TWI637973B - Acrylic copolymer and adhesive composition containing same - Google Patents

Abstract

The invention discloses an acrylic copolymer and an adhesive composition including the acrylic copolymer. The adhesive composition can shorten the curing period to improve productivity, suppress viscosity changes to improve storage stability, and satisfy physical properties such as durability, high heat resistance, and reworkability by using a compound including the following Chemical Formula 2 Acrylic copolymer: Wherein, R ₁ is a C ₁ -C ₁₂ aliphatic hydrocarbon; and R ₂ and R ₃ are hydrogen, C ₁ -C ₁₂ aliphatic hydrocarbon, or C ₆ -C ₁₂ aromatic hydrocarbon, respectively.

Description

Acrylic copolymer and adhesive composition containing acrylic copolymer

The present invention relates to an adhesive composition which can shorten the curing period and improve the durability without reducing the stability of the liquid.

A liquid crystal display (LCD) having an LCD panel includes an LCD cell and a polarizing plate, which are adhered to both sides of the LCD panel via an adhesive layer.

Adhesives are used to satisfy physical properties such as reworkability and durability such as adhesion to a substrate, prevention of light leakage, and heat and humidity resistance. In addition, adhesives can be used to shorten the curing period, which is one of the physical factors that improve productivity.

Korean Patent Laid-Open No. 10-2010-0113487 discloses an adhesive composition obtained by using an acrylamide monomer having a hydroxyl group as a cross-linking agent to shorten the curing period and still retain the physical properties of a conventional adhesive .

However, although the conventional adhesive composition has the advantage of a short curing period, its reactivity in a liquid can increase, resulting in poor liquid stability. In addition, due to the current trend to make thinner and weaker polarizer protective films and increase the stress caused by the high stretching of polarizers, the heat resistance of polarizers is deteriorated, so that traditional adhesives cannot effectively improve the heat resistance of polarizers. Sexual deterioration.

Therefore, the present invention solves the problems occurring in the above-mentioned conventional knowledge, and an object of the present invention is to provide an adhesive composition that can improve liquid stability and shorten curing period even without adding a cross-linking accelerator, which is sufficient to meet high requirements. Heat resistance is a property necessary for the adhesive composition of a polarizer.

To achieve this, here is provided an acrylic copolymer comprising a compound of Chemical Formula 1:

Wherein, R ₁ is a C ₁ -C ₁₂ aliphatic hydrocarbon; and R ₂ and R ₃ are hydrogen, C ₁ -C ₁₂ aliphatic hydrocarbon, or C ₆ -C ₁₂ aromatic hydrocarbon, respectively.

Here, in the compound of Chemical Formula 1, R ₁ may be C ₁ -C ₄ alkyl; and R ₂ and R ₃ may each be a separate hydrogen, C ₁ -C ₄ alkyl, or C ₆ -C ₈ benzene Or benzyl.

The compound of Chemical Formula 1 may be at least one selected from the group consisting of compounds of Chemical Formulas 2 to 5:

[Chemical Formula 4]

The acrylic copolymer may include a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms and a compound of Chemical Formula 1.

The content of the compound of Chemical Formula 1 may be 0.1 to 10 parts by weight based on 100 parts by weight of the (meth) acrylate monomer of the alkyl group having 1 to 12 carbon atoms.

According to another object of the present invention, there is provided an adhesive composition including the acrylic copolymer.

The adhesive composition may further include a cross-linking agent.

The invention discloses an adhesive composition which can shorten the curing period and can improve the durability without reducing the liquid stability.

Next, the details of the present invention will be described below.

An acrylic copolymer according to the present invention includes the compound of the following Chemical Formula 1: [Chemical Formula 1]

Wherein, R1 is a C ₁ -C ₁₂ aliphatic hydrocarbon; and R ₂ and R ₃ are respectively hydrogen, a C ₁ -C ₁₂ aliphatic hydrocarbon, or a C ₆ -C ₁₂ aromatic hydrocarbon.

Preferably, in the compound of Chemical Formula 1, R1 may be C ₁ -C ₄ alkyl; and R ₂ and R ₃ may each be a separate hydrogen, C ₁ -C ₄ alkyl, or C ₆ -C ₈ benzene Or benzyl.

Most preferably, the compound of Chemical Formula 1 may be at least one selected from the group consisting of the following Chemical Formulas 2 to 5:

The acrylic copolymer of the present invention preferably includes a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms and the compound of the above Chemical Formula 1. Here, (meth) acrylate means an acrylate and a methacrylate.

The compound of Chemical Formula 1 contains a functional group to interact in a molecule During the reaction, it plays the role of basic catalyst and active group.

More specifically, the compound of Chemical Formula 1 includes an amide group and a hydroxyl group. The acrylic copolymer including the compound can accelerate the crosslinking reaction between the crosslinking agent and the crosslinkable monomer to shorten the curing period of the adhesive.

In addition, although the compound of Chemical Formula 1 contains an amide group as a catalyst and a hydroxyl group to perform a cross-linking reaction with the amide group in its molecule, solvation and decomposition into the amide group and the hydroxyl group can ensure liquid stability in a solvent.

In addition, after the structure of the compound is cured, the cross-linking structure is formed by cross-linking between the main chains, rather than the cross-linking agent formed by the side chains, which leads to an increase in cross-linking density, thereby improving heat resistance. .

Alkyl (meth) acrylate monomers having 4 to 12 carbon atoms are (meth) acrylates derived from fatty alcohols having 4 to 12 carbon atoms, examples of which are n- (meth) acrylate Ester, butyl 2- (meth) acrylate, t- (meth) acrylate, pentyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and the like. They can be used alone or in combination of two or more. Among these, n- (meth) acrylate, 2-ethylhexyl (meth) acrylate, or a mixture thereof is preferred.

The content of the compound of Chemical Formula 1 may be 0.1 to 10 parts by weight, and preferably 0.5 to 3 parts by weight based on 100 parts by weight of a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms. Serving. If the content of the compound is less than 0.1 parts by weight, the acceleration effect of the crosslinking reaction will be poor, and the curing will not be shortened because the degree of crosslinking is reduced. Period and improve durability. If the content of the compound exceeds 10 parts by weight, the cross-linking reaction becomes fast, the liquid stability becomes poor, and the cohesive force becomes too strong, so that the adhesive force becomes worse, resulting in the defect of peeling under heat resistance conditions.

In addition, the acrylic copolymer of the present invention may further include a polymerizable monomer having a crosslinkable functional group in addition to the crosslinkable functional group of the compound of Chemical Formula 1. The polymerizable monomer can provide cohesion or adhesion through chemical bonding with the following crosslinking agents. Examples thereof may include a monomer having a hydroxyl group, a monomer having a carboxyl group, a monomer having an amide group, a monomer having a tertiary amine group, and the like. They can be used alone or in combination of two or more.

Examples of the monomer having a hydroxyl group are hydroxyethyl 2- (meth) acrylate, hydroxypropyl 2- (meth) acrylate, hydroxybutyl 2- (meth) acrylate, 4-hydroxybutyl (methyl) Acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, having 2 to 4 carbon atoms Hydroxyalkylene glycol (meth) acrylate, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl ethylene Ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl vinyl ether, 10-hydroxydecyl vinyl ether, and the like. Among these, 4-hydroxybutyl vinyl ether is preferred.

Examples of the monomer having a carboxyl group are monovalent acids such as (meth) acrylates, crotonic acid, and the like; divalent acids such as maleic acid, itaconic acid, fumaric acid, and the like, and monoalkanes thereof Base ester; 3- (meth) acryloyl propionic acid; succinic anhydride ring-opening adduct of 2-hydroxyalkyl (meth) acrylate of alkyl group having 2-3 carbon atoms, having 2-4 Carbon atom alkylene hydroxyalkylene glycol (meth) acrylate succinic acid Anhydride ring-opening adducts and compounds obtained by succinic anhydride ring-opening adducts and caprolactone adducts of 2-hydroxyalkyl (meth) acrylates of alkyl groups having 2-3 carbon atoms ; And the like. Among these, (meth) acrylate is preferable.

Examples of the monomer having an amide group are (meth) acrylamide, hydroxyethylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, 3-hydroxypropyl (meth) acrylamide, 4-hydroxybutyl (meth) acrylamide, 6-hydroxyhexyl (meth) acrylamide, 8-hydroxyoctyl (meth) acrylamide, 2-hydroxyhexyl (meth) acrylamide, and the like. Among these, (meth) acrylamide is preferred.

Examples of the monomer having a tertiary amino group are N, N- (dimethylamino) ethyl (meth) acrylate, N, N- (diethylamino) ethyl (meth) acrylate, N, N- (dimethylamino) propyl (meth) acrylate, and the like.

Based on 100 parts by weight of all monomers used to prepare the acrylic copolymer, the content of the polymerizable monomer having a crosslinkable functional group is preferably 0.1 to 10 parts by weight, and most preferably 0.5 to 3 Parts by weight. If it is less than 0.1 parts by weight, the cohesive force of the adhesive will be reduced, resulting in poor durability. If it exceeds 10 parts by weight, the adhesive force of the adhesive is reduced due to a high gel fraction and a problem of durability is caused.

In addition, without reducing the adhesive force of the adhesive, it may further include other polymerized monomers than the above monomers. For example, all the monomers used to prepare the acrylic copolymer are 100 weight The content is based on not more than 40 parts by weight.

Among these polymerized monomers, an aromatic monomer having a high glass transition temperature (Tg) to increase the glass transition temperature or an aromatic monomer for preventing light leakage.

The method for preparing the copolymer is not particularly limited. Copolymers can be prepared by conventional methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. Among these, solution polymerization is preferred. In addition, solvents, polymerization initiators, chain transfer agents for controlling molecular weight, and the like commonly used in conventional polymerization can also be used.

The weight average molecular weight (in terms of polystyrene, Mw) of the copolymer, as measured by colloidal permeation chromatography, is 50,000 to 2,000,000, and preferably 400,000 to 2,000,000. If the weight average molecular weight of the copolymer is less than 50,000, the adhesion between the copolymers will be insufficient, resulting in a problem of adhesion durability. If the weight average molecular weight of the copolymer exceeds 200,000, a large amount of a diluting solvent is required to ensure the processability at the time of coating.

Further, the present invention is characterized in that the adhesive composition includes an acrylic copolymer. The adhesive composition may further include a cross-linking agent.

The cross-linking agent is a composition used to appropriately cross-link the copolymer to improve the cohesiveness of the adhesive, and the type of the cross-linking agent is not particularly limited. Examples of the cross-linking agent include isocyanate-based compounds, epoxy-based compounds, and the like, and these may be used alone or as a mixture of two or more.

Examples of the isocyanate-based compound are diisocyanate compounds such as toluene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isopropyl Furone diisocyanate, tetramethylxylene diisocyanate, and naphthalene diisocyanate; one plus obtained by reacting 3 mol diisocyanate compound with 1 mol polyol compound such as trimethylolpropane 3 mol diisocyanate compound A monoisocyanurate obtained by self-condensing, a diisocyanate obtained by condensing a diisocyanate urea obtained from 2 moles of a diisocyanate compound of 3 moles and a remaining 1 mole of a diisocyanate compound Urea bodies, and polyfunctional isocyanate compounds having three functional groups, such as triphenylmethane triisocyanate and methylene diisocyanate; and the like.

Examples of the epoxy resin-based compound include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polypropylene glycol diethylene glycol. Glycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, glycerol Polydiether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromo neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl Ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris (glycidyl) isocyanurate, tris (glycidyloxyethyl) iso Cyanurate, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, and such as.

As for the crosslinking agent, the melamine-based compound may be used alone or as a mixture with two or more isocyanate-based compounds and epoxy resin-based compounds.

Examples of the melamine-based compound are hexamethylolmelamine, hexamethoxymethylmelamine, hexabutoxymethylmelamine, and the like.

Based on 100 parts by weight of the copolymer, in terms of solid content, the content of the crosslinking agent is preferably 0.1 to 5 parts by weight and most preferably 0.1 to 2 parts by weight. If cross-linked The content of the agent is less than 0.1 parts by weight, the cohesive force is lowered due to insufficient crosslinking degree, resulting in poor durability, such as air bubbles, and poor cuttability. If the content of the cross-linking agent exceeds 5 parts by weight, the adhesion may be deteriorated due to excessive cross-linking reactions, resulting in defects in durability such as peeling.

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

The type of the silane coupling agent is not particularly limited. Examples of the silane coupling agent are vinylchlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-cyclo Propoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidyl Oxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloyloxymethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-acryloyloxypropyltrimethoxysilane, N-2 -(Aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl)- 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-di Methyl-butylene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxy Silane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatepropyltriethoxysilane , And the like. They can be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 0 to 10 parts by weight and most preferably 0.005 to 5 parts by weight based on 100 parts by weight of the copolymer. If the content of the silane coupling agent exceeds 10 parts by weight, the durability will be deteriorated.

The adhesive composition may further include, in addition to the above composition, such as a tackifier resin, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, a defoamer, a filler, a light stabilizer, and an antistatic Additives to adjust the adhesion, cohesion, viscosity, elastic modulus, glass transition temperature, antistatic properties, and the like required for the adhesive composition.

The adhesive composition of the present invention can be used as an adhesive for combining a polarizing plate and a liquid crystal cell, or an adhesive for a surface protection film. In addition, the adhesive composition of the present invention can be used for protective films, reflective sheets, adhesive sheets for molding, adhesive sheets for photography, adhesive sheets for marking land, optical adhesive products, and electronics. Adhesives for products, adhesive sheet products for general advertising and patches for medical use.

The preferred embodiments are provided to help understand the present invention, and the examples described below are only for presenting the present invention and not for limiting the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Example 1: Preparation of acrylic copolymer Example 1-1

89.5 parts by weight of n-butyl acrylate (BA), 10 parts by weight of propylene A methyl ester (MA) and a monomer mixture of 2 parts by weight of a compound of formula 2 were placed in a 1 liter reactor with a cooling device to facilitate the reflux of nitrogen and control of temperature, and then 100 parts by weight of acetic acid Ethyl acetate (acetone) was added as a solvent. After that, it was purged with nitrogen for 1 hour to remove oxygen, and the temperature was maintained at 62 ° C. Stir the monomer mixture evenly. Then, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, followed by a reaction for 8 hours to prepare an acrylic copolymer having a weight average molecular weight of about 1,000,000.

Examples 1-1 to 1-10 and Comparative Examples 1 to 4

The acrylic copolymer was prepared by the same method as in Production Example 1, and the combination shown in Table 1 below was used.

Examples 2-1 to 2-13 and comparative examples 5 to 9

The adhesive composition was prepared by mixing the composition of the composition as shown in Table 2 below, and then diluted with ethyl acetate. Each of the adhesive composition prepared as above was coated on a release film coated with a silicon release agent to have a thickness of 25 μm, and then dried at 100 ° C. for 1 minute to form an adhesive layer.

The formed adhesive layer was attached to a 185 μm-thick iodine-based polarizing plate through an adhesive process to manufacture an adhesive-attached polarizing plate.

Test case

The characteristics of the adhesive composition, the adhesive sheet, and the adhesive-attached polarizing plate obtained by this example and the comparative example were measured by the following methods, and the measurement results are recorded in Table 3.

1. Storage stability (viscosity change,%)

A viscometer (Brookfield LVDV-II + B (rotor code 3, 30 rpm)) was used to measure the initial viscosity of the adhesive composition and the viscosity of the adhesive composition after being left at room temperature for 24 hours, and calculate the viscosity Change (Δη).

<Evaluation criteria>

○: Δη <10%

Δ: 10% Δη <20%

×: 20% Δη

2. During curing

When the manufactured adhesive sheet was cured at 23 ° C and 65% RH for 1 to 10 days, the gel fraction was measured daily as described below. The number of days of curing is extended until the gelation rate no longer increases, that is, the curing period is judged accordingly.

The adhesive layer of about 0.25g of adhesive sheet was fixed on a 250-mesh wire mesh (100mm X 100mm), and the wire mesh was wrapped so that the gel would not escape from it. The weight was accurately measured using a precision balance, and the wire mesh was immersed in an ethyl acetate solution for 3 days. Remove the soaked wire mesh, and then a small amount The ethyl acetate solution was rinsed, dried at 120 ° C for 24 hours, and then weighed. The measured weight is used to calculate the gel fraction by Equation 1. Determine the curing period based on the time point at which the calculated gel fraction falls within the range of 70% to 80% and no change with time is observed: [Equation 1] Gel fraction (%) = (CA) / (BA) X 100

[In Equation 1, A is the weight of the metal mesh (g); B is the weight of the adhesive layer fixed to the metal mesh (BA: weight of the adhesive layer, g); and C is the metal mesh after soaking and drying Weight (CA: weight of gel resin, g)].

3.Durability (heat resistance, damp heat resistance)

The manufactured polarizer with an adhesive was cut into a size of 90 mm × 170 mm to prepare a sample, and the release film was peeled off therefrom, and then the polarizer was attached to both sides of the glass substrate (110 mm × 190 mm × 0.7 mm) The light absorption axes of the polarizing plates are made orthogonal to each other. Here, a pressure of 5 kg / cm ² is applied, and it is performed in a clean room to avoid the generation of bubbles or foreign materials. In order to measure the heat resistance, the sample was left at a temperature of 80 ° C for 1000 hours, and then, it was observed whether blistering or peeling occurred. In order to measure the humidity and heat resistance, the samples were placed under the conditions of 60 ° C and 90% RH for 1000 hours, and then observed whether blistering or peeling occurred. Here, the sample is left at room temperature for 24 hours before the sample is evaluated.

<Evaluation criteria>

◎: No bubbles or peeling:

○: Number of bubbles or peeling <5

Δ: 5 Number of bubbles or peeling <10

×: 10 Number of bubbles or peeling

4. Reworkability

The manufactured polarizing plate with an adhesive was cut into 25 mm × 100 mm, and then the release film was peeled. This polarizing plate was laminated to a glass substrate (Corning # 1737, Corning Corporation) by applying a pressure of 0.25 MPa, and then subjected to high pressure treatment at 5 atm and 50 ° C for 20 minutes to prepare a sample for evaluation. To measure heat reworkability, the samples were stored in an oven at 80 ° C for 10 hours, and then taken out. Then, the sample was left at room temperature for 120 hours, and then the adhesive layer was peeled off at a speed of 1.3 cm / s. In order to measure the resistance to moist heat rework, the samples were stored in an oven at 60 ° C and 90 RH% for 12 hours, and then taken out. Then, the sample was left at room temperature for 120 hours, and then the adhesive layer was peeled off at a speed of 1.3 cm / s. Based on the following criteria, the hot rework resistance and the hot and humid rework resistance were evaluated.

<Evaluation criteria>

○: In the case of heat-resistant reworkability and moisture-heat reworkability, no adhesive agent remained on the glass substrate and the adhesive layer was completely peeled off without tearing the polarizing plate.

Δ: In the case of heat-resistant reworkability or moisture-heat reworkability, a small amount of adhesive remained on the glass substrate and the adhesive layer was completely peeled off without tearing the polarizing plate.

×: In the case of any one of heat-resistant reworkability and moisture-heat reworkability, a large amount of adhesive remained on the glass substrate and the polarizing plate was torn when the adhesive layer was peeled off.

[table 3]

As can be seen from Table 3, the adhesive compositions of Examples 2-1 to 2-13 including compounds of Chemical Formula 1 according to the present invention have better liquid stability and shorter than the adhesive compositions of Comparative Examples 5 to 9. Curing time, durability (heat resistance and humidity and heat resistance), and reworkability.

As described above, the adhesive composition of the present invention can improve the liquid stability and shorten the curing period without adding a cross-linking accelerator, and has a satisfying high heat resistance. It is the current adhesive composition for polarizing plates. Required characteristics.

Claims (5)

An acrylic copolymer composed of a compound of Chemical Formula 1 and a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms. Based on 100 parts by weight of acrylate monomer, the content of the compound of Chemical Formula 1 is 0.1 to 10 parts by weight: Wherein, R ₁ is a C ₁ -C ₁₂ aliphatic hydrocarbon; and R ₂ and R ₃ are hydrogen, C ₁ -C ₁₂ aliphatic hydrocarbon, or C ₆ -C ₁₂ aromatic hydrocarbon, respectively. The acrylic copolymer according to item 1 of the scope of patent application, wherein in the compound of Chemical Formula 1, R ₁ is a C ₁ -C ₄ alkyl group; and R ₂ and R ₃ are separate hydrogen and C ₁ -C ₄ Alkyl, or C ₆ -C ₈ phenyl or benzyl. The acrylic copolymer according to item 2 of the scope of patent application, wherein the compound of Chemical Formula 1 is at least one selected from the group consisting of compounds of Chemical Formulas 2 to 5: An adhesive composition includes the acrylic copolymer according to any one of claims 1 to 3 of the patent application scope. The adhesive composition according to item 4 of the patent application scope further includes a cross-linking agent.