JP2016135832A - Adhesive sheet for touch panel, adhesive film for touch panel, laminate for touch panel, electrostatic capacitance touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet for touch panel excellent in wet thermal adhesiveness and step followability, an adhesive film for touch panel and a laminate for touch panel and an electrostatic capacitance which can be obtained by using the adhesive sheet for touch panel.SOLUTION: The adhesive sheet for touch panel is an adhesive sheet for touch panel by curing a composition for forming an adhesive sheet containing a rubber, a polymerizable monomer, a photoinitiator and a tackifier. The rubber contains a first rubber having weight average molecular weight of 1000 to 100,000 and a second rubber having weight average molecular weight of 250,000 to 2,000,000 with the content of the second rubber of 10 mass% or more based on 100 mass% of the total mass of the adhesive sheet for touch panel.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive sheet for a touch panel, an adhesive film for a touch panel, a laminate for a touch panel, and a capacitive touch panel.

In recent years, the rate of mounting touch panels on mobile phones, portable game devices, and the like has increased, and for example, capacitive touch panels capable of detecting multiple points (hereinafter simply referred to as touch panels) are attracting attention.
Usually, when manufacturing a touch panel, a pressure-sensitive adhesive sheet is used to bring the members such as a display device and a touch panel sensor into close contact with each other.
For example, Patent Document 1 discloses that “(A) component: a hydrogenated conjugated diene-based polymer site and a hydrogenated conjugated diene-based polymer including a reactive double bond; and (B) component: 8 or more carbon atoms” Solvent-free active energy ray-curable optical pressure-sensitive adhesive composition comprising a monomer having 18 or less linear or branched alkyl groups and a component (C): a monomer having a hydroxyl group and / or a nitrogen atom-containing group The weight average molecular weight of the component (A) is 10,000 or more and 100,000 or less, the content of the component (A), the content of the component (B), and the (C ) The active energy ray-curable optical pressure-sensitive adhesive composition, wherein the content of the component (C) is 5% by mass or more and 20% by mass or less with respect to the total content of Adhesive sheet obtained using Etc. have been disclosed.

JP, 2014-214275, A

When the above-mentioned pressure-sensitive adhesive sheet is applied to a touch panel, if the touch panel is placed in a humid heat environment, the adhesion between the pressure-sensitive adhesive sheet and the adhesion target member is likely to be reduced.
Thus, when adhesiveness falls, a water | moisture content will enter easily between an adhesive sheet and a contact object member. At this time, if the pressure-sensitive adhesive sheet has high hydrophilicity, it can absorb moisture, and thus hardly causes a problem. On the other hand, when the hydrophobicity of the pressure-sensitive adhesive sheet for touch panels is high, moisture that has returned to room temperature is likely to condense between the pressure-sensitive adhesive sheet and the adhesion target member, which causes whitening of the touch panel.
In recent years, as disclosed in Patent Document 1, in order to obtain a touch panel that is less likely to malfunction, the dielectric constant of the pressure-sensitive adhesive sheet used therein is lowered. In order to make the adhesive sheet have a low dielectric constant, for example, a highly hydrophobic material such as rubber or terpene resin may be added to the adhesive composition (adhesive sheet composition). If it does so, the hydrophobicity of an adhesive sheet will become high, and it exists in the tendency which the problem of the whitening mentioned above tends to arise.
In order to solve such a problem, even when a highly hydrophobic material is used, it is required to improve the adhesiveness (wet heat adhesion) of the pressure-sensitive adhesive sheet during wet heat.

Here, Patent Document 1 described above shows that the pressure-sensitive adhesive sheet obtained by using the pressure-sensitive adhesive composition has a low dielectric constant and excellent transparency under high-temperature and high-humidity conditions. .
However, the pressure-sensitive adhesive sheet described in Patent Document 1 does not satisfy the level required at least recently in terms of wet heat adhesion, and further improvement is required.

  On the other hand, when bonding the adhesive sheet to a transparent panel having a step due to the decorative portion, it is also important to suppress the generation of bubbles in the step portion. That is, it is required to be excellent in so-called step following ability.

This invention is made | formed in view of the above point, and it aims at providing the adhesive sheet for touchscreens excellent in wet heat adhesiveness and level | step difference followable | trackability.
Moreover, this invention also makes it the objective to provide the adhesive film for touch panels obtained using the said adhesive sheet for touch panels, the laminated body for touch panels, and a capacitive touch panel.

That is, as a result of intensive studies on the above problems, the present inventor has found that a desired effect can be obtained by adding a specific amount of high molecular weight rubber (weight average molecular weight: 250,000 to 2,000,000).
More specifically, the present inventors have found that the above object can be achieved by the following configuration.

(1) A pressure-sensitive adhesive sheet for a touch panel obtained by curing a pressure-sensitive adhesive sheet-forming composition containing a rubber, a polymerizable monomer, a photopolymerization initiator, and a tackifier,
The rubber includes a first rubber having a weight average molecular weight of 1,000 to 100,000 and a second rubber having a weight average molecular weight of 250,000 to 2,000,000.
The pressure-sensitive adhesive sheet for touch panel, wherein the content of the second rubber is 10% by mass or more with respect to 100% by mass of the total mass of the pressure-sensitive adhesive sheet for touch panel.
(2) The pressure-sensitive adhesive sheet for touch panel according to (1), wherein the second rubber contains at least one selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene, and modified polyisoprene.
(3) The pressure-sensitive adhesive sheet for touch panel according to (1) or (2), wherein the first rubber contains at least one selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene, and modified polyisoprene.
(4) The difference in SP value between the second rubber and the polymerizable monomer and the difference in SP value between the second rubber and the first rubber are both 0.4 or less, (1 )-(3) The adhesive sheet for touch panels as described in any one of.
(5) In the pressure-sensitive adhesive sheet forming composition, the mass ratio of the second rubber to the total mass of the first rubber, the second rubber, and the polymerizable monomer is 0.25 to 0.35. The pressure-sensitive adhesive sheet for a touch panel according to any one of (1) to (4) above.
(6) Furthermore, the said adhesive sheet formation composition contains phosphorus antioxidant,
In the pressure-sensitive adhesive sheet forming composition, the ratio of the mass of the phosphorus antioxidant to the mass of the second rubber is 0.006 or more, and any one of the above (1) to (5) The adhesive sheet for touchscreens of description.
(7) The gel component in the second rubber according to any one of (1) to (6), wherein the gel component is 5% by mass or less with respect to 100% by mass of the total mass of the second rubber. Touch panel adhesive sheet.
(8) The pressure-sensitive adhesive sheet for a touch panel according to any one of (1) to (7), wherein the second rubber is a rubber obtained by anionic polymerization.
(9) The adhesive for touch panels which has the adhesive sheet for touch panels as described in any one of said (1)-(8), and the peeling sheet arrange | positioned on the at least one surface of the said adhesive sheet for touch panels. the film.
(10) A laminate for a touch panel, comprising the touch panel pressure-sensitive adhesive sheet according to any one of (1) to (8) above and a capacitive touch panel sensor.
(11) Furthermore, a protective substrate is provided,
The laminated body for touchscreens as described in said (10) provided with the said protective substrate, the said adhesive sheet for touchscreens, and the said capacitive touch panel sensor in this order.
(12) A capacitive touch panel comprising a capacitive touch panel sensor, the touch panel adhesive sheet according to any one of (1) to (8), and a display device in this order.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet for touchscreens excellent in wet heat adhesiveness and level | step difference followable | trackability can be provided.
Moreover, according to this invention, the adhesive film for touchscreens obtained using the said adhesive sheet for touchscreens, the laminated body for touchscreens, and a capacitive touch panel can also be provided.

It is sectional drawing of the one aspect | mode of the laminated body for touchscreens of this invention. It is sectional drawing of another aspect of the laminated body for touchscreens of this invention. It is sectional drawing of the electrostatic capacitance type touch panel of this invention. It is sectional drawing of the evaluation sample used by level | step difference followable | trackability evaluation.

Below, the adhesive sheet for touch panels, the adhesive film for touch panels, the laminated body for touch panels, and a capacitive touch panel of this invention are demonstrated in detail.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Adhesive sheet for touch panel]
The pressure-sensitive adhesive sheet for a touch panel of the present invention is a pressure-sensitive adhesive sheet for a touch panel obtained by curing a composition for forming a pressure-sensitive adhesive sheet containing a rubber, a polymerizable monomer, a photopolymerization initiator, and a tackifier. The rubber includes a first rubber having a weight average molecular weight of 1,000 to 100,000 and a second rubber having a weight average molecular weight of 250,000 to 2,000,000. Content of the said 2nd rubber is 10 mass% or more with respect to 100 mass% of total mass of the said adhesive sheet for touchscreens.
Below, the adhesive sheet for touchscreens of this invention may only be called "adhesive sheet".
In this invention, the adhesive sheet for touch panels excellent in wet heat adhesiveness and level | step difference followability is obtained by making the adhesive sheet for touch panels contain the 2nd rubber | gum whose weight average molecular weight is 250,000-2 million in a specific amount. I found.
Although the details of this mechanism are not clear, it is presumed that it is as follows.
That is, if the entanglement between the molecular chains constituting the rubber is small, the shear rate dependence becomes close to the behavior of a Newtonian viscous body. On the other hand, if the molecular chains are sufficiently entangled with each other, “shear thinning” occurs in which the stress decreases due to shearing, so the speed dependence becomes small (becomes the behavior of a non-Newtonian viscous body). . Moreover, there is a correlation between the speed dependency and the temperature dependency. When the speed dependency is small, the temperature dependency becomes small.
Here, since the second rubber has a high molecular weight of 250,000 to 2,000,000, the molecular weight is likely to be entangled with each other, and the speed dependency is small. Therefore, by including the second rubber in the pressure-sensitive adhesive sheet-forming composition, it is considered that the difference in peel strength between the low temperature and the high temperature of the pressure-sensitive adhesive sheet for touch panels is reduced, and wet heat adhesion is improved.
Moreover, it is thought that the adhesive sheet for touch panels excellent in level | step difference followability is obtained by using 2nd rubber | gum.

<Adhesive sheet forming composition>
The pressure-sensitive adhesive sheet of the present invention is obtained by curing a pressure-sensitive adhesive sheet-forming composition. Below, the component contained in the composition for adhesive sheet formation of this invention and the component which may be contained are demonstrated.

(Rubber)
The composition for forming an adhesive sheet of the present invention contains rubber. The rubber contained in the composition for forming an adhesive sheet of the present invention includes a first rubber having a weight average molecular weight of 1,000 to 100,000 and a second rubber having a weight average molecular weight of 250,000 to 2,000,000.
When the pressure-sensitive adhesive sheet forming composition (pressure-sensitive adhesive sheet) contains rubber, the hydrophobicity of the pressure-sensitive adhesive sheet can be improved and the relative dielectric constant of the touch panel can be reduced.
The rubber contained in the pressure-sensitive adhesive sheet-forming composition of the present invention contains other rubbers (that is, those having a polymerization average molecular weight of the first rubber and the second rubber) as long as they contain the first rubber and the second rubber. Rubber that is outside the range of rubber) may be contained.

(First rubber)
The first rubber has a weight average molecular weight in the range of 1,000 to 100,000, and is usually liquid at normal temperature (23 ° C.).
The weight average molecular weight of the first rubber is in the range of 1000 to 100,000, but is preferably in the range of 1000 to 50,000, and more preferably in the range of 1000 to 35,000. When the weight average molecular weight of the first rubber is in the above range, a pressure-sensitive adhesive sheet excellent in step following ability can be obtained, or the handleability of the pressure-sensitive adhesive sheet-forming composition can be improved.
On the other hand, when the weight average molecular weight of the first rubber is less than 1000, plasticization becomes excessive, and there is a tendency for the adhesive strength to decrease or, if remarkable, the adhesive layer to flow and leak at a high temperature. On the other hand, if the weight average molecular weight of the first rubber exceeds 100,000, the step following property of the pressure-sensitive adhesive sheet is lowered, the viscosity of the pressure-sensitive adhesive sheet forming composition is excessively improved, and the handleability is lowered.

In addition, the weight average molecular weight of each component in this invention is the value calculated | required by the gel permeation chromatography (GPC) measurement by polystyrene conversion.
More specifically, the weight average molecular weight is measured using GPC (gel permeation chromatography) under the following conditions.
Apparatus: HLC-8020 manufactured by Tosoh Corporation
Column: TSKgel GMHXL manufactured by Tosoh Corporation
Column temperature: 40 ° C
Detector: differential refractometer RI-8020 manufactured by Tosoh Corporation
Eluent: Tetrahydrofuran

Examples of the first rubber include unmodified or modified rubber, and more specifically, natural rubber, (modified) polyisobutylene, (modified) polybutadiene, (modified) hydrogenated polyisoprene, and (modified) hydrogenated. Examples thereof include polybutadiene, (modified) polyisoprene, (modified) polybutene, (modified) styrene butadiene copolymer, a copolymer arbitrarily selected from these groups, and a mixture thereof. In the above examples, “(modified) A” (“A” is a compound name) is a generic name including both A modified with an arbitrary group and unmodified A.
The first rubber may contain a rubber having a polymerizable group. Rubber having a polymerizable group is a kind of modified rubber. Examples of such polymerizable groups include known radical polymerizable groups ((meth) acryloyl group, acrylamide group, vinyl group, styryl group, allyl group, etc.) and known cationic polymerizable groups (epoxy group, etc.). It is done. Examples of the first rubber having a polymerizable group include rubbers having a (meth) acryloyl group (for example, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene). In addition, the 1st rubber | gum which has a polymeric group is not contained in the polymeric monomer mentioned later.
The first rubber is selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene and modified polyisoprene (preferably (meth) acryl-modified polyisoprene) from the viewpoint of realizing low dielectric constant and low temperature dependency. It is preferable to include at least one kind.
In this specification, (meth) acryl is a generic name including both acryl and methacryl, and (meth) acryloyl is a generic name including both acryloyl and methacryloyl.

The content of the first rubber is preferably 5 to 45% by mass and 10 to 30% by mass with respect to the total mass (100% by mass) of the pressure-sensitive adhesive sheet-forming composition in that the effect of the present invention is more excellent. More preferred.
The content of the first rubber is preferably 5 to 45% by mass and more preferably 10 to 30% by mass with respect to the total mass (100% by mass) of the pressure-sensitive adhesive sheet in that the effect of the present invention is more excellent.
In addition, 1 type of 1st rubber | gum may be used and may be used in combination of 2 or more type.

(Second rubber)
The second rubber has a weight average molecular weight in the range of 250,000 to 2,000,000 and is usually solid at normal temperature (23 ° C.).
The weight average molecular weight of the second rubber is in the range of 250,000 to 2,000,000, preferably in the range of 500,000 to 1,800,000, and more preferably in the range of 700,000 to 1,500,000. When the weight average molecular weight of the second rubber is in the above range, an adhesive sheet excellent in wet heat adhesion can be obtained.
On the other hand, when the weight average molecular weight of the second rubber is less than 250,000, the wet heat adhesion of the pressure-sensitive adhesive sheet is lowered. Moreover, when the weight average molecular weight of 2nd rubber exceeds 2 million, preparation of the composition for adhesive sheet formation will become difficult.
The method for measuring the weight average molecular weight is as described above.

Since the specific example of the second rubber is the same as that of the first rubber, the description thereof is omitted.
The second rubber is selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene and modified polyisoprene (preferably (meth) acryl-modified polyisoprene) from the viewpoint of realizing low dielectric constant and low temperature dependency. It is preferable to include at least one kind.

Content of 2nd rubber is 10 mass% or more with respect to the total mass (100 mass%) of the composition for adhesive sheet formation, It is preferable that it is 10-25 mass%, and is 12-20 mass%. More preferably, it is more preferably 15 to 20% by mass.
Content of 2nd rubber is 10 mass% or more with respect to the total mass (100 mass%) of an adhesive sheet, It is preferable that it is 10-25 mass%, and it is more preferable that it is 10-22 mass%. The content is preferably 10 to 18% by mass.
Thus, the adhesive sheet excellent in wet heat adhesiveness is obtained because content of the 2nd rubber is 10 mass% or more. In addition, when the content of the second rubber is 25% by mass or less, the pressure-sensitive adhesive sheet has good flexibility, and a pressure-sensitive adhesive sheet excellent in step following ability can be obtained. There is a tendency for the solubility of to be improved.
On the other hand, when the content of the second rubber is less than 10% by mass, the wet heat adhesion of the pressure-sensitive adhesive sheet is lowered.

The ratio of the mass of the second rubber to the total mass of the first rubber, the second rubber and the polymerizable monomer described later (the mass of the second rubber / the above total) is preferably 0.25 to 0.35, It is more preferably 0.28 to 0.35, and further preferably 0.30 to 0.33.
When the ratio of the mass of the second rubber is 0.25 or more, the wet heat adhesion of the pressure-sensitive adhesive sheet tends to be more excellent. Further, when the ratio of the mass of the second rubber is 0.35 or less, the step following property of the pressure-sensitive adhesive sheet becomes more excellent, or the solubility of the second rubber during the preparation of the pressure-sensitive adhesive sheet-forming composition. Tend to be good.

The difference in SP value between the second rubber and the first rubber and the difference in SP value between the second rubber and the polymerizable monomer described later are preferably 0.4 (MPa) ^1/2 or less, It is more preferably 0.3 (MPa) ^1/2 or less, and further preferably 0.2 (MPa) ^1/2 or less.
Since the difference in SP value is 0.4 or less, the compatibility between the second rubber, the first rubber and the polymerizable monomer is improved, and whitening of the pressure-sensitive adhesive sheet can be suppressed. Can be obtained.
In addition, when each of the first rubber, the second rubber, and the polymerizable monomer contains two or more kinds of compounds, those having the largest SP value difference are compared. For example, the first rubber contains two kinds of compounds (first rubber A, first rubber B), the SP value relationship is first rubber A <first rubber B, and the second rubber contains two kinds of compounds ( 2nd rubber A and 2nd rubber B) are included, and when the relationship of SP value is 2nd rubber A <2nd rubber B, the difference of SP value of 1st rubber A and 2nd rubber B is compared. It shall be.
In the present invention, the SP value (solubility parameter) is determined by Michael M. et al. Collman, John F. Graf, Paul C.M. "Specific Interactions and the Miscibility of Polymer Blends" (1991), Technological Publishing Co., by Painter (Pensylvania State Univ.). Inc. It is a value obtained by the calculation described in.

The second rubber may contain a gel component, and this gel component may exist in the form of gel-like fine particles in the second rubber. If the content of the gel component (gel-like particles) in the second rubber can be reduced, light scattering by the gel component can be suppressed, so that a pressure-sensitive adhesive sheet suitable for optical applications can be obtained. The gel component is a component that is hardly melted due to chemical cross-linking and is insoluble in a good polymer solvent.
From this point of view, the gel component in the second rubber is preferably 5% by mass or less, more preferably 2% by mass or less, based on 100% by mass of the total mass of the second rubber. Most preferably, it is not contained (0% by mass).
The content of the gel component can be measured, for example, by the method described in JP2013-185058A (measurement method of gel fraction).

  The production of the second rubber can be carried out by a conventionally known polymerization method, and the radical species, the cationic polymerization, the anionic polymerization, the coordination polymerization, etc. can be appropriately selected as the active species when the second rubber is polymerized. it can. Among these, since the content of the gel component in the second rubber can be reduced, the second rubber is preferably a rubber obtained by anionic polymerization.

(Polymerizable monomer)
A polymerizable monomer is a compound having a polymerizable group. As the polymerizable group, a known polymerizable group can be used, so-called radical polymerizable group ((meth) acryloyl group, acrylamide group, vinyl group, styryl group, allyl group, etc.), cationic polymerizable group (epoxy group, etc.) ).
Of these, (meth) acrylic monomers are preferred as the polymerizable monomers, in particular because they are excellent in handleability and polymerizability, and can further improve the step following property of the resulting pressure-sensitive adhesive sheet, and are particularly monofunctional (meth) acrylic. Monomers are more preferred. In addition, (meth) acrylic polymer (poly (meth) acrylate) is obtained by superposing | polymerizing a (meth) acryl monomer.
A (meth) acryl monomer is a polymerizable compound having a (meth) acryloyl group. The monofunctional (meth) acrylic monomer is a polymerizable compound having one (meth) acryloyl group.
In addition, as a polymerizable monomer, only 1 type may be used or 2 or more types may be used together.

Although the kind of (meth) acrylic monomer is not particularly limited, (meth) acrylic acid alkyl ester is preferable, and a monofunctional (meth) acrylic monomer represented by the following formula (A) is more preferable in terms of excellent handleability. .
Formula _{(A) CH 2 = CHR 1} -COO-R 2
In formula (A), R ₁ represents a hydrogen atom or an alkyl group. As an alkyl group, C1-C3 is preferable and C1-C1 is more preferable.
R ₂ represents a hydrocarbon group which may have a hetero atom.
Especially, the number of carbon atoms in the hydrocarbon group represented by R ₂ (the number of carbon atoms) is preferably 6 or more, more preferably 6 to 16 in that the step following property of the obtained pressure-sensitive adhesive sheet is more excellent. 8 to 12 are more preferable.
Preferred examples of the hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group obtained by combining these. The aliphatic hydrocarbon group may be linear, branched, or cyclic, and more specifically, a linear aliphatic hydrocarbon group, a branched aliphatic hydrocarbon group, a cyclic aliphatic. Examples include hydrocarbon groups (alicyclic hydrocarbon groups).
Examples of the aliphatic hydrocarbon group include an alkyl group, a cycloalkyl group, and an alkenyl group. Examples of the aromatic hydrocarbon group include a phenyl group and a naphthyl group.

The solubility parameter (SP value) of the (meth) acrylic monomer is not particularly limited, but is preferably 8.0 to 10.0 (MPa) ^1/2 in terms of more excellent effects of the present invention.

  Specific examples of (meth) acrylic monomers include n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, and isodecyl. (Meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-hexadecyl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (Meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate and the like can be mentioned.

One preferred embodiment of the (meth) acrylic monomer is an embodiment in which two types of (meth) acrylic monomers are used in combination in terms of more excellent effects of the present invention. A monomer X in which R ₂ is a chain aliphatic hydrocarbon group (preferably a branched chain aliphatic hydrocarbon group), and a monomer Y in which R ₂ in the formula (A) is a cyclic aliphatic hydrocarbon group; An embodiment in which is used in combination is more preferred.

  Although content in particular of a polymerizable monomer is not restrict | limited, 10-45 mass% is preferable with respect to the total mass of the composition for adhesive sheet formation, 15-30 mass% is more preferable, 20-30 mass% is further more preferable. .

(Photopolymerization initiator)
The composition for forming an adhesive sheet of the present invention contains a photopolymerization initiator.
The kind in particular of photoinitiator is not restrict | limited, A well-known photoinitiator (a radical photoinitiator, a cationic photoinitiator) can be used. For example, alkynephenone photopolymerization initiator, methoxyketone photopolymerization initiator, acylphosphine oxide photopolymerization initiator, hydroxyketone photopolymerization initiator (for example, IRGACURE184; 1,2-α-hydroxyalkylphenone) Aminoketone photopolymerization initiator (for example, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one (IRGACURE (registered trademark) 907)), oxime photopolymerization initiator Is mentioned.
Especially, as a photoinitiator, an acyl phosphine oxide type photoinitiator is preferable, and it is more preferable that at least one selected from the group which consists of a monoacyl phosphine oxide and a bisacyl phosphine oxide is included.
Specific examples of monoacylphosphine oxide include benzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyl-diphenylphosphine oxide, 3,4-dimethyl Examples include benzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl-phenylethoxyphosphine oxide.
Specific examples of bisacylphosphine oxide include bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, bis ( 2,6-dimethylbenzoyl) -ethylphosphine oxide and the like.
In addition, as a photoinitiator, only 1 type may be used or 2 or more types may be used together.

  Although content in particular of a photoinitiator is not restrict | limited, 1.0-5.0 mass% is preferable with respect to 100 mass% of total mass of the composition for adhesive sheet formation, 1.5-4.0 mass% Is more preferable.

(Tackifier)
The composition for forming an adhesive sheet of the present invention contains a tackifier.
As the tackifier, those known in the field of patch or patch preparation may be appropriately selected and used. For example, petroleum resin (for example, aromatic petroleum resin, aliphatic petroleum resin, resin by C9 fraction), terpene resin (for example, α-pinene resin, β-pinene resin, terpene resin, terpene phenol copolymer) , Hydrogenated terpene phenol resin, aromatic modified hydrogenated terpene resin, aromatic modified terpene resin, abietic acid ester resin), rosin resin (eg, partially hydrogenated gum rosin resin, erythritol modified wood rosin resin, tall oil rosin resin) , Wood rosin resin), coumarone indene resin (for example, coumarone indene styrene copolymer), styrene resin (for example, polystyrene, copolymer of styrene and α-methylstyrene, etc.) and the like. More preferred tackifiers include petroleum resins, terpene resins, and styrene resins that do not contain polar groups, with terpene resins being most preferred.
Among the terpene resins, terpene resins and hydrogenated terpene resins are preferable, and hydrogenated terpene resins are most preferable.
Commercially available products can be used as such terpene resins, and specific examples include Clearon P150, Clearon P135, Clearon P125, Clearon P115, Clearon P105, Clearon P85 (manufactured by Yasuhara Chemical) and the like.
In addition, as a tackifier, only 1 type may be used or 2 or more types may be used together.

The content of the tackifier is preferably 5 to 50% by mass, more preferably 20 to 45% by mass with respect to the total mass (100% by mass) of the composition for forming an adhesive sheet, in that the effect of the present invention is more excellent. preferable.
Moreover, 5-50 mass% is preferable with respect to the adhesive sheet total mass (100 mass%), and, as for content of a tackifier, the effect of this invention is more excellent, and 20-45 mass% is more preferable.

(Antioxidant)
The composition for forming an adhesive sheet of the present invention preferably contains an antioxidant. By containing the antioxidant, it is possible to suppress the reaction of the polymerizable group contained in the polymerizable monomer or the like during the preparation of the pressure-sensitive adhesive sheet-forming composition, so that the adhesion of the pressure-sensitive adhesive sheet can be improved. .

Examples of the antioxidant include phenolic antioxidants, hydroquinone antioxidants, phosphorus antioxidants, hydroxylamine antioxidants, and the like.
Examples of the phenol-based or hydroquinone-based antioxidant include 2,6-di-tert-butyl-4-methylphenol, 4,4′-thiobis- (6-tert-butyl-3-methylphenol), 1, 1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythrityl-tetrakis [3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and the like.
Examples of phosphorus antioxidants include tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and bis. Phosphite antioxidants such as (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite Can be mentioned.
Examples of the hydroxylamine-based antioxidant include N, N-dioctadecylhydroxylamine and N, N-dibenzylhydroxylamine.
Among these, it is preferable to use a phosphorus-based antioxidant and more preferable to use a phosphite-based antioxidant because the above-described effects are further exhibited and polymerization inhibition is small.
In addition, as an antioxidant, only 1 type may be used or 2 or more types may be used together.
When the pressure-sensitive adhesive sheet-forming composition contains a phosphorus-based antioxidant, the ratio of the mass of the phosphorus-based antioxidant to the mass of the second rubber in the pressure-sensitive adhesive sheet-forming composition is 0.006 or more. It is preferable that it is 0.01-0.05. Thereby, the above-mentioned effect is further exhibited.

(Other ingredients)
The composition for forming an adhesive sheet of the present invention may contain a chain transfer agent. The type of chain transfer agent is not particularly limited, and known chain transfer agents (for example, 1-dodecanethiol, trimethylolpropane tristhiopropionate, pentaerythritol tetrakisthiopropionate, etc.) are used.

The composition for forming an adhesive sheet of the present invention may contain an adhesion improver. One of the functions of the adhesion improver is to improve the adhesion of the pressure-sensitive adhesive sheet.
Examples of the adhesion improver include (meth) acrylic acid, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, butoxyethylene glycol (meth) acrylate, butoxydiethylene glycol (meth) acrylate, and methoxytriethylene glycol (meth) acrylate. , Tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, tetraethylene glycol monomethyl ether (meth) acrylate, hexaethylene glycol monomethyl Ether (meth) acrylate, octaethylene glycol monomethyl ether (meth) acrylate, nonaethylene glycol methyl ether (Meth) acrylate, heptapropylene glycol monomethyl ether (meth) acrylate, tetraethylene glycol ethyl ether (meth) acrylate, tetraethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, octapropylene glycol mono (meth) acrylate Glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N, N-isopropyl (meth) acrylamide, Nt-octyl (meth) acrylamide, N, N-dimethyl Aminoethyl (meth) acrylamide, N, N- dimethylaminopropyl (meth) acrylamide, diacetone acrylamide, (meth) acryloyl morpholine, N- vinylpyrrolidone, etc. N- vinyl caprolactam. These adhesion improvers may be used alone or in combination of two or more.

  The content in the case of containing an adhesion improver is not particularly limited, but is preferably 0.1 to 10% by mass with respect to 100% by mass of the total mass of the pressure-sensitive adhesive sheet-forming composition, More preferably, it is 0.5-3 mass%.

  The composition for forming an adhesive sheet of the present invention may contain a crosslinking agent. One of the functions of the cross-linking agent is to cross-link the above-described polymerizable monomer and adhesion improver. As the crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, a polyfunctional (meth) acrylate, or the like can be used.

  Examples of the isocyanate-based crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene diisocyanate. , Diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof Examples include adducts with polyol compounds such as trimethylolpropane, burettes and isocyanurates of these polyisocyanate compounds. Among the isocyanate-based crosslinking agents, from the viewpoint of the dielectric constant of the adhesive layer, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, hexa Methylene diisocyanate and isophorone diisocyanate are preferable, and hexamethylene diisocyanate and isophorone diisocyanate are more preferable from the viewpoint of coloring over time.

  Examples of the epoxy-based crosslinking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, Examples include trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, and the like. Among epoxy-based crosslinkers, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and trimethylolpropane triglycidyl ether are preferable from the viewpoint of the flexibility of the adhesive layer. From this point of view, 1,6-hexanediol diglycidyl ether and trimethylolpropane triglycidyl ether are more preferable.

  Examples of polyfunctional (meth) acrylates include ethylene glycol (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, and polypropylene glycol di (meth) acrylate. , Tetraethylene glycol di (meth) acrylate, bisphenoxyethanol full orange acrylate, bisphenoxyethanol full orange acrylate and other bifunctional (meth) acrylates, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tri ( (Meth) acryloyloxyethyl) phosphate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaeryth Toruhekisa (meth) acrylate such as 3 or more functional groups of the (meth) acrylate.

Although it does not specifically limit as content in the case of containing a crosslinking agent, 0.01-2 mass% is preferable with respect to 100 mass% of total mass of the composition for adhesive sheet formation, 0.1-1 mass% Is more preferable.
These crosslinking agents may be used alone or in combination of two or more.

  In addition to the above, the pressure-sensitive adhesive sheet-forming composition of the present invention includes a solvent (water, organic solvent, etc.), a polymerization inhibition inhibitor, a surface lubricant, a leveling agent, a corrosion inhibitor, a light stabilizer, an ultraviolet absorber, and a polymerization agent. Add appropriately according to the use of various conventionally known additives such as inhibitors, silane coupling agents, inorganic or organic fillers, powders such as metal powders and pigments, particles and foils. Can do.

(Method for producing composition for forming pressure-sensitive adhesive sheet)
Although the composition for adhesive sheet formation of this invention is not limited to this, For example, it can obtain by the manufacturing method including the following 1st processes and 2nd processes.
The first step is a step of obtaining a mixture by mixing and stirring the first rubber, the second rubber, the polymerizable monomer, and the tackifier at 80 to 120 ° C. for 1 to 8 hours.
In the 1st process, you may add the adhesion improvement agent etc. which were mentioned as said arbitrary ingredients further.
As described above, the second rubber is often solid at room temperature. Therefore, it is preferable to add the second rubber component by pulverization with an optional device (for example, a rubber chopper) in order to uniformly mix the components in the first step or to increase the compatibility between the components. .
Next, in the second step, after adjusting the first mixture to be in the range of 80 to 120 ° C., the photopolymerization initiator is added to the first mixture, and the mixture is mixed and stirred for 0.5 to 2 hours. And a step of obtaining a composition for forming an adhesive sheet.
In the second step, antioxidants, cross-linking agents and the like mentioned as optional components may be added.
The mixing and stirring in the first step and the second step can be performed by a known apparatus and are not particularly limited. The “mixing and stirring” includes the meaning of “kneading”.

<Method for producing adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention is obtained by curing the above-described pressure-sensitive adhesive sheet-forming composition. Hereinafter, although an example of the manufacturing method of the adhesive sheet of this invention is shown, the manufacturing method of the adhesive sheet of this invention is not limited to this.

  The pressure-sensitive adhesive sheet-forming composition is applied onto a predetermined substrate (for example, a release film), and subjected to a curing treatment to form a pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer). In addition, even if a peeling film is further laminated | stacked on the surface of the adhesive sheet exposed after formation of the adhesive sheet formation composition before the hardening process, or the adhesive sheet formation composition apply | coated on the base material after formation of an adhesive sheet Good.

Examples of the method for applying the composition for forming an adhesive sheet include a gravure coater, a comma coater, a bar coater, a knife coater, a die coater, and a roll coater.
In addition, although the example which apply | coats the composition for adhesive sheet formation was shown here, if it can be made to adhere on a base material, not only application | coating but a well-known method can be utilized.
Moreover, as a hardening process, a photocuring process, a thermosetting process, etc. are mentioned.
The photocuring treatment may consist of a plurality of curing steps, and the light wavelength to be used may be appropriately selected from a plurality. Further, the thermosetting treatment may be composed of a plurality of curing steps, and the method for applying heat may be selected from appropriate methods such as an oven, a reflow furnace, and an IR heater. Furthermore, you may combine a photocuring process and a thermosetting process suitably.
The light source used in the photocuring treatment is not particularly limited, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a xenon lamp, a metal halide lamp, and an electrodeless lamp. The light used for the photocuring treatment is preferably ultraviolet light, and for example, a general ultraviolet irradiation device, more specifically, a belt conveyor type ultraviolet irradiation device is preferably used.
Conditions during the light curing is appropriately selected depending on the components of the compositions used, the amount of irradiation (e.g., ultraviolet irradiation amount) is preferably from 100~2500mJ / cm ² as and 200~1100mJ / cm ² preferable.
In addition, after manufacturing the said adhesive sheet on a temporary support body, the method of transferring an adhesive sheet on a peeling film can also be used.

As described above, one in which a release film (release sheet) is disposed on at least one surface of an adhesive sheet may be handled as an adhesive film. From the viewpoint of handleability, an adhesive film in which release sheets are disposed on both sides of the adhesive sheet is preferable.
As the release sheet, a known release sheet can be used. The thickness of the release sheet to be used is not particularly limited, but is preferably 25 to 250 μm and more preferably 35 to 100 μm from the viewpoint of handleability.

<Physical properties of adhesive sheet>
Although the thickness in particular of an adhesive sheet is not restrict | limited, Usually, it is preferable that it is 20-500 micrometers, and it is more preferable that it is 50-300 micrometers.
The pressure-sensitive adhesive sheet is preferably optically transparent. That is, it is preferably a transparent adhesive sheet. Optically transparent means that the total light transmittance is 85% or more, preferably 90% or more, and more preferably 95% or more. The total light transmittance can be measured using an integrating sphere light transmittance measuring device (for example, trade name “CM-3600A” manufactured by Konica Minolta).

[Laminate for touch panel, capacitive touch panel]
The pressure-sensitive adhesive sheet of the present invention is used for touch panel applications, and in particular, can be suitably used for production of touch panels (particularly, capacitive touch panels). Hereinafter, the aspect which applied the adhesive sheet for the touchscreen use is explained in full detail.

The laminated body for touchscreens of this invention is equipped with the adhesive sheet of this invention mentioned above, and a capacitive touch panel sensor.
One embodiment of the laminate for a touch panel of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing one embodiment of the laminate for a touch panel of the present invention. In FIG. 1, the laminated body 100 for a touch panel includes an adhesive sheet 12 and a capacitive touch panel sensor 18.
Moreover, FIG. 2 is sectional drawing which represents typically another aspect of the laminated body for touchscreens of this invention. In FIG. 2, the laminate for touch panel 200 includes a protective substrate 20, an adhesive sheet 12, and a capacitive touch panel sensor 18.

The capacitive touch panel of the present invention includes a capacitive touch panel sensor, the above-described adhesive sheet of the present invention, and a display device in this order.
One embodiment of the capacitive touch panel of the present invention will be described with reference to the drawings.
FIG. 3A is a cross-sectional view schematically illustrating one embodiment of the capacitive touch panel of the present invention. 3A, the capacitive touch panel 300 includes the capacitive touch panel sensor 18, the adhesive sheet 12, and the display device 40.
FIG. 3B is a cross-sectional view schematically showing another aspect of the capacitive touch panel of the present invention. In FIG. 3B, the capacitive touch panel 400 includes the protective substrate 20, the adhesive sheet 12, the capacitive touch panel sensor 18, the adhesive sheet 12, and the display device 40.

The capacitive touch panel sensor 18 is arranged on the display device (operator side) and uses a change in capacitance that occurs when an external conductor such as a human finger comes into contact (approaching). This is a sensor that detects the position of an external conductor such as a finger.
The configuration of the capacitive touch panel sensor 18 is not particularly limited, but usually has a detection electrode (especially, a detection electrode extending in the X direction and a detection electrode extending in the Y direction), and the static electricity of the detection electrode in contact with or close to the finger. The coordinates of the finger are specified by detecting the change in capacitance.
The protective substrate 20 is a substrate disposed on the adhesive sheet, and serves to protect a capacitive touch panel sensor 18 (to be described later) from the external environment, and its main surface constitutes a touch surface. The protective substrate 20 is preferably a transparent substrate, and a plastic film, a plastic plate, a glass plate, or the like is used. It is desirable that the thickness of the substrate is appropriately selected according to each application.
The display device 40 is a device having a display surface for displaying an image, and each member is arranged on the display screen side. The type of the display device 40 is not particularly limited, and a known display device can be used. For example, cathode ray tube (CRT) display, liquid crystal display (LCD), organic light emitting diode (OLED) display, vacuum fluorescent display (VFD), plasma display panel (PDP), surface field display (SED), field emission display (FED) or electronic paper (E-Paper).

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” and “%” are based on mass.

<Preparation of composition for forming pressure-sensitive adhesive sheet>
First, the first rubber, the second rubber, the polymerizable monomer, the tackifier, and the adhesion improver were kneaded in a kneading machine in a 100 ° C. constant temperature bath so that the mixing ratio shown in Table 1 was obtained.
Subsequently, the temperature of the thermostatic bath was adjusted to 80 ° C., and a photopolymerization initiator, an antioxidant, and a crosslinking agent were added so as to have a blending ratio shown in Table 1, and kneaded in a kneader. And the composition for adhesive sheet formation which concerns on a comparative example was obtained.
The pressure-sensitive adhesive sheet-forming composition according to Comparative Example 2 was obtained without adding the second rubber, and the pressure-sensitive adhesive sheet-forming composition according to Comparative Example 3 was prepared without adding the first rubber. Obtained.

Each component shown in Table 1 is as follows.
(First rubber)
Claprene LIR-30 (trade name, manufactured by Kuraray Co., Ltd., polyisoprene, weight average molecular weight 28,000, SP value 8.0)
-Claprene UC-102M (trade name, manufactured by Kuraray Co., Ltd., methacrylate-modified polyisoprene, weight average molecular weight 17,000, SP value 8.0)
・ Kuraprene LBR-305 (trade name, manufactured by Kuraray Co., Ltd., polybutadiene, weight average molecular weight 26,000, SP value 8.3)
Polybest 110 (trade name, manufactured by Evonik, unmodified liquid polybutadiene, weight average molecular weight 2,600, SP value 8.3)
(Second rubber)
JSR IR-2200 (trade name, manufactured by JSR Corporation, polyisoprene, weight average molecular weight 800,000, SP value 8.0)
・ Cariflex IR0307 (trade name, manufactured by Kraton, polyisoprene, weight average molecular weight 1.4 million, SP value 8.0)
(Polymerizable monomer)
EHA (2-ethylhexyl acrylate, manufactured by Wako Pure Chemical Industries, SP value 7.8)
IBXA (isobornyl acrylate, manufactured by Kyoeisha Chemical Co., SP value 8.4)
-HEA (hydroxyethyl acrylate, Osaka Organic Chemical Industry, SP value 12)
(Photopolymerization initiator)
・ Lucirin TPO (trade name, manufactured by BASF, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide)
Irgacure 819 (trade name, manufactured by BASF, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide)
(Tackifier)
・ Clearon P135 (trade name, manufactured by Yasuhara Chemical, hydrogenated terpene resin)
(Antioxidant)
Irgafos 168 (trade name, manufactured by BASF, phosphorus antioxidant, tris (2,4-di-tert-butylphenyl) phosphite)
(Crosslinking agent)
・ NDA (Kyoeisha Chemical Co., Ltd., 1,9-nonanediol diacrylate)
(Adhesion improver)
Cyclomer M-100 (trade name, manufactured by Daicel Corporation, 3,4-epoxycyclohexylmethyl methacrylate)

<Production of adhesive sheet>
Each pressure-sensitive adhesive sheet-forming composition obtained above was vacuum degassed and then applied to a 50 μm-thick release film with an applicator so that the film thickness was 200 μm, and further covered with a release film, with a metal halide lamp. Ultraviolet irradiation was performed for 3 minutes to obtain pressure-sensitive adhesive films according to Examples and Comparative Examples in which release films were disposed on both sides of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer).
In addition, the peeling PET film (peeling polyethylene terephthalate film) was used for the peeling film.

<Evaluation test>
(Moist heat adhesion)
The adhesive films according to Examples and Comparative Examples obtained as described above were cut into 2.5 cm × 5 cm, respectively, and one of the release films was peeled off to expose the exposed adhesive sheet surface to the glass substrate and the other release The surface of the pressure-sensitive adhesive sheet exposed by peeling off the film was attached to a Kapton film to prepare a sample. Subsequently, the obtained sample was stored in a constant temperature and humidity chamber having a humidity of 85% RH and a temperature of 85 ° C. for 0.5 hour. Thereafter, one end of the Kapton film is held at 85 ° C. using a Tensilon tester (product name “RTC-1150A”) manufactured by Orientec Co., Ltd., and a 180 ° peel test ( (Tensile speed 300 cm / min) was performed, the average test force value of the pressure-sensitive adhesive sheet and the glass substrate was measured, and this value was defined as the wet heat adhesion force (N / 25 mm).

(Step following capability)
The adhesive film according to each example and comparative example was cut to 3.0 cm × 4.0 cm, one release film was peeled off, and the exposed adhesive layer (adhesive sheet) was attached to a 50 μm-thick PET film. The release film was peeled off. The pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) where the pressure-sensitive adhesive film is exposed is pasted onto a glass substrate on which a 38 μm-thick Kapton tape (polyimide tape) has been pasted in advance, and pressure defoaming is performed at 40 ° C., 5 atm for 60 minutes. It processed and it was set as the evaluation sample.
About the produced sample, the level | step difference of glass and a Kapton tape was observed with the Nikon optical microscope, and the boundary space | gap width was measured. More specifically, as shown in FIG. 4, the configuration of the obtained sample corresponds to an embodiment in which the pressure-sensitive adhesive sheet 54 and the optical PET 56 are arranged on the glass substrate 50 on which the Kapton tape 52 is pasted. As shown in FIG. 4, a gap 58 is likely to occur between the glass substrate 50 and the adhesive sheet 54 at the step portion of the Kapton tape 52, and the boundary gap width does not contact the Kapton tape 52 and the adhesive sheet 54. A distance D on the glass substrate is intended.

(Evaluation of Haze (Whitening))
The release film on one side of the pressure-sensitive adhesive film obtained as described above is peeled off, the surface of the exposed pressure-sensitive adhesive sheet is bonded to an optical PET film (Toray Cosmo Shine), and the other release film is peeled off to form a glass. After being attached to (EAGLE XG manufactured by Dow Corning) and exposed to 40 ° C. and 5 atm for 20 minutes, it was further allowed to stand at 25 ° C. and 50% for 24 hours. Then, the value of Haze (haze) was measured using Tokyo Denshoku Co., Ltd. haze meter MODEL TC-H3. In addition, it shows that the degree of whitening is so small that the value of Haze is small.

<Evaluation results>
The results of the above evaluation tests are shown in Table 1.

As shown in Table 1, it was found that all the pressure-sensitive adhesive sheets according to the examples were excellent in wet heat adhesion and step following ability.
Moreover, the adhesive sheet which concerns on Examples 4-7 uses the thing with little gel as 2nd rubber (The gel component is 5 mass% or less in 100 mass% of 2nd rubber). Therefore, the pressure-sensitive adhesive sheets according to Examples 4 to 7 are examples in which a gel-rich one obtained by coordination polymerization as the second rubber (the gel component exceeds 5% by mass in 100% by mass of the second rubber) is used. It turned out that there is little whitening compared with 1-3. The gel component content was measured by the above-described method for measuring the gel fraction.
In the pressure-sensitive adhesive sheet-forming composition according to Examples 3 and 8, the ratio of the mass of the second rubber to the total mass of the first rubber, the second rubber and the polymerizable monomer exceeded 0.35. When preparing the composition for forming a sheet, an increase in viscosity and a decrease in the solubility of the second rubber were observed, and preparation was difficult as compared with other compositions for forming an adhesive sheet.
In the composition for forming an adhesive sheet according to Example 9, the difference in SP value between the second rubber and the HEA having the SP value farthest from the second rubber among the polymerizable monomers exceeds 0.4. Therefore, the compatibility between the second rubber and the polymerizable monomer was reduced, and white turbidity was observed. As a result, it was found that the evaluation of Haze was lowered despite the use of the second rubber having a small gel component.
Compared with the adhesive sheet of Example 6, the adhesive sheet of Example 10 had the tendency for wet heat adhesiveness to fall. This is because the content of the antioxidant in the pressure-sensitive adhesive sheet-forming composition of Example 10 is small, so that part of the polymerizable group reacts during the preparation of the pressure-sensitive adhesive sheet-forming composition, and is cured or crosslinked. This is thought to be due to the lack of.

According to the pressure-sensitive adhesive sheets according to Comparative Examples 1 and 2, since the content of the second rubber was less than 10% by mass, it was shown that wet heat adhesion deteriorates. In addition, the aspect of patent document 1 corresponds to the comparative example 2, and a desired effect is not acquired.
According to the pressure-sensitive adhesive sheet according to Comparative Example 3, since the first rubber was not contained, it was shown that the step following ability and the wet heat adhesion were deteriorated.

12 Adhesive Sheet 18 Capacitive Touch Panel Sensor 20 Protective Substrate 40 Display Device 50 Glass Substrate 52 Kapton Tape 54 Adhesive Sheet 56 Optical PET
58 Gap 100,200 Laminate 300,400 for touch panel Capacitive touch panel

Claims (12)

A pressure-sensitive adhesive sheet for a touch panel obtained by curing a pressure-sensitive adhesive sheet-forming composition containing rubber, a polymerizable monomer, a photopolymerization initiator, and a tackifier,
The rubber includes a first rubber having a weight average molecular weight of 1,000 to 100,000, and a second rubber having a weight average molecular weight of 250,000 to 2,000,000.
The pressure-sensitive adhesive sheet for touch panel, wherein the content of the second rubber is 10% by mass or more with respect to 100% by mass of the total mass of the pressure-sensitive adhesive sheet for touch panel.   The pressure-sensitive adhesive sheet for touch panel according to claim 1, wherein the second rubber contains at least one selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene, and modified polyisoprene.   The pressure-sensitive adhesive sheet for touch panel according to claim 1 or 2, wherein the first rubber contains at least one selected from the group consisting of polybutadiene, polyisoprene, modified polybutadiene, and modified polyisoprene.   The difference in SP value between the second rubber and the polymerizable monomer and the difference in SP value between the second rubber and the first rubber are both 0.4 or less. The adhesive sheet for touchscreens of any one of Claims.   In the pressure-sensitive adhesive sheet forming composition, the mass ratio of the second rubber to the total mass of the first rubber, the second rubber, and the polymerizable monomer is 0.25 to 0.35. The adhesive sheet for touchscreens of any one of 1-4. Furthermore, the composition for forming an adhesive sheet contains a phosphorus-based antioxidant,
The touch panel according to any one of claims 1 to 5, wherein in the composition for forming an adhesive sheet, a ratio of a mass of the phosphorus antioxidant to a mass of the second rubber is 0.006 or more. Adhesive sheet.   The pressure-sensitive adhesive sheet for a touch panel according to any one of claims 1 to 6, wherein the gel component in the second rubber is 5% by mass or less with respect to 100% by mass of the total mass of the second rubber.   The pressure-sensitive adhesive sheet for a touch panel according to any one of claims 1 to 7, wherein the second rubber is a rubber obtained by anionic polymerization.   The adhesive film for touchscreens which has the adhesive sheet for touchscreens of any one of Claims 1-8, and the peeling sheet arrange | positioned on the at least one surface of the said adhesive sheet for touchscreens.   The laminated body for touchscreens provided with the adhesive sheet for touchscreens of any one of Claims 1-8, and a capacitive touch panel sensor. In addition, with a protective substrate,
The laminated body for touchscreens of Claim 10 provided with the said protective substrate, the said adhesive sheet for touchscreens, and the said electrostatic capacitance type touchscreen sensor in this order.   An electrostatic capacitance type touch panel provided with an electrostatic capacitance type touch panel sensor, the adhesive sheet for touch panels according to any one of claims 1 to 8, and a display device in this order.

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