KR100952285B1 - Optical film containing (meth) acrylic resin and manufacturing method thereof - Google Patents

Abstract

The present invention provides an optical film including a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures, a manufacturing method thereof, and a polarizing plate and a liquid crystal display device including the optical film.

Optical film, glass transition temperature, (meth) acrylic resin

Description

Optical film containing (meth) acrylic resin and its manufacturing method {OPTICAL FILMS COMPRISING (METH) ACRYLIC RESINS AND METHOD FOR PREPARING THE SAME}

1 is a view schematically showing a structure of a liquid crystal display device in which an optical film according to the present invention is applied as a protective film of a polarizing plate.

The present invention relates to an optical film, a manufacturing method thereof, and a polarizing plate and a liquid crystal display device including the optical film. Specifically, the present invention relates to an optical film including a (meth) acrylic resin, a method of manufacturing the same, and a polarizing plate and a liquid crystal display device including the optical film having improved mechanical and optical properties.

Acrylic resins are inexpensive and have high transparency and are suitable as resins for films. However, acrylate films containing acrylic resins have inferior mechanical properties, which are insufficient to produce films. In order to improve this, a technique of preparing an acrylate film using a material polymerized by adding a soft segment to an acrylic resin has been attempted, but there is still a demand for development of a film satisfactory in mechanical properties.

The present inventors have conducted research to solve the problems of the prior art, and as a result, a certain kind of (meth) acrylic copolymer has excellent mechanical properties and excellent optical properties when fabricated into a film, and thus is applied as a material of an optical film. It turned out that it can show a good effect. Accordingly, an object of the present invention is to provide an optical film including a (meth) acrylic resin having excellent mechanical properties, a manufacturing method thereof, and a polarizing plate and a liquid crystal display device including the optical film.

In order to achieve the above object, the present invention provides an optical film comprising a graft copolymer comprising two or more (meth) acrylic resins having different glass transition temperatures.

In addition, the present invention a) preparing a first (meth) acrylic resin comprising a first (meth) acrylic monomer, b) a functional group capable of reacting with radicals in the main chain of the first (meth) acrylic resin Introducing, c) radically polymerizing a second (meth) acrylic monomer to the modified first (meth) acrylic resin obtained in step b), and converting the first (meth) acrylic resin to a first (meth) acrylic resin. And a graft copolymer obtained by graft polymerization of a second (meth) acrylic resin having a different glass transition temperature, and d) forming a film using the graft copolymer obtained in step c). It provides a method for producing an optical film.

In addition, the present invention is a liquid crystal display device comprising a liquid crystal cell, and a first polarizing plate and a second polarizing plate provided on both sides of the liquid crystal cell, glass between at least one of the first polarizing plate and the second polarizing plate and the liquid crystal cell Provided is a liquid crystal display device comprising at least one optical film comprising a graft copolymer comprising two or more kinds of (meth) acrylic resins having different transition temperatures.

In addition, the present invention is a polarizing plate comprising a polarizer and an optical film comprising a graft copolymer comprising two or more (meth) acrylic resins having different glass transition temperatures, provided as a protective film on one side or both sides of the polarizer. To provide.

In addition, the present invention is a liquid crystal display device comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate provided on both sides of the liquid crystal cell, wherein at least one of the first polarizing plate and the second polarizing plate of the polarizer and the polarizer Provided is a polarizing plate comprising an optical film including a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures provided as protective films on one or both surfaces thereof.

Hereinafter, the present invention will be described in detail.

The optical film according to the present invention is characterized in that it comprises a graft copolymer comprising two or more (meth) acrylic resins having different glass transition temperatures. The optical film according to the present invention including the graft copolymer as described above has much better mechanical properties and optical properties than conventional acrylic films, and thus may be usefully used in various applications. In this specification, (meth) acrylic-type resin is interpreted as including both acrylic resin and methacryl-type resin.

In the present invention, it is preferable that two or more kinds of (meth) acrylic resins having different glass transition temperatures are not compatible with each other. It is preferable that at least 1 type of the said (meth) acrylic-type resin has a glass transition temperature less than 0 degreeC, and at least 1 type of the said (meth) acrylic-type resin has a glass transition temperature of 0 degreeC or more. The polymer chain constituting the main chain in the graft copolymer is preferably a (meth) acrylic resin having a glass transition temperature of less than 0 ° C.

The (meth) acrylic resin is not particularly limited, but may be prepared by polymerizing a (meth) acrylic monomer, and an additional comonomer may be further added if necessary.

As said (meth) acrylic-type monomer, it is good to have a C1-C12 alkyl group, Preferably it has a C2-C8 alkyl group, an alkylene group, and an aromatic substituent. Examples of the (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms include butyl acrylate, butyl methacrylate and 2-ethylhexyl acrylate. 2-ethylhexyl methacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, t- T-butyl acrylate, t-butyl methacrylate, pentyl acrylate, pentyl methacrylate, n-octyl acrylate ), n- N-octyl methacrylate, isononyl acrylate, isononyl methacrylate, iso-nonyl methacrylate, n-tetradecyl acrylate, n-tetradecyl methacrylate, la A monomer selected from the group consisting of uryl acrylate, lauryl methacrylate, benzyl acrylate, benzyl methacrylate and the like can be used, and these can be used alone or in mixture of two or more thereof. However, the present invention is not limited to these.

A (meth) acrylic acid ester monomer having a functional group may be added to prepare the (meth) acrylic resin, and specific examples thereof include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Hydroxy, such as 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate (Meth) acrylic acid ester monomer comprising a; (Meth) acrylic acid ester monomers containing an epoxy such as 2-glycidyl (meth) acrylate; (Meth) acrylic acid ester monomers including carboxylic acids such as acrylic acid, methacrylic acid, acrylic acid dimer, itaconic acid, maleic acid, maleic anhydride, crotonic acid, β-carboxyethyl acrylate, etc. may be used, and these are 1 The species may be used alone or in a mixture of two or more thereof. However, the present invention is not limited only to these examples.

The (meth) acrylic resin may further include other monomers in addition to the aforementioned monomers. For example, a vinyl cyanide monomer, a maleimide monomer, a vinyl monomer including an aromatic ring, and the like may be further included.

The vinyl cyanide monomers include acrylonitrile and the like. The maleimide monomers include N-phenylmaleimide, N-cyclohexyl maleimide, N-methyl maleimide, N-butyl maleimide and the like. Vinyl monomers containing aromatic rings include styrene-based monomers, specifically styrene, α-methylstyrene, 3-methylstyrene, p-methylstyrene, p-ethylstyrene, p One or two selected from the group: -propyl styrene, 4- (p-methylphenyl) styrene, 1-vinylnaphthalene, p-chlorostyrene, m-chlorostyrene and p-nitrostyrene; Although these compounds etc. are mentioned, it is not limited only to these.

As the monomer capable of producing a (meth) acrylic resin having a glass transition temperature of 0 ° C. or more among the monomers, any monomer having a glass transition temperature of 0 ° C. of the homopolymer of each monomer may be used. In the present invention, methyl methacrylate (MMA) may be mainly used, and the content thereof preferably includes 50 mol% or more of methyl methacrylate in the (meth) acrylic resin.

In order to manufacture the (meth) acrylic resin having a glass transition temperature of 0 ° C. or more, a monomer having a glass transition temperature of less than 0 ° C. in addition to the monomer may be used as a comonomer, in which case the glass transition temperature of the copolymer is 0. The amount may be adjusted so as to be higher than or equal to ℃.

In addition, the monomer capable of producing a (meth) acrylic resin having a glass transition temperature of less than 0 ° C among the monomers may typically include butyl acrylate (BA). In addition, butyl (meth) acrylate and ethyl (meth) ) Acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) Acrylate, n-tetradecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, and the like, these monomers alone or mixed two or more kinds Can be used.

In particular, when the (meth) acrylic resin having a glass transition temperature of less than 0 ° C forms a main chain of the graft copolymer, a resin having a different glass transition temperature in the main chain of the copolymer, for example, a (meth) acrylic type having a glass transition temperature of 0 ° C or more In order for the resin to be graft polymerized, a method of introducing a functional group capable of reacting with radicals may be applied to the (meth) acrylic resin having a glass transition temperature of less than 0 ° C. At this time, in order to introduce a functional group capable of reacting with a radical to the (meth) acrylic resin having a glass transition temperature of less than 0 ° C, a (meth) acrylic acid ester monomer having a functional group in addition to the aforementioned (meth) acrylic monomer is added. It is preferable. Examples of the (meth) acrylic acid ester monomer having the functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxy. (Meth) acrylic acid ester monomers including hydroxy such as hexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate; (Meth) acrylic acid ester monomers containing an epoxy such as 2-glycidyl (meth) acrylate; (Meth) acrylic acid ester monomers including carboxylic acids such as acrylic acid, methacrylic acid, acrylic acid dimer, itaconic acid, maleic acid, maleic anhydride, crotonic acid, β-carboxyethyl acrylate, etc. may be used, and these are 1 The species may be used alone or in a mixture of two or more thereof. However, the present invention is not limited only to these examples.

In order to prepare a (meth) acrylic resin having a glass transition temperature of less than 0 ° C., a monomer having a glass transition temperature of 0 ° C. or more in addition to the above monomer may be used as a comonomer, in which case the glass transition temperature of the copolymer is 0 ° C. The amount can be adjusted to be used below.

In the present invention, the graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures is made of (meth) acrylic resins having a low glass transition temperature, and a (meth) having a high glass transition temperature. The acrylic resin may form a side chain or vice versa. In the present invention, the graft copolymer preferably has a structure in which a (meth) acrylic resin having a low glass transition temperature forms a main chain, and a (meth) acrylic resin having a high glass transition temperature forms a side chain. For example, the graft copolymer has a structure in which at least one (meth) acrylic resin having a glass transition temperature of less than 0 ° C forms a main chain, and at least one of the (meth) acrylic resins having a glass transition temperature of 0 ° C or more forms a side chain. Can be.

The graft copolymer has a weight average molecular weight of 50,000 to 2 million, more preferably 50,000 to 500,000, the number average molecular weight of 10,000 to 1 million, more preferably in the range of 10,000 to 300,000 It is preferable.

In the present invention, the content ratio of the (meth) acrylic resin having a glass transition temperature of less than 0 ° C. and the (meth) acrylic resin having a glass transition temperature of 0 ° C. or more is 95 to 5 to 5 to 95, more preferably in weight ratio. It is preferable that it is in the range of 90 to 10 to 10 to 90.

According to an exemplary embodiment of the present invention, a) preparing a first (meth) acrylic resin comprising a first (meth) acrylic monomer, b) reacting with radicals in the main chain of the first (meth) acrylic resin Introducing a functional group capable of c) radically polymerizing a second (meth) acrylic monomer to the modified first (meth) acrylic resin obtained in the step b), and then applying the first to the first (meth) acrylic resin. Preparing a graft copolymer obtained by graft polymerization of a (meth) acrylic resin and a second (meth) acrylic resin having a different glass transition temperature, and d) using a graft copolymer obtained in step c). It provides a method for producing an optical film comprising the step of forming.

Step a) is a step of preparing the first (meth) acrylic resin, and in order to introduce a functional group capable of reacting with radicals in the main chain of the first (meth) acrylic resin in step b), It is preferable to add a (meth) acrylic acid ester monomer having various functional groups to the first (meth) acrylic monomer. Preferred examples of the (meth) acrylic acid ester monomer having the functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6- (Meth) acrylic acid ester monomers including hydroxy such as hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate; (Meth) acrylic acid ester monomers containing an epoxy such as 2-glycidyl (meth) acrylate; (Meth) acrylic acid ester monomers including carboxylic acids such as acrylic acid, methacrylic acid, acrylic acid dimer, itaconic acid, maleic acid, maleic anhydride, crotonic acid, β-carboxyethyl acrylate, and the like, but are limited to these examples only. It doesn't happen. The amount of the (meth) acrylic acid ester monomer having a functional group added at the time of preparing the first (meth) acrylic resin is preferably 0.1-50 mol%, more preferably 0.1-10 mol%.

Subsequently, step b) is a step of introducing a functional group capable of reacting with radicals in the main chain of the first (meth) acrylic resin prepared in step a). The functional group capable of reacting with the radical is a -SH group.

Specifically, in one embodiment of step b), as a method of introducing a -SH group to the first (meth) acrylic resin, a hydroxyl group or a carboxyl group in the resin, a mercapto acid (Mmercaptoacetic acid), mercapto An alcohol, or mercaptoester, can be used which comprises esterifying, in the presence or absence of a catalyst. In this step, the amount of -SH group that can be introduced into the first (meth) acrylic resin may be introduced in various amounts depending on the reaction conditions. For example, the degree of esterification may be adjusted to 0.1-100 mol%, more preferably 50-100 mol% with respect to the functional groups of the entire hydroxyl group or carboxyl group, thereby introducing various concentrations of the -SH group.

As the catalyst that can be used in step b), an acid catalyst may be typically used. Examples of the acid catalyst usable include inorganic acids of sulfuric acid or hydrochloric acid, organic acids such as methanesulfonic acid and paratoluenesulphonic acid, and Lewis acids such as boronic acid. The acid catalyst used in step b) is not particularly limited in amount.

The first (meth) acrylic resin in which the mercapto group is introduced may act as a chain transfer agent in a subsequent radical polymerization process, and may serve to provide an active site for graft polymerization (Journal of Polymer Science 1959, p411-423).

In the step c), the second (meth) acrylic monomer is added to the modified first (meth) acrylic resin obtained in the step b) and subjected to radical polymerization, so that the first (meth) is added to the first (meth) acrylic resin. The graft copolymer to which the 2nd (meth) acrylic-type resin from which acrylic resin differs from glass transition temperature is graft-polymerized can be manufactured.

In the step c), the amount of the modified first (meth) acrylic resin obtained in the step b) may be controlled in various amounts from 1 to 50 parts by weight based on 100 parts by weight of the second (meth) acrylic monomer. . The second (meth) acrylic monomer refers to a (meth) acrylic monomer that may be included in a second (meth) acrylic resin having a different glass transition temperature from the first (meth) acrylic resin, and examples thereof are as described above. In the method of manufacturing an optical film according to the present invention, the first (meth) acrylic resin is a (meth) acrylic resin having a glass transition temperature of less than 0 ° C, and the second (meth) acrylic resin is a (meth) having 0 ° C or more. It is preferable that it is acrylic resin.

Also in step c), a (meth) acrylic acid ester monomer having a functional group may be added in addition to the second (meth) acrylic monomer. Preferred examples of the (meth) acrylic acid ester monomer having a functional group are the same as those which can be used in step a) above.

As the radical polymerization in step c), a method known in the art may be used, and the scope of the present invention is not limited by the polymerization method. For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization are possible, but are not limited to these examples.

As the polymerization initiator, for example, an initiator activated by heat or an initiator activated by light may be used. Specifically, thermally activated initiators such as azo compounds such as azobis (isobutyronitrile), peroxide compounds such as benzoyl peroxide, benzophenone, benzoin ethyl ether and 2,2'-dimethoxy-2-phenyl Initiators activated by light such as acetophenone may be used, but are not limited to these examples. The amount of the polymerization initiator is not particularly limited, but in order to obtain an appropriate molecular weight of the resulting graft copolymer, it is generally used in a weight ratio of 0.01 to 5, more preferably 0.1 to 1 relative to the second (meth) acrylic monomer. Can be.

In addition, a chain transfer agent may be added to appropriately control the molecular weight. Suitable chain transfer agents are suitable such as methane-based or alpha methyl styrene dimers such as dodecyl methane, lauryl methane and the like.

Although the said polymerization reaction temperature has a some fluctuation | variation for balance with the other polymerization conditions, it can be 30-130 degreeC normally, Preferably it is 40-120 degreeC, More preferably, it can be 40-90 degreeC. In addition, although reaction time changes with reaction conditions, such as reaction temperature, a kind, or concentration of monomer, it can be made into 2 to 24 hours normally. Fillers, reinforcing agents, stabilizers, colorants and antioxidants may be further added as needed during the radical polymerization.

Examples of the solvent used in the polymerization include ethers such as tetrahydrofuran, diethyl ether and dioxane, hydrocarbons such as n-hexane, petroleum ether, toluene, benzene and xylene, methanol, ethanol and isopropanol, and the like. Ketones such as alcohols, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, N, N-dimethyl formamide, dimethyl sulfoxide and the like. Each of these solvents may be used alone, or two or more thereof may be used in combination. It is preferable to perform the said polymerization reaction in inert gas atmosphere. As an inert gas, nitrogen gas, argon gas, etc. are mentioned, for example.

In the above method, the molecular weight of the graft copolymer and the graphene are controlled by controlling the amounts of precursors, polymerization initiators, and second (meth) acrylic monomers to introduce functional groups capable of reacting with radicals in the main chain of the first (meth) acrylic resin. The degree of heat and thermal stability can be controlled.

In the step d), the graft copolymer may be prepared as an optical film using a method such as extrusion molding, inflation molding, or solution softening, which is a method of preparing a general film as a primary molding process. The optical film is preferably used for industrial purposes in itself, that is, in an unstretched state, but may be used as a retardation film by imparting retardation in a stretching operation as a secondary molding process in the next step.

In addition, when manufacturing the optical film according to the present invention may be mixed with the commercialized acrylic resin in addition to the above-described graft copolymer to improve productivity. At this time, the mixing ratio of the graft copolymer and the acrylic resin is not particularly limited, and the mixing ratio may be mixed in a range in which the mechanical properties of the obtained optical film are not lowered. Preferably, the weight ratio between the graft copolymer and the acrylic resin may be mixed in the range of 95: 5 to 5:95, and more preferably in the range of 80:20 to 20:80. If the weight ratio of the acrylic resin is more than 95% may not have the physical properties suitable for use as an optical film. The specific type of the acrylic resin is not particularly limited and may be a commercially available type. For example, polymethyl methacrylate (PMMA) may be used.

When the film is produced by extrusion molding as the primary molding, a film of any thickness can be produced by passing a thin gap of the die called a T-die. At this time, in order to prevent appearance defects due to gas foaming, it is preferable to heat and dry the graft copolymer at a temperature in the range of 80 to 130 ° C in advance. Extrusion is preferably performed at a temperature sufficiently higher than the glass transition temperature at which the graft copolymer melt flows to suppress the orientation of the molecular chain. For cooling and solidifying the film in the molten state after passing through the die, a low temperature metal roller or a steel belt may be used.

When manufacturing a film by the solution softening method as a primary shaping | molding process, the solvent which a graft copolymer can be soluble is selected, and a some solvent can be used as needed. Specific examples of the solvent that may be used in the solution softening method include methylene chloride, chloroform, chlorobenzene, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, and the like. no. In particular, a good solvent and a poor solvent for the graft copolymer may be combined to control the volatilization rate. During drying in the solution softening method, it is preferable that bubbles or internal voids are not formed in the film by setting heating conditions, and the concentration of the residual solvent is 0.1 wt% or less.

The optical film produced by the primary molding process by the above method is preferably 30 to 500 ㎛ thickness.

In the case where the optical film prepared as described above is further stretched, when the glass transition temperature of the graft copolymer is referred to as Tg, it may be performed at a temperature of Tg-20 ° C to Tg + 30 ° C. The glass transition temperature indicates a region from the temperature at which the storage modulus of the graft copolymer begins to decrease, and thus the loss modulus becomes larger than the storage modulus, at which the orientation of the polymer chain is relaxed to be lost. The glass transition temperature can be measured by differential scanning calorimetry (DSC).

In addition, the present invention is a liquid crystal display device comprising a liquid crystal cell, and a first polarizing plate and a second polarizing plate provided on both sides of the liquid crystal cell, glass between at least one of the first polarizing plate and the second polarizing plate and the liquid crystal cell Provided is a liquid crystal display device comprising at least one optical film comprising a graft copolymer comprising two or more kinds of (meth) acrylic resins having different transition temperatures.

The present invention also provides a polarizing plate comprising a polarizer and an optical film comprising a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures provided as protective films on one or both surfaces of the polarizer. to provide.

When only one surface of the polarizer is provided with the optical film according to the present invention as a protective film, the other surface may be provided with a protective film known in the art. On the other side of the protective film, a triacetate cellulose (TAC) film, a polynorbornene-based film made of ring opening metathesis polymerization (ROMP), and a ring-opened polymerized cyclic olefin-based polymer were further hydrogenated (HROMP ( Ring opening metathesis polymerization followed by hydrogenation) A polymer, a polyester film, or a polynorbornene-based film prepared by addition polymerization may be used. In addition, a film made of a transparent polymer material may be used as a protective film, but is not limited thereto.

As the polarizer, a film made of polyvinyl alcohol (PVA) containing iodine or dichroic dye may be used. The polarizer may be prepared by dyeing iodine or dichroic dye on the PVA film, but a method of manufacturing the same is not particularly limited. In the present specification, the polarizer means a state not including a protective film, and the polarizing plate means a state including a polarizer and a protective film.

In the polarizing plate according to the present invention, the protective film and the polarizer may be laminated by a method known in the art.

For example, the lamination of the protective film and the polarizer may be made by an adhesive method using an adhesive. That is, first, an adhesive is coated on the surface of the PVA film, which is a protective film or a polarizer, using a roll coater, gravure coater, bar coater, knife coater, capillary coater, or the like. Before the adhesive is completely dried, the protective film and the polarizer are laminated by heating or pressing at room temperature with a lamination roll. In the case of using a hot melt adhesive, a heat press roll should be used.

Adhesives that can be used for lamination of the protective film and the polarizer include one-component or two-component PVA adhesives, polyurethane adhesives, epoxy adhesives, styrene butadiene rubber (SBR) adhesives, or hot melt adhesives, but only in these examples. It is not limited. When using a polyurethane adhesive, it is preferable to use the polyurethane adhesive manufactured using the aliphatic isocyanate type compound which does not yellow by light. When using one-component or two-component dry laminate adhesives or adhesives with relatively low reactivity between isocyanates and hydroxyl groups, a solution-type adhesive diluted with an acetate solvent, a ketone solvent, an ether solvent, or an aromatic solvent, etc. You can also use At this time, the adhesive viscosity is preferably low viscosity of 5000 cps or less. The adhesives are excellent in storage stability and preferably have a light transmittance of 90% or more at 400 to 800 nm.

A tackifier can also be used if it can exert sufficient adhesive force. The adhesive is preferably cured by heat or ultraviolet rays after lamination, and thus the mechanical strength is improved to the level of the adhesive. The adhesive strength is also large, and thus the adhesive strength is such that the adhesive cannot be peeled off without breaking of either film to which the adhesive is attached. It is preferable.

Specific examples of the pressure-sensitive adhesives that can be used include natural rubber, synthetic rubber or elastomer, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate or modified polyolefin-based pressure-sensitive adhesive having excellent optical transparency, and a curing type in which a curing agent such as isocyanate is added thereto. An adhesive is mentioned.

In addition, the present invention is a liquid crystal display device comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate provided on both sides of the liquid crystal cell, wherein at least one of the first polarizing plate and the second polarizing plate of the polarizer and the polarizer Provided is a polarizing plate comprising an optical film including a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures provided as protective films on one or both surfaces thereof.

Looking at Figure 1 illustrating the above liquid crystal display as follows. In FIG. 1, an optical film according to the present invention may be disposed as a protective film on one or both surfaces of at least one polarizing film of the polarizing plate 11 and the polarizing plate 12. The optical film according to the present invention may be disposed as an inner protective film or may be disposed as an outer protective film. Although FIG. 1 shows that the retardation film is provided, the presence of the retardation film is not essential. In addition, although the backlight is illustrated as being disposed on the polarizer 12 side in FIG. 1, the backlight may be disposed on the polarizer 11 side.

The liquid crystal display device including the polarizing plate according to the present invention described above may further include the optical film according to the present invention between the polarizing plate and the liquid crystal cell.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

Example

a) Preparation of First Acrylic Resin

1) Preparation of First Acrylic Resin [A]

93 g of butyl acrylate, 7 g of 2-hydroxyethyl acrylate, 43 g of toluene, 0.2 g of initiator AIBN, and 0.1 g of 1-octylmerethane were added dropwise to 70 ° C. and 250 ml reactor over 4 hours, and further 3 hours were 95 ° C. Polymerization was carried out to prepare a polymer. The unreacted monomer in the solution was measured by gas chromatography to confirm that the conversion was 98%. (Molecular weight: Mw = 215k, Mn = 70k)

2) Preparation of First Acrylic Resin [B]

97 g of butyl acrylate, 3 g of 2-hydroxyethyl acrylate, 100 g of toluene, 0.7 g of initiator AIBN, and 0.73 g of 1-octylmerethane were added dropwise to the reactor at 70 ° C over 250 hours over 4 hours, and further 3 hours at 95 ° C. Polymerization was carried out to prepare a polymer. The unreacted monomer in the solution was measured by gas chromatography to confirm that the conversion was 98%. (Molecular weight: Mw = 43.3k, Mn = 15.3k)

3) Preparation of First Acrylic Resin [C] and [D]

As shown in Table 1, the first acrylic resins [C] and [D] having various functional groups and molecular weights were prepared. In this case, the reaction temperature and the reaction time were prepared in the same manner as in 1).

First acrylic resin [A] [B] [C] [D] BA (g) (butyl acrylate) 93 97 97 97.5 HEA (g) (hydroxyethyl acrylate) 7 3 3 2.5 ¹⁾ Toluene (g) 43 100 60 21 AIBN (g) 0.2 0.7 0.2 0.04 1-octyl merethane (g) 0.1 0.73 0.15 0.16 Conversion (%) 98 98 97 95 Mw 215k 43.3k 95k 123k Mn 70k 15.3k 40k 51k PDI 3.09 2.9 2.3 2.1

1) 4-hydroxybutyl acrylate

b) of the first acrylic resin In the main chain Radicals and  Introduction of functional groups that can react

200 g of toluene was further added to 200 g of the first acrylic resin [A] solution prepared in a), and 1 g of p-toluene sulfonic acid and 6 g of thioglycolic acid were added thereto under reflux. The reaction was carried out for 4 hours. After the reaction was completed, the mixture was added dropwise into methanol to precipitate. Then, toluene was added to the precipitate, followed by heating to remove azeotropic methanol in the polymer. Through this process, the first acrylic resin [A '] polymer solution including SH was obtained.

In addition, modified first acrylic resins [B '], [C'], and [D '] having various functional groups and molecular weights were prepared as shown in Table 2. In each case, the amount of the polymerization solution, the amount of the solvent, the reaction temperature, and the reaction time were performed in the same manner as the process of preparing the modified first acrylic resin [A '] solution.

Production Example of First Acrylic Resin Containing SH [A '] [B '] [C '] [D '] First acrylic resin [A] [B] [C] [D] Amount of first acrylic resin solution (g) 200 200 200 200 Toluene (g) 200 200 200 200 Thioglycolic acid 6 5 5 4 Amount of acid catalyst One 0.8 0.8 One

Acid catalyst: p-toluene sulfonic acid

c) Graft  polymerization

Production Example  1 to 3

32 g of the modified first acrylic resin [A '] solution obtained in step b) (TSC 40%), 79.17 g of MMA, 4.17 g of MA, and 0.26 g of AIBN were placed in a 250 mL polymerizer and maintained at 70 ° C. in a nitrogen atmosphere for 12 hours. The reaction proceeded. After the reaction was terminated, the above polymerization solution was precipitated in methanol to obtain a graft copolymer.

Production Examples 2 and 3 were polymerized as shown in Table 3 below to obtain a polymer in which a second (meth) acrylic resin was grafted to the first (meth) acrylic resin.

Exp. No. Preparation Example 1 Production Example 2 Production Example 3 MMA (g) 79.17 79.17 79.17 MA (g) 4.17 4.17 4.17 Toluene (g) 134 84 65 [A '] solution (g) 32 32 32 AIBN (g) 0.26 0.26 0.26 TSC (%) 40 50 55 Polymerization temperature (℃) 70 70 70 Mw 294k 221k 288k Mn 31k 34k 67k PDI 9.42 6.48 4.28 conversion (%) 79 80 82

Production Example  4 and 5

In Preparation Examples 4 and 5, 20 g (TSC 50%) of the modified first acrylic resin [B '] solution obtained in the step b), 95 g of MMA, 5 g of MA, 0.26 g of AIBN, and 140 g of toluene were placed in a 250 mL polymerizer and nitrogen atmosphere. The reaction proceeded for 12 hours while maintaining at 70 ℃. After the reaction was terminated, the above polymerization solution was precipitated in methanol to obtain a graft copolymer.

Ingredients (Net) Preparation Example 4 Preparation Example 5 MMA 95 95 MA 5 5 AIBN 0.26 0.26 toluene 140 140 [B '] solution 20 20 TSC (%) 50 50 Mw 248k 300k Mn 39k 40k PDI 6.5 7.44 Conversion (%) 83 79 Tg (占 폚) 112 110

Production Example  6 to 8

In Preparation Example 6, 20 g (TSC 50%) of the modified first acrylic resin [C ′] solution obtained in the step b), 72 g MMA, 9 g acrylonitrile (AN), 9 g N-cyclohexylmaleimide (CHMI), and 0.24 g toluene AIBN 90 g was put into a 250 mL polymerizer, and the reaction temperature was heated up at 70 degreeC to 80 degreeC over 4 hours in nitrogen atmosphere, and it heated up over 80 hours at 80 degreeC to 100 degreeC, and maintained for 1 hour. After the reaction was terminated, the above polymerization solution was precipitated in methanol to obtain a graft copolymer. It was dried in an oven at 90 ° C. to obtain a final polymer. (Mw = 181 k, PDI = 3.62)

Preparation Examples 7 and 8 were carried out in the same manner to obtain a graft copolymer as shown in Table 5.

Preparation Example 6 Preparation Example 7 Preparation Example 8 MMA (g) 72 72 72 CHMI (g) 9 9 9 AN (g) 9 9 9 Toluene (g) 90 90 90 [C '] solution (g) 20 20 20 AIBN (g) 0.24 0.1 0.24 Tsc (%) 50 50 50 Mw 181 k 204k 227k Mn 50k 49k 59k PDI 3.62 4.16 3.85 Conversion (%) 85.0 80 93.0 Change in reaction temperature 70-> 80 (4hr elevated), 80-> 100 (4hr elevated), 1hr hold 50 (keep 3 hours), 70 (keep 2 hours), 100 (4 hours warm up) 60-> 80 (8hr temperature rise),-> 100 (4hr temperature rise)

Production Example  9 to 12

In Preparation Example 9, 20 g (TSC 50%) of the modified first acrylic resin [D '] solution obtained in step b), 85.5 g of MMA, 4.5 g of MA, and 90 g of AIBN 0.2 g toluene were placed in a 250 mL polymerizer, and placed in a nitrogen atmosphere. The reaction was carried out while the reaction temperature was raised from 60 ° C to 80 ° C over 8 hours. After the reaction was terminated, the above polymerization solution was precipitated in methanol to obtain a graft copolymer. It was dried in an oven at 90 ° C. to obtain a final polymer. (Mw = 368k, PDI = 5.8)

Preparation Examples 10 to 12 were carried out in the same manner to obtain a graft copolymer as shown in Table 6.

Preparation Example 9 Preparation Example 10 Preparation Example 11 Preparation Example 12 MMA (g) 85.5 85.5 85.5 76 MA (g) 4.5 4.5 4.5 4 Toluene (g) 90 90 90 80 [D '] solution (g) 20 20 20 40 AIBN (g) 0.2 0.2 0.2 0.4 Tsc (%) 50 50 50 50 Mw 368k 261k 221k 281k Mn 68k 71k 53k 33k PDI 5.8 3.18 4.1 7.78 Conversion (%) 65 60 80 90 Change in reaction temperature 60-> 80 (8hr temperature rise) 60-> 80 (8hr temperature rise) 60-> 80 (7hr temperature rise),-> 95 (5hr temperature rise)

Film manufacturing

7.5 g of the graft copolymer prepared in Preparation Example was added to 42.5 g of dichloroethane, and stirred at 30 ° C. for 24 hours to prepare a uniform solution. Filtering with a 5㎛ filter to remove insoluble matter and dust, to prepare a casting solution of 15 wt%. The casting solution was poured into a glass plate for an LCD substrate, cast at a rate of 0.3 m / min with a doctor blade, and dried at room temperature for 60 minutes. Thereafter, the solvent was removed by drying at 60 ° C. for 60 minutes and at 115 ° C. for 90 minutes to remove the polymer film. Physical properties of the prepared film are shown in Table 7 below. The combat rate and the haze of the film were measured with a reflectance-transmittance meter (HR-100, Murakami color research Lab.). In each case, the film has a combat rate of 90% or more, and the haze is as shown in Table 7 below. In addition, the graft copolymer films obtained in each case were not broken when bent, and thus the degree of toughness was much improved compared to the conventional polymethylmethacrylate resin.

Copolymer Type Film thickness (μm) Permeability (%) Haze (%) Toughness Example 1 Preparation Example 1 96 92 0.2 Tough Example 2 Production Example 2 90 93 0.3 Tough Example 3 Production Example 3 80 91 0.4 Tough Example 4 Preparation Example 4 66 93 0.3 Tough Example 5 Preparation Example 5 87 91 0.4 Tough Example 6 Preparation Example 6 86 90 0.4 Tough Example 7 Preparation Example 7 74 90 0.4 Tough Example 10 Preparation Example 10 87 92 0.5 Tough

In addition, the result of extending | stretching the film of the graft copolymer produced in Examples 1, 3, and 7 is put together in following Table 8. Looking at the results, it was found that the phase retardation and the thickness retardation are low, and thus, are suitable for use as an optical film.

Drawing temperature (℃) Elongation (%) Drawing speed (mm / min) Film thickness (㎛) Planar retardation value (nm) Thickness direction retardation value (nm) Example 1 115 25 50 95 9.5 10.8 115 50 50 76 13.9 16 115 100 50 66 19.4 22.5 Example 4 117 25 50 62 2.1 2.4 117 50 50 53 3.5 3.9 117 100 50 40 5.2 6.1 Example 5 142 100 50 66 8.3 7.6 142 50 50 74 5.8 4.1 142 25 50 82 3.7 2.7 Example 7 118 100 50 55 1.2 0.7 118 50 50 64 0.4 0.5 118 25 50 69 0 1.2 Example 10 140 100 50 69 10.5 10.1 140 50 50 76 7.1 6.4 140 25 50 85 4.4 3.3

The optical film according to the present invention includes a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures, and has excellent optical and mechanical properties. It can be usefully used.

Claims (24)

An optical film comprising a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures. The optical film of claim 1, wherein the (meth) acrylic resin includes a (meth) acrylic monomer having or not having at least one substituent selected from an alkyl group having 1 to 12 carbon atoms, alkylene and aromatics. The method according to claim 2, wherein the (meth) acrylic monomers are butyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylate, n-tetradecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) Optical film comprising at least one selected from the group consisting of acrylate and benzyl (meth) acrylate. The method according to claim 2, wherein the (meth) acrylic resin is a (meth) acrylic acid ester monomer containing hydroxy; (Meth) acrylic acid ester monomers including epoxy; And a (meth) acrylic acid ester monomer having at least one functional group selected from the group consisting of a (meth) acrylic acid ester monomer including a carboxylic acid. The optical film of claim 4, wherein the (meth) acrylic resin further comprises at least one monomer selected from the group consisting of a vinyl cyanide monomer, a maleimide monomer, and a vinyl monomer including an aromatic ring. 2. The glass transition temperature of claim 1, wherein at least one of two or more kinds of (meth) acrylic resins having different glass transition temperatures has a glass transition temperature of less than 0 ° C., and at least one of the (meth) acrylic resins has a glass transition temperature of 0 ° C. 3. Optical film that is more than. The optical film of claim 6, wherein the (meth) acrylic resin having a glass transition temperature of 0 ° C. or more includes 50 mol% or more of methyl methacrylate (MMA). The method according to claim 6, wherein the (meth) acrylic resin having a glass transition temperature of less than 0 ℃ butyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, iso Propyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylate, n-tetradecyl (meth) acrylate, 2-ethylhexyl (meth) acrylic An optical film comprising a (meth) acrylic monomer selected from the group consisting of latex, lauryl (meth) acrylate and benzyl (meth) acrylate. The (meth) acrylic resin having a glass transition temperature of less than 0 ° C. according to claim 6, comprising: a (meth) acrylic acid ester monomer containing hydroxy; (Meth) acrylic acid ester monomers including epoxy; And a (meth) acrylic acid ester monomer having at least one functional group selected from the group consisting of a (meth) acrylic acid ester monomer including a carboxylic acid. The optical film according to claim 9, wherein the (meth) acrylic acid ester monomer having the functional group is contained in 0.1 to 50 mol% in the (meth) acrylic resin having a glass transition temperature of less than 0 ° C. The graft copolymer of claim 6, wherein at least one (meth) acrylic resin having a glass transition temperature of less than 0 ° C forms a main chain, and at least one of the (meth) acrylic resins having a glass transition temperature of 0 ° C or more forms a side chain. Optical film which is a structure. The method according to claim 6, wherein the (meth) acrylic resin having a glass transition temperature of less than 0 ℃ and the (meth) acrylic resin having a glass transition temperature of 0 ℃ or more of the graft copolymer is included in a weight ratio of 95: 5 to 5:95 It is optical film. The optical film of claim 1, wherein the graft copolymer has a weight average molecular weight of 50,000 to 2 million, and a number average molecular weight of 10,000 to 1 million. a) preparing a first (meth) acrylic resin comprising a first (meth) acrylic monomer, b) introducing a functional group capable of reacting with a radical into a main chain of the first (meth) acrylic resin, c) The first (meth) acrylic resin and the glass transition temperature to the first (meth) acrylic resin by radical polymerization of the second (meth) acrylic monomer to the modified first (meth) acrylic resin obtained in step b) Preparing a graft copolymer graft polymerized with a different second (meth) acrylic resin, and d) forming a film using the graft copolymer obtained in step c) Way. The method according to claim 14, wherein the first (meth) acrylic resin is a (meth) acrylic resin having a glass transition temperature of less than 0 ℃, the second (meth) acrylic resin is a (meth) acrylic resin having a glass transition temperature of 0 ℃ or more. Method for producing an optical film. The method according to claim 15, wherein the (meth) acrylic resin having a glass transition temperature of less than 0 ℃ is a (meth) acrylic acid ester monomer containing hydroxy; (Meth) acrylic acid ester monomers including epoxy; And a (meth) acrylic acid ester monomer having at least one functional group selected from the group consisting of a (meth) acrylic acid ester monomer including a carboxylic acid. The method according to claim 16, wherein the (meth) acrylic acid ester monomer having the functional group is contained in 0.1 to 50 mol% in the (meth) acrylic resin having a glass transition temperature of less than 0 ° C. The method according to claim 14, wherein the step b) is to introduce an -SH group into the main chain of the first (meth) acrylic resin.  The method according to claim 14, wherein in the step c) using a polymerization initiator of 0.01 to 5 by weight relative to the second (meth) acrylic monomer. The method of claim 14, wherein the step d) uses an extrusion molding method, an inflation molding method or a solution flexible method. The method according to claim 14, wherein the step d) further comprises the step of stretching. A liquid crystal display device comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate provided on both surfaces of the liquid crystal cell, wherein at least one of the first polarizing plate and the second polarizing plate and the liquid crystal cell are any one of claims 1 to 13. A liquid crystal display device comprising at least one optical film comprising a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures according to one of claims. A graft copolymer comprising a polarizer and at least two (meth) acrylic resins having different glass transition temperatures according to any one of claims 1 to 13, which are provided as protective films on one or both surfaces of the polarizer. Polarizing plate comprising an optical film.  A liquid crystal display device comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate provided on both surfaces of the liquid crystal cell, wherein at least one of the first polarizing plate and the second polarizing plate protects the polarizer and one or both surfaces of the polarizer. A polarizing plate comprising an optical film including a graft copolymer comprising two or more kinds of (meth) acrylic resins having different glass transition temperatures according to any one of claims 1 to 13, provided as a film. LCD display device.

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