KR101938894B1 - Pressure-sensitive adhesive composition for optical members and pressure-sensitive adhesive tape for optical members - Google Patents

Abstract

일반식 (1-1) 중, R¹ 은 수소 원자 또는 메틸기를 나타내고, R² 는 수소 원자 또는 탄소수 3 미만의 알킬기를 나타내고, n 은 8∼45 의 정수를 나타낸다.
[화학식 2]

일반식 (1-2) 중, R³ 은 수소 원자 또는 메틸기를 나타내고, R⁴ 는 탄소수 3∼30 의 알킬기를 나타내고, m 은 8∼45 의 정수를 나타낸다.An object of the present invention is to provide a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability. Another object of the present invention is to provide a pressure-sensitive adhesive tape for optical members produced by using the pressure-sensitive adhesive composition for optical members.
The present invention relates to a pressure-sensitive adhesive composition for optical members containing an acrylic copolymer, wherein the acrylic copolymer comprises 1 to 25% by weight of 2-hydroxyethyl acrylate, 1 to 25% by weight of N-vinylpyrrolidone, 0.5 to 30% by weight of a monomer having a structure represented by the following general formula (1-1) or 0.1 to 30% by weight of a monomer having a structure represented by the following general formula (1-2) .
[Chemical Formula 1]

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group having less than 3 carbon atoms, and n represents an integer of 8 to 45.
(2)

In the general formula (1-2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and m represents an integer of 8 to 45.

Description

TECHNICAL FIELD [0001] The present invention relates to a pressure-sensitive adhesive composition for optical members and a pressure-sensitive adhesive tape for optical members. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability. The present invention also relates to a pressure-sensitive adhesive tape for optical members produced using the pressure-sensitive adhesive composition for optical members.

2. Description of the Related Art Display panels are used in various fields, and particularly in mobile phones, portable information terminals, and the like, they are used not only in image display devices but also in input devices. In such an image display apparatus or an input apparatus, the display panel is stuck to a protective plate, a touch panel, an optical filter, or the like for protecting the surface thereof with an adhesive agent or adhesive tape having high transparency such as an acrylic adhesive agent .

However, in the past, when the acrylic pressure-sensitive adhesive is exposed to high temperature and high humidity and then returned to room temperature, the moisture absorbed by the acrylic pressure-sensitive adhesive becomes white due to condensation, resulting in lowering of visibility. Such a decrease in visibility due to whitening may be a fatal defect in an image display apparatus or an input apparatus.

As to this problem, for example, Patent Document 1 discloses an acrylic transparent pressure-sensitive adhesive composition comprising an ABA-type triblock copolymer composed of an acrylate ester and a methacrylate ester and a resin having a hydroxyl group polymer blended. Patent Document 1 discloses that the acrylic transparent pressure-sensitive adhesive composition described in this document can maintain transparency without being whitened even when exposed for a long time under an environment such as a high temperature and high humidity environment, a hot water immersion environment, and a boiling environment.

However, the acrylic transparent pressure-sensitive adhesive composition described in Patent Document 1 is not sufficient in terms of adhesive property and heat resistance, which are originally required for a pressure-sensitive adhesive or pressure-sensitive adhesive tape, because the resin having a hydroxyl group to be blended has a low molecular weight. Accordingly, there is a demand for a new pressure-sensitive adhesive or pressure-sensitive adhesive tape capable of suppressing whitening that occurs under high temperature and high humidity without deteriorating the reliability of the pressure-sensitive adhesive or pressure-sensitive adhesive tape.

Japanese Laid-Open Patent Publication No. 2009-102467

An object of the present invention is to provide a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability. Another object of the present invention is to provide a pressure-sensitive adhesive tape for optical members produced by using the pressure-sensitive adhesive composition for optical members.

The present invention relates to a pressure-sensitive adhesive composition for optical members containing an acrylic copolymer, wherein the acrylic copolymer comprises 1 to 25% by weight of 2-hydroxyethyl acrylate, 1 to 25% by weight of N-vinylpyrrolidone, 0.5 to 30% by weight of a monomer having a structure represented by the following general formula (1-1) or 0.1 to 30% by weight of a monomer having a structure represented by the following general formula (1-2) .

[Chemical Formula 1]

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group having less than 3 carbon atoms, and n represents an integer of 8 to 45.

(2)

In the general formula (1-2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and m represents an integer of 8 to 45.

Hereinafter, the present invention will be described in detail.

The present inventors have found that, in a pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer, by using a high hydrophilic monomer for a monomer constituting an acrylic copolymer, water is finely dispersed when exposed to high temperature and high humidity and then returned to room temperature, As a result, it was found that whitening can be suppressed.

The present inventors have found that a large number of highly hydrophilic monomers increase the glass transition temperature (Tg) of an acrylic copolymer more than necessary and are unsuitable for a pressure-sensitive adhesive composition, while 2-hydroxyethyl acrylate, N-vinylpyrrolidone , Or a specific monomer having a polyethylene oxide chain at a predetermined ratio, it is possible to obtain a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability, .

The pressure-sensitive adhesive composition for an optical member of the present invention contains an acrylic copolymer.

Wherein the acrylic copolymer comprises 1 to 25% by weight of 2-hydroxyethyl acrylate, 1 to 25% by weight of N-vinylpyrrolidone, 0.5 to 30% by weight of a monomer having a structure represented by the following general formula (1-1) , Or 0.1 to 30% by weight of a monomer having a structure represented by the following general formula (1-2).

(3)

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group having less than 3 carbon atoms, and n represents an integer of 8 to 45.

[Chemical Formula 4]

In the general formula (1-2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and m represents an integer of 8 to 45.

2-hydroxyethyl acrylate, N-vinylpyrrolidone, the monomer having the structure represented by the general formula (1-1), and the monomer having the structure represented by the general formula (1-2) High hydrophilicity. Therefore, when the mixed monomer contains these monomers in the above range, the pressure sensitive adhesive composition for an optical member according to the present invention finely disperses water when exposed to high temperature and high humidity and then returned to room temperature, Can be suppressed.

In the present specification, 2-hydroxyethyl acrylate, N-vinylpyrrolidone, a monomer having a structure represented by the general formula (1-1), and a monomer having a structure represented by the general formula (1-2) It is also referred to as " a monomer having a hydrophilic group ".

In addition, the monomer having a hydrophilic group does not increase the glass transition temperature (Tg) of the acrylic copolymer more than necessary, and does not adversely affect the reliability of the pressure-sensitive adhesive composition for optical members of the present invention.

In general, whitening of the acrylic pressure sensitive adhesive becomes remarkable when a thin metal film containing a metal such as ITO or a metal oxide is used as an adherend. However, since the mixed monomer contains a monomer having the hydrophilic group in the above- The pressure-sensitive adhesive composition for an optical member of the present invention can suppress whitening occurring under high temperature and high humidity even when a thin metal film containing a metal such as ITO or a metal oxide is used as an adherend.

In addition to the above-mentioned monomers having a hydrophilic group, for example, 4-hydroxybutyl acrylate (4-HBA), 3-hydroxypropyl Acrylate (3-HPA), and 6-hydroxyhexyl acrylate (6-HHA). The mixed monomer may contain these highly hydrophilic monomers.

Among the above-mentioned monomers having a hydrophilic group, a pressure-sensitive adhesive composition for an optical member capable of maintaining high adhesiveness and maintaining high adhesiveness even after a lapse of time can be obtained, and a thin metal film containing a metal such as ITO or a metal oxide can be deposited The monomers having the structure represented by the general formula (1-1) or the monomers having the structure represented by the general formula (1-2) are preferred because they can more effectively inhibit whitening occurring under high temperature and high humidity Do.

When the pressure-sensitive adhesive composition for an optical member of the present invention contains a crosslinking agent to be described later, when the monomer having a hydrophilic group is 2-hydroxyethyl acrylate or N-vinylpyrrolidone, depending on the kind or amount of the crosslinking agent The gelation of the pressure-sensitive adhesive composition for an optical member sharply progresses, and handling properties may be lowered. Therefore, it is necessary to sufficiently control the kind and amount of the cross-linking agent. On the other hand, when the monomer having a hydrophilic group is a monomer having a structure represented by the general formula (1-1) or a monomer having a structure represented by the general formula (1-2), the kind or amount of the crosslinking agent Accordingly, the gelation of the pressure-sensitive adhesive composition for an optical member can be inhibited from progressing rapidly, and the kind and amount of the crosslinking agent can be easily controlled.

In the monomer having the structure represented by the general formula (1-1) and the monomer having the structure represented by the general formula (1-2), the repeating number of the ethylene oxide has a lower limit of 8 and an upper limit of 45. If the number of repetitions of the ethylene oxide is less than 8, the obtained pressure-sensitive adhesive composition for an optical member can not sufficiently suppress whitening occurring under high temperature and high humidity. When the number of repetitions of the ethylene oxide exceeds 45, the obtained pressure-sensitive adhesive composition for an optical member can not sufficiently suppress whitening occurring under high temperature and high humidity. When the number of repetitions of the ethylene oxide exceeds 45, a monomer having a structure represented by the general formula (1-1) or a monomer having a structure represented by the general formula (1-2) The compatibility of the pressure-sensitive adhesive composition for an optical member is deteriorated.

The number of repetitions of the ethylene oxide can more effectively inhibit whitening occurring under high temperature and high humidity, so that the lower limit is preferably 13 and the upper limit is preferably 40. [ It is particularly preferable that the number of repeating ethylene oxide is 30. The repeating number of the ethylene oxide is represented by n in the general formula (1-1) and m in the general formula (1-2).

In the monomer having the structure represented by the general formula (1-1), the terminal group of the polyethylene oxide chain is a hydrogen atom or an alkyl group having less than 3 carbon atoms. Among them, an alkyl group having less than 3 carbon atoms is preferable because a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening under the condition of higher temperature and high humidity is obtained.

The terminal group of the polyethylene oxide chain is represented by R ² in the general formula (1-1).

In the monomer having the structure represented by the general formula (1-2), the terminal group of the polyethylene oxide chain is an alkyl group having 3 to 30 carbon atoms. The terminal group of the polyethylene oxide chain is preferably an alkyl group having 18 carbon atoms since a pressure-sensitive adhesive composition for an optical member capable of inhibiting whitening under the condition of higher temperature and high humidity is obtained. The terminal group of the polyethylene oxide chain is represented by R ⁴ in the general formula (1-2).

Among the monomers having the structure represented by the general formula (1-1) or the monomers having the structure represented by the general formula (1-2), for example, Brenma PME-1000 (repeating number of ethylene oxide = BENMA PME-2000 (ethylene oxide repeat number = 45, terminal methyl group, Nichi), Brenma PME-400 (repeating number of ethylene oxide = 9, terminal methyl group, NK ester AM-130G (repeating number of ethylene oxide = 13, terminal methyl group, Shin Nakamura Chemical Industry Co., Ltd.), Wight ester 041MA (repeating number of ethylene oxide = 30, terminal methyl group, manufactured by Kyowa Chemical Industry Co., Ltd.) Blena AE-400 (repeating number of ethylene oxide = 10, terminal hydroxyl group, manufactured by Nichite Corporation), Brena ANE-400 (repeating number of ethylene oxide = 30, terminal octadecyl group, 1300 (repeating number of ethylene oxide = 30, terminal nonylphenyl , And the like can be similarly prepared niche).

When the proportion of the monomer having a hydrophilic group in the mixed monomer is too small, the resulting pressure-sensitive adhesive composition for an optical member can not sufficiently suppress whitening occurring under high temperature and high humidity. When the proportion of the monomer having a hydrophilic group in the mixed monomer is excessively large, the resulting pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member lowers the initial wettability and adherence to the adherend is deteriorated, and reliability is inferior.

The ratio of 2-hydroxyethyl acrylate or N-vinylpyrrolidone in the mixed monomer is preferably 5% by weight, more preferably 8% by weight, more preferably 20% by weight, still more preferably 20% by weight, Is 15% by weight.

The ratio of the monomer having the structure represented by the general formula (1-1) or the monomer having the structure represented by the general formula (1-2) in the mixed monomer is preferably 1% by weight, more preferably 1% 2% by weight, preferably 20% by weight, and more preferably 15% by weight.

The mixed monomer preferably contains 10 to 60% by weight of a monomer having a bicyclo ring structure and one olefinic double bond.

The pressure-sensitive adhesive composition for an optical member, obtained by containing the monomer having the bicyclo ring structure and one olefinic double bond, dramatically improves the adhesion to an adherend. Such an improvement in adhesion is particularly effective when the adherend is a polycarbonate plate or an acrylic plate.

It is known that the polycarbonate plate and the acrylic plate are easy to absorb moisture, and the water is vaporized under a high temperature condition to generate outgas. Therefore, when the adherend is a polycarbonate plate or an acrylic plate, bubbles grow due to the gas pressure of the outgas under a high temperature condition, and are likely to be exfoliated and peeled off at the interface between the polycarbonate plate or the acrylic plate and the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive composition for an optical member, which is obtained by containing the monomer having the bicyclo ring structure and one olefinic double bond, can dramatically improve the adhesive force to the adherend, and the adherend is a polycarbonate plate or acrylic Plate, it is possible to suppress delamination and peeling occurring at the interface between the adherend and the pressure-sensitive adhesive layer.

The polycarbonate plate and the acrylic plate are used for a touch panel of an input device such as a cellular phone, a portable information terminal, and the like.

The bicyclo ring structure is not particularly limited, and examples of the functional group having a bicyclo ring structure include a bicyclo [1.1.0] butyl group, a bicyclo [1.1.1] pentyl group, a bicyclo [2.1.0 ] Pentyl group, a bicyclo [3.1.0] hexyl group, a bicyclo [2.1.1] hexyl group, a bicyclo [2.2.0] hexyl group, a bicyclo [2.2.1] heptyl group, a bicyclo [3.1.1 ] Heptyl group, a bicyclo [3.2.0] heptyl group, a bicyclo [4.1.0] heptyl group, a bicyclo [2.2.2] octyl group, a bicyclo [3.2.1] octyl group, a bicyclo [3.3.0 ] Octyl group, a bicyclo [3.2.1] octyl group, a bicyclo [4.1.1] octyl group, a bicyclo [4.2.0] octyl group, a bicyclo [ Nonocyclo [4.2.1] nonyl group, a bicyclo [4.3.0] nonyl group, a bicyclo [5.1.1] nonyl group, a bicyclo [5.2.0] ] Nonyl group, a bicyclo [4.3.1] decyl group, and a functional group having a structure in which a part of these hydrogen atoms are substituted with a chain alkyl group or a cyclic alkyl group There. The above substitution may be a single point or a plurality of points. Among them, as the functional group having the above-mentioned bicyclo ring structure, a norbornyl group and an isobornyl group are preferable, and an isobornyl group is particularly preferable.

The olefinic double bond is not particularly limited, and examples of the functional group having an olefinic double bond include a (meth) acryloyl group, a vinyl group, and an allyl group. Among them, as the functional group having an olefinic double bond, a (meth) acryloyl group is preferable.

As the monomer having the bicyclo ring structure and one olefinic double bond, for example, isobornyl (meth) acrylate having an isobornyl group and a (meth) acryloyl group is preferable.

When the proportion of the monomer having the bicyclo ring structure and the monomer having one olefinic double bond in the mixed monomer is less than 10% by weight, the resulting pressure-sensitive adhesive composition for an optical member has poor adhesion to an adherend, There may be a case where it is lowered. If the proportion of the monomer having the bicyclo ring structure and the monomer having one olefinic double bond in the mixed monomer exceeds 60% by weight, the glass transition temperature of the resulting acrylic copolymer may be increased. The pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member containing such an acrylic copolymer may adhere to an adherend in a deteriorated manner, resulting in lowered reliability.

The ratio of the above-mentioned bicyclo ring structure and the monomer having one olefinic double bond in the mixed monomer is more preferably 15% by weight, still more preferably 25% by weight, still more preferably 55% by weight, A more preferred upper limit is 40% by weight.

The mixed monomer preferably contains 30 to 80% by weight of a (meth) acrylic acid ester monomer having a structure represented by the following general formula (2). In the present specification, the (meth) acrylic acid ester monomer having the structure represented by the following general formula (2) is simply referred to as "(meth) acrylic acid ester monomer".

[Chemical Formula 5]

In the general formula (2), R ⁵ represents a hydrogen atom or a methyl group, and R ⁶ represents an alkyl group having ³ to 14 carbon atoms. The hydrogen atom of the alkyl group of R ⁶ may be substituted with a cycloalkyl group.

When the number of carbon atoms of the alkyl group of R < ⁶ > is 2 or less or 15 or more, the glass transition temperature of the obtained acrylic copolymer may be increased. The pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member containing such an acrylic copolymer may adhere to an adherend in a deteriorated manner, resulting in lowered reliability. The alkyl group of R < ⁶ > preferably has 4 to 12 carbon atoms.

The hydrogen atom of the alkyl group of R < ⁶ > may be substituted with a cycloalkyl group. The cycloalkyl group is not particularly limited, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

The (meth) acrylic acid ester monomer is not particularly limited and includes, for example, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, (Meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl ) Acrylate, and the like.

The pressure-sensitive adhesive layer comprising the obtained pressure-sensitive adhesive composition for an optical member is improved in cohesive strength, initial adhesion, adhesion, and the like, because the mixed monomer contains such a monomer. Among them, the pressure-sensitive adhesive layer having a low low-temperature elastic modulus and a high initial wettability can be obtained. Therefore, the (meth) acrylic acid ester monomer is preferably selected from the group consisting of 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate and butyl (Meth) acrylate monomer selected from the group consisting of (meth) acrylic acid ester monomers.

When the proportion of the (meth) acrylic acid ester monomer in the mixed monomer is less than 30% by weight, the resulting pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member has a low temperature elasticity and low initial wettability, And the reliability may be lowered. When the proportion of the (meth) acrylic acid ester monomer in the mixed monomer exceeds 80% by weight, the resulting pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member may have poor cohesive strength and lower processability.

The ratio of the (meth) acrylic acid ester monomer in the mixed monomer is more preferably 40% by weight, and still more preferably 65% by weight.

The mixed monomer may contain a monomer having a carboxyl group and one olefinic double bond.

Since the above-mentioned mixed monomer contains a monomer having the carboxyl group and one olefinic double bond, the resulting acrylic copolymer has increased intermolecular interaction. The pressure-sensitive adhesive layer comprising the acrylic copolymer-containing pressure-sensitive adhesive composition for an optical member has improved cohesion.

The mixed monomer may not contain a monomer having a carboxyl group and one olefinic double bond.

The monomer having a carboxyl group and one olefinic double bond is not particularly limited and examples thereof include (meth) acrylic acid, (meth) acryloyl acetic acid, (meth) acryloyl propionic acid, (meth) acryloyl butyric acid , Unsaturated monocarboxylic acids such as (meth) acryloylpentanoic acid and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid and itaconic acid.

The ratio of the carboxyl group to the monomer having one olefinic double bond in the mixed monomer is not particularly limited, but is preferably 2% by weight or less. When the ratio of the carboxyl group to the monomer having one olefinic double bond exceeds 2% by weight, the resulting pressure-sensitive adhesive composition for an optical member, when a thin metal film containing a metal such as ITO or a metal oxide is used as an adherend, The metal thin film may be easily deteriorated.

The ratio of the carboxyl group to the monomer having one olefinic double bond in the mixed monomer is more preferably 1% by weight or less, and still more preferably 0.5% by weight or less.

The method for producing the acrylic copolymer is not particularly limited. For example, the monomer having the hydrophilic group, and other monomers such as the monomer having an olefinic double bond and the bicyclo ring structure, , And a method of radical polymerization in the presence of a polymerization initiator.

The polymerization method is not particularly limited, and conventionally known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization and bulk polymerization can be mentioned.

The solvent used in the solution polymerization is not particularly limited, and examples thereof include ethyl acetate, toluene, dimethylsulfoxide, ethanol, acetone, diethyl ether and the like.

The amount of the solvent to be used in the solution polymerization is not particularly limited, but the lower limit is preferably 25 parts by weight and the upper limit is 300 parts by weight based on 100 parts by weight of the mixed monomer. If the blending amount of the solvent is less than 25 parts by weight, the molecular weight distribution of the resulting acrylic copolymer may be widened. The pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member containing such an acrylic copolymer may lower the adhesive force and the cohesive force to the adherend, and the reliability may be lowered in some cases. When the blending amount of the solvent is more than 300 parts by weight, it may be necessary to prepare a pressure-sensitive adhesive composition for an optical member using the acrylic copolymer to obtain a pressure-sensitive adhesive layer.

The polymerization initiator is not particularly limited, and examples thereof include persulfates, organic peroxides, and azo compounds. Among them, in the case where a metal thin film containing ITO or the like or a metal oxide is used as an adherend, an azo compound is preferable considering the influence on the metal thin film.

The persulfate is not particularly limited, and examples thereof include potassium persulfate, sodium persulfate, and ammonium persulfate. The organic peroxide is not particularly limited, and examples thereof include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxy pivalate, (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethyl Hexanoate, t-butylperoxyisobutylate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. The azo compound is not particularly limited, and examples thereof include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 4,4'-azobis 4-cyanopentanoic acid), 2,2'-azobis (2-methylbutyronitrile), and azobiscyclohexanecarbonitrile.

These polymerization initiators may be used alone or in combination of two or more.

The blending amount of the polymerization initiator is not particularly limited, but a preferable lower limit is 0.02 parts by weight and a preferable upper limit is 0.5 parts by weight based on 100 parts by weight of the mixed monomer. If the blending amount of the polymerization initiator is less than 0.02 parts by weight, the polymerization reaction may become insufficient or a long time may be required for the polymerization reaction. If the blending amount of the polymerization initiator is more than 0.5 parts by weight, the weight average molecular weight of the obtained acrylic copolymer may be excessively low or the molecular weight distribution may be excessively widened. The pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member containing such an acrylic copolymer may lower the adhesive force and the cohesive force to the adherend, and the reliability may be lowered in some cases.

The weight average molecular weight of the acrylic copolymer is preferably 200,000, and more preferably 1,500,000. When the acrylic copolymer has a weight average molecular weight of less than 200,000, the resulting pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member may have a low temperature elastic modulus and lower reliability. If the weight average molecular weight of the acrylic copolymer exceeds 1.5 million, the flowability of the acrylic copolymer may be lowered. The pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member containing such an acrylic copolymer may adhere to an adherend in a deteriorated manner, resulting in lowered reliability.

A more preferable lower limit of the weight average molecular weight of the acrylic copolymer is 300,000, a more preferable lower limit is 400,000, a still more preferable lower limit is 500,000, a more preferable upper limit is 1.2 million, a more preferable upper limit is 90,000, Is 65 million.

In the present specification, the weight average molecular weight means a value measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene. Specifically, for example, the acrylic copolymer is diluted 100 times with tetrahydrofuran (THF) to obtain a diluted solution. The diluted solution thus obtained is filtered with a filter, and the obtained filtrate is applied to a column (trade name: 2690 Separations Model ", etc.), and the weight average molecular weight can be determined by polystyrene conversion.

The solution containing the acrylic copolymer becomes a solution having a low viscosity. Therefore, when the pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive composition for an optical member containing the acrylic copolymer, the amount of the solvent required for application is small and the handling property is excellent. Further, it is easy to produce a thick pressure-sensitive adhesive layer, and the adhesive force of the pressure-sensitive adhesive layer to an adherend can be increased.

The viscosity of the pressure-sensitive adhesive composition solution for an optical member containing the acrylic copolymer is not particularly limited, but it is preferable to use a B-type viscometer (" B8U type viscometer " The lower limit is 500 mPa 占 퐏, and the preferable upper limit is 100000 mPa 占 퐏.

The pressure-sensitive adhesive composition for an optical member of the present invention may contain a crosslinking agent in addition to the acrylic copolymer.

By containing the crosslinking agent, a crosslinked structure can be formed in the acrylic copolymer. The gel fraction of the pressure-sensitive adhesive layer comprising the obtained pressure-sensitive adhesive composition for an optical member can be adjusted by appropriately adjusting the kind or amount of the crosslinking agent.

The crosslinking agent is not particularly limited, and examples thereof include an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, and a metal chelate crosslinking agent. In particular, the pressure-sensitive adhesive composition for an optical member of the present invention preferably contains at least one crosslinking agent selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents since it is easy to exhibit performance such as heat resistance and durability.

The isocyanate crosslinking agent is not particularly limited, but an aliphatic isocyanate crosslinking agent is preferred. Of the aliphatic isocyanate-based crosslinking agents, commercially available products include, for example, Colonate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.).

The epoxy cross-linking agent is not particularly limited, but an aliphatic epoxy cross-linking agent is preferred. Among the above-mentioned aliphatic epoxy cross-linking agents, commercially available products include, for example, Denacol EX212 and Denacol EX214 (both manufactured by Nagase Chemtech).

The blending amount of the crosslinking agent is not particularly limited, but a preferable lower limit is 0.1 part by weight and a preferable upper limit is 10 parts by weight based on 100 parts by weight of the acrylic copolymer. If the blending amount of the crosslinking agent is less than 0.1 part by weight, crosslinking of the acrylic copolymer becomes insufficient, and the resulting pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition for an optical member may have poor cohesive strength and poor processability. When the compounding amount of the crosslinking agent is more than 10 parts by weight, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member to be obtained may deteriorate the adhesive force and the initial adhesive property to the adherend, thereby lowering the reliability.

The blending amount of the crosslinking agent is more preferably 0.3 part by weight and more preferably 3.0 part by weight based on 100 parts by weight of the acrylic copolymer.

The pressure-sensitive adhesive composition for an optical member of the present invention may further contain a tackifier resin.

The tackifier resin is not particularly limited, and examples thereof include a xylene resin, a phenol resin, a rosin resin, a terpene resin and the like. These tackifier resins may be used alone or in combination of two or more. Among them, xylene resin is preferable and alkylphenol reactant of xylene resin is more preferable.

As the tackifier resin, a hydrogenated resin is preferable. By using such a hydrogenated resin, the resulting pressure-sensitive adhesive composition for an optical member has high transparency.

The pressure-sensitive adhesive composition for an optical member of the present invention may further contain a silane coupling agent.

By containing the silane coupling agent, the resulting pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member is improved in adhesion to an adherend.

The silane coupling agent is not particularly limited and includes, for example, vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane,? -Methacryloxypropylmethyldimethoxysilane,? -Glycidoxime Glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-aminopropyltri Aminopropyltriethoxysilane,? -Aminopropyltrimethylmethoxysilane, N- (2-aminoethyl) 3-aminopropyltriethoxysilane, N- (2-aminoethyl) Mercaptopropyltrimethoxysilane,? -Mercaptopropyltrimethoxysilane,? -Mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane,? -Mercaptopropylmethyldimethoxysilane, and the like.

The pressure-sensitive adhesive composition for an optical member of the present invention may further contain conventionally known additives as necessary within a range not hindering the effect of the present invention.

The additive is not particularly limited, and examples thereof include a filler and an antioxidant.

The method for producing the pressure-sensitive adhesive composition for an optical member of the present invention is not particularly limited. For example, the acrylic copolymer and, if necessary, the crosslinking agent, the tackifier resin, the silane coupling agent, Followed by stirring.

The use of the pressure-sensitive adhesive composition for an optical member of the present invention is not particularly limited, and can be applied to various optical members. Among them, the pressure-sensitive adhesive composition for an optical member of the present invention can be used as a protective plate for protecting the surface of an image display device when manufacturing an image display device such as a cellular phone or a portable information terminal, Further, when manufacturing an input device such as a mobile phone or a portable information terminal, it is preferable to use the polycarbonate plate or the acrylic plate of the touch panel for bonding the display panel.

INDUSTRIAL APPLICABILITY The pressure-sensitive adhesive composition for an optical member of the present invention can suppress whitening occurring under high temperature and high humidity, and therefore can be preferably applied to optical applications requiring high transparency such as bonding to a display panel, Can be realized.

The pressure-sensitive adhesive tape for optical members having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for optical members of the present invention may be produced, and the obtained pressure-sensitive adhesive tape for optical members may be applied to the above-described uses.

The adhesive tape for an optical member having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member of the present invention is also one of the present invention.

The gel fraction of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately adjusted in accordance with the use of the pressure-sensitive adhesive tape for optical members. The lower limit is preferably 30% by weight, and the upper limit is preferably 95% by weight. If the gel fraction of the pressure-sensitive adhesive layer is less than 30% by weight, the workability of the pressure-sensitive adhesive tape for optical members may be deteriorated. If the gel fraction of the pressure-sensitive adhesive layer exceeds 95% by weight, the initial pressure-sensitive adhesive layer may deteriorate in wettability, adherence to an adherend may deteriorate, and reliability may be lowered.

A more preferable lower limit of the gel fraction of the pressure-sensitive adhesive layer is 40% by weight, and a more preferable upper limit is 90% by weight.

The gel fraction can be measured by the following method.

First, the adhesive tape for an optical member of the present invention is cut into a flat rectangular shape of 50 mm x 25 mm to prepare a test piece. The pressure-sensitive adhesive layer of the obtained test piece was scraped off using a spoon to prepare a pressure-sensitive adhesive mass. The pressure-sensitive adhesive mass was immersed in ethyl acetate at 23 占 폚 for 24 hours and then the pressure-sensitive adhesive mass was taken out from the ethyl acetate through a 200 mesh stainless steel mesh. Lt; 0 > C for 1 hour. Then, the mass of the pressure-sensitive adhesive mass after drying is measured, and the gel fraction is calculated using the following formula (1).

Gel fraction (% by weight) = 100 x (W ₂ ) / (W ₁ ) (1)

In the formula (1), W ₁ represents the weight of the pressure-sensitive adhesive mass before the immersion, and W ₂ represents the weight of the pressure-sensitive adhesive mass after the immersion and drying. If necessary, the pressure sensitive adhesive layer may be swollen by immersing the test piece in a solvent before scraping off the pressure sensitive adhesive layer of the test piece with a spoon.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferable lower limit is 5 占 퐉 and a preferable upper limit is 1 mm. If the thickness of the pressure-sensitive adhesive layer is less than 5 占 퐉, the pressure-sensitive adhesive layer may deteriorate the adhesive force to the adherend, thereby lowering the reliability. If the thickness of the pressure-sensitive adhesive layer exceeds 1 mm, the pressure-sensitive adhesive component may seep out and the handling property may be lowered. More preferably, the lower limit of the thickness of the pressure-sensitive adhesive layer is 10 占 퐉, more preferably the lower limit is 20 占 퐉, more preferably the upper limit is 500 占 퐉, and still more preferably the upper limit is 300 占 퐉.

The adhesive tape for an optical member of the present invention may be of a non-support type having no base material or a support type having a pressure-sensitive adhesive layer formed on both surfaces of the base material.

The substrate is not particularly limited as long as it is a substrate having transparency and may be a sheet made of a transparent resin such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, polyimide, A sheet having a net-like structure, a sheet having a hole, and the like.

The thickness of the substrate is not particularly limited, but a preferable lower limit is 2 占 퐉 and a preferable upper limit is 200 占 퐉. If the thickness of the substrate is less than 2 탆, the resulting optical member adhesive tape may have insufficient strength, which may cause tearing or difficult handling. If the thickness of the base material exceeds 200 占 퐉, the elasticity of the base material is excessively strong, and the followability of the resulting adhesive tape for an optical member may deteriorate. A more preferable lower limit of the thickness of the substrate is 5 mu m, and a more preferable upper limit is 100 mu m.

The method for producing the pressure-sensitive adhesive tape for optical members of the present invention is not particularly limited. As a method for producing a non-support type adhesive tape for optical members, for example, a pressure-sensitive adhesive layer is formed by applying the pressure-sensitive adhesive composition for an optical member of the present invention onto a releasable surface of a release paper or a release film, A method in which the treated surface is brought into contact with the pressure-sensitive adhesive layer to obtain a laminate by superimposing newly prepared releasing paper or release film, and then the resulting laminate is pressed with a rubber roller or the like.

Further, in the method for producing an adhesive tape for optical member of the present invention, it is preferable that a method for producing a pressure-sensitive adhesive tape for an optical member, which comprises mixing a monomer having a hydrophilic group and other monomers such as a monomer having an olefinic double bond and the bicyclo ring structure, Is subjected to radical polymerization by bulk polymerization to prepare the above acrylic copolymer and to be subjected to a single step at the same time.

The mass polymerization is preferably a photopolymerization because the polymerization heat is easily removed and the reaction control is easy.

In particular, the method for producing the pressure-sensitive adhesive tape for an optical member of the present invention is a method for producing a pressure-sensitive adhesive tape for an optical member, which comprises the above-mentioned mixed monomer, a photopolymerization initiator and, if necessary, an additive, Treated on the surface of the release-treated transparent synthetic resin film to form a monomer layer. Thereafter, on the monomer layer, the release-treated surface of another transparent synthetic resin film having one surface thereof subjected to the release treatment is laminated, A method of radically polymerizing the mixed monomer by irradiating the monomer layer with light such as ultraviolet irradiation is preferably used.

When the pressure-sensitive adhesive tape for optical member of the present invention is produced by photopolymerization, a crosslinking structure can be formed at the same time as polymerization. Therefore, the above-mentioned mixed monomer is preferably a polyfunctional (meth) acrylate having two or more polymerizable functional groups .

The polyfunctional (meth) acrylate is not particularly limited and examples thereof include 1,6-hexanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, polypropylene glycol di (Meth) acrylate, poly (di (meth) acrylate, poly (di (meth) acrylate), poly (ethylene terephthalate) And ester di (meth) acrylate. Among them, 1,6-hexanediol diacrylate, polypropylene glycol diacrylate, hydrogenated polybutadiene diacrylate, polyurethane diacrylate, polyvinyl butyral diacrylate and the like are preferable from the viewpoints of a small decrease in the stress dispersion property of the obtained pressure- , And polyester diacrylate are preferable.

When the mixed monomer contains the polyfunctional (meth) acrylate, the blending amount of the polyfunctional (meth) acrylate is not particularly limited, but the lower limit of the mixed monomer is preferably 0.02 wt%, the upper limit is preferably 5 wt% to be. If the compounding amount of the polyfunctional (meth) acrylate is less than 0.02% by weight, crosslinking of the acrylic copolymer becomes insufficient, and the resulting pressure-sensitive adhesive layer may have poor cohesive strength and poor processability. If the compounding amount of the polyfunctional (meth) acrylate exceeds 5% by weight, the pressure-sensitive adhesive layer to be obtained may deteriorate the adhesive force and the initial adhesive property to the adherend, thereby lowering the reliability.

The mixing amount of the polyfunctional (meth) acrylate is more preferably 0.05% by weight, and more preferably 3% by weight, in the mixed monomer.

The photopolymerization initiator is not particularly limited and may be, for example, a ketone series such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (Merak Company, trade name "DARACURE 2959" (Trade name: DARACURE 1173, manufactured by Merck & Co., Ltd.), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone (Trade name: Irgacure 651), 2-hydroxy-2-cyclohexyl acetophenone (manufactured by Ciba Geigy Co., Ltd., trade name: Irgacure 184), benzyl dimethyl ketal Ketal photopolymerization initiators, halogenated ketones, acylphosphine oxides, acylphosphonates, and the like.

The blending amount of the photopolymerization initiator is not particularly limited, but a preferable lower limit is 0.01 part by weight and a preferable upper limit is 5 parts by weight based on 100 parts by weight of the mixed monomer. If the blending amount of the photopolymerization initiator is less than 0.01 part by weight, polymerization of the mixed monomer becomes incomplete, and the resultant pressure-sensitive adhesive layer may not be able to obtain necessary physical properties because of a decrease in cohesive force. When the blending amount of the photopolymerization initiator is more than 5 parts by weight, the amount of radical generation during light irradiation increases, the number average molecular weight of the obtained acrylic copolymer decreases, or the gel fraction of the pressure-sensitive adhesive layer decreases, There are cases where it can not be sufficiently suppressed.

The blending amount of the photopolymerization initiator is more preferably 0.03 part by weight and more preferably 1 part by weight based on 100 parts by weight of the mixed monomer.

The transparent synthetic resin film is not particularly limited, and examples thereof include a polyethylene terephthalate film.

The lamp used for the light irradiation is not particularly limited, and for example, a lamp having a light emission distribution at a wavelength of 400 nm or less can be used.

Mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps and the like as the lamps having a light emission distribution at the wavelength of 400 nm or less . In particular, it is preferred that the light of the active wavelength region of the photopolymerization initiator is efficiently emitted, the light absorption of components other than the photopolymerization initiator contained in the monomer layer is small, the light sufficiently reaches the interior of the monomer layer, Since a mixed monomer can be effectively polymerized, a chemical lamp is preferable.

The light irradiation intensity in the light irradiation is not particularly limited and is appropriately adjusted in accordance with the degree of polymerization of the desired acrylic copolymer or the performance of the pressure-sensitive adhesive layer, since it is a factor that determines the degree of polymerization of the obtained acrylic copolymer.

For example, when an acetophenone-based photopolymerization initiator is used as the photopolymerization initiator, the light irradiation intensity of the wavelength range effective for photodecomposition of the acetophenone-based photopolymerization initiator is preferably 0.1 to 100 mW / cm 2. The wavelength range effective for photodecomposition of the acetophenone-based photopolymerization initiator varies depending on the photopolymerization initiator, and is usually about 365 nm to 420 nm.

The application of the adhesive tape for an optical member of the present invention is not particularly limited and can be applied to various optical members. In particular, in the case of manufacturing an image display device such as a mobile phone or a portable information terminal, the adhesive tape for an optical member of the present invention can be used for protecting the surface of an image display device A polycarbonate plate or an acrylic plate of a touch panel and a display panel are used for bonding the display panel and the display panel when manufacturing the input device such as a cellular phone or a portable information terminal desirable.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability. Further, according to the present invention, it is possible to provide an adhesive tape for an optical member produced using the adhesive composition for an optical member.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1-1)

(1) Preparation of acrylic copolymer

In a reactor equipped with a thermometer, a stirrer and a cooling tube, 44.5 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, 25 parts by weight of 2-hydroxyethyl acrylate, 100 parts by weight of ethyl acetate was added to 100 parts by weight of these monomers, and after nitrogen substitution, the reactor was heated to initiate reflux. After 30 minutes, 0.2 part by weight of t-hexyl peroxy pivalate as a polymerization initiator was diluted with 5 parts by weight of ethyl acetate based on 100 parts by weight of the monomer, and the resulting polymerization initiator solution was added dropwise to the reactor over 2 hours. Thereafter, the mixture was refluxed at 70 DEG C for 8 hours from the start of the addition of the polymerization initiator to obtain an acrylic copolymer solution having a solid content of 50%.

The obtained acrylic copolymer was analyzed with a thermal decomposition apparatus (Double Short Pyrolyzer manufactured by Frontia Labo Co., Ltd.), a GC-MS apparatus (Q-1000GC manufactured by Nippon Denki Co., Ltd.), FT-IR (manufactured by Thermo Fisher Scientific, NICOLET6700 ) And NMR (JNM-ECA400, manufactured by Nippon Denshi Co., Ltd.) were used to measure the ratio (weight%) of the constituent units derived from each monomer constituting the acrylic copolymer. The ratio (% by weight) of the constituent units obtained is shown in Table 1.

The obtained acrylic copolymer was measured for its weight average molecular weight by polystyrene conversion by GPC method using "2690 Separations Model" manufactured by Waters Corporation as a column. The weight average molecular weights obtained are shown in Table 1.

(2) Production of adhesive tape for optical member

0.5 part by weight of Colonate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent was added to 100 parts by weight of the obtained acrylic copolymer and stirred to prepare a pressure-sensitive adhesive composition for optical member.

The resultant pressure-sensitive adhesive composition for an optical member was applied to the release-treated surface of the release type polyethylene terephthalate film to form a pressure-sensitive adhesive layer having a thickness of 100 占 퐉. On the pressure-sensitive adhesive layer thus obtained, the releasable polyethylene terephthalate film The phthalate film was laminated to obtain a laminate. The obtained laminate was pressed by a rubber roller to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

(Examples 1-2 to 1-5 and Comparative Examples 1-1 to 1-3)

Except that a modified polyethylene terephthalate film was applied to both sides of the adhesive tape in the same manner as in Example 1-1 except that an acrylic copolymer having a proportion (weight%) of the constituent units shown in Table 1 was obtained by changing the monomer composition of the acrylic copolymer Sensitive adhesive tape for an optical member was obtained.

(Example 2-1)

(1) Preparation of acrylic copolymer

59.5 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, and 25 parts by weight of N-vinylpyrrolidone were mixed in a reactor equipped with a stirrer, a thermometer, To 100 parts by weight of these monomers, 100 parts by weight of ethyl acetate was added, followed by nitrogen bubbling, and then the reactor was heated to 70 DEG C under a nitrogen flow. Subsequently, 0.2 part by weight of t-hexyl peroxy pivalate as a polymerization initiator was diluted with 5 parts by weight of ethyl acetate based on 100 parts by weight of the monomer, and the resulting polymerization initiator solution was added dropwise to the reactor over 2 hours. During the reaction, the temperature was controlled by heating and cooling so as to keep the reaction temperature at 70 캜. The reaction was carried out at 70 캜 for 8 hours from the start of the addition of the polymerization initiator, and then the reaction was terminated by cooling to obtain an acrylic copolymer solution having a solid content of 50%.

The obtained acrylic copolymer was analyzed with a thermal decomposition apparatus (Double Short Pyrolyzer manufactured by Frontia Labo Co., Ltd.), a GC-MS apparatus (Q-1000GC manufactured by Nippon Denki Co., Ltd.), FT-IR (manufactured by Thermo Fisher Scientific, NICOLET6700 ) And NMR (JNM-ECA400, manufactured by Nippon Denshi Co., Ltd.) were used to measure the ratio (weight%) of the constituent units derived from each monomer constituting the acrylic copolymer. Table 2 shows the ratio (% by weight) of the constituent units obtained.

The obtained acrylic copolymer was measured for its weight average molecular weight by polystyrene conversion by GPC method using "2690 Separations Model" manufactured by Waters Corporation as a column. The obtained weight average molecular weight is shown in Table 2.

(2) Production of adhesive tape for optical member

To 100 parts by weight of the acrylic copolymer obtained, 1.0 part by weight of Denacol EX212 (manufactured by Nagase ChemteX Corp.) as a crosslinking agent was added and stirred to prepare a pressure-sensitive adhesive composition for an optical member.

The resultant pressure-sensitive adhesive composition for an optical member was applied to the release-treated surface of the release type polyethylene terephthalate film to form a pressure-sensitive adhesive layer having a thickness of 100 占 퐉. On the pressure-sensitive adhesive layer thus obtained, the releasable polyethylene terephthalate film The phthalate film was laminated to obtain a laminate. The obtained laminate was pressed by a rubber roller to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

(Examples 2-2 to 2-8, Comparative Examples 2-1 to 2-3)

Except for obtaining an acrylic copolymer having a ratio (weight%) of the constituent units shown in Table 2 and a weight average molecular weight by changing the monomer composition of the acrylic copolymer and the amount of ethyl acetate in the reaction, In the same manner, a double-sided pressure-sensitive adhesive tape for optical member having a release type polyethylene terephthalate film adhered to both surfaces thereof was obtained.

(Example 3-1)

(1) Preparation of acrylic copolymer

59.3 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, 0.2 part by weight of 2-hydroxyethyl acrylate and 0.5 part by weight of acrylic acid were placed in a reactor equipped with a stirrer, , 5 parts by weight of Brena PME-1000 (repeating number of ethylene oxide = 23, terminal methyl group, manufactured by Niches Corporation) as a monomer having a structure represented by the general formula (1-1) and 100 parts by weight of ethyl acetate 100 parts by weight were added, and after nitrogen substitution, the reactor was heated to initiate reflux. After 30 minutes, 0.2 part by weight of t-hexyl peroxy pivalate as a polymerization initiator was diluted with 5 parts by weight of ethyl acetate based on 100 parts by weight of the monomer, and the resulting polymerization initiator solution was added dropwise to the reactor over 2 hours. Thereafter, the mixture was refluxed at 70 DEG C for 8 hours from the start of the addition of the polymerization initiator to obtain an acrylic copolymer solution having a solid content of 50%.

The obtained acrylic copolymer was measured for its weight average molecular weight by polystyrene conversion by GPC method using "2690 Separations Model" manufactured by Waters Corporation as a column. The weight average molecular weights obtained are shown in Table 3.

(2) Production of adhesive tape for optical member

0.5 part by weight of Colonate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent was added to 100 parts by weight of the obtained acrylic copolymer and stirred to prepare a pressure-sensitive adhesive composition for optical member.

The resultant pressure-sensitive adhesive composition for an optical member was applied to the release-treated surface of the release type polyethylene terephthalate film to form a pressure-sensitive adhesive layer having a thickness of 100 占 퐉. On the pressure-sensitive adhesive layer thus obtained, the releasable polyethylene terephthalate film The phthalate film was laminated to obtain a laminate. The obtained laminate was pressed by a rubber roller to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

(Examples 3-2 to 3-9 and Comparative Examples 3-1 to 3-5)

Acrylic copolymer having a weight average molecular weight shown in Table 3 or 4 was obtained by changing the monomer composition of the acrylic copolymer as shown in Tables 3 and 4 to obtain a modified polyethylene terephthalate Thereby obtaining a double-sided pressure-sensitive adhesive tape for an optical member in which the film was affixed to both surfaces.

(Example 3-10)

, 59.4 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, and Brena PME-1000 (a copolymer of ethylene oxide 5 parts by weight of 1,6-hexanediol diacrylate and 0.1 part by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by Chiba Chemical Co., Ltd., trade name: &Quot; Irgacure 651 ") were uniformly mixed, and then nitrogen purge was carried out to prepare a dissolved oxygen-free monomer composition.

The resulting monomer composition was sandwiched between two silicone-modified polyethylene terephthalate films each having a thickness of 38 mu m with a spacer of 100 mu m so as to have a thickness of 100 mu m so that each of the release-treated surfaces was in contact with the monomer composition. Subsequently, the monomer composition was irradiated with ultraviolet rays of 2 mW for 5 minutes by using a fluorescent lamp having a main wavelength of 365 nm and the monomers were polymerized to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

In addition, since the crosslinking structure is formed simultaneously with the polymerization, it is difficult to measure the weight average molecular weight of the obtained acrylic copolymer.

(Examples 3-11 to 3-18 and Comparative Examples 3-6 to 3-10)

Sensitive adhesive tape for optical member attached to both surfaces of a release type polyethylene terephthalate film in the same manner as in Example 3-10 except that the monomer composition of the acrylic copolymer was changed as shown in Table 5 or 6 to obtain an acrylic copolymer .

(Example 4-1)

(1) Preparation of acrylic copolymer

59.3 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, 0.2 part by weight of 2-hydroxyethyl acrylate and 0.5 part by weight of acrylic acid were placed in a reactor equipped with a stirrer, , 5 parts by weight of Brena PSE-1300 (repeating number of ethylene oxide = 30, end octadecyl group, manufactured by Niches Corporation) as a monomer having a structure represented by general formula (1-2), and 100 parts by weight of these monomers After 100 parts by weight of ethyl acetate was added and replaced with nitrogen, the reactor was heated to start reflux. After 30 minutes, 0.2 part by weight of t-hexyl peroxy pivalate as a polymerization initiator was diluted with 5 parts by weight of ethyl acetate based on 100 parts by weight of the monomer, and the resulting polymerization initiator solution was added dropwise to the reactor over 2 hours. Thereafter, the mixture was refluxed at 70 DEG C for 8 hours from the start of the addition of the polymerization initiator to obtain an acrylic copolymer solution having a solid content of 50%.

The obtained acrylic copolymer was measured for its weight average molecular weight by polystyrene conversion by GPC method using "2690 Separations Model" manufactured by Waters Corporation as a column. The weight average molecular weights obtained are shown in Table 7.

(2) Production of adhesive tape for optical member

0.5 part by weight of Colonate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent was added to 100 parts by weight of the obtained acrylic copolymer and stirred to prepare a pressure-sensitive adhesive composition for optical member.

The resultant pressure-sensitive adhesive composition for an optical member was applied to the release-treated surface of the release type polyethylene terephthalate film to form a pressure-sensitive adhesive layer having a thickness of 100 占 퐉. On the pressure-sensitive adhesive layer thus obtained, the releasable polyethylene terephthalate film The phthalate film was laminated to obtain a laminate. The obtained laminate was pressed by a rubber roller to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

(Examples 4-2 to 4-9 and Comparative Example 4-1)

Acrylic copolymer having a weight average molecular weight shown in Table 7 was obtained by changing the monomer composition of the acrylic copolymer as shown in Table 7. In the same manner as in Example 4-1 except that the modified polyethylene terephthalate film had a Thereby obtaining a double-sided pressure-sensitive adhesive tape for an optical member to which the adhesive was applied.

(Example 4-10)

59.4 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of isobornyl acrylate, 0.5 part by weight of acrylic acid, and Brena PSE-1300 (a copolymer of ethylene oxide 5 parts by weight of 1,6-hexanediol diacrylate and 0.1 part by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by Ciba Geigy Co., Ltd.) , Trade name " Irgacure 651 ") were uniformly mixed, and then nitrogen purge was carried out to prepare a monomer composition from which dissolved oxygen was removed.

The resulting monomer composition was sandwiched between two silicone-modified polyethylene terephthalate films each having a thickness of 38 mu m with a spacer of 100 mu m so as to have a thickness of 100 mu m so that each of the release-treated surfaces was in contact with the monomer composition. Subsequently, the monomer composition was irradiated with ultraviolet rays of 2 mW for 5 minutes by using a fluorescent lamp having a main wavelength of 365 nm and the monomers were polymerized to obtain a double-sided pressure-sensitive adhesive tape for optical member with a releasable polyethylene terephthalate film adhered to both surfaces.

In addition, since the crosslinking structure is formed simultaneously with the polymerization, it is difficult to measure the weight average molecular weight of the obtained acrylic copolymer.

(Examples 4-11 to 4-18 and Comparative Example 4-2)

A double-faced pressure-sensitive adhesive tape for optical member was obtained in the same manner as in Example 4-10, except that the monomer composition of the acrylic copolymer was changed as shown in Table 8 to obtain an acrylic copolymer, and the releasable polyethylene terephthalate film was attached to both surfaces .

(evaluation)

The following evaluations were carried out on the double-sided adhesive tape for optical member obtained in Examples and Comparative Examples. The results are shown in Tables 1 to 8.

(1) Measurement of gel fraction

From one side of the double-faced adhesive tape for an optical member obtained strip the release polyethylene terephthalate film, a pressure-sensitive adhesive layer-sided adhesive tape for optical member scraped with a spoon to prepare a pressure-sensitive adhesive mass, measuring the weight (W ₁₎ of the pressure-sensitive adhesive loaf Respectively. The mass of the pressure-sensitive adhesive was immersed in ethyl acetate at 23 占 폚 for 24 hours, and the mass of the pressure-sensitive adhesive was taken out from the ethyl acetate via a 200-mesh stainless steel mesh and dried for one hour at 110 占 폚. The weight (W ₂ ) of the mass of pressure-sensitive adhesive after drying was measured, and the gel fraction was calculated by the formula (1).

(2) Evaluation of generation of whiteness (measurement of haze value)

A release polyethylene terephthalate film was peeled from both sides of the obtained optical member double-faced pressure-sensitive adhesive tape, and a transparent polyethylene terephthalate film was attached to the surface of one side, and a slide glass (trade name "S-1214", manufactured by MATSUNAMI Co., Ltd.) A test piece having a three-layer structure of a pressure-sensitive adhesive layer / slide glass as a double-sided pressure-sensitive adhesive tape for a bonded, transparent polyethylene terephthalate film / optical member was prepared. The haze value (%) immediately after the preparation of the test piece and the haze value (%) of the test piece after allowing the test piece to stand for 24 hours under high temperature and high humidity at 80 占 폚 and 85% RH were measured with a haze meter (fully automatic haze meter "TC-HIIIDPK" Manufactured by TOKYO FUSION CO., LTD.), And a haze value was calculated by the following formula (2).

(2) Haze value (%) = {Haze value (%) of the test piece after being left for 24 hours} - {Haze value (%

(3) Adhesion evaluation

The obtained double-sided adhesive tape for optical member was cut so as to have a plane shape of 25 mm x 100 mm. One of the two release type polyethylene terephthalate films of the cut optical member double-sided adhesive tape was peeled off, and the exposed surface of the optical member double-sided adhesive tape was bonded onto the polyethylene terephthalate film. Further, the other one-side releasable polyethylene terephthalate film of the optical member double-stick adhesive tape was peeled off and the exposed surface of the double-sided adhesive tape for optical member was bonded onto a polycarbonate plate (PC plate) to form a polycarbonate plate ), A laminated sample in which a double-faced pressure-sensitive adhesive tape for optical members and a polyethylene terephthalate film were laminated in this order was obtained. Thereafter, a rubber roller of 2.0 kg was placed on a polyethylene terephthalate film of the obtained laminated sample, and a rubber roller was reciprocated once at a speed of 300 mm / minute to obtain a polycarbonate plate (PC plate) and a double- The mixture was allowed to stand at 23 DEG C for 20 minutes, and a test sample was prepared.

The obtained test sample was subjected to a tensile test in the direction of 180 占 at a peeling speed of 300 mm / min according to JIS Z0237, and the initial adhesive force (N / 25 mm) was measured. The obtained test sample was allowed to stand at 23 占 폚 for 24 hours and then subjected to a tensile test in the 180 占 direction at a peeling rate of 300 mm / min according to JIS Z0237, and the adhesive force (N / 25 mm) after 24 hours was measured .

(4) Bubbling state (foam resistance test)

The obtained double-sided adhesive tape for optical member was cut to have a planar shape of 45 mm x 60 mm. The one-side releasable polyethylene terephthalate film of the cut optical double-faced adhesive tape was peeled off and the exposed surface of the double-stick adhesive tape for optical member was bonded onto a polyethylene terephthalate film having a thickness of 0.5 mm. Further, the other one-side releasable polyethylene terephthalate film of the double-sided adhesive tape for optical members was peeled off, and the exposed surface of the double-sided adhesive tape for optical member was placed on a polycarbonate plate (PC plate) having a planar shape with a thickness of 2.0 mm A laminated sample was obtained in which a double-faced pressure-sensitive adhesive tape for optical members and a polyethylene terephthalate film were laminated in this order on a polycarbonate plate (PC plate). Thereafter, the resultant laminated sample was stopped for 24 hours under conditions of a temperature of 85 占 폚 or a temperature of 60 占 폚 and a relative humidity (RH) of 90% to obtain a test sample. The state of bubble formation at the bonding interface of the obtained test sample was visually observed.

A case where no bubbles having a size of 0.01 mm or more were observed at all, a case where bubbles having a size of 0.01 mm or more was observed with 1 to 5 bubbles per one test sample was defined as " The case where six or more samples were observed per one test sample was evaluated as " x ", and the state of bubble formation was evaluated.

(5) Presence or absence of whitening when pasted to the ITO film

On both surfaces of the obtained optical member double-faced pressure-sensitive adhesive tape, the release polyethylene terephthalate film was peeled off, an ITO film was attached to the surface of one side, and a slide glass (trade name: S- 1214, manufactured by MATSUNAMI) A three-layer structure of a pressure-sensitive adhesive layer / a slide glass as a double-sided adhesive tape for a film / optical member was prepared. The haze value (%) immediately after the preparation of the test piece and the haze value (%) of the test piece after being left for 24 hours were measured with a haze meter (fully automatic haze meter "TC-HIIIDPK Quot; manufactured by TOKYO FURNACING CO., LTD.), And the? Haze value was calculated by the above formula (2). ?,?,?, And?, Respectively. The? Haze value was evaluated as?, The? Haze value was less than 0.2, the?

(6) Evaluation of resistance between ITO films

The obtained double-sided adhesive tape for optical members was cut to have a planar shape of 40 mm long x 60 mm wide. Further, two adjacent corners in the width direction were cut into planar shapes each having a length of 10 mm from the edge and a width of 10 mm from the edge, to obtain a convex tape sheet. One of the release type polyethylene terephthalate films of the convex tape sheet was peeled off and the exposed surface of the convex tape sheet was bonded onto the polyethylene terephthalate. Further, the other one-side releasable polyethylene terephthalate film of the convex tape sheet was peeled off, and the exposed surface of the convex tape sheet was bonded onto the ITO film surface of the ITO film having a plane shape of 40 mm long × 60 mm wide, A conductive film laminate in which a double-faced adhesive tape for an optical member and polyethylene terephthalate were laminated in this order on the ITO film surface of the ITO film was obtained.

Thereafter, the initial resistance value of the obtained conductive film laminate was measured. Further, the conductive film laminate was allowed to stand under high temperature and high humidity at 60 占 폚 and relative humidity of 90% for 100 hours, and the resistance value of the conductive film laminate after leaving was measured using an amorphous ITO film (manufactured by Oike Kogyo Co., Ltd.). The resistance value of the terminal of the 2-terminal resistance value measuring instrument was measured against the exposed surface of the ITO film surface of 10 mm x 10 mm size.

The deterioration level of ITO was evaluated using the rate of change in resistance value calculated from the following formula (3).

(%) = (R ₁ -R ₀ ) / R ₀ × 100 (3)

In the formula (3), R ₀ represents an initial resistance value, and R ₁ represents a resistance value after being left under high temperature and high humidity for 100 hours.

The resistance value change rate is preferably 20% or less, and more preferably 15% or less. If the rate of change of the resistance value exceeds 20%, a wrong electrical signal is input to the recognition area of the touch panel having the ITO film, which may cause a bad response.

Industrial availability

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for an optical member capable of suppressing whitening occurring under high temperature and high humidity and realizing high reliability. Further, according to the present invention, it is possible to provide an adhesive tape for an optical member produced using the adhesive composition for an optical member.

Claims (12)

A pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer,
The acrylic copolymer is obtained by polymerizing a mixed monomer containing 0.5 to 30% by weight of a monomer having a structure represented by the following general formula (1-1).

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group having less than 3 carbon atoms, and n represents an integer of 13 to 45. A pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer,
Wherein the acrylic copolymer is obtained by polymerizing a mixed monomer containing 0.1 to 30% by weight of a monomer having a structure represented by the following general formula (1-2).

In the general formula (1-2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and m represents an integer of 13 to 45. 3. The method of claim 2,
In the general formula (1-2), R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having a carbon number of 18, and m is 30. A pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer,
The acrylic copolymer contains 0.5 to 30% by weight of a monomer having a structure represented by the following general formula (1-1), 25 to 60% by weight of a monomer having a bicyclo ring structure and one olefinic double bond Wherein the pressure-sensitive adhesive composition is obtained by polymerizing a mixed monomer.

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group having less than 3 carbon atoms, and n represents an integer of 8 to 45. A pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer,
The acrylic copolymer contains 0.1 to 30% by weight of a monomer having a structure represented by the following general formula (1-2), 25 to 60% by weight of a monomer having a bicyclo ring structure and one olefinic double bond Wherein the pressure-sensitive adhesive composition is obtained by polymerizing a mixed monomer.

In the general formula (1-2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 3 to 30 carbon atoms, and m represents an integer of 8 to 45. The method according to claim 4 or 5,
Wherein the bicyclo ring structure is a bicyclo ring structure of an isobornyl group. The method according to claim 4 or 5,
Wherein the olefinic double bond is an olefinic double bond of a (meth) acryloyl group. A pressure-sensitive adhesive composition for an optical member containing an acrylic copolymer,
The acrylic copolymer is obtained by polymerizing a mixed monomer containing 1 to 25% by weight of N-vinylpyrrolidone and 25 to 60% by weight of a monomer having a bicyclo ring structure and one olefinic double bond Sensitive adhesive composition for an optical member. 9. The method according to claim 4, 5 or 8,
Wherein the mixed monomer further contains 30 to 65% by weight of a (meth) acrylic acid ester monomer having a structure represented by the following general formula (2).

In the general formula (2), R ⁵ represents a hydrogen atom or a methyl group, and R ⁶ represents an alkyl group having ³ to 14 carbon atoms. The hydrogen atom of the alkyl group of R ⁶ may be substituted with a cycloalkyl group. 10. The method of claim 9,
The (meth) acrylic acid ester monomer having the structure represented by the general formula (2) is at least one selected from the group consisting of 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and butyl (meth) (Meth) acrylic acid ester monomer. The method according to claim 1, 2, 3, or 4,
Wherein the acrylic copolymer has a weight average molecular weight of 200,000 to 1,500,000. A pressure-sensitive adhesive tape for optical members, comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for an optical member according to any one of claims 1, 2, 3, 4, 5,