and the 1st film sensor 5a are laminated | stacked one by one is obtained.

  Next, the pressure-sensitive adhesive layer 4a provided on the release sheet is bonded to the surface of the laminate on the first film sensor 5a side (exposed surface of the base film 51 of the first film sensor 5a). Subsequently, the other release sheet 12b is peeled from the laminate, and the cover material 6 is pasted so that the printed layer 7 side of the cover material 6 contacts the pressure-sensitive adhesive layer 11 with respect to the exposed pressure-sensitive adhesive layer 11. Match. Thereby, the structure by which the cover material 6, the adhesive layer 11, the 2nd film sensor 5b, the adhesive layer 4b, the 1st film sensor 5a, the adhesive layer 4a, and a peeling sheet are laminated | stacked one by one is obtained.

  Finally, the release sheet is peeled off from the structure, and the structure is bonded to the display module 3 so that the exposed pressure-sensitive adhesive layer 4 a is in contact with the display module 3. Thereby, the touch panel 2 shown in FIG. 2 is manufactured.

  When the pressure-sensitive adhesive layer 11 and the cover material 6 are bonded in the above process, since the pressure-sensitive adhesive layer 11 is excellent in step following ability, it is difficult to form a gap between the step formed by the printing layer 7 and the pressure-sensitive adhesive layer 11. The agent layer 11 can fill the step. Further, even when the touch panel 2 is placed under a high temperature and high humidity condition, it is possible to prevent bubbles, floats, peeling, and the like from occurring near the step.

  Further, when the cover material 6 is a plastic plate, even if outgas is generated from the plastic plate under high temperature and high humidity conditions, the pressure-sensitive adhesive layer 11 is excellent in blister resistance, and thus blisters such as bubbles, floats, and peeling. Is suppressed from occurring.

  Furthermore, since the pressure-sensitive adhesive layer 11 is excellent in moisture and heat whitening resistance, whitening when the touch panel 2 returns to room temperature after being placed in a high temperature and high humidity condition is suppressed.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, one of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
1. Preparation of (meth) acrylic acid ester polymer 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate were copolymerized to produce a (meth) acrylic acid ester polymer ( A) was prepared. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, it was a weight average molecular weight (Mw) of 600,000.

2. Preparation of Adhesive Composition 100 parts by mass of the (meth) acrylic acid ester polymer (A) obtained in the above step (1) (solid content converted value; the same applies hereinafter) and an abietic acid ester-based tackifying liquid (B ) 10 parts by mass of abietic acid ester compound (made by Arakawa Chemical Co., Ltd., product name “Pine Crystal ME-G”) as (tackifier) and tolylene diisocyanate compound (made by Toyochem Co., Ltd.) as a crosslinking agent (C) , Product name “BHS8515”) 0.25 parts by mass, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 36% by mass.

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[(Meth) acrylic acid ester polymer (A)]
2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate AA: acrylic acid MA: methyl acrylate
[Crosslinking agent (C)]
Isocyanate: Tolylene diisocyanate compound (Toyochem, product name “BHS8515”)
Epoxy system: 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Taisei Kayaku Co., Ltd., product name “TC-5”)

3. Production of pressure-sensitive adhesive sheet Peeling of a heavy-peelable release sheet (product name "SP-PET752150", manufactured by Lintec Corporation), in which one side of a polyethylene terephthalate film was subjected to a release treatment with a silicone-based release agent The treated surface was coated with a knife coater so that the thickness after drying was 25 μm, and then heat treated at 90 ° C. for 1 minute to form a coated layer. Similarly, a release treatment of a light release release sheet (product name “SP-PET382120” manufactured by Lintec Corporation) in which one side of a polyethylene terephthalate film was release-treated with a silicone-based release agent was applied to the obtained adhesive composition coating solution. The surface was coated with a knife coater so that the thickness after drying was 25 μm, and then heat-treated at 90 ° C. for 1 minute to form a coating layer.

  Subsequently, the heavy release type release sheet with the coating layer obtained above and the light release type release sheet with the coating layer obtained above were bonded so that both coating layers were in contact with each other. By curing for 7 days under the condition of 50% RH, a pressure-sensitive adhesive sheet having a structure of heavy release type release sheet / pressure-sensitive adhesive layer (thickness: 50 μm) / light release type release sheet was produced. The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring instrument (manufactured by Teclock, product name “PG-02”) in accordance with JIS K7130.

[Examples 2-3, Comparative Examples 1-4]
The ratio of each monomer constituting the (meth) acrylic acid ester polymer (A), the weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A), the type and blending amount of the tackifier, and the crosslinking agent A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the type and blending amount of (C) were changed as shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Measurement of gel fraction)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), the mass was weighed with a precision balance, and the mesh By subtracting the single mass, the mass of the adhesive alone was calculated. The mass at this time is M1.

  Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Thereafter, the pressure-sensitive adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 80 ° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the pressure sensitive adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Blister resistance evaluation)
Polyethylene terephthalate film (manufactured by Oike Kogyo Co., Ltd., ITO film, thickness) provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples 125 μm) transparent conductive film and an acrylic plate made of polymethyl methacrylate (PMMA) (Mitsubishi Gas Chemical Co., Ltd., Iupilon sheet MR200, thickness: 1 mm) to obtain a laminate.

The obtained laminate was autoclaved for 30 minutes at 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 24 hours. Subsequently, it was stored for 72 hours under 85 ° C. and 85% RH durability conditions. Thereafter, it was visually confirmed whether or not the pressure-sensitive adhesive layer had bubbles, floating or peeling, and blister resistance was evaluated according to the following criteria. The results are shown in Table 2.
A: There were no bubbles, no floating, and no peeling.
○: Only bubbles with a diameter of 0.1 mm or less were generated.
X: Bubbles with a diameter of more than 0.1 mm, floating or peeling occurred.

[Test Example 3] (Evaluation of step following ability)
(A) Preparation of sample for evaluation On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), an ultraviolet curable ink (made by Teikoku Ink, The product name “POS-911 Black”) was screen-printed in a frame shape (outside: vertical 90 mm × width 50 mm, width 5 mm) so that the coating thickness was any one of 5 μm, 10 μm, 15 μm, and 20 μm. Next, irradiation with ultraviolet rays (80 W / cm ² , ^two metal halide lamps, lamp height of 15 cm, belt speed of 10 to 15 m / min) is performed to cure the printed ultraviolet curable ink, and a level difference due to printing (level difference) A stepped glass plate having a thickness of any one of 5 μm, 10 μm, 15 μm, and 20 μm was produced.

  The light release type release sheet was peeled off from the pressure sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure sensitive adhesive layer was easily made of a polyethylene terephthalate film having an easy adhesion layer (Toyobo Co., Ltd., PET A4300, thickness: 100 μm). Bonded to the adhesive layer. Next, the heavy release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (product name “LPD3214”, manufactured by Fuji Plastics Co., Ltd.), the laminate is laminated on each stepped glass plate so that the adhesive layer covers the entire frame-like print, and this is used as an evaluation sample. did.

(B) Evaluation of Evaluation Sample The obtained evaluation sample was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 24 hours. Subsequently, it stored for 72 hours under the wet heat conditions of 85 degreeC and 85% RH, and level | step difference followability was evaluated after that. Step followability is determined by whether or not the printing step is completely filled with the adhesive layer, and if gaps or bubbles are observed at the interface between the printing step and the adhesive layer, it cannot follow the printing step. It is judged that Here, the step following property was evaluated as a step following rate (%) according to the following criteria. The results are shown in Table 2.

Step follow-up rate (%) = {(height of printing step filled without gaps or bubbles (μm)) / (thickness of adhesive layer: 50 μm)} × 100
A: Step following rate 40%
○: Step following rate 10% to 30%
×: Step following rate less than 10%

[Test Example 4] (Measurement of optical properties)
About the adhesive layer of the adhesive sheet obtained by the Example and the comparative example, according to JISK7361-1: 1997, using a haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH-2000) haze value (%) and Total light transmittance (%) was measured. The results are shown in Table 2.

  As can be seen from Table 2, the pressure-sensitive adhesive sheets obtained in the examples were excellent in both step followability and blister resistance, and had good optical properties.

  The pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, for bonding between a display module in a touch panel and a cover material having a step, particularly a plastic plate.

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Touch panel 3 ... Display body module 4a, 4b ... Adhesive layer 5a ... 1st film sensor 5b ... 2nd film sensor 51 ... Base film 52 ... Transparent conductive film 6 ... Cover material 7 ... Print layer

Claims (7)

(Meth) acrylate polymer (A) containing 8-30% by mass of a monomer having a reactive functional group as a monomer unit constituting the polymer;
An adhesive obtained by crosslinking an adhesive composition containing an abietic acid ester-based tackifying liquid (B),
A pressure-sensitive adhesive having a gel fraction of 30 to 95%.   The said (meth) acrylic acid ester polymer (A) contains the hard monomer whose glass transition temperature as a homopolymer is 70 degreeC or more as a monomer unit which comprises the said polymer. The adhesive as described.   The pressure-sensitive adhesive according to claim 1 or 2, wherein the (meth) acrylic acid ester polymer (A) contains 2-ethylhexyl (meth) acrylate as a monomer unit constituting the polymer. .   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 200,000 to 1,200,000.   The said adhesive composition contains a crosslinking agent (C) further, The adhesive as described in any one of Claims 1-4 characterized by the above-mentioned. Two release sheets,
An adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets;
The said adhesive layer consists of an adhesive as described in any one of Claims 1-5, The adhesive sheet characterized by the above-mentioned.   The pressure-sensitive adhesive layer according to claim 6, wherein the pressure-sensitive adhesive layer is disposed between two patterned transparent conductive films or between the patterned transparent conductive film and a cover material or a display module. Sheet.

Images