KR20120137266A - Adhesive composition, polarizing plate and liquid crystal display device comprising the same - Google Patents

Abstract

PURPOSE: An adhesive composition is provided to ensure adhesion and durability as an adhesive, to remarkably reduce a curing time, and to secure enough pot-life because of low viscosity and viscosity changing rate. CONSTITUTION: An adhesive composition comprises an acryl-based copolymer, an isocyanate-based crosslinking agent, and a Lewis acid crosslinking promoter. When the solid content is 28 weight%, the initial viscosity is 350-450 cP at 23 °C and the viscosity changing rate is 20% or less after leaving at 21-25 °C for 24 hours. An adhesive composition comprises 0.1-5 parts by weight of the isocyanate-based crosslinking agent and 0.008-0.04 parts by weight of the Lewis acid crosslinking promoter with respect to100.0 parts by weight of the acryl-based copolymer based on solid content.

Description

Adhesive composition, polarizing plate and liquid crystal display including the same {ADHESIVE COMPOSITION, POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE COMPRISING THE SAME}

The present invention can shorten the curing period and ensure sufficient pot-life while satisfying the physical properties required as the pressure-sensitive adhesive, environmentally friendly and economical pressure-sensitive adhesive composition that can minimize the amount of dilution solvent during coating, a polarizing plate comprising the same and It relates to a liquid crystal display device.

A liquid crystal display device (LCD) includes a liquid crystal panel including a liquid crystal cell and a polarizing plate bonded to both surfaces of the liquid crystal cell via an adhesive layer.

The pressure-sensitive adhesive for bonding the liquid crystal cell and the polarizing plate must satisfy the physical properties of the pressure-sensitive adhesive, such as adhesion to the substrate, heat resistance and heat and moisture resistance, and with this, the curing period should be shortened to improve productivity.

In general, as the pressure-sensitive adhesive for bonding the liquid crystal cell and the polarizing plate, an acrylic pressure-sensitive adhesive having a weight average molecular weight of 1 million to 1.5 million has been mainly used. Since the pressure-sensitive adhesive has a high weight average molecular weight, a large amount of diluting solvent (eg, ethyl acetate, toluene, etc.) is required during coating, and thus, the drying time is too long, resulting in poor production efficiency.

In addition, with the revision of the Air Pollution Prevention Act, etc., regulations on the emission of volatile organic compounds (VOCs), which are dilution solvents, have been tightened, and pressure-sensitive adhesives that can minimize the use of dilution solvents during coating are required.

In view of this, Korean Patent Publication No. 2010-0039274 discloses a (meth) acrylic polymer having a viscosity of 5,000-10,000 cP and a weight average molecular weight of 300,000 to 900,000 when the solid content is 30% by weight. An adhesive for polarizing plates formed by crosslinking with an isocyanate-based crosslinking agent in the presence of a crosslinking accelerator is disclosed. The pressure-sensitive adhesive can secure durability of the polarizing plate even when a polymer having a low weight average molecular weight is used, but has a disadvantage in that processability is poor due to high viscosity of the polymer.

In addition, Japanese Laid-Open Patent Publication No. 2007-009006 discloses a pressure-sensitive adhesive composition in which a resin composition having a weight average molecular weight of 200,000-700,000 and a resin composition having a weight average molecular weight of 50,000 or less is mixed, but the pressure-sensitive adhesive satisfies the durability of the polarizing plate. Difficult to let

Patent Document 1: Korean Patent Publication No. 2010-0039274 Patent Document 2: Japanese Patent Application Laid-Open No. 2007-009006

It provides a pressure-sensitive adhesive composition that satisfies the physical properties required as a conventional pressure-sensitive adhesive, while improving the productivity by shortening the curing period and securing sufficient pot-life, which is advantageous in terms of process, and also minimizes the amount of diluted solvent used during coating. It aims to do it.

Another object of the present invention is to provide a polarizing plate in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is laminated.

Another object of the present invention is to provide a liquid crystal display device having the polarizing plate on at least one side of a liquid crystal cell.

1. Viscosity change rate after acryl-based copolymer, isocyanate-based crosslinking agent and Lewis acid cross-linking accelerator, when the solid content is 28% by weight, its initial viscosity is 350-450cP at 23 ° C and left at 21-25 ° C for 24 hours. The pressure-sensitive adhesive composition which is 20% or less.

2. In the above 1, the pressure-sensitive adhesive composition comprising 0.1 to 5 parts by weight of isocyanate-based crosslinking agent and 0.008 to 0.04 parts by weight of Lewis acid crosslinking accelerator based on 100 parts by weight of the acrylic copolymer based on the solid content.

3. In the above 1, the isocyanate-based crosslinking agent is at least one member selected from the group consisting of hexamethylene diisocyanate and its adducts, isocyanurate body and biuret body.

4. In the above 1, Lewis acid is dibutyltin octoate, dibutyltin dioleyl maleate, dibutyltin dibutyl maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylaceto Nitrate, dibutyltin bistriethoxysilicate, dibutyltin distearate, dioctyltin distearate, dioctyltin dilaurate, dioctyltin diacetate, dibutyltin bisisononyl 3-meractopropionate Pressure-sensitive adhesive composition which is at least one organic tin-based compound selected from the group consisting of dibutyltin bisisooctylthioglycol, dimethyltin bisisooctylthioglycol, dioctyltin bisisooctylthioglycol and dilauryl tin bisoctylthioglycol.

5. The polarizing plate of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of any one of 1 to 4 above.

6. Liquid crystal display device provided with the polarizing plate of the above 5 on at least one side of the liquid crystal cell.

The pressure-sensitive adhesive composition according to the present invention can secure the adhesive strength and durability as the pressure-sensitive adhesive and can significantly shorten the curing period to improve productivity.

In addition, the pressure-sensitive adhesive composition of the present invention is low in viscosity and its rate of change, thereby ensuring sufficient pot-life, and is stable in terms of process. It is environmentally friendly and economical in terms of cost.

The present invention can shorten the curing period and ensure sufficient pot-life while satisfying the physical properties required as the pressure-sensitive adhesive, environmentally friendly and economical pressure-sensitive adhesive composition that can minimize the amount of dilution solvent during coating, a polarizing plate comprising the same and It relates to a liquid crystal display device.

Hereinafter, the present invention will be described in detail.

The pressure-sensitive adhesive composition of the present invention includes an acrylic copolymer, an isocyanate-based crosslinking agent and a Lewis acid crosslinking accelerator, in particular, its initial viscosity is 350-450 cP at 23 ° C. and the viscosity change rate after being left at 21-25 ° C. for 24 hours is 20%. It is characterized by the following.

The acrylic copolymer of the present invention may be a copolymer of a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms and a monomer having a crosslinkable functional group. Here, (meth) acrylate means both acrylate and methacrylate.

As a (meth) acrylate monomer which has a C1-C12 alkyl group, n-butyl (meth) acrylate, 2-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate , 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acryl Elate, pentyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, etc. are mentioned. These may be used alone or in combination of two or more thereof. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, or a mixture thereof is preferable.

The (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms is preferably contained in an amount of 85 to 99.9% by weight, more preferably 90 to 95% by weight, based on 100% by weight of the total monomers used for preparing the acrylic copolymer. It is good to be%. If the content is less than 85% by weight, the initial adhesive strength may not be sufficient, and when the content is more than 99.9% by weight, durability may be weakened.

The monomer having a crosslinkable functional group is a component for reinforcing the cohesive force or adhesive strength of the pressure-sensitive adhesive composition by chemical bonding to impart durability and cleavage, such as a monomer having a hydroxy group, a monomer having a carboxyl group, a monomer having an amide group, and a tertiary The monomer which has an amine group, the monomer which has a vinyl group, etc. are mentioned, These can be used individually or in mixture of 2 or more types.

As a monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Hydroxyalkylene glycols having 2 to 4 carbon atoms of alkylene groups such as 6-hydroxyhexyl (meth) acrylate, 2 hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate ( Methacrylate, etc. are mentioned, Among these, 2-hydroxyethyl (meth) acrylate 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; Succinic anhydride ring-opening adduct of 2-hydroxyalkyl (meth) acrylate with 2-3 carbon atoms of an alkyl group, Succinic anhydride ring opening adduct of hydroxyalkylene glycol (meth) acrylate with 2-4 carbon atoms of an alkylene group And a compound obtained by ring-opening addition of succinic anhydride to a caprolactone adduct of 2-hydroxyalkyl (meth) acrylate having 2 to 3 carbon atoms of an alkyl group.

Examples of the monomer having an amide group include (meth) acrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, and 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) ) Acrylate, and the like.

N-vinylpyrrolidone, N-vinyl caprolactam, etc. are mentioned as a monomer which has a vinyl group.

It is preferable that the monomer which has a crosslinkable functional group is contained in 0.1 to 15 weight% with respect to 100 weight% of total monomers used for manufacture of an acryl-type copolymer, More preferably, it is 1 to 8 weight%. If the content is less than 0.1% by weight, the cohesive force of the pressure-sensitive adhesive may be reduced, the durability may be lowered. If the content is more than 15% by weight, the adhesive strength may be degraded by a high gel fraction and may cause a problem in durability.

In addition, other polymerizable monomers in addition to the monomers may be further included in a range that does not lower the adhesion, such as 10% by weight or less.

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 has a weight average molecular weight (Mw, polystyrene equivalent) measured by gel permeation chromatography (GPC), usually 200,000 to 1.50,000, preferably 300,000 to 1 million. If the weight average molecular weight is less than 200,000, there is a lack of cohesion between the copolymers may cause problems in adhesion durability, if the weight average molecular weight is more than 1.5 million may require a large amount of dilution solvent to ensure fairness during coating.

As a crosslinking agent, it is for strengthening the cohesion force of an adhesive by crosslinking an acryl-type copolymer suitably, In this invention, an isocyanate type crosslinking agent is more preferable especially from a reactive point with a Lewis acid crosslinking promoter.

As isocyanate type crosslinking agent, tolylene diisocyanate, xylene diisocyanate, 2, 4- diphenyl methane diisocyanate, 4, 4- diphenyl methane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate Diisocyanate compounds such as naphthalene diisocyanate; Diisocyanate obtained from 2 moles of an adduct obtained by reacting 3 moles of a diisocyanate compound with 1 mole of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate obtained by self-condensing 3 moles of the diisocyanate compound, and 3 moles of the diisocyanate compound And polyfunctional isocyanate compounds containing three functional groups such as biuret, triphenylmethanetriisocyanate and methylenebistriisocyanate, in which the remaining 1 mole of diisocyanate is condensed to urea. Can be used. Among them, hexamethylene diisocyanate and its adducts, isocyanurates, biurets, and the like are particularly preferred in that crosslinking reactions occur more effectively even in a low viscosity adhesive composition with long chains.

In addition, the melamine compound may be used alone or in combination of two or more kinds together with the isocyanate crosslinking agent. Hexamethylol melamine, hexamethoxymethylmelamine, hexabutoxymethylmelamine, etc. are mentioned as a melamine type compound.

The content of the crosslinking agent is not particularly limited as long as it can satisfy the initial viscosity and viscosity change rate characteristics of the pressure-sensitive adhesive composition together with other components. For example, acrylic copolymers based on solids content It is preferable to be contained in 0.1-5 weight part with respect to 100 weight part, More preferably, it is 0.2-2 weight part. If the content is less than 0.1 part by weight, the cohesion force becomes small due to insufficient crosslinking degree, which may cause deterioration of durability such as lifting and damage of cutting property.If the content is more than 5 parts by weight, durability deterioration is caused by excessive crosslinking reaction and storage stability. Can also fall.

In particular, the present invention is characterized by the use of an acidic crosslinking accelerator Lewis acid as a crosslinking accelerator which is a catalyst for controlling the curing rate by accelerating the crosslinking reaction between the isocyanate crosslinking agent and the functional group contained in the acrylic copolymer.

Lewis acids are organometallic compounds having electron accepting properties, and in particular, organic tin compounds are selected and used in the present invention. The organotin compound is not only higher in crosslinking accelerator efficiency than other crosslinking accelerators, but also more effective in combination with an isocyanate compound, which is a crosslinking agent. In addition, in the case of using a conventional crosslinking accelerator other than the tin-based compound, the pressure-sensitive adhesive is applied by applying a pressure-sensitive adhesive composition to a peelable substrate, removing an organic solvent to form a pressure-sensitive adhesive layer, and transferring the formed pressure-sensitive adhesive layer to a substrate, for example, a polarizing plate. In many cases, an attached polarizing plate is produced. On the other hand, the tin-based compound has good efficiency of the crosslinking promotion reaction and can form an adhesive layer even when directly applied to a substrate.

As the organic tin compound, dibutyltin octoate, dibutyltin dioleyl maleate, dibutyltin dibutyl maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, di Butyl tin bistriethoxy silicate, dibutyl tin distearate, dioctyl tin distearate, dioctyl tin dilaurate, dioctyl tin diacetate, dibutyl tin bisisononyl 3-meractopropionate, dibutyl Tin bisisooctyl thioglycol, dimethyl tin bisisooctyl thioglycol, dioctyl tin bisisooctyl thioglycol, dilauryl tin bis octyl thioglycol, and the like.

The content of the crosslinking accelerator is not particularly limited as long as it can satisfy the initial viscosity and viscosity change rate characteristics of the pressure-sensitive adhesive composition together with other components. For example, acrylic copolymers based on solids content It is preferable to be contained in 0.008-0.04 weight part with respect to 100 weight part, More preferably, it is 0.008-0.03 weight part. If the content is less than 0.008 parts by weight, the effect of promoting the crosslinking reaction may be insignificant. If the content is more than 0.04 parts by weight, the storage stability of the pressure-sensitive adhesive may be poor, resulting in a short pot-life, which may lower processability.

In addition, the pressure-sensitive adhesive composition of the present invention may further include a silane coupling agent.

The kind of the silane coupling agent is not particularly limited, and for example, vinylchlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxy Propyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-metha Krilloxypropyl triethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyl diethoxysilane, 3-acryloxypropyl trimethoxysilane , N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyl Methyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyl Dimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, and the like. These can be used individually or in mixture of 2 or more types.

The silane coupling agent may be included in an amount of 0 to 10 parts by weight, preferably 0.005 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer based on the solid content. If the content is more than 10 parts by weight, durability may be reduced.

In addition, the pressure-sensitive adhesive composition of the present invention may further include an antistatic agent with the above components.

The kind of antistatic agent is not particularly limited, and may include metal oxides such as ITO, ATO, tin oxide, zinc oxide, antimony oxide and indium oxide; Conductive polymers such as polythiophene (such as PEDOT of Bayer), polyaniline, polypyrrole; Alkali metal salts such as NaPF ₆ , NaSbF ₆ , KPF ₆ , and KSbF ₆ ; Fluorinated organometallic compounds such as 3M's HQ-115; Poly (acrylamide-co-diallyldimethylammonium chloride solution, 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM] [PF ₆ ], 1-butyl-3- (2-hydroxyethyl) imine Quaternary ammonium salts, such as dazolium bis (trifluoromethanesulfonyl) imide [BHEIM] [NTf ₂ ], tetrabutylmethylammonium bis (trifluoromethanesulfonyl) imide [TBMA] [NTf ₂ ], etc. ; Ionic compounds such as hexylpyridinium hexafluorophosphate, dodecylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, and the like. Can be used.

The antistatic agent may be included in an amount of 0 to 5 parts by weight, preferably 0.05-3 parts by weight, based on 100 parts by weight of the acrylic copolymer based on the solid content. If the content is more than 5 parts by weight, transparency may be lowered.

In addition to the above components, the pressure-sensitive adhesive composition is a tackifying resin, antioxidant, corrosion inhibitor, leveling agent, surface lubricant, dye, pigment in order to adjust the adhesion, cohesion, viscosity, modulus, glass transition temperature, etc. required according to the application It may further include additives such as antifoaming agent, filler, light stabilizer.

It is preferable that the adhesive composition of this invention has an initial viscosity of 350-450 cP at 23 degreeC, when solid content is 28 weight%. If the initial viscosity is less than 350cP, the viscosity is excessively low to reduce the coatability and staining may occur, and if it is more than 450cP pot-life may be shortened.

At the same time, the pressure-sensitive adhesive composition of the present invention preferably has a change rate of 20% or less at 23 ° C. after being left at room temperature, such as 21-25 ° C. for 24 hours. When the viscosity change rate is more than 20%, a change in coating properties and physical properties may occur according to the viscosity change of the pressure-sensitive adhesive composition during the coating process, thereby lowering the production stability.

The pressure-sensitive adhesive composition as described above can shorten the curing period, the viscosity and the rate of change of viscosity can be adjusted low to secure sufficient pot-life and can also minimize the amount of dilution solvent used during coating. As a result, production efficiency and fairness can be increased, environmentally friendly and cost can be reduced.

The pressure-sensitive adhesive composition of the present invention can be used both as a pressure-sensitive adhesive for surface protection film as well as pressure-sensitive adhesive for polarizing plate for bonding with a liquid crystal cell. In addition, it can be used as a protective film, a reflective sheet, a structural adhesive sheet, a photo adhesive sheet, a lane display adhesive sheet, an optical adhesive product, an adhesive for an electronic component, as well as a general commercial adhesive sheet product and a medical patch.

The polarizing plate of the present invention is characterized in that an adhesive layer made of an adhesive composition is laminated.

The thickness of the pressure-sensitive adhesive layer can be adjusted according to the adhesive force, it is usually preferably 3 to 100㎛, more preferably 10 to 100㎛.

Such a polarizing plate can be applied to all conventional liquid crystal display devices, and in particular, a polarizing plate in which an adhesive layer is stacked may constitute a liquid crystal display device including a liquid crystal panel provided on at least one side of a liquid crystal cell.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but these examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims. It is apparent to those skilled in the art that various changes and modifications can be made to the present invention, and such modifications and changes belong to the appended claims.

Example

Preparation Example 1 Preparation of Acrylic Copolymer

90 parts by weight of n-butyl acrylate (BA), 7 parts by weight of methyl acrylate (MA), 2-hydroxyethyl acrylate (2- HEA) 2 parts by weight and a monomer mixture consisting of 1 part by weight of acrylic acid (AA) was added and then 100 parts by weight of ethyl acetate (EA) as a solvent. Thereafter, nitrogen gas was added for 1 hour to remove oxygen, and the reactor was replaced, and the temperature was maintained at 62 ° C. After stirring the monomer mixture uniformly, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and reacted for 6 hours to prepare an acrylic copolymer having a weight average molecular weight of 600,000 or more.

Example 1

(1) pressure-sensitive adhesive composition

100 parts by weight of the acrylic copolymer A of Preparation Example 1, 0.2 parts by weight of hexamethylene diisocyanate adduct (COR-HXR: Nippon Polyurethane Co., Ltd.) of trimethylolpropane as a crosslinking agent, and 3- as a silane coupling agent, based on the solid content. 0.4 parts by weight of glycidoxypropyltrimethoxysilane (KBM-403, Shin-Etsu), 0.01 part by weight of dibutyltin dilaurate (DBTDL) as a crosslinking accelerator and 1-octyl-4-methylpyridinium hexafluorophosphate as an antistatic agent After mixing 2 parts by weight, the solid content was diluted to 28% to prepare a pressure-sensitive adhesive composition.

(2) adhesive sheet

The pressure-sensitive adhesive composition was dried on a film coated with a silicone release agent and then applied to have a thickness of 25 μm, and dried at 100 ° C. for 1 minute to form a pressure-sensitive adhesive layer. An adhesive sheet was prepared by laminating another release film thereon.

(3) polarizing plate with pressure-sensitive adhesive

After peeling the release film of the prepared pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer was laminated on an iodine-based polarizing plate having a thickness of 185 μm to prepare a polarizing plate with pressure-sensitive adhesive.

Example  2-6, Comparative example  1-4

To carry out the same as in Example 1, the components and contents of the pressure-sensitive adhesive composition was used as shown in Table 1. At this time, the content is parts by weight.

division Public
coalescence Cross-linking agent Silane
Coupling agent Crosslinking accelerator Antistatic agent
Viscosity COR-HXR KBM-403 DBTDL DMAP Viscosity (cP) Rate of change (%) Example 1 100 0.2 0.4 0.01 - 2 360 5 Example 2 100 0.2 0.4 0.02 - 2 390 9 Example 3 100 0.3 0.4 0.01 - 2 410 11 Example 4 100 0.3 0.4 0.02 - 2 380 15 Example 5 100 0.4 0.4 0.01 - 2 360 11 Example 6 100 0.5 0.4 0.01 - 2 430 14 Comparative Example 1 100 0.3 0.4 0.05 - 2 420 68 Comparative Example 2 100 0.1 0.4 0.005 - 2 320 10 Comparative Example 3 100 0.5 0.4 0.06 - 2 920 Gelation Comparative Example 4 100 0.3 0.4 - 0.01 2 400 15 COR-HXR: Hexamethylene diisocyanate adduct of trimethylolpropane (Japan Polyurethane Industry)
KBM-403: 3-glycidoxypropyltrimethoxysilane (Shin-Etsu)
DBTDL: Dibutyl Tin Dilaurate
DMAP: 4-dimethylaminopyridine
Antistatic Agent: 1-octyl-4-methylpyridinium hexafluorophosphate

Test Example

The physical properties of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive polarizing plate prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 2 below.

1. Storage stability (viscosity change)

The initial viscosity of the prepared pressure-sensitive adhesive composition and the viscosity after standing for 24 hours at room temperature were measured at 23 ° C. using a viscometer (Brookfield LVDV-II + B type (spindle no. 3, 30 rpm)). The rate of change (Δη) of the measured viscosity was calculated and evaluated based on the following criteria.

<Evaluation Criteria>

○: Δη <20%

×: 20% ≤ Δη

2. Gel fraction (%)

The prepared pressure-sensitive adhesive polarizing plate was cured at 23 ° C. and 65% RH for 2 days. About 0.25 g of the adhesive layer of the polarizing plate with an adhesive is affixed on the fixed 250 mesh wire mesh (100 mm x 100 mm), and it wraps so that a gel may not leak. After accurate weighing by precision balance, the wire mesh is immersed in 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 weighed. The gel fraction was calculated by the following equation 1 using the measured weight.

[Wherein, A is the weight of the wire mesh (g), B is the weight of the wire mesh with the adhesive layer (BA: adhesive weight, g), C is the weight of the dried wire mesh after immersion (CA: weight of the gelled resin, g )being].

3. Process stability

It was visually observed that the pressure-sensitive adhesive composition was uniformly applied to form a pressure-sensitive adhesive layer when the prepared pressure-sensitive adhesive composition was applied on a film coated with a silicone release agent to have a thickness of 25 μm.

<Evaluation Criteria>

(Circle): An adhesive composition is apply | coated uniformly and a uniform adhesive layer is formed.

X: An adhesive composition is not apply | coated uniformly and a nonuniform adhesive layer is formed.

4. Durability (heat and moisture resistant)

The pressure sensitive adhesive polarizing plate was cut into a size of 90 mm x 170 mm, the release film was peeled off, and the specimens were prepared by attaching the optical absorption axis at right angles to both surfaces of the glass substrate (110 mm x 190 mm x 0.7 mm). At this time, the applied pressure was 5 kg / cm &lt; 2 &gt;, and the clean room operation was performed so that bubbles or foreign matter would not occur. The heat resistance characteristics were observed whether bubbles or peeling occurred after 1000 hours at 80 ℃ temperature, and the heat-resistant characteristics were bubbles or peeling after 1000 hours at 60 ℃ temperature and 90% RH conditions Was observed. At this time, it was observed after leaving for 24 hours at room temperature immediately before evaluating the state of the specimen.

<Evaluation Criteria>

Ⓞ: No bubbles or peeling.

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

×: 10 ≤ air bubbles or peeling

5. Adhesive force (N / 25㎜)

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. After room temperature adhesiveness was left for 24 hours under 23 ° C and 50% RH, the warm adhesive strength was measured after 48 hours under 50 ° C and 50% RH, and then the universal tensile tester (UTM, Instron) was used. The pressure-sensitive adhesive layer was peeled off at a peeling rate of 300 mm / min and a peeling angle of 180 °, and measured. At this time, measurement was carried out under conditions of 23 캜 and 50% RH.

division Save
stability Gel fraction
(%) fair
stability durability Adhesion (N / 25㎜) Heat resistance Wet heat Room temperature Gaon Example 1 ○ 69 ○ ◎ ○ 2.1 9.3 Example 2 ○ 75 ○ ○ ○ 1.5 7.8 Example 3 ○ 71 ○ ◎ ○ 1.3 6.4 Example 4 ○ 78 ○ ◎ ○ 1.6 7.2 Example 5 ○ 74 ○ ○ ◎ 1.9 6.4 Example 6 ○ 72 ○ ◎ ◎ 1.2 5.8 Comparative Example 1 × 82 ○ △ × 1.8 7.5 Comparative Example 2 ○ 58 ○ ○ × 6.9 26.2 Comparative Example 3 × 89 × × × 1.5 9.1 Comparative Example 4 ○ 36 ○ ○ ○ 8.6 19.8

As shown in Table 2 above, the pressure-sensitive adhesive composition of Examples 1 to 6, including an acrylic copolymer, a crosslinking agent, and a Lewis acid crosslinking accelerator, and the initial viscosity and the rate of change of viscosity corresponding to the scope of the present invention are Comparative Examples 1 to 4 Compared with the pressure-sensitive adhesive composition of the durability and adhesion is good, the storage stability is excellent, it was confirmed that sufficient pot-life can be secured and the curing period can be shortened.

Claims (6)

It contains an acrylic copolymer, an isocyanate crosslinking agent and a Lewis acid crosslinking accelerator, and when the solid content is 28% by weight, its initial viscosity is 350-450 cP at 23 ° C. and the viscosity change rate after being left at 21-25 ° C. for 24 hours is 20. Pressure-sensitive adhesive composition of less than or equal to%.
The pressure-sensitive adhesive composition of claim 1, comprising 0.1 to 5 parts by weight of isocyanate-based crosslinking agent and 0.008 to 0.04 parts by weight of Lewis acid crosslinking accelerator based on 100 parts by weight of the acrylic copolymer based on the solid content.
The pressure-sensitive adhesive composition of claim 1, wherein the isocyanate-based crosslinking agent is at least one member selected from the group consisting of hexamethylene diisocyanate and its adducts, isocyanurates, and biurets.
The method of claim 1, wherein the Lewis acid is dibutyltin octoate, dibutyltin dioleyl maleate, dibutyltin dibutyl maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, Dibutyltin bistriethoxysilicate, Dibutyltin distearate, Dioctyl tin distearate, Dioctyl tin dilaurate, Dioctyl tin diacetate, Dibutyltin bisisononyl 3-meractopropionate, Di An adhesive composition which is at least one organic tin-based compound selected from the group consisting of butyltin bisisooctylthioglycol, dimethyltin bisisooctylthioglycol, dioctyltin bisisooctylthioglycol, and dilauryl tin bisoctylthioglycol.
The polarizing plate in which the adhesive layer which consists of an adhesive composition of any one of Claims 1-4 was laminated | stacked.
A liquid crystal display device comprising the polarizing plate of claim 5 on at least one side of the liquid crystal cell.