KR101631379B1 - Pressure sensitive adhesive composition - Google Patents

Abstract

The present invention relates to a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition according to the present invention can form a pressure-sensitive adhesive excellent in endurance reliability, stress relaxation property and reworkability. Incidentally, when the pressure-sensitive adhesive composition is used additionally, the coating process can be efficiently carried out, for example, even when the solid content of the coating is kept high, so that a pressure-sensitive adhesive excellent in productivity and excellent in thickness uniformity can be formed . The pressure-sensitive adhesive composition can be used for an optical film such as a polarizing plate or the like.

Description

[0001] PRESSURE SENSITIVE ADHESIVE COMPOSITION [0002]

The present invention relates to a pressure-sensitive adhesive composition, an optical laminate, a polarizing plate and a display device.

In general, in order to manufacture a liquid crystal display device (hereinafter, referred to as "LCD device"), a liquid crystal cell and a polarizing plate including a liquid crystal are basically required, and an appropriate adhesive layer or adhesive layer . Further, in order to improve the function of the liquid crystal display device, a retardation plate, a wide viewing angle compensation plate, a brightness enhancement film, or the like may be additionally attached to the polarizing plate.

The main structure for forming the liquid crystal display device is a liquid crystal layer arranged in a regular manner; A polarizing plate having a multi-layered structure in which a pressure-sensitive adhesive layer or an adhesive layer is incorporated with a liquid crystal cell constituted of a transparent glass plate or a plastic plate-like material containing a transparent electrode layer as a reference; Retarder; And additional functional film layers and the like.

In this case, the polarizing plate has a structure including a iodine compound or a dichroic polarizing material arranged in a predetermined direction. In order to protect these polarizing elements, a protective film such as triacetyl cellulose (TAC) . The polarizing plate may additionally include a retardation film having a unidirectional molecular arrangement, a wide viewing angle compensation film such as a liquid crystal type film, a brightness enhancement film, a reflective layer, or a smokable layer.

Each of the above-mentioned films has different physical properties because they are made of materials having different molecular structures and compositions. Particularly under heat or humid conditions, there is a lack of dimensional stability due to shrinkage or expansion of materials having a unidirectional molecular arrangement.

In a TN (Twisted Nematic) type or STN (Super Twisted Nematic) type liquid crystal display system, the optical axis of a polarizing plate is usually crossed on both sides of a liquid crystal panel at 45 degrees and 135 degrees. In the liquid crystal display system, when the polarizing plate is fixed by the pressure-sensitive adhesive, the deformation stress due to the heat or the humid environment remains in the remained state, and light leakage occurs in the portion where the stress is concentrated. Also, the light leakage occurs more largely as the thickness of the liquid crystal panel is reduced. In order to solve this problem, there has been an attempt to improve the light leakage by applying a stress relaxation function to the pressure-sensitive adhesive to relieve stress concentration due to the contraction of the polarizing plate.

However, a liquid crystal display device such as IPS (In-Plane Switching) or VA (Vertical Alignment), which is mainly used for a large-sized TV, is attached by crossing the optical axis of the polarizing plate on both sides of the liquid crystal panel at 0 degree and 90 degrees. In such a liquid crystal display device, light leakage due to stress concentration is also generated in a heat or humid environment, but the warping of the liquid crystal panel is known to be an important cause of light leakage. The warping of the liquid crystal panel is caused by a difference in shrinkage percentage of the polarizing plate (particularly, in the direction of stretching shrinkage) depending on the position under heat or wet heat. That is, in the TN or STN liquid crystal display device, the optical axes of the polarizing plates are crossed at 45 degrees and 135 degrees so that the stretching axis directions of the upper and lower polarizing plates are symmetrically or balanced, while the liquid crystal display devices such as IPS or VA, Since the optical axes of the upper and lower polarizers are crossed at 0 degree and 90 degrees, the extension axis direction of the upper and lower polarizers is asymmetric. Therefore, in a liquid crystal display device such as IPS or VA, warping by the upper polarizing plate and warping by the lower polarizing plate are different, so that warping of the liquid crystal panel occurs in a direction in which the warping is large as a whole. Due to the warping of the liquid crystal panel, the liquid crystal panel is pressed by the top case used for fixing the liquid crystal panel, thereby generating light leakage due to unevenness of the liquid crystal.

Patent Document 1 discloses a liquid crystal display device such as an IPS or MVA type in which the storage elastic modulus at 0 to 50 ° C after crosslinking is 10 ⁵ 10 ⁹ Pa, and a glass transition temperature of -20 캜 or higher. This document discloses that the light leakage phenomenon can be improved by using a pressure sensitive adhesive having a higher elastic modulus and a higher glass transition temperature than conventional pressure sensitive adhesives. However, this does not mention an improvement in the warp of the IPS or MVA type liquid crystal panel, and it is difficult to improve the light leakage due to the warping of the liquid crystal panel by the above-described method.

Accordingly, the development of a new pressure-sensitive adhesive for a polarizing plate which can improve the light leakage phenomenon due to the warpage of the liquid crystal panel while hardly changing the main characteristics of the polarizing plate product such as durability and reliability that can occur during long- The polarizing plate applied is desperately required.

Patent Document 1: JP-A-2006-058718

The present invention provides a pressure-sensitive adhesive composition, an optical laminate, a polarizing plate and a display device.

The present invention relates to a pressure-sensitive adhesive composition.

Exemplary pressure sensitive adhesive compositions may include block copolymers. As used herein, the term " block copolymer " may refer to a copolymer comprising blocks of different polymerized monomers.

In one example, the block copolymer may include a first block having a glass transition temperature of 60 ° C to 100 ° C and a second block having a glass transition temperature of -10 ° C or less. In the present specification, the "glass transition temperature of a given block" of a block copolymer means a glass transition temperature measured from a polymer formed only of the monomers contained in the block. In one example, the glass transition temperature of the first block may preferably be 65 [deg.] C to 95 [deg.] C. In the above, the glass transition temperature of the second block may be -20 占 폚 or lower, -30 占 폚 or lower, -35 占 폚 or lower, or -40 占 폚 or lower. The lower limit of the glass transition temperature of the second block is not particularly limited, but may be, for example, about -80 캜, -70 캜, -60 캜, or -55 캜. The block copolymer containing at least two kinds of blocks may form a fine phase separation structure in the pressure-sensitive adhesive, for example. Such a block copolymer exhibits appropriate stress relaxation property realized by a proper cohesive force and a temperature change realized from a fine phase separation structure and thus has excellent durability and adhesive property and also exhibits light leakage phenomenon caused by bending when applied to a liquid crystal display device Sensitive adhesive can be effectively formed.

The first block in the block copolymer may have a number average molecular weight (M _n ) of 2,500 to 150,000, for example. The number average molecular weight of the first block means, for example, the number average molecular weight of the polymer produced by polymerizing only the monomer forming the first block. The number average molecular weight referred to in the present specification can be measured by a method as shown in the examples using, for example, GPC (Gel Permeation Chromatograph). The number average molecular weight of the first block may be about 5,000 to 100,000 or 10,000 to 50,000 in another example. In addition, the block copolymer may have a number average molecular weight of 50,000 to 300,000. The number average molecular weight of the block copolymer may be in the range of 90,000 to 250,000, 90,000 to 200,000 or 90,000 to 180,000 in another example. The block copolymer preferably has a molecular weight distribution (PDI; Mw / Mn), that is, a ratio (Mw / Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) within a range of 1.0 to 2.5 or 1.4 to 2.5 Can be. The pressure-sensitive adhesive composition or pressure-sensitive adhesive of excellent physical properties can be provided by controlling the molecular weight characteristics as described above.

In one example, the block copolymer may be a crosslinkable copolymer having a crosslinkable functional group. As the crosslinkable functional group, a hydroxy group, a carboxyl group, an isocyanate group or a glycidyl group can be exemplified, and for example, a hydroxy group can be used.

In the case of containing a crosslinkable functional group, the functional group may be included in, for example, a second block having a low glass transition temperature. In one example, the first block having a high glass transition temperature may not contain a crosslinkable functional group, and the second block may contain a crosslinkable functional group. When a crosslinkable functional group is included in the second block, the pressure-sensitive adhesive exhibits appropriate cohesive force and stress relaxation property in accordance with temperature change, thereby forming a pressure-sensitive adhesive excellent in physical properties required for optical films such as durability, light- can do.

The kind of the monomer forming the first block and the second block in the block copolymer is not particularly limited as long as the glass transition temperature as described above can be ensured by the combination of the respective monomers.

In one example, the first block may comprise polymerized units derived from (meth) acrylic acid ester monomers. As used herein, the fact that a monomer is contained in a polymer or a block in a polymerized unit may mean that the monomer undergoes a polymerization reaction to form a skeleton of the polymer or block, for example, a main chain or a side chain. As the (meth) acrylic acid ester monomer, for example, alkyl (meth) acrylate may be used. In one example, considering the control of cohesion, glass transition temperature and tackiness, alkyl (meth) acrylates having an alkyl group of 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms Methacrylate may be used. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (Meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate and lauryl (meth) acrylate. Can be selected and used. As the monomer forming the first block in consideration of the ease of controlling the glass transition temperature and the like, though not particularly limited, methacrylic acid ester monomers such as methacrylic acid ester monomers having 1 to 20 carbon atoms, 1 to 16 carbon atoms, Alkyl methacrylates having 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms can be used.

The second block of the block copolymer includes, for example, 90 parts by weight to 99.9 parts by weight of a (meth) acrylic acid ester monomer and polymerized units derived from 0.1 to 10 parts by weight of a copolymerizable monomer having a crosslinkable functional group can do. In the present specification, the unit weight portion may mean the ratio of the weight between the respective components. For example, as described above, the second block includes polymerized units derived from 90 to 99.9 parts by weight of the (meth) acrylic acid ester monomer and 0.1 to 10 parts by weight of the copolymerizable monomer having a crosslinkable functional group (A: B) based on the weight of the (meth) acrylic acid ester monomer (A) forming the polymerized unit of the second block and the copolymerizable monomer (B) having a crosslinkable functional group is 90 to 99.9: 0.1 to 10, respectively.

As the (meth) acrylic acid ester monomer forming the second block, it is possible to secure a glass transition temperature in the above-described range finally through copolymerization with the copolymerizable monomer among the monomers that can be contained in the first block Type monomers can be selected and used. The (meth) acrylic acid ester monomer forming the second block in consideration of the ease of controlling the glass transition temperature and the like is not particularly limited, but examples of the monomer described above include acrylic acid ester monomers such as acrylic acid ester monomers having 1 to 20 carbon atoms, Alkyl acrylates having 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms can be used.

Examples of the copolymerizable monomer having a crosslinkable functional group include a copolymerizable monomer having a moiety copolymerizable with other monomers contained in the block copolymer such as the above (meth) acrylic acid ester monomer and having a crosslinkable functional group, For example, a monomer having a hydroxyl group or the like can be used. In the production of pressure-sensitive adhesives, a variety of copolymerizable monomers having the above-mentioned crosslinkable functional groups are known, and all of these monomers can be used in the polymer. Examples of the copolymerizable monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) Hydroxyalkyl (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate such as hydroxyalkyl (meth) acrylate or 8-hydroxyoctyl (Meth) acrylate, and the like can be used, but the present invention is not limited thereto. Hydroxyalkyl acrylate or hydroxyalkylene glycol acrylate among the above monomers may be used in consideration of reactivity with other monomers forming the second block and easiness of controlling the glass transition temperature and the like. no.

The first block and / or the second block may further comprise any other comonomer, if necessary, for example, for controlling the glass transition temperature and the like, and the monomer may be included as polymerized units have. Examples of the comonomer include (meth) acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-vinylpyrrolidone, Nitrogen-containing monomers such as lactam and the like; (Meth) acrylic acid esters, alkoxy alkylene glycol (meth) acrylic acid esters, alkoxy alkylene glycol (meth) acrylic acid esters, alkoxy alkylene glycol (Meth) acrylic acid esters, phenoxy alkylene glycol (meth) acrylic acid esters, phenoxy alkylene glycol (meth) acrylic acid esters, phenoxy trialkylene glycol Alkylene oxide group-containing monomers such as polyalkylene glycol (meth) acrylic acid esters and the like; Glycidyl group-containing monomers such as glycidyl (meth) acrylate; And carboxylic acid vinyl esters such as vinyl acetate, but are not limited thereto. These comonomers may be included in the polymer by selecting one kind or more than two types as appropriate according to need. Such comonomers may be included in the block copolymer, for example, in a proportion of 20 parts by weight or less, or 0.1 parts by weight to 15 parts by weight, based on the weight of the other monomer in each block.

The block copolymer may comprise, for example, 5 to 50 parts by weight of the first block and 50 to 95 parts by weight of the second block. The ratio of the weight between the first block and the second block is adjusted as described above to provide the pressure-sensitive adhesive composition and the pressure-sensitive adhesive having excellent physical properties. In another example, the block copolymer comprises 5 to 45 parts by weight of the first block and 55 to 95 parts by weight of the second block, or 5 to 40 parts by weight of the first block and 60 to 60 parts by weight of the second block, 95 parts by weight.

In one example, the block copolymer may be a diblock copolymer comprising the first and second blocks, i.e. a block copolymer comprising only two blocks of the first and second blocks. By using the diblock copolymer, the durability of the pressure-sensitive adhesive, the stress relaxation property, and the reworkability can be maintained more excellent.

The method for producing the block copolymer is not particularly limited and can be produced in a usual manner. The block polymer is polymerized by, for example, an LRP (Living Radical Polymerization) method. Examples thereof include an organic rare earth metal complex as a polymerization initiator or an alkali metal or alkaline earth metal salt using an organic alkali metal compound as a polymerization initiator , An anionic polymerization method in which an organic alkali metal compound is used as a polymerization initiator and synthesized in the presence of an organoaluminum compound, an atomic transfer radical polymerization method using an atom transfer radical polymerization agent as a polymerization initiator (ATRP), an activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP), and an initiator for ICAR (polymerization initiator) for performing polymerization under an organic or inorganic reducing agent that generates electrons using an atom transfer radical polymerization agent as a polymerization initiator continuous activator regeneration) Atom Transfer Radical Polymerization (ATRP), weapon (RAFT) using a reversible addition-cleavage chain transfer agent using a reducing agent addition-cleavage chain transfer agent, or a method using an organic tellurium compound as an initiator. Among these methods, an appropriate method can be selected and applied.

The pressure-sensitive adhesive composition may further comprise a crosslinking agent capable of crosslinking the block copolymer. As the crosslinking agent, a crosslinking agent having at least two functional groups capable of reacting with the crosslinkable functional group contained in the block copolymer may be used. Examples of such a crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent or a metal chelate crosslinking agent, and for example, an isocyanate crosslinking agent may be used.

Examples of the isocyanate crosslinking agent include diisocyanate compounds such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoboron diisocyanate, tetramethylxylene diisocyanate and naphthalene diisocyanate, A compound obtained by reacting a diisocyanate compound with a polyol can be used. As the polyol, for example, trimethylolpropane and the like can be used.

The pressure-sensitive adhesive composition may contain one or more of the above-mentioned crosslinking agents, but the crosslinking agents that can be used are not limited thereto.

The multifunctional crosslinking agent may be contained in the adhesive composition in an amount of, for example, 0.01 part by weight to 1 part by weight, 0.02 part by weight to 0.5 part by weight or 0.03 to 0.25 part by weight based on 100 parts by weight of the block copolymer, Fraction, cohesion, adhesion and durability can be excellently maintained.

The pressure-sensitive adhesive composition may further include a silane coupling agent. As the silane coupling agent, for example, a silane coupling agent having a beta-cyano group or an acetoacetyl group can be used. Such a silane coupling agent can make the pressure sensitive adhesive formed by, for example, a copolymer having a low molecular weight exhibit excellent adhesion and adhesion stability, and can maintain excellent durability reliability under heat and moisture and heat resistant conditions .

As the silane coupling agent having a beta-cyano group or an acetoacetyl group, for example, a compound represented by the following formula (1) or (2) can be used.

[Chemical Formula 1]

(R ₁ ) _n Si (R ₂ ) _(4-n)

(2)

(R ₃ ) _n Si (R ₂ ) _(4-n)

Wherein R ₁ is a beta-cyanoacetyl group or a beta-cyanoacetylalkyl group, R ₃ is an acetoacetyl group or an acetoacetylalkyl group, R ₂ is an alkoxy group and n is 1 to 3 ≪ / RTI >

In the general formula (1) or (2), the alkyl group may be an alkyl group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms, and the alkyl group may be linear, branched or cyclic have.

In the general formula (1) or (2), the alkoxy group may be an alkoxy group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms, and the alkoxy group may be linear, Can be.

In Formula 1 or 2, n may be, for example, 1 to 3, 1 to 2, or 1.

Examples of the compound represented by the general formula (1) or (2) include acetoacetylpropyltrimethoxysilane, acetoacetylpropyltriethoxysilane, beta-cyanoacetylpropyltrimethoxysilane or beta-cyanoacetylpropyltriethoxysilane But is not limited thereto.

In the pressure-sensitive adhesive composition, the silane coupling agent may be contained in an amount of 0.01 to 5 parts by weight or 0.01 to 1 part by weight based on 100 parts by weight of the block copolymer, and the desired physical properties may be effectively imparted to the pressure-sensitive adhesive within this range.

The pressure-sensitive adhesive composition may further include a tackifier as necessary. Examples of the tackifier include a hydrocarbon resin or hydrogenated product thereof, a rosin resin or hydrogenated product thereof, a rosin ester resin or hydrogenated product thereof, a terpene resin or hydrogenated product thereof, a terpene phenol resin or hydrogenated product thereof, Polymerized rosin ester resin, and the like, or a mixture of two or more of them may be used, but the present invention is not limited thereto. The tackifier may be contained in the pressure-sensitive adhesive composition in an amount of 100 parts by weight or less based on 100 parts by weight of the block copolymer.

The pressure-sensitive adhesive composition may further include, if necessary, further at least one additive selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, a defoamer, a surfactant and a plasticizer.

The pressure-sensitive adhesive composition may have a coating solid content of 20 wt% or more or 25 wt% or more. As used herein, the term coating solids refers to the solids content of the adhesive composition, i.e., the coating, at the time it is applied to the coating process to form the adhesive. Such coating solids can be measured, for example, in a conventional manner. Usually, at the time of application to the coating process, the pressure-sensitive adhesive composition, that is, the coating liquid includes the above-mentioned block copolymer, cross-linking agent, initiator and other additives, and may also include a solvent. When the solid content of the coating is 20 wt% or more, the productivity of the pressure-sensitive adhesive, optical film, or display device can be maximized. The upper limit of the coating solid content is not particularly limited and can be suitably controlled within a range of, for example, 50 wt% or less, 40 wt% or less, or 30 wt% or less, taking into consideration the viscosity for application to the coating process.

The pressure-sensitive adhesive composition may also have a coating viscosity of about 500 cP to about 3,000 cP at 23 캜. The term coating viscosity refers to the viscosity of the pressure-sensitive adhesive composition, that is, the coating liquid at the time when the pressure-sensitive adhesive composition is applied to the coating process to form the pressure-sensitive adhesive, in the state where the above-described coating solid is maintained. The coating viscosity may range, for example, from 500 cP to 2,500 cP, from 700 cP to 2,500 cP or from 900 cP to 2,300 cP at 23 占 폚. The pressure-sensitive adhesive composition comprising the block copolymer may exhibit a viscosity at a level that enables effective coating even when the coating solid content is set high.

The pressure-sensitive adhesive composition may have a gel fraction of 80% by weight or less after implementing the crosslinked structure. The gel fraction can be calculated by the following general formula (1).

[Formula 1]

Gel fraction (%) = B / A x 100

In the general formula (1), A represents the mass of the pressure-sensitive adhesive composition which implements the crosslinked structure, and B represents the mass of the pressure-sensitive adhesive composition of mass A in a net of 200 mesh, This indicates the dry weight of the insoluble fraction collected after immersion.

By maintaining the gel fraction at 80 wt% or less, workability, durability and reworkability can be maintained. The lower limit of the gel fraction of the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, 0% by weight. However, when the gel fraction is 0% by weight, it does not mean that no crosslinking has proceeded to the pressure-sensitive adhesive composition at all. For example, a pressure-sensitive adhesive composition having a gel fraction of 0 wt% has some degree of crosslinking or crosslinking, but the degree of crosslinking is low, so that the gel can not be retained in the mesh having a size of 200 mesh Leakage may also be included.

The pressure-sensitive adhesive composition may be a pressure-sensitive adhesive composition for an optical film. The pressure-sensitive adhesive composition for an optical film can be obtained by, for example, laminating an optical film such as a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensation film or a brightness enhancement film to each other, And can be used for adhering to complexes. In one example, the pressure-sensitive adhesive composition for a polarizing plate may be a pressure-sensitive adhesive composition used for adhering a polarizing film to a liquid crystal panel.

The present invention also relates to a pressure-sensitive adhesive optical laminate. Exemplary optical stacks include optical films; And a pressure-sensitive adhesive layer formed on one side or both sides of the optical film. The pressure-sensitive adhesive layer may be, for example, a pressure-sensitive adhesive layer for adhering the optical film to a liquid crystal panel or other optical film of an LCD device. The pressure-sensitive adhesive layer may include the pressure-sensitive adhesive composition of the present invention described above. The pressure-sensitive adhesive composition may be contained in the pressure-sensitive adhesive layer in a state of implementing a crosslinked structure. The optical film may be a polarizing film, a retardation film, a brightness enhancement film, or a laminate in which two or more of the above are laminated.

The present invention also relates to an adhesive polarizing plate. The polarizing plate may have, for example, a structure in which the optical film is a polarizing film in the adhesive optical laminate.

The type of the polarizing film included in the polarizing plate is not particularly limited, and a general type known in the art such as a polyvinyl alcohol polarizing film and the like can be employed without limitation.

A polarizing film is a functional film capable of extracting only light vibrating in one direction from incident light while vibrating in various directions. Such a polarizing film may be, for example, a form in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin constituting the polarizing film can be obtained by, for example, gelling a polyvinyl acetate-based resin. In this case, the polyvinyl acetate-based resin that can be used may include not only homopolymers of vinyl acetate but also copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of the monomer copolymerizable with vinyl acetate include monomers such as unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group, or a mixture of two or more thereof. no. The degree of gelation of the polyvinyl alcohol-based resin may be generally from 85 mol% to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be further modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin may be about 1,000 to 10,000 or about 1,500 to 5,000.

The polarizing film is formed by a process of stretching a polyvinyl alcohol resin film as described above (e.g., uniaxially stretching), a process of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, A step of treating the adsorbed polyvinyl alcohol based resin film with an aqueous solution of boric acid and a step of water washing after treatment with an aqueous solution of boric acid. As the dichroic dye, iodine or dichroic organic dyes may be used.

The polarizing plate may further include a protective film attached to one side or both sides of the polarizing film. In this case, the pressure sensitive adhesive layer may be formed on one side of the protective film. The kind of the protective film is not particularly limited and includes, for example, a cellulose-based film such as TAC (triacetyl cellulose); Polycarbonate film or PET (poly (ethylene terephthalate)); Polyethersulfone-based films; Or a polyolefin film produced by using a polyethylene film, a polypropylene film, a resin having a cyclo or norbornene structure, or an ethylene-propylene copolymer, or the like, or a film having a laminate structure of two or more layers.

The polarizing plate may further include at least one functional layer selected from the group consisting of a protective layer, a reflective layer, an antiglare layer, a retardation plate, a wide viewing angle compensation film, and a brightness enhancement film.

The method for forming the pressure-sensitive adhesive layer on the polarizing plate or the optical film as described above is not particularly limited. For example, the pressure-sensitive adhesive composition may be directly coated on the polarizing plate or the optical film and cured to form a crosslinked structure Or a method in which the pressure-sensitive adhesive composition is coated and cured on the release-treated surface of the release film to form a crosslinked structure and then transferred to a polarizing plate or an optical film.

The method of coating the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition may be applied by a conventional means such as a bar coater.

The multifunctional crosslinking agent contained in the pressure-sensitive adhesive composition during the coating process is preferably controlled in such a manner that the crosslinking reaction of the functional groups does not proceed from the viewpoint of performing a uniform coating process. Thus, the crosslinking agent can be crosslinked Structure to improve the cohesive force of the pressure-sensitive adhesive, and improve the adhesive property and cuttability.

The coating process is also preferably performed after sufficiently removing the bubble-inducing component such as volatile components or reaction residues in the pressure-sensitive adhesive composition, and thus the crosslinking density or the molecular weight of the pressure-sensitive adhesive is too low to lower the elastic modulus, It is possible to prevent the problem that the bubbles existing between the glass plate and the adhesive layer become large and scatterers are formed inside.

The method of curing the pressure-sensitive adhesive composition subsequent to the coating to form a crosslinked structure is also not particularly limited. For example, the coating layer may be cured at a suitable temperature such that a cross-linking reaction between the block copolymer contained in the coating layer and the multi- And a method of maintaining the same.

The polarizing plate is excellent in the effect of preventing light leakage due to a warping phenomenon when applied to a liquid crystal display device by causing a crosslinking reaction between a block copolymer contained in the coating layer and a polyfunctional crosslinking agent.

In one example, the polarizing plate may satisfy the following expression (1).

[Equation 1]

ΔW = S ₁ - S ₀ <11 mm

In the formula (1),? W is a change amount of the position of the lower portion of the sample indicating the degree of bending of the adhesive type polarizing plate, S ₁ is a width of 35 mm, and a polarizer having a length of 400 mm A sample having a length of 40 mm and a length of 410 mm and having a thickness of 0.7 mm was attached to the center of the glass and stored for 72 hours under a heat-resistant condition of 60 ° C. And S ₀ is a distance between the reference point and the fixed direction of the sample in a state where the one side of the sample is fixed with a magnet under the condition of 25 ° C, The degree of bending is the distance from the reference point.

The term &quot; reference point &quot; in this specification means a point where the polarizing plate is perpendicularly connected to the bent end point by the bending phenomenon about the surface of the substrate, the coating liquid and the polarizing plate joined together.

In the above formula (1), the lower the? W is, the better the bending property is, and the lower limit is not particularly critical, but may be, for example, 10 mm or less or 9 mm or less.

In one example, the polarizing plate may satisfy the following expression (2).

[Equation 2]

ΔW = S ₁ - S ₀ ≤ 30 mm

In the formula (2),? W is the amount of change in position of the lower portion of the sample indicating the degree of bending of the adhesive type polarizing plate, S ₁ is a width of 35 mm, and a polarizer having a length of 400 mm A length of 40 mm, a length of 410 mm, and a thickness of 0.4 mm, was kept for 72 hours under a heat-resistant condition of 60 ° C, and then a heat-resistant condition of 60 ° C And S ₀ is a distance between the reference point and the fixed direction of the sample in a state where the one side of the sample is fixed with a magnet under the condition of 25 ° C, The degree of bending is the distance from the reference point.

In the above formula (2), the lower the value of? W is, the better the bending property is, and the lower limit is not particularly critical, but may be, for example, 29 mm or less, 28 mm or less, 27 mm or less, 26 mm or less or 25 mm or less.

The invention also relates to a display device, for example an LCD device. Exemplary display devices may include a liquid crystal panel and the polarizing plate or optical laminate attached to one or both sides of the liquid crystal panel. The polarizing plate or the optical laminate may be attached to the liquid crystal panel by the above-described pressure-sensitive adhesive.

Examples of the liquid crystal panel in the apparatus include passive matrix type panels such as TN (twisted nematic) type, STN (super twisted nematic) type, F (ferroelectic) type or PD (polymer dispersed) type; An active matrix type panel such as a two terminal or a three terminal; A known panel such as an in-plane switching (IPS) panel and a vertical alignment (VA) panel may be used.

Other types of liquid crystal display devices, for example, the types of upper and lower substrates such as a color filter substrate or an array substrate are not particularly limited, and configurations known in the art can be employed without limitation.

The pressure-sensitive adhesive composition according to the present invention can form a pressure-sensitive adhesive excellent in endurance reliability, stress relaxation property and reworkability. Incidentally, when the pressure-sensitive adhesive composition is used additionally, the coating process can be efficiently carried out, for example, even when the solid content of the coating is kept high, so that a pressure-sensitive adhesive excellent in productivity and excellent in thickness uniformity can be formed . The pressure-sensitive adhesive composition can be used for an optical film such as a polarizing plate or the like.

Hereinafter, the pressure-sensitive adhesive composition will be described in detail through examples and comparative examples, but the scope of the pressure-sensitive adhesive composition is not limited by the following examples.

1. Evaluation of molecular weight

The number average molecular weight (Mn) and the molecular weight distribution (PDI) were measured using GPC under the following conditions, and the measurement results were converted using a standard polystyrene of Agilent system for the calibration curve.

<Measurement Conditions>

Measuring instrument: Agilent GPC (Agilent 1200 series, U.S.)

Column: Two PL Mixed B connections

Column temperature: 40 ° C

Eluent: THF (Tetrahydrofuran)

Flow rate: 1.0 mL / min

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

2. Coated  evaluation

The pressure-sensitive adhesive compositions prepared in Examples and Comparative Examples were coated, and the coating layer was visually observed and evaluated according to the following criteria.

<Evaluation Criteria>

A: No visible bubbles or streaks on the coating layer.

B: Bubbles and / or stripe pattern were microscopically observed in the coating layer.

C: Bubbles and / or stripe pattern were observed visually in the coating layer.

3. Evaluation of durability

The polarizing plates prepared in Examples and Comparative Examples were cut to have a width of about 180 mm and a length of about 320 mm to prepare specimens, which were then attached to 19-inch commercial panels. Thereafter, the panel is stored in an autoclave (50 DEG C, 5 atmospheres) for about 20 minutes to prepare a sample. The durability against moisture and heat of the samples was evaluated by observing the occurrence of bubbles and peeling at the adhesive interface after the samples were left at 60 ° C and 90% relative humidity for 500 hours. The durability was evaluated at 80 ° C After 500 hours of operation, the occurrence of bubbles and peeling was also observed and evaluated according to the following criteria.

<Evaluation Criteria>

A: No bubbles and peeling occurred

B: Bubbles and / or slight peeling occurred

C: large amount of bubbles and / or peeling occurred

4. Evaluation of flexural characteristics (1)

The flexural properties (1) of the polarizing plate were measured in the following order.

<Flexural Characteristics (1) Measurement Procedure>

1) STN soda lime glass having a width of about 40 mm, a length of about 410 mm, and a thickness of 0.4 mm was prepared, washed cleanly with a solvent such as ethyl acetate or isopropyl acetate to remove foreign matter, dried .

2) Prepare a polarizing plate coated with the coating solution (pressure-sensitive adhesive composition) prepared in Examples and Comparative Examples in the MD (machine direction) direction to prepare a specimen having a width of about 35 mm and a length of about 400 mm.

3) Prepare the sample prepared in 2) in the middle of STN soda lime glass prepared in 1) using a laminator.

4) One side of the sample is fixed with a magnet under a heat-resistant condition of 25 ° C, and the degree of warpage in the opposite direction fixed is measured as a distance (S ₀ ) away from the reference point.

5) After measuring the initial warpage, store it for 72 hours under heat-resistant condition at 60 ℃.

6) Thereafter, the degree of bending of the sample in the chamber is maintained in the same manner as in 4), ie, the degree of bending in the opposite direction fixed to the rat with one side fixed to the magnet, (S ₁ ).

The measured degree of warpage (? W) was expressed by the following formula and evaluated according to the following criteria.

<Formula>

ΔW = S ₁ - S ₀

<Evaluation Criteria>

A: When? W = 30 mm

B: When? W = 40 mm

C: When? W> 40 mm

5. Evaluation of bending characteristics (2)

The flexural properties (2) of the polarizing plate were measured in the following order.

<Flexural characteristics (2) Measurement sequence>

1) STN soda lime glass having a width of about 40 mm, a length of about 410 mm, and a thickness of 0.7 mm was prepared, washed cleanly with a solvent such as ethyl acetate or isopropyl acetate to remove foreign substances, .

2) Prepare a polarizing plate coated with the coating solution (pressure-sensitive adhesive composition) prepared in Examples and Comparative Examples in the MD (machine direction) direction to prepare a specimen having a width of about 35 mm and a length of about 400 mm.

3) Prepare the sample prepared in 2) in the middle of STN soda lime glass prepared in 1) using a laminator.

4) One side of the sample is fixed with a magnet under a heat-resistant condition of 25 ° C, and the degree of warpage in the opposite direction fixed is measured as a distance (S ₀ ) away from the reference point.

5) After measuring the initial warpage, store it for 72 hours under heat-resistant condition at 60 ℃.

6) Thereafter, the degree of bending of the sample in the chamber is maintained in the same manner as in 4), ie, the degree of bending in the opposite direction fixed to the rat with one side fixed to the magnet, (S ₁ ).

The measured degree of warpage (? W) was expressed by the following formula and evaluated according to the following criteria.

<Formula>

ΔW = S ₁ - S ₀

<Evaluation Criteria>

A: When? W = 9 mm

B: when? W = 11 mm

C: when? W> 11 mm

6. Estimation of glass transition temperature

The glass transition temperature (Tg) of each block or the like of the block copolymer was calculated according to the following equation.

<Formula>

1 / Tg =? N / Tn

In the above formula, Wn represents the weight fraction of the monomer used in each block and the like, and Tn represents the glass transition temperature which appears when the monomer used forms a homopolymer.

That is, in the above formula, the value obtained by dividing the weight fraction of the used monomer by the glass transition temperature (Wn / Tn) obtained when the monomer is formed into the homopolymer is calculated for each monomer on the right side to be.

7. Measurement of monomer conversion and composition ratio

(MMA) which is the main monomer forming the first block and the butyl acrylate (BA) which is the main monomer forming the second block in the block copolymers of the examples and the comparative examples and the block copolymer The compositional content in the cohesion was calculated by the following formula according to the results of &lt; 1 &gt; H-NMR.

<Conversion rate of MMA>

MMA conversion ratio (%) = 100 x B / (A + B)

In the above, A is an area of a peak (from 3.4 ppm to 3.7 ppm) derived from a methyl group derived from MMA contained in the polymer in the 1 H-NMR spectrum, and B is a peak derived from the methyl group of un polymerized MMA ). That is, the conversion rate of the monomer was calculated in consideration of the position of the methyl group peak in the structure of MMA.

<BA conversion rate>

BA conversion rate (%) = 100 x C / (C + D)

Where D is the area of a peak (from 5.7 to 6.4 ppm) derived from = CH ₂ of the double bond end of BA in the 1 H-NMR spectrum and C is the area of -OCH ₂ - (the vicinity of 3.8 ppm to 4.2 ppm). That is, the relative conversion of the = CH ₂ peak of BA and the -OCH ₂ -peak of the polymer was calculated and the conversion of BA was measured.

<Calculation of composition ratio>

The ratio of the first and second blocks of the block copolymer is determined based on the ratio of methyl methacrylate (MMA) and butyl acrylate (BA), which are the main monomers used for forming the first block and the second block, .

<Formula>

Content (%) of MMA in block copolymer = 100 x MMA peak area / BA peak area

The MMA peak area is an area value per 1 proton of a peak near 3.4 to 3.7 ppm in 1H-NMR (peak observed by -CH ₃ derived from MMA), and a BA peak area is 3.8 to 4.2 ppm in 1 H-NMR Is the area value per 1H proton of the near peak (peak observed by -OCH ₂ - present in the polymer formed by BA).

That is, the weight ratio of the first and second blocks was calculated by calculating the relative values of the -CH ₃ peak of the MMA structure and the -OCH ₂ -peak of the polymer formed from the BA.

Manufacturing example  1. Preparation of block copolymer (A1)

0.08 g of EBiB (ethyl 2-bromoisobutyrate), 11.2 g of methyl methacrylate (MMA) and 2.8 g of butyl methacrylate (BMA) were mixed in 6.1 g of ethyl acetate (EAc). The flask containing the mixture was sealed with a rubber membrane, purged with nitrogen at about 25 캜 for about 30 minutes and stirred, and dissolved oxygen was removed through bubbling. Thereafter, 0.002 g of CuBr ₂ , 0.005 g of TPMA (tris (2-pyridylmethyl) amine) and 0.016 g of V-65 (2,2'-azobis (2,4-dimethyl valeronitrile) And the reaction was initiated by immersing in a reaction tank at about 67 ° C (polymerization of the first block). A mixture of 151 g of butylacrylate (BA) previously bubbled with nitrogen, 4.7 g of hydroxybutyl acrylate (HBA) and 250 g of ethyl acetate (EAc) was added to the mixture at a time when the conversion of methyl methacrylate was about 75% . &Lt; / RTI &gt; Then, 0.006 g of CuBr ₂ , 0.01 g of TPMA and 0.05 g of V-65 were added to the reaction flask, and a chain extension reaction was carried out (polymerization of the second block). When the conversion of the monomer (BA) reaches 80% or more, the reaction mixture is exposed to oxygen and diluted with an appropriate solvent to terminate the reaction. In this process, V-65 has a half- And the reaction mixture was appropriately divided until the end of the reaction.

Manufacturing example  2 to 7. Preparation of block copolymers (A2 to A3 and B1 to B3)

Except that the raw materials and additives used in the polymerization of the first block were adjusted as shown in Table 1 and the kinds of raw materials and additives used in the polymerization of the second block were adjusted as shown in Table 2 A block copolymer was prepared in the same manner as in Preparation Example 1.

division Raw material EBiB EA CuBr ₂ TPMA V-65 MMA BMA HPMA My
One
The
rock A1 11.2 2.8 - 0.08 6.1 0.002 0.005 0.016 A2 9.4 6.3 - 0.07 6.8 0.002 0.005 0.016 A3 35.8 15.3 - 0.1 22 0.008 0.016 0.055 B1 11.6 2.4 0.4 0.08 6.2 0.002 0.005 0.016 B2 11.6 2.4 0.4 0.08 6.2 0.002 0.005 0.016 B3 5.8 - - 0.1 2.5 0.001 0.002 0.007

division Raw material EA CuBr ₂ TPMA V-65 BA HBA My
2
The
rock A1 151 4.7 250 0.006 0.01 0.05 A2 146 9.3 250 0.006 0.01 0.05 A3 113 5.9 234 0.0002 0.0004 0.047 B1 156 - 250 0.006 0.01 0.05 B2 151 4.7 250 0.006 0.01 0.05 B3 163 0.8 250 0.006 0.01 0.05

The properties of each block copolymer prepared in the above manner are shown in Table 3 below.

division Block copolymer A1 A2 A3 B1 B2 B3 The first block MMA ratio 80 60 70 81 81 100 BMA ratio 20 40 30 16 16 0 HPMA ratio 0 0 0 3 3 0 Tg (占 폚) 90 72 80 90 90 110 Mn (x 10000) 2.3 2.9 3.8 2.3 2.3 0.8 PDI 1.34 1.38 1.41 1.36 1.36 1.18 The second block BA ratio 97.0 94.0 95.0 100 87.0 99.5 HBA ratio 3.0 6.0 5.0 0 13.0 0.5 Tg (占 폚) -46.2 -47.5 -47.0 -45 -44.2 -47.0 block
Copolymer Mn (x 10000) 12.3 14.1 10.4 12.4 12.3 10.1 PDI 1.8 2.1 2.1 1.8 1.9 1.6 Monomer ratio Unit: parts by weight
MMA: methyl methacrylate (homopolymer Tg: about 110 ° C)
BMA: butyl methacrylate (homopolymer Tg: about 27 ° C)
HPMA: 2-hydroxypropyl methacrylate (homopolymer Tg: about 26 ° C)
BA: butyl acrylate (homopolymer Tg: about -45 ° C)
HBA: 4-hydroxybutyl acrylate (homopolymer Tg: about -80 ° C)
Tg: glass transition temperature
Mn: number average molecular weight
PDI: molecular weight distribution

Manufacturing example  8. Preparation of random copolymer (B4)

10 parts by weight of methyl methacrylate (MMA), 87.3 parts by weight of n-butyl acrylate, and 2.7 parts by weight of 4-hydroxybutyl acrylate were charged into a 1 L reactor equipped with a cooling device to easily regulate the temperature and nitrogen gas was refluxed , N-dodecyl mercaptan as a molecular weight regulator was added in an amount of 200 ppm, and 120 parts by weight of ethyl acetate was added as a solvent. Next, nitrogen gas was purged for about 60 minutes to remove oxygen, 0.05 parts by weight of AIBN (azobisisobutyronitrile) as a reaction initiator was added while maintaining the temperature at 60 占 폚, and the reaction was carried out for about 8 hours to prepare a random copolymer. The number average molecular weight (Mn) of the prepared random copolymer (B4) was about 132,000 and the molecular weight distribution (PDI) was about 4.6.

Example  One

Preparation of coating liquid (pressure-sensitive adhesive composition)

To 100 parts by weight of the block copolymer (A1) prepared in Preparation Example 1 were added 0.04 part by weight of a crosslinking agent (Coronate L, manufactured by NPU of Japan), 0.1 part by weight of DBTDL (Dibutyltin dilaurate) and 0.2 part by weight of a silane coupling agent having a? And ethyl acetate as a solvent were mixed to prepare a coating liquid (pressure-sensitive adhesive composition) by adjusting the coating solid content to about 33% by weight.

Production of adhesive polarizer

The prepared coating solution was coated on a release-treated surface of a poly (ethylene terephthalate) (MRF-38, manufactured by Mitsubishi) having a thickness of 38 탆 and subjected to release treatment so that the thickness after drying was about 23 탆, For about 3 minutes. After drying, a WV liquid crystal layer of a polarizing plate (TAC / PVA / TAC laminated structure: TAC = triacetyl cellulose, PVA = polyvinyl alcohol polarizing film) coated with a WV (Wide View) The formed coating layer was laminated to prepare a pressure-sensitive polarizer.

Example  2 to 4 and Comparative Example  1 to 5

A pressure-sensitive adhesive composition (coating solution) and a pressure-sensitive polarizer were prepared in the same manner as in Example 1, except that components and ratios were adjusted as shown in Table 4 in the preparation of the pressure-sensitive adhesive composition (coating solution).

division Example Comparative Example One 2 3 4 One 2 3 4 5 acryl
polymer Kinds A1 A1 A2 A3 B4 B1 B2 B3 A3 content 100 100 100 100 100 100 100 100 100 Crosslinker content 0.04 0.5 0.2 0.2 0.07 0.07 0.07 0.07 1.5 DBTDL content 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 SCA content 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Content Unit: parts by weight
Cross-linking agent: Coronate L, Japan NPU
DBTDL: dibutyltin dilaurate
SCA: Silane coupling agent having a? -Cyano acetyl group (M812, manufactured by LG Chemical)

The evaluation results of the physical properties of each of the above Examples and Comparative Examples are shown in Table 5 below.

division Example Comparative Example One 2 3 4 One 2 3 4 5 Coating property A A A A A A A A A Heat resistance durability A A A A C C B C B Wet heat resistance A A A A B C B C B Flexural properties (1) A A A A C B C B C Flexural properties (2) A A A A C C C B C

Claims (18)

5 to 50 parts by weight of a first block having a glass transition temperature of 60 to 100 DEG C and containing polymerized units derived from a methacrylic acid ester monomer; And 50 to 95 parts by weight of a second block having a glass transition temperature of -10 占 폚 or less and containing a crosslinkable functional group, wherein the crosslinkable functional group is contained in the first block Wherein the methacrylic acid ester monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t- Butyl methacrylate, butyl methacrylate, sec-butyl methacrylate, pentyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylbutyl methacrylate, n-octyl methacrylate, isobornyl methacrylate, Acrylonitrile, acrylonitrile, methacrylonitrile, methacrylonitrile, acrylonitrile, methacrylonitrile, methacrylonitrile, acrylonitrile, methacrylonitrile, delete The pressure-sensitive adhesive composition according to claim 1, wherein the crosslinkable functional group is a hydroxy group. delete The pressure-sensitive adhesive composition according to claim 1, wherein the second block comprises polymerized units derived from 90 parts by weight to 99.9 parts by weight of an acrylic acid ester monomer and 0.1 part by weight to 10 parts by weight of a copolymerizable monomer having a crosslinkable functional group. The pressure-sensitive adhesive composition according to claim 1, wherein the first block has a number-average molecular weight of 2,500 to 150,000. The pressure-sensitive adhesive composition according to claim 1, wherein the block copolymer has a number average molecular weight of 50,000 to 300,000. The pressure-sensitive adhesive composition according to claim 1, wherein the block copolymer has a molecular weight distribution of 1.0 to 2.5. The pressure-sensitive adhesive composition according to claim 1, wherein the block copolymer is a diblock copolymer having a first block and a second block. The pressure-sensitive adhesive composition according to claim 1, further comprising a multifunctional crosslinking agent having two or more functional groups capable of reacting with the crosslinkable functional group. The pressure-sensitive adhesive composition according to claim 10, wherein the multifunctional crosslinking agent is contained in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the block copolymer. The pressure-sensitive adhesive composition according to claim 1, wherein the coating solid content is 20% by weight or more. The pressure-sensitive adhesive composition according to claim 1, wherein the coating viscosity at 23 DEG C is 500 cP to 3,000 cP. The pressure-sensitive adhesive composition according to claim 1, wherein the gel fraction after implementing the crosslinked structure is 80% by weight or less. Optical film; And an adhesive layer which is present on one side or both sides of the optical film and which is formed from the pressure-sensitive adhesive composition of claim 1. Polarizing film; And a pressure-sensitive adhesive layer which is present on one side or both sides of the polarizing film and which is formed from the pressure-sensitive adhesive composition of claim 1. The adhesive type polarizing plate according to claim 16, wherein the pressure-sensitive adhesive composition is contained in the pressure-sensitive adhesive layer in a state of realizing a crosslinked structure. A display device comprising the adhesive optical laminate of claim 15 or the adhesive polarizer of claim 16 attached to one or both surfaces of a liquid crystal panel.