KR20200131580A - Optical laminate and display device - Google Patents

Abstract

The present application relates to an optical film having an adhesive layer that provides excellent optical compensation without deterioration in durability under high temperature and/or high humidity conditions.

Description

Optical laminate and display device including the same

The present application relates to an optical laminate and a display device including the same.

A liquid crystal display device (hereinafter referred to as "LCD") typically includes a liquid crystal panel and an optical film including a liquid crystal component injected between two transparent substrates. Examples of the optical film include a polarizing film, a retardation film, or a brightness improving film. A pressure-sensitive adhesive for an optical film may be used to laminate these optical films to each other or to attach the optical film to an adherend such as a liquid crystal panel.

Since the materials forming each of the aforementioned optical films have different molecular structures or compositions from each other, these optical films also have different physical properties from each other. For example, films using a material having a one-way molecular arrangement under high temperature and/or high temperature and high humidity conditions lack dimensional stability due to shrinkage or expansion. Specifically, when a polarizing plate and other optical members such as the optical film are fixed by an adhesive, and these laminates are placed in high temperature and/or high temperature and high humidity conditions, stress is concentrated on the polarizing plate due to contraction or expansion of the polarizing plate. As a result, birefringence occurs and light leakage is observed. With the trend of increasing the size of the polarizing plate due to the increase in the size of the LCD panel, the degree of contraction, residual stress, birefringence, and light leakage of the polarizing plate described above are getting worse.

In order to minimize light leakage, optical compensation is required that adjusts the negative birefringence of the adhesive caused by residual stress to positive birefringence.

Prior Document 1 (Korean Patent Publication No. 10-2003-0069461) corrects the negative birefringence exhibited by the acrylic adhesive layer under residual stress by mixing 0.01 to 40 parts by weight of a low molecular weight substance showing positive birefringence under residual stress into the acrylic adhesive layer. Suggest a technique to do. However, due to the use of a low molecular weight material, the modulus of the pressure-sensitive adhesive is lowered, so that there is a problem of cutting properties when working with a polarizing plate, and during long-term storage, there is a problem that the low molecular weight material moves to the interface and phase-separates from the acrylic pressure-sensitive adhesive as the main component. In addition, due to the plasticizing effect of the low molecular weight body, the Mc (average molecular weight between cross-linking points) in the cross-linked structure substantially increases, resulting in a smaller residual stress, resulting in less orientation of the low molecular weight body. A large amount of low molecular weight material is required.

Prior Document 2 (Korean Patent Laid-Open No. 10-2004-0030597) discloses a technique for improving the plasticizing resistance of an adhesive layer by introducing an acrylic monomer containing an aromatic group in a side chain. In addition, Prior Document 3 (Korean Patent Publication No. 10-2002-0044070) and Prior Document 4 (Korean Patent Publication No. 10-2003-0004119) introduced an acrylic monomer containing an aromatic group in the side chain to obtain the refractive index of the pressure-sensitive adhesive layer. Disclosed is a method of controlling However, in the method of supplementing light leakage disclosed in these prior documents, a large amount of aromatic-containing acrylic monomers are required.When a large amount of aromatic-containing acrylic monomers are used, the adhesive strength of the pressure-sensitive adhesive increases significantly, which adversely affects re-peelability, which is the main function of the pressure-sensitive adhesive for a polarizing plate. In addition, when a large amount of aromatic-containing acrylic monomer is used, there is also a problem that the durability of the pressure-sensitive adhesive decreases.

An object of the present application is to solve the problems of the prior art as described above.

Another object of the present application is to provide an adhesive-type optical laminate and display device having excellent durability and re-peelability.

Another object of the present application is to provide an adhesive optical laminate and a display device in which the yellowing phenomenon is suppressed.

Another object of the present application is to provide an adhesive optical laminate and a display device in which light leakage is suppressed under high temperature and/or high temperature and high humidity conditions.

All of the above and other objects of the present application can be solved by the present application described in detail below.

In an example related to the present application, the present application relates to an adhesive optical laminate. The pressure-sensitive adhesive optical laminate having the configuration described below may have light leakage stability because the pressure-sensitive adhesive effectively has positive birefringence under residual stress. In addition, the adhesive optical laminate of the following configuration not only has excellent durability and adhesive strength, but also has properties in which yellowing is suppressed.

The optical laminate includes an optical film, a first adhesive layer, and a second adhesive layer in sequence. In this case, the first adhesive layer may include a block copolymer (A) having an aromatic group, and the second adhesive layer may include a random copolymer (B) having a polymerization unit derived from a carboxyl group-containing (meth) acrylic acid ester. .

In one example, as the optical film, a polarizing plate, a polarizer, a retardation film, a brightness enhancing film, an anti-glare film, a wide viewing angle compensation film, etc., or a laminate in which two or more of the above are laminated may be exemplified. In the present application, the terms'polarizer' and'polarizing plate' refer to objects that are distinguished from each other. That is, the polarizer refers to a film, sheet, or device itself exhibiting a polarizing function, and the polarizing plate refers to an optical device including other elements together with the polarizer. Other elements that may be included in the optical element together with the polarizer may include a polarizer protective film or a retardation layer, but are not limited thereto.

In one example, the optical film used for the adhesive-type optical laminate may be a polarizer.

The type of polarizer included in the polarizing plate is not particularly limited, and for example, a general type known in the related art such as a polyvinyl alcohol polarizer may be employed without limitation.

The polarizer is a functional film capable of extracting only light vibrating in one direction from incident light while vibrating in various directions. Such a polarizer may be, for example, in 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 polarizer can be obtained, for example, by gelling a polyvinyl acetate-based resin. In this case, the polyvinyl acetate-based resin that can be used may include a homopolymer of vinyl acetate, as well as a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of the monomers copolymerizable with vinyl acetate may include one or more mixtures of unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and acrylamides having an ammonium group, but are limited thereto. no. The degree of gelation of the polyvinyl alcohol-based resin may be generally about 85 mol% to 100 mol%, and 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 generally about 1,000 to 10,000 or about 1,500 to 5,000.

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

In addition to the polarizer, the polarizing plate may include a protective film and/or an optical functional film.

In one example, the polarizing plate may include a protective film attached to one or both surfaces of the polarizer, and in this case, the adhesive layer of the configuration described above may be formed on one or both surfaces of the protective film. The type of the protective film is not particularly limited. For example, the protective film may be a glass substrate, or may be a substrate containing a polymer component. For example, a cellulose-based film such as TAC (Triacetyl cellulose); Polyester-based films such as polycarbonate films or PET (poly(ethylene terephthalet)); Polyethersulfone film; Alternatively, a film having a single or two or more layered structure, such as a polyethylene film, a polypropylene film, or a polyolefin-based film prepared using a resin having a cyclo-based or norbornene structure, or an ethylene-propylene copolymer, may be used as the protective film. The protective film may have two or more stacked structures.

In one example, the polarizing plate may further include one or more optical functional films selected from the group consisting of a reflective film, an anti-glare film, a retardation film, a wide viewing angle compensation film, and a brightness enhancing film. The optical functional film may have two or more stacked structures.

In one example, the polarizing plate may include at least one wide viewing angle compensation film selected from ±A film, ±B film, and ±C film. In the present application,'A film' refers to a film that satisfies the refractive index of the film nx ≠ny = nz. In this case, a case of nx> ny is referred to as a +A film, and a case of nx <ny is referred to as a -A film. . The'B film' refers to a film whose refractive index satisfies nx ≠ny ≠ nz, where nx> ny> nz is called -B film, and nz> nx> ny is called +B film. The'C film' refers to a film in which the refractive index of the film satisfies nx = ny ≠nz. In this case, a case of ny <nz is referred to as a +C film, and a case of ny> nz is referred to as a -C film. In this regard, nx means the refractive index in the slow axis direction in the plane direction of the film or plate, ny means the refractive index in the direction perpendicular to the slow axis in the plane direction of the film or plate, and nz is the film Or it means the refractive index in the thickness direction of the plate.

In one example, the polarizing plate may include a retardation film. The retardation layer may be, for example, a quarter wave plate (QWP). The quarter wave plate may have a quarter wave phase delay characteristic. In the present specification, the term n-wavelength phase delay property refers to a property capable of retarding incident light by n times the wavelength of the incident light within at least a partial wavelength range. The quarter-wavelength phase delay characteristic may be a characteristic of converting incident linearly polarized light into elliptical polarized light or circularly polarized light, and conversely converting incident elliptical polarized light or circularly polarized light into linearly polarized light. As the quarter wave plate, a quarter wave plate generally manufactured and distributed in the related art field may be used. For example, a uniaxially stretched cycloolefin-based film, a uniaxially stretched polyethylene terephthalate film, a uniaxially stretched polycarbonate film, or a liquid crystal film may be used without limitation.

In one example, the optical laminate may further include a glass substrate. In this case, the adhesive layer may be positioned between the optical film and the glass substrate. Specifically, the optical laminate may sequentially include a polarizer, a first adhesive layer, a second adhesive layer, and a glass substrate.

In one example, the glass substrate may be included in the optical film. For example, when the optical film is a polarizing plate, the glass substrate may be a kind of protective film to protect the polarizer, and the adhesive layer is used to attach the polarizer and the glass substrate, or the side opposite the glass substrate where the glass substrate and the polarizer contact It can be placed on top and used to bond other members to the glass substrate.

In another example, the glass substrate may have a configuration separate from the optical film. For example, the glass substrate may be a part of a liquid crystal panel as a component that confines a liquid crystal layer, and in this case, the adhesive layer may be used to attach a polarizing plate and a liquid crystal panel.

The first adhesive layer positioned on the optical film includes a block copolymer (A) having an aromatic group. The aromatic group included in the first adhesive layer adjacent to the polarizer may be effectively disposed according to the change in the size of the polarizer under high temperature conditions, thereby contributing to light leakage suppression.

Specifically, the inventor of the present application is that when the stress generated when the polarizing plate shrinks under heat-resistant conditions such as high temperature and/or high humidity is transmitted to the adhesive, the chain inside the adhesive is aligned to suppress light leakage. It is necessary to induce alignment of aromatics, but when the adhesive layer containing aromatic groups is located far from the polarizer, stress is not transmitted to the adhesive containing aromatic groups, and as a result, alignment of aromatic groups is not performed properly, reducing the ability to suppress light leakage. Confirmed. Accordingly, in the present application, the first adhesive layer positioned on the optical film includes a block copolymer (A) having an aromatic group.

In the present application, that the adhesive layer includes a copolymer means that the adhesive layer is formed from a composition containing the copolymer.

In addition, the term "block copolymer" in the present application may refer to a copolymer including blocks of different polymerized monomers.

The block copolymer (A) may include a first block and a second block having different glass transition temperatures.

Specifically, the block copolymer includes a first block having a glass transition temperature of 50° C. or higher; And a second block having a glass transition temperature of -10 °C or less. In the present application, the "glass transition temperature of a block" constituting the block copolymer is a glass transition temperature of a polymer formed only of monomers included in the block, and may be calculated according to the method described in the following examples.

In one example, the glass transition temperature of the first block may be 50°C or higher, 60°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, or 85°C or higher. The upper limit of the first block glass transition temperature is not particularly limited, but, for example, 150°C or less, 140°C or less, 130°C or less, 120°C or less, 110°C or less, 100°C or less, 95°C or less, or 90°C or less It can be about. In the present application, the first block having a relatively high glass transition temperature may form a hard segment having relatively rigid physical properties in the block copolymer. The first block may exist in a glass form at room temperature, and may serve to impart a cohesive force to an adhesive including the block copolymer.

In one example, the glass transition temperature of the second block may be -10°C or less, -20°C or less, -30°C or less, -35°C or less, -40°C or less, or -45°C or less. The lower limit of the second block glass transition temperature is not particularly limited, but may be, for example, -80°C or higher, -70°C or higher, -60°C, -55°C or higher, -50°C or higher, or -45°C or higher. . The second block having a relatively low glass transition temperature may form a soft segment having soft physical properties in the block copolymer. The second block may have molecular flow at room temperature, and may serve to impart stress relaxation properties to the pressure-sensitive adhesive including the block copolymer.

The copolymer including both blocks satisfying the glass transition temperature range may form a fine phase-separated structure in the adhesive. Since the block copolymer exhibits adequate cohesive force and stress relaxation properties according to temperature changes, it forms a pressure-sensitive adhesive that maintains excellent physical properties required for optical films such as interfacial adhesion, high temperature durability reliability, light leakage prevention properties, and reworkability. can do.

In one example, the block copolymer of the present application including the two blocks may be a diblock copolymer or a triblock copolymer. In consideration of the interfacial adhesion of the pressure-sensitive adhesive, high temperature durability reliability, stress relaxation property and reworkability, a diblock copolymer may be advantageous.

In one example, the block copolymer may include a first block and a second block each having a specific functional group. Specifically, the block copolymer (A) has a glass transition temperature of 50° C. or higher, and a first block having an aromatic group; And a second block having a glass transition temperature of -10° C. or less and having a crosslinkable functional group. The types of monomers or compounds that can provide the functional group contained in the block will be described in detail below.

As long as it has the specific functional group described above and can simultaneously have the glass transition temperature described above, the type or content of the monomer for forming each block is not particularly limited.

In one example, the first block and the second block may include a polymerization unit derived from a (meth)acrylic acid ester. In the present application, the term "polymerization unit" may mean a state in which the predetermined monomer is polymerized and contained in a resin, a polymer, or a main chain or side chain of a polymerization reactant formed by polymerization of a predetermined monomer.

As the (meth)acrylic acid ester used for forming the first block, for example, alkyl (meth) acrylate may be used. In consideration of cohesion, glass transition temperature, and adhesion control, an alkyl (meth)acrylate having 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 may be used. have. Examples of such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate )Acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate, iso Bornyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate and lauryl (meth) acrylate, etc., and one or more of the above has the glass transition temperature You can choose and use it as much as possible.

In one example, as a monomer forming the first block in consideration of the ease of controlling the glass transition temperature, etc., among the monomers, a methacrylic acid ester monomer, for example, 1 to 20 carbon atoms, 1 to 16 carbon atoms, and 1 carbon number Alkyl methacrylate having an alkyl group having 1 to 12 carbon atoms or 1 to 4 carbon atoms may be used.

In one example, the first block may include a polymerization unit derived from an alkyl methacrylate and a polymerization unit derived from an aromatic group-containing alkyl (meth)acrylate.

The kind of the aromatic group-containing alkyl (meth)acrylate is not particularly limited, but, for example, benzyl (meth)acrylate or 2-phenoxy ethyl (meth)acrylate may be used. In addition, one or more of the above compounds may be used.

The first block of the first adhesive layer having an aromatic group has excellent durability under high temperature conditions due to a high glass transition temperature. In particular, in the case where the stress due to the change in the size of the polarizing plate is concentrated in the pressure-sensitive adhesive under a temperature condition higher than the first block glass transition temperature, the aromatic groups can be effectively aligned by unwinding the chain of the first block, so that the content of the polymerization unit having an aromatic group is reduced. Even if it is small, it can be effective in reducing light leakage. Designing to include an aromatic group in the first block is advantageous in that the light leakage effect can be sufficiently exhibited even with a smaller amount than that of including an aromatic group in the second block.

In addition, as mentioned above, the light leakage improvement effect is achieved by aligning the aromatic groups randomly entangled in the copolymer by the stress applied by the shrinkage of the polarizing plate.If the aromatic group is included in the second adhesive layer, the durability condition (e.g. For example, under high temperature conditions such as about 95°C, or high temperature/high humidity conditions such as 65°C and 95% relative humidity), stress generated by shrinkage of the polarizing plate may be weakened as it is transmitted to the second adhesive layer via the first adhesive layer. Accordingly, there is a problem that the alignment of the aromatic groups is not sufficiently generated and the effect of improving light leakage is insufficient.

In one example, the compound providing an aromatic group to the first block may be an aromatic group-containing alkyl methacrylate. For example, benzyl methacrylate or 2-phenoxy ethyl methacrylate can be used.

In one example, based on the total weight of the first block, the first block may contain 50 parts by weight or less of a polymerization unit derived from an aromatic group-containing alkyl (meth)acrylate. Specifically, the content of the polymerization unit derived from the aromatic group-containing alkyl (meth)acrylate may be, for example, 45 parts by weight or less, 40 parts by weight or less, or 35 parts by weight or less. More specifically, the content of the polymerized unit derived from the aromatic group-containing alkyl (meth)acrylate is 34 parts by weight or less, 33 parts by weight or less, 32 parts by weight or less, 31 parts by weight or less, 30 parts by weight or less, 29 parts by weight or less , 28 parts by weight or less, 27 parts by weight or less, 26 parts by weight or less, 25 parts by weight or less, 24 parts by weight or less, 23 parts by weight or less, 22 parts by weight or less, 21 parts by weight or less, or 20 parts by weight or less. The lower limit of the content of the polymerization unit derived from a monomer capable of providing an aromatic group is not particularly limited, but may be, for example, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more.

In one example, the first block may include 50 to 95 parts by weight of a polymerization unit derived from an alkyl (meth) acrylate and 5 parts by weight to 50 parts by weight of a polymerization unit derived from an aromatic group-containing alkyl (meth) acrylate. .

In one example, the first block is an alkyl (meth)acrylate, a polymerization unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and an alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms It may contain a polymerization unit of. In the case of having the above configuration, it may be advantageous in improving the high temperature durability of the pressure-sensitive adhesive. Specifically, since the alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms can cause chain entanglement more easily than an alkyl (meth)acrylate having 4 or more carbon atoms of the alkyl group, physical entanglement can occur instead of chemical crosslinking. Crosslinking can be sufficiently imparted to the adhesive resin, thereby providing an adhesive layer excellent in high temperature durability. In this case, the first block is a polymerization unit derived from 45 to 75 parts by weight of an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms, 5 to 20 parts by weight of an alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms, and It may contain 5 parts by weight to 50 parts by weight of a polymerization unit derived from an aromatic group-containing alkyl (meth)acrylate. Although not particularly limited, the alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms may be an alkyl methacrylate having an alkyl group having 1 to 3 carbon atoms, and the alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms is And an alkyl methacrylate having an alkyl group having 4 or more carbon atoms.

In one example, the first block may include only the polymerization unit of the (meth)acrylic acid ester described above, specifically an alkyl (meth)acrylate, and more specifically an alkyl methacrylate.

In one example, unlike the second block described below, the first block may not include a unit derived from a monomer having a crosslinkable functional group.

In one example, the number average molecular weight (Mn) of the first block of the block copolymer may range from 2,500 to 150,000. The number average molecular weight of the first block may be, for example, the number average molecular weight of a polymer prepared by polymerizing only the monomers forming the first block. The number average molecular weight referred to in the present application can be measured according to the method presented in the following experimental examples using, for example, GPC (Gel Permeation Chromatograph). More specifically, the number average molecular weight (Mn) of the first block is, for example, the lower limit of 10,000 or more, 15,000 or more, 20,000 or more, 25,000 or more, 30,000 or more, 35,000 or more, 40,000 or more, 45,000 or more, or 50,000 or more. I can. More specifically, the lower limit of the number average molecular weight (Mn) of the first block may be, for example, 55,000 or more, 6,000 or more, 65,000 or more, 70,000 or more, 75,000 or more, 80,000 or more, 85,000 or more, 90,000 or more, or 95,000 or more. have. And the upper limit may be 145,000 or less, 140,000 or less, 135,000 or less, 130,000 or less, 125,000 or less, 120,000 or less, 115,000 or less, 110,000 or less, 105,000 or less, 100,000 or less, 95,000 or less, or 90,000 or less.

In another example, the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the first block (Mw/Mn), that is, the molecular weight distribution (PDI=Mw/Mn) may be in the range of 1.0 to 3.0. . More specifically, the lower limit of the PDI value of the first block may be, for example, 1.00 or more, 1.05 or more, 1.15 or more, 1.20 or more, 1.25 or more, 1.30 or more, 1.35 or more, 1.40 or more, 1.45 or more, or 1.50 or more. And the upper limit may be, for example, 2.5 or less or 2.0 or less, and more specifically 1.95 or less, 1.90 or less, 1.85 or less, 1.80 or less, 1.75 or less, 1.70 or less, 1.65 or less, 1.60 or less, 1.55 or less, or 1.50 or less I can.

In one example, as the (meth)acrylic acid ester used for forming the second block, for example, as in the first block, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to carbon atoms Alkyl (meta) acrylate having an alkyl group of 8 or 1 to 4 carbon atoms can be used.

In the present application, the second block may include a crosslinkable functional group that reacts with a crosslinking agent described below to form a crosslinked structure of the pressure-sensitive adhesive. When the crosslinkable functional group is included in the second block, it exhibits appropriate cohesive force and stress relaxation properties according to temperature changes to form a pressure-sensitive adhesive that maintains excellent physical properties such as interfacial adhesion, high temperature durability reliability, light leakage prevention properties, and reworkability. can do.

In one example, the second block may include a polymerization unit derived from 60 to 99.9 parts by weight of a methacrylic acid ester monomer and 0.1 to 40 parts by weight of a copolymerizable monomer having a crosslinkable functional group. Specifically, the copolymerizable monomer having a crosslinkable functional group may be used in an amount of 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less. have. More specifically, the copolymerizable monomer having a crosslinkable functional group may be used in an amount of 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, or 1.5 parts by weight or less.

In one example, the (meth)acrylic acid ester used for forming the second block may be an alkyl acrylate. Specific types of alkyl acrylates are the same as those described for the first block.

The kind of crosslinkable functional group is not specifically limited. For example, it may be a carboxyl group, a sulfonic acid group, a phosphate group, or a hydroxy group.

In one example, the crosslinkable functional group may be a hydroxy group (-OH). For example, the second block may include a polymerization unit derived from a hydroxy group-containing alkyl (meth)acrylate monomer. Alternatively, for example, the second block may include a polymerization unit derived from a hydroxy group-containing alkyl acrylate monomer.

In one example, the second block may include a hydroxy group (-OH) and may have a polymerization unit derived from a copolymerizable monomer represented by Formula 1 below.

[Formula 1]

However, in Formula 1, Q is hydrogen or an alkyl group, A and B are each independently an alkylene group or an alkylidene group, and n is an integer within the range of 0 to 10. In addition, when there are two or more [-O-B-] units in Formula 1, the number of carbon atoms of B in each [-O-B-] unit may be the same or different.

In the present specification, the term ``alkyl group'' is a linear, branched or cyclic 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 unless otherwise specified. It may mean, and the alkyl group may be optionally substituted with one or more substituents. As the alkyl group in Formula 1, a straight or branched alkyl group having 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms may be exemplified. Although not particularly limited, when Q in Formula 1 is an alkyl group, Q may be an alkyl group having 1 to 4 carbon atoms.

In the present specification, the term "alkylene group" or "alkylidene group" is a straight chain 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 unless otherwise specified. , It may mean a branched or cyclic alkylene group or an alkylidene group, and the above may be optionally substituted by one or more substituents. Although not particularly limited, in Formula 1, for example, A and B may each independently be a linear alkylene group having 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms.

In addition, n in Formula 1 may be, for example, 0 to 7, 0 to 5, 0 to 3, or 0 to 2.

Examples of the compound of Formula 1 include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. ) Acrylate or hydroxy alkyl (meth) acrylate such as 8-hydroxyoctyl (meth) acrylate, and the like may be used. Or, hydroxyalkylene glycol (meth)acrylate such as 2-hydroxyethylene glycol (meth)acrylate or 2-hydroxypropylene glycol (meth)acrylate may be exemplified as a compound of Formula 1, but the compounds listed above It is not particularly limited to these.

In one example, in consideration of the reactivity of the monomer or the ease of controlling the glass transition temperature, hydroxyalkyl acrylate or hydroxyalkylene glycol acrylate may be used as the compound represented by Formula 1 above.

In one example, unlike the first block described above, the second block may not include a polymerization unit derived from an aromatic group-containing monomer.

In one example, the second block may include only a polymerization unit derived from a (meth)acrylic acid ester monomer and a copolymerizable monomer having a crosslinkable functional group.

In one example, the second block may include a polymerization unit derived from an alkyl acrylate. Alternatively, the second block may contain only a polymerization unit derived from an alkyl acrylate.

In one example, the first block may include a polymerization unit derived from an alkyl methacrylate, and the second block may include a polymerization unit derived from an alkyl acrylate. The first block including the alkyl methacrylate has a high glass transition temperature and is advantageous for securing durability, and the second block including the alkyl acrylate has a low glass transition temperature, so it may be advantageous to implement adhesive performance.

The first block and/or the second block may further include a polymerization unit derived from any other comonomer, if necessary, for example, for control of a glass transition temperature. Such optional comonomers include (meth)acrylonitrile, (meth)acrylamide, N-methyl (meth)acrylamide, N-butoxy methyl (meth)acrylamide, N-vinyl pyrrolidone or N- Nitrogen-containing monomers such as vinyl caprolactam; Alkoxy alkylene glycol (meth)acrylic acid ester, alkoxy dialkylene glycol (meth)acrylic acid ester, alkoxy trialkylene glycol (meth)acrylic acid ester, alkoxy tetraalkylene glycol (meth)acrylic acid ester, alkoxy polyethylene glycol (meth)acrylic acid Ester, phenoxy alkylene glycol (meth) acrylic acid ester, phenoxy dialkylene glycol (meth) acrylic acid ester, phenoxy trialkylene glycol (meth) acrylic acid ester, phenoxy tetraalkylene glycol (meth) acrylic acid ester or phenoxy Alkylene oxide group-containing monomers such as polyalkylene glycol (meth)acrylic acid ester; Styrene-based monomers such as styrene or methyl styrene; Glycidyl group-containing monomers such as glycidyl (meth)acrylate; Or a carboxylic acid vinyl ester such as vinyl acetate, but is not limited thereto. These comonomers may be used in an amount of, for example, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less based on the total weight of the block in each block. When any comonomer is used, the lower limit of its content may be, for example, 0.1 parts by weight.

In one example, the block copolymer may have a number average molecular weight (Mn) of 300,000 or less. More specifically, the number average molecular weight (Mn) of the block copolymer is, for example, its lower limit is 50,000 or more, specifically 55,000 or more, 60,000 or more, 65,000 or more, 70,000 or more, 75,000 or more, 80,000 or more, 85,000 or more, It may be 90,000 or more, 95,000 or more, or 100,000 or more. More specifically, the lower limit of the number average molecular weight (Mn) of the block copolymer is, for example, 110,000 or more, 115,000 or more, 120,000 or more, 125,000 or more, 130,000 or more, 135,000 or more, 140,000 or more, 145,000 or more, 150,000 or more, 155,000 or more. , 160,000 or more, 165,000 or more, 170,000 or more, 175,000 or more, 180,000 or more, 185,000 or more, 190,000 or more, 195,000 or more, 200,000 or more, 210,000 or more, 215,000 or more, 220,000 or more, 225,000 or more, or 230,000 or more. And the upper limit may be, for example, 295,000 or less, more specifically 290,000 or less, 285,000 or less, 280,000 or less, 275,000 or less, 270,000 or less, 265,000 or less, 260,000 or less, 255,000 or less, 250,000 or less, 245,000 or less, or 240,000 or less. .

In another example, the molecular weight distribution (PDI=Mw/Mn) of the block copolymer may range from 1.5 to 3.5. Specifically, the lower limit of the molecular weight distribution of the block copolymer may be, for example, 2.0 or more or 2.5 or more. More specifically, the lower limit is 2.55 or more, 2.60 or more, 2.65 or more, 2.70 or more, 2.75 or more, 2.80 or more, 2.85 or more, 2.90 or more, 2.95 or more, 3.00 or more, 3.05 or more, 3.10 or more, 3.15 or more, 3.20 or more, 3.25 It may be greater than or equal to 3.30. And, the upper limit may be, for example, 3.45 or less, 3.40 or less, 3.35 or less, 3.30 or less, 3.25 or less, 3.20 or less, 3.15 or less, or 3.10 or less.

As described above, when the molecular weight characteristics of the block copolymer are adjusted, a pressure-sensitive adhesive that maintains excellent physical properties required for an optical film such as interfacial adhesion, high temperature durability reliability, light leakage prevention property, and reworkability can be formed.

In one example, the block polymer of the present application may include 5 parts by weight to 50 parts by weight of the first block and 50 parts by weight to 95 parts by weight of the second block.

In another example, the block copolymer may contain a relatively excessive amount of the second block. Specifically, the block copolymer comprises 55 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 85 parts by weight of the second block among the total block copolymers. It can include more than one. In this case, the upper limit of the content of the second block in the total block copolymer may be, for example, 95 parts by weight or less, 94 parts by weight or less, 93 parts by weight or less, 92 middle parts or less, 91 parts by weight or less, or 90 parts by weight or less. have. Further, in this case, the content of the first block is, for example, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight of the total block copolymer. It may be less than or equal to 15 parts by weight, and its lower limit may be, for example, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, or 9 parts by weight or more.

A method of preparing the block copolymer is not particularly limited, and a known method may be used. For example, the block polymer may be polymerized in a LRP (Living Radical Polymerization) method. Specifically, an anionic polymerization method in which an organic rare earth metal complex is used as a polymerization initiator or an organic alkali metal compound is used as a polymerization initiator in the presence of an inorganic acid salt such as an alkali metal or alkaline earth metal salt, or an organic alkali metal compound is polymerized. Anionic polymerization method that is used as an initiator and synthesized in the presence of an organic aluminum compound, atomic transfer radical polymerization method (ATRP) using an atom transfer radical polymerization agent as a polymerization control agent, and an atom transfer radical polymerization agent as a polymerization control agent. ARGET (Activators Regenerated by Electron Transfer) atom transfer radical polymerization (ATRP), ICAR (Initiators for continuous activator regeneration) atom transfer radical polymerization (ATRP), reversible addition of inorganic reducing agents- Polymerization by reversible addition-cleavage chain transfer using a cleavage chain transfer agent (RAFT), or a method using an organic tellurium compound as an initiator may be used, and an appropriate method is selected from the above methods to prepare the block copolymer. I can.

In one example, the first adhesive layer may further include a crosslinking agent. That is, the first adhesive layer may be formed by curing a composition comprising a block copolymer (A) and a crosslinking agent. In this case, the term "curing" may mean a process in which at least two components included in the pressure-sensitive adhesive composition chemically react with each other by irradiation and/or heating of electromagnetic waves. In the range of the term ``electromagnetic wave'' in the above, microwaves, infrared (IR), ultraviolet (UV), X-rays and gamma rays, as well as alpha-particle beams, proton beams, Particle beams such as a neutron beam and an electron beam may be included.

In one example, the crosslinking agent may be a compound having at least two or more functional groups capable of reacting with a crosslinkable group included in the block copolymer, that is, a multifunctional crosslinking agent. As the crosslinking agent, as a crosslinking agent capable of undergoing a crosslinking reaction by application of heat, an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, or a metal chelate crosslinking agent may be exemplified.

In one example, when the crosslinkable functional group introduced into the block copolymer is a hydroxy group, an isocyanate-based crosslinking agent may be used as the crosslinking agent. Examples of the isocyanate crosslinking agent include diisocyanate compounds such as tolyene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoborone diisocyanate, tetramethylxylene diisocyanate or naphthalene diisocyanate, Alternatively, a compound obtained by reacting the diisocyanate compound with a polyol may be used, and as the polyol, for example, trimethylol propane may be used.

In one example, the multifunctional crosslinking agent may be included in the composition in an amount of 0.001 parts by weight or more, based on 100 parts by weight of the block copolymer. Specifically, the content of the multifunctional crosslinking agent may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and more specifically, the content of the crosslinking agent is 0.10 or more, 0.15 or more, 0.20 or more, It may be 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, or 0.50 or more. The upper limit of the content of the multifunctional crosslinking agent is not particularly limited, but may be, for example, 10 parts by weight or less or 5 parts by weight or less, and specifically, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight It may be less than or equal to part. In this range, the gel fraction, cohesion, adhesion, and durability of the pressure-sensitive adhesive can be excellently maintained.

In one example, the first adhesive layer may further include a silane coupling agent. That is, the first adhesive layer may be formed by curing a composition including a block copolymer (A), a crosslinking agent, and a silane coupling agent. The specific kind of the silane coupling agent is not limited. For example, a silane coupling agent containing any one of an epoxy group, a thiol group, an amino group, a vinyl group, an epoxy group, a beta-cyanoacetyl group, an acetoacetyl group or a halogen may be used.

In one example, the silane coupling agent may be a compound having a beta-cyano group or one or more selected from compounds having an acetoacetyl group. Specifically, the silane coupling agent may be at least one selected from a compound having a beta-cyano group represented by the following formula (A) and a compound having an acetoacetyl group represented by the following formula (B).

[Formula A]

(R ₁ ) _n Si(R ₂ ) _(4-n)

[Formula B]

(R ₃ ) _n Si(R ₂ ) _(4-n)

In Formula A or B, R1 is a beta-cyanoacetyl group or a beta-cyanoacetylalkyl group, R3 is an acetoacetyl group or an acetoacetylalkyl group, R2 is an alkoxy group, and n is a number of 1 to 3.

In Formula A or B, 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 such an alkyl group may be linear, branched or cyclic. I can. In addition, in 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 such an alkoxy group may be a linear, branched or ring It can be a prize.

Examples of the compound represented by Formula A or B include acetoacetylpropyl trimethoxysilane, acetoacetylpropyl triethoxy silane, beta cyanoacetylpropyl trimethoxysilane or beta cyanoacetylpropyl triethoxy silane. However, it is not particularly limited thereto.

In one example, the first adhesive layer may contain the silane coupling agent in a range of 0.01 to 5 parts by weight, based on 100 parts by weight of the block copolymer. Specifically, the lower limit of the content of the silane coupling agent is, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, 0.05 parts by weight or more, more specifically, 0.1 parts by weight or more, 0.15 parts by weight or more, It may be 0.2 parts by weight or more, 0.25 parts by weight or more, 0.3 parts by weight or more, 0.35 parts by weight or more, 0.4 parts by weight or more, 0.45 parts by weight or more, or 0.5 parts by weight or more. In addition, the upper limit of the content of the silane coupling agent may be, for example, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less.

The second adhesive layer positioned on the first adhesive layer includes a random copolymer (B). The random copolymer has a carboxyl group. As a result of experimental confirmation, when the adhesive layer containing an acidic functional group such as a carboxyl group is positioned closer to the polarizer, that is, when used for the first adhesive layer, the interfacial adhesion between the optical film or the adhesive is poor. Since hydrogen bonding may occur by the second adhesive having a carboxyl group, the modulus and cohesive strength of the adhesive can be increased. In addition, the interaction with the functional groups of the heterogeneous substrate adjacent to the second adhesive layer (eg, Si-OH in the case of glass) may increase, so that adhesion to the heterogeneous substrate may be increased.

The kind of monomers capable of providing a carboxyl group to the random copolymer is not particularly limited. For example, a carboxyl group-containing (meth)acrylic acid ester monomer may be used.

In one example, the random copolymer is a carboxyl group-containing monomer, (meth)acrylic acid, 2-(meth)acryloyloxyacetic acid, 3-(meth)acryloyloxypropyl acid, and 4-(meth)acrylo A carboxyl group-containing (meth)acrylate such as monooxybutyric acid, (meth)acrylic acid duplex or the like can provide a carboxyl group to the random copolymer.

In one example, the random copolymer may include a polymerization unit derived from a carboxyl group-containing monomer in the range of 0.5 to 10 parts by weight. Specifically, the polymerization unit derived from a carboxyl group-containing monomer in the random copolymer is, for example, 1 part by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, 2.5 parts by weight or more, 3.0 parts by weight or more, 3.5 parts by weight or more , 4.0 parts by weight or more, 4.5 parts by weight or more, 5.0 parts by weight or more, or 5.5 parts by weight or more. When the content range is satisfied, the cohesive strength of the adhesive is improved by imparting appropriate hydrogen bonds to the copolymer, and at the same time, the adhesive strength can be increased by inducing an interaction with an adjacent base material (eg, glass). . In addition, when it exceeds the above range, a yellowing problem may occur due to an increase in the content of the acidic functional group, a carboxyl group.

In one example, the random copolymer may include a polymerization unit derived from a (meth)acrylic acid ester in addition to a polymerization unit derived from a carboxyl group-containing monomer. For example, the random copolymer may include a carboxyl group-containing monomer and an alkyl (meth)acrylate. The alkyl (meth)acrylate used when forming the random copolymer may be selected in consideration of cohesion, glass transition temperature, and adhesion control.

In one example, the alkyl (meth)acrylate used when forming the random copolymer is an alkyl having 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. (Meth)acrylate can be used. Examples of such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate )Acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate, iso Bornyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and the like, and one or more of the above may be used.

In one example, the alkyl (meth)acrylate used in forming the random copolymer may be an alkyl acrylate having 1 to 20 carbon atoms. The specific types of compounds are the same as those described in connection with the second block.

In one example, the random copolymer may include 0.5 to 10 parts by weight of a polymerization unit derived from a carboxyl group-containing monomer and 99.5 to 90 parts by weight of a polymerization unit derived from an alkyl (meth)acrylate.

In one example, the random copolymer included in the second adhesive layer may be a crosslinkable polymer. Specifically, the random copolymer may include a polymerization unit derived from a carboxyl group-containing monomer, an alkyl (meth)acrylate, and a copolymerizable monomer having a crosslinkable functional group.

In one example, the random copolymer is derived from 0.5 to 10 parts by weight of a carboxyl group-containing (meth)acrylate, 70 to 99 parts by weight of an alkyl (meth)acrylate, and 0.1 to 10 parts by weight of a copolymerizable monomer having a crosslinkable functional group It may contain a polymerization unit of.

In one example, the monomer providing the crosslinkable functional group used in the second block of the block copolymer of the first adhesive layer and the monomer providing the crosslinkable functional group used in the random copolymer of the second adhesive layer are the same can do. When it has a similar composition with respect to the crosslinkable functional group, it is possible to improve adhesion or durability.

In one example, the second adhesive layer may further include a crosslinking agent. That is, the composition for forming the second adhesive layer may further include a crosslinking agent. The configuration related to the crosslinking agent is the same as described for the above-described first adhesive layer.

In one example, the crosslinkable functional group in the second adhesive layer may be a hydroxy group, and the crosslinking agent may be an isocyanate compound.

In one example, the composition for forming the second adhesive layer may not include a catalyst. For example, in the case of a pressure-sensitive adhesive system including an isocyanate crosslinking agent and a hydroxy group as a crosslinkable functional group, a catalyst such as DBTDL (Dibutyl Tin Dilaurate) is generally used. However, when a carboxyl group is used together in an adhesive system in which an isocyanate crosslinking agent is chemically bonded to a hydroxy group contained in the adhesive polymer to form a crosslinked structure, the effect of catalyst addition is not exhibited even if the adhesive composition contains a catalyst. Therefore, when curing the pressure-sensitive adhesive resin containing a carboxyl group, instead of using a catalyst, it may be considered to increase the content of the crosslinking agent or the curing agent. For example, a crosslinking agent having a higher content than the content of the crosslinking agent actually used in the first adhesive layer may be used, and through this, a crosslinking or curing density capable of functioning as an adhesive layer may be secured. Specifically, the second adhesive layer may include at least 1 part by weight of a crosslinking agent based on 100 parts by weight of the random copolymer. More specifically, the lower limit of the content of the crosslinking agent may be 1.5 parts by weight or 2.0 parts by weight or more.

In one example, the second adhesive layer may further include a silane coupling agent. The configuration related to the silane coupling agent is the same as described for the above-described first adhesive layer.

In the present application, the thickness of the first adhesive layer and the second adhesive layer may be adjusted to a predetermined size or ratio.

Specifically, in one example, the thickness of the first adhesive layer may be 5 μm or more. When the thickness of the first adhesive layer is less than the above, the amount of aromatic groups that mitigate light leakage by aligning according to a change in the size of the polarizing plate under conditions such as high temperature may not be effective. Although not particularly limited, the thickness of the first adhesive layer is 25 µm or less, 24 µm or less, 23 µm or less, 22 µm or less, 21 µm or less, 20 µm or less, 19 µm or less, 18 µm or less, 17 µm or less, It may be 16 µm or less, 15 µm or less, 14 µm or less, 13 µm or less, 12 µm or less, 11 µm or less, or 10 µm or less.

In one example, the thickness of the second adhesive layer may be 20 μm or less. Specifically, the thickness of the second adhesive layer may be 19.5 µm or less, 19.0 µm or less, 18.5 µm or less, 17.5 µm or less, 17.0 µm or less, 16.5 µm or less, 16.0 µm or less, 15.5 µm or less, or 15 µm or less. When the thickness of the adhesive layer including a carboxyl group, which is an acidic functional group, exceeds the above range, yellowing of the adhesive layer may be severe. The lower limit of the thickness is not particularly limited, but may be, for example, 5 µm or more, 6 µm or more, 7 µm or more, 8 µm or more, 9 µm or more, or 10 µm or more.

In one example, the total thickness of the adhesive layer obtained by combining the thicknesses of the first adhesive layer and the second adhesive layer may be 30 μm or less. More specifically, the upper limit of the total thickness may be, for example, 25 µm or less, 24 µm or less, 23 µm or less, 22 µm or less, 21 µm or less, or 20 µm or less.

In another example, a ratio (a/b) between the thickness (a) of the first adhesive layer and the thickness (b) of the second adhesive layer may be 0.3 or more. When a/b, which is a ratio of thickness, is less than 0.3, durability conditions (e.g., high temperature conditions such as about 95°C, or high temperature/high humidity conditions such as 65°C and 95% relative humidity, due to carboxyl groups present in the second adhesive layer) ), yellowing of the adhesive may occur.

In one example, each of the adhesive layers may further include a tackifier, if necessary. As the tackifier, for example, a hydrocarbon resin or a hydrogenated product thereof, a rosin resin or a hydrogenated product thereof, a rosin ester resin or a hydrogenated product thereof, a terpene resin or a hydrogenated product thereof, a terpene phenol resin or a hydrogenated product thereof, a polymerized rosin resin or One kind or two or more kinds of polymerized rosin ester resins, etc. may be used in combination, but is not limited thereto. The tackifier may be used in a composition for forming each adhesive layer in an amount of 100 parts by weight or less based on 100 parts by weight of the block copolymer.

The method of forming each adhesive layer of the above-described configuration on the optical film is not particularly limited. For example, a first adhesive layer prepared on a separator (release film) is coated on an optical film, and then a second adhesive layer prepared on a separate separator is sequentially placed on the first adhesive layer of the optical film. You can use the method of laminating.

The specific method of forming each adhesive layer is also not particularly limited. For example, a method of implementing a crosslinked structure by directly coating and curing an adhesive composition on a substrate such as a polarizing plate, or coating and curing the adhesive composition on the release-treated surface of a release film to form a crosslinked structure Afterwards, a method of transferring it can be used. When coating the adhesive composition, for example, a conventional means such as a bar coater can be used.

It is preferable from the viewpoint of performing a uniform coating process that the crosslinking agent included in the pressure-sensitive adhesive composition is controlled so that the crosslinking reaction of the functional group does not proceed. Through this, the crosslinking agent forms a crosslinked structure in the curing and aging process after the coating operation, thereby improving the cohesiveness of the pressure-sensitive adhesive, and improving adhesive properties and cuttability.

In addition, the coating process is preferably carried out after sufficiently removing bubbles-causing components such as volatile components or reaction residues in the pressure-sensitive adhesive composition, and accordingly, the crosslinking density or molecular weight of the pressure-sensitive adhesive is too low, so that the elastic modulus decreases, and in a high temperature state Bubbles existing between the glass plate and the adhesive layer become large, thereby preventing a problem of forming a scattering body inside.

After coating, a method of implementing a crosslinked structure by curing the adhesive composition is also not particularly limited. For example, the coating layer may be maintained at an appropriate temperature so that a crosslinking reaction between the block copolymer included in the coating layer and the crosslinking agent may be induced.

After coating, a method of implementing a crosslinked structure by curing the coated pressure-sensitive adhesive composition is also not particularly limited. For example, a method of maintaining the coating layer at an appropriate temperature so that a crosslinking reaction between the block copolymer included in the coating layer and the crosslinking agent may be induced may be used.

According to the present application having the above configuration, an aromatic group is concentrated on one side of the adhesive layer to effectively compensate for birefringence caused by a change in the size of a polarizing plate at a high temperature, and to have an excellent effect in suppressing light leakage. In addition, it has excellent high-temperature, high-temperature, and high-humidity durability reliability, and particularly, it is possible to minimize lifting on a glass substrate.

In another example relating to the present application, the present application also relates to a display device. When the display device is an LCD, the device 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 pressure-sensitive adhesive described above.

The liquid crystal panel may include, for example, a first substrate sequentially formed, a pixel electrode, a first alignment layer, a liquid crystal layer, a second alignment layer, a common electrode, and a second substrate. In one example, the first substrate and the second substrate may be a glass substrate. In this case, the polarizing plate or the optical laminate may be attached to the glass substrate via the pressure-sensitive adhesive layer described above.

The device may further include a light source on a side opposite to the viewing side of the liquid crystal panel. On the first substrate on the light source side, for example, an active driving circuit including a TFT (Thin Film Transistor) and wiring as a driving element electrically connected to a transparent pixel electrode may be formed. The pixel electrode may include, for example, Indium Tin Oxide (ITO), and may function as an electrode for each pixel. In addition, the first or second alignment layer may include, for example, a material such as polyimide, but is not limited thereto.

Examples of the liquid crystal panel in the apparatus include a passive matrix type panel such as a twisted nematic (TN) type, a super twisted nematic (STN) type, a ferroelectic (F) type, or a polymer dispersed (PD) type; An active matrix type panel such as a two terminal type or a three terminal type; Known panels, such as an IPS (In Plane Switching) panel and a vertical alignment (VA) panel, may all be applied.

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

According to an example of the present application, an aromatic group is placed on one side in the thickness direction without causing a decrease in the durability reliability of the adhesive layer that may occur under high temperature or high temperature/humidity conditions, and thus excellent optics even when a small amount of optical compensation monomer is used. It has a compensating ability and can effectively suppress a light leakage phenomenon due to a change in dimensions of the polarizing plate.

Hereinafter, the present application will be described in detail through examples. However, the scope of protection of the present application is not limited by the examples described below.

<Measurement or evaluation items>

1. Molecular weight

The number average molecular weight (Mn) and molecular weight distribution (PDI) of each block or block copolymer were measured using GPC (Gel Permeation Chromatograph), and the GPC measurement conditions are as follows. The measurement results were converted using standard polystyrene (Aglient system (manufactured)) to prepare the calibration curve.

<GPC measurement conditions>

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

Column: Connect 2 PL Mixed B

Column temperature: 40°C

Eluent: THF (Tetrahydrofuran)

Flow rate: 1.0 mL/min

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

2. Glass transition temperature

The glass transition temperature (T _g ) of each block of the block copolymer or block copolymer was calculated according to Equation A below.

[Equation A]

1/Tg=∑Wn/Tn

In the above formula, Wn is the weight fraction of the block copolymer or the monomer applied to each block of the copolymer, and Tn represents the glass transition temperature when each monomer forms a homopolymer. That is, in Equation A, the right side is the result of summing the calculated values after calculating all of the values (Wn/Tn) by dividing the weight fraction of the monomer used by the glass transition degree indicated when the monomer forms a homopolymer. to be.

3. Light transmission Uniformity( Light leak ) evaluation

A polarizing plate having adhesive compositions used in Examples and Comparative Examples attached to one side was cut to have a width of about 200 mm and a length of about 200 mm, and on both sides of a soda lime glass having a width of 250 mm and a length of 250 mm. It was attached by crossing at 90°. Thereafter, the glass substrate to which the polarizing plate is attached is stored in an autoclave (50° C., 5 atmospheres) for about 20 minutes to prepare a sample. The prepared sample was stored in an oven at 80° C. for 72 hours and then mounted on a back light unit at room temperature, and the uniformity of light transmittance was observed and evaluated based on the following criteria.

<Light transmission uniformity evaluation criteria>

A: It is difficult to judge the non-uniformity of light transmittance with the naked eye.

B: There is a slight non-uniformity of light transmission

C: There is some non-uniformity of light transmission

D: There is a large amount of non-uniformity in light transmission

4. Durability evaluation

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, and attached to a commercial liquid crystal panel of 19 inches. Then, the liquid crystal panel to which the polarizing plate is attached is stored in an autoclave (50° C. 5 atm) for about 20 minutes to prepare a sample. Moisture and heat resistance was evaluated according to the following criteria after leaving the sample prepared at 65° C. and 95% relative humidity for 500 hours. In addition, heat resistance and durability were evaluated according to the following criteria after maintaining the prepared samples at 95° C. and 105° C. for 500 hours, respectively.

<Evaluation criteria for heat and moist heat resistance>

A: No bubbles and peeling occurred

B: Some bubbles and/or peeling occurred

C: A large amount of bubbles and/or peeling occurs

5. Polarizing plate-adhesive interface adhesion evaluation

The polarizing plate having the adhesive composition prepared in Examples and Comparative Examples attached to one side was cut to have a width of about 50 mm and a length of about 100 mm, and an adhesive tape on the adhesive surface 3 days after coating (American tape Co., Ltd.) was laminated and the adhesive tape was removed, while observing the interface peeling phenomenon between the polarizing plate and the pressure-sensitive adhesive, and evaluated based on the following criteria.

<Interface adhesion evaluation criteria>

A: 90% or more of the adhesive composition remains on the polarizing plate

B: The pressure-sensitive adhesive composition remains 50% or more to less than 90% on the polarizing plate

C: less than 50% of the pressure-sensitive adhesive composition remains on the polarizing plate

6. Discoloration evaluation of adhesive composition

The prepared coating solution for the first adhesive layer was coated on the release-treated surface of a release-treated 38 μm-thick release PET (poly(ethylene terephthalate)) (MRF-38, manufactured by Mitsubishi), and kept in an oven at 95° C. for about 3 minutes. After preparing the adhesive composition, the first adhesive layer and the second adhesive layer were laminated. Thereafter, the laminated adhesive film was cut to have a width of 40 mm and a length of 40 mm to prepare a specimen. Then, attach it to a jig having a width of 40 mm and a length of 40 mm, and use a UV-Vis Spectrophotometer (manufactured by JASCO, model name V-7100) to position the adhesive surface toward the light source and measure the single b value. Do (b1). After that, the optical characteristic single b value of the sample kept for 250 hours in an oven at 95°C was measured (b2), and the color change of the adhesive composition before and after the durable conditions was observed, and the color change rate of the adhesive ((b2-b1)/b1) Evaluate. At this time, the single b value is a value displayed by the spectrophotometer machine itself, and is an index showing the color value compared from the color difference meter. The larger the single b value is, the stronger the yellow color becomes, and the larger the negative value, the more the blue color becomes. A pressure-sensitive adhesive having an acidic functional group can turn yellow when subjected to durability conditions, and a single b value is used as an index of such yellowing.

<Adhesive color change evaluation criteria>

O (less color change): (b2-b1) / b1 ≤ 0.25

X (large color change): (b2-b1) / b1> 0.25

<of the copolymer Manufacturing example >

Manufacturing example 1. Preparation of block copolymer (A1)

EBiB (ethyl 2-bromoisobutyrate) 0.032 g and methyl methacrylate (MMA) 9.0 g, butyl methacrylate (BMA) 2.6 g and 2-phenoxyethyl methacrylate (PEMA) 2.9 g ethyl acetate (EAc) 9.8 mixed in g. The reactor containing the mixture was sealed, purged and stirred with nitrogen at about 25° C. for about 30 minutes, and dissolved oxygen was removed through bubbling. Thereafter, 0.002 g of CuBr2, 0.006 g of TPMA (tris(2-pyridylmethyl)amine) and 0.003 g of V-65 (2,2'-azobis(2,4-dimethyl valeronitrile)) were added to the mixture from which oxygen was removed. Then, the reaction was initiated in a reaction tank at about 67°C (polymerization of the first block). When the conversion rate of methyl methacrylate is about 70%, a mixture of 121.0 g of butyl acrylate (BA), 1.5 g of hydroxybutyl acrylate (HBA) and 250 g of ethyl acetate (EAc), previously bubbled with nitrogen It was charged in the presence of nitrogen. Thereafter, 0.004 g of CuBr2, 0.01 g of TPMA and 0.01 g of V-65 were added to the reactor, and a chain extension reaction was performed (polymerization of the second block). When the conversion ratio of the monomer (BA) reached 80% or more, the reaction mixture was exposed to oxygen and diluted in an appropriate solvent to terminate the reaction to prepare a block copolymer (V-65 in the above process is It was appropriately divided and added until the reaction was completed).

Manufacturing example 2. Preparation of block copolymers (A2 to A3)

A block copolymer was prepared in the same manner as in Preparation Example 1, except that the raw materials used in the polymerization of the first block and the second block were adjusted in the ratio shown in Table 1 below.

[Table 1]

Manufacturing example 3. Preparation of random copolymer (B1)

94 parts by weight of 2-ethylhexylacrylate (EHA) and 1 part by weight of hydroxybutyl acrylate (HBA) in a reactor equipped with a cooling device so that nitrogen gas is refluxed and temperature control is easy , A mixture of monomers consisting of 5 parts by weight of acrylic acid (AA) was added. Then, 200 parts by weight of ethylacetate (EAc) was added as a solvent. After purging nitrogen gas for 60 minutes to remove oxygen, the temperature was maintained at 60°C, and 0.05 parts by weight of azobisisobutyronitrile (AIBN) as a reaction initiator was added and reacted for 8 hours at random. Copolymer (B1) was prepared. The weight average molecular weight of copolymer (B1) was 280,000 and molecular weight distribution was 3.5.

Manufacturing example 4. Preparation of random copolymer (B2)

Consists of 99 parts by weight of n-butylacrylate (BA) and 1 part by weight of hydroxybutyl acrylate (HBA) in a reactor equipped with a cooling device to facilitate nitrogen gas reflux and temperature control. A mixture of monomers was added. Then, 200 parts by weight of ethylacetate (EAc) was added as a solvent. After purging nitrogen gas for 60 minutes to remove oxygen, the temperature was maintained at 60°C, and 0.05 parts by weight of azobisisobutyronitrile (AIBN) as a reaction initiator was added and reacted for 8 hours at random. Copolymer (B2) was prepared. At this time, the weight average molecular weight was 1.13 million and molecular weight distribution was 5.7.

< Example And Comparative example >

Example One

(One) First Adhesive layer Coating liquid ( First Adhesive layer Composition)

With respect to 100 parts by weight of the block copolymer (A1) prepared in Preparation Example 1, 0.20 parts by weight of a crosslinking agent (Coronate L, manufactured by NPU in Japan), 0.01 parts by weight of DBTDL (Dibutyltin dilaurate), 0.15 parts by weight of a silane coupling agent (M812, manufactured by LG Chemical) Part by weight was mixed, and ethyl acetate was added as a solvent to adjust the coating solid content to about 30% by weight to prepare a coating solution for a first adhesive layer (adhesive composition).

(2) Second Adhesive layer Coating liquid ( Second Adhesive layer Composition)

With respect to 100 parts by weight of the random copolymer (B1) prepared in Preparation Example 3, 1.9 parts by weight of a crosslinking agent (Coronate L, manufactured by NPU in Japan) and 0.06 parts by weight of a silane coupling agent (M812, manufactured by LG Chem) were mixed, and ethyl acetate as a solvent By blending and adjusting the coating solid content to be about 15% by weight, a coating solution for a second adhesive layer (adhesive composition) was prepared.

(3) Preparation of adhesive polarizing plate

The prepared coating solution for the first adhesive layer was coated on the release-treated surface of a 38 μm-thick release-treated PET (poly(ethylene terephthalate)) (MRF-38, manufactured by Mitsubishi) so that the thickness after drying was about 8 μm, It was held in an oven at 95° C. for about 3 minutes. After drying, a coating layer formed on the release PET was laminated on one side of a polarizing plate (stack structure of COP/PVA/COP: COP=cyclopolyolefin, PVA=polyvinyl alcohol-based polarizing film) to prepare an adhesive polarizing plate.

Similarly, the prepared coating solution for the second adhesive layer was coated on the release-treated surface of a 38 μm-thick release-treated PET (poly(ethylene terephthalate)) (MRF-38, manufactured by Mitsubishi) so that the thickness after drying was about 14 μm, It was held in an oven at 95° C. for about 3 minutes. The adhesive film obtained after drying was laminated with the first adhesive layer surface of the adhesive polarizing plate coated with the first adhesive layer on one surface prepared above to prepare an adhesive polarizing plate having a laminated adhesive surface.

Example 2 to 3 and Comparative example 1 to 5

When preparing the pressure-sensitive adhesive composition (coating solution), a pressure-sensitive adhesive composition (coating solution) and a pressure-sensitive adhesive polarizing plate were prepared in the same manner as in Example 1, except that each component and ratio were adjusted as shown in Table 2 below.

[Table 2]

[Table 3]

According to the article of the present application, a block copolymer composition having an aromatic group for optical compensation in the first block is used as a material of the first adhesive layer having a predetermined thickness, and a random copolymer that is an acidic functional group is used as a second adhesive layer having a predetermined thickness. It can be seen that the example used as the material has excellent light leakage reduction effect and excellent heat/moisture heat resistance.

On the other hand, in the case of Comparative Example 2 using a block copolymer having no aromatic group, while the durability was satisfied, it showed inferiority in light leakage. It is thought that when an aromatic group is added in the block polymer, the alignment of the aromatic group proceeds smoothly under heat-resistant conditions, resulting in the ability to suppress light leakage. It can be understood in the same context that Comparative Example 4, in which the stacking positions of the first adhesive layer and the second adhesive layer used in Example 1 were changed from each other, also had poor light leakage suppression ability. That is, since the first adhesive layer contributing to the light leakage suppression ability does not directly receive the shrinkage stress of the polarizing plate, the aromatic groups are not sufficiently aligned, and thus the light leakage suppression effect is insufficient.

In the case of Comparative Example 1 in which the first adhesive layer had a thin thickness of 3 µm, the effect of suppressing light leakage was inferior and showed an inferiority in the b value change after the moist heat resistance of the adhesive.

In addition, in Comparative Example 3, in which a random copolymer without introducing a carboxyl group, which is an acidic functional group, was used, it was confirmed that excitation occurred from the glass substrate under severe conditions (high temperature and/or high humidity), resulting in abnormality in durability.

Claims (21)

Optical film; A first adhesive layer comprising a block copolymer (A) having an aromatic group; And a second adhesive layer comprising a random copolymer (B) having a polymerization unit derived from a carboxyl group-containing (meth) acrylic acid ester in sequence,
A pressure-sensitive adhesive optical laminate having a thickness of the first adhesive layer of 5 μm or more. The method of claim 1, wherein the block copolymer (A) has a glass transition temperature of 50° C. or higher and includes a first block having an aromatic group; And a second block having a glass transition temperature of -10° C. or less and having a crosslinkable functional group. The adhesive-type optical laminate according to claim 2, wherein the first block and the second block contain a polymerized unit derived from a (meth)acrylic acid ester. The adhesive-type optical laminate according to claim 2, wherein the first block comprises a polymerization unit derived from an alkyl methacrylate and a polymerization unit derived from an aromatic group-containing alkyl methacrylate. The adhesive optical laminate according to claim 2, wherein the first block contains 50 parts by weight or less of a polymerization unit derived from an aromatic group-containing alkyl methacrylate. The adhesive optical laminate of claim 2, wherein the first block has a number average molecular weight in the range of 2,500 to 150,000. The adhesive optical laminate according to claim 6, wherein the number average molecular weight of the block copolymer (A) is in the range of 50,000 to 300,000. The adhesive-type optical layered product according to claim 7, wherein the block copolymer (A) has a molecular weight distribution [weight average molecular weight (Mw)/number average molecular weight (Mn)] in the range of 1.5 to 3.5. The adhesive-type optical laminate according to claim 2, wherein the second block comprises 60 to 99.9 parts by weight of a polymerization unit derived from an alkyl acrylate and 0.1 to 40 parts by weight of a copolymerizable monomer containing a crosslinkable functional group. The adhesive-type optical laminate according to claim 2, wherein the block copolymer (A) is a diblock copolymer having a first block and a second block. The adhesive-type optical laminate of claim 2, wherein the block copolymer (A) comprises 5 to 50 parts by weight of the first block and 50 to 95 parts by weight of the second block. The adhesive-type optical laminate of claim 1, wherein the first adhesive layer further comprises a crosslinking agent in a range of 0.01 to 10 parts by weight based on 100 parts by weight of the block copolymer (A). The adhesive optical laminate of claim 1, wherein the first adhesive layer further comprises a silane coupling agent. The adhesive-type optical laminate according to claim 1, wherein the random copolymer (B) contains a polymerization unit derived from a carboxyl group-containing monomer in a range of 0.5 to 10 parts by weight. The adhesive-type optical laminate according to claim 1, wherein the random copolymer (B) contains a polymerization unit derived from a carboxyl group-containing monomer, an alkyl (meth)acrylate, and a copolymerizable monomer having a crosslinkable functional group. The adhesive optical laminate of claim 1, wherein the second adhesive layer further comprises a crosslinking agent in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the random copolymer (B). The adhesive optical laminate of claim 1, wherein the second adhesive layer further comprises a silane coupling agent. The adhesive optical laminate according to claim 1, wherein the second adhesive layer has a thickness of 20 μm or less. The adhesive-type optical laminate according to claim 18, wherein a ratio (a/b) between the thickness (a) of the first adhesive layer and the thickness (b) of the second adhesive layer is 0.3 or more. The adhesive type optical laminate according to claim 1, wherein the optical film is a polarizer. Liquid crystal panel; And comprising the optical laminate according to claim 1,
A display device to which an affection panel and an optical laminate are attached through the second adhesive layer.