WO2015151224A1

WO2015151224A1 - Adhesive composition, adhesive, and adhesive sheet

Info

Publication number: WO2015151224A1
Application number: PCT/JP2014/059605
Authority: WO
Inventors: 祐樹小澤; 隆行荒井; 所司　悟
Original assignee: リンテック株式会社
Priority date: 2014-03-31
Filing date: 2014-03-31
Publication date: 2015-10-08
Also published as: JP6325653B2; JPWO2015151224A1

Abstract

An adhesive sheet (1) which is provided with two releasing sheets (12a, 12b) and an adhesive layer (11) that is sandwiched between the releasing sheets (12a, 12b) so as to be in contact with the releasing surfaces of the two releasing sheets (12a, 12b), and wherein the adhesive layer (11) is formed of an adhesive that is obtained by curing an adhesive composition which contains a (meth)acrylic acid ester polymer (A) and a cyclodextrin (B). This adhesive sheet (1) has an excellent balance between dielectric constant and resistance to wet heat whitening. It is preferable that the (meth)acrylic acid ester polymer (A) contains a monomer having a hydroxyl group and/or a monomer having a carboxyl group as a monomer unit that constitutes the polymer.

Description

Adhesive composition, adhesive and adhesive sheet

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

In various mobile electronic devices such as smartphones and tablet terminals in recent years, a touch panel is often used as a display panel. The types of touch panels include a resistive film method and a capacitance method, but the above-described mobile electronic devices mainly employ a capacitance method.

Here, in a capacitive touch panel, an electric field is formed on the entire surface of the touch panel, and position detection is performed by detecting changes in the surface charge of the part touched by the finger. Therefore, the dielectric constant of the member used for the touch panel is important for the response and malfunction of the sensor of the touch panel.

Therefore, in Patent Document 1, by reducing the dielectric constant of the pressure-sensitive adhesive layer, a branched alkyl group having 10 to 24 carbon atoms is attached to the end of the ester group in order to improve the response speed of the touch panel and prevent malfunction. A pressure-sensitive adhesive comprising a (meth) acrylic polymer obtained by polymerizing a monomer component containing 19 to 99.5% by weight of an alkyl (meth) acrylate having an alkyl group is proposed.

JP 2012-246477 A

Patent Document 1 attempts to achieve a low dielectric constant of the pressure-sensitive adhesive layer by using a low-polarity monomer. However, such monomers are special and not readily available, and are not suitable for mass production. Moreover, since the (meth) acrylic polymer of Patent Document 1 has low polarity, there arises a problem that the adhesiveness of the obtained adhesive to a glass plate, an acrylic plate, or the like is deteriorated.

On the other hand, when a 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 becomes white and transparency decreases. There is a problem of “whitening”. Therefore, the pressure-sensitive adhesive layer that can be used is limited. Moreover, if the composition of the (meth) acrylic polymer constituting the pressure-sensitive adhesive layer is changed in order to improve the heat and heat whitening resistance, the dielectric constant of the pressure-sensitive adhesive layer tends to increase.

The present invention has been made in view of the actual situation as described above, and does not change the dielectric constant of the pressure-sensitive adhesive layer resulting from the (meth) acrylic acid ester polymer in the pressure-sensitive adhesive composition, and is resistant to heat and heat whitening. It is an object of the present invention to provide a pressure-sensitive adhesive composition capable of improving the property, and a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet obtained using the pressure-sensitive adhesive composition.

In order to achieve the above object, first, the present invention provides a pressure-sensitive adhesive composition comprising a (meth) acrylic acid ester polymer (A) and a cyclodextrin (B). (Invention 1).

The adhesive composition according to the invention (Invention 1) can suppress wet heat whitening in the obtained adhesive by containing the cyclodextrins (B). On the other hand, since cyclodextrins (B) are compounds with a low dielectric constant, even if cyclodextrin (B) is contained in the adhesive composition, an increase in dielectric constant is suppressed in the obtained adhesive. Therefore, the obtained pressure-sensitive adhesive has improved wet heat whitening resistance without changing the dielectric constant, and has an excellent balance between dielectric constant and wet heat whitening resistance.

In the said invention (invention 1), it is preferable that the said (meth) acrylic acid ester polymer (A) contains the monomer which has a hydroxyl group, and / or the monomer which has a carboxyl group as a monomer unit which comprises the said polymer. (Invention 2).

In the above invention (Invention 2), the (meth) acrylic acid ester polymer (A) contains 0.1 to 15% by mass of the monomer having a hydroxyl group as a monomer unit constituting the polymer, or It is preferable to contain 0.1 to 8% by mass of a monomer having a carboxyl group (Invention 3).

In the above inventions (Inventions 1 to 3), the content of cyclodextrins (B) in the adhesive composition is 0.1 to 20 masses per 100 parts by mass of the (meth) acrylic acid ester polymer (A). Part (Invention 4).

In the above inventions (Inventions 1 to 4), the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 200,000 to 900,000 (Invention 5).

In the above inventions (Inventions 1 to 5), the cyclodextrins (B) are preferably modified cyclodextrins (Invention 6).

In the above invention (Invention 6), the modified cyclodextrin is preferably a partially methylated cyclodextrin (Invention 7).

In the above inventions (Inventions 6 and 7), the degree of substitution of the modified cyclodextrin is preferably 0.2 to 2.5 (Invention 8).

In the above inventions (Inventions 1 to 8), it is preferable to further contain at least one of a crosslinking agent (C) and an active energy ray-curable compound (D) (Invention 9).

Secondly, the present invention provides an adhesive obtained by curing the above-mentioned adhesive composition (Invention 1 to 9) (Invention 10).

In the said invention (invention 10), it is preferable that the dielectric constant in 0.1 MHz of the said adhesive is 9.0 or less (invention 11).

In the above inventions (Inventions 10 and 11), the haze value is preferably 0.1 to 2.0% (Invention 12).

Thirdly, 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 10 to 12) is provided (Invention 13).

In the said invention (invention 13), 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 14).

The pressure-sensitive adhesive composition according to the present invention forms a pressure-sensitive adhesive with improved moisture and heat whitening resistance without changing the dielectric constant of the pressure-sensitive adhesive layer resulting from the (meth) acrylic acid ester polymer in the composition. can do. Moreover, the pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention have an excellent balance between dielectric constant and resistance to moist heat whitening.

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 composition]
The pressure-sensitive adhesive composition according to this embodiment (hereinafter referred to as “pressure-sensitive adhesive composition P”) contains a (meth) acrylic acid ester polymer (A) and cyclodextrins (B), Furthermore, it contains at least one of a crosslinking agent (C) and an active energy ray-curable compound (D). 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”.

In the pressure-sensitive adhesive composition P according to this embodiment, a predetermined amount of hydroxyl groups derived from the cyclodextrins (B) remains in the obtained pressure-sensitive adhesive by containing the cyclodextrins (B). A hydroxyl group is a hydrophilic group, and when such a hydrophilic group is present in a pressure-sensitive adhesive, even if the pressure-sensitive adhesive is placed under a high temperature and high humidity condition, it penetrates into the pressure sensitive adhesive under the high temperature and high humidity condition. As a result, the whitening of the pressure-sensitive adhesive is suppressed. Therefore, it is not necessary to change the composition or the like of the (meth) acrylic acid ester polymer constituting the pressure-sensitive adhesive layer in order to improve the moisture and heat whitening resistance.

On the other hand, unlike the other hydrophilic group-containing compounds, cyclodextrins (B) are compounds having a low dielectric constant. Therefore, even if cyclodextrin (B) is contained in adhesive composition P, the resulting adhesive is obtained. An increase in dielectric constant is suppressed in the agent. Therefore, the resulting pressure-sensitive adhesive has improved heat and heat whitening resistance while suppressing changes in the dielectric constant due to the (meth) acrylic acid ester polymer (A). The balance is excellent.

1. (Meth) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) is an adhesive main agent in the adhesive composition P. The (meth) acrylic acid ester polymer (A) usually contains a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms as the monomer unit constituting the polymer, preferably the main component Contained as. Thereby, the obtained adhesive can express preferable adhesiveness.

Examples of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n- (meth) acrylate. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid esters having an alkyl group having 1 to 8 carbon atoms are preferred, such as methyl (meth) acrylate, n-butyl (meth) acrylate and (meth) acrylic. The acid 2-ethylhexyl is particularly preferred. 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) is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer, from the viewpoint of imparting adhesiveness. The content is preferably 30% by mass or more, particularly preferably 60% by mass or more, and more preferably 80% by mass or more. When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer and / or a carboxyl group-containing monomer, the content of the (meth) acrylic acid alkyl ester whose alkyl group has 1 to 20 carbon atoms The upper limit is preferably the remainder excluding the hydroxyl group-containing monomer and the carboxyl group-containing monomer.

The (meth) acrylic acid ester polymer (A) preferably contains a monomer having a hydroxyl group and / or a monomer having a carboxyl group as a monomer unit constituting the polymer. The (meth) acrylic acid ester polymer (A) containing a monomer having a hydroxyl group and / or a monomer having a carboxyl group as a monomer unit is excellent in compatibility with the cyclodextrins (B). Moreover, when the adhesive composition P contains a crosslinking agent (C), the reactivity with the crosslinking agent is excellent.

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, the compatibility between the resulting (meth) acrylic acid ester polymer (A) and the cyclodextrins (B), and the reactivity with the hydroxyl group crosslinking agent (C) when it contains a crosslinking agent (C), From the viewpoint of copolymerization with other monomers, 2-hydroxyethyl (meth) acrylate 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. Above all, the compatibility of the resulting (meth) acrylic acid ester polymer (A) with the cyclodextrins (B), and the reactivity with the carboxyl group crosslinking agent (C) when it contains a crosslinking agent (C). (Meth) acrylic acid is preferable from the viewpoint of copolymerization with other monomers, and acrylic acid is particularly preferable. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) contains 0.1 to 15% by mass, particularly 0.5 to 12% by mass, more preferably 1 to 10% by mass of a hydroxyl group-containing monomer as a monomer unit constituting the polymer. %, Or 0.1 to 8% by mass, particularly 1 to 5% by mass of the carboxyl group-containing monomer.

When the content of the hydroxyl group-containing monomer is 15% by mass or less or the content of the carboxyl group-containing monomer is 8% by mass or less, the resulting adhesive has a sufficiently low dielectric constant. Here, since the adhesive composition P according to this embodiment contains the cyclodextrins (B), even when the content of the hydroxyl group-containing monomer or the carboxyl group-containing monomer is defined in the low numerical range as described above, The resulting pressure-sensitive adhesive has excellent moisture and heat whitening resistance.

On the other hand, when the content of the hydroxyl group-containing monomer is 0.1% by mass or more, or the content of the carboxyl group-containing monomer is 0.1% by mass or more, the pressure-sensitive adhesive composition P is a crosslinking agent (C ), The reaction with the crosslinking agent (C) is good.

The (meth) acrylic acid ester polymer (A) may contain other monomers as a monomer unit 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 hydroxyl group-containing monomer or the carboxyl 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 Non-crosslinkable acrylamide such as acrylic ester, acrylamide, methacrylamide, etc. Non-crosslinkable tertiary such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate Examples thereof include (meth) acrylic acid ester having an amino group, vinyl acetate, 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 (meth) acrylic acid ester polymer (A) preferably has a weight average molecular weight of 200,000 to 900,000, particularly preferably 250,000 to 700,000, and more preferably 300,000 to 600,000. preferable. In addition, the weight average molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

The weight-average molecular weight of the (meth) acrylic acid ester polymer (A), which is the main component of the pressure-sensitive adhesive composition P, is 200,000 or more, so that the pressure-sensitive adhesive obtained has sufficient cohesive strength and is durable. It will be excellent. On the other hand, in the capacitive touch panel, in order to conceal the wiring layer, a printed layer that becomes a step is often provided at the peripheral portion of the cover material, but the weight average of the (meth) acrylate polymer (A) When the molecular weight is 900,000 or less, the followability to the printing step is good.

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

2. Cyclodextrins (B)
Cyclodextrin is a cyclic oligosaccharide having glucose as a structural unit, and has 3 hydroxyl groups per glucose structural unit. In the present specification, cyclodextrins and modified dextrins in which some of the hydroxyl groups of cyclodextrins are substituted with other functional groups are collectively referred to as “cyclodextrins”. The cyclodextrins (B) used in the present embodiment exclude those constituting a ring component having a rotaxane structure.

In addition to the (meth) acrylic acid ester polymer (A) described above, the pressure-sensitive adhesive composition P according to the present embodiment contains cyclodextrins (B), so that the resulting pressure-sensitive adhesive has heat and heat whitening resistance. It is excellent, specifically, whitening is suppressed when it is returned to room temperature and normal humidity after being subjected to high temperature and high humidity conditions (for example, under conditions of 85 ° C. and 85% RH for 72 hours).

On the other hand, since cyclodextrins (B) are compounds having a low dielectric constant, in the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P, an increase in the dielectric constant is suppressed, and the balance between the dielectric constant and resistance to moist heat whitening is achieved. It will be excellent.

As cyclodextrins, those having 5 or more glucose structural units are known. However, as cyclodextrins (B) used in this embodiment, α-cyclodextrins (α-cyclodextrins having 6 structural units) are known. Dextrin and modified α-cyclodextrin (the same shall apply hereinafter)), β-cyclodextrins having a structural unit of 7 and γ-cyclodextrins having a structural unit of 8 can be preferably used. Β-cyclodextrins are preferred from the viewpoint of improving thermal whitening properties and lowering the dielectric constant.

As cyclodextrins (B), from the viewpoint of compatibility with other components in the adhesive composition P (for example, (meth) acrylic acid ester polymer (A), etc.), some of the hydroxyl groups of cyclodextrin are It is preferable to use a modified cyclodextrin substituted with another functional group. Here, examples of the other functional group include an alkoxy group such as a methoxy group and an ethoxy group, and an acyl group such as an acetyl group. Among these, a methoxy group is particularly preferable from the viewpoint of compatibility with the (meth) acrylic acid ester polymer (A) and the diluent solvent. A cyclodextrin in which one or a plurality of hydroxyl groups are left and another hydroxyl group is substituted with a methoxy group is a partially methylated cyclodextrin.

The degree of substitution in the modified cyclodextrin is preferably 0.2 to 2.5, particularly 0.5 to 2.0, from the viewpoint of compatibility with the other components in the adhesive composition P. preferable. Here, the degree of substitution of the modified cyclodextrin in this specification is the number of hydroxyl groups substituted with other functional groups per glucose constituent unit, and all three hydroxyl groups in one glucose constituent unit are substituted. If it is done, it becomes 3.0.

The content of the cyclodextrins (B) in the adhesive composition P is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). The amount is preferably 5 to 10 parts by mass, and more preferably 1 to 4 parts by mass. When the content of the cyclodextrins (B) is 100 parts by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), the moisture and heat whitening resistance of the adhesive obtained from the adhesive composition P Is more preferable, and when it is 20 parts by mass or less, the pressure-sensitive adhesive properties and optical properties of the pressure-sensitive adhesive obtained are preferable.

3. Crosslinking agent (C) and active energy ray curable compound (D)
The pressure-sensitive adhesive composition P preferably further contains at least one of a crosslinking agent (C) and an active energy ray-curable compound (D). When the adhesive composition P contains at least one of the crosslinking agent (C) and the active energy ray-curable compound (D), the cohesive force of the obtained adhesive is improved.

(1) Crosslinking agent (C)
The pressure-sensitive adhesive composition P further contains a cross-linking agent (C), thereby cross-linking the (meth) acrylic acid ester polymer (A) to form a three-dimensional network structure. Improve durability.

The crosslinking agent (C) may be any one that reacts with the reactive group (hydroxyl group or carboxyl group) of the (meth) acrylic acid ester polymer (A). For example, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent. , Amine crosslinker, melamine crosslinker, aziridine crosslinker, hydrazine crosslinker, aldehyde crosslinker, oxazoline crosslinker, metal alkoxide crosslinker, metal chelate crosslinker, metal salt crosslinker, ammonium Examples thereof include a salt-based cross-linking agent. A crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group. When the (meth) acrylic acid ester polymer (A) contains a carboxyl group-containing monomer, at least one selected from an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent excellent in reactivity with a carboxyl group is used as a crosslinking agent ( It is preferable to use as C), and it is particularly preferable to use an epoxy-based crosslinking agent.

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, etc. , 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 is preferable from the viewpoint of reactivity with hydroxyl groups.

Examples of the epoxy-based 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.

The content of the crosslinking agent (C) in the pressure-sensitive adhesive composition P is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), particularly 0. .05 to 1 part by mass is preferred. When the content of the crosslinking agent (C) is 0.01 parts by mass or more, the cohesive force and durability of the obtained pressure-sensitive adhesive are more excellent. On the other hand, when the content of the crosslinking agent (C) is 5 parts by mass or less, the pressure-sensitive adhesive is obtained when the hydroxyl group or carboxyl group of the (meth) acrylic acid ester polymer (A) reacts with the crosslinking agent (C). The hydroxyl group or carboxyl group in the residue remains sufficiently, and the moisture and heat whitening resistance is good. In addition, when the content of the crosslinking agent (C) is 5 parts by mass or less, the degree of crosslinking is not excessive, and the followability to a printing step becomes good.

(2) Active energy ray-curable compound (D)
The pressure-sensitive adhesive composition P further contains the active energy ray-curable compound (D), so that the obtained pressure-sensitive adhesive is excellent in durability when it is cured by irradiation with active energy rays.

The active energy ray-curable compound (D) may be either a monomer or an oligomer, or a mixture thereof. Among them, a polyfunctional acrylate monomer having a molecular weight of 1000 or less that is excellent in compatibility with the (meth) acrylic acid ester polymer (A) and the like can be preferably exemplified.

Examples of polyfunctional acrylate monomers having a molecular weight of 1000 or less include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol diene. (Meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified Bifunctional type such as di (meth) acrylate phosphate, di (acryloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, etc .; trimethylolpropane tri (meth) acrylate Rate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanate Trifunctional type such as nurate and ε-caprolactone modified tris- (2- (meth) acryloxyethyl) isocyanurate; tetrafunctional type such as diglycerin tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; propionic acid modified 5-functional type such as dipentaerythritol penta (meth) acrylate; dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate A trifunctional (acryloxyethyl) isocyanurate is preferable from the viewpoint of reactivity. These may be used individually by 1 type and may be used in combination of 2 or more type.

As the active energy ray-curable compound (D), an active energy ray-curable acrylate oligomer can also be used. The acrylate oligomer preferably has a weight average molecular weight of 50,000 or less. Examples of such acrylate oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate.

The active energy ray-curable compound (D) can be used by selecting one from among the above-mentioned polyfunctional acrylate monomers and acrylate oligomers, or can be used in combination of two or more. It can also be used in combination with other active energy ray-curable components.

When the adhesive composition P contains the active energy ray-curable compound (D), the content of the active energy ray-curable compound (D) is 100 parts by mass of the (meth) acrylic acid ester polymer (A). On the other hand, the amount is preferably 1 to 25 parts by mass, particularly preferably 3 to 20 parts by mass, and further preferably 5 to 15 parts by mass. When the content of the active energy ray-curable compound (D) is within the above range, the resulting adhesive has excellent durability, and the adhesiveness of the (meth) acrylate polymer (A). Is maintained well.

4). Various Additives The adhesive composition P is optionally added with various additives such as a photopolymerization initiator, a silane coupling agent, a refractive index adjusting agent, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, a light It may contain stabilizers, softeners, fillers and the like.

When the adhesive composition P contains the active energy ray-curable compound (D), when ultraviolet rays are used as the active energy ray for curing the adhesive composition P, the adhesive composition P is a photopolymerization initiator. It is preferable to contain. By containing the photopolymerization initiator, the pressure-sensitive adhesive composition P containing the active energy ray-curable compound (D) can be efficiently cured, and the polymerization curing time and active energy ray irradiation amount are reduced. be able to.

Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethyla Nobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2, 4,6-trimethylbenzoyl-diphenyl-phosphine oxide and the like. These may be used alone or in combination of two or more.

The photopolymerization initiator is preferably used in an amount in the range of 0.1 to 30 parts by mass, particularly 1 to 20 parts by mass with respect to 100 parts by mass of the active energy ray-curable compound (D).

In addition, the adhesive composition P preferably contains a silane coupling agent from the viewpoint of improving the adhesiveness of the obtained adhesive. As the silane coupling agent, an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with other components in the pressure-sensitive adhesive composition P, and having light transmittance is preferable.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- ( 3,4-epoxycyclohexyl) silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane Amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, etc. Elemental compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of them, and alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane Examples include condensates with silicon compounds. These may be used individually by 1 type and may be used in combination of 2 or more type.

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). The amount is preferably 0.1 to 1.0 part by mass, and more preferably 0.2 to 0.5 part by mass.

5. Production of Adhesive Composition Adhesive composition P produced (meth) acrylic acid ester polymer (A), and obtained (meth) acrylic acid ester polymer (A) and cyclodextrins (B). And a crosslinking agent (C), an active energy ray-curable compound (D), other additives, and the like, if desired.

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

In the polymerization step, the weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

Once the (meth) acrylic acid ester polymer (A) is obtained, the solution of the (meth) acrylic acid ester polymer (A) is added to the cyclodextrin (B), and optionally a crosslinking agent (C), active energy rays. A curable compound (D), another additive, a diluting solvent, and the like are added and mixed thoroughly to obtain a pressure-sensitive adhesive composition P (coating solution) diluted with a solvent.

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, cellosolve solvents such as ethyl cellosolve and the like are used.

The concentration / viscosity of the coating solution prepared in this manner is not particularly limited as long as it is within a coatable range, and can be appropriately selected according to the situation. For example, dilution is performed so that the concentration of the adhesive composition P is 10 to 40% by 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.

[Adhesive]
The pressure-sensitive adhesive according to this embodiment is obtained by curing the pressure-sensitive adhesive composition P. When the pressure-sensitive adhesive composition P does not contain the active energy ray-curable compound (D), the pressure-sensitive adhesive composition P is applied to the release surface of the release sheet and then dried, preferably heat-treated to be cured. An adhesive can be obtained. After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH) as necessary.

Moreover, when the adhesive composition P contains the active energy ray-curable compound (D), the adhesive composition P is applied to the release surface of the release sheet and then dried, preferably heat-treated, and then activated. An adhesive can be obtained by irradiating and curing energy rays.

As a method for applying the coating solution of the adhesive composition P, 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.

Although drying of the adhesive composition P may be performed by air drying, it is usually performed by heat treatment (preferably hot air drying). In the case of performing the heat treatment, the heating temperature is preferably 50 to 150 ° C., particularly preferably 70 to 120 ° C. The heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

As active energy rays, ultraviolet rays, electron beams and the like are usually used. The dose of the active energy ray varies depending on the type of the energy ray, for example, in the case of ultraviolet rays, preferably 50 ~ 1000mJ / cm ² in quantity, especially 100 ~ 500mJ / cm ² preferably. In the case of an electron beam, about 10 to 1000 krad is preferable.

When the adhesive composition P contains a crosslinking agent (C), the (meth) acrylic acid ester polymer (A) is crosslinked by the crosslinking agent (C) by drying (heating treatment) of the adhesive composition P. To form a three-dimensional network structure. Moreover, when the adhesive component of the adhesive composition P contains the active energy ray-curable compound (D), by irradiating the adhesive composition P with the active energy ray, a plurality of active energy ray-curable compounds (D) are obtained. It is presumed that a three-dimensional network structure is formed by bonding to each other, and a structure entangled with the (meth) acrylic acid ester polymer (A) is formed.

The dielectric constant at 0.1 MHz of the pressure-sensitive adhesive according to this embodiment is preferably 9.0 or less. When the dielectric constant at 0.1 MHz of the pressure-sensitive adhesive according to this embodiment is 9.0 or less, the touch panel manufactured using the pressure-sensitive adhesive can contribute to suppression of malfunction and improvement of responsiveness. it can.

Here, the pressure-sensitive adhesive according to the present embodiment is such that the pressure-sensitive adhesive composition P contains a cyclodextrin (B), so that the pressure-sensitive adhesive obtained in the pressure-sensitive adhesive composition P contains a cyclodextrin (B). In addition, it exhibits excellent moisture and heat whitening resistance without greatly changing the dielectric constant. In the (meth) acrylic acid ester polymer (A) of the adhesive composition P, the monomer unit constituting the polymer has a hydroxyl group-containing monomer content of 15% by mass or less, or a carboxyl group-containing monomer. When the content is 8% by mass or less, the obtained adhesive has a sufficiently low dielectric constant, and the above-described dielectric constant at 0.1 MHz can be easily achieved. In addition, the measuring method of the dielectric constant of an adhesive is as showing to the test example mentioned later.

The gel fraction of the pressure-sensitive adhesive according to this embodiment is preferably 15 to 95%, particularly preferably 40 to 90%, and more preferably 60 to 85%. When the gel fraction is 15% or more, the cohesive force of the pressure-sensitive adhesive is sufficient and the durability is excellent. On the other hand, when the gel fraction is 95% or less, excellent step following performance is exhibited and the adhesiveness can be kept high. 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. However, the

release sheets

12a and 12b in the pressure-sensitive adhesive sheet 1 are not essential components, and are peeled and removed when the pressure-sensitive adhesive sheet 1 is used. 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 formed by bridge | crosslinking the adhesive composition P mentioned above. The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) is preferably 10 to 300 μm, particularly preferably 25 to 250 μm, and more preferably 50 to 100 μm. When the thickness of the pressure-sensitive adhesive layer 11 is 10 μm or more, excellent adhesive force is sufficiently exhibited, and when the thickness of the pressure-sensitive adhesive layer 11 is 300 μm or less, workability is improved. Further, when the thickness of the pressure-sensitive adhesive layer 11 is 25 to 100 μm, it is suitable for optical applications, particularly for touch panel applications. The pressure-sensitive adhesive layer 11 may be formed as a single layer or may be formed by laminating a plurality of layers.

The haze value of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7136: 2000) is preferably 2.0% or less, particularly preferably 1.5% or less, and more preferably 1.0%. The following is preferable. When the haze value is 2.0% or less, the pressure-sensitive adhesive according to this embodiment has very high transparency and is suitable for optical applications. In addition, it is especially preferable that the haze value of the pressure-sensitive adhesive layer 11 is within the above range even after an evaluation test for resistance to heat and whitening described later.

(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.

The release surface of the

release sheets

12a and 12b (particularly the surface in contact with the pressure-sensitive adhesive layer 11) is preferably subjected to a release 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.

The thickness of the

release sheets

12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

(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 the adhesive composition P is cured to form an application layer, the release surface of the other release sheet 12b (or 12a) is superimposed on the application 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 cure 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.

As a method of applying the coating liquid of the above-mentioned adhesive composition P, 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.

(4) Adhesive strength A transparent conductive film made of tin-doped indium oxide (ITO) is provided on the pressure-sensitive adhesive layer 11 side of the laminate obtained by laminating the pressure-sensitive adhesive layer 11 on a base material made of a polyethylene terephthalate film having a thickness of 100 μm. When the obtained transparent conductive film is attached to the transparent conductive film, the adhesive strength of the laminate to the transparent conductive film is preferably 5 to 80 N / 25 mm, particularly 10 to 70 N / 25 mm. And more preferably 15 to 50 N / 25 mm. When the adhesive force is in the above range, the constituent members of the touch panel are securely bonded.

In addition, although the adhesive force here means the adhesive force measured by the 180 degree peeling method according to JIS２００Z0237: 2009, the measurement sample has a width of 25 mm and a length of 100 mm, and the measurement sample is attached. After being applied to the body by applying pressure at 0.5 MPa and 50 ° C. for 20 minutes, the sample was left for 24 hours under conditions of normal pressure, 23 ° C. and 50% RH, and then measured at a peeling rate of 300 mm / min. To do.

(5) 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 of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, or may be formed of 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 first film sensor 5a and the second film sensor 5b are each generally composed of a base film 51 and a 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. .

In the present embodiment, the transparent conductive film 52 of the second film sensor 5b is located above the second film sensor 5b in FIG. On the other hand, the transparent conductive film 52 of the first film sensor 5a is positioned on the upper side of the first film sensor 5a in FIG. 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 constituting the printing layer 7 is not particularly limited, and a 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 (height of the step) of the printing layer 7 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 preferably 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 from the structure, and the structure is bonded to the display module 3 so that the exposed adhesive layer 4a is in contact with the display module 3. Thereby, the touch panel 2 shown in FIG. 2 is manufactured.

In the touch panel 2 described above, since the dielectric constant of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 is low, malfunction caused by the pressure-sensitive adhesive layer 11 is effectively suppressed, and the responsiveness of the touch panel sensor is improved. is doing. Furthermore, since the pressure-sensitive adhesive constituting 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.

Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

[Example 1]
1. Preparation of (meth) acrylic acid ester polymer 70 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate and 10 parts by weight of 2-hydroxyethyl acrylate were copolymerized to give 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 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) (in terms of solid content; the same applies hereinafter) and ethanol as cyclodextrins (B) Partially methylated β-dextrin diluted 10-fold (manufactured by Junsei Co., Ltd., product name “methyl-β-cyclodextrin”, substitution degree 1.6 to 1.9) 0.1 part by mass, and as crosslinking agent (C) 0.25 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name “Coronate L”) and 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent Product name “KBM-403”) 0.25 parts by mass, sufficiently stirred, diluted with methyl ethyl ketone to give a solid content concentration of 36% by mass To obtain a coating solution of the composition.

Here, Table 1 and Table 2 show the composition of the adhesive composition including Examples and Comparative Examples described later. Details of the abbreviations described in Table 1 and Table 2 are as follows.
[(Meth) acrylic acid ester polymer]
BA: n-butyl acrylate MA: methyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate AA: acrylic acid

3. Manufacture of pressure-sensitive adhesive sheet Peeling of a heavy-peelable release sheet (product name “SP-PET752150”, manufactured by Lintec Corporation) from a polyethylene terephthalate film 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 type release sheet (product name “SP-PET382120” manufactured by Lintec Co., Ltd.) 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 was obtained as a laminate composed of a heavy release type release sheet / adhesive layer (thickness: 50 μm) / light release type release sheet. 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 (hereinafter the same).

[Examples 2 and 3, Comparative Examples 1 and 2]
Table 1 shows the ratio of each monomer constituting the (meth) acrylic acid ester polymer (A), the weight average molecular weight of the (meth) acrylic acid ester polymer (A), and the blending amount of the cyclodextrins (B). A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the above was changed.

Example 4
1. Preparation of (meth) acrylate polymer Polymer (meth) acrylate polymer (A) was prepared by copolymerizing 77 parts by weight of n-butyl acrylate, 20 parts by weight of methyl methacrylate and 3 parts by weight of acrylic acid. did. 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 of 600,000.

2. Preparation of adhesive composition 100 parts by mass of the obtained (meth) acrylic acid ester polymer (A) and partially methylated β-dextrin diluted 10 times with ethanol as cyclodextrins (B) (manufactured by Junsei Co., Ltd.) , Product name “methyl-β-cyclodextrin”, substitution degree 1.6 to 1.9) 1.0 part by mass and tris (acryloxyethyl) isocyanurate (Toa) as active energy ray-curable compound (D) A mixture of 5.0 parts by mass (product name “Aronix M-315” manufactured by Synthetic Co., Ltd.) and benzophenone and 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator in a mass ratio of 1: 1 (Ciba Specialty Chemicals) 1.0 part by mass, product name “Irgacure 500” manufactured by the company, and 3-glycidoxypropylate as a silane coupling agent Mixing with 0.25 parts by mass of methoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBM-403”), sufficiently stirring, and diluting with methyl ethyl ketone, a sticky composition having a solid content concentration of 36% by mass A coating solution of the product was obtained.

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, and heavy release was performed. A pressure-sensitive adhesive sheet having a structure of mold release sheet / coating layer (thickness: 50 μm) / light release release sheet was prepared. Then, the adhesive sheet was obtained by irradiating an ultraviolet-ray through the peeling sheet on the following conditions, hardening the said application layer and making it an adhesive layer. In addition, the thickness of the formed adhesive layer was 50 micrometers.
<Ultraviolet irradiation conditions>
Fusion Co. electrodeless lamp H bulb used, illuminance 600 mW / cm ^2, light quantity 150 mJ / cm ²
・ UV illuminance / light meter uses "UVPF-36" manufactured by Eye Graphics.

[Examples 5 to 6, Comparative Examples 3 to 4]
Table 2 shows the ratio of each monomer constituting the (meth) acrylic acid ester polymer (A), the weight average molecular weight of the (meth) acrylic acid ester polymer (A), and the blending amount of the cyclodextrins (B). A pressure-sensitive adhesive sheet was produced in the same manner as in Example 4 except that the above was changed.

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 adhesive strength)
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 (PET A4300, manufactured by Toyobo Co., Ltd., thickness: 100 μm) having an easy adhesion layer. Bonded to the adhesive layer. The laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

On the other hand, a transparent conductive film (Oike Industry Co., Ltd., ITO film, thickness: 125 μm) in which a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) is provided on one side of a polyethylene terephthalate (PET) film The PET film was fixed to the glass plate so that the PET film side was in contact with the glass plate.

The heavy release type release sheet was peeled off from the sample, and the exposed adhesive layer was attached to the transparent conductive film. This pasting was performed by pressurizing at a pressure of 0.5 MPa for 20 minutes under a temperature condition of 50 ° C.

Then, after leaving for 24 hours under conditions of normal pressure, 23 ° C. and 50% RH, using a tensile tester (Orientec Co., Ltd., product name “Tensilon”), peel speed according to JIS Z0237: 2009 The adhesive strength (N / 25 mm) was measured under the conditions of 300 mm / min and peeling angle of 180 °. The results are shown in Table 3 and Table 4.

[Test Example 2] (Gel fraction measurement)
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 3 and Table 4.

[Test Example 3] (Measurement of haze value)
About the adhesive layer (thickness: 50 micrometers) of the adhesive sheet obtained by the Example and the comparative example, according to JISK7136: 2000 using a haze meter (Nippon Denshoku Industries Co., Ltd. product name "NDH2000"). The haze value (%) was measured. The results are shown in Table 3 and Table 4.

[Test Example 4] (Heat and heat whitening resistance evaluation)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were sandwiched between two soda lime glasses (thickness: 1.1 mm) to obtain a laminate. About the laminated body, haze value (%) was measured according to JISK7136: 2000 using the haze meter (The Nippon Denshoku Industries Co., Ltd. make, product name "NDH2000").

Next, the laminate was stored for 72 hours under wet heat conditions of 85 ° C. and 85% RH. Then, it returns to normal temperature normal humidity of 23 degreeC and 50% RH, About the said laminated body, using a haze meter (the Nippon Denshoku Industries Co., Ltd. make, product name "NDH2000"), haze value (in accordance with JIS K7136: 2000) %). In addition, the said haze value was measured within 30 minutes after returning a laminated body to normal temperature normal humidity.

Based on the above results, a haze value increase (points) after the wet heat condition was calculated by subtracting the haze value before the wet heat condition from the haze value after the wet heat condition. Based on the obtained increase in haze value, the resistance to moist heat whitening was evaluated according to the following criteria. The results are shown in Table 3 and Table 4.
A: Very good (haze increase after wet heat condition is less than 1.0 point)
○: Good (the increase in haze value after wet heat conditions is 1.0 point or more and less than 1.5 point)
Δ: within suitability value (increase in haze value after wet heat condition is 1.5 points or more and less than 2.0 points)
X: Defect (increased haze value after wet heat condition is 2.0 points or more)

[Test Example 5] (Calculation of dielectric constant)
After forming a 100 μm thick adhesive layer on one side of a 50 μm thick polyethylene terephthalate film in the same manner as in the Examples and Comparative Examples, a 50 μm thick polyethylene terephthalate film was bonded to the adhesive layer. It cut | judged to 50 mm x 50 mm. The obtained laminate was measured for capacitance (C1) using an impedance analyzer (manufactured by Hewlett-Packard Japan, HP-4194A). Further, two polyethylene terephthalate films having a thickness of 50 μm were stacked and cut into 50 mm × 50 mm, and the capacitance (C2) was measured in the same manner. And C2 was subtracted from C1, and the electrostatic capacitance (C3) of the adhesive was calculated. Based on this capacitance C3, the dielectric constant ε _s of the adhesive was calculated from the following formula. The results are shown in Table 3 and Table 4.

ε _s = (C3 × d) / (ε ₀ × S)
ε _s : dielectric constant of adhesive ε ₀ : dielectric constant of vacuum (8.854 × 10 ⁻¹² )
C3: Capacitance of the adhesive S: Area of the adhesive layer d: Thickness of the adhesive layer

[Test Example 6] (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, and 15 μm. Next, irradiation with ultraviolet rays (80 W / cm ² , ² metal halide lamps, lamp height 15 cm, belt speed 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, and 15 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 (PET A4300, thickness: 100 μm) having an easy adhesion layer. 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 After the obtained evaluation sample was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, it was further stored for 72 hours under wet heat conditions of 85 ° C. and 85% RH. . Thereafter, the pressure-sensitive adhesive layer (particularly in the vicinity of the step due to the printing layer) was visually confirmed, and the step following property was evaluated according to the following criteria. The results are shown in Table 3 and Table 4.
(Double-circle): There was no bubble, floating, and peeling at all.
○: Only bubbles with a diameter of 0.2 mm or less were generated.
X: Bubbles with a diameter of more than 0.2 mm, floating or peeling occurred.

As can be seen from Tables 3 and 4, the pressure-sensitive adhesive sheets obtained in the examples were excellent in moisture and heat whitening resistance while keeping the dielectric constant low. Moreover, the adhesive sheets obtained in the examples and comparative examples were all good in adhesive strength, haze, and step following ability.

The pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention can be suitably used for producing a touch panel with few malfunctions.

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

(Meth) acrylic acid ester polymer (A),
A pressure-sensitive adhesive composition containing cyclodextrins (B).
The (meth) acrylic acid ester polymer (A) contains a monomer having a hydroxyl group and / or a monomer having a carboxyl group as a monomer unit constituting the polymer. Adhesive composition.
The (meth) acrylic acid ester polymer (A) contains 0.1 to 15% by mass of the monomer having a hydroxyl group as a monomer unit constituting the polymer, or 0. The pressure-sensitive adhesive composition according to claim 2, containing 1 to 8% by mass.
The content of cyclodextrins (B) in the adhesive composition is 0.1 to 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). The pressure-sensitive adhesive composition according to any one of 1 to 3.
The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 200,000 to 900,000.
The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the cyclodextrins (B) are modified cyclodextrins.
The pressure-sensitive adhesive composition according to claim 6, wherein the modified cyclodextrin is a partially methylated cyclodextrin.
The pressure-sensitive adhesive composition according to claim 6 or 7, wherein the degree of substitution of the modified cyclodextrin is 0.2 to 2.5.
The pressure-sensitive adhesive composition according to any one of claims 1 to 8, further comprising at least one of a crosslinking agent (C) and an active energy ray-curable compound (D).
A pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition according to any one of claims 1 to 9.
The pressure-sensitive adhesive according to claim 10, wherein the pressure-sensitive adhesive has a dielectric constant of 0.1 or less at 0.1 MHz.
12. The pressure-sensitive adhesive according to claim 10, wherein the haze value is 0.1 to 2.0%.
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 pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to any one of claims 10 to 12.
The pressure-sensitive adhesive layer according to claim 13, 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.