KR101866438B1 - Adhesive composition - Google Patents

Abstract

More particularly, the present invention relates to an acrylic copolymer comprising a monomer and a monomer having a hydroxyl group: a carbodiimide crosslinking agent; And an isocyanate-based crosslinking agent, the present invention relates to a pressure-sensitive adhesive composition having a crosslinking base point increased, a curing speed is improved, stress is enhanced, light leakage phenomenon is improved, and adhesion is low and adhesive durability is excellent even under severe conditions (high temperature and humidity).

Description

[0001] ADHESIVE COMPOSITION [0002]

The present invention relates to a pressure-sensitive adhesive composition which is excellent in low-tackiness and adhesive durability, and which simultaneously has a high curing speed.

As the size of the image display device has been increased, another property improvement is required for the pressure-sensitive adhesive used for its manufacture.

For example, a liquid crystal monitor is manufactured by sequentially laminating a liquid crystal panel, a polarizing plate, a protective film, and the like with a pressure-sensitive adhesive layer interposed therebetween, but the arrangement of the respective members may be adjusted in the case of positioning or the like. At this time, there may be a case where it is necessary to peel off the laminated members once again and to attach them again (i.e., to bond them).

Exemplary Display Unless specifically, the operation of peeling the polarizing plate bonded to the liquid crystal panel from the liquid crystal panel requires a larger force as the display is enlarged, which may lower the productivity and workability. In addition, there is a possibility that the cell gap of the liquid crystal panel is changed in accordance with the stress when the bonded member is peeled off.

Accordingly, the pressure-sensitive adhesive is required to have a lower workability than the conventional one so that the pressure-sensitive adhesive does not remain after peeling, and at the same time, the members of the large display can be easily peeled off.

A related art related to this is Japanese Patent Application Laid-Open No. 2008-176173. This technique is a pressure-sensitive adhesive composition comprising an acrylic resin, an isocyanate compound, an aziridine compound and a silicone oligomer. However, since the aziridine compound is toxic and harmful to human body, it is required to avoid use in terms of workability and stability. In addition, there is a disadvantage in that it can not exhibit low adhesiveness simultaneously with reworkability.

Further, the optical film used in the image display apparatus, particularly the polarizing plate, has a large dimensional change of the film due to environmental changes. Therefore, when a pressure-sensitive adhesive such as a label or double-sided tape is used, defects such as foaming or peeling are likely to occur in an environment of high temperature and high humidity. In Japanese Patent Laid-Open No. 2008-176173, the molecular weight of the resin as the main component of the pressure-sensitive adhesive is increased to improve durability reliability. However, when the resin has a high molecular weight, the solid content of the pressure-sensitive adhesive solution is small and the productivity is lowered.

Japanese Unexamined Patent Application Publication No. S57-195208 in which a silane coupling agent is added to the pressure-sensitive adhesive in order to improve the endurance reliability is known. However, although the durability is improved by the combination of the following silane coupling agents, there is a disadvantage in that low adhesion is not realized due to strong adhesion to the glass surface.

It is an object of the present invention to provide a pressure-sensitive adhesive composition which not only exhibits low durability and high durability even under severe conditions (high temperature and high humidity), but also has a high curing speed.

In order to achieve the above object, the present invention provides an acrylic copolymer comprising a monomer having the following Formula 1 and a monomer having a hydroxyl group: a carbodiimide crosslinking agent; And an isocyanate-based crosslinking agent.

또는

이고, n은 1 내지 10의 정수이며, X는 산소원자 또는 -NH임).(Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms,

or

, N is an integer of 1 to 10, and X is an oxygen atom or -NH.

Preferably, R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms, and X may be an oxygen atom.

The carbodiimide crosslinking agent may be a diisocyanate having two or more carbodiimide groups in the molecule.

The monomer having a hydroxyl group may be a hydroxyalkyl (meth) acrylate, a hydroxyalkylene glycol (meth) acrylate, or a mixture thereof.

0.01 to 5 parts by weight of a carbodiimide crosslinking agent and 0.01 to 5 parts by weight of an isocyanate crosslinking agent relative to 100 parts by weight of the acrylic copolymer.

The acrylic copolymer may contain a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms, a monomer of the formula (1), and a monomer having a hydroxyl group.

The acrylic copolymer may contain 100 parts by weight of a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms, 0.01-5 parts by weight of a monomer of the formula (1), and 0.01-10 parts by weight of a monomer having a hydroxyl group.

The pressure-sensitive adhesive composition of the present invention is composed of a specific crosslinking agent and has an advantage of improving the light leakage phenomenon because the crosslinking base point is increased and the curing speed is fast and the stress is strengthened.

Further, the pressure-sensitive adhesive composition of the present invention is advantageous in that it has low stickiness and excellent durability in adhesion even under severe conditions (high temperature and high humidity).

The present invention relates to a pressure-sensitive adhesive composition which is excellent in low-tackiness and adhesive durability, and which simultaneously has a high curing speed.

Hereinafter, the present invention will be described in detail.

The pressure-sensitive adhesive composition of the present invention is an acrylic copolymer comprising a monomer having the following formula (1) and a monomer having a hydroxyl group: a carbodiimide crosslinking agent; And an isocyanate-based crosslinking agent.

[Chemical Formula 1]

또는

이고, n은 1 내지 10의 정수이며, X는 산소원자 또는 -NH임).(Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms,

or

, N is an integer of 1 to 10, and X is an oxygen atom or -NH.

In the acrylic copolymer, the carboxyl group and the carbodiimide crosslinking agent of the above formula (1), and the hydroxy group of the monomer having a hydroxyl group and the isocyanate crosslinking agent function as crosslinking points, respectively. That is, the acrylic copolymer according to the present invention has an effect of improving the durability because the crosslinking base point is increased and the cohesive force is strengthened as compared with the conventional acrylic copolymer. In addition, the monomer of Formula 1 has an advantage that the curing speed is fast because the monomer chain is long in addition to the crosslinking point of the carboxyl group.

R ₁ in Formula 1 is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms, and X may be an oxygen atom.

The monomer having a hydroxyl group may be at least one selected from the group consisting of hydroxyalkyl (meth) acrylate, hydroxyalkylene glycol (meth) acrylate and hydroxyalkyl acrylamide.

(Meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl Hydroxypropyl (meth) acrylate, 2-hydroxypropyleneglycol (meth) acrylate, 2-hydroxyethyl (meth) acrylamide, Acrylamide, 4-hydroxybutyl (meth) acrylamide and 6-hydroxyhexyl (meth) acrylamide can be used. Preferably, 2-hydroxyethyl (meth) acrylate or 2-hydroxyethyl (meth) acrylamide is preferred.

The acrylic copolymer of the present invention includes a (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms, a monomer having the formula (1), and a monomer having a hydroxyl group.

Here, (meth) acrylate means acrylate and methacrylate.

Butyl (meth) acrylate, 2-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (Meth) acrylate, nonyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate and lauryl (meth) acrylate. Of these, n-butyl acrylate, Mixtures of these are preferred. These may be used alone or in combination of two or more.

It is preferable that the monomer of Formula 1 contains 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms. If the content is less than 0.01 part by weight, the cohesive force synergistic effect is insignificant. If the content is more than 5 parts by weight, the cohesive strength is too high, and the durability may be lowered.

The monomer having a hydroxyl group is preferably contained in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms. When the content is less than 0.01 part by weight, the crosslinking degree is low and the adhesive strength is high, so that defects may occur during reworking. When the content is more than 10 parts by weight, adhesiveness may be lowered due to high degree of crosslinking and durability problems may occur.

In the acrylic copolymer of the present invention, other polymerizable monomers other than the above monomers may be added in an amount not lowering the adhesive force, for example, 10 parts by weight or less based on 100 parts by weight of the (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms . ≪ / RTI >

The method for producing the copolymer is not particularly limited and can be produced by methods such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, which are commonly used in the art, and solution polymerization is preferable. In addition, a solvent, a polymerization initiator, a chain transfer agent for molecular weight control and the like which are usually used in polymerization can be used.

The present invention is characterized by a pressure-sensitive adhesive composition containing the acrylic copolymer and two specific crosslinking agents.

The crosslinking agent can improve the adhesion and durability, and can maintain the reliability at a high temperature and the shape of the pressure-sensitive adhesive.

The present invention uses a carbodiimide crosslinking agent and an isocyanate crosslinking agent capable of performing a crosslinking reaction smoothly with each monomer contained in the acrylic copolymer.

The carbodiimide-based crosslinking agent is not particularly limited and is generally used in the art, and specifically, a compound having two or more carbodiimide groups (-N═C═N-) in the molecule is preferable, A bidentimide compound can be used. Particularly, a diisocyanate compound having two or more carbodiimide groups in the molecule is preferable.

The carbodiimide compound may also be a high molecular weight polycarbodiimide produced by a decarboxylic acid condensation reaction of a diisocyanate in the presence of a carbodiimidization catalyst. Examples of such compounds include those obtained by condensation reaction of the following diisocyanates by decarboxylation.

Examples of the diisocyanate include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-di Phenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6- At least one selected from the group consisting of diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and tetramethyl xylylene diisocyanate is used .

Examples of the carbodiimidation catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, , 1-ethyl-2-phosphorene-1-oxide, or their 3-phosphorene isomers.

Such high molecular weight polycarbodiimides may be synthesized or commercially available products may be used. Commercially available products include CARBODILITE (registered trademark) series of Nisshinbo Chemical Inc., for example. Among them, Kabodite (registered trademark) V-01, V-03, V-05, V-07 and V-09 are preferable because of their excellent compatibility with organic solvents. Particularly preferred are carbodite (registered trademark) V-01, V-05, and V-07.

The carbodiimide crosslinking agent may contain 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 1 part by weight based on 100 parts by weight of the acrylic copolymer. If the content is less than 0.01 part by weight, the effect of strengthening the cohesive force may be insufficient due to insufficient crosslinking point. If the content exceeds 5 parts by weight, durability may be deteriorated due to excessive crosslinking reaction.

The isocyanate crosslinking agent may be hydroxyalkyl (meth) acrylate, hydroxyalkylene glycol (meth) acrylate, or a mixture thereof. Specifically, diisocyanate compounds such as tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 2,4- or 4,4-diphenylmethane diisocyanate, and the like; And adducts of polyhydric alcohol compounds such as trimethylolpropane of diisocyanate.

In addition to the isocyanate crosslinking agent, melamine derivatives such as hexamethylol melamine, hexamethoxymethyl melamine, hexabutoxymethyl melamine and the like; Polyepoxy compounds, for example, bisphenol A and epichlorohydrin condensate type epoxy compounds; At least one crosslinking agent selected from the group consisting of polyglycidyl ether of polyoxyalkylene polyol, glycerin di- or triglycidyl ether, and tetraglycidyl xylenediamine may be further added and used together.

Such an isocyanate crosslinking agent may be contained in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer. When the content is less than 0.01 part by weight, the crosslinking degree is insufficient and the cohesive force is reduced, so that the physical properties such as durability and cutability may be deteriorated. When the content is more than 5 parts by weight, excessive crosslinking reaction may cause residual stress.

The pressure-sensitive adhesive composition of the present invention may further contain additives such as a tackifier resin, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, a defoaming agent, A filler, a light stabilizer, an antistatic agent, a silane coupling agent, and the like. In this case, the silane coupling agent is preferably used in the form of a monomer, and the oligomer form may lower the adhesive force because of low adhesiveness between the adhesive and the adherend, so that the use thereof is preferably limited.

The pressure-sensitive adhesive composition of the present invention can be used as a pressure-sensitive adhesive for a polarizing plate or a pressure-sensitive adhesive for a surface protective film for bonding with a liquid crystal cell. In addition, it can be used not only as a protective film, a reflective sheet, a structural adhesive sheet, a photographic adhesive sheet, a lane marking adhesive sheet, an optical adhesive product, an electronic component adhesive, but also a general commercial adhesive sheet product or a medical patch.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example  1-9 and Comparative Example  1-5

1) Preparation of acrylic copolymer

A monomer mixture having the composition shown in the following Table 1 was put in a 1 L reactor equipped with a cooling device for regulating the temperature of the nitrogen gas and refluxing, and 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for one hour to maintain oxygen at 72 < 0 > C to remove oxygen. After the mixture was homogeneously mixed, 0.05 parts by weight of azobisisobutyronitrile (AIBN) as a reaction initiator was added and reacted for 8 hours to prepare an acrylic copolymer.

2) Preparation of pressure-sensitive adhesive composition

The acrylic copolymer prepared in 1) above was mixed in the composition shown in the following Table 1 and diluted to a concentration of 28% by weight in consideration of coating property to prepare a pressure-sensitive adhesive composition.

division
(Parts by weight) Acrylic copolymer (% by weight) Cross-linking agent Silane coupling agent Acrylate monomer Formula 1 Monomer having a hydroxyl group Polymerizable
Monomer Carbodiimide system Isocyanate system KBM-403 X-41-1053 2-CEA A-SA 6-44HA 2-HEA 2-HEAA Example 1 98.5 0.5 - - One - - 0.2 0.5 - - Example 2 98.9 0.1 - - One - - 0.2 0.5 - - Example 3 98 One - - One - - 0.2 0.5 - - Example 4 89 10 - - One - - 0.2 0.5 - - Example 5 98.5 - 0.5 - One - - 0.2 0.5 - - Example 6 98.5 - - 0.5 One - - 0.2 0.5 - - Example 7 98.5 0.5 - - - One - 0.2 0.5 - - Example 8 98.5 0.5 - - One - - 0.5 0.5 - - Example 9 98.5 0.5 - - One - - 0.2 0.5 0.5 - Comparative Example 1 98.5 0.5 - - One - - 0.7 - - - Comparative Example 2 98.5 0.5 - - One - - - 0.7 - - Comparative Example 3 98.5 - - - One - 0.5 0.2 0.5 - - Comparative Example 4 98.5 0.5 - - One - - 0.7 - - 0.5 Comparative Example 5 98.5 0.5 - - One - - - 0.7 - 0.5 Acrylate monomer: butyl acrylate
2-CEA: 2-carboxyethyl acrylate (Aldrich)
A-SA:? -Acryloyloxyethylhydrogen succinate (Shin Nakamura)
6-44HA: 6-acrylamidohexanolic acid (TCI)
2-HEA: 2-hydroxyethyl acrylate (Aldrich)
2-HEAA: 2-hydroxyethylacrylamide (Aldrich)
Polymerizable monomer: acrylic acid (Aldrich)
Carbodiimide based crosslinking agent: Carbodilite V-07 product (Nisshin Bosa)
Isocyanate-based crosslinking agent: Coronate-L product (Nihon Polyurethane Coating Co., Ltd.)
KBM-403 (Shin-Etsu)
X-41-1053 (Shin-Etsu)
The content of the crosslinking agent and the silane coupling agent is in the range of 100 parts by weight per 100 parts by weight of the acrylic copolymer

3) Polarizer with adhesive

2) was cured on a releasing film coated with a silicone release agent to a thickness of 25 占 퐉 and dried at 100 占 폚 for 1 minute to form an adhesive layer.

The pressure-sensitive adhesive layer prepared above was laminated on an iodine-based polarizing plate having a thickness of 185 탆 by pressure-sensitive adhesive processing to produce a polarizer with a pressure-sensitive adhesive. The prepared polarizing plate was stored for a curing period under the conditions of 23 캜 and 60% RH.

Test Example

The properties of the pressure-sensitive adhesive composition and the polarizer with a pressure-sensitive adhesive prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 2 below.

One. Light beam  phenomenon

The prepared polarizer with a pressure-sensitive adhesive was adjusted to a size of 233 mm 309 mm using a cutting device (Super Cutter, PN1-600 manufactured by Ozone Systems Co., Ltd.). Thereafter, the releasing film was peeled off, and the exposed pressure-sensitive adhesive layer was laminated (laminated) to a non-alkali glass (Eagle XG manufactured by Corning). The pressure-sensitive adhesive layer was pressed in an autoclave of Kurihara Seisakusho Co., Respectively.

The bonding was performed so that the polarization axis of the polarizing plate with a pressure-sensitive adhesive was in the cross-Nicol state (polarizing axis: angle 0 deg., Angle 90 deg.) On the surface of the alkali-free glass. After leaving for 500 hours under the drying condition at 80 캜 in this state, the light leakage phenomenon was evaluated by the following method.

The light leakage phenomenon was evaluated by measuring the brightness of each area shown in the following figure using MCPD-2000 manufactured by Otsuka Denshi and calculating the brightness difference (DELTA L *) by the following equation.

A, b, C, d and e are brightness values of measurement points (one central portion of each region) predetermined in the A region, B region, C region, D region and E region.

At this time, as the value of DELTA L * is smaller, light leakage does not occur and light leakage does not occur.

2. Durability (heat resistance / Wet heat )

The polarizing plate with a pressure-sensitive adhesive was cut into a size of 90 mm x 170 mm and the release film was peeled off. The polarizing plate was attached to both sides of a glass substrate (110 mm x 190 mm x 0.7 mm) such that the absorption axes of the respective polarizing plates were orthogonal. At this time, the applied pressure was 5 kg / cm 2, and the clean room work was performed so as to prevent bubbles or foreign matter from being produced, thereby preparing the test piece.

The heat resistance of the specimen was measured at a temperature of 80 ° C for 1000 hours, and then the occurrence of bubbles or peeling was observed. The specimens were allowed to stand at room temperature for 24 hours immediately before evaluating the state of the specimens. The moisture resistance characteristics of the specimens were observed under the condition of temperature of 60 ° C and humidity of 90% RH for 1000 hours, and then bubble or peeling was observed.

<Evaluation Criteria>

No bubble or peeling: ⓞ

Less than 5 bubbles or peeling: ○

Bubbles or exfoliation Less than 5: Less than 10

10 or more bubbles or peeling: x

3. Gel fraction (%)

The prepared polarizer with a pressure-sensitive adhesive was cured at 23 DEG C and 65% RH for 2 days. Approximately 0.25 g of the pressure-sensitive adhesive layer of the polarizing plate with a pressure-sensitive adhesive is stuck to a wire mesh (100 mm x 100 mm) of a 250 mesh precisely weighed, and the gel is wrapped so as not to leak. After accurately weighing the weight with a precision balance, the wire net is immersed in the ethyl acetate solution for 3 days. The immersed wire mesh is taken out, washed with a small amount of ethyl acetate solution, dried at 120 ° C for 24 hours and then weighed. Using the measured weight, the gel fraction was calculated by the following equation (2).

B is the weight of the wire netting attached to the pressure-sensitive adhesive layer (BA: weight of the pressure-sensitive adhesive, g); C is the weight of the wire netted after immersion (CA: weight of the gelled resin, g )being].

4. Adhesion

The prepared polarizer with a pressure-sensitive adhesive was cut into a size of 25 mm x 100 mm and the release film was peeled off. The release film was laminated to a glass substrate (# 1737, Corning) at a pressure of 0.25 MPa and autoclaved to prepare a specimen. The prepared specimens were allowed to stand under the conditions of 23 ° C and 50% RH for 24 hours, and the pressure-sensitive adhesive layer was peeled off at a peeling speed of 10 mm / min and a peeling angle of 180 ° using a universal tensile tester (UTM, Instron). At this time, measurement was carried out under conditions of 23 캜 and 50% RH.

division Light leakage phenomenon durability Gel fraction
(%) Adhesion
N / 25mm Heat resistance Wet heat Example 1 0.7 ◎ ◎ 73.5 2.3 Example 2 1.1 ◎ ○ 70.3 2.9 Example 3 1.4 ◎ ○ 75.6 2.1 Example 4 1.7 ○ ○ 80.1 1.8 Example 5 1.5 ○ ◎ 75.1 2.0 Example 6 1.1 ○ ◎ 74.6 2.5 Example 7 1.5 ◎ ○ 77.5 2.1 Example 8 1.0 ○ ○ 76.4 2.2 Example 9 1.2 ◎ ◎ 73.1 1.9 Comparative Example 1 3.5 × × 23.0 10.3 Comparative Example 2 3.3 × △ 32.3 10.8 Comparative Example 3 3.7 △ △ 52.1 9.5 Comparative Example 4 3.9 × × 31.5 11.5 Comparative Example 5 3.3 × × 51.7 9.7

As shown in Table 2, the pressure-sensitive adhesives of Examples 1 to 9, which were prepared by using the carbodiimide-based crosslinking agent and the isocyanate-based crosslinking agent according to the present invention in combination and using an acrylic copolymer containing an acrylate- It was confirmed that the composition had low adhesion and excellent durability under high temperature and high humidity conditions as compared with Comparative Examples 1 to 5, as well as improved light leakage.

In addition, it was confirmed that the cross-linking agent increased the cross-linking base point and the curing speed became faster.

In particular, it was confirmed that Comparative Examples 4 and 5 had problems in terms of durability and adhesiveness by using a carbodiimide type crosslinking agent or an isocyanate type crosslinking agent and an oligomer type silane coupling agent.

Claims (7)

An acrylic copolymer comprising a monomer having the following formula (1) and a monomer having a hydroxyl group:
Carbodiimide-based crosslinking agents; And
An isocyanate-based crosslinking agent,
0.01 to 5 parts by weight of a carbodiimide crosslinking agent and 0.01 to 5 parts by weight of an isocyanate crosslinking agent based on 100 parts by weight of the acrylic copolymer;
[Chemical Formula 1]

(Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms,

or

, N is an integer of 1 to 10, and X is an oxygen atom or -NH.
The pressure-sensitive adhesive composition according to claim 1, wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 2 to 6 carbon atoms, and X is an oxygen atom.
The pressure-sensitive adhesive composition according to claim 1, wherein the carbodiimide-based crosslinking agent is a diisocyanate having at least two carbodiimide groups in the molecule.
The pressure-sensitive adhesive composition according to claim 1, wherein the monomer having a hydroxyl group is at least one selected from the group consisting of hydroxyalkyl (meth) acrylate, hydroxyalkylene glycol (meth) acrylate and hydroxyalkyl acrylamide.
delete The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer contains a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms, a monomer of the formula (1), and a monomer having a hydroxyl group.
The acrylic copolymer according to claim 6, wherein the acrylic copolymer comprises 100 parts by weight of a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms, 0.01-5 parts by weight of a monomer of the formula (1) and 0.01-10 parts by weight of a monomer having a hydroxyl group .