JP7052298B2 - Optical Adhesives and Optical Adhesive Sheets - Google Patents

Description

The present invention relates to adhesives that can be used in optical applications.

In recent years, input devices that use a touch panel in combination with an image display device such as a liquid crystal display (LCD) or an organic electorluminescence (EL) display (OLED) have become widespread. The transparent conductive film used for a touch panel is generally configured by laminating a transparent conductive film (ITO film) on a base material such as plastic, and the transparent conductive film is laminated on another member via an adhesive layer. ing.

As the image display device, a flat display using a glass substrate has been the mainstream, but in recent years, a foldable display (Foldable display) and a rollable display (Rollable display) using a flexible substrate such as plastic have been used. Flexible displays are being developed. Such a flexible display has various advantages such as excellent lightness, thinness, flexibility, and designability as compared with a conventional flat display using a glass substrate. Have.

Conventionally, the adhesive layer has been required to have the property of not foaming or peeling in a high temperature environment or a high temperature and high humidity environment, but when used for a flexible display capable of bending the display itself, it is possible to cope with bending. It was necessary.

Therefore, Patent Document 1 describes a monomer unit derived from an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms in the pressure-sensitive adhesive, and a monomer derived from a monomer having a saturated cyclic group. A pressure-sensitive adhesive consisting of a polymer containing a unit in a molecular structure is disclosed.

Japanese Unexamined Patent Publication No. 2017-48328

However, although the conventional pressure-sensitive adhesive has a certain degree of heat resistance, there is a problem that the moisture resistance and the flexibility cannot be satisfied at the same time.

An object of the present invention is to provide an optical pressure-sensitive adhesive and an optical pressure-sensitive adhesive sheet capable of producing an optical pressure-sensitive adhesive sheet having good moisture-heat resistance, heat resistance and flexibility.

The optical pressure-sensitive adhesive of the present invention contains a copolymer (A) containing a hydroxyl group and an isocyanate curing agent (B).
The copolymer (A) containing a hydroxyl group is a monomer (a-1) having a hydroxyl group, a macromonomer (a-2) having a number average molecular weight of 2000 to 10000 (excluding the monomer (a-1)). It is a copolymer of a monomer mixture containing a monomer (a-3) selected from the group consisting of an amide group-containing monomer, an amino group-containing monomer, a nitrile group-containing monomer, a carboxyl group-containing monomer, and an alkylene oxide-containing monomer.
The isocyanate curing agent (B) contains 0.1 to 10 parts by mass with respect to 100 parts by mass of the copolymer (A) containing a hydroxyl group.

According to the above-mentioned invention, it is an object of the present invention to provide an optical pressure-sensitive adhesive and an optical pressure-sensitive adhesive sheet capable of producing an optical pressure-sensitive adhesive sheet having good moisture-heat resistance, heat resistance and flexibility.
Can be provided.

It is sectional drawing which shows typically the liquid crystal display. It is sectional drawing which shows typically the organic EL display.

The terms used herein are defined. The (meth) acrylic acid ester includes an acrylic acid ester and a methacrylic acid ester. The monomer is an ethylenically unsaturated group-containing monomer. The adherend is the other party to which the adhesive sheet is attached. Sheets, films and tapes are synonyms in the present invention.

The optical pressure-sensitive adhesive of the present invention contains a copolymer (A) containing a hydroxyl group and an isocyanate curing agent (B).
The copolymer (A) containing a hydroxyl group is a monomer (a-1) having a hydroxyl group, a macromonomer (a-2) having a number average molecular weight of 2000 to 10000 (excluding the monomer (a-1)). It is a copolymer of a monomer mixture containing a monomer (a-3) selected from the group consisting of an amide group-containing monomer, an amino group-containing monomer, a nitrile group-containing monomer, a carboxyl group-containing monomer, and an alkylene oxide-containing monomer.
The isocyanate curing agent (B) contains 0.1 to 10 parts by mass with respect to 100 parts by mass of the copolymer (A) containing a hydroxyl group.

The optical pressure-sensitive adhesive of the present invention preferably forms a pressure-sensitive adhesive layer by coating and is used as a pressure-sensitive adhesive sheet provided with a base material. The pressure-sensitive adhesive sheet is preferably used as, for example, an optical pressure-sensitive adhesive sheet used for display applications. The optical pressure-sensitive adhesive means that the pressure-sensitive adhesive layer to be formed is transparent and can transmit light, so that the useable adhesive is not limited to display applications.

Since the optical pressure-sensitive adhesive of the present invention uses the macromonomer (a-2) as the constituent unit of the copolymer (A), the pressure-sensitive adhesive layer has a trade-off property of achieving both hardness and softness. , Heat resistance and flexibility are improved.

It is more preferable that the optical pressure-sensitive adhesive forms an pressure-sensitive adhesive layer by coating and is used as an optical pressure-sensitive adhesive sheet provided with an optical film. The optical adhesive sheet can be used for bonding various members. In particular, it is preferable to use it for bonding each member constituting the display.

<Copolymer containing a hydroxyl group (A)>
In the present specification, the copolymer (A) containing a hydroxyl group (hereinafter referred to as "copolymer (A)") is a monomer (a-1) having a hydroxyl group, a macromonomer (a-2), and a monomer (hereinafter referred to as "copolymer (A)"). It is a copolymerization of a monomer mixture containing a-3).

Since the copolymer (A) has a hydroxyl group by copolymerizing the monomer (a-1) containing a hydroxyl group, a polymer network is formed by a cross-linking reaction with the isocyanate curing agent (B). As a result, in addition to improving the adhesion between the adhesive layer and the base material, heat resistance and moisture heat resistance are further improved.

Examples of the hydroxyl group-containing monomer (a-1) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. Examples thereof include 3-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.
Among these, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl acrylate are more preferable in terms of further improving heat resistance and moist heat resistance.

The monomer (a-1) containing a hydroxyl group may be used alone or in combination of two or more.

The hydroxyl group-containing monomer (a-1) preferably contains 0.1 to 5% by mass, more preferably 0.2 to 2% by mass, in 100% by mass of the monomer mixture. When the content is 0.1% by mass or more, sufficient cohesive force can be easily obtained, and when the content is 5% by mass or less, both cohesive force and adhesiveness can be easily achieved at a high level.

The copolymer (A) in the present specification contains a macromonomer (a-2) as a monomer unit constituting the copolymer. By containing the macromonomer (a-2) in the copolymer (A), a trade-off property of achieving both hardness and softness in the adhesive layer can be obtained.

The macromonomer (a-2) is a monomer having a polymer unit and a polymerizable functional group unit (ethylenically unsaturated group) and having a number average molecular weight of 2000 to 10000. When the macromonomer (a-2) is used, the copolymer (A) forms a high-molecular-weight side chain as a hard segment, so that the cohesive force of the copolymer (A) itself is improved and hardness is obtained. Be done. Further, it is presumed that the presence of the high molecular weight side chain suppresses the formation of molecular entanglement or cluster formation between the copolymers (A) (the entanglement is alleviated). As a result, the adhesive layer has a trade-off property of achieving both hardness and softness, so that heat resistance and flexibility are improved. The number average molecular weight of the macromonomer (a-2) is more preferably 4000 to 8000. Further, the macromonomer (a-2) is a monomer other than the monomer (a-1) containing a hydroxyl group.

The polymerizable functional group of the macromonomer (a-2) is preferably at least one selected from the group consisting of, for example, a vinyl group, an allyl group, and a (meth) acryloyl group. The polymer chain portion constituting the macromonomer is preferably a polymer of (meth) acrylic acid alkyl ester.
Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, and 2-ethylhexyl. It can be formed by copolymerization of an alkyl ester (meth) acrylate such as (meth) acrylate and stearyl (meth) acrylate.
Further, an acrylic monomer or a vinyl monomer copolymerizable with the (meth) acrylic acid alkyl ester can also be used.

Examples of commercially available macromonomers (a-2) include macromonomers (product names: AA-6, AA-6S, number average molecular weight) in which the molecular terminal is a methacryloyl group and the polymer chain is polymethylmethacrylate. 6000; macromonomer whose polymer chain is polystyrene (product name: AS-6S, AS-6, number average molecular weight 6000; manufactured by Toa Synthetic Co., Ltd.), polymer chain is a copolymer of styrene / acrylic nitrile. Macromonomer (product name: AN-6S, number average molecular weight 6000; manufactured by Toa Synthetic Co., Ltd.), macromonomer whose polymer chain is polybutyl acrylate (product name: AB-6, number average molecular weight 6000; manufactured by Toa Synthetic Co., Ltd.) , Macromonomer whose polymer chain is polybutyl acrylate (product name: AB-8, number average molecular weight 8000; manufactured by Toa Synthetic Co., Ltd.) and the like.

The macromonomer (a-2) may be used alone or in combination of two or more.

The macromonomer (a-2) preferably contains 0.1 to 5% by mass, more preferably 0.1 to 2% by mass, in 100% by mass of the monomer mixture. When the content is 0.1% by mass or more, both hardness and softness can be achieved at a higher level. Further, when the content is 5% by mass or less, the heat resistance and the flexibility are further improved.

The monomer (a-3) is a monomer selected from the group consisting of an amide group-containing monomer, an amino group-containing monomer, a nitrile group-containing monomer, a carboxyl group-containing monomer, and an alkylene oxide-containing monomer. In other words, the monomer (a-3) is preferably a monomer having an SP value of 9.0 to 15 and having a solubility in water of 50 g / L or more and having no hydroxyl group and having appropriate hydrophilicity. This increases the hydrophilicity of the copolymer (A). When the SP value becomes 9.00 or more, the polarity of the copolymer (A) becomes higher, and when the copolymer (A) is left in a high temperature and high humidity environment, the adhesive layer is less likely to turn white. Further, when the SP value is 15.00 or less, the polarity of the copolymer (A) can be made more appropriate. Further, when the solubility in water is 50 g / L or more, the affinity with water is further improved. The monomer (a-3) is a monomer other than the hydroxyl group-containing monomer (a-1) and the macromonomer (a-2).

When the adhesive sheet is attached to an adherend such as glass and then left in a high temperature and high humidity environment, moisture usually infiltrates into the adhesive layer. Since the pressure-sensitive adhesive layer containing the copolymer (A) contains a monomer (a-3) unit having appropriate hydrophilicity, the affinity between the water content and the copolymer (A) is good, and both are well compatible with each other. Therefore, the transparent adhesive layer can maintain its transparency without changing to white. That is, in the present invention, moisture resistance is obtained by intentionally infiltrating the adhesive layer with moisture.

Examples of the amide group-containing monomer include (meth) acrylamide, N-methylolacrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, N-vinylacetamide, N-vinylpyrrolidone, and acryloylmorpholine. ..
Among these, (meth) acrylamide, diacetone (meth) acrylamide and acryloyl morpholine are preferable, and acrylamide and acryloyl morpholine are more preferable in terms of improving heat resistance and moisture heat resistance and further suppressing floating and peeling.

Examples of the amino group-containing monomer include aminomethyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the like.
Among these, dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate are preferable, and dimethylaminoethyl acrylate and diethylaminoethyl acrylate are more preferable in terms of improving heat resistance and moist heat resistance and further suppressing the floating and peeling. ..

Carboxyl group-containing monomers include (meth) acrylic acid, monohydroxyethyl phthalate acrylate, p-carboxybenzyl acrylate, ethyleneoxy-modified (additional moles: 2-18) phthalic acid acrylate, monohydroxypropyl phthalate acrylate, and succinic acid. Examples thereof include monohydroxyethyl acrylate, β-carboxyethyl acrylate, 2- (4-benzoyl-3-hydroxyphenoxy) ethyl acrylate, maleic acid, monoethylmaleic acid, itaconic acid, citraconic acid, and fumaric acid.
Among these, (meth) acrylic acid and itaconic acid are preferable, and (meth) acrylic acid is more preferable in terms of improving heat resistance and moisture heat resistance, and further suppressing the floating and peeling.

Examples of the alkyleneoxy group-containing monomer include the monomer represented by the following general formula (1) and the monomer represented by the general formula (2). As the alkyleneoxy group, for example, an ethyleneoxy group and a propyleneoxy group are preferable, and an ethyleneoxy group is more preferable.

General formula (1)

General formula (2)

In the general formula (1) and the general formula (2), R ₁ and R ₂ are independent hydrogen atoms or methyl groups, and n and m are integers representing repeating units, and 1 ≦ n ≦ 25 and 1 ≦ m. ≦ 25, preferably 1 ≦ n ≦ 13, 1 ≦ m ≦ 5.

Commercially available products of the monomer represented by the general formula (1) are, for example, methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a hydrogen atom, n = 1), methoxydiethylene glycol acrylate (Osaka Organic). Manufactured by Kagaku Kogyo Co., Ltd .: In the above formula (1), R ₁ is a hydrogen atom, n = 2), methoxytriethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd .: In the above formula (1), R ₁ is a hydrogen atom, n = = 3), methoxypolyethylene glycol # 400 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a hydrogen atom, n = 9), methoxypolyethylene glycol # 600 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: In the above formula (1), R ₁ is a hydrogen atom, n = 13), methoxypolyethylene glycol # 1000 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a hydrogen atom, n = 23). methoxydiethyleneglycol methacrylate (manufactured by Shin Nakamura chemical Co., Ltd. in the above formula (1), R ₁ is a methyl group, n = 2), methoxy triethylene glycol dimethacrylate (manufactured by Shin Nakamura chemical Co., Ltd. in the above formula (1), R ₁ is a methyl group, n = 3), methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a methyl group, n = 4), methoxypolyethylene glycol # 400 methacrylate (New Nakamura) Made by Chemical Industry Co., Ltd .: In the above formula (1), R ₁ is a hydrogen atom, n = 9), methoxypolyethylene glycol # 600 methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a hydrogen atom, n = 13), methoxypolyethylene glycol # 1000 methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (1), R ₁ is a hydrogen atom, n = 23).

Commercially available products of the monomer represented by the general formula (2) include, for example, methoxytripropylene glycol acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .: in the above formula (2), R ₁ is a hydrogen atom, m = 3), methoxytripropylene glycol. Methacrylate (manufactured by Shin Nakamura Chemical Industry Co., Ltd .: in the above formula (2), R ₁ is a methyl group, m = 3)

Among these, methoxyethyl acrylate, methoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol # 400 acrylate, methoxypolyethylene glycol # 600 acrylate, in terms of improving heat resistance and moist heat resistance, and further suppressing the floating and peeling. Methoxytripropylene glycol acrylate is preferable, and methoxyethyl acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol # 400 acrylate, and methoxytripropylene glycol acrylate are more preferable.

Among the monomers (a-3), amide group-containing monomers and alkylene oxide-containing monomers are more preferable in terms of being able to further suppress improvements in heat resistance and moist heat resistance.

The monomer (a-3) preferably contains 10 to 50% by mass, more preferably 10 to 30% by mass, in 100% by mass of the monomer mixture. When the content is 10 to 50% by mass, the moisture resistance and heat resistance are further improved.

The monomer (a-3) may be used alone or in combination of two or more.

<SP value>
The SP value (solubility parameter) of the monomer can be obtained by the following formula 1 based on the Fedors calculation method [“Polymer Engineering and Science”, Vol. 14, No. 2 (1974), pp. 148 to 154].

Formula 1

However, in the formula, δ is the solubility parameter (SP value), and Δei is the molar evaporation energy (
cal / mol) and Δvi are molar volumes (cm ³ / mol). The unit of the solubility parameter is (cal / mol) ^1/2 .

Table 1 shows the eigenvalues of Δei and Δvi given to the main atom or atomic group with respect to the above formula 1.

<Solubility in water>
In the present invention, the solubility of the monomer (a-3) in water can be determined by the following solubility test.
(Solubility test)
A predetermined amount of monomer is added to 1 L of distilled water at 25 ° C., stirred with Homo Disper (manufactured by PRIMIX) for 10 minutes, left for 60 minutes, and then the solubility is evaluated according to the following criteria, and the solubility in distilled water is evaluated. Is calculated.
Dissolution: It is transparent, has no turbidity, and is completely dissolved.
Insoluble: Cloudy and inadequately dissolved.

In addition, the solubility parameter (SP value) of the main monomer (a-3) calculated by the above formula and the solubility are shown in Table 2.

The monomer (a-1) having a hydroxyl group, the macromonomer (a-2), and other monomers other than the monomer (a-3) that can be used for copolymerization have, for example, a (meth) acrylic acid alkyl ester and an epoxy group. Monomers and vinyl monomers are preferable.

The alkyl ester (meth) acrylate is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth). Acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) Examples thereof include acrylate, hexadecyl (meth) acrylate, and octadecyl (meth) acrylate. Of these, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable in terms of further improving the adhesive performance.

Monomers having an epoxy group include, for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 6-methyl-3,4-epoxycyclohexylmethyl (meth) acrylate and the like. Can be mentioned.

Examples of the vinyl monomer include vinyl acetate, vinyl crotonic acid, styrene, acrylonitrile and the like.
Other monomers may be used alone or in combination of two or more.

The other monomer preferably contains 20 to 95% by mass, more preferably 30 to 90% by mass, based on 100% by mass of the monomer mixture. When the content is adjusted to 20 to 95% by mass, the moisture resistance and heat resistance are further improved.

The weight average molecular weight of the copolymer (A) is preferably 500,000 to 1.8 million, more preferably 800,000 to 1.5 million. When it is in the range of 500,000 to 1.8 million, the cohesive force is further improved, and the moisture resistance, heat resistance and flexibility are further improved. The weight average molecular weight and the number average molecular weight are polystyrene-equivalent values measured by a gel permeation chromatography (GPC) method. Details of the measurement method of GPC are described in Examples.

The copolymer (A) can be synthesized by polymerizing a monomer mixture. As the polymerization, known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization are possible, but solution polymerization is preferable. As the solvent used in the solution polymerization, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone and the like are preferable.
The polymerization temperature is preferably a boiling point reaction at 60 to 120 ° C. The polymerization time is preferably about 5 to 12 hours.

The polymerization initiator used for the polymerization is preferably a radical polymerization initiator. The radical polymerization initiator is generally a peroxide or an azo compound.
Peroxides include, for example, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-. Dialkyl peroxides such as di (t-butylperoxy) hexin-3;
Peroxyesters such as t-butylperoxybenzoate, t-butylperoxyacetate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane; cyclohexanone peroxide, 3,3,5-trimethylcyclohexanoneper Ketone peroxides such as oxides and methylcyclohexanone peroxides;
2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-) Butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) barate, and other peroxyketals;
Hydroperoxides such as cumenehydroperoxide, diisopropylbenzenehydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide;
Diacyl peroxides such as benzoyl peroxide, decanoyle peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide;
Examples thereof include peroxydicarbonates such as bis (t-butylcyclohexyl) peroxydicarbonate.

The azo compound is, for example, 2,2'-azobisisobutyronitrile such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN), 2,2'-azobis (2-methylbutyronitrile);
2,2'-Azobisvaleronitrile such as 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile);
2,2'-azobis propionitrile such as 2,2'-azobis (2-hydroxymethylpropionitrile);
Examples thereof include 1,1'-azobis-1-alkanenitrile such as 1,1'-azobis (cyclohexane-1-carbonitrile).

The polymerization initiator may be used alone or in combination of two or more.

The polymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the monomer mixture.

<Isocyanate curing agent (B)>
The isocyanate curing agent (B) reacts with the hydroxyl group of the copolymer (A) to improve the cohesive force of the adhesive layer and further improve the heat resistance.

The isocyanate curing agent (B) is a polyisocyanate having two or more isocyanate groups. The isocyanate curing agent (B) is preferably an isocyanate monomer such as an aromatic polyisocyanate, an aliphatic polyisocyanate, an aromatic aliphatic polyisocyanate, or an alicyclic polyisocyanate, and a burette body, a nurate body, and an adduct body thereof. ..

The aromatic polyisocyanate is, for example, 1,3-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-. Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4', 4 "-Triphenylmethane triisocyanate and the like can be mentioned.

The aliphatic polyisocyanate includes, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylenedisocyanate, 1,3-butylenedisisisus, and the like. Dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like can be mentioned.

The aromatic aliphatic polyisocyanate is, for example, ω, ω'-diisocyanate-1,3-dimethylbenzene, ω, ω'-diisocyanate-1,4-dimethylbenzene, ω, ω'-diisocyanate-1,4-diethylbenzene, Examples thereof include 1,4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

The alicyclic polyisocyanate is, for example, 3-isocyanate methyl-3,5,5-trimethylcyclohexylisocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexanediisocyanate, 1,4. -Cyclohexanediisocyanate, methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,4-bis (isocyanatemethyl) cyclohexane and the like can be mentioned.

The burette body is a self-condensed product having a burette bond in which an isocyanate monomer is self-condensed. Examples of the burette body include a burette body of hexamethylene diisocyanate.

The nurate form is a trimer of an isocyanate monomer. For example, a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, a trimer of tolylene diisocyanate, and the like can be mentioned.

The adduct is a bifunctional or higher functional isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional or higher functional small molecule active hydrogen-containing compound. The adduct can be, for example, a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with trilenidis isocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, or trimethylol. Examples thereof include a compound obtained by reacting propane with isophorone diisocyanate, a compound obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate, and the like.

The isocyanate curing agent (B) is preferably a trifunctional isocyanate compound from the viewpoint of forming a sufficient crosslinked structure. The isocyanate curing agent is more preferably an adduct-form or a nurate-form, which is a reaction product of an isocyanate monomer and a trifunctional small molecule active hydrogen-containing compound. The isocyanate curing agent is a trimethylolpropane adduct body of hexamethylene diisocyanate, a nurate body of hexamethylene diisocyanate, a trimethylol propane adduct body of tolylene diisocyanate, a nurate body of tolylene diisocyanate, a trimethylol propane adduct body of isophorone diisocyanate, and isophorone diisocyanate. Nurate and trimethylolpropane adducts of xylylene diisocyanate are preferable, and trimethylolpropane adducts of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, and trimethylolpropane adducts of xylylene diisocyanate are more preferable.

The isocyanate curing agent (B) is preferably used in an amount of 0.1 part by mass to 10 parts by mass, more preferably 0.5 part by mass to 5 parts by mass, based on 100 parts by mass of the copolymer (A). When the content is 0.1 to 10 parts by mass, the cohesive force of the adhesive layer is improved and the heat resistance is further improved.

The optical pressure-sensitive adhesive of the present invention can be used in combination with other curing agents other than the isocyanate curing agent (B). As the other curing agent, an epoxy compound, an aziridine compound, a carbodiimide compound, an acid anhydride group-containing compound, a metal chelate and the like are preferable.

Examples of the epoxy compound 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, and the like. Trimethylol Propane triglycidyl ether, diglycidyl aniline, N, N, N', N'-tetraglycidyl-m-xylylene diamine, 1,3-bis (N, N'-diglycidyl aminomethyl) cyclohexane, N, Examples thereof include N, N', N'-tetraglycidylaminophenylmethane and the like.

Examples of the aziridine compound include N, N'-diphenylmethane-4,4'-bis (1-aziridinecarbokisite), N, N'-toluene-2,4-bis (1-aziridinecarbokisite), and bisisophthaloyl. -1- (2-Methylaziridine), tri-1-aziridinylphosphine oxide, N, N'-hexamethylene-1,6-bis (1-aziridinecarbokisite), 2,2'-bishydroxymethylbutanol -Tris [3- (1-aziridinyl) propionate], trimethyl propantri-β-aziridinyl propionate, tetramethylol methanetri-β-aziridinyl propionate, tris-2,4,6-( 1-aziridinyl) -1,3,5-triazine, 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane and the like can be mentioned.

The carbodiimide compound is preferably a high molecular weight polycarbodiimide produced by decarboxylating and condensing the diisocyanate compound in the presence of a carbodiimideization catalyst. The commercially available high molecular weight polycarbodiimide is preferably the carbodilite series manufactured by Nisshinbo. Among them, Carbodilite V-01, 03, 05, 07, 09 is preferable because it has excellent compatibility with an organic solvent.

The acid anhydride group-containing compound is a compound having two or more carboxylic acid anhydride groups. Examples of the acid anhydride group-containing compound include tetracarboxylic acid dianhydride, hexacarboxylic acid trianhydride, hexacarboxylic acid dianhydride, and maleic anhydride copolymer resin. The "acid anhydride group-containing compound" includes polycarboxylic acids, polycarboxylic acid esters, polycarboxylic acid half esters and the like that can become anhydrides during the reaction via a dehydration reaction.

Tetracarboxylic acid dianhydride is, for example, pyromellitic anhydride, benzophenone tetracarboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, diphenylsulfonetetracarboxylic acid dianhydride, diphenylsulfide tetracarboxylic acid. Examples thereof include dianhydride, butanetetracarboxylic acid dianhydride, perylenetetracarboxylic acid dianhydride, naphthalenetetracarboxylic acid dianhydride and the like.

The metal chelate is preferably a coordination compound of a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium with acetylacetone or ethyl acetoacetate. Examples of the metal chelate include aluminum ethyl acetoacetate / diisopropyrate, aluminum trisacetylacetonate, aluminum bisethylacetate / monoacetylacetone, and aluminum alkylacetate / diisopropyrate.

Other curing agents may be used alone or in combination of two or more.

As the other curing agent, it is preferable to use 0.05 part by mass to 20 parts by mass, and more preferably 0.1 part by mass to 15 parts by mass with respect to 100 parts by mass of the copolymer (A). When the content is 0.05 to 20 parts by mass, the cohesive force is improved and the heat resistance is further improved.

The optical pressure-sensitive adhesive of the present invention may contain a plasticizer as long as the problem can be solved.

As the plasticizer, for example, an ester-based plasticizer and a liquid rubber-based plasticizer are preferable.
Ester-based plasticizers include aliphatic dibasic acid diester-based plasticizers, phthalic acid diester-based plasticizers, trimellitic acid trimester-based plasticizers, pyromellitic acid tetraester-based plasticizers, adipic acid diester-based plasticizers, and alkylene oxides. Examples thereof include group-containing aliphatic dibasic acid diester plasticizers.

Among these, ester-based plasticizers are preferable in terms of wettability and stain resistance, and trimellitic acid ester-based plasticizers, pyromellitic acid ester-based plasticizers, and alkylene oxide group-containing aliphatic dibasic acid esters are more preferable.

The plasticizer may be used alone or in combination of two or more.

The plasticizer is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, based on 100 parts by mass of the copolymer (A). When the content is 10 parts by mass or more, the flexibility is further improved. When the content is 80 parts by mass or less, the cohesive force and stain resistance are further improved.

The optical pressure-sensitive adhesive of the present invention may further contain an organic silane compound.

Examples of the organic silane compound include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropyltripropoxysilane, and 3- (meth) acryloxy. An alkoxysilane compound having a (meth) acryloxy group, such as propyltributoxysilane, 3- (meth) acryloxipropylmethyldimethoxysilane, 3- (meth) acryloxylpropylmethyldiethoxysilane;
Alkoxysilane compounds having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane;
3-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl)- 3-Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) An alkoxysilane compound having an amino group such as -3-aminopropylmethyldiethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane;
Alkoxysilane compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane;
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltributoxysilane, 3-glycidoxypropylmethyldimethoxysilane, An alkoxysilane compound having an epoxy group such as 3-glycidoxypropylmethyldiethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane;
Tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane;
3-Chloropropyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, styryltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 3-Triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate, 3-isocyanuspropyltrimethoxysilane, 3-isocyanampropyl Examples thereof include triethoxysilane, hexamethyldisilazane, and silicone resins having an alkoxysilyl group in the molecule.

The amount of the organic silane compound is preferably 0.01 to 2 parts by mass, more preferably 0.05 to 1 part by mass with respect to 100 parts by mass of the copolymer (A).

The pressure-sensitive adhesive of the present invention includes various resins, oils, softeners, dyes, pigments, antioxidants, ultraviolet absorbers, weather-resistant stabilizers, plasticizers, fillers, etc. as optional components as long as the problems can be solved. It can contain an anti-aging agent, an anti-static agent and the like.

The pressure-sensitive adhesive of the present invention is suitable as an optical pressure-sensitive adhesive sheet, as a raw material for various plastic sheets, general labels / seals, adhesive-imparting agents, pressure-sensitive adhesives for laminated structures, sealing agents, and various resin additives. It can be used very usefully as a raw material.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention includes a base material and a pressure-sensitive adhesive layer which is a cured product of an optical pressure-sensitive adhesive. The pressure-sensitive adhesive sheet is produced, for example, by applying an optical pressure-sensitive adhesive to a base material and drying it to form a pressure-sensitive adhesive layer. Further, an optical pressure-sensitive adhesive is applied to the peelable sheet and dried to form an pressure-sensitive adhesive layer, and the base materials are bonded to each other. Further, on the surface of the adhesive layer that is not in contact with the base material, a peelable sheet is usually attached until immediately before use in order to prevent foreign matter from adhering. The drying temperature is usually about 60 to 150 ° C. The thickness of the adhesive layer is usually about 0.1 to 200 μm.

Examples of the coating method include a roll coater method, a comma coater method, a die coater method, a reverse coater method, a silk screen method, and a gravure coater method.

When applying the optical adhesive, the viscosity can be adjusted with a solvent. The solvent is, for example, a hydrocarbon solvent such as toluene, xylene, hexane, heptane; an ester solvent such as ethyl acetate or butyl acetate; a ketone solvent such as acetone or methyl ethyl ketone; a halogenated hydrocarbon solvent such as dichloromethane or chloroform. ; Examples include ether solvents such as diethyl ether, methoxytoluene, and dioxane.

The thickness of the adhesive layer is usually about 20 to 200 μm.

As the base material, flexible sheets and plate materials can be used without limitation. Examples of the base material include plastic, paper, and metal foil, and laminates thereof and the like.
In order to improve the adhesion to the surface of the base material in contact with the adhesive layer, easy adhesion treatment such as dry treatment such as corona discharge treatment or wet treatment such as coating of an anchor coating agent can be performed in advance.
As the base material, a laminated body obtained by laminating a single optical film or a plurality of optical films can be used.

The thickness of the base material is usually about 10 to 250 μm.

As the release sheet, a known release sheet in which the surface of plastic or paper is subjected to a known release treatment such as a silicone-based release agent can be used.

The thickness of the peelable sheet is usually about 10 to 250 μm.

<Optical adhesive sheet>
The optical pressure-sensitive adhesive sheet of the present invention preferably includes a pressure-sensitive adhesive layer which is a cured product of an optical pressure-sensitive adhesive. Further, on both sides of the adhesive layer, a peelable sheet is usually attached until just before use to prevent foreign matter from adhering. It is also preferable to attach the base material to one side or both sides of the adhesive layer. The base material is preferably an optical film.

The optical film is a transparent and light-transmitting film, for example, polyvinyl alcohol, triacetyl cellulose, polyolefin (polyester, polyethylene), polycycloolefin, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene. Examples thereof include polyesters such as naphthalate, polyacrylics such as polymethylmethacrylate and polybutylmethacrylate, polycarbonate, polynorbornene, polyarylate, polyphenylene sulfide, polystyrene, polyamide-based, polyimide and epoxy-based resins.

Among these optical films, a low-polarity optical film is preferable. Examples of the low-polarity optical film include polycycloolefin resin (water contact angle 90 °), polycarbonate resin (water contact angle 80 °), polynorbornene resin (water contact angle 89 °), and polymethylmethacrylate resin (water contact angle 80 °). °). The low-polarity optical film is an optical film having a contact angle with water (water contact angle) of 70 ° or more. The water contact angle is measured by the droplet method using an automatic contact angle meter (model CA-V type) manufactured by Kyowa Surface Science Co., Ltd. after leaving various optical films at 23 ° C and 50% RH for 24 hours. In an atmosphere of 23 ° C. and 50% RH, 2.0 μL of distilled water was dropped onto the film, and the angle consisting of the tangent line between the film and the edge of the droplet was measured 1 second after the droplet was dropped. do.

Further, as the optical film, it is also preferable to use an optical member having an optical function formed by forming a functional layer on the film, imparting functionality to the film itself, or forming a laminated film. Examples of the optical member include a polarizing plate, a retardation film, an elliptical polarizing film, an antireflection film, a brightness improving film, and glass.

Applications of the optical adhesive sheet of the present invention include, for example, various electronics-related members such as LCDs, OLEDs, plasma displays, touch screen panels, and electrode peripheral members.
<Display>
The display of the present invention preferably includes an optical member and an adhesive layer which is a cured product of an optical adhesive.
First, an LCD will be described as an example of a display with reference to FIG. The lower side of FIG. 2 is the lower side, and the upper side is the upper side. Needless to say, the configuration of the LCD is not limited to FIG. The surface of the liquid crystal cell 105 is protected by adhering glass 103 on both sides thereof. The liquid crystal cell 105 may be, for example, a TFT substrate. Plastic can be used instead of glass 103. The plastic is preferably the optical film described above. The thickness of the glass 103 is about 0.2 to 1.5 mm. The polarizing plate 101 is attached to each of the glass 103 via the adhesive layer 102. The thickness of the adhesive layer 102 is about 15 to 30 μm. The polarizing plate 101 is generally configured to have a protective film bonded to both sides of a polarizing element via an adhesive. Examples of the polarizing element include a polyvinyl alcohol film. Further, as the protective film, for example, a triacetyl cellulose film is preferable.

Next, OLED will be described as another example of the display with reference to FIG. The lower side of FIG. 2 is the lower side, and the upper side is the upper side. Needless to say, the configuration of the OLED is not limited to FIG. The organic EL cell 210 has a structure in which a support 209, an organic EL layer 208, and a protective layer 207 are sequentially laminated. The support 209 is, for example, a polyimide film. As the organic EL layer 208, a known organic EL layer can be used. The barrier layer 207 can be appropriately selected from silicon nitride, glass, plastic and the like. As the glass, for example, glass whose surface is coated with fluorine is preferable. As the plastic, for example, polyethylene naphthalate and transparent polyimide are preferable. A retardation film 206 is laminated on the barrier layer 207 via the adhesive layer 202. The polarizing plate 201 is laminated on the retardation film 206 via the adhesive layer 202.

Next, examples will be given and further described in detail, but the present invention is not limited thereto. In the example, unless otherwise specified, "parts" indicates "parts by mass" and "%" indicates "% by mass". The blending amount in the table is a part by mass.

<Synthesis Example 1: Copolymer (A)>
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube (hereinafter, simply referred to as “reaction vessel”), 0.1 part of 2-hydroxyethyl acrylate (HEA), 30.0 parts of acrylamide (AAm), 2.5 parts of macromonomer AB-6 (manufactured by Toa Synthetic Co., Ltd., one-terminal methacryloyl-based butyl acrylate), 67.3 parts of butyl acrylate, 100 parts of ethyl acetate, 2,2' -0.2 parts of azobisisobutyronitrile (hereinafter referred to as AIBN) was charged, and the atmosphere in the reaction vessel was replaced with nitrogen gas. Then, the reaction was started by heating to 65 ° C. while stirring in a nitrogen atmosphere. Then, the reaction solution was reacted at 65 ° C. for 4 hours. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain a copolymer (A-1) solution having a non-volatile content of 30% and a viscosity of 3000 mPa · s. The weight average molecular weight of the obtained copolymer (A-1) was 1.5 million.

<Synthesis Examples 2 to 21>
The copolymer (A) was synthesized by the same method as in Synthesis Example 1 except that the raw materials and the amounts used were changed according to the mass ratio in Table 3. The weight average molecular weight (Mw) of the obtained copolymer (A) is shown in Table 3. The blanks in the table indicate that they are not mixed.

<Measurement of weight average molecular weight (Mw)>
The weight average molecular weight (Mw) was measured by using a GPC "LC-GPC system" manufactured by Shimadzu Corporation. The weight average molecular weight (Mw) was determined by using polystyrene having a known molecular weight as a standard material.
Device name: LC-GPC system "Prominence" manufactured by Shimadzu Corporation
Column: 4 GMHXL manufactured by Tosoh Co., Ltd. and 1 HXL-H manufactured by Tosoh Co., Ltd. were connected.
Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 ml / min Column temperature: 40 ° C

(Example 1)
<Preparation of adhesive>
With respect to 100 parts of the copolymer (A-1) in the obtained copolymer (A-1) solution, 2.5 parts of the adduct compound of trimethylolpropane of tolylene diisocyanate as the isocyanate curing agent (B), As an organic silane compound, 0.1 part of 3-glycidoxypropyltrimethoxysilane and ethyl acetate were added so that the non-volatile content was 20%, and the mixture was stirred to obtain a pressure-sensitive adhesive.

<Creation of optical adhesive sheet>
The obtained optical adhesive is applied onto a peelable sheet (polyethylene terephthalate (PET), "E7004", silicone-based peeling layer, manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm so that the thickness after drying is 50 μm. The adhesive layer was formed by working and drying at 110 ° C. for 3 minutes. Next, one side of a peelable sheet (polyethylene terephthalate, "SP-PET3811", silicone-based peeling layer, manufactured by Lintec Corporation) having a thickness of 38 μm is bonded to this adhesive layer to form a “peeling sheet / adhesive layer / peelable sheet”. The laminated body of was produced. Then, the obtained laminate was aged for one week under the condition of a temperature of 25 ° C. and a relative humidity of 55% to obtain an optical adhesive sheet.

<Examples 2 to 30, Comparative Examples 1 to 6>
As shown in Table 4, an optical pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the type of copolymer, the curing agent, the type of silane coupling agent, and the blending amount were changed.
However, Examples 1 and 3 are reference examples.

Using the obtained optical adhesive sheet, the following physical properties were evaluated for transparency, heat resistance, moisture heat resistance, re-peelability, corrosion resistance, moisture heat whitening resistance, and flexibility.

<Creating an adhesive sheet for testing>
Peel off one of the peelable adhesive sheets of the obtained optical adhesive sheet, and use a laminator on a PET film (manufactured by Toyobo Co., Ltd., A-4300) having a thickness of 100 μm in an exposed adhesive layer at 25 ° C. and a relative humidity of 50% RH. A laminated body composed of a PET film / an adhesive layer / a peelable sheet was prepared.

<Transparency>
A test pressure-sensitive adhesive sheet 1 composed of a PET film / adhesive layer / peelable sheet was produced by cutting out the laminate to a size of 112 mm in width × 200 mm in length (corresponding to a 9-inch type display).
The peelable sheet was peeled off from the test adhesive sheet 1, and the exposed adhesive layer was attached to a non-alkali glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator. HAZE was measured. HAZE was measured using a Turbidimeter NDH5000W manufactured by Nippon Denshoku Kogyo Co., Ltd. The evaluation criteria are as follows.
◯: HAZE is less than 1.0 (good).
X: HAZE is 1.0 or more (defective).

<Heat resistance / moisture heat resistance (non-alkali glass)>
A test pressure-sensitive adhesive sheet 2 composed of a PET film / adhesive layer / peelable sheet was produced by cutting out the laminate to a size of 112 mm in width × 200 mm in length (corresponding to a 9-inch type display).
The peelable sheet was peeled off from the test adhesive sheet 2, and the exposed adhesive layer was attached to a non-alkali glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator. A test laminate consisting of a PET film / adhesive layer / glass was obtained. Then, as a heat resistance test, it was left to stand for 500 hours under the condition of 105 ° C., cooled in an atmosphere of 25 ° C. and a relative humidity of 50% RH, and then the generation of air bubbles and the floating and peeling of the adhesive sheet were visually evaluated under the following conditions. .. As an evaluation of moisture and heat resistance, the test laminate was left in an atmosphere of 60 ° C. and a relative humidity of 95% RH for 500 hours, cooled in an atmosphere of 25 ° C. and a relative humidity of 50% RH, and then bubbles were generated and an adhesive sheet was used. Floating and peeling were visually evaluated under the following conditions. The heat resistance and moist heat resistance were evaluated based on the following three-stage evaluation criteria.
◎: "No bubbles are generated, no floating or peeling is observed, and there is no problem in practical use."
○: "There are slight bubbles, floating and peeling, but there is no problem in practical use."
×: "Practical use is not possible due to the remarkable generation of bubbles, floating and peeling."

<Heat resistance / moisture heat resistance (ITO film)>
The heat resistance test and the moisture heat resistance test were carried out in the same manner as above, except that the adherend of the separately prepared test adhesive sheet 2 was changed from a non-alkali glass plate to an ITO film (made by TDK, Fleclear, thickness 120 μm). .. The evaluation criteria are the same as above.

<Removability (reworkability)>
A test pressure-sensitive adhesive sheet 3 composed of a PET film / pressure-sensitive adhesive layer / peelable sheet was produced by cutting out the laminate to a size of 25 mm in width × 100 mm in length.
The peelable sheet was peeled off from the test adhesive sheet 3, and the exposed adhesive layer was attached to a non-alkali glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator. A test laminate consisting of a PET film / adhesive layer / glass was obtained.
Next, the test laminate was left at 23 ° C. and a relative humidity of 50% for 1 week, and then peeled off at a speed of 300 mm / min in the 180 ° direction to carry out a 180 ° peel test. The fogging of the glass surface after peeling was visually observed, and the re-peeling property was evaluated in three stages.
○: "There is no fogging on the glass surface, there is no problem in practical use"
X: "Cloudy on the glass surface or transfer of the adhesive layer was observed, not practical"

<Corrosion resistance>
A test pressure-sensitive adhesive sheet 4 composed of a PET film / pressure-sensitive adhesive layer / peelable sheet was produced by cutting out the laminate to a size of 25 mm in width × 100 mm in length.
The peelable sheet is peeled off from the test adhesive sheet 4, and the exposed adhesive layer is attached to an ITO film (manufactured by TDK, Freclear, thickness 120 μm) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator, and PET. A test laminate consisting of a film / adhesive layer / ITO film was obtained.
Next, the test laminate was left at 85 ° C. and a relative humidity of 85% RH for 500 hours, the rate of change (%) in the resistance value from immediately after application was measured, and the corrosion resistance was evaluated by the rate of change. The resistance value was measured using a Rollester GP (model number MCP-T600) manufactured by Mitsubishi Chemical Corporation. The evaluation criteria are as follows.
◯: The rate of change of resistance value is less than 150%. Good.
X: The rate of change of resistance value is 150% or more. Not practical.

<Transparency after aging>
The peelable sheet is peeled off from the separately prepared test adhesive sheet 4, and the exposed adhesive layer is attached to a non-alkali glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator. Then, a test laminate composed of a PET film / adhesive layer / glass was obtained.
Next, the test laminate was left to stand in an atmosphere of 85 ° C. and a relative humidity of 85% RH for 1000 hours, cooled in an atmosphere of 25 ° C. and a relative humidity of 50% RH, and then HAZE was measured. HAZE was measured using a Turbidimeter NDH5000W manufactured by Nippon Denshoku Kogyo Co., Ltd. The evaluation criteria are as follows.
⊚: HAZE is less than 1.2 (good).
◯: HAZE is 1.2 or more and less than 8.0 (no problem in practical use).
X: HAZE is 8.0 or more (not practical).

<Flexibility>
A test pressure-sensitive adhesive sheet 5 composed of a PET film / adhesive layer / peelable sheet was produced by cutting out the laminate to a size of 112 mm in width × 200 mm in length (corresponding to a 9-inch type display).
The peelable sheet is peeled off from the above laminate, and the exposed adhesive layer is attached to an ITO film (made by TDK, Freclear, thickness 120 μm) at 25 ° C. and a relative humidity of 50% RH atmosphere using a laminator, and PET film / adhesive. A test laminate consisting of a layer / ITO film was obtained.
Next, the conditions were set so that the inner diameter (diameter) of the test laminate when bent in a bending tester (manufactured by Yuasa System Equipment Co., Ltd.) at 25 ° C and 50% relative humidity RH atmosphere was set to 6 mm, and then bent and 180. 100,000 cycles were repeated with ° opening as one cycle. The flexibility was evaluated from the following viewpoints on the transparency and appearance of the test laminate.

Transparency: HAZE of the test laminate was measured using a Turbidimeter NDH5000W manufactured by Nippon Denshoku Kogyo Co., Ltd. The evaluation criteria are as follows.
◯: HAZE is less than 1.0 (good).
X: HAZE is 1.0 or more (not practical).

Appearance: The presence or absence of air bubbles in the test laminate and the presence or absence of floating or peeling of the adhesive layer were visually evaluated under the following conditions.
◎: "No bubbles are generated, no floating or peeling is observed, and there is no problem in practical use."
○: "There are slight bubbles, floating and peeling, but there is no problem in practical use."
×: "There is a practical problem because bubbles are noticeably generated, floating and peeling are observed."

The transparency and appearance of the flexibility were evaluated in the same manner as above except that the atmosphere at the time of bending was changed to an atmosphere of 85 ° C. and a relative humidity of 60 ° C. and an RH atmosphere.

From the results in Table 5, the optical pressure-sensitive adhesives of Examples 1 to 30 are excellent in transparency, heat resistance, moisture heat resistance, removability, corrosion resistance, moisture heat whitening resistance, and flexibility. On the other hand, it was not possible to satisfy all of the above-mentioned characteristics in Comparative Examples 1 to 6.

101 Polarizing plate 102 Adhesive layer 103 Glass 104 Liquid crystal layer 105 Liquid crystal cell 201 Polarizing plate 202 Adhesive layer 206 Phase difference film 207 Barrier layer 208 Organic EL layer 209 Support 210 Organic EL cell

Claims (5)

It contains a copolymer (A) containing a hydroxyl group and an isocyanate curing agent (B).
The copolymer (A) containing a hydroxyl group is a monomer (a-1) having a hydroxyl group, a macromonomer (a-2) having a number average molecular weight of 2000 to 10000 (excluding the monomer (a-1)). It is a copolymer of a monomer mixture containing a monomer (a-3) selected from the group consisting of an amide group-containing monomer, an amino group-containing monomer, a nitrile group-containing monomer, a carboxyl group-containing monomer, and an alkylene oxide-containing monomer.
The monomer (a-1) having a hydroxyl group is contained in an amount of 0.2 to 2% by mass and the monomer (a-3) is contained in an amount of 10 to 50% by mass in 100% by mass of the monomer mixture.
An optical pressure-sensitive adhesive containing 0.1 to 10 parts by mass of the isocyanate curing agent (B) with respect to 100 parts by mass of the copolymer (A) containing a hydroxyl group. The optical pressure-sensitive adhesive according to claim 1, wherein the macromonomer (a-2) is contained in an amount of 0.1 to 5% by mass in 100% by mass of the monomer mixture. An optical pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer which is a cured product of the optical pressure-sensitive adhesive according to claim 1 or 2 . An optical pressure-sensitive adhesive sheet comprising an optical film and a pressure-sensitive adhesive layer which is a cured product of the optical pressure-sensitive adhesive according to claim 1 or 2 . A display provided with an optical member and an adhesive layer which is a cured product of the optical adhesive according to claim 1 or 2 .

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