KR102443988B1 - Acryl-based adhesive composition, polarizing plate and display device - Google Patents

Abstract

The present invention, 100 parts by weight of an acrylic copolymer (A) having a branched structure having a weight average molecular weight of 300,000 to 1,000,000 g/mol; And it relates to an acrylic pressure-sensitive adhesive composition comprising 5 to 30 parts by weight of an acrylic copolymer (B) having a linear structure having a weight average molecular weight of 1,500,000 to 2,000,000 g/mol, a polarizing plate and a display device manufactured using the same.

Description

Acrylic pressure-sensitive adhesive composition, polarizing plate, and display device {ACRYL-BASED ADHESIVE COMPOSITION, POLARIZING PLATE AND DISPLAY DEVICE}

The present invention relates to an acrylic pressure-sensitive adhesive composition, a polarizing plate, and a display device, and more particularly, to an acrylic pressure-sensitive adhesive composition having a low viscosity characteristic, excellent coating property, durability, in particular, excellent room temperature and low humidity durability, and a polarizing plate manufactured using the same; It relates to a display device.

In general, a liquid crystal display device (LCD) includes a liquid crystal cell containing liquid crystal and a polarizing plate, and an adhesive layer is used to attach the liquid crystal cell and the polarizing plate. Acrylic resins, rubbers, urethane resins, silicone resins, or EVA (Ethylene Vinyl Acetate) are used as adhesives for attaching polarizing plates that form the adhesive layer. Among them, acrylic resins with transparency, oxidation resistance and yellowing resistance are used as the base. Adhesives are widely used.

In the case of the acrylic pressure-sensitive adhesive for a polarizing plate, it is preferable to use an acrylic resin having a high weight average molecular weight in order to improve durability and curing efficiency. This is because, when an acrylic resin having a weight average molecular weight of 1 million or less is used, the curing efficiency is lowered and the curing rate is slowed, and the cohesive force and curing degree of the pressure-sensitive adhesive are lowered under high temperature or high temperature/high humidity conditions, thereby reducing durability.

However, when an acrylic resin having a high weight average molecular weight is used, there is a problem in that the viscosity of the coating solution increases and workability decreases. The viscosity of the coating solution can be adjusted by lowering the solid content in the coating solution. However, when the adhesive layer is formed using a coating solution with a low solid content as described above, the manufacturing cost increases and productivity decreases, and it is difficult to precisely control the thickness of the adhesive layer. There is a problem.

Accordingly, as a method for increasing the solid content while maintaining the viscosity of the coating solution at an appropriate level, a method of mixing a low molecular weight substance or increasing the content of an unreacted curing agent has been proposed. However, in the case of mixing the low molecular weight material, the adhesive layer is easy to deform, so when the polarizing plate is stored in a roll form in the polarizing plate manufacturing process, the adhesive layer is easily pressed and deformed (pit) occurs when the polarizing plate is cut. There is a problem in that the pressure-sensitive adhesive protrudes from the surface, and thus the polarizing plate is easily contaminated. In addition, when the content of unreacted curing agent is increased, when a certain period of time has elapsed after the polarizing plate is attached to the liquid crystal panel, the adhesive strength is greatly increased, making it difficult to rework, and the effect of the residual curing agent changes over time of the adhesive properties. There is a problem that it is easy to become.

Therefore, there is a demand for the development of an acrylic pressure-sensitive adhesive composition for a polarizing plate that can be coated at a high solid content without a significant increase in coating viscosity, and can achieve excellent curing efficiency, cohesive force, re-peelability and durability.

The present invention is to solve the above problems, and to provide an acrylic pressure-sensitive adhesive composition having excellent coating properties, re-peelability properties and durability.

In addition, the present invention is to provide a polarizing plate including a pressure-sensitive adhesive layer formed by the acrylic pressure-sensitive adhesive composition as described above and a display device including the same.

In one aspect, the present invention is formed by polymerizing a first monomer mixture comprising a monomer represented by the following [Formula 1], a (meth)acrylic monomer having a crosslinkable functional group, and an alkyl (meth)acrylate-based monomer 100 parts by weight of an acrylic copolymer (A) having a branched structure; and 5 to 30 parts by weight of an acrylic copolymer (B) having a linear structure formed by polymerizing a second monomer mixture including a (meth)acrylic monomer having a crosslinkable functional group and an alkyl (meth)acrylate monomer. A pressure-sensitive adhesive composition is provided. In this case, the acrylic copolymer (A) has a weight average molecular weight of 300,000 to 1,000,000 g/mol, and the acrylic copolymer (B) has a weight average molecular weight of 1,500,000 to 2,000,000 g/mol.

[Formula 1]

R ¹ -CH=CR ² -(C=O)-OXY

In Formula 1, R ¹ is hydrogen, a C1 to C6 alkyl group or a C2 to C6 alkenyl group, R ² is hydrogen or a C1 to C10 alkyl group, X is a single bond, a C1 to C10 alkylene group, a C2 to C10 alkenylene group , ether, ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.

In another aspect, the present invention, a polarizing film; and an adhesive layer formed on one or both sides of the polarizing film and comprising a cured product of the acrylic pressure-sensitive adhesive composition according to the present invention.

In another aspect, the present invention provides a display device including the polarizing plate according to the present invention.

The acrylic pressure-sensitive adhesive composition according to the present invention uses a mixture of a branched polymer having a specific weight average molecular weight and a linear polymer, so that it has a low viscosity characteristic even at a relatively high solid content compared to the prior art, and thus has excellent coating properties, re-peelability and Excellent durability.

In addition, the polarizing plate including the pressure-sensitive adhesive layer formed using the acrylic pressure-sensitive adhesive composition according to the present invention exhibits excellent durability even under high temperature, high temperature/high humidity, and room temperature and low humidity conditions, and has excellent re-peelability and adhesiveness.

Hereinafter, the present invention will be described in detail.

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless specifically stated otherwise.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In this specification, "(meth)acryl" is a generic term for acryl and methacryl. For example, (meth)acrylate includes methacrylate and acrylate, and (meth)acrylic acid includes acrylic acid and methacrylic acid.

In this specification, "X to Y" which shows a range means "X or more and Y or less".

As used herein, "branched polymer structure" refers to a polymer structure having two or more long chains grown in different directions.

As a result of repeated research to develop an acrylic pressure-sensitive adhesive composition having a low viscosity even when the solid content is high and having excellent durability and re-peelability, the present inventors have a branched structure acrylic copolymer having a specific weight average molecular weight and a linear structure It was found that the above object can be achieved by using the acrylic copolymer of a specific content, and the present invention has been completed.

Hereinafter, the acrylic pressure-sensitive adhesive composition according to the present invention will be described in detail.

adhesive composition

The acrylic pressure-sensitive adhesive composition according to the present invention includes 100 parts by weight of an acrylic copolymer (A) having a branched structure having a weight average molecular weight of 300,000 to 1,000,000 g/mol and a linear acrylic copolymer having a weight average molecular weight of 1,500,000 to 2,000,000 g/mol (B) 5 to 30 parts by weight.

Hereinafter, each component of the acrylic adhesive composition of this invention is demonstrated concretely.

(1) Acrylic copolymer of branched polymer structure (A)

The acrylic copolymer (A) of the branched polymer structure is a first monomer mixture comprising a monomer represented by the following [Formula 1], a (meth)acrylic monomer having a crosslinkable functional group, and an alkyl (meth)acrylate-based monomer It is formed by polymerization of

[Formula 1]

R ¹ -CH=CR ² -(C=O)-OXY

In Formula 1, R ¹ is hydrogen, a C1 to C6 alkyl group or a C1 to C6 alkenyl group, R ² is hydrogen or a C1 to C10 alkyl group, X is a single bond, a C1 to C10 alkylene group, a C2 to C10 alkenylene group , ether, ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.

The monomer represented by [Formula 1] is for forming an acrylic copolymer having a branched polymer structure. Conventionally, acrylic copolymers having a linear polymer structure in which monomers are polymerized in one long chain form have been mainly used as acrylic copolymers used in pressure-sensitive adhesives for polarizing plates. However, when only the acrylic copolymer having such a linear polymer structure is used, as the weight average molecular weight increases, the viscosity increases as well, resulting in poor workability.

However, when the acrylic copolymer is formed by adding the monomer represented by [Formula 1], a copolymer having a non-linear branched polymer structure is prepared. Specifically, the monomer of [Formula 1] has two or more ethylene groups, so radical formation is possible in free radical polymerization, and chains can grow in different directions, so branches having two or more chains with different growth directions type polymer is formed. The acrylic copolymer having such a branched polymer structure has lower viscosity characteristics than the acrylic copolymer having a linear polymer structure having the same weight average molecular weight. Therefore, when the acrylic copolymer having a branched polymer structure is used, excellent coating properties can be realized even when the solid content in the pressure-sensitive adhesive composition is increased.

Specific examples of the monomer represented by the [Formula 1] include allyl methacrylate, allyl acrylate, methallyl methacrylate, methallyl acrylate, 3-butenyl acrylate, but-3-enyl-2-methylprop-2-enoate, 2-allyloxyethyl 2-allyloxyethyl acrylate, 2-allyloxyethyl methacrylate, 3-allyloxypropyl methacrylate, 3-allyloxypropyl acrylate, 2-allyl 2-allyloxyethoxyethyl methacrylate, 2-allyloxyethoxyethyl acrylate, cyclohex-2-enyl acrylate, cyclo-hex -2-en-1-yl-2-methylprop-2-enoate (cyclohex-2-en-1-yl 2-methylprop-2-enoate) and 3-vinylcyclohex-2-enyl acrylate ( 3-vinylcyclohex-2-enyl acrylate) may be at least one selected from the group consisting of, but is not limited thereto. The monomer represented by Formula 1 may be included in an amount of 0.01 to 1 parts by weight, preferably 0.05 to 0.8 parts by weight, more preferably 0.1 to 0.6 parts by weight based on 100 parts by weight of the first monomer mixture. When the content of the monomer represented by [Formula 1] is less than 0.01 parts by weight, it is difficult to prepare a copolymer having low viscosity characteristics. difficult to control

On the other hand, the (meth)acrylic monomer having the crosslinkable functional group is for improving the durability, adhesive force and cohesive force of the pressure-sensitive adhesive, for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer or a nitrogen-containing monomer, etc., but limited thereto it's not going to be Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, or 2-hydroxypropylene glycol (meth)acrylate, and examples of the carboxyl group-containing monomer include is (meth)acrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, acrylic acid duplex, itaconic acid, maleic acid and maleic anhydride. Examples of the nitrogen-containing monomer include (meth)acrylamide, N-vinyl pyrrolidone, or N-vinyl caprolactam, but is not limited thereto.

The (meth)acrylic monomer having the crosslinkable functional group may be included in an amount of 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the first monomer mixture. . When the content of the (meth)acrylic monomer having a crosslinkable functional group satisfies the above range, better adhesion and durability may be obtained.

On the other hand, the alkyl (meth) acrylate-based monomer preferably includes an alkyl group having 2 to 14 carbon atoms. This is because, when the alkyl group included in the alkyl (meth) acrylate monomer becomes too thick, the cohesive force of the pressure-sensitive adhesive is lowered, and it may be difficult to control the glass transition temperature (Tg) or the adhesiveness. For example, examples of the alkyl (meth) acrylate-based monomer include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate ) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate, and in the present invention, one or two of the above A mixture of the above may be used.

The alkyl (meth) acrylate-based monomer may be included in an amount of 84 parts by weight to 99.89 parts by weight, preferably 89.2 to 98.95 parts by weight, more preferably 94.4 to 98.9 parts by weight, based on 100 parts by weight of the first monomer mixture. have. When the content of the alkyl (meth) acrylate-based monomer satisfies the above range, excellent adhesion and durability may be obtained.

According to one embodiment, the acrylic copolymer (A) having the branched polymer structure, based on 100 parts by weight of the first monomer mixture, 84 parts by weight to 99.89 parts by weight of the alkyl (meth) acrylate-based monomer, 0.1 to 15 It may be formed by polymerizing a first monomer mixture comprising a (meth)acrylic monomer having a crosslinkable functional group in parts by weight and a monomer represented by 0.01 to 1 parts by weight of [Formula 1].

The acrylic copolymer (A) having a branched polymer structure according to the present invention may be prepared by mixing each of the above-described monomers to prepare a monomer mixture, and then polymerizing the same. In this case, the polymerization method is not particularly limited, and various polymerization methods known in the art may be used, for example, polymerization methods such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. A polymerization initiator, molecular weight control, etc. may be additionally added during the polymerization, and the input timing of each component is not particularly limited. That is, the components may be added in batches, or may be divided and added several times.

In the present invention, in particular, the acrylic copolymer (A) having a branched polymer structure can be prepared by using a solution polymerization method, and the solution polymerization is performed by adding an initiator, a molecular weight regulator, etc. in a state in which each monomer is uniformly mixed. , it is preferably carried out at a polymerization temperature of 50 °C to 140 °C. Examples of the initiator that can be used in this process include azo initiators such as azobisisobutyronitrile or azobiscyclohexane carbonitrile; and/or a conventional initiator such as a peroxide such as benzoyl peroxide or acetyl peroxide, and one or a mixture of two or more thereof may be used, but is not limited thereto. In addition, as the molecular weight modifier, mercaptans such as t-dodecyl mercaptan or n-dodecyl mercaptan, defentin, or terpenes of t-terpene, chloroform, or a halogenated hydrocarbon of carbon tetrachloride, or pentaerythritol Tetrakis (3-mercapto propionate) may be used, but is not limited thereto.

On the other hand, in the present invention, it is preferable that the weight average molecular weight of the acrylic copolymer (A) of the branched polymer structure is 300,000 to 1,000,000 g/mol. When the weight average molecular weight of the acrylic copolymer (A) having a branched structure is less than 300,000 g/mol, the cohesive force of the adhesive is insufficient due to the decrease in curing efficiency, and the re-peelability property is deteriorated, and the durability under high temperature or high temperature/high humidity environment is deteriorated. There is a problem, and when it exceeds 1,000,000 g/mol, it is difficult to prepare a uniform adhesive layer due to poor coating properties.

(2) acrylic copolymer having a linear structure (B)

The acrylic copolymer (B) having a linear polymer structure is formed by polymerizing a second monomer mixture including a (meth)acrylic monomer having a crosslinkable functional group and an alkyl (meth)acrylate monomer.

The (meth)acrylic monomer having the crosslinkable functional group may include, for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, or a nitrogen-containing monomer, but is not limited thereto. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, or 2-hydroxypropylene glycol (meth)acrylate, and examples of the carboxyl group-containing monomer include is (meth)acrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, acrylic acid duplex, itaconic acid, maleic acid and maleic anhydride. Examples of the nitrogen-containing monomer include (meth)acrylamide, N-vinyl pyrrolidone, or N-vinyl caprolactam, but is not limited thereto.

The (meth)acrylic monomer having the crosslinkable functional group may be included in an amount of 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the second monomer mixture. . When the (meth)acrylic-based content having a crosslinkable functional group in the acrylic copolymer (B) having a linear polymer structure satisfies the above range, superior adhesive strength and durability may be obtained.

On the other hand, the alkyl (meth) acrylate-based monomer preferably includes an alkyl group having 2 to 14 carbon atoms. For example, examples of the alkyl (meth) acrylate-based monomer include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate ) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate, and in the present invention, one or two of the above A mixture of the above may be used.

The alkyl (meth) acrylate-based monomer may be included in an amount of 85 to 99.9 parts by weight, preferably 90 to 99 parts by weight, more preferably 95 to 99 parts by weight, based on 100 parts by weight of the second monomer mixture. have. When the content of the alkyl (meth)acrylate monomer in the acrylic copolymer (B) having a linear polymer structure satisfies the above range, excellent adhesion and durability can be obtained.

According to one embodiment, the acrylic copolymer (A) having a linear polymer structure is, based on 100 parts by weight of the second monomer mixture, 85 parts by weight to 99.9 parts by weight of an alkyl (meth)acrylate-based monomer and 0.1 to 15 parts by weight. It may be formed by polymerizing a second monomer mixture including a (meth)acrylic monomer having a negative crosslinkable functional group.

The acrylic copolymer (B) having a linear polymer structure according to the present invention may be prepared by mixing each of the above-described monomers to prepare a monomer mixture, and then polymerizing the same. In this case, the polymerization method is not particularly limited, and various polymerization methods known in the art may be used, for example, polymerization methods such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. A polymerization initiator, a molecular weight regulator, etc. may be additionally added during the polymerization, and the input timing of each component is not particularly limited. That is, the components may be added in batches, or may be divided and added several times. On the other hand, the types of the polymerization initiator and molecular weight regulator are the same as those described in the acrylic copolymer (A) having a branched polymer structure.

On the other hand, in the present invention, it is preferable that the weight average molecular weight of the acrylic copolymer (B) of the linear polymer structure is 1,500,000 to 2,000,000 g/mol. When the weight average molecular weight of the acrylic copolymer (B) having a linear polymer structure is less than 1,500,000 g/mol, there is a problem in that durability is deteriorated. difficult to manufacture.

On the other hand, the acrylic copolymer (B) of the linear polymer structure is included in an amount of 5 to 30 parts by weight based on 100 parts by weight of the acrylic copolymer (A) having the branched polymer structure. When the content of the acrylic copolymer (B) having a linear polymer structure is less than 5 parts by weight, the effect of improving durability at room temperature and low humidity conditions measured after the moist heat test is not sufficient, and when it exceeds 30 parts by weight, high viscosity characteristics are shown. coating is poor.

(3) multifunctionality crosslinking agent

Meanwhile, the pressure-sensitive adhesive composition of the present invention may further include a polyfunctional crosslinking agent together with the acrylic copolymers (A) and (B).

The multifunctional crosslinking agent is used to further improve the durability of the adhesive layer by reacting with the acrylic copolymer to form a crosslinked structure, and for example, an isocyanate-based crosslinking agent may be used. As the isocyanate-based crosslinking agent, a conventional one known in the art may be used, for example, toluene diisocyanate, 2,4-trylene diisocyanate, 2,6-trylene diisocyanate, hydrogenated torylene diisocyanate, Isoform diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4-diisocyanate, 1,3-bisisocyanatomethyl cyclohexane, tetramethylxylene diisocyanate, 1 ,5-naphthalene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, trimethylolpropane modified toluene diisocyanate, trimethylolpropane modified tolylene diisocyanate, torylene diisocyanate adduct of trimethylolpropane, xylene diisocyanate adduct of trimethylolpropane, triphenylmethanetoisocyanate, methylenebistriisocyanate, polyols (trimethylolpropane) and mixtures thereof, etc. Can be used.

The polyfunctional crosslinking agent is preferably included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer having a branched polymer structure. When the content of the polyfunctional crosslinking agent satisfies the above range, excellent durability can be obtained without deterioration of physical properties such as adhesion.

(4) other ingredients

The pressure-sensitive adhesive composition of the present invention may further include other components, such as a solvent, a silane coupling agent, a crosslinking catalyst, a tackifying resin, an additive, and the like, in addition to the components described above for controlling physical properties.

The pressure-sensitive adhesive composition of the present invention may further include a solvent for viscosity control. In this case, the solvent may include, for example, ethyl acetate, n-pentane, isopentane, neopentane, n-hexane, n-octane, n-heptane, methyl ethyl ketone, acetone, toluene, or a combination thereof, However, the present invention is not limited thereto. The solvent may be included in an amount such that the solid content in the pressure-sensitive adhesive composition is 20% by weight or more, preferably 20 to 60% by weight.

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

Such a silane coupling agent improves the adhesion and adhesion stability between the pressure-sensitive adhesive and the glass substrate, improves heat resistance and moisture resistance, and also improves adhesion reliability when the pressure-sensitive adhesive is left for a long time under high temperature and/or high humidity conditions. do. Examples of the coupling agent that can be used in the present invention include γ-glycidoxypropyl triethoxy silane, γ-glycidoxypropyl trimethoxy silane, γ-glycidoxypropyl methyldiethoxy silane, γ-glycidoxy propyl triethoxy silane, 3-mercaptopropyl trimethoxy silane, vinyltrimethoxysilane, vinyltriethoxy silane, γ-methacryloxypropyl trimethoxy silane, γ-methacryloxypropyl triethoxy silane, γ-aminopropyl trimethoxy silane, γ-aminopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, γ-acetoacetatepropyl trimethoxysilane, γ-acetoacetatepropyl triethoxy silane, and β-cyanoacetyl trimethoxy silane, β-cyanoacetyl triethoxy silane, and acetoxyaceto trimethoxy silane, and one or a mixture of two or more of them may be used. In the present invention, it is preferable to use a silane-based coupling agent having an acetoacetate group or a β-cyanoacetyl group, but is not limited thereto.

For example, the silane coupling agent may be a compound represented by the following formula (2).

[Formula 2]

(Ra)nSi(Rb)4-n

In Formula 2, Ra is a β-cyanoacetyl group, an acetoacetyl group, or an acetoacetylalkyl group, Rb is an alkoxy group, and n is an integer of 1 to 3. In this case, the alkyl group or alkoxy group included in Formula 2 may have 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4 carbon atoms, and may be a straight chain or branched chain.

Specific examples of the compound represented by Formula 2 include acetoacetylpropyl trimethoxysilane, acetoacetylpropyl triethoxy silane, beta-cyanoacetyl trimethoxy silane, or beta-cyanoacetyl triethoxy silane. However, the present invention is not limited thereto.

In the composition of the present invention, the silane-based coupling agent may be included in an amount of 0.01 parts by weight to 5 parts by weight, preferably 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of the acrylic copolymer (A) having a branched polymer structure. If the content of the coupling agent is less than 0.01 parts by weight, the effect of increasing the adhesive strength is insignificant, and when it exceeds 5 parts by weight, there is a risk of lowering durability.

The pressure-sensitive adhesive composition of the present invention may further include a crosslinking catalyst. The cross-linking catalyst is for accelerating curing (cross-linking) of the pressure-sensitive adhesive layer, and when the pressure-sensitive adhesive composition includes a cross-linking catalyst, there is an advantage that it does not need to go through a separate aging (aging) process after coating and drying the surface of the substrate. Examples of the crosslinking catalyst include bis(tri-n-butyltin)oxide, bis(tri-n-butyltin)sulfate, di-n-butyldiphenyltin, and di-n-butyltinbis(acetyl). acetonate), di-n-butyltin bis(2-ethylhexanoate), di-n-butyltin dichloride, di-n-butyltin dilaurate, di-n-butyltin oxide, dimethyldiphenyltin, Dimethyltin dichloride, diphenyltin dichloride, diphenyltin oxide, hexa-n-butyltin, hexaphenyltin, tetra-n-butyltin, tetraphenyltin, tin (II) acetate, tin (II) acetylacetonate, Tin (II) chloride, tin (II) iodide, tin (II) oxalate, etc. may be used, but is not limited thereto.

Meanwhile, the crosslinking catalyst may be included in an amount of 0.001 parts by weight to 0.5 parts by weight, preferably 0.001 parts by weight to 0.1 parts by weight, based on 100 parts by weight of the acrylic copolymer (A) having a branched polymer structure. If the content of the crosslinking catalyst is less than 0.001 parts by weight, the curing accelerating effect is insignificant, and when it exceeds 0.5 parts by weight, there is a fear that durability may be lowered.

The pressure-sensitive adhesive composition of the present invention may further include 1 part by weight to 100 parts by weight of a tackifying resin based on 100 parts by weight of the acrylic copolymer (A) having a branched polymer structure from the viewpoint of adjusting the adhesive performance. The kind of such tackifying resin is not particularly limited, and for example, (hydrogenated) hydrocarbon-based resin, (hydrogenated) rosin resin, (hydrogenated) rosin ester resin, (hydrogenated) terpene resin, (hydrogenated) terpene phenol resin, One kind or a mixture of two or more kinds of polymerized rosin resin or polymerized rosin ester resin may be used. When the content of the tackifying resin is less than 1 part by weight, there is a fear that the effect of addition is insignificant, and when it exceeds 100 parts by weight, there is a fear that the compatibility and/or the effect of improving cohesion may be reduced.

The pressure-sensitive adhesive composition of the present invention also includes one or more additives selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, and a plasticizer to the extent that the effect of the invention is not affected. may further include.

The pressure-sensitive adhesive composition according to the present invention including the above components has a low viscosity characteristic even when the solid content is high, so that excellent coating properties can be realized. Specifically, the pressure-sensitive adhesive composition according to the present invention has a viscosity of 2,000 cP or less at 23° C. appear low. In this case, the solid content may refer to the solid content at the time when the pressure-sensitive adhesive composition of the present invention is prepared in the form of a coating solution or the like, and is applied to the manufacturing process of the pressure-sensitive adhesive. As described above, when the pressure-sensitive adhesive composition of the present invention is used, it is possible to increase the solid content in the coating solution without deteriorating the coating property, so that not only the productivity is excellent, but also precise control of the thickness and the like is possible.

In addition, the pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive composition of the present invention has excellent re-peelability properties, excellent durability in high temperature, high temperature/high humidity, and room temperature and low humidity environments, and there is little change in physical properties of the adhesive layer over time.

Polarizer

Next, a polarizing plate according to the present invention will be described.

A polarizing plate according to the present invention, a polarizing film; and a pressure-sensitive adhesive layer formed on one or both sides of the polarizing film and containing a cured product of the pressure-sensitive adhesive composition according to the present invention described above.

The type of the polarizing film used in the present invention is not particularly limited, and a general type known in this field may be employed. For example, the polarizing film may include a polarizer; and a protective film formed on one or both surfaces of the polarizer.

The type of polarizer included in the polarizing plate of the present invention is not particularly limited, and, for example, a general type known in this field, such as polyvinyl alcohol-based polarizer, may be employed without limitation.

A polarizer is a functional film or sheet capable of extracting only light vibrating in one direction from incident light while vibrating in multiple directions. Such a polarizer may be, for example, a form in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. Polyvinyl alcohol-type resin which comprises a polarizer can be obtained by gelatinizing polyvinyl acetate-type resin, for example. In this case, the polyvinyl acetate-based resin that can be used may include not only a homopolymer of vinyl acetate, but also a copolymer of vinyl acetate and other monomers copolymerizable therewith. In the above, examples of the monomer copolymerizable with vinyl acetate include one or a mixture of two or more of unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group. not. The degree of gelation of the polyvinyl alcohol-based resin may be usually about 85 mol% to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be further modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. In addition, the degree of polymerization of the polyvinyl alcohol-based resin may be usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

The above polyvinyl alcohol-type resin can be formed into a film, and it can be used as a raw film of a polarizer. A method of forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a general method known in this field may be used.

The thickness of the raw film formed of the polyvinyl alcohol-based resin is not particularly limited, and for example, may be appropriately controlled within the range of 1 µm to 150 µm. In consideration of ease of stretching, etc., the thickness of the raw film may be controlled to 10 μm or more.

The polarizer is a step of stretching (ex. uniaxial stretching) the polyvinyl alcohol-based resin film as described above, dyeing the polyvinyl alcohol-based resin film with a dichroic dye, adsorbing the dichroic dye, and adsorbing the dichroic dye The polyvinyl alcohol-based resin film can be manufactured through a process of treating the polyvinyl alcohol-based resin film with an aqueous solution of boric acid and a process of washing with water after treatment with an aqueous solution of boric acid. In the above, as the dichroic dye, iodine or a dichroic organic dye may be used.

The polarizing film of the present invention may further include a protective film formed on one or both surfaces of the polarizer. The kind of protective film that may be included in the polarizing plate of the present invention is not particularly limited, and for example, a cellulose-based film such as triacetyl cellulose; polyester-based films such as polycarbonate films or polyethylene terephthalate films; polyether sulfone-based film; and/or a polyethylene film, a polypropylene film, or a polyolefin film having a cyclo- or norbornene structure, or a polyolefin-based film such as an ethylene propylene copolymer may be formed as a multilayer film in which a protective film is laminated. At this time, the thickness of the protective film is also not particularly limited, and may be formed in a conventional thickness.

On the other hand, the method of forming the pressure-sensitive adhesive layer on the polarizing film in the present invention is not particularly limited, and for example, a method of applying and curing the pressure-sensitive adhesive composition (coating solution) to the film or device by a conventional means such as a bar coater, or After the pressure-sensitive adhesive composition is once applied to the surface of the releasable substrate and cured, a method of transferring the formed pressure-sensitive adhesive layer onto the surface of a polarizing film or device may be used.

In the present invention, the process of forming the pressure-sensitive adhesive layer is preferably performed after sufficiently removing the bubble-inducing components such as volatile components or reaction residues inside the pressure-sensitive adhesive composition (coating solution). Accordingly, the crosslinking density or molecular weight of the pressure-sensitive adhesive is too low, and the elastic modulus is lowered, and bubbles present between the glass plate and the pressure-sensitive adhesive layer become large at a high temperature, thereby preventing problems such as forming a scatterer inside.

On the other hand, the method of curing the pressure-sensitive adhesive composition of the present invention during the manufacture of the polarizing plate is also not particularly limited, and may be carried out through a conventional curing method known in the art. For example, the curing may be performed by maintaining a temperature at which a crosslinking reaction can be induced between the crosslinkable functional group and the polyfunctional crosslinking agent in the pressure-sensitive adhesive composition applied through heating or the like.

The polarizing plate of the present invention may further include one or more functional layers selected from the group consisting of a protective layer, a reflective layer, an anti-glare layer, a retardation plate, a wide viewing angle compensation film, and a luminance enhancing film.

The polarizing plate according to the present invention as described above has little change over time of the adhesive layer, excellent durability even under high temperature or high temperature/high humidity conditions, and excellent reworkability.

Specifically, the polarizing plate has a creep distance (Creep) change rate defined by the following formula (1) of 15% or less, preferably 13% or less, more preferably 10% or less.

Equation (1): Push distance change rate (%)= (T ₀ -T ₁ /T ₀ )×100

In Equation (1), T ₀ is a measurement specimen prepared by attaching the polarizing plate to a glass substrate, stored at 23° C. and 50% RH for 1 day, and then stored at a load of 1,000 g for 1,000 seconds. It is the pushing distance measured when the polarizing plate is pulled, and T ₁ is the measurement specimen stored for 4 days at 23° C. and 50% RH, and then the polarizing plate of the measurement specimen was pulled for 1,000 seconds under a 1,000 g load. It is the rolling distance measured when

In addition, the polarizing plate according to the present invention has an adhesive force change rate defined by the following formula (2) of 30% or less, preferably 25% or less, more preferably 20% or less.

Equation (2): Adhesion change rate (%) = (B ₀ -B ₁ /B ₀ )×100

In the above formula (2), B ₀ is the polarizing plate is stored at 23 ℃, 50%RH conditions for 1 day, the polarizing plate is attached to a glass substrate, and stored at 23 ℃, 50% RH for 4 hours, It is the adhesive force measured when the polarizing plate is pulled under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees, and B ₁ is the polarizing plate after storing it for 4 days at 23 ° C. This is the adhesive force measured when the polarizing plate is attached to the polarizer, stored at 23° C., 50% RH for 4 hours, and then the polarizing plate is pulled under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees.

In addition, the polarizing plate according to the present invention has a re-peel force change rate defined by the following formula (3) of 30% or less, preferably 25% or less, more preferably 20% or less.

Equation (3): Re-peel force change rate (%)= (C ₀ -C ₁ /C ₀ )×100

In the above formula (3), C ₀ is after storing the polarizing plate at 23 ℃, 50%RH conditions for 1 day, attaching the polarizing plate to a glass substrate, storing at 80 ℃ for 1 hour, 23 ℃, 50% After storage for 1 hour at RH, the force required to completely separate the polarizing plate when the polarizing plate is pulled under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees, and C ₁ is the polarizing plate at 23° C., 50% After storage at RH for 4 days, the polarizing plate was attached to a glass substrate, stored at 80°C for 1 hour, stored at 23°C, 50% RH for 1 hour, and then peeled at a rate of 300 mm/min, peeling angle 180 It is the force required to completely separate the polarizing plate when the polarizing plate is pulled under the conditions of the figure.

display device

Next, the display device of the present invention will be described.

The display device of the present invention includes the above-described polarizing plate according to the present invention.

More specifically, the display device may be a liquid crystal display device including a liquid crystal panel in which the polarizing plate according to the present invention is bonded to one or both surfaces. In this case, the type of the liquid crystal panel is not particularly limited. In the present invention, for example, without being limited to the type, F various passive matrices including TN (Twisted Neumatic) type, STN (Super Twisted Neumatic) type, F (ferroelectric) type and PD (polymer dispersed LCD) type, etc. method; Various active matrix methods, including two-terminal and three-terminal; Any known liquid crystal panel including a horizontal electric field type (IPS mode) panel and a vertical alignment type (VA mode) panel may be applied. In addition, the type of other components included in the liquid crystal display of the present invention and the manufacturing method thereof are not particularly limited, and general configurations in this field may be employed without limitation.

production example 1: Preparation of acrylic copolymer (A-1) having a branched structure

97.2 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA), 0.18 parts by weight of allyl methacrylate (AMA) in a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed for easy temperature control A monomer mixture containing parts was added, and 60 parts by weight of ethyl acetate (EAc) was added as a solvent. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70°C. Then, 0.23 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator, 0.15 parts by weight of azobis(2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) as a polymerization initiator, allyl methacryl) The acrylic copolymer (A-1) was prepared by reacting for 10 hours while additionally adding 0.12 parts by weight of the rate (AMA), In this case, the allyl methacrylate was added after 3 hours of the reaction time, and the molecular weight regulator was the reaction time It was divided into 5 divided doses up to 5 hours, and the polymerization initiator was divided into 10 divided doses until 7 hours of reaction time while checking the degree of exotherm.

production example 2: Preparation of branched structure acrylic copolymer (A-2)

97.0 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA), 0.3 parts by weight of allyl methacrylate (AMA) in a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed for easy temperature control A monomer mixture containing parts was added, and 60 parts by weight of ethyl acetate (EAc) was added as a solvent. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70°C. Then, 0.185 parts by weight of n-dodecyl mercaptan (n-DDM) as a molecular weight regulator, 0.15 parts by weight of azobis (2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) as a polymerization initiator, 0.15 parts by weight, allyl methacryl The acrylic copolymer (A-2) was prepared by reacting for 10 hours while additionally adding 0.2 parts by weight of the rate (AMA), In this case, the allyl methacrylate was added after 3 hours of the reaction time, and the molecular weight regulator was the reaction time It was divided into 5 divided doses up to 5 hours, and the polymerization initiator was divided into 10 divided doses until 7 hours of reaction time while checking the degree of exotherm.

production example 3: Preparation of linear acrylic copolymer (B-1)

A monomer mixture containing 97.5 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA) is added to a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, and a solvent is used. 100 parts by weight of ethyl acetate (EAc) was added. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 64°C. Then, 0.052 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator and 0.04 parts by weight of azobisisobutyronitrile (V-60, manufacturer: Wako) as a polymerization initiator were additionally added and reacted for 7 hours. An acrylic copolymer (B-1) was prepared.

production example 4. Preparation of linear acrylic copolymer (B-2)

A monomer mixture containing 97.5 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA) is added to a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed for easy temperature control, and the solvent is used as a solvent. 100 parts by weight of ethyl acetate (EAc) was added. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 64°C. Then, 0.026 parts by weight of n-dodecyl mercaptan (n-DDM) as a molecular weight regulator and 0.04 parts by weight of azobisisobutyronitrile (V-60, manufacturer: Wako) as a polymerization initiator were additionally added and reacted for 4 hours. Then, 50 parts by weight of ethyl acetate (EAc) purged with nitrogen gas for 30 minutes was added for 1 hour and then reacted for 2 hours to prepare an acrylic copolymer (B-2).

production example 5. Preparation of linear acrylic copolymer (B-3)

A monomer mixture containing 98.7 parts by weight of butyl acrylate (BA) and 1.3 parts by weight of hydroxybutyl acrylate (HBA) is added to a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, and a solvent is used. 100 parts by weight of ethyl acetate (EAc) was added. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 64°C. Then, 0.006 parts by weight of n-dodecyl mercaptan (n-DDM) as a molecular weight regulator and 0.04 parts by weight of azobisisobutyronitrile (V-60, manufacturer: Wako) as a polymerization initiator were additionally added and reacted for 2 hours. After that, 85 parts by weight of ethyl acetate (EAc) purged with nitrogen gas for 30 minutes was added for 1 hour and then reacted for 4 hours to prepare an acrylic copolymer (B-3).

production example 6. Preparation of linear acrylic copolymer (B-4)

A monomer mixture containing 99.2 parts by weight of butyl acrylate (BA) and 0.8 parts by weight of hydroxybutyl acrylate (HBA) is added to a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, and a solvent is used. 120 parts by weight of ethyl acetate (EAc) was added. Then, after purging with nitrogen gas for 60 minutes to remove oxygen, the temperature was maintained at 62°C. Then, 0.03 parts by weight of azobisisobutyronitrile (V-60, manufacturer: Wako) was additionally added as a polymerization initiator and reacted for 2 hours, followed by purging with nitrogen gas for 30 minutes with ethyl acetate (EAc) After adding 90 parts by weight for 1 hour, it was further reacted for 5 hours to prepare an acrylic copolymer (B-4).

production example 7. Preparation of linear acrylic copolymer (B-5)

A monomer mixture containing 99.2 parts by weight of butyl acrylate (BA) and 0.8 parts by weight of hydroxybutyl acrylate (HBA) is added to a 3L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, and a solvent is used. 100 parts by weight of ethyl acetate (EAc) was added. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 64°C. Then, 0.011 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator and 0.04 parts by weight of azobisisobutyronitrile (V-60, manufacturer: Wako) as a polymerization initiator were additionally added, and for 2 hours and 30 minutes After the reaction, 85 parts by weight of ethyl acetate (EAc) purged with nitrogen gas for 30 minutes was added for 1 hour, and then reacted for 3 hours and 30 minutes to prepare an acrylic copolymer (B-5).

The weight average molecular weight and polymer structure of the acrylic copolymers prepared in Preparation Examples 1 to 7 were measured as follows and shown in Table 1.

(1) The weight average molecular weight was measured using GPC under the following conditions. The measurement results were converted using standard polystyrene of Agilent system to prepare the calibration curve.

<Measurement conditions>

Meter: Agilent GPC (Agulent 1200 series, USA)

Column: 2 PL Mixed B connections

Column temperature: 40°C

Eluent: Tetrohydrofuran

Flow rate: 1.0 mL/min

Concentration: ~ 1 mg/mL (100 μl injection)

(2) The polymer structure was evaluated as follows.

First, the same kind of alkyl (meth)acrylate-based monomer and (meth)acrylic-based monomer having a crosslinkable functional group as used in the acrylic copolymer to be evaluated for the polymer structure (hereinafter referred to as 'evaluation target copolymer') The mixture was mixed to prepare a monomer mixture. At this time, the content of the (meth)acrylic monomer having a crosslinkable functional group in the monomer mixture was made equal to the content of the (meth)acrylic monomer having a crosslinkable functional group in the copolymer to be evaluated. Then, the monomer mixture was polymerized to prepare an acrylic copolymer (hereinafter, referred to as a 'reference copolymer') having a weight average molecular weight (error range ±5%) equivalent to that of the copolymer to be evaluated.

Thereafter, ethyl acetate solvent was added to each of the reference copolymer and the copolymer to be evaluated to adjust the solid content concentration to 30%, and then the viscosity was measured. If the viscosity of the evaluation target copolymer measured as described above has a viscosity that is 30% or more lower than that of the reference copolymer, it is evaluated as having a branched polymer structure, and in other cases, it is evaluated as having a linear polymer structure. .

[Table 1]

Example One

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared in Preparation Example 1, 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5, and a polyfunctional crosslinking agent (coronate L, Nippon Poly) 0.2 parts by weight (manufactured by Urethane), 0.01 parts by weight of a crosslinking catalyst (di-n-butyltindilaurate, Sigma-Aldrich), 0.2 parts by weight of a silane coupling agent (silane coupling agent containing beta-cyanoacetyl group, LG Chem, M812) After mixing and diluting with ethyl acetate to a solid content of 50.7% by weight, uniformly mixed to prepare a pressure-sensitive adhesive composition (coating solution).

The prepared pressure-sensitive adhesive composition was applied to the release-treated surface of the release-treated polyethylene terephthalate film (release PET) having a thickness of 38 µm, so that the thickness after drying was 23 µm, and then dried to form a pressure-sensitive adhesive coating layer. Then, the adhesive coating layer was laminated on the polarizing plate to prepare a polarizing plate including the adhesive layer.

Example 2

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared in Preparation Example 1, and 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5, instead of 5 parts by weight of the branched copolymer prepared in Preparation Example 2 100 parts by weight of the acrylic copolymer A-2 of the structure, 30 parts by weight of the acrylic copolymer B-4 of the linear structure prepared in Preparation Example 6, and dilution so that the solid content is 20.9% by weight. A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1.

comparative example One

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5 was not added, and the solid content was diluted to 51.3% by weight. .

comparative example 2

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 2, except that the acrylic copolymer B-4 having a linear structure prepared in Preparation Example 6 was not added, and the solid content was diluted to 31.4% by weight. .

comparative example 3

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared by Preparation Example 1 and 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5 instead of 5 parts by weight of the linear structure prepared by Preparation Example 3 A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that 100 parts by weight of the acrylic copolymer B-1 was used and the solid content was diluted to 30.2% by weight.

comparative example 4

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared by Preparation Example 1 and 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared by Preparation Example 5 instead of 5 parts by weight of the linear structure prepared by Preparation Example 4 A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that 100 parts by weight of the acrylic copolymer B-2 was used and the solid content was diluted to 21.8% by weight.

comparative example 5

Instead of 30 parts by weight of the acrylic copolymer B-4 having a linear structure prepared in Preparation Example 5, 30 parts by weight of the acrylic copolymer B-5 having a linear structure prepared in Preparation Example 7 was used, and the solid content was 24.1% by weight. A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 2, except for dilution.

comparative example 6

Instead of 100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared in Preparation Example 1, 100 parts by weight of the acrylic copolymer B-1 having a linear structure prepared in Preparation Example 3 was used, and the solid content was 29.8% by weight. A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1 except for dilution as much as possible.

comparative example 7

100 parts by weight of the acrylic copolymer A-2 having a branched structure prepared in Preparation Example 2, 30 parts by weight of the acrylic copolymer B-4 having a linear structure prepared in Preparation Example 6 instead of 30 parts by weight of the linear structure prepared in Preparation Example 4 100 parts by weight of the acrylic copolymer B-2 and 5 parts by weight of the acrylic copolymer B-4 having a linear structure prepared by Preparation Example 6 were used, and the solid content was diluted to 21.2% by weight. A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in 2 .

comparative example 8

Using the acrylic copolymer B-1 having a linear structure prepared by Preparation Example 3 instead of the acrylic copolymer A-2 having a branched structure prepared by Preparation Example 2, and diluting it so that the solid content is 20.5% by weight Except that, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 2. The prepared pressure-sensitive adhesive composition was too high in viscosity to be coated for forming an adhesive layer.

comparative example 9

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared in Preparation Example 1 and 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5 instead of 5 parts by weight of the linear structure prepared in Preparation Example 5 An adhesive composition was prepared in the same manner as in Example 1, except that 100 parts by weight of the acrylic copolymer B-3 was used and the solid content was diluted to 20.0% by weight. The prepared pressure-sensitive adhesive composition was too high in viscosity to be coated for forming the pressure-sensitive adhesive layer.

comparative example 10

100 parts by weight of the acrylic copolymer A-1 having a branched structure prepared in Preparation Example 1 and 5 parts by weight of the acrylic copolymer B-3 having a linear structure prepared in Preparation Example 5 instead of 5 parts by weight of the linear structure prepared in Preparation Example 5 A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that 100 parts by weight of the acrylic copolymer B-3 was used and the solid content was diluted to 15.8% by weight.

comparative example 11

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 2, except that 35 parts by weight of the acrylic copolymer B-4 having a linear structure prepared in Preparation Example 6 was diluted so that the solid content was 20.2% by weight. . The prepared pressure-sensitive adhesive composition was too high in viscosity to be coated for forming an adhesive layer.

comparative example 12

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that 3 parts by weight of the acrylic copolymer B-3 having a linear structure prepared by Preparation Example 5 was diluted so that the solid content was 51.1% by weight. prepared.

The physical properties of the pressure-sensitive adhesive composition and the polarizing plate prepared in Examples 1 to 2 and Comparative Examples 1 to 12 were measured by the following method, and the measurement results are shown in Tables 2 and 3 below.

How to measure physical properties

1. Coating solids content (unit: %)

The coating solid content was measured as follows.

First, the weight (A) of the aluminum dish is measured, and then the pressure-sensitive adhesive composition prepared in Examples or Comparative Examples is collected in an amount of about 0.3 to 0.5 g (weight of the sample before drying: S) and the weight is It was placed in a measured aluminum dish. At this time, the weight B (A+S) of the sample before drying including the aluminum dish is measured. Then, a very small amount of an ethyl acetate solution in which a polymerization inhibitor (hydroquinone) is dissolved (a polymerization inhibitor concentration of 0.5 wt%) is added to the pressure-sensitive adhesive composition in a very small amount using a pipette, and the solvent is removed by drying it in an oven at 150°C for about 30 minutes. removed. Thereafter, the dried sample was cooled at room temperature for about 15 to 30 minutes, and after drying including the aluminum dish weight A, the weight including the weight C of the sample was measured, and the coating solid content was measured according to Equation (4) below.

Formula (4): Coating solids (%) = {(C-A)/(B-A)}X100

In Equation (4), A is the weight of the aluminum dish (unit: g), C is the weight of the sample after drying including the weight A of the aluminum dish (unit: g), and B is the sample before drying including the weight A of the aluminum dish is the weight (unit: g) of

2. Coating viscosity (unit: cP)

The coating viscosity of the pressure-sensitive adhesive composition was evaluated according to the following procedure using a Brookfield digital viscometer (RV DV2T).

Put about 220 mL of the pressure-sensitive adhesive composition into a 250 mL PE bottle, close the lid so that the solvent does not volatilize, seal it sufficiently with parafilm, etc., and then leave it sufficiently under constant temperature/humidity (23° C., 50% relative humidity) conditions to remove air bubbles. Then, after removing the seal and lid, a spindle was placed at an angle to prevent bubbles from forming in the pressure-sensitive adhesive composition, the spindle was connected to a viscometer, and the liquid level of the pressure-sensitive adhesive composition was adjusted to fit into the groove of the spindle. Then, the viscosity was measured under the rpm condition in which the torque was 20% (±1%).

3. Coatability

When the pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was coated on a polyethylene terephthalate film, the state of the coating layer was visually observed and evaluated according to the following criteria.

<Coatability Evaluation Criteria>

○: Bubbles, streaks, etc. were not visually confirmed in the coating layer.

Δ: Microscopically confirmed bubbles and/or streaks in the coating layer.

X: A uniform coating layer is not formed.

4. Creep distance (Creep, unit: ㎛)

A specimen was prepared by cutting the polarizing plate prepared in Examples and Comparative Examples into sizes of 10 mm in width and 10 mm in length. Then, the release PET film attached to the adhesive layer was peeled off, and a polarizing plate was attached to an alkali-free glass using a roller of 2 kg according to JIS Z 0237 to prepare a measurement specimen. Then, the specimen for measurement was stored at constant temperature and humidity conditions (23° C., 50% R.H.) for 1 day and 4 days, respectively, and then each pushing distance using TA equipment (Texture Analyzer, Stable Microsystems Co., UK) was measured. Specifically, the pushing distance was measured as the distance (unit: μm) pushed by the polarizing plate from the glass substrate when the polarizing plate of the measurement specimen was pulled for 1,000 seconds under a load of 1,000 g.

5. Adhesion (Unit: gf/25mm)

The polarizing plates prepared in Examples and Comparative Examples were stored in constant temperature and humidity conditions (23° C., 50% R.H.) for 1 day and 4 days, respectively, and then cut to have a width of 25 mm and a length of 100 mm to prepare a specimen. Then, the release PET film attached to the adhesive layer was peeled off, and a polarizing plate was attached to an alkali-free glass using a roller of 2 kg according to JIS Z 0237 to prepare a measurement specimen.

The specimen for measurement was stored under constant temperature and humidity conditions (23° C., 50% R.H.) for 4 hours. Then, the force required to completely separate the polarizing plate from the glass substrate is measured by pulling the polarizing plate under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees using TA equipment (Texture Analyzer, manufactured by Stable Microsystems, UK). to measure the adhesive force (unit: gf/25mm).

6. Re-peel force (unit: gf/25mm) and re-peelability:

The polarizing plates prepared in Examples and Comparative Examples were stored in constant temperature and humidity conditions (23° C., 50% R.H.) for 1 day and 4 days, respectively, and then cut to have a width of 25 mm and a length of 100 mm to prepare a specimen. Then, the release PET film attached to the adhesive layer was peeled off, and a polarizing plate was attached to an alkali-free glass using a roller of 2 kg according to JIS Z 0237 to prepare a measurement specimen.

Then, the specimen for measurement was stored at 80° C. for 1 hour, and then stored under constant temperature and humidity conditions (23° C., 50% R.H.) for 1 hour. Then, the force required to completely separate the polarizing plate from the glass substrate is measured by pulling the polarizing plate under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees using TA equipment (Texture Analyzer, manufactured by Stable Microsystems, UK). to measure the re-peel force (unit: gf/25mm).

In addition, re-peelability was evaluated based on the following criteria after re-peelability.

<Evaluation criteria>

○: When the re-peel force is 1,500 gf/25 mm or less, and there is no adhesive layer remaining on the glass substrate after re-peelling

△: When the re-peel force exceeds 1,500 gf/25 mm and 2,500 gf/25 mm or less, or when the adhesive layer residue is confirmed on the glass substrate after re-peeling, and the residue area is 5% or less

×: If the re-peel force exceeds 3,000 gf/25 mm, or if the adhesive layer residue is confirmed on the glass substrate after re-peeling, the residue area exceeds 5%

7. Durability evaluation

A sample was prepared by cutting the polarizing plate prepared in Examples and Comparative Examples to a size of 180 mm × 250 mm (length × width), and the sample was attached to a 19-inch commercial panel using a laminator. Thereafter, the panel was pressed in an autoclave (50° C. and 5 atm) for about 20 minutes, and then stored for 24 hours under constant temperature and humidity conditions (23° C., 50% R.H.) to prepare a measurement specimen.

The heat resistance durability was evaluated by leaving the prepared specimen at a temperature of 80° C. for 500 hours, and then observing whether bubbles or peeling occurred.

The heat-and-moisture resistance was evaluated by leaving the prepared specimen at a temperature of 60° C. and a relative humidity of 90% R.H. for 500 hours, and then observing whether bubbles or peeling occurred.

The room temperature and low humidity durability was evaluated by leaving the specimen for which the moisture and heat resistance was evaluated for 500 hours at a temperature of 25° C. and a relative humidity of 25% R.H., and then observing whether bubbles or peeling occurred.

<Evaluation criteria>

○: No bubbles and no peeling

△: Slightly generated bubbles and/or peeling

×: A large amount of bubbles and/or peeling occurred

[Table 2]

[Table 3]

As shown in [Table 2] and [Table 3], the pressure-sensitive adhesive composition of Examples 1 and 2 using the acrylic copolymer having a branched polymer structure of the present invention is 2,000 even when the solid content is as high as 20% by weight or more. Viscosity characteristics of cP or less were exhibited, and it can be seen that the sliding distance, adhesive force, and re-peelability change rate were low, indicating excellent stability over time. In addition, the re-peelability of the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Examples 1 and 2 was excellent, and durability at high temperature, high temperature/high humidity, and room temperature and low humidity environment was also excellent.

In contrast, the pressure-sensitive adhesive compositions of Comparative Examples 1 to 7, 10 and 12 showed relatively low coating viscosity, but showed a high rate of change over time in the pushing distance, adhesive force or re-peelability compared to the pressure-sensitive adhesive composition of Examples 1 to 2, or , it was found that the room temperature and low humidity durability measured after the moisture and heat resistance test was lowered.

In addition, in the pressure-sensitive adhesive compositions of Comparative Examples 8 to 9 and 11, when the solid content was 20% by weight or more, the coating viscosity exceeded 2000 cP, and it was impossible to proceed with the coating process.

Claims (16)

An acrylic copolymer having a branched polymer structure formed by polymerizing a first monomer mixture including a monomer represented by the following [Formula 1], a (meth)acrylic monomer having a crosslinkable functional group, and an alkyl (meth)acrylate monomer (A) 100 parts by weight; and
An acrylic copolymer comprising 5 to 30 parts by weight of an acrylic copolymer (B) having a linear polymer structure formed by polymerizing a second monomer mixture including a (meth)acrylic monomer having a crosslinkable functional group and an alkyl (meth)acrylate monomer It is a pressure-sensitive adhesive composition,
The acrylic copolymer (A) has a weight average molecular weight of 300,000 to 1,000,000 g/mol,
The acrylic copolymer (B) is an acrylic pressure-sensitive adhesive composition having a weight average molecular weight of 1,500,000 to 2,000,000 g/mol.
[Formula 1]
R ¹ -CH=CR ² -(C=O)-OXY
In Formula 1, R ¹ is hydrogen, a C1 to C6 alkyl group or a C2 to C6 alkenyl group, R ² is hydrogen or a C1 to C10 alkyl group, X is a single bond, a C1 to C10 alkylene group, a C2 to C10 alkenylene group , ether, ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.
According to claim 1,
The monomer represented by Formula 1 is allyl methacrylate, allyl acrylate, methallyl methacrylate, methallyl acrylate, 3-part Tenyl acrylate (3-butenyl acrylate), but-3-enyl-2-methylprop-2-enoate (but-3-enyl-2-methylprop-2-enoate), 2-allyloxyethyl acrylate ( 2-allyloxyethyl acrylate, 2-allyloxyethyl methacrylate, 3-allyloxypropyl methacrylate, 3-allyloxypropyl acrylate, 2-allyloxyethoxy Ethyl methacrylate (2-allyloxyethoxyethyl methacrylate), 2-allyloxyethoxyethyl acrylate, cyclohex-2-enyl acrylate, cyclo-hex-2- En-1-yl-2-methylprop-2-enoate (cyclohex-2-en-1-yl 2-methylprop-2-enoate) and 3-vinylcyclohex-2-enyl acrylate (3-vinylcyclohex) -2-enyl acrylate) at least one acrylic pressure-sensitive adhesive composition selected from the group consisting of.
According to claim 1,
The first monomer mixture is an acrylic pressure-sensitive adhesive composition comprising 0.01 to 1 part by weight of the monomer represented by the above [Formula 1] based on 100 parts by weight of the monomer mixture.
According to claim 1,
The first monomer mixture, based on 100 parts by weight of the first monomer mixture,
84 parts by weight to 99.89 parts by weight of the alkyl (meth)acrylate-based monomer;
0.1 to 15 parts by weight of a (meth)acrylic monomer having the crosslinkable functional group; and
The acrylic pressure-sensitive adhesive composition comprising 0.01 to 1 part by weight of the monomer represented by the [Formula 1].
According to claim 1,
The second monomer mixture is, based on 100 parts by weight of the second monomer mixture, 85 parts by weight to 99.9 parts by weight of an alkyl (meth)acrylate-based monomer and 0.1 to 15 parts by weight of a (meth)acrylic monomer having a crosslinkable functional group. An acrylic pressure-sensitive adhesive composition comprising.
According to claim 1,
The pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive composition further comprising a multifunctional crosslinking agent.
7. The method of claim 6,
The polyfunctional crosslinking agent is an isocyanate-based crosslinking agent acrylic pressure-sensitive adhesive composition.
7. The method of claim 6,
The multifunctional crosslinking agent is an acrylic pressure-sensitive adhesive composition that is included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer (A) having a branched polymer structure.
According to claim 1,
The acrylic pressure-sensitive adhesive composition has a solid content of 20% by weight or more, and the viscosity at 23°C is 2000cP or less.
According to claim 1,
The acrylic pressure-sensitive adhesive composition has a solid content of 20% to 60% by weight and a viscosity of 500 to 2000cP at 23°C.
polarizing film; and
A polarizing plate comprising an adhesive layer formed on one or both sides of the polarizing film and comprising a cured product of the acrylic pressure-sensitive adhesive composition of any one of claims 1 to 10.
12. The method of claim 11,
The polarizing plate is a polarizing plate having a creep distance (Creep) change rate defined by the following formula (1) of 15% or less.
Equation (1): Push distance change rate (%)= (T ₀ -T ₁ /T ₀ )×100
In Equation (1), T ₀ is a measurement specimen prepared by attaching the polarizing plate to a glass substrate, stored at 23° C. and 50% RH for 1 day, and then stored at a load of 1,000 g for 1,000 seconds. It is the pushing distance measured when the polarizer is pulled,
T ₁ is the pushing distance measured when the polarizing plate of the measurement specimen is stored for 4 days at 23° C. and 50%RH condition, and then the polarizing plate of the measurement specimen is pulled for 1,000 seconds under a load of 1,000 g.
12. The method of claim 11,
The polarizing plate is a polarizing plate having an adhesive force change rate of 30% or less as defined by the following formula (2).
Equation (2): Adhesion change rate (%) = (B ₀ -B ₁ /B ₀ )×100
In the above formula (2), B ₀ is the polarizing plate is stored at 23 ℃, 50%RH conditions for 1 day, the polarizing plate is attached to a glass substrate, and stored at 23 ℃, 50% RH for 4 hours, It is the adhesive force measured when the polarizing plate is pulled under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees,
The B ₁ is after storing the polarizing plate at 23 ° C., 50% RH for 4 days, attaching the polarizing plate to a glass substrate, storing at 23 ° C., 50% RH for 4 hours, then peeling speed 300 mm / min, It is the adhesive force measured when the polarizing plate is pulled under the condition of a peeling angle of 180 degrees.
12. The method of claim 11,
The polarizing plate is a polarizing plate having a re-peel force change rate of 30% or less, which is defined by the following formula (3).
Equation (3): Re-peel force change rate (%)= (C ₀ -C ₁ /C ₀ )×100
In the above formula (3), C ₀ is after storing the polarizing plate at 23 ℃, 50%RH conditions for 1 day, attaching the polarizing plate to a glass substrate, storing at 80 ℃ for 1 hour, 23 ℃, 50% It is the force required to completely separate the polarizing plate when the polarizing plate is pulled under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees after storage at RH for 1 hour,
The C ₁ stores the polarizing plate at 23° C. and 50% RH for 4 days, attaches the polarizer to a glass substrate, stores at 80° C. for 1 hour, and then stores at 23° C., 50% RH for 1 hour. Then, the force required to completely separate the polarizing plate when the polarizing plate is pulled under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees.
12. The method of claim 11,
The polarizing plate has a creep distance (Creep) change rate defined by the following formula (1) is 15% or less, an adhesive force change rate defined by the following formula (2) is 30% or less, and a re-peel force defined by the following formula (3) A polarizing plate with a change rate of 30% or less.
Equation (1): Push distance change rate (%)= (T ₀ -T ₁ /T ₀ )×100
(In Equation (1), T ₀ is a specimen for measurement by attaching the polarizing plate to a glass substrate, storing it for 1 day at 23° C. and 50% RH, and then storing the specimen for 1,000 seconds under a load of 1,000 g. is _the pushing distance measured when the polarizing plate of It is the push distance measured when
Equation (2): Adhesion change rate (%) = (B ₀ -B ₁ /B ₀ )×100
(In Equation (2), B ₀ is after storing the polarizing plate at 23 ° C., 50% RH for 1 day, attaching the polarizing plate to a glass substrate, and storing at 23 ° C., 50% RH for 4 hours. , the peeling rate 300mm / min, the peeling angle is the adhesive force measured when the polarizing plate is pulled under the conditions of 180 degrees, wherein B ₁ is the polarizing plate after storing the polarizing plate at 23 ℃, 50%RH conditions for 4 days, and then the polarizing plate is free It is the adhesive force measured when the polarizing plate is attached to a substrate, stored at 23° C., 50% RH for 4 hours, and then the polarizing plate is pulled under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees)
Equation (3): Re-peel force change rate (%)= (C ₀ -C ₁ /C ₀ )×100
(In the above formula (3), C ₀ is after storing the polarizing plate at 23 ℃, 50%RH conditions for 1 day, attaching the polarizing plate to a glass substrate, storing at 80 ℃ for 1 hour, 23 ℃, 50 After storage at % RH for 1 hour, the force required to completely separate the polarizing plate when the polarizing plate is pulled under the conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees, and C ₁ is the polarizing plate at 23° C., 50 After storage at %RH for 4 days, the polarizing plate is attached to a glass substrate, stored at 80° C. for 1 hour, and then stored at 23° C. and 50% RH for 1 hour, peeling rate 300 mm/min, peeling angle It is the force required to completely separate the polarizing plate when the polarizing plate is pulled under the condition of 180 degrees)
A display device comprising the polarizing plate of claim 11 .