Description

OPTICAL FILMS, RETARDATION FILMS, AND LCD COMPRISING THE SAMES

Technical Field

[1] The present invention relates to an optical film, a retardation film using the optical film, a process of producing the optical and retardation films, and a liquid crystal display including the optical and retardation films. This application claims priority from Korean Patent Application No. 10-2006-0102954 filed on October 23, 2006 in the KIPO, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[2] Styrene-based resins are advantageous in that economic efficiency is excellent due to low-priced styrene monomer used to prepare the resins and its excellent transparency. Films produced by using the styrene-based resins are considered as useful materials to prepare a retardation film having a positive R value by using the th stretching.

[3] However, the styrene-based resins are disadvantageous in that heat resistance and mechanical properties are poor, with the exception of when the resins are prepared in conjunction with costly special monomers. If the resins are blended with an amorphous polyester polymer in order to avoid the disadvantages of the styrene-based resin, performance of the resulting composition is reduced due to low compatibility.

[4] Polymer, 38(3), pp 577-580, 1997 by Han Mo Jung et al. discloses that when amorphous polyester polymeric block and styrene-based resins are blended, if polyester prepared by using tetramethylbisphenol-A is used as the amorphous polyester polymeric block and poly(styrene-co-acrylonitrile) is used as the styrene-based resin, the compatibility is increased. However, the use of tetramethylbisphenol-A as the monomer is disadvantageous in that economic efficiency is low due to the high cost and it is difficult to obtain desirable physical properties required in the optical film because the styrene-based resin having the desirable compatibility is limited to poly(styrene-co-acrylonitrile) containing acrylonitrile in a content of 5 to 15%.

[5] Meanwhile, in respects to the production of retardation films, Japanese Unexamined

Patent Application Publication Nos. 2000-162436 and 2000-304925 disclose a process of producing a retardation film, which includes attaching an inverse shrinkable film to a film of a thermoplastic resin to perform stretching. However, in the process, it is difficult to control the refractive index in order to increase the z-axis direction refractive index.

[6] Korean Registered Patent No. 0484085 discloses a process of providing a z-axis

direction refractive index by using a combined substance of optical devices including one or more optical retardation films and one or more broadband reflective polarizers. However, this patent requires a complicated process. [7] Korean Unexamined Patent Application Publication No. 2004-29251 discloses a process of providing a z-axis direction refractive index, which includes forming a film by using a copolymer obtained by copolymerizing olefin and N-phenyl maleimide and stretching the film uniaxially or biaxially. However, the patent is disadvantageous in that since material having a high glass transition temperature is used, a stretching process is performed at a high temperature of 22O ⁰ C or more and the thickness retardation (R ) of the film having a thickness of 100 D after +50% stretching is controlled th to be 100 or less. Disclosure of Invention Technical Problem

[8] The present inventors found that when a block copolymer provided in the present invention is used as material of an optical film, an optical film having excellent transparency, heat resistance, and mechanical properties can be obtained. Furthermore, the present inventors found that when the optical film provided in the present invention is uniaxially or biaxially stretched, a retardation film having excellent transparency, heat resistance, and mechanical properties can be obtained.

[9] Accordingly, it is an object of the present invention to provide an optical film that is obtained using a block copolymer, a process of producing the optical film, and a liquid crystal display including the optical film.

[10] It is another object of the present invention to provide a retardation film which has excellent physical properties such as transparency, heat resistance, and mechanical properties due to characteristics of a styrene-based resin and an amorphous polyester polymeric block or a polycarbonate polymeric block which are obtained using uniaxial or biaxial stretching of the optical film, a process of producing the retardation film, and a liquid crystal display including the retardation film. Technical Solution

[11] The present invention provides an optical film including a block copolymer. The block copolymer comprises a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[12] Furthermore, the present invention provides a process of producing an optical film, which comprises the steps of 1) preparing a block copolymer using a) a vinyl

polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block; and 2) forming a film using the block copolymer.

[13] Furthermore, the present invention provides a liquid crystal display including one or more optical films.

[14] Furthermore, the present invention provides a retardation film including a block copolymer. The block copolymer comprises a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[15] Furthermore, the present invention provides a process of producing a retardation film, which comprises the steps of 1) preparing a block copolymer using a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block; 2) forming a film using the block copolymer; and 3) uniaxially or biaxially stretching the film.

[16] Furthermore, the present invention provides a liquid crystal display including one or more retardation films.

[17] Furthermore, the present invention provides an integrated polarizing plate including one or more retardation films; and a polarizing film.

[18] Each of the retardation film as a protective film, provided on a side or both sides of the polarizing film, which comprises a block copolymer comprising a) a vinyl polymeric block containing styrene or a derivative thereof, and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[19] Furthermore, the present invention provides a liquid crystal display including the integrated polarizing plate.

Advantageous Effects

[20] The present invention provides an optical film having excellent transparency and

mechanical strength, which is produced using a block copolymer of a vinyl polymeric block and an amorphous polyester polymeric block or a block copolymer of vinyl polymeric block and a polycarbonate polymeric block.

[21] In addition, a retardation film which is produced using uniaxial or biaxial stretching of the optical film according to the present invention and has a retardation so that R is th larger than 0 and R is 0 or R is larger than 0 and R is not 0 does not have dis- m th m advantages of the styrene -based resin, but excellent heat resistance and mechanical strength. Thus, high contrast characteristics and a low change in color of LCDs are ensured.

Brief Description of the Drawings

[22] FIG. 1 is a view schematically illustrating a structure of a liquid crystal display including a retardation film according to the present invention;

[23] FIG. 2 is a view schematically illustrating a structure of a liquid crystal display including an integrated polarizing plate according to the present invention; and

[24] FIG. 3 is a view schematically illustrating a structure of a liquid crystal display including an integrated polarizing plate according to the present invention.

[25] -Explanation of the signs that are the main part of the drawings-

[26] 1 : OUTER PROTECTIVE FILM

[27] 2: POLARIZING FILM

[28] 4: RETARDATION FILM

[29] 6: LIQUID CRYSTAL CELL

[30] 7 : INNER PROTECTIVE FILM

[31] 8 : POLARIZING FILM

[32] 10: OUTER PROTECTIVE FILM

[33] 11 : FIRST POLARIZING PLATE

[34] 12: SECOND POLARIZING PLATE

Best Mode for Carrying Out the Invention

[35] Hereinafter, the present invention will be described in detail.

[36] The present invention provides an optical film including a block copolymer. The block copolymer comprises a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[37] A styrene monomer which is used to prepare the vinyl polymeric block containing a) styrene or the derivative thereof is represented by the following Formula 1, and specific examples of the styrene monomer include one or more compounds selected

from styrene, -methylstyrene, 3-methylstyrene, p-methylstyrene, p-ethylstyrene, p- propylstyrene, 4-(p-methylphenyl)styrene, 1-vinylnaphthalene, p-chlorostyrene, m- chlorostyrene, and p-nitrostyrene. It is preferable to use styrene or methylstyrene. However, examples of the styrene monomer are not limited thereto. It is preferable that styrene or the derivative thereof be contained in the vinyl polymeric block in an amount of 50 mol% or more so as to have desirable optical properties.

[38] [Formula 1]

[39]

Rn

[40] wherein R is hydrogen; a hydrocarbon radical any one selected from alkyl having 1 to 20 carbon atoms, aryl, alkylaryl and arylalkyl; halogen; nitro group ; or alkoxy group ; n is an integer in the range of 0 to 5; and Rs may be the same as or different from each other with the proviso that n is 2 to 5.

[41] The vinyl polymeric block which contains a) styrene or the derivative thereof may further contain other monomers, in addition to the above-mentioned styrene monomer. For example, a (metha)acrylic ester compound, a vinyl cyanide compound, or a maleimide compound may be further contained. Specific examples of the (metha) acrylic ester compound include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylrate, butyl acrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, and benzyl methacrylate. Specific examples of the vinyl cyanide compound include acrylonitrile. Specific examples of the maleimide compound include N-phenylmaleimide, N-cyclohexylmaleimide, N-methylmaleimide, and N- butylmaleimide. However, examples of the monomers which may be added to styrene or the derivative thereof include vinyl monomers that are capable of being copolymerized with styrene or the derivative thereof and preferably vinyl monomers that are capable of being copolymerized using radical polymerization, but are not limited thereto.

[42] Above bl) an amorphous polyester polymeric block is prepared using the di- carboxylic acid or the derivative thereof and the diol compound. In this connection, at least one of the dicarboxylic acid or the derivative thereof and the diol compound should contain the aromatic group.

[43] The aromatic dicarboxylic acid or the derivative thereof may be represented by the following Formulae 2 to 4. Specific examples of the aromatic dicarboxylic acid or the

derivative thereof include, but are not limited to one or more compounds selected from terephthalic acids, isophthalic acids, phthalic acids, diphenyl-m,m'-dicarboxylic acids, diphenyl-p,p'-dicarboxylic acids, diphenylmethane-m,m'-dicarboxylic acids, diphenylmethane-p,p'-dicarboxylic acids, benzophenone-4,4'-dicarboxylic acids, and p- phenylenediacetic acids. Preferable examples thereof include the terephthalic acids and the isophthalic acids. Examples of the derivative of the dicarboxylic acids include acyl chlorides and acyl bromides of the aromatic dicarboxylic acids, and ester derivatives.

[44] [Formula 2] [45]

[46] [Formula 3] [47]

[48] [Formula 4] [49]

[50] wherein R is hydrogen; a hydrocarbon radical any one selected from alkyl having 1 to 20 carbon atoms, aryl, alkylaryl and arylalkyl; halogen; nitro group; or alkoxy group; X is any one selected from a halogen atom, a hydroxy, and a alkoxy; n is an integer in the range of 0 to 4, m and 1 are each an integer in the range of 0 to 3, k is an integer in the range of 0 to 2; and Rs may be the same as or different from each other with the proviso that n, m, 1, or k is 2 or more.

[51] The aromatic diol may be represented by the following Formulae 5 and 6, and specific examples of the aromatic diol include, but are not limited to one or more compounds selected from hydroquinone, resorcinol,

2,2'-bis(4-hydroxyphenylpropane), 2,2'-bis(4-hydroxy-3,5-dichlorophenylpropane), 1 , 1 '-bis(4-hydroxyphenyl)-cyclohexane, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 4,4'-diphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, and 4,4'-dihydroxydiphenyl methane. Preferable examples of the aromatic diol include 2,2-bis(4-hydroxyphenyl)propane.

[52] [Formula 5]

[53]

[54] [Formula 6]

[55]

[56] wherein R and R' are each independently hydrogen; a hydrocarbon radical selected from alkyl having 1 to 20 carbon atoms, aryl, alkylaryl and arylalkyl; halogen; nitro group; or alkoxy group; W is oxo; or diradical selected from alkylene having 1 to 20 carbon atoms and arylene; n and m are each an integer in the range of 0 to 4; and and R and R' may be the same as or different from each other with the proviso that n and m are in the range of 2 to 4.

[57] When the aromatic carboxylic acid is used as a carboxylic acid used to form bl) the amorphous polyester polymeric block, aliphatic diol represented by the following Formula 7 may be used in addition to aromatic diol. Specific examples of aliphatic diol include ethylene glycol, propylene glycol, 1,4- butanediol, pentamethylene glycol, and hydrogenated bisphenol A. The above-mentioned diols may be used alone or as a mixture of two or more species.

[58] [Formula 7]

[59]

HO Q OH

[60] wherein Q is alkylene diradical having 1 to 20 carbon atoms.

[61] When the aromatic diol is used as a diol compound used to form bl) the amorphous polyester polymeric block, the aliphatic dicarboxylic acid represented by the following Formula 8 or the derivative thereof may be used in addition to aromatic dicarboxylic acids. Specific examples of the aliphatic dicarboxylic acid include adipic acids, pimelic acids, succinic acids, malonic acids, malic acids, citric acids, and sebacic acids. The above-mentioned dicarboxylic acids may be used alone or as a mixture of two or more

species.

[62] [Formula 8]

[63]

[64] wherein Q is alkylene diradical having 1 to 20 carbon atoms, and X and X' are each any one selected from halogen, hydroxy, and alkoxy.

[65] Above b2) the polycarbonate polymeric block is prepared using phosgene and the aromatic diol compound. Phosgene may be a phosgene compound or contain a compound such as triphosgene that is capable of being converted into phosgene in respects to an in situ addition during the preparation of the polycarbonate polymeric block. The aromatic diol compound is the same as the diol compound which may be represented by Formulae 5 and 6 used to prepare bl) amorphous polyester.

[66] The block copolymer according to the present invention may be a A-(B-A) -B type, n a A-(B-A) type, or a mixture type. In this connection, A is an amorphous polyester polymeric block or a polycarbonate polymeric block, and B is a vinyl polymeric block, n is an integer of 0 or more, and m is an integer of 1 or more.

[67] It is preferable that a weight ratio of the amorphous polyester polymeric block or the polycarbonate polymeric block and the vinyl polymeric block be 90: 10 to 5:95 in the block copolymer. If the weight ratio deviates from the above-mentioned range, the block copolymer may not have desirable physical properties required when the block copolymer is used for optical films or retardation films.

[68] Furthermore, preferably, number average molecular weights of the amorphous polyester polymeric block or the polycarbonate polymeric block and the vinyl polymeric block, which are used to prepare the block copolymer, are each 1,000 or more. The preparation of the block copolymer, which contains the vinyl polymeric block having styrene or the derivative thereof and the amorphous polyester polymeric block of the dicarboxylic acid or the derivative thereof and the diol compound or the polycarbonate polymeric block, may be performed using a process known in the related art.

[69] For example, the block copolymer of the vinyl polymeric block and the amorphous polyester polymeric block may be prepared using the process which is disclosed in U.S. Pat. No. 4,980,418, the disclosure of which is incorporated herein by reference in its entirety. For example, the block copolymer may be prepared using the following three types of processes.

[70] First, a block copolymer of polyester polymeric block and vinyl polymeric block may be prepared using a preparation process which includes the steps of (a) performing radical polymerization of vinyl monomers by using dicarboxylic acids, diol, or diester containing chemical species initiating the radical polymerization as a polymerization initiator to form the vinyl polymeric block, which has a carboxyl, hydroxyl, or ester terminal group; and (b) performing poly condensation for formation of polyester polymeric block by using the vinyl polymeric block as a part of the dicarboxylic acids, diol, or hydroxycarboxylic acid component.

[71] Second, a block copolymer of polyester polymeric block and vinyl polymeric block may be prepared using a preparation process which includes the steps of (a) performing polycondensation using dicarboxylic acid dihalide containing chemical species initiating radical polymerization to form an azo-containing polyester polymeric block as a dicarboxylic acid component; and (b) performing radical polymerization of vinyl monomers by using the azo-containing polyester polymeric block as a polymerization initiator.

[72] Third, a block copolymer of polyester polymeric block and vinyl polymeric block may be prepared using a preparation process which includes the steps of (a) performing radical polymerization of vinyl monomers by using dicarboxylic acid dihalide containing chemical species initiating the radical polymerization as a polymerization initiator to form the vinyl polymeric block, which has a carboxylic acid halide terminal group; and (b) performing polycondensation for formation of polyester polymeric block by using the vinyl polymeric block as a part of an acid component.

[73] In the three preparation processes, the chemical species which initiate the radical polymerization include azo, peroxy and the like. The three preparation processes will be described in detail when azo is used as the chemical species.

[74] In the first preparation process, the radical polymerization of the vinyl monomers is performed using dicarboxylic acids, diol, or diester containing azo as the polymerization initiator to form the vinyl polymeric block. For example, dicarboxylic acids, diol, and diester containing azo are shown in the following Structural Formulae 9 to 11.

[75]

CH ₃ CH ₃ <9)

HOOC — R. ¹ C — TsT- N — C — R ¹ — COOH

I 1

CN CN

O CtT ₃ CK ₃ O (I 0)

, ^H Il I I I ^H ,

I I

CHi CK ₃

[76] wherein R is an alkylene group having 1 to 4 carbon atoms, and R and R are independently an alkyl group having 1 to 4 carbon atoms. Preferable examples of di- carboxylic acids, diol, and diester containing azo include 4,4'-azobis(4-cyanopentanic acid), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], and dimethyl 2,2'-azobisisobutyrate.

[77] When the radical polymerization is performed using dicarboxylic acids, diol, or diester containing azo as the polymerization initiator, it is preferable to perform the radical polymerization at a temperature that is the same as or higher than a temperature at which the azo group is decomposed. The amount of dicarboxylic acids, diol, or diester containing azo is preferably 1 to 30 mol% and more preferably 1 to 20 mol% based on the total mole of the vinyl monomers. In order to control the degree of polymerization of the vinyl polymeric block, the amount of dicarboxylic acids, diol, or diester containing azo may be adjusted. The vinyl polymeric block which is prepared using the above-mentioned process has a carboxyl, hydroxyl, or ester terminal group at both ends thereof. It is preferable that a chain transfer agent be not used so that the vinyl polymeric block has the above-mentioned functional groups at the ends thereof.

[78] The vinyl polymeric block which has a carboxyl, hydroxyl, or ester terminal group at the ends thereof is mixed with a reactant which is used to form the polyester polymeric block, for example, hydroxycarboxylic acid, dicarboxylic acid, dicarboxylic acid diester, diol or the like. The mixture is subjected to copolycondensation using a process such as melt polycondensation which is known in the related art. The block copolymer of the vinyl polymeric block and the polyester polymeric block may be obtained using the above-mentioned process. During the melt polycondensation, it is preferable to use salts of antimony, titanium, tin, or other metals as a catalyst. The above-mentioned preparation process is useful to prepare the block copolymer of the polyester polymeric block containing polyethylene terephthalate or polybutylene terephthalate and the vinyl polymeric block containing maleimide, acrylonitrile, or an

alkenyl aromatic compound. The block copolymer may be prepared in a A-(B-A) type, and A and B are the polyester polymeric block and the vinyl polymeric block, respectively.

[79] During the second preparation process, the polycondensation is first performed to prepare the polyester polymeric block. With respect to the polycondensation, it is preferable to perform the interfacial polycondensation. During the polycondensation, azo-containing dicarboxylic acid dihalide is used as a part of the dicarboxylic acid component to achieve the copolycondensation. The catalyst which is used during the polycondensation may be selected from tertiary amine such as triethylamine and tripropylamine; a tetravalent ammonium compound such as tetraethylammonium bromide, benzyltriethylammonium chloride, and trimethylbenzylammonium chloride; and tetravalent phosphonium such as n-butyltriphenylphosphonium bromide. Azo- containing dicarboxylic acid dichloride is shown in the following Structural Formula 12.

[80]

[81] wherein R is an alkylene group having 1 to 4 carbon atoms. It is preferable to use

4,4'-azobis(4-cyanopentanoyl chloride) as the azo-containing dicarboxylic acid dihalide. The amount of azo-containing dicarboxylic acid dihalide is preferably 1 to 30 mol% based on the total mole of the acid components used to form the polyester polymeric block. In the final block copolymer, the length of the polyester block polyemr may be adjusted by changing the amount of dicarboxylic acid dihalide. In order to control the molecular weight of polyester, monovalent phenol such as phenol, cresol, xylenol, p-phenylphenol, and o-phenylphenol and alcohol may be used as a molecular weight controlling agent. In order to prevent side reactions, the polymerization is performed at 4O ⁰ C or less and preferably 2O ⁰ C or less. The polyester polymeric block which is prepared under the above-mentioned condition contains one or more azo groups in a polymer chain thereof.

[82] Subsequently, the radical polymerization of the vinyl monomers is performed using the azo-containing polyester polymeric block as the polymerization initiator to form the block copolymer of the polyester polymeric block and the vinyl polymeric block. It is preferable to perform the radical polymerization using solution polymerization. It is

preferable to perform the polymerization reaction at a temperature that is the same as or higher than a temperature at which the azo group is decomposed in order to perform the radical polymerization. The chain transfer agent may be used in a small amount during the radical polymerization. However, if the chain transfer agent is used in an excessive amount, polymerization efficiency of the prepared block copolymer may be reduced. The length of the vinyl polymeric block may be controlled by changing the reaction temperature and the concentration of the monomers. The preparation process is useful to prepare the block copolymer of the polyester polymeric block containing amorphous aromatic polyester capable of performing the interfacial polycondensation and various types of vinyl polymeric block. The block copolymer may have a A-(B-A) type chemical structure.

[83] During the third process, the radical polymerization of the vinyl monomers is performed using the azo-containing dicarboxylic acid dihalide as the polymerization initiator to prepare the vinyl polymeric block. The azo-containing dicarboxylic acid dihalide contains a compound represented by Structural Formula 12. It is preferable to use 4,4'-azobis(4-cyanopentanoyl chloride) as the azo-containing dicarboxylic acid dihalide. The amount of azo-containing dicarboxylic acid dihalide is 1 to 30 mol% and preferably 1 to 20 mol% based on the total mole of the vinyl monomers. The degree of polymerization of the vinyl polymeric block may be controlled by changing the amount of dicarboxylic acid dihalide. The vinyl polymeric block which is prepared under the above-mentioned condition has carboxylic acid halide groups at both ends thereof.

[84] Subsequently, in order to form the polyester polymeric block using the vinyl polymeric block as the acid component, the interfacial polycondensation is performed to prepare the block copolymer of the polyester polymeric block and the vinyl polymeric block. The interfacial polycondensation is performed at 4O ⁰ C or less and preferably 2O ⁰ C or less in order to prevent side reactions from occurring. The third process is useful to prepare the block copolymer of the polyester polymeric block containing amorphous aromatic polyester capable of performing the interfacial polycondensation and various types of vinyl polymeric block. The block copolymer which is prepared using the third process may have a A-(B-A) type chemical structure.

[85] The block copolymer of the vinyl polymeric block and the polycarbonate polymeric block may be prepared using the following two preparation processes that are similar to the second and the third processes among the three preparation processes of the block copolymer of the vinyl polymeric block and the amorphous polyester polymeric block.

[86] First, a block copolymer of polycarbonate polymeric block and vinyl polymeric block may be prepared using a preparation process which includes the steps of (a)

performing polycondensation by using dicarboxylic acid dihalide containing chemical species initiating radical polymerization instead of a part of a phosgene component to form the polycarbonate polymeric block; and (b) performing the radical polymerization of vinyl monomers using the polycarbonate polymeric block as a polymerization initiator.

[87] Second, a block copolymer of polycarbonate polymeric block and vinyl polymeric block may be prepared using a preparation process which includes the steps of (a) performing radical polymerization of vinyl monomers by using dicarboxylic acid dihalide containing chemical species initiating the radical polymerization as a polymerization initiator to form the vinyl polymeric block, which has a carboxylic acid halide terminal group; and (b) performing polycondensation by using the vinyl polymeric block instead of a part of a phosgene component to form the polycarbonate polymeric block.

[88] In addition, the block copolymer of the vinyl polymeric block and the polycarbonate polymeric block may be prepared using commercial polycarbonate.

[89] The block copolymer of the vinyl polymeric block and the polycarbonate polymeric block may be prepared using a preparation process which includes the steps of (a) reacting polycarbonate and the aromatic diol compound in the presence of base to form polycarbonate which has a phenol group at an end thereof and a reduced molecular weight according to an equivalent of aromatic diol used during the reaction; (b) reacting polycarbonate having the low molecular weight and the phenol group at the end thereof and dicarboxylic acid dihalide containing chemical species initiating radical polymerization to form a polycarbonate macroinitiator; and (c) performing the radical polymerization of vinyl monomers using the polycarbonate macroinitiator as a polymerization initiator. The preparation of polycarbonate having the low molecular weight and the phenol group at the end thereof during step a may be performed using a method which is described in, for example, U.S. Patent No. 6,359,081, the disclosure of which is incorporated herein by reference in its entirety.

[90] The block copolymer of the present invention may further include a filler, a strengthening agent, a stabilizer, a coloring agent, or an antioxidant.

[91] Furthermore, the present invention provides a process of producing an optical film, which includes 1) preparing a block copolymer using a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block; and 2) forming a film using the block copolymer.

[92] As to the optical film of the present invention, the size of the vinyl polymeric block

and the size of the amorphous polyester or polycarbonate polymeric block of the block copolymer may be controlled to use the block copolymer having various types of compositions and average molecular weights as material. Preferably, number average molecular weights of the vinyl polymeric block and the polyester polymeric block or the polycarbonate polymeric block are each 1,000 or more. In the block copolymer, a weight ratio of the polyester polymeric block or the polycarbonate polymeric block and the vinyl polymeric block is in the range of 90:10 to 5:95. If the weight ratio is not in the above-mentioned range, the prepared block copolymer does not have physical properties required in the optical film.

[93] When the film is produced by using the block copolymer, the optical film may be produced by using the block copolymer having the standard reduced weight average molecular weight of polystyrene in the range of 5,000 to 1,000,000 according to primary molding processes such as an extrusion molding process, an inflation molding process, or a solvent casting process which is a typical film production process. The optical film may be industrially used without any modification, or may be subjected to an additional stretching process which is a secondary molding process to be converted into a retardation film having retardation.

[94] When the film is produced by using the extrusion molding process as the primary molding process, the film may pass through a small space between T-dies to have a predetermined thickness. In this connection, it is preferable to heat and dry the block copolymer at a temperature in the range of 80 to 13O ⁰ C in advance so as to prevent an undesirable appearance due to bubbling of gas. As to the condition of the extrusion molding process, it is preferable to perform the molding process at a temperature that is sufficiently higher than a glass transition temperature at which the block copolymer is melted and then starts to flow at a shearing rate of less than 1000/sec in order to suppress alignment of the molecular chain. In order to perform cooling and solidification of the molten film after the film passes through the die, a low-temperature metal roller or a steel belt may be used.

[95] When the film is produced by using the solvent casting process as the primary molding process, a solvent which is capable of dissolving the block copolymer is selected, and a plurality of solvents may be used if necessary. Specific examples of the solvent which is capable of being used during the solvent casting process include, but are not limited to methylene chloride, chloroform, chlorobenzene, 1,4-dioxane, 1,3-dioxolane, and tetrahydrofuran. In particular, a good solvent and a poor solvent in respects to the block copolymer may be combined with each other in order to control a voltailization speed. As to the drying of the substrate by using the solvent casting process, it is preferable that the concentration of the residual solvent be 0.1 wt% or less so as to prevent bubbles or internal voids from being formed in the film by adjusting

the heating condition.

[96] It is preferable that the optical film produced by using the primary molding process have a thickness in the range of 30 to 500 D.

[97] The optical film may have a total transmittance of 90% or more and a haze of 2.5% or less.

[98] In addition, the present invention provides a liquid crystal display which includes one or more optical films containing the block copolymer.

[99] The optical film may be used as a protective film of the polarizing plate constituting the liquid crystal display.

[100] Furthermore, the present invention provides a retardation film including a block copolymer. The block copolymer includes a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[101] Furthermore, the present invention provides a process of producing a retardation film. The process includes 1) preparing a block copolymer using a) a vinyl polymeric block containing styrene or a derivative thereof; and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block; 2) forming a film using the block copolymer; and 3) uniaxially or biaxially stretching the film.

[102] As to the optical film, the retardation film has a specific function and thus is used for the specific purpose. The three dimensional refractive index of the retardation film is controlled to be different from that of the optical film. The film, which is produced by using the block copolymer prepared by using the above-mentioned process according to the extrusion molding process, the inflation molding process, or the solvent casting process, is uniaxially or biaxially stretched to have optical properties that R > 0 and R = 0, or to produce the retardation film having optical properties that th m

R > 0 and R ≠ 0. In general, the biaxial stretching is performed so that stretching th m ratios of two axes are the same as each other to produce the retardation film having the optical properties that R > 0 and R = O. Furthermore, the uniaxial stretching is th m performed, or the biaxial stretching is performed so that stretching ratios of two axes are different from each other to produce the retardation film having the optical properties that R th > 0 and R m ≠ 0. Additionally, in consideration of the retardation which may be provided when the film is produced by using the solvent casting process

or the extrusion molding process, desirable R and R values are provided according to th m the purpose. In this connection, when a stretching direction of the film plane is an x axis, a transverse direction in respects to the film plane is a y axis, and a perpendicular direction (thickness direction) in respects to the film plane is a z axis, the x-axis direction refractive index is called n , the y-axis direction refractive index is called n , x y and the z-axis direction refractive index is called n . R denotes the thickness re- z th tardation and is obtained by using the equation R = d (n - (n + n )/2). Furthermore, R th z x y denotes the in-plane retardation and is obtained by using the equation R = d (n - n ) m m x y

(d is the thickness of the film). As to the uniaxial stretching process, the uniaxial stretching process such as the free width uniaxial stretching or the constant width uniaxial stretching is performed to produce the retardation film. Furthermore, in respects to the biaxial stretching process, the biaxial stretching process such as sequential biaxial stretching and simultaneous biaxial stretching may be performed to produce the retardation film.

[103] During the stretching process of the secondary molding performed to obtain the retardation film, it is preferable to perform the stretching process at a temperature in the range of a temperature that is lower than a glass transition temperature of the block copolymer by 2O ⁰ C to a temperature that is higher than the glass transition temperature of the block copolymer by 3O ⁰ C. The glass transition temperature means a temperature in the range of a temperature at which the storage elasticity of the block copolymer starts to be reduced to allow the loss elasticity to be higher than the storage elasticity to a temperature at which the alignment of the polymer chains becomes loose and thus vanishes. The glass transition temperature may be measured by using a differential scanning calorimeter (DSC). It is preferable to stretch the film so that the stretching speed be in the range of 1 to 100 mm/min and the stretching ratio be in the range of 5 to 300%. The stretching ratio is defined by the following equation: stretching ratio (%) = (length of sample after stretching - length of sample before stretching) / (length of sample before stretching) xlOO.

[104] In order to realize uniform birefringence of the film obtained after the stretching process, it is preferable that the film obtained by using the primary molding process do not have nonuniform alignment or residual distortion and be optically isotropic. To achieve this, it is preferable to perform the solvent casting process as the film formation process. Preferably, in the film which is produced by using the solvent casting process as the primary molding process, the concentration of residual solvent is 0.1 wt% or less when the stretching process is performed as the secondary molding process. When the film is produced by using the extrusion molding process as the primary molding process, it is preferable to perform heat treatment at a temperature that is higher than the glass transition temperature by 3O ⁰ C so as to loose the alignment

of the polymer chains.

[105] The retardation film which is produced by using the secondary molding process preferably has a thickness in the range of 30 to 300 D. It is preferable that the in-plane retardation value of the retardation film be 0 to +500 nm and the thickness retardation value be 0 to +500 D.

[106] In addition, the present invention provides a liquid crystal display including one or more retardation films containing the block copolymer

[107] The retardation film which is produced according to the present invention is used as an optical compensation member for liquid crystal displays. Examples of the retardation film may include a retardation film such as a STN type LCD, a TFT-TN type LCD, a VA type LCD, and an IPS type LCD; a 1/2 wavelength plate; a 1/4 wavelength plate; an inverse wavelength dispersion property film; an optical compensation film; a color filter; a laminate film including a polarizing plate; and a polarizing plate compensation film. The scope of the present invention is not limited thereto, but may be enlarged as long as a birefringence characteristic of R th that is larger than 0 is required.

[108] In particular, the retardation film which is produced by using the process according to the present invention is usefully applied to an IPS (in-plane switching) type liquid crystal display containing liquid crystal having the positive dielectric anisotropy to improve a viewing angle characteristic.

[109] The liquid crystal display which includes one or more retardation films containing the block copolymer will be described with reference to FIG. 1.

[110] In the liquid crystal display which includes a liquid crystal cell 6, a first polarizing plate 11 and a second polarizing plate 12, respectively, provided on both sides of the liquid crystal cell, the retardation film may be provided between the liquid crystal cell 6 and the first polarizing plate 11 and/or the second polarizing plate 12. FIG. 1 illustrates the retardation film which is provided between the first polarizing plate 11 and the liquid crystal cell 6. However, one or more retardation films may be provided between the second polarizing plate 12 and the liquid crystal cell 6, or between the first polarizing plate 11 and the liquid crystal cell 6 and between the second polarizing plate 12 and the liquid crystal cell 6.

[I l l] In addition, FIG. 1 illustrates a backlight which is provided on the second polarizing plate. However, the backlight may be provided on the first polarizing plate.

[112] The first polarizing plate 11 and the second polarizing plate 12 may include a protective film on a side or both sides thereof. Examples of the inner protective film may include, but are not limited to a triacetate cellulose (TAC) film, a polynorbonene film which is produced by using ring opening metathesis polymerization (ROMP), a HROMP (ring opening metathesis polymerization followed by hydrogenation) polymer which is produced by using hydrogenation of a ring-opened cyclic olefin polymer, a

polyester film, and a polynorbonene film which is produced by using addition polymerization. Additionally, a protective film which is made of a transparent polymer material may be used. However, examples of the protective film are not limited thereto.

[113] The present invention provides an integrated polarizing plate including one or more retardation films; and a polarizing film.

[114] The retardation film as a protective film, provided on a side or both sides of the polarizing film, which comprises a block copolymer comprising a) a vinyl polymeric block containing styrene or a derivative thereof, and at least one polymeric block of bl) an amorphous polyester polymeric block of a dicarboxylic acid or a derivative thereof and a diol compound, in which at least one of the dicarboxylic acid or the derivative thereof and the diol compound contains an aromatic group, and b2) a polycarbonate polymeric block.

[115] If the retardation film is provided on only one side of the polarizing film, a protective film which is known in the related art may be provided on another side thereof.

[116] Examples of the polarizing film may include a film which contains iodine or dichromatic dyes and is made of polyvinyl alcohol (PVA). The polarizing film may be produced by applying iodine or dichromatic dyes on the PVA film. However, the production method of the polarizing plate is not limited. In the specification, the polarizing film does not include the protective film, and the polarizing plate includes the polarizing film and the protective film.

[117] In the integrated polarizing plate according to the present invention, the protective film and the polarizing film may be combined with each other by using a method known in the related art.

[118] For example, the combination of the protective film and the polarizing film may be performed according to an attachment method using an adhesive. That is, the adhesive is applied on the surface of the PVA film that is the protective film of the polarizing film or the polarizing film by using a roll coater, a gravure coater, a bar coater, a knife coater, a capillary coater, or the like. Before the adhesive is completely dried, the protective film and the polarizing film are combined with each other using heat pressing or pressing at normal temperature by means of a combination roll. When a hot melt type adhesive is used, the heat pressing roll is used.

[119] Examples of the adhesive which is capable of being used to combine the protective film and the polarizing plate include, but are not limited to a one- or two-liquid type PVA adhesive, a polyurethane adhesive, an epoxy adhesive, a styrene-butadiene rubber (SBR) adhesive, or a hot melt adhesive. If the polyurethane adhesive is to be used, it is preferable to use the polyurethane adhesive produced by using an aliphatic isocyanate

compound which does not cause yellowing due to light. If an one- or two-liquid type dry laminate adhesive or an adhesive having relatively low reactivity in respects to isocyanate and a hydroxy group is used, a solution type adhesive which is diluted with an acetate solvent, a ketone solvent, an ether solvent, or an aromatic solvent may be used. In this connection, it is preferable that the adhesive have low viscosity of 5000 cps or less. Preferably, the adhesive has excellent storage stability and light transmittance of 90% or more at a wavelength of 400 to 800 nm.

[120] Any adhesive may be used as long as the adhesive has desirable adhesion strength.

It is preferable that the adhesive be sufficiently cured by heat or ultraviolet rays after the combination so that mechanical strength required in the adhesive is ensured, and interfacial adhesion strength is large so that stripping does not occur as long as any one of both sides of the film to which the adhesive is attached is not destroyed.

[121] Specific examples of the adhesive may include natural rubber, synthetic rubber, or elastomer having excellent optical transparency, a vinyl chloride/vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, denatured polyolefin adhesive, and a curable adhesive containing a curing agent such as isocyanate.

[122] The present invention provides a liquid crystal display including the integrated polarizing plate.

[123] The liquid crystal display including the integrated polarizing plate will be described with reference to FIG. 2. The retardation film 4 is provided between the polarizing film 2 of the first polarizing plate 11 and the liquid crystal cell 6. In this connection, the backlight is adjacent to the second polarizing plate 12 and an observer is adjacent to the first polarizing plate 11, but they are not limited thereto. In the liquid crystal display which includes the liquid crystal cell 6, the first polarizing plate 11 and the second polarizing plate 12, respectively, provided on both sides of the liquid crystal cell 6, the first polarizing plate 11, the second polarizing plate 12, or both the first polarizing plate 11 and the second polarizing plate 12 may be the integrated polarizing plate according to the present invention.

[124] FIG. 2 illustrates the retardation film which is provided between the polarizing film

2 of the first polarizing plate 11 and the liquid crystal cell 6. However, the retardation film may be provided between the polarizing film 8 of the second polarizing plate 12 and the liquid crystal cell 6, or between the polarizing film 2 of the first polarizing plate 11 and the liquid crystal cell 6 and between the polarizing film 8 of the second polarizing plate 12 and the liquid crystal cell 6. One or more retardation films may be provided on one side or both sides of the polarizing film.

[125] As shown in FIG. 3, the retardation film 4 is provided between the polarizing film 2 of the first polarizing plate 11 and the liquid crystal cell 6. In this connection, the backlight is adjacent to the first polarizing plate 11 and an observer is adjacent to the

second polarizing plate 12, but they are not limited thereto.

[126] If the liquid crystal display according to the present invention includes the integrated polarizing plate, one or more retardation films according to the present invention may be additionally provided between the polarizing plate and the liquid crystal cell. Mode for the Invention

[127] A better understanding of the present invention may be obtained in light of the following Examples which are set forth to illustrate, but are not to be construed to limit the present invention.

[128] EXAMPLE

[129] [Preparation of the macroinitiator A]

[130] 9.08 g of bisphenol-A (39.8 mmol) and 68.0 mg of p-tertiary-butylphenol (0.453 mmol) were added to a 500 mL reactor which contained 3.60 g of sodium hydroxide (90.0 mmol) dissolved in 200 mL aqueous solution, and agitated for 10 min to prepare a clear solution. 83 mg of benzyltriethylammonium chloride (BTEAC) was added thereto. After the reactor was cooled to 12 ⁰ C, 50 mL of methylene chloride solution containing 2.00 g (9.85 mmol) of terephthaloyl chloride (TPC), 2.00 g (9.85 mmol) of isophthaloyl chloride (IPC), and 60.0 mg (0.19 mmol) of 4,4'-azobis(4-cyanopentanoyl chloride) (ACPC) dissolved therein was added and then agitated for 2 hours to perform the polymerization.

[131] After the polymerization, the completion of the reaction and the production of the polymer were performed by using the following procedure. 2.5 mL of methylene chloride solution containing 4 mg of benzoyl chloride dissolved therein was added and the agitation was then performed for 10 min. 10 mL of aqueous solution containing 40 mg of sodium hydroxide and 0.15 g of p-tertiary-butylphenol was added and additional agitation was then performed for 20 min. After the reaction was finished by adding about 2 mL of acetic acid, the agitating device was stopped to perform layer separation, the water layer was removed, and the methylene chloride solution was washed with iced water seven times. The resulting solution was slowly diluted by using an excessive amount of methanol to precipitate the polymer and then filter the polymer, thus producing the white solid. The solid was dried at normal temperature to produce 6.9 g of macroinitiator A.

[132] [Preparation of macroinitiators B to E]

[133] The polymerization was performed by using the same procedure as the production of the macroinitiator A, except that p-tertiary-butylphenol was not used and the reaction composition of the following Table 1 was used. After the polymerization, the completion of the reaction and the production of the polymer were performed by using

the following procedure. 0.4 g of TBP/NaOH (aq) was added to the NaOH aqueous solution, and the additional reaction was performed for 5 min. Next, 0.5 g of benzoyl chloride was added and additional agitation was performed for 5 min. After the reaction was completed, the polymerization solution was subjected to the same process as the production of the macroinitiator A to produce macroinitiators B to E.

[134] Table 1

[135] [Preparation of the block copolymer of polyarylate polymeric block and poly(styrene-co-acrylonitrile) polymeric block]

[136] PREPARATION EXAMPLE 1 [137] 2 g of macroinitiator A which was dissolved in 20 g of dioxane, 4 g of acrylonitrile (AN), and 16 g of styrene (SM) were added to a 100 mL flask having an agitating device at 9O ⁰ C to perform the polymerization. After 3 hours, dilution was performed by using 100 mL of THF (tetrahydrofuran) to stop the reaction. The resulting solution was continuously agitated at normal temperature to be completely dissolved, slowly dropped onto an excessive amount of methanol, and dried to produce 11.4 g of white precipitate. The glass transition temperature which was measured by using a DSC (Differential Scanning Calorimeter) was 115 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC (Gel Permeation Chromatography) was 323,000.

[138] PREPARATION EXAMPLE 2 [139] The procedure of Preparation Example 1 was repeated to produce 13 g of block copolymer of the polyarylate polymeric block and the poly(styrene-co-acrylonitrile) polymeric block, except that the temperature of the flask reactor was set to 8O ⁰ C and

the polymerization time was set to 18 hours.

[140] PREPARATION EXAMPLE 3

[141] The procedure of Preparation Example 1 was repeated to produce 6.7 g of block copolymer of the polyarylate polymeric block and the poly(styrene-co-acrylonitrile) polymeric block, except that the temperature of the flask reactor was set to 9O ⁰ C, the polymerization time was set to 18 hours, and 2 g of acrylonitrile (AN) and 8 g of styrene (SM) were added to initiate the polymerization.

[142] PREPARATION EXAMPLE 4

[143] 3.25 g of macroinitiator B was dissolved in 50 g of dioxane in a 200 mL vessel, 6 g of acrylonitrile and 19 g of styrene were added and then shaken to prepare the uniformly mixed reaction solution. The solution was provided to the hot plate, a temperature of which was controlled at 9O ⁰ C in advance, to initiate the polymerization. After the polymerization was performed for 18 hours, dilution was performed by using 100 mL of tetrahydrofuran to stop the reaction. The resulting solution was continuously agitated at normal temperature to be completely dissolved, slowly dropped onto an excessive amount of methanol, and dried to produce the white precipitate. The glass transition temperature which was measured by using a DSC was 115 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 385,000.

[144] PREPARATION EXAMPLE 5

[145] The procedure of Preparation Example 4 was repeated to produce a polymer, except that 3.25 g of macroinitiator C was dissolved in 51.3 g of dioxane. The glass transition temperature which was measured by using a DSC was 115 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 372,000.

[146] PREPARATION EXAMPLE 6

[147] The procedure of Preparation Example 4 was repeated to produce a polymer, except that 6.5 g of macroinitiator C was dissolved in 51.2 g of dioxane. The glass transition temperature which was measured by using a DSC was 115 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 289,000.

[148] PREPARATION EXAMPLE 7

[149] The procedure of Preparation Example 4 was repeated to produce 15.7 g of white polymer, except that 3.0 g of macroinitiator C was dissolved in 27.0 g of dioxane and the solution containing 30.0 g of styrene dissolved in 30.0 g of dioxane was added thereto. The glass transition temperature which was measured by using a DSC was 109 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 334,000.

[150] PREPARATION EXAMPLE 8

[151] The procedure of Preparation Example 7 was repeated to produce 20.1 g of white polymer, except that 27.0 g of styrene and 3.0 g of N-cyclohexylmaleimide were used instead of 30.0 g of styrene. The glass transition temperature which was measured by using a DSC was 111 ⁰ C and 155 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 293,000.

[152] PREPARATION EXAMPLE 9

[153] The procedure of Preparation Example 7 was repeated to produce 19.5 g of white polymer, except that 27.0 g of styrene and 3.0 g of N-phenylmaleimide were used instead of 30.0 g of styrene. The glass transition temperature which was measured by using a DSC was 111 ⁰ C and 193 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 311,000.

[154] PREPARATION EXAMPLE 10

[155] The procedure of Preparation Example 4 was repeated to produce 22.9 g of white polymer, except that 6.0 g of macroinitiator C was dissolved in 54.0 g of dioxane and 30.0 g of styrene was then added thereto. The glass transition temperature which was measured by using a DSC was 109 ⁰ C, and the polystyrene reduced weight average molecular weight which was measured by using a GPC was 227,000.

[156] [Production of the optical film]

[157] EXPERIMENTAL EXAMPLE 1

[158] 7.5 g of block copolymer which was prepared in Preparation Example 1 was added to 42.5 g of dichloroethane, and the solution which was prepared by performing the agitation at 3O ⁰ C for 24 hours was filtered by using a 5 D filter to prepare a 15 wt% casting solution from which insoluble substances and dust were removed. The casting solution was poured on the glass plate for LCD substrates, subjected to casting by using the doctor blade at a speed of 0.3 m/min, and dried at room temperature for 60 min, at 6O ⁰ C for 60 min, and at 115 ⁰ C for 90 min to remove the solvent and strip the polymer film. The thickness of the produced optical film was 73 D, the total transmittance was 92%, and the haze was 0.5%. The total transmittance and the haze were measured three times, and average values were used. The produced optical film was not broken even though the film was folded.

[159] EXPERIMENTAL EXAMPLES 2 to 9

[160] The procedure of Experimental Example 1 was repeated by using the block copolymers prepared in Preparation Examples 2 to 10 to produce the optical film. In the present examples, the amounts of the polymers and the solutions, and the thickness, the total transmittance, and the haze of the films were measured, and the results are described in the following Table 2. All the produced films had the total transmittance of 90% or more, the refraction index of 1.574 or more, and the haze of less than 0.8%,

except that the haze of the film of Experimental Example 4 was 2.5%. All the optical films had the in-plane retardation of 5 nm or less and the thickness retardation of 8 nm or less. All the optical films were not broken even though the films were folded, with the exception of Experimental Example 8.

Table 2

Production condition of the optical film by using the solvent casting process and properties of the optical film

[162] EXPERIMENTAL EXAMPLE 10

[163] The reactor having the volume of 500 mL, which was heated to 100 ⁰ C by using the jacket, was put in a nitrogen atmosphere, a vessel for supplying the solution containing 100 g of styrene and 20 g of the macroinitiator D dissolved in 200 g of dioxane drop by drop was provided in the reactor. After the mechanical agitating device which was provided in the reactor was operated, the solution drops were provided from the vessel for 2 hours. After the provision of the solution was finished, the additional agitation was performed for 2 hours to conduct the polymerization. The weight average molecular weight of the polymer was 92,308, and the glass transition temperature was 114 ⁰ C.

[164] 7.5 g of the block copolymer was added to 42.5 g of dichloroethane, and the agitation was performed at 3O ⁰ C for 24 hours to prepare the homogeneous solution. The solution was filtered by using a 5 D filter to prepare a 15 wt% casting solution from which insoluble substances and dust were removed. The casting solution was poured on glass, subjected to casting by using the doctor blade at a speed of 0.3 m/min, and dried at room temperature for 60 min, at 6O ⁰ C for 60 min, and at 115 ⁰ C for 90 min to remove the solvent and strip the polymer film. The thickness of the produced optical film was 100 D, Tg of the film was 114 ⁰ C, the total transmittance was 92.5%, and the haze was 0.9%.

[165] EXPERIMENTAL EXAMPLE 11

[166] 2 g of ACPC (4,4'-azobis(4-cyanopentanyl chloride), 30 g of styrene, and 60 g of benzene were added to the spherical reactor which was provided with the agitating device and had the volume of 250 ml, and then agitated. The temperature of the reactor was increased to 8O ⁰ C while the argon gas was continuously injected to perform the polymerization for 9 hours. After the reaction was finished, the reaction mixture was

cooled to normal temperature and poured on an excessive amount of hexane to be precipitated. The precipitated polymer was dried to obtain acid-chloride terminated polystyrene.

[167] 7.6 g of 2,2-bis(4-hydroxyphenyl)propane, 3 g of sodium hydroxide, and 200 g of distilled water were mixed, agitated, and dissolved in the 1 L reactor which was provided with the agitating device. 0.1 g of benzyltriethylammonium chloride and 10 ml of methylene chloride were added while the temperature of the reactor was maintained at 15 ⁰ C and then strongly agitated. In addition, 6.4 g of the diacid chloride mixture containing terephthaloyl chloride and isophthaloyl chloride mixed with each other in the same mole number was dissolved in 333.3 ml of methylene chloride. The solution was added to the alkali aqueous solution which was prepared in advance. The argon gas was injected while the reaction temperature was maintained at 15 ⁰ C, and the resulting solution mixture was strongly agitated to perform the reaction for 2 hours. After the reaction was finished, the reaction mixture was poured on an excessive amount of methanol to be precipitated. The precipitated polymer was washed with deionized water twice and dried in a vacuum to obtain 22.1 g of the polymer. The weight average molecular weight of the obtained polymer was 97,000 and the glass transition temperature was 114 ⁰ C.

[168] 7.5 g of the block copolymer was added to 42.5 g of dichloroethane, and the agitation was performed at 3O ⁰ C for 24 hours to prepare the homogeneous solution. The solution was filtered by using a 5 D filter to prepare a 15 wt% casting solution from which insoluble substances and dust were removed. The casting solution was poured on glass, subjected to casting by using the doctor blade at a speed of 0.3 m/min, and dried at room temperature for 60 min, at 6O ⁰ C for 60 min, and at 115 ⁰ C for 90 min to remove the solvent and strip the polymer film. The thickness of the produced optical film was 100 D, Tg of the film was 114 ⁰ C, the total transmittance was 92.1%, the haze was 3.6%, and the refraction index was 1.5886.

[ 169] [Production of the retardation film]

[170] EXPERIMENTAL EXAMPLE 12

[171] The retardation film was produced by using the optical film which was produced in

Experimental Example 2 to measure optical properties thereof.

[172] The in-plane retardation and the thickness retardation of the retardation film were measured by using the following procedure.

[173] In respects to the thickness retardation, Kobra 21-ADH (trade name) which was manufactured by OJI Scientific Instruments Co., Ltd. was used. The direction in which the refractive index was highest in a plane direction at 590 nm was considered an x axis, the direction which was perpendicular to the x axis in the plane direction was considered an y axis, and the direction which was perpendicular to the xy plane was

considered a z axis, n , n , and n which were the refractive indices in respects to the x y z directions were measured at 590 nm, the thickness of the film layer was measured to measure n , n , and n which were the refractive indices in respects to the axis x y z directions. Next, the thickness retardation and the in-plane retardation of the film were calculated by using the following Equations 1 and 2. [174] [Equation 1]

[175]

[176] wherein n is the refractive index in the direction in which the refractive index is highest in respects to the plane of the film, n is the refractive index in the transverse y direction in respects to n in the plane, n is the refractive index in the direction which is perpendicular in respects to the plane of the film, d is the thickness of the film, and R is the thickness retardation. [177] [Equation 2]

[178]

[179] wherein n is the refractive index in the direction in which the refractive index is highest in respects to the plane of the film, n is the refractive index in the transverse direction in respects to n x in the plane, d is the thickness of the film, and R m is the in- plane retardation.

[180] The in-plane retardation of the sample of the film, which was produced in Experimental Example 2 and used during the stretching, was 5 nm before the stretching, and the thickness retardation thereof was 8 nm before the stretching. The film was stretched under a condition of the temperature of 115 ⁰ C, the speed of 50 mm/min, and the stretching ratio of 100%. The stretching ratio was defined by the following equation.

[181] Stretching ratio (%) = (length of sample after stretching - length of sample before stretching) / (length of sample before stretching) xlOO

[182] The in-plane retardation and the thickness retardation of the film were measured after the stretching, and the results are described in Table 3.

[183] EXPERIMENTAL EXAMPLES 13 to 20

[184] The films which were produced in Experimental Examples 2 to 10 were stretched by using the same procedure as Experimental Example 12 while the stretching condition such as the stretching temperature, the stretching ratio, and the stretching

speed were changed. Next, the retardation was measured, and the stretching condition and the retardation measurement results are described in Table 3. [185] Table 3

Production and optical properties of the retardation film

[186] [Preparation of the polycarbonate macroinitiator] [187] 14.34 g of bisphenol-A, 200 mL of methylene chloride, and 14.0 mL of triethyl amine were added to the spherical reactor which was provided with the dropping funnel and the agitation magnet and had the volume of 250 ml to prepare the transparent solution, and nitrogen bubbling was performed to make a nitrogen atmosphere. The solution containing 5.93 g of triphosgene dissolved in 30 mL of methylene chloride was charged in the dropping funnel, and the triphosgene solution was dropped while the reactor was put in the cooling bath containing iced water so that the inner temperature of the reactor was controlled to be less than 15 ⁰ C. After the dropping was finished, the cooling bath was separated, the temperature was increased to normal temperature, and the polymerization was performed for 24 hours. The weight average molecular weight of polycarbonate sampled from the reaction solution was 9,500, which was measured by using the GPC.

[188] The solution was put in the cooling bath containing the iced water, the solution containing 2.0 g of ACPC dissolved in 10 mL of methylene chloride was dropped, and the reaction was performed while the temperature was increased to normal temperature and the agitation was conducted. After the additional reaction was performed for 24

hours, the reaction mixture was poured on an excessive amount of methanol to perform precipitation. The weight average molecular weight of the obtained polymer was 34,000.

[ 189] [Production of the polycarbonate-polystyrene block copolymer]

[190] PREPARATION EXAMPLE 11

[191] 3.0 g of polycarbonate-macroinitiator which was prepared in the above was dissolved in 20 g of dioxane in the reaction flask which was provided with the agitation magnet and had the volume of 100 mL, 20.0 g of the styrene monomer was added thereto, and the agitation was performed at 8O ⁰ C. After 24 hours, the resulting mixture was diluted with 100 mL of THF to stop the reaction, continuously agitated at normal temperature to be completely dissolved, slowly dropped on an excessive amount of methanol, and dried to obtain 11.0 g of white precipitate. The glass transition temperature which was measured by using the DSC was 112 ⁰ C and the polystyrene reduced weight average molecular weight which was measured by using the GPC was 112,000.

[192] [Production of the polycarbonate-polystyrene block copolymer film]

[193] EXPERIMENTAL EXAMPLE 21

[194] 15 g of the block copolymer which was prepared in Preparation Example 11 was added to 40 g of methylene chloride, and the solution which was prepared by performing the agitation at 3O ⁰ C for 24 hours was filtered by using a 5 D filter to prepare a 15 wt% casting solution from which insoluble substances and dust were removed. The casting solution was poured on the glass plate for LCD substrates, subjected to casting by using the doctor blade at a speed of 0.3 m/min, and dried at room temperature for 60 min, at 6O ⁰ C for 60 min, and at 115 ⁰ C for 90 min to remove the solvent and strip the polymer film. The thickness of the film was 80 D, the total transmittance was 92%, and the haze was 0.5%.