KR20150122507A - Adhesive composition - Google Patents

Abstract

The present invention relates to an adhesive composition and, more specifically, to an adhesive composition comprising a silane coupling agent having a specific structure and an acrylic copolymer, wherein the composition can maintain excellent adhesive durability under extreme conditions such as high temperature and high humidity or the like and exhibits excellent reworkability when re-adhering after peeling as well as exhibiting excellent initial adhesive power when forming an adhesive layer.

Description

[0001] ADHESIVE COMPOSITION [0002]

The present invention relates to a pressure-sensitive adhesive composition capable of exhibiting excellent reworkability and adhesion durability when an adhesive layer is formed.

A liquid crystal display device is composed of a liquid crystal cell containing a liquid crystal and a polarizing plate, which is mainly bonded to one side of a polarizing plate by forming an adhesive layer. In addition, a retardation plate, a wide viewing angle compensation plate, or a brightness enhancement film is additionally attached to a polarizing plate through an adhesive or the like in order to improve the function of the liquid crystal display device.

Since the pressure-sensitive adhesive for bonding the polarizing plate and the liquid crystal cell can be exposed to high temperature and high humidity environment during the manufacturing process after the bonding, transportation or handling, it is required to have excellent durability so as to maintain the adhesive force even in such a harsh environment.

Further, the pressure-sensitive adhesive should be able to peel and re-bond if necessary in the event of misalignment, foreign matter contamination, or the like in the bonding process, so that the pressure-sensitive adhesive should have excellent peeling and re-bonding properties, that is, .

As a pressure-sensitive adhesive for use in the bonding, a pressure-sensitive adhesive composition containing a silane compound having a hydrocarbon group (JP-A-7-331204) is known. However, the above-mentioned pressure sensitive adhesive can not maintain a proper adhesive force to the extent required in actual use environments, and the adhesive force excessively increases under high temperature and high humidity conditions, or the pressure sensitive adhesive remains on the substrate upon peeling, have.

Japanese Laid-Open Patent Publication No. 7-331204

An object of the present invention is to provide a pressure-sensitive adhesive composition which can exhibit excellent reworkability.

It is an object of the present invention to provide a pressure-sensitive adhesive composition which can exhibit excellent pressure-sensitive durability even under severe conditions of high temperature and high humidity.

Another object of the present invention is to provide a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

Another object of the present invention is to provide a polarizing plate comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

It is another object of the present invention to provide an image display apparatus having the above polarizing plate.

1. A pressure-sensitive adhesive composition comprising a silane coupling agent represented by the following formula (1) and an acrylic copolymer:

[Chemical Formula 1]

Wherein R ₁ , R ₂ , R ₃ and R ₄ are independently of each other a straight or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkylcarbonyl group having 2 to 12 carbon atoms,

The alkyl group may be further substituted with at least one of a halogen atom and an alkoxy group having 1 to 5 carbon atoms,

And the alkylcarbonyl group may be further substituted with at least one of a halogen atom and an alkyl group having 1 to 5 carbon atoms.

2. The pressure-sensitive adhesive composition according to 1 above, wherein the compound of formula (1) is selected from compounds represented by the following formulas (2) to (10).

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

.

.

3. The pressure-sensitive adhesive composition according to 1 above, wherein the silane coupling agent is contained in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer.

4. The pressure-sensitive adhesive composition according to 1 above, wherein the acrylic copolymer is polymerized by including a polymerizable monomer having a carboxylic acid functional group in the molecule.

5. The pressure-sensitive adhesive composition according to 1 above, further comprising at least one crosslinking agent selected from the group consisting of an isocyanate-based, epoxy-based, metal chelating-based and oxazoline-based compound.

6. The pressure-sensitive adhesive composition according to item 1 above, wherein the pressure-sensitive adhesive composition is used for bonding between the polymer film and the glass substrate.

7. The pressure-sensitive adhesive composition according to 6 above, wherein said polymer film is a protective film for a polarizer or a polarizer.

8. The pressure-sensitive adhesive composition according to 6 above, wherein said bonded surface of said glass substrate comprises a silanol group and has a pH of 6.0 or less.

9. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition according to any one of items 1 to 8 above.

10. A polarizer comprising at least one side of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above 1 to 8.

11. An image display apparatus comprising the above-mentioned polarizing plate.

12. The image display apparatus according to 11 above, wherein the adhesive layer of the polarizing plate joins the polarizing plate to the glass substrate of the liquid crystal cell.

13. The image display apparatus of 12 above, wherein said bonded surface of said glass substrate comprises a silanol group and a portion having a pH of 6.0 or less.

The pressure-sensitive adhesive composition of the present invention not only has excellent initial adhesion at the time of forming an adhesive layer, but also exhibits excellent reworkability.

The pressure-sensitive adhesive composition of the present invention can exhibit good adhesion durability even under severe conditions of high temperature and high humidity when forming an adhesive layer.

The present invention includes the silane coupling agent and the acrylic copolymer represented by the general formula (1), thereby exhibiting an excellent initial adhesion when forming an adhesive layer, and an increase in adhesion due to heating or aging is small, And is capable of maintaining good adhesion durability even in severe conditions such as high temperature and high humidity.

Hereinafter, the present invention will be described in more detail.

≪ Pressure sensitive adhesive composition &

The pressure-sensitive adhesive composition of the present invention includes a silane coupling agent and an acrylic copolymer having a specific structure.

Silane Coupling agent

Typically, the silane coupling agent includes an organic reactor in the molecule to perform a covalent bond with the polymer matrix in the adherend (glass substrate) and the composition and to improve adhesion between the interface with the adherend.

Conventionally, a silane coupling agent containing an organic reactor having a high reactivity in order to improve the adhesive strength is used. In this case, the increase in the adhesion or the increase in the sticking power with time compared to the initial adhesion force is so large that when the polarizer is peeled from the adherend, There was a problem that adhesive residue remained on the adherend.

However, since the silane coupling agent of the present invention does not contain an organic reactive group in the molecule, it improves the recyclability of the pressure-sensitive adhesive layer and at the same time forms a polymer by self-condensation reaction, Excellent adhesion durability can be exhibited even under severe conditions of initial adhesion and high temperature and humidity.

For example, the pressure-sensitive adhesive composition according to the present invention can be more preferably used when it is applied between a polymer film and a glass substrate. It is preferable that the silanol group (-SiOH) present in the glass substrate is a silane coupling agent It acts as a catalyst for self-condensation reaction and contributes to improvement of adhesion. When the composition of the present invention is applied to a polarizing plate, the polymer film may mean a polarizer or a protective film for a polarizer.

The silane coupling agent according to the present invention is represented by the following general formula (1).

[Chemical Formula 1]

Wherein R ₁ , R ₂ , R ₃ and R ₄ are independently of each other a straight or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkylcarbonyl group having 2 to 12 carbon atoms,

The alkyl group may be further substituted with at least one of a halogen atom and an alkoxy group having 1 to 5 carbon atoms,

And the alkylcarbonyl group may be further substituted with at least one of a halogen atom and an alkyl group having 1 to 5 carbon atoms.

The kind of the silane coupling agent according to the present invention is not particularly limited, but may be at least one selected from compounds represented by the following formulas (2) to (10).

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

The content of the silane coupling agent of the present invention is not particularly limited, but may be 0.001 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer. When the above range is satisfied, it is possible to exhibit proper reworkability and durability. On the other hand, when the amount is less than 0.001 part by weight, the effect is difficult to achieve as a trace amount. When the amount exceeds 5 parts by weight, the adhesive property is deteriorated by bleeding out of the silane coupling agent. It can easily happen.

Acrylic copolymer

The acrylic copolymer according to the present invention preferably contains a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms and a polymerizable monomer having a crosslinkable functional group.

Here, (meth) acrylate means acrylate and methacrylate.

Examples of the (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms include n-butyl (meth) acrylate, 2-butyl (meth) acrylate, (Meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (Meth) acrylate, n-butyl acrylate, nonyl (meth) acrylate, decyl (meth) acrylate and lauryl Or a mixture thereof. These may be used alone or in combination of two or more.

The polymerizable monomer having a cross-linkable functional group is a component for imparting durability and cutability by reinforcing the cohesive strength or adhesive strength of the pressure-sensitive adhesive composition by chemical bonding, and examples thereof include monomers having a hydroxy group, monomers having a carboxyl group, monomers having an amide group, Monomers having a tertiary amine group, and the like. These monomers may be used alone or in admixture of two or more.

The polymerizable monomer is preferably a polymerizable monomer having a carboxylic acid functional group in order to promote the reaction in which the silane coupling agent of the present invention self-condenses to form an oligomer.

Examples of the monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl Hydroxypropyleneglycol (meth) acrylate, hydroxyalkylene glycol having 2 to 4 carbon atoms in the alkylene group (e.g., methoxyethyl (meth) acrylate, Hydroxybutyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl (meth) acrylate, 4-hydroxybutyl vinyl ether, Vinyl ether, and 10-hydroxydecyl vinyl ether, among which 4-hydroxybutyl vinyl ether is preferable.

Examples of the monomer having a carboxyl group include monovalent acids such as (meth) acrylic acid and crotonic acid; Dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and monoalkyl esters thereof; 3- (meth) acryloylpropionic acid; A succinic anhydride ring-opening addition adduct of 2-hydroxyalkyl (meth) acrylate in which the alkyl group has 2 to 4 carbon atoms, anhydrous succinic ring opening adduct of a hydroxyalkylene glycol (meth) acrylate having 2 to 4 carbon atoms in the alkylene group , And compounds obtained by ring-opening addition of succinic anhydride to a caprolactone adduct of 2-hydroxyalkyl (meth) acrylate in which the alkyl group has 2-3 carbon atoms. Of these, (meth) acrylic acid is preferable.

Examples of the monomer having an amide group include (meth) acrylamide, N-isopropyl acrylamide, N-tertiary butyl acrylamide, 3-hydroxypropyl (meth) acrylamide, 4-hydroxybutyl (Meth) acrylamide, 8-hydroxyoctyl (meth) acrylamide, and 2-hydroxyethylhexyl (meth) acrylamide. Of these, (meth) acrylamide is preferable.

Examples of the monomer having a tertiary amine group include N, N- (dimethylamino) ethyl (meth) acrylate, N, N- (diethylamino) ethyl (meth) Methacrylate, and the like.

The polymerizable monomer having a crosslinkable functional group is preferably contained in an amount of 0.05 to 10 parts by weight, more preferably 0.1 to 8 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 0.05 part by weight, the cohesive force of the pressure-sensitive adhesive becomes small and durability may be deteriorated. When the content is more than 10 parts by weight, a high gel fraction may lower the adhesive strength and cause durability problems.

The acrylic copolymer may further contain other polymerizable monomers other than the above monomers in an amount not lowering the adhesive force, for example, 10% by weight or less based on the total amount.

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 acrylic copolymer preferably has a weight average molecular weight (polystyrene conversion, Mw) of 50,000 to 2,000,000, more preferably 400,000 to 2,000,000 as measured by Gel Permeation Chromatography (GPC). When the weight-average molecular weight is less than 50,000, cohesion between co-polymers may be insufficient, which may cause problems in adhesion durability. If the weight average molecular weight is more than 2,000,000, a large amount of a diluting solvent may be required in order to ensure fairness in coating.

Cross-linking agent

The pressure-sensitive adhesive composition of the present invention may further comprise a crosslinking agent. The crosslinking agent can improve adhesion and durability, maintain reliability at high temperature, and maintain the shape of the pressure-sensitive adhesive.

The cross-linking agent may be an isocyanate-based, epoxy-based, peroxide-based, metal chelating-based, oxazoline-based, or the like. A double isocyanate-based is preferred.

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 a crosslinking agent may be contained in an amount of 0.1 to 15 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer. If the content is less than 0.1 part by weight, the cohesive strength may be decreased due to insufficient crosslinking, which may deteriorate the durability of the adhesive durability and the cutability. If the content is more than 15 parts by weight, the residual stress due to the excessive crosslinking reaction may be deteriorated.

additive

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, and the like.

<Adhesive sheet>

The present invention also provides a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

The adhesive sheet of the present invention can be applied to a polarizing plate and a surface protective film for bonding with a liquid crystal cell. The present invention is applicable not only to a protective film, a reflective sheet, a structural adhesive sheet, a photographic adhesive sheet, a lane marking adhesive sheet, an optical adhesive product, an adhesive for electronic components, a general commercial adhesive sheet product, and a medical patch.

The thickness of the adhesive layer is not particularly limited and may be, for example, 3 to 100 m, preferably 10 to 100 m.

The pressure sensitive adhesive sheet of the present invention comprises an adhesive layer formed on at least one surface of a release film.

The pressure-sensitive adhesive layer can be formed by coating the pressure-sensitive adhesive composition on at least one surface of the release film. The coating method is not particularly limited and a method known in the art may be used. For example, a method such as bar coater, air knife, gravure, reverse roll, kiss roll, spray, blade, die coater, casting, Can be used.

The releasing film is not particularly limited, and a releasing film commonly used for the pressure-sensitive adhesive sheet can be used, and examples thereof include polyester resins such as polyethylene terephthalate, polybutylene terephthalide, polyethylene naphthalate and polybutylene naphthalate; Polyimide resin; Acrylic resin; Styrene-based resins such as polystyrene and acrylonitrile-styrene; Polycarbonate resin; Polylactic acid resin; Polyurethane resin; Polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymer; Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; Polyamide resins; Sulfonic resin; Polyether-ether ketone resin; Allylate series resin; Or a mixture of these resins.

The thickness of the release film is not particularly limited, and may be, for example, from 5 to 500 mu m, and preferably from 10 to 100 mu m.

<Polarizer>

The present invention also provides a polarizing plate comprising an adhesive layer formed on at least one side of the pressure-sensitive adhesive composition.

The polarizing plate of the present invention comprises a polarizer, a protective film bonded to at least one surface of the polarizer, and an adhesive layer formed on the protective film with the adhesive composition.

The polarizer may be a polarizer well-known in the art, for example, a polyvinyl alcohol film produced through a process such as swelling, dyeing, crosslinking, stretching, washing, drying and the like.

The protective film is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. Specifically, polyester films such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate; Cellulose-based films such as diacetylcellulose and triacetylcellulose; Polycarbonate-based films; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene-based films such as polystyrene and acrylonitrile-styrene copolymer; Polyolefin films; Vinyl chloride film; Polyamide-based films such as nylon and aromatic polyamide; Imidazole film; Sulfone based films; Polyether ketone-based films; A sulfided polyphenylene-based film; Vinyl alcohol film; Vinylidene chloride films; Vinyl butyral film; Allylate-based films; Polyoxymethylene-based films; Urethane-based films; Epoxy-based films; Silicone-based films, and the like. Among them, a cellulose-based film having a surface saponified (saponified) by alkali or the like is preferable in consideration of polarization characteristics or durability. In addition, the protective film may have the function of an optical layer.

The adhesive layer may be coated directly on the protective film, or may be formed by adhering an adhesive sheet to the protective film.

<Image Display Device>

Further, the present invention provides an image display apparatus including the polarizing plate.

The adhesive layer of the polarizing plate may be used to bond the glass substrate of the liquid crystal cell of the polarizing plate, and the bonding surface of the organic substrate may include a silanol group (-SiOH) and a portion having a pH of 6.0 or less.

As a specific example, the above-described glass substrate may be etched so as to contain a large amount of a silanol group (-SiOH). After the etching treatment, it is judged that the silanol group acts as a catalyst in the portion containing a large amount of the silanol group (-SiOH), so that the silane coupling agent of the adhesive layer can form the self condensation reaction. Thereafter, the self-condensed polymer is able to exhibit excellent initial adhesion and excellent adhesion durability even under severe conditions of high temperature and high humidity by intermolecular entanglement with the acrylic copolymer.

In this respect, the pH of the portion containing a large amount of the silanol group may be 6.0 or less, preferably pH 5.6 or less. As described above, the portion in which the silanol group capable of acting as a catalyst of the self-condensation reaction sufficiently exists satisfies the above-described pH condition, and the bonding strength with the silane coupling agent inside the adhesive layer formed by the pressure- have.

In other words, the image display device according to the present invention has the above-described structure, thereby making it possible to exhibit excellent adhesion durability.

Further, the image display apparatus of the present invention may further include a configuration known in the art in addition to the above configuration.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Manufacturing example  1: Preparation of acrylic copolymer

1- (1): Preparation of Acrylic Copolymer A-1

85 parts by weight of n-butyl acrylate (BA), 7 parts by weight of methyl acrylate (MA), 5 parts by weight of 2-hydroxyethyl acrylate , And 3 parts by weight of acrylic acid, and then 100 parts by weight of ethyl acetate (Eac) was introduced as a solvent. Nitrogen gas was then purged for 1 hour to remove oxygen and then maintained at 62 ° C. After the mixture was homogeneously mixed, 0.07 part by weight of azobisisobutyronitrile (AIBA) was added as a reaction initiator and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight: about 1,000,000).

1- (2): Preparation of Acrylic Copolymer A-2

90 parts by weight of n-butyl acrylate (BA), 5 parts by weight of methyl acrylate (MA), 4 parts by weight of 2-hydroxyethyl acrylate (4 parts by weight) , And 1 part by weight of acrylic acid, and then 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for 1 hour to remove oxygen and then maintained at 62 ° C. After the mixture was homogeneously mixed, 0.07 part by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight: about 1,000,000).

1- (3): Preparation of Acrylic Copolymer A-3

Acrylic acid copolymer (weight average molecular weight: about 1,000,000) was prepared in the same manner as in Production Example 1, except that carboxyethyl acrylate was used instead of acrylic acid.

1- (4): Preparation of Acrylic Copolymer A-4

 Acrylic acid copolymer (weight average molecular weight: about 1,000,000) was prepared in the same manner as in Preparation Example 1, except that 2-acryloyloxyhydrogen succinate was used instead of acrylic acid.

Example  And Comparative Example

Each component was mixed using the ingredients and the contents shown in Table 1 below and then diluted to 20% by weight with a methyl ethyl ketone solvent to prepare a pressure-sensitive adhesive composition.

division
(Parts by weight) Acrylic copolymer Silane coupling agent Cross-linking agent ingredient content ingredient content ingredient content Example 1 A-1 100 B-1 0.1 C-1 One Example 2 A-1 100 B-1 0.5 C-1 One Example 3 A-1 100 B-1 1.0 C-1 One Example 4 A-1 100 B-1 2.0 C-1 One Example 5 A-1 100 B-1 5.0 C-1 One Example 6 A-1 100 B-1 0.5 C-2 One Example 7 A-1 100 B-1 0.5 C-3 One Example 8 A-1 100 B-1 0.5 C-4 One Example 9 A-2 100 B-1 0.5 C-1 One Example 10 A-2 100 B-1 0.5 C-2 One Example 11 A-3 100 B-1 0.5 C-2 One Example 12 A-4 100 B-1 0.5 C-2 One Example 13 A-1 100 B-1 0.01 C-1 One Example 14 A-1 100 B-2 0.5 C-1 One Example 15 A-1 100 B-3 0.5 C-1 One Example 16 A-1 100 B-4 0.5 C-1 One Comparative Example 1 A-1 100 - - C-1 One Comparative Example 2 A-1 100 B-5 0.5 C-1 One Comparative Example 3 A-1 100 B-6 0.5 C-1 One

B-2:

B-3:

B-4:

B-5: 3-글리시독시프로필트리메톡시실란, KBM-403 (신에츠사)
B-6: 3-아세토아세톡시프로필트리메톡시실란, AAPS (신에츠사)
C-1: 코로네이트-L (TDI의 TMP어덕트, 일본우레탄사)
C-2: 코로네이트-HXR (HDI의 이소누아레이트, 일본우레탄사)
C-3: D110N (HDI-TMP어덕트, 미쯔이 화학)
C-4: D140N (IPDI-TMP어덕트, 미쯔이 화학)A-1: Acrylic copolymer of Production Example 1- (1)
A-2: Acrylic copolymer of Production Example 1- (2)
A-3: Acrylic copolymer of Production Example 1- (3)
A-4: Acrylic copolymer of Production Example 1- (4)
B-1:

B-2:

B-3:

B-4:

B-5: 3-glycidoxypropyltrimethoxysilane, KBM-403 (Shin-Etsu)
B-6: 3-acetoacetoxypropyltrimethoxysilane, AAPS (Shinetsu)
C-1: Coronate-L (TMP adduct of TDI, Urethane Japan)
C-2: Coronate-HXR (isoniazoate of HDI, Urethane Company of Japan)
C-3: D110N (HDI-TMP adduct, Mitsui Chemicals)
C-4: D140N (IPDI-TMP adduct, Mitsui Chemicals)

Test Methods

The pressure-sensitive adhesive composition prepared above was cured on a releasing film coated with a silicone release agent to a thickness of 25 mu m and dried at 100 DEG C for 1 minute, 5 minutes and 10 minutes to form an adhesive layer. A release film was laminated on the pressure-sensitive adhesive layer to produce a pressure-sensitive adhesive sheet.

After the release film of the pressure-sensitive adhesive sheet thus prepared was peeled off, the pressure-sensitive adhesive layer prepared above was laminated on an iodine-based polarizing plate having a thickness of 185 탆 by sticking to produce a polarizing plate. The prepared polarizing plate was stored for a curing period under the conditions of 23 캜 and 60% RH.

(1) Evaluation of adhesion durability (heat resistance and Humidity Durability )

The prepared polarizing plate was cut into a size of 90 mm x 170 mm and the release film was peeled off. Then, both surfaces of the glass substrate (110 mm x 190 mm x 0.7 mm) So that the absorption axes of the respective polarizing plates were orthogonal to each other. At this time, the applied pressure was 5 kg / cm ² , and a clean room operation was performed so that bubbles or foreign matter would not be generated.

The heat resistance of the specimen was maintained 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 for 1000 hours under the conditions of a temperature of 60 ° C and a humidity of 90% RH, and then the occurrence of bubbles or peeling was observed.

<Evaluation Criteria>

Ⓞ: No bubble or peeling

○: Less than 5 bubbles or peeling

△: Bubbles or peeling 5 or more and less than 10

X: 10 or more bubbles or peeling

(2) Re-workability  evaluation

The polarizing plate was cut into a size of 25 mm in width and 100 mm in length and the release film was peeled off and laminated to Corning's # 1737 glass at a pressure of 0.25 MPa (acid treatment on the bonding surface to confirm the pH 5.6) The autoclave was treated for 20 minutes under conditions of 5 atm and 50 deg. C to prepare evaluation samples. After putting it in an oven at 80 ° C, which was a heat-resistant condition, it was taken out after 10 hours, left at room temperature for 120 hours, and peeled at a rate of 1.3 cm / s. In addition, it was placed in an oven at 60 DEG C and 90RH% in a humid condition, taken out after 12 hours, left at room temperature for 120 hours, and peeled at a rate of 1.3 cm / s.

<Evaluation Criteria>

?: No peeling of the pressure-sensitive adhesive on the glass substrate in both the conditions, and the glass substrate was cleanly peeled off without tearing the polarizing plate

?: No adhesive transfer or tearing of the polarizing plate was observed, but haze was observed on the surface of the panel after peeling.

X: Pressure-sensitive adhesive remains on the panel under either condition or the polarizer tears in the peeling process

(3) Evaluation of initial / warm adhesion - Adhesion (N / 25 mm)

The polarizing plate with a pressure-sensitive adhesive was cut to a size of 25 mm x 100 mm and the release film was peeled off and laminated to a glass substrate (# 1737, Corning) at a pressure of 0.25 MPa , And autoclave treatment was carried out to prepare specimens.

The initial adhesive strength of the specimens after being left for 24 hours under the conditions of 23 ° C. and 50% RH and the temperature bonding strength after 48 hours at 50 ° C. and 50% RH were measured using a universal tensile tester (UTM, Instron) The peeling speed was 300 mm / min, and the peeling angle was 180 deg. At this time, measurement was carried out under conditions of 23 캜 and 50% RH.

division durability Re-workability Initial adhesion Thermal adhesion Heat resistance Wet heat Example 1 ◎ ◎ ○ 7.7 9.8 Example 2 ◎ ◎ ○ 7.2 9.3 Example 3 ◎ ◎ ○ 6.5 8.4 Example 4 ○ ◎ ○ 5.2 6.2 Example 5 ○ ○ ○ 4.3 5.7 Example 6 ◎ ◎ ○ 7.4 9.7 Example 7 ◎ ◎ △ 8.2 11.1 Example 8 ◎ ◎ △ 8.9 12.3 Example 9 ◎ ◎ ○ 5.1 7.1 Example 10 ◎ ◎ ○ 4.7 6.9 Example 11 ◎ ◎ △ 11.5 15.3 Example 12 ◎ ◎ △ 13.1 17.6 Example 13 ◎ ○ △ 9.1 12.2 Example 14 ○ ◎ ○ 6.8 9.2 Example 15 ○ ◎ ○ 6.2 9.3 Example 16 ◎ ◎ ○ 7.4 9.6 Comparative Example 1 ○ × ○ 9.8 12.0 Comparative Example 2 ◎ ◎ × 5.2 23.9 Comparative Example 3 ○ ◎ × 5.8 21.0

Table 1 shows that when the pressure-sensitive adhesive composition according to the present invention was used (Examples 1 to 16), not only excellent initial adhesive strength was exhibited but also an increase in adhesive strength due to heat treatment or aging was small, , And excellent adhesive durability was maintained even under severe conditions such as high temperature and high humidity.

In the case of Comparative Example 1 in which no silane coupling agent was used at all, it was confirmed that the adhesion durability was remarkably lowered. In the case of Comparative Examples 2 and 3 using a different kind of silane coupling agent, the durability to adhesion and the initial adhesive strength were the same However, it was confirmed that the adhesive strength was rapidly increased under the heating condition, and thus the reworkability was remarkably decreased.

Claims (13)

A pressure-sensitive adhesive composition comprising a silane coupling agent represented by the following formula (1) and an acrylic copolymer:
[Chemical Formula 1]

Wherein R ₁ , R ₂ , R ₃ and R ₄ are independently of each other a straight or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkylcarbonyl group having 2 to 12 carbon atoms,
The alkyl group may be further substituted with at least one of a halogen atom and an alkoxy group having 1 to 5 carbon atoms,
And the alkylcarbonyl group may be further substituted with at least one of a halogen atom and an alkyl group having 1 to 5 carbon atoms.
The pressure-sensitive adhesive composition according to claim 1, wherein the compound of formula (1) is selected from compounds represented by the following formulas (2) to (10).
(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

.
The pressure-sensitive adhesive composition according to claim 1, wherein the silane coupling agent is contained in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer.
The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer is polymerized by including a polymerizable monomer having a carboxylic acid functional group in the molecule.
The pressure-sensitive adhesive composition according to claim 1, further comprising at least one crosslinking agent selected from the group consisting of isocyanate-based, epoxy-based, metal chelating-based, and oxazoline-based compounds.
The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is used for bonding between the polymer film and the glass substrate.
The pressure-sensitive adhesive composition according to claim 6, wherein the polymer film is a protective film for a polarizer or a polarizer.
7. The pressure-sensitive adhesive composition according to claim 6, wherein the bonded surface of the glass substrate comprises a silanol group and a pH of 6.0 or less.
A pressure-sensitive adhesive sheet comprising an adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 8.
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed on at least one surface thereof with the pressure-sensitive adhesive composition according to any one of claims 1 to 8.
An image display apparatus comprising the polarizing plate of claim 10.
The image display apparatus according to claim 11, wherein the adhesive layer of the polarizing plate joins the polarizing plate to the glass substrate of the liquid crystal cell.
The image display apparatus according to claim 12, wherein the bonded surface of the glass substrate includes a silanol group and a portion having a pH of 6.0 or less.