KR20190045153A - Acrylic pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet - Google Patents

Abstract

(Meth) acrylate ester monomer (a1) and (meth) acrylic acid alkyl ester monomer (a2) as an acrylic pressure sensitive adhesive composition suitable for coating thick coatings, which can obtain a pressure sensitive adhesive exhibiting excellent heat stability, (Meth) acrylic acid alkyl ester monomer (a2) is a (meth) acrylic acid alkyl ester monomer having a straight chain alkyl group having 10 to 24 carbon atoms ( (meth) acrylic acid ester monomer (a1) having a straight chain alkyl group having 10 to 24 carbon atoms and a copolymerizable component (a2-1) having 5 to 15% by weight of a (meth) acrylic acid ester monomer 1) in an amount of 50 to 94% by weight.

Description

Acrylic pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet

The present invention relates to an acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive comprising the acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet, and more particularly to an acrylic pressure-sensitive adhesive composition which is excellent in thermal stability, heat and humidity resistance, exhibits a low dielectric constant and is suitable for coating a thick coating .

2. Description of the Related Art In recent years, in a mobile device such as a television or a PC monitor, a notebook PC, a mobile phone, or a tablet terminal, a touch panel in which a liquid crystal display and a position input device are combined is widely used.

The touch panel generally comprises a liquid crystal display, a transparent conductive film substrate (ITO substrate), and a protective film (glass), and a transparent pressure sensitive adhesive sheet is used for interfacing these members.

Such a pressure-sensitive adhesive for a transparent pressure-sensitive adhesive sheet has not only an adhesive property such as adhesion, but also shock absorption property for preventing breakage of the liquid crystal display due to external impact, excellent optical property (transparency) A low dielectric constant or the like is required in order to suppress the malfunction of the touch panel caused by the noise.

As a pressure-sensitive adhesive having a low dielectric constant, for example, a pressure-sensitive adhesive using a (meth) acryl-based polymer obtained by polymerizing a monomer component containing an alkyl (meth) acrylate having a branched alkyl group at the terminal of an ester group having 10 to 18 carbon atoms as a main component , A methacrylic acid alkyl ester monomer having a long chain alkyl group having a carbon number of 10 or more at the alkyl ester site and a methacrylic acid alkyl ester monomer having an alkyl group having a carbon number of 1 to 9 at the alkyl ester site, A pressure-sensitive adhesive using a copolymer of a monomer mixture (A) containing a monomer (see Patent Document 2) is known.

On the other hand, in a pressure-sensitive adhesive for an optical member such as a touch panel, a drying step for volatilizing a solvent after coating the pressure-sensitive adhesive is unnecessary and is suitable for coating a thick coating. Therefore, an acrylic pressure- For example, a solvent-free type active energy ray-curable pressure-sensitive adhesive comprising a diluting monomer and a polyfunctional compound as a curing component is known, for example, (See Patent Document 3).

However, in the method using the diluted monomer, there is a problem that the unreacted monomer remaining in the pressure-sensitive adhesive layer lowers the durability at high temperature.

For this reason, hot-melt type pressure-sensitive adhesives that do not use a dilute monomer are used among solvent-free pressure-sensitive adhesives. The hot melt type pressure sensitive adhesive can obtain a pressure sensitive adhesive layer of a thick film having high durability at high temperature more efficiently.

Patent Document 1 JP 2012-246477A Patent Document 2 JP 2015-40237A Patent Document 3 JP 2009-57550A

However, in the hot melt method, since the resin is exposed to a high temperature for a long time, it is necessary that the resin is more excellent in thermal stability.

Since alkyl (meth) acrylates having branched alkyl groups are susceptible to removal of hydrogen at the branched positions, the acrylic resins obtained by using a large amount of alkyl (meth) acrylates having branched alkyl groups are poor in thermal stability, The pressure-sensitive adhesive described in Document 1 was not sufficient in terms of thermal stability when used in a hot-melt type pressure-sensitive adhesive.

In addition, since the acrylic resin described in Patent Document 2 uses a large amount of methacrylate having a small number of carbon atoms as the monomer of the acrylic resin, the acrylic resin has a high glass transition temperature and is difficult to handle when processed into a sheet by the hot melt method , Which makes it difficult to increase the molecular weight, resulting in poor reliability of the pressure-sensitive adhesive.

When the content of the hydroxyl group-containing monomer as the monomer component of the acrylic resin is increased, the moisture resistance of the pressure-sensitive adhesive improves. However, side reactions such as transesterification reaction tend to occur under high temperature conditions and tend to cause increase in molecular weight and gelation. When used as a pressure-sensitive adhesive, thermal stability was poor.

Accordingly, the present invention provides an acrylic pressure-sensitive adhesive composition which is excellent in thermal stability, resistance to humidity and humidity, and which can obtain a pressure-sensitive adhesive exhibiting a low dielectric constant under such a background, and is also suitable for coating thick coatings.

SUMMARY OF THE INVENTION Accordingly, the present inventors have conducted intensive studies in view of such circumstances, and as a result, have found that (meth) acrylic acid alkyl ester monomers having an alkyl group of a long chain and a straight chain, By using an acrylic resin which is contained as a main component and copolymerized with a copolymerizable component containing a specific amount of a hydroxyl group-containing (meth) acrylic acid ester monomer, a pressure-sensitive adhesive exhibiting excellent heat stability, , An acrylic pressure sensitive adhesive composition suitable for thick coating application can be obtained.

That is, the gist of the present invention is a pressure-sensitive adhesive composition comprising an acrylic resin (A) which is a copolymer of a copolymerizable component containing a hydroxyl group-containing (meth) acrylic ester monomer (a1) and a (meth) acrylic acid alkyl ester monomer (a2) (Meth) acrylic acid alkyl ester monomer (a2) comprises a (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms and the copolymerization component is a (Meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms in an amount of 5 to 15% by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive composition.

The present invention also provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition.

The acrylic pressure sensitive adhesive composition of the present invention is a pressure sensitive adhesive composition comprising an acrylic resin (A) which is a copolymer of a copolymerizable component containing a hydroxyl group-containing (meth) acrylic ester monomer (a1) and a (meth) acrylic acid alkyl ester monomer (a2) (Meth) acrylic acid alkyl ester monomer (a2) comprises a (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms and the copolymerization component is a (Meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms in an amount of 5 to 15% by weight. Therefore, the pressure-sensitive adhesive made of the acrylic pressure-sensitive adhesive composition is excellent in thermal stability and shows a low dielectric constant without yellowing of the resin by heating, and is also excellent in heat and humidity resistance, impact absorbability, . And, it is particularly useful as a pressure-sensitive adhesive used for sticking an optical member constituting a touch panel or an image display device.

When the copolymerization component further contains 0.1 to 20% by weight of the methacrylic acid alkyl ester monomer (a2-2) having an alkyl group having 4 to 8 carbon atoms as the (meth) acrylic acid alkyl ester monomer (a2) It is possible to increase the cohesive force while keeping it.

The proportion of the (meth) acrylic acid alkyl ester monomer (a2) having a straight chain alkyl group and the (meth) acrylic acid alkyl ester monomer having a branched chain containing alkyl group in the copolymerization component in the weight ratio 100/0 to 70/30, the thermal stability is further improved.

Further, when the weight average molecular weight of the acrylic resin (A) is 150,000 to 150,000, it is more excellent in resistance to moisture and humidity, impact absorbability, and step traceability.

When the acrylic resin (A) has an active energy ray-crosslinkable structural moiety, the acrylic resin (A) can be cured (crosslinked) efficiently to increase the cohesive force.

In addition, if the active energy ray-crosslinkable structural moiety is a benzophenone-based crosslinked structure, the reactive energy is excellent and the cohesive force can be further increased.

When the content of the volatile matter in the acrylic resin (A) is 2% by weight or less, a thicker coating can be applied.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail, but these are only examples of preferred embodiments.

In the present invention, (meth) acrylate means acrylate or methacrylate, (meth) acrylate means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate, The resin is a resin obtained by polymerizing a monomer component containing at least one (meth) acrylic monomer. The term " sheet " includes conceptually a sheet, a film, and a tape.

≪ Acrylic pressure-sensitive adhesive composition &

The acrylic pressure sensitive adhesive composition of the present invention comprises 5 to 15% by weight of a hydroxyl group-containing (meth) acrylic ester monomer (a1), 5 to 15% by weight of a (meth) acrylic acid alkyl ester monomer (a2) (A) which is a copolymer of a copolymerizable component containing 50 to 94% by weight of an alkyl ester monomer (a2-1).

The (meth) acrylic acid ester monomer (a1) containing a hydroxyl group typically has a hydroxyl group-containing (meth) acrylic acid ester monomer having 5 to 12 carbon atoms, preferably 5 to 10 carbon atoms, and particularly preferably 5 to 8 carbon atoms, Specific examples thereof include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl Hydroxypropyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, diethylene glycol (Meth) acrylate, hydroxyethyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl methacrylate, (Meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 3-chloro-2-hydroxypropyl Containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth) acrylate, and the like.

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

Above all, from the viewpoint of excellent reactivity with the crosslinking agent and from the viewpoint of improving the anti-wet heat resistance, monomers having a primary hydroxyl group are preferable, and acrylic acid hydroxyalkyl ester is preferable. Among them, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferable, and 4-hydroxybutyl acrylate is particularly preferable from the standpoint of ease of production, with few impurities such as di (meth) acrylate .

The content of the hydroxyl group-containing (meth) acrylic acid ester monomer (a1) in the copolymerization component is preferably 5 to 15% by weight, particularly preferably 8 to 14% by weight, Is 10 to 13% by weight.

When the content is too small, the anti-wet heat resistance tends to decrease. When the content is too large, the dielectric constant tends to be high.

The free acid contained in the hydroxyl group-containing (meth) acrylic ester monomer (a1) is preferably 1.0% or less, particularly preferably 0.5% or less, more preferably 0.1% or less.

When such a content is too large, the thermal stability tends to be reduced, and when the pressure-sensitive adhesive sheet is used, corrosion of the metal adherend tends to proceed easily.

Examples of the alkyl (meth) acrylate monomer (a2) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (Meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, (Meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, isotridecyl Isostearyl (meth) acrylate, isotetracosyl (meth) acrylate, and the like.

In the present invention, it is necessary that the (meth) acrylic acid alkyl ester monomer (a2) contains a (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms, Acrylate having a carbon number of 10), lauryl (meth) acrylate having a carbon number of 12, tridecyl (meth) acrylate having a carbon number of 13, hexadecyl (meth) acrylate having a carbon number of 16, (Meth) acrylate (having 18 carbon atoms), and behenyl (meth) acrylate (having 22 carbon atoms).

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

Among (meth) acrylic acid alkyl ester monomers (a2-1) having a straight chain alkyl group of 10 to 24 carbon atoms, alkyl methacrylate is used in view of low dielectric constant and low glass transition temperature of the acrylic resin (A) And stearyl methacrylate, lauryl methacrylate and tridecyl methacrylate are particularly preferable.

The content of the (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group of 10 to 24 carbon atoms is from 50 to 94% by weight, preferably from 60 to 83% by weight, 70 to 80% by weight.

When the content is too small, the dielectric constant tends to be high or the thermal stability of the acrylic resin (A) tends to be lowered.

Further, in the present invention, it is preferable that the (meth) acrylic acid alkyl ester monomer (a2) contains a methacrylic acid alkyl ester monomer (a2-2) having an alkyl group having 4 to 8 carbon atoms from the viewpoint of improving the cohesive force. The alkyl group of the methacrylic acid alkyl ester monomer (a2-2) having an alkyl group of 4 to 8 carbon atoms may be either a straight chain alkyl group or a branched chain alkyl group.

Examples of the methacrylic acid alkyl ester monomer (a2-2) having an alkyl group having 4 to 8 carbon atoms include iso-butyl methacrylate (the number of carbon atoms in the alkyl group is 4), tert-butyl methacrylate -Ethylhexyl methacrylate (having 8 carbon atoms), and the like.

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

Among them, the monomer having a tertiary carbon in the alkyl group can efficiently remove the hydrogen during the photo-crosslinking to increase the cohesive force, and the other monomer has a high glass transition temperature to improve the cohesive force.

Of the methacrylic acid alkyl ester monomers (a2-2) having an alkyl group of 4 to 8 carbon atoms, tert-butyl methacrylate, 2-ethylhexyl methacrylate Is preferably used.

The content of the methacrylic acid alkyl ester monomer (a2-2) having an alkyl group having from 4 to 8 carbon atoms is preferably from 0.1 to 20% by weight, particularly preferably from 1 to 18% by weight, Is 5 to 15% by weight.

When the content is too small, the cohesive strength tends to decrease. When the content is too large, the thermal stability and handling tend to deteriorate.

(Meth) acrylic acid alkyl ester monomer (a2) having a linear alkyl group and a (meth) acrylic acid alkyl ester monomer having a branched chain containing alkyl group in the copolymerization component in a proportion of a weight ratio Is preferably 100/0 to 70/30, particularly preferably 100/0 to 80/20, and more preferably 90/10 to 85/15.

When the content of the (meth) acrylic acid alkyl ester monomer having an alkyl group having a branched chain is too large, the thermal stability of the resin tends to decrease. When the content of the alkyl (meth) acrylate monomer having a straight chain alkyl group is too large, Is lowered.

Further, in the present invention, from the viewpoint of efficiently increasing the cohesive force while keeping the dielectric constant low, it is preferable that a branched chain alkyl group such as a branched chain containing monomer having a tertiary carbon in the alkyl group and a branched chain containing monomer having a tert- (Meth) acrylic acid alkyl ester monomer (a2).

The branched chain-containing monomer having tertiary carbon in the alkyl group can efficiently remove hydrogen during photo-crosslinking to increase the cohesive force. The branched chain-containing monomer having a tert-butyl group such as tert-butyl (meth) By increasing the glass transition temperature, the cohesive force can be improved.

Among them, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and tert-butyl (meth) acrylate are used as the (meth) acrylic acid alkyl ester monomer (a2) having a branched chain- And particularly preferably 2-ethylhexyl (meth) acrylate or tert-butyl (meth) acrylate.

The content of the (meth) acrylic acid alkyl ester monomer (a2) is preferably from 51 to 95% by weight, more preferably from 70 to 90% by weight, particularly preferably from 80 to 88% by weight, based on the entire copolymerization component.

If the content of the (meth) acrylic acid alkyl ester monomer (a2) is too small, the adhesion tends to be insufficient.

In addition, the acrylic resin (A) used in the present invention preferably has an active energy ray-crosslinkable structural moiety from the viewpoint of efficiently curing (crosslinking) the acrylic resin and enhancing cohesive force.

The active energy ray-crosslinkable structural moiety is a structural moiety capable of forming a crosslinked structure by reacting with a part of the acrylic resin (A) or other curing components contained in the acrylic resin composition by irradiation with active energy rays.

In the present invention, the active energy ray-crosslinkable structural moiety is preferably a benzophenone based crosslinked structure from the viewpoint of high reactivity and excellent cohesive strength.

Therefore, in the present invention, it is preferable to use (meth) acrylate monomer (a3) containing an active energy ray-crosslinkable structural moiety as a copolymerization component of the acrylic resin (A).

As the (meth) acrylic ester monomer (a3) containing an active energy ray-crosslinkable structural moiety, it is possible to form an effective crosslinked structure by an active energy ray such as ultraviolet ray or electron ray, in which a (meth) acrylic acid ester monomer having a benzophenone structure is contained (Meth) acryloyloxybenzophenone, and the like. Specific examples thereof include 4- (meth) acryloyloxybenzophenone and the like.

The content of the (meth) acrylic acid ester monomer (a3) containing an active energy ray-crosslinkable structural moiety is preferably 0.01 to 5% by weight based on the total of the copolymerization components, and among these, a (meth) acrylic acid ester The content of the monomer is preferably from 0.01 to 5% by weight, particularly preferably from 0.1 to 2% by weight, more preferably from 0.2 to 1% by weight, based on the entire copolymerization component. When the content is too small, there is a tendency that the holding power at the time of forming the crosslinked structure by the active energy ray is lowered. In addition, when the crosslinked structure is formed to prepare a processable pressure sensitive adhesive sheet, A large amount of energy is required at the time of preparing the pressure-sensitive adhesive sheet, and efficient production tends to become difficult. If the content is too large, the cohesive force of the entire system becomes too high, and the adhesion tends to decrease.

In the present invention, if necessary, other copolymerizable ethylenically unsaturated monomer (a4) may be contained as a copolymerization component.

Examples of the other copolymerizable ethylenic unsaturated monomer (a4) include phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol Acrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol-polypropylene glycol- (meth) acrylate, orthophenylphenoxyethyl (meth) acrylate, (Meth) acrylate such as cyclohexyl (meth) acrylate, cyclohexyloxyalkyl (meth) acrylate, tert-butylcyclohexyloxyethyl (meth) acrylate Containing monomer such as isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate and the like; alicyclic monomers containing 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (Meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, 2-butoxyethyl Acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, (Meth) acrylic acid,? -Carboxyethyl acrylate and the like, acrylic acid dimers such as (meth) acrylic acid and? -Carboxyethyl acrylate, crotonic acid, maleic acid , Carboxyl group-containing monosaccharides such as maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycolic acid, (Meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylacetamide Amino group-containing monomers such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and quaternary compounds thereof, and other amino group-containing monomers such as acrylonitrile, Vinylidene chloride, vinylidene chloride, alkylvinylether, vinyltoluene, vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid, fumaric acid, Dialkyl esters, aryl alcohols, acrylic chlorides, methyl vinyl ketones, N-acrylamidomethyltrimethylammonium chlorides, aryltrimethylammonium chlorides, dimethylaryl vinyl ketones and the like.

These may be used alone, or two or more of them may be used in combination.

For the purpose of increasing the molecular weight of the acrylic resin (A), ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (Meth) acrylate, propylene glycol di (meth) acrylate, divinylbenzene, and the like may be used in combination.

The content of the other copolymerizable ethylenic unsaturated monomer (a4) is preferably 0 to 20% by weight, particularly preferably 0 to 10% by weight, more preferably 0 to 5% by weight, based on the entire copolymerization component .

If the content is too high, the thermal stability tends to deteriorate or the adhesive strength tends to deteriorate.

When a carboxyl group-containing monomer is used as the other copolymerizable ethylenically unsaturated monomer (a4), such a content is preferably 0 to 0.1% by weight, more preferably 0 to 0.07% by weight, , And further preferably 0 to 0.05% by weight. If the content is too large, there is a possibility that the metal or metal oxide of the adherend such as the ITO film is corroded or deteriorated.

The acrylic resin (A) used in the present invention is obtained by copolymerizing the above-mentioned (meth) acrylic acid ester monomer (a1) having hydroxyl groups and the (meth) acrylic acid alkyl ester monomer (a2-1) having a linear alkyl group having 10 to 24 carbon atoms And optionally polymerizing and polymerizing the above-mentioned optional polymerization components.

As the polymerization method of the acrylic resin (A), conventionally known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be used. In the present invention, however, From the viewpoint that an acrylic resin (A) can be produced with an arbitrary monomer composition.

Hereinafter, the acrylic resin (A) used in the present invention is an example of a preferable production method.

First, a copolymerization component and a polymerization initiator are mixed or dripped into an organic solvent and then subjected to solution polymerization to obtain an acrylic resin (A) solution.

[Organic solvent]

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as n-hexane, esters such as methyl acetate, ethyl acetate and butyl acetate, and alcohols such as methyl alcohol, ethyl Aliphatic alcohols such as alcohol, n-propyl alcohol and isopropyl alcohol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, aliphatic ethers such as dimethyl ether and diethyl ether, Aliphatic halogenated hydrocarbons such as ethylene, and cyclic ethers such as tetrahydrofuran. Among these solvents, it is preferable to use a solvent having a boiling point of 70 캜 or lower from the viewpoint of removing the solvent from the acrylic resin solution obtained by solution polymerization and efficiently producing a solvent-free acrylic resin.

Examples of the organic solvent having a boiling point of 70 ° C or lower include hydrocarbons such as n-hexane (67 ° C), aliphatic alcohol mols such as methanol (65 ° C), esters such as methyl acetate (54 ° C) (40 ° C), cyclic ethers such as tetrahydrofuran (66 ° C), and the like, and the like. Examples of the solvent include aliphatic hydrocarbons such as tetrahydrofuran Among them, acetone and methyl acetate are preferably used from the viewpoints of versatility and safety, and acetone is particularly preferably used.

Further, the numerical values in parentheses following each organic solvent name are boiling points.

[Polymerization initiator]

As the polymerization initiator used in the polymerization reaction, azo-based polymerization initiators and peroxide-based polymerization initiators which are common radical polymerization initiators can be used. Examples of the azo-based polymerization initiators include 2,2'-azobis (2 Azobisisobutyronitrile, 2,2'-azobisisobutyronitrile, (1-phenylethyl) azodiphenylmethane, 2,2'-azobis (2,4-dimethylvaleronitrile) Azobis (2-cyclopropylpropionitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), and the like. Examples of the peroxide-based polymerization initiator include For example, there may be mentioned benzoyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, tert-butyl peroxypivalate, tert- , Diisopropyl peroxycarbonate, diisobutyryl peroxide, and the like.

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

In the production of the acrylic resin (A) used in the present invention, the polymerization is preferably carried out at a relatively low temperature using an organic solvent having a boiling point of 70 ° C or lower as a reaction solvent for solution polymerization. At this time, If a polymerization initiator is used, the polymerization initiator tends to remain. If the polymerization initiator remains, gelation of the acrylic resin (A) tends to occur in the step of removing the solvent from the acrylic resin (A) solution described later.

Therefore, from the viewpoint of stably carrying out the step of removing the solvent from the solution of the acrylic resin (A) obtained by solution polymerization, it is preferable to use a polymerization initiator having a half-life temperature of 10 hours and less than 60 ° C for 10 hours, Among them, 2,2'-azobis (2,4-dimethylvaleronitrile) (52 ° C), 2,2'-azobis (2-cyclopropylpropionitrile) Butyl peroxypivalate (54.6 占 폚), tert-hexyl peroxy pivalate (53.2 占 폚), tert-hexyl peroxy Diisopropyl peroxycarbonate (40.5 占 폚) and diisobutyryl peroxide (32.7 占 폚) are preferable, and 2,2'-azobis (2,4-dimethylvaleronitrile ) (52 캜), and tert-hexyl peroxy pivalate (53.2 캜).

Further, the values in parentheses following each compound name are the 10-hour half-life temperature of each compound.

The amount of the polymerization initiator to be used is generally 0.001 to 10 parts by weight, preferably 0.1 to 8 parts by weight, particularly preferably 0.5 to 6 parts by weight, more preferably 1 to 4 parts by weight, based on 100 parts by weight of the copolymerization component Particularly preferably 1.5 to 3 parts by weight, and most preferably 2 to 2.5 parts by weight. When the amount of the polymerization initiator used is too small, the polymerization rate of the acrylic resin (A) is lowered and the residual monomer tends to increase or the weight average molecular weight of the acrylic resin (A) tends to increase. Gelation of the acrylic resin (A) tends to occur in the step of removing the solvent from the resin (A) solution.

[Polymerization conditions, etc.]

The polymerization conditions for the solution polymerization may be polymerized in accordance with conventionally known polymerization conditions. For example, the copolymerization component containing a (meth) acrylic monomer and a polymerization initiator may be mixed or added in a solvent to polymerize can do.

The polymerization temperature in the polymerization reaction is usually 40 to 120 ° C, but in the present invention, 50 to 90 ° C is preferable, 55 to 75 ° C, particularly 60 to 70 ° C is preferable from the viewpoint of stable reaction . If the polymerization temperature is too high, the acrylic resin (A) tends to gel, whereas if it is too low, the activity of the polymerization initiator lowers, so the polymerization rate lowers and the residual monomer tends to increase.

There is no particular limitation on the polymerization time in the polymerization reaction (the time until the last heating is started in the case of performing the final heating described later), but it is preferably 0.5 hour or more, preferably 1 hour or more, More preferably not less than 2 hours, particularly preferably not less than 5 hours.

The polymerization reaction is preferably carried out while refluxing the solvent from the viewpoint of easy heat removal.

In the production of the acrylic resin (A) of the present invention, in order to reduce the amount of the residual polymerization initiator, it is preferable to perform the last spurt heating in order to heat decompose the polymerization initiator.

The final heating temperature is preferably higher than the 10-hour half-life temperature of the polymerization initiator. Specifically, the final heating temperature is preferably 40 to 150 占 폚, 55 to 130 占 폚, 95 < 0 > C. If the final heating temperature is too high, the acrylic resin (A) tends to yellow, while if it is too low, the polymerization monomer and the polymerization initiator remain and the stability of the acrylic resin (A) over time and the thermal stability tends to be lowered.

Thus, a solution of the acrylic resin (A) can be obtained.

The acrylic resin (A) solution can be used in the acrylic pressure sensitive adhesive composition of the present invention even in a state containing a little solvent, but in the present invention, when substantially all of the solvent is removed from the acrylic pressure sensitive adhesive composition and used as a solventless pressure sensitive adhesive, . For this reason, the solvent is usually removed from the obtained acrylic resin (A) solution.

The step of removing the solvent from the acrylic resin (A) solution can be carried out by a publicly known method. Examples of the method of removing the solvent include a method of removing the solvent by heating and a method of removing the solvent by decompression. From the viewpoint of efficient removal of the solvent, a method of removing by heating under reduced pressure is preferable.

The temperature in the case of removing the solvent by heating is preferably 60 to 150 DEG C. In particular, the reaction solution after polymerization of the acrylic resin (A) is kept at 60 to 80 DEG C to distill out the solvent, From the viewpoint of greatly reducing the residual solvent amount, it is preferable to let the solvent flow out at ~150 캜. From the viewpoint of suppressing the gelation of the acrylic resin (A), it is preferable that the temperature at the time of removing the solvent is not carried out at 150 캜 or higher.

When the solvent is removed by decompression, the pressure is preferably 20 to 101.3 kPa, more preferably 50 to 101.3 kPa to distill the solvent in the reaction solution, From the viewpoint of greatly reducing the residual solvent amount, it is preferable to discharge the solvent.

Thus, the acrylic resin (A) used in the present invention can be produced.

The acrylic resin (A) used in the present invention preferably has a weight average molecular weight of 100,000 or more, more preferably from 150,000 to 150,000, particularly preferably from 200,000 to 1,000,000, and particularly preferably from 250,000 to 80,000 , And particularly preferably from 300,000 to 600,000. If the weight average molecular weight is too large, the viscosity tends to become too high, and the coatability and handling tends to deteriorate. When the weight average molecular weight is too small, the cohesive force tends to decrease and the durability tends to deteriorate.

The weight average molecular weight of the acrylic resin (A) is the weight average molecular weight of the acrylic resin (A) which is not heated after the production and is the weight average molecular weight at the completion of the production.

The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, more preferably 10 or less, particularly preferably 7 or less, especially 5 or less. When the degree of dispersion is too high, the durability of the pressure-sensitive adhesive layer tends to deteriorate and foaming tends to occur. When the degree of dispersion tends to be too low, the handling property tends to decrease. Further, the lower limit of the degree of dispersion is usually 1.1 in view of manufacturing limitations.

The above weight average molecular weight was a weight average molecular weight in terms of standard polystyrene molecular weight, and the weight average molecular weight was measured using a high-performance liquid chromatograph ("Waters 2695 (main body)" and "Waters 2414 Three serials of L (exclusion limit molecular weight: 2 x 10 ⁷ , separation range: 100 to 2 x 10 ⁷ , theoretical number of steps: 10,000 units / filler material: styrene-divinylbenzene copolymer, , And the number average molecular weight can be measured using the same method. The degree of dispersion can be determined by the weight average molecular weight and the number average molecular weight.

The acrylic resin (A) used in the present invention preferably has a glass transition temperature (Tg) of -100 to 50 ° C, particularly preferably -50 to 20 ° C, and more preferably -20 to 0 ° C. If the glass transition temperature is too high, the melting viscosity of the acrylic resin (A) becomes high, so that the required heating temperature at the time of coating increases and the stability of the acrylic resin (A) may be impaired. There is a tendency to deteriorate. If the glass transition temperature is too low, thermal durability tends to be lowered.

The glass transition temperature (Tg) is determined by the following measurement method.

A release sheet is peeled off from the pressure sensitive adhesive sheet before irradiation with active energy rays, which will be described later, to form a pressure sensitive adhesive sheet having a thickness of about 650 占 퐉 in an uncrosslinked state. The dynamic viscoelasticity of the prepared sheet is measured under the following conditions, and the temperature at which the loss tangent (loss elastic modulus G "/ storage elastic modulus G '= tanδ) becomes maximum is read to obtain Tg of the acrylic resin.

〔Measuring conditions〕

Measuring instrument: DVA-225 (manufactured by Haitai Kasei Corporation)

Deformation Mode: Shear

Distortion: 0.1%

Measuring temperature: -100 to 20 ° C

Measuring frequency: 1Hz

The melting viscosity (mPa 占 퐏) of the acrylic resin (A) at 100 占 폚 is preferably 1,000 to 10,000,000 mPa 占 퐏, particularly preferably 50,000 to 1,000,000 mPa 占 퐏, more preferably 200,000 to 600,000 mPa · S. If the viscosity is too low, the durability tends to be lowered due to the lowering of the molecular weight. If the viscosity is too high, the handling property tends to be lowered and the coating becomes difficult.

Further, the above viscosity is a value obtained by measuring a load of 30 kg, an orifice diameter of 1.0 mm, a die length of 10 mm, and a measurement temperature of 100 DEG C by using a " high performance flow tester " manufactured by Shimadzu Corporation.

The acrylic resin (A) of the present invention is preferably used as a solvent-free, non-solvent type acrylic resin. In this case, the content of the acrylic resin (A) in the solvent is preferably 2% by weight or less, 2% by weight, especially 0.0001 to 1% by weight, especially 0.001 to 0.1% by weight. When the content of the solvent is too large, bubbles are generated in the pressure-sensitive adhesive layer when used as a pressure-sensitive adhesive, and durability tends to be lowered.

The residual monomer content in the acrylic resin (A) of the present invention is preferably 2% by weight or less, particularly preferably 0.00001 to 1.5% by weight, more preferably 0.0001 to 1.0% by weight. If the amount of the residual monomer is too large, the molecular weight increases upon heating, and the coating property and the adhesive property tend to be lowered, or bubbles are generated in the pressure-sensitive adhesive, and the durability tends to decrease.

The content of the solvent and the amount of residual monomer in the acrylic resin (A) were determined by diluting the acrylic resin (A) 20 times with toluene and measuring the amount of the acrylic resin (A) with a gas chromatography / mass fraction detector (GC: 7890 AGCsystem, MSD: Agilent Technologies 5975 inert). ≪ / RTI >

In the present invention, the content of volatile matter in the acrylic resin (A) (usually, the solvent and the remaining monomer are the main components) is preferably 2% by weight or less, particularly preferably 0.00001 to 1.5% by weight, more preferably 0.0001 to 1.0% Weight%. When the amount of the residual monomer is too large, the molecular weight of the acrylic resin (A) is increased when heated and the coating property is lowered. In the case of the pressure-sensitive adhesive, the pressure-sensitive adhesive property is lowered or bubbles are generated and the durability is lowered.

The content of the volatile matter in the acrylic resin (A) is a value calculated by heating the acrylic resin in a circular aluminum foil having a diameter of 50 mm in an amount of 1.5 g in a hot air dryer at 130 캜 for one hour before heating and after heating.

The acrylic pressure sensitive adhesive composition of the present invention preferably contains 90% by weight or more, more preferably 95 to 99.9% by weight, particularly preferably 98 to 99.9% by weight, particularly 99 to 99.9% by weight of the acrylic resin (A) %.

The acrylic pressure-sensitive adhesive composition of the present invention can be a pressure-sensitive adhesive made by curing an acrylic pressure-sensitive adhesive composition by subjecting it to active energy ray irradiation treatment as described later and then aging, but in the case of curing with an active energy ray , And a photopolymerization initiator (B) may be added from the viewpoint of stabilizing the reaction upon irradiation with active energy rays.

The photopolymerization initiator (B) is not particularly limited as long as it generates radicals by the action of light. Examples of the photopolymerization initiator (B) include photopolymerization initiators such as acetophenone, benzoin, benzophenone, thioxanthone and acylphosphine oxide Although it is preferable to use a hydrogen-removable benzophenone-based photopolymerization initiator from the viewpoint of efficient crosslinking between molecules or within the molecule.

Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoyl benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. These may be used alone or in combination of two or more.

As the preparation of these photopolymerization initiators (B), triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Mihira ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid , Ethyl 4-dimethylaminobenzoate, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, 4-dimethylaminobenzoic acid isoamyl, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diisopropylthioxanthone and the like can be used in combination. These preparations may be used alone or in combination of two or more.

The blending amount of such photopolymerization initiator (B) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the acrylic resin (A) Wealth. If the amount is too small, the curing rate tends to be lowered or the curing tends to be insufficient, and if too much, the curability is not improved and the economical efficiency tends to be lowered.

When curing by an active energy ray is carried out, an active energy ray-curable monomer such as a monofunctional monomer or a polyfunctional monomer can also be contained. Thus, the cohesive force of the whole pressure-sensitive adhesive layer can be adjusted to obtain stable adhesive property.

As the active energy ray-curable monomer, a multifunctional monomer containing two or more ethylenic unsaturated groups in a molecule is preferable, and examples thereof include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (Meth) acrylates such as ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (Meth) acrylate such as pentaerythritol hexa (meth) acrylate, trimethylol propane tri (meth) acrylate, tetramethylol methane tri (meth) acrylate, isocyanuric acid ethylene oxide- , Vinyl (meth) acrylate, and urethane (meth) acrylate. The polyfunctional monomers may be used alone or in combination of two or more.

The multifunctional monomer is preferably used in an amount of 0 to 5 parts by weight, particularly preferably 0.01 to 2 parts by weight, more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the acrylic resin (A) .

The acrylic pressure sensitive adhesive composition of the present invention may be blended with other pressure sensitive adhesives as required, or may be blended with conventionally known additives such as crosslinking agents, crosslinking accelerators, silane coupling agents, antistatic agents, tackifiers, and functional dyes.

Thus, the acrylic pressure sensitive adhesive composition of the present invention can be obtained by mixing the acrylic resin (A), the photopolymerization initiator (B) and other optional components as required. In addition, the mixing method is not particularly limited, and various methods such as a method of collectively mixing the components, a method of mixing arbitrary components, and a method of collectively or sequentially mixing the remaining components have.

The acrylic pressure-sensitive adhesive composition of the present invention has a melt viscosity (mPa · s) at 100 ° C of preferably 1,000 to 10,000,000 mPa · s, particularly preferably 50,000 to 1,000,000 mPa · s, more preferably 200,000 to 600,000 mPa · s. If the viscosity is too low, the durability tends to be insufficient due to the lowering of the molecular weight. If the viscosity is too high, the handling property tends to be lowered and coating becomes difficult.

The content of the solvent in the acrylic pressure sensitive adhesive composition of the present invention is preferably 2% by weight or less, more preferably 0.00001 to 2% by weight, particularly 0.0001 to 1% by weight, particularly 0.001 to 0.1% by weight. When the content of the solvent is too large, bubbles are generated in the pressure-sensitive adhesive layer when used as a pressure-sensitive adhesive, and durability tends to be lowered.

The residual monomer content in the acrylic pressure sensitive adhesive composition is preferably 2% by weight or less, particularly preferably 0.00001 to 1.5% by weight, more preferably 0.0001 to 1.0% by weight. If the amount of the residual monomer is too large, the molecular weight increases when heated, resulting in a decrease in coatability and adhesive property, or bubbles in the pressure-sensitive adhesive, resulting in a decrease in durability.

In the present invention, the content of volatile components in the acrylic pressure-sensitive adhesive composition (usually, the solvent and the remaining monomer is the main component) is preferably 2% by weight or less, particularly preferably 0.00001 to 1.5% by weight, and more preferably 0.0001 to 1.0% by weight. If the amount of the residual monomer is too large, the molecular weight of the acrylic resin (A) increases when heated, and the coating property is lowered, or when the acrylic resin (A) is used as a pressure-sensitive adhesive, the adhesive property tends to deteriorate or bubbles are generated and the durability tends to deteriorate.

The melt viscosity, solvent content, residual monomer content and volatile component content of the acrylic pressure-sensitive adhesive composition can be measured by the same method as in the acrylic resin (A).

The acrylic pressure sensitive adhesive composition of the present invention is useful as a hot melt pressure sensitive adhesive component. The pressure sensitive adhesive made of the acrylic pressure sensitive adhesive composition of the present invention is particularly useful as a solventless pressure sensitive adhesive for optical members.

<Adhesive sheet>

The acrylic pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition comprising a pressure-sensitive adhesive sheet provided on a base sheet, a pressure-sensitive adhesive layer provided on the substrate sheet, a pressure- Is preferably used.

In addition, the pressure sensitive adhesive layer may be one obtained by curing (crosslinking) the acrylic pressure sensitive adhesive composition of the present invention, even if it is the acrylic pressure sensitive adhesive composition itself of the present invention.

The curing method includes a method of curing with an active energy ray. By irradiating an active energy ray, the acrylic resin (A) in the acrylic pressure-sensitive adhesive composition forms a crosslinking structure in at least one of the molecule and the molecule.

The pressure-sensitive adhesive sheet can be produced, for example, as follows.

First, the acrylic pressure-sensitive adhesive composition is coated on one side or both sides of the base sheet in a state dissolved by heating and then cooled, or the acrylic pressure-sensitive adhesive composition is dissolved by heating and extruded onto a base sheet by a T die or the like A pressure-sensitive adhesive layer is formed on one surface or both surfaces of the base sheet so as to have a predetermined thickness. The pressure-sensitive adhesive sheet can be produced by attaching the release sheet to the pressure-sensitive adhesive layer side if necessary.

In addition, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer is formed on a base sheet, then subjected to active energy ray irradiation treatment as required, and aged again to cure (crosslink) the pressure-sensitive adhesive composition can be produced.

Further, a double-sided pressure-sensitive adhesive sheet without a substrate can be produced by forming a pressure-sensitive adhesive layer on a release sheet and attaching a release sheet to the pressure-sensitive adhesive layer side on the opposite side.

The pressure-sensitive adhesive sheet or double-sided pressure-sensitive adhesive sheet thus obtained is used for peeling off the release sheet from the pressure-sensitive adhesive layer in use.

Examples of the base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate and polyethylene terephthalate / isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene and polymethylpentene; Polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene and the like; polyamides such as nylon 6 and nylon 6,6; polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene- Vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, vinyl polymers such as polyvinyl alcohol and vinylon, cellulosic resins such as cellulose triacetate and cellophane, methyl polymethacrylate, ethyl polymethacrylate, ethyl polyacrylate, Of acrylic resin, polystyrene, polycarbonate, polyarylate May be a fabric or non-woven fabric made of a synthetic resin sheet such as polyimide, aluminum, copper, and the metal foil of the iron, the jilji, such as glassine paper, glass fibers, natural fibers, synthetic fibers and the like. These base sheets can be used as a single layer body or as a multi-layer body in which two or more kinds of layers are laminated. Of these, a synthetic resin sheet is preferable from the viewpoint of lightening and the like.

As the release sheet, for example, various synthetic resin sheets exemplified as the base sheet, a paper, a fabric, a nonwoven fabric or the like can be used. As the release sheet, it is preferable to use a silicone type release sheet.

The acrylic pressure-sensitive adhesive composition is not particularly limited as long as it is a general coating method, and examples thereof include roll coating, die coating, gravure coating, comma coating, slot coating and screen printing.

When irradiating with active energy ray, it is possible to use not only electromagnetic waves such as far ultraviolet ray, ultraviolet ray, near ultraviolet ray and infrared ray, electromagnetic waves such as X ray and? Ray but also electron ray, proton ray and neutron ray. It is advantageous to cure by irradiation with ultraviolet rays from the easiness of obtaining, the price and the like.

In the present invention, the optical member with a pressure-sensitive adhesive layer can be obtained by laminating the pressure-sensitive adhesive layer on the optical member. It is also possible to attach the optical members to each other using the double-sided pressure-sensitive adhesive sheet.

Examples of the optical member include a liquid crystal display, a transparent conductive film plate (ITO substrate), and a protective film (glass) constituting a touch panel or an image display device.

The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is preferably 10 to 100% by weight, particularly preferably 30 to 90% by weight, particularly preferably 50 to 80% by weight from the viewpoint of endurance performance and adhesive strength. When the gel fraction is too low, the cohesive force is lowered and the durability tends to be lowered. If the gel fraction is too high, the cohesive force tends to decrease due to the increase of the cohesive force.

When a pressure-sensitive adhesive layer is formed by curing with an active energy ray, it is preferable from the viewpoint of economical efficiency and processability that the gel fraction increases at a low irradiation dose. Specifically, the gel fraction is preferably 10 to 90% by weight, particularly preferably 30 to 85% by weight, and more preferably 50 to 80% by weight, at an integrated light quantity of 1000 mJ / When the gel fraction at a low irradiation dose is too low, a large amount of active energy dose is required until the adhesive layer is formed, so that efficient production tends to be difficult. On the other hand, in the case of using an adhesive sheet with a low gel fraction due to economical efficiency, the workability of the adhesive sheet tends to be lowered.

When the gel fraction is adjusted to the above range, for example, the active energy ray irradiation amount or the content of the active energy ray crosslinkable structural moiety in the acrylic resin (A) may be adjusted, or the amount of photoinitiator, the kind of active energy ray- Is achieved by adjusting the amount.

The gel fraction is a standard for the degree of crosslinking (degree of curing) and is calculated, for example, by the following method. That is, an adhesive sheet (not provided with a release sheet) having a pressure-sensitive adhesive layer formed on a base polymer sheet (for example, a polyethylene terephthalate (PET) film or the like)) was wrapped with a 200 mesh SUS wire netting, Deg.] C for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the wire net is determined as the gel fraction. However, the weight of the base material shall be omitted.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is usually preferably from 50 to 3000 占 퐉, more preferably from 100 to 1000 占 퐉, and particularly preferably from 175 to 350 占 퐉. If the thickness of the pressure-sensitive adhesive layer is too small, the impact absorbability tends to decrease. If the pressure-sensitive adhesive layer is too thick, the thickness of the entire optical member tends to be increased, and practicality tends to decrease.

The thickness of the pressure-sensitive adhesive layer in the present invention was measured using the "ID-C112B" manufactured by Mitsutoyo Co., Ltd., and the measured value of the thickness of the constituent members other than the pressure- Min.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention preferably has a haze value of 2% or less, particularly 0 to 1.5% or 0 to 1% when the thickness of the pressure-sensitive adhesive layer is 175 m. %, The pressure-sensitive adhesive layer is whitened and transparency tends to be lowered.

The pressure-sensitive adhesive layer of the present invention preferably has a relative dielectric constant at 100 Hz of 3.5 or less, more preferably 3.0 or less. The lower limit value of the relative permittivity is usually 1.0.

If the relative permittivity is too high, the electrostatic capacitance between the electrodes mounted on the touch panel tends to increase, causing a malfunction. If the relative permittivity is too low, the capacitance tends to decrease and the detection sensitivity tends to decrease.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In the examples, &quot; part &quot; and &quot;% &quot; mean weight basis excluding the haze value. The measurement of the weight average molecular weight of the acrylic resin was carried out in accordance with the aforementioned method.

[Production Example 1]

Azobis (2,4-dimethylvaleronitrile) (ADVN: 10-hour half-life temperature 52 占 폚) serving as a polymerization initiator was added to a 2 L flask with a condenser as a polymerization solvent at a boiling point of 56 占 폚 , 50 parts of stearyl methacrylate (SMA: a2-1) (15% of the entire copolymerization component), a mixture of lauryl methacrylate and tridecyl methacrylate (SLMA: a2- Methacrylate (2EHMA: a2-2) (with respect to the entire copolymerization component: 15%), 4-hydroxybutyl acrylate (4 HBA : A1) was mixed with 20 parts of 40 parts (12% of all of the copolymerization components) and 1.5 parts of 4-methacryloyloxybenzophenone (MBP: a3) And the remaining 80% of the above-mentioned monomer solution was added dropwise over 2 hours. After 1 hour and 3 hours after the dropwise addition, 0.2 parts of ADVN and 0.6 parts of each were added and reacted to obtain an acrylic resin [A-1] solution.

The solution of the acrylic resin [A-1] obtained above was subjected to pressure reduction to a pressure of 10 kPa at a jacket temperature of 80 ° C for one hour in a flask in which a solvent was removed by using a T- The solvent was removed to obtain an acrylic resin [A-1] (weight average molecular weight: 33.9 million, volatile content: 0.9%, glass transition temperature-8.9 ° C).

[Production Example 2, Comparative Production Examples 1 and 2]

Acrylic resin [A-2], [A'-1] and [A'-2] were prepared in the same manner as in Production Example 1 except that the copolymerization components of the acrylic resin were changed to those in Table 1.

&Lt; Example 1 &gt;

The acrylic resin [A-1] obtained above was sandwiched between two polyester type release sheets (176 탆 in thickness), pressed while heating at 100 캜 so that the thickness of the adhesive layer was 175 탆, Was irradiated with ultraviolet light at a peak illuminance of 150 mW / cm 2 and an integrated exposure dose of 1,000 mJ / cm 2 (500 mJ / cm 2 × 2 passes) to obtain a substrate-less double-faced pressure-sensitive adhesive sheet.

Further, the release sheet on one side was peeled off from the pressure-sensitive adhesive layer of the substrate-less pressure sensitive adhesive sheet obtained above and pressed against a polyethylene terephthalate (PET) film (thickness: 125 탆) A PET film with a pressure-sensitive adhesive layer was obtained.

&Lt; Example 2 &gt;

Sensitive adhesive sheet of Example 2 and a PET film with a pressure-sensitive adhesive layer were prepared in the same manner as in Example 1 except that the acrylic resin [A-1] was changed to the acrylic resin [A- &Lt; / RTI &gt;

&Lt; Comparative Example 1 &

Sensitive adhesive sheet of Comparative Example 1 and a PET sheet with a pressure-sensitive adhesive layer were prepared in the same manner as in Example 1 except that the acrylic resin [A-1] was changed to the acrylic resin [A'-1] A film was obtained.

&Lt; Comparative Example 2 &

Sensitive adhesive sheet of Comparative Example 2 and a PET film with a pressure-sensitive adhesive layer in the same manner as in Example 1 except that the acrylic resin [A-1] was changed to the acrylic resin [A'-2] &Lt; / RTI &gt;

[Gel fraction (1)]

The substrateless double-faced pressure-sensitive adhesive sheet was cut into 40 mm x 40 mm and left for 30 minutes under conditions of 23 deg. C x 50% RH. One of the release sheets was peeled off and the side of the pressure sensitive adhesive layer was covered with a 50 mm x 100 mm SUS mesh sheet ), Peeling the other release sheet again, folding the SUS mesh sheet at the central portion in the longitudinal direction to wrap the sample, and immersing the sample in a sealed container containing 250 g of toluene kept at 23 DEG C for 24 hours And the gel fraction (%) was measured at the weight change.

[Gel fraction (2)]

The substrateless double-faced pressure-sensitive adhesive sheet was cut into a size of 40 mm x 40 mm and irradiated with ultraviolet rays at a peak illuminance of 150 mW / cm 2 and an integrated exposure dose of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 passes) And the pressure-sensitive adhesive layer side was stuck to a SUS mesh sheet (200 mesh) of 50 mm x 100 mm. Thereafter, one of the release sheets was peeled off, and the pressure-sensitive adhesive layer side was peeled off by SUS mesh The gel fraction (%) was measured at a change in weight when the sample was folded at the central portion in the longitudinal direction of the sheet and then immersed in a sealed container containing 250 g of toluene kept at 23 DEG C for 24 hours.

〔adhesiveness〕

The PET film with the pressure-sensitive adhesive layer was cut into a width of 25 mm and a length of 100 mm. The release sheet was peeled off and the side of the pressure-sensitive adhesive layer was immersed in an alkali-free glass ("Eagle XG" Under the conditions of a pressure of 50 kg / cm &lt; 2 &gt; and a pressure of 20 kg / cm &lt; 2 &gt; for 20 minutes under the conditions of a peak illuminance of 150 mW / The substrate was irradiated with ultraviolet rays at 2000 mJ / cm 2 (1000 mJ / cm 2 × 2 passes) and allowed to stand for 30 minutes under the conditions of 23 ° C. × 50% RH. Subsequently, 180 ° peel strength N / 25 mm) was measured.

[Optical properties of pressure-sensitive adhesive layer]

The base materialless double-faced pressure-sensitive adhesive sheet was cut into a size of 25 mm x 25 mm and irradiated with ultraviolet rays at a peak illuminance of 150 mW / cm 2 and an integrated exposure dose of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 passes) in a high-pressure mercury UV irradiator. Thereafter, the releasable sheet on one side was peeled from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive side was stuck to an alkali-free glass ("Eagle XG" manufactured by Corning Incorporated, thickness 1.1 mm) and autoclave treatment (50 ° C × 0.5 MPa × 20 minutes ), And left for 30 minutes under conditions of 23 캜 x 50% RH. Finally, one release sheet was peeled off again, and a test piece having the constitution of "alkali-free glass / pressure-sensitive adhesive layer" was produced.

The haze value, total light transmittance, color difference b ^* value, and YI value were measured using the obtained test pieces.

[Haze value and total light transmittance]

The haze value was determined by measuring the diffuse transmittance and the total light transmittance using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.), and calculating the haze value by substituting the values of the obtained diffuse transmittance and total light transmittance into the following formula. In addition, this machine conforms to JIS K7361-1.

Haze value (%) = (diffuse transmittance / total light transmittance) x 100

[Color difference]

The color difference b ^* value was measured in accordance with JIS K 7105, and the measurement was carried out under a transmission condition using a spectral colorimeter (SE6000: manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[YI value]

The YI value was measured in accordance with JIS K 7373, and the measurement was carried out under a transmission condition using a spectral colorimeter (SE6000: manufactured by Nippon Denshoku Kogyo Co., Ltd.).

The haze, total light transmittance, color difference b * value and YI value in the examples were measured by adhering only the pressure sensitive adhesive layer to an alkali-free glass (total light transmittance = 93%, haze = 0.06%, b * value = 0.16) .

[Humidity Resistance]

The PET film with the pressure-sensitive adhesive layer was cut into a size of 30 mm x 50 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer side was stuck to an alkali-free glass (Eagle XG manufactured by Corning Incorporated, The film was irradiated with ultraviolet rays at a peak illuminance of 150 mW / cm 2 and an integrated exposure dose of 2000 mJ / cm 2 (1000 mJ / cm 2 × 2 passes) in a high-pressure mercury UV irradiator from the PET film side, × 50% RH for 30 minutes to prepare a test piece having the constitution of "alkali-free glass / pressure-sensitive adhesive layer / PET film".

The obtained test pieces were subjected to a humidity resistance thermostability test for 168 hours under an atmosphere of 60 DEG C x 90% RH, and the haze value before the initiation of the humid heat resistance test and the humidity resistance thermostability test were measured and evaluated according to the following criteria. The haze value was measured by the same method as the measurement of optical properties of the pressure-sensitive adhesive layer.

(evaluation)

○: The haze value after the humid heat resistance test is less than 2.0% and the rising rate of the haze value before and after the humid heat resistance test is not more than 20%

The haze value immediately after the humid heat resistance test is less than 2.0%, and the rising ratio of the haze value before and after the humid heat resistance test is greater than 20%.

X: Haze value immediately after the wet heat stability test is 2.0% or more

The rate of increase (%) of the haze value before and after the humid heat resistance test is obtained by the following formula.

Growth rate (%) = (Haze value after test - Haze value before test) / Haze value before test × 100

[Thermal Stability]

The base materialless double-faced pressure-sensitive adhesive sheet was cut into a size of 30 mm x 50 mm and subjected to ultraviolet irradiation at a peak illuminance of 150 mW / cm 2 and an integrated exposure dose of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 passes) in a high-pressure mercury UV irradiator. Thereafter, the release sheet on one side was peeled from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive side was stuck to the non-alkali glass ("Eagle XG" manufactured by Corning Inc., thickness 1.1 mm) An alkali glass (manufactured by Corning Incorporated, Eagle XG) was stuck together and subjected to an autoclave treatment (50 DEG C x 0.5 MPa x 20 minutes) to prepare a test piece having the constitution of "alkali-free glass / adhesive layer / alkali-free glass".

The obtained test piece was subjected to a thermal stability test for 168 hours under an atmosphere of 150 캜, and the b ^* value after the thermal stability test was measured. The b ^* value was measured by the same method as the measurement of the optical property of the pressure-sensitive adhesive layer.

(evaluation)

○ ... b ^* value immediately after the thermal stability test is not more than 0.5

X: b ^* value immediately after the thermal stability test is greater than 0.5

[Specific dielectric constant]

The release sheet on one side was peeled off from the pressure-sensitive adhesive layer of the substrateless double-side adhesive sheet and pressed against the untreated PET film (thickness: 50 mu m), and then one release sheet was peeled off and pressed onto the untreated PET film as described above, PET film / pressure-sensitive adhesive layer / PET film &quot;.

The PET film with the pressure-sensitive adhesive layer was cut into a piece of 7 cm x 7 cm and irradiated with ultraviolet rays at a peak illuminance of 150 mW / cm 2 and an integrated exposure amount of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 passes) in a high-pressure mercury UV irradiator.

The electric capacity of the test piece for dielectric constant measurement was measured by applying an electric field at a frequency of 100 Hz between the electrodes under an atmosphere of 23 占 폚 and 50% RH using HP4284A PASSIJON LCR meter (manufactured by Agilent) The dielectric constant of the pressure-sensitive adhesive layer was calculated from the change in electric capacity between the electrodes. Thereafter, the dielectric constant was calculated from the obtained dielectric constant.

(evaluation)

The adhesive layer has a relative dielectric constant of 3.0 or less at 100 KHz

X: The relative dielectric constant of the adhesive layer at 100 KHz is larger than 3.0

The pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition of Examples 1 and 2 was low in dielectric property and excellent in heat stability and wet heat resistance. On the other hand, in Comparative Example 1 in which the content of the hydroxyl group-containing (meth) acrylic ester monomer (a1) was small, the heat resistance was poor. In Comparative Example 2 in which the content of the linear (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group of 10 to 24 carbon atoms was small, the thermal stability was poor and the relative dielectric constant was high.

Although the embodiment has been described in the concrete form of the present invention, the embodiment is merely an example and is not to be construed as limiting. Various modifications that are obvious to those skilled in the art are expected to be within the scope of the present invention.

The acrylic pressure-sensitive adhesive composition of the present invention is capable of coating a thick coating, and the pressure-sensitive adhesive made by using the pressure-sensitive adhesive composition of the present invention is excellent in thermal stability without yellowing of the resin by heating, exhibits low dielectric constant, It is particularly useful as a pressure-sensitive adhesive to be used for sticking an optical member constituting a touch panel, an image display device, etc., and for use in an organic EL display bag.

Claims (10)

A pressure-sensitive adhesive composition comprising an acrylic resin (A) which is a copolymer of a copolymerizable component containing a hydroxyl group-containing (meth) acrylic ester monomer (a1) and a (meth) acrylic acid alkyl ester monomer (a2)
Wherein the (meth) acrylic acid alkyl ester monomer (a2) comprises a (meth) acrylic acid alkyl ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms,
(Meth) acrylic acid ester monomer (a2-1) having a straight chain alkyl group having 10 to 24 carbon atoms in an amount of 50 to 94% by weight, the copolymerization component containing 5 to 15% by weight of a hydroxyl group-containing (meth) Based on the weight of the acrylic pressure-sensitive adhesive composition. The method according to claim 1,
Wherein the copolymerization component further comprises 0.1 to 20% by weight of a methacrylic acid alkyl ester monomer (a2-2) having an alkyl group having 4 to 8 carbon atoms as the (meth) acrylic acid alkyl ester monomer (a2) . The method according to claim 1 or 2,
(Meth) acrylic acid alkyl ester monomer having a straight chain alkyl group and a (meth) acrylic acid alkyl ester monomer having a branched chain containing alkyl group in the (meth) acrylic acid alkyl ester monomer (a2) 0 to 70/30. 4. The method according to any one of claims 1 to 3,
Wherein the acrylic resin (A) has a weight average molecular weight of 150,000 to 150,000. 5. The method according to any one of claims 1 to 4,
Wherein the acrylic resin (A) has an active energy ray-crosslinkable structural moiety. The method of claim 5,
Wherein the active energy ray-crosslinkable structure moiety is a benzophenone-based crosslinked structure. 7. The method according to any one of claims 1 to 6,
Wherein the content of volatile components in the acrylic resin (A) is 2% by weight or less. A pressure-sensitive adhesive comprising the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 7. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 7. The method of claim 9,
Wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by curing the acrylic pressure-sensitive adhesive composition with an active energy ray.