DESCRIPTION

OPTICAL COMPONENT COMPRISING ACRYLIC BLOCK COPOLYMER

TECHNICAL FIELD

[0001] The present invention relates to an optical component comprising an acrylic block copolymer. More particularly, the invention relates to an optical component which is formed from a composition containing an acrylic block copolymer and having excellent melt processability and which is excellent in flexibility, light resistance and transparency.

BACKGROUND ART

[0002] Development of various uses of acrylic block copolymers has been studied in the past because of excellent properties of the copolymers.

For example, in a patent document 1 (National Publication of International Patent No. 508394/2008) and a patent document 2 (WO2008/065982) , an optical film (heat ray reflecting film, polarizing film or the like) having at least one adhesive layer composed of an acrylic block copolymer is disclosed.

[0003] In a patent document 4 (Japanese Patent Laid- Open Publication No. 084658/2007), a near infrared absorbing

sheet using an adhesive obtained by blending an acrylic block copolymer with a near infrared absorbing material is disclosed.

In a patent document 5 (Japanese Patent Laid-Open Publication No. 277574/2003), a transparent flexible material obtained by blending an acrylic block copolymer with a specific methacrylic resin is disclosed.

[0004] In a patent document 6 (Japanese Patent Laid- Open Publication No. 128809/2003), a laminated film using an acrylic block copolymer and having excellent transparency is disclosed.

In a patent document 7 (Japanese Patent Laid-Open Publication No. 349782/1999), a cover sheet using an acrylic block copolymer is disclosed. [0005] In a patent document 8 (Japanese Patent Laid- Open Publication No. 302617/1999), an adhesive sheet using an acrylic block copolymer is disclosed.

As processes for preparing such acrylic block copolymers, there are known, for example, a living polymerization process using a rare earth compound, which is disclosed in a patent document 9 (Japanese Patent Laid-Open Publication No. 93060/1994), a living polymerization process using a mineral acid salt, which is disclosed in a patent document 10 (National Publication of international Patent 507737/1993) , a

living polymerization process using an organoaluminum compound, which is disclosed in a patent document 11 (Japanese Patent Laid-Open Publication No. 335432/1999), and an ATRP living polymerization process disclosed in a non- patent document 1.

[0006] In a patent document 3 (WO2007/011017 ) , a method in which a residual metal derived from a polymerization initiator is highly removed from an acrylic block copolymer obtained by anionic polymerization using an organoaluminum compound to obtain high transparency is disclosed.

[0007] However, studies to apply acrylic block copolymers to optical components taking molding properties and other properties into consideration have not been sufficiently made yet.

Patent document 1: National Publication of International Patent No. 508394/2008

Patent document 2: WO2008/065982

Patent document 3: WO2007/011017 Patent document 4: Japanese Patent Laid-Open Publication No. 084658/2007

Patent document 5: Japanese Patent Laid-Open Publication No. 277574/2003

Patent document 6: Japanese Patent Laid-Open Publication No. 128809/2003

Patent document 7 : Japanese Patent Laid-Open Publication No. 349782/1999 Patent document 8 : Japanese Patent Laid-Open Publication No. 302617/1999

Patent document 9: Japanese Patent Laid-Open Publication No. 93060/1994

Patent document 10: National Publication of international Patent 507737/1993

Patent document 11: Japanese Patent Laid-Open Publication No. 335432/1999

Non-patent document 1: "Macromol . Chem. Phys.", 2000, Vol. 201, pp. 1108-1114 DISCLOSURE OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0008] It is an object of the present invention to provide an optical component which comprises a material containing an acrylic block copolymer and having excellent melt processability and which is excellent in flexibility, light resistance and transparency.

MEANS TO SOLVE THE PROBLEM

[0009] The present inventors have earnestly studied in order to solve the above problems. As a result, they have

found that the above problems can be solved by an optical component formed from a composition containing a specific acrylic block copolymer, and they have achieved the present invention. [0010] That is to say, according to the present invention, the above object is attained by producing an optical component which is an optical component formed from a composition containing an acrylic block copolymer, wherein: the acrylic block copolymer has two or more polymer blocks (A) each of which is synthesized from monomers containing at least one monomer selected from methacrylic esters and acrylic esters and has a glass transition temperature of not lower than 50 ⁰ C, and one or more polymer blocks (B) each of which is synthesized from monomers containing at least one monomer selected from methacrylic esters and acrylic esters and has a glass transition temperature of not higher than 20 ⁰ C.

[0011] The composition used for the optical component preferably has a light transmittance of not less than 90%. The acrylic block copolymer contained in the composition is preferably synthesized by a living polymerization process.

[0012] The composition preferably has a tensile modulus at 25°C of 20 MPa to 2000 MPa.

In a preferred embodiment, the optical component is in the form of a film or a sheet .

[0013] In another preferred embodiment, the optical component is in the form of a tube, a column, a cone or a cone frustum.

The optical component preferably further has an optical function. An example of the optical function is a phase difference function.

[0014] By combining the optical component with an LED light-emitting part, an optical element can be produced.

EFFECT OF THE INVENTION

[0015] According to the present invention, an optical component which comprises a material having excellent melt processability and is excellent in flexibility, light resistance and transparency is provided by taking the above constitution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a group of explanatory views showing a planar shape and a sectional shape of a mold cavity formed in a mold used in the working examples.

Fig. 2 is an explanatory plan view of a light guide, showing measuring points in luminance measurement in the working examples.

Fig. 3 is an exploded explanatory view showing constitution of luminance measurement in the working examples. Description of symbols a: cold-cathode tube b: reflecting sheet c: diffusion sheet d: light guide

BEST MODE FOR CARRYING OUT THE INVENTION [0017] The present invention is described in detail hereinafter.

The acrylic block copolymer used for the optical component of the invention is characterized by having two or more polymer blocks (A) each of which is synthesized from two or more methacrylic ester and acrylic ester monomers and has a glass transition temperature of not lower than 50 ⁰ C and one or more polymer blocks (B) each of which is synthesized from methacrylic ester and acrylic ester monomers and has a glass transition temperature of not higher than 20 ⁰ C. The composition containing such an acrylic block copolymer is excellent in melt processability, and the optical component formed from the composition is excellent in flexibility, light resistance and transparency.

[0018] Examples of the monomers used for the synthesis of the polymer block (A) include methacrylic esters,

such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate and 2-hydroxyethyl methacrylate, and acrylic esters, such as methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate and 2-hydroxyethyl acrylate.

[0019] Of these, methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, 2- hydroxyethyl methacrylate, methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate and 2-hydroxyethyl acrylate are preferable, and methyl methacrylate is more preferable, from the viewpoints of enhancement of transparency and heat resistance of the resulting optical component. The polymer block (A) may be synthesized from one of these methacrylic esters and acrylic esters, or may be synthesized from two or more of them. In the acrylic block copolymer, two or more polymer blocks (A) are contained, and these polymer blocks (A) may be the same as or different from each other.

[0020] Examples of the monomers used for the synthesis of the polymer block (B) include methacrylic esters, such as n-propyl methacrylate, n-butyl methacrylate, isobutyl

methacrylate, arαyl methacrylate, isoamyl methacrylate, n- hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate, phenoxyethyl methacrylate and 2-methoxyethyl methacrylate, and acrylic esters, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate and 2-methoxyethyl acrylate.

[0021] Of these, acrylic esters, such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, phenoxyethyl acrylate and 2-methoxyethyl acrylate, are preferable from the viewpoint of enhancement of flexibility of the resulting optical component.

[0022] Of these, further, n-propyl methacrylate, n- butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate, phenoxyethyl methacrylate, 2-methoxyethyl methacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl

acrylate, phenoxyethyl acrylate and 2-methoxyethyl acrylate are preferable, and ethyl acrylate, n-propyl acrylate, n- butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate and 2-methoxyethyl acrylate are more preferable, from the viewpoints of enhancement of transparency, flexibility, low-temperature resistance and low-temperature properties of the resulting optical component The polymer block (B) may be synthesized from one of these methacrylic esters and acrylic esters, or may be synthesized from two or more of them. When two or more polymer blocks (B) are contained in the acrylic block copolymer, these polymer blocks (B) may be the same as or different from each other. [0023] As monomers used for the synthesis of the polymer block (A) and the polymer Block (B) , methacrylic esters and acrylic esters each of which has a reactive group may be further used within limits not detrimental to the properties of the acrylic block copolymer for use in the invention. Examples of the methacrylic esters and the acrylic esters each of which has a reactive group include glycidyl methacrylate, allyl methacrylate, glycidyl acrylate and allyl acrylate. Such a monomer is used usually in a small amount, and it is used in an amount of preferably not

more than 40% by mass, more preferably not more than 20% by mass, based on the total amount by mass of the monomers used for the synthesis of the polymer blocks.

[0024] As monomers used for the synthesis of the polymer block (A) and the polymer Block (B) , moreover, other monomers may be used in combination, when necessary, within limits not detrimental to the properties of the acrylic block copolymer for use in the invention.

[0025] Examples of the other monomers include methacrylic acid, acrylic acid, styrene, α-methylstyene, p- methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, 1,3- butadiene, isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride and vinylidene chloride. Such a monomer is used usually in a small amount, and it is used in an amount of preferably not more than 40% by mass, more preferably not more than 20% by mass, based on the total amount by mass of the monomers used for the synthesis of the polymer blocks.

[0026] The acrylic block copolymer for use in the invention may have other polymer blocks, when necessary, in addition to the polymer block (A) and the polymer block (B) .

Examples of the other polymer blocks include polymer blocks or copolymer blocks synthesized from monomers, such as methacrylic acid, acrylic acid, styrene, α-methylstyene, p-

methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, 1,3- butadiene, isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride and vinylidene chloride, and polymer blocks comprising polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyurethane and polydimethylsiloxane. In the above polymer blocks, hydrogenation products of polymer blocks synthesized from monomers including diene monomers, such as 1, 3-butediene and isoprene, are also included.

[0027] Although the bonding form of the polymer blocks contained in the acrylic block copolymer of the invention is not specifically restricted, it is preferable from the viewpoints of heat resistance, mechanical strength, surface sticking, etc. of the optical component of the invention that the copolymer takes a form wherein the polymer blocks (A) are bonded to both ends of at least one polymer block (B) . Examples of such copolymers include a tri-block copolymer of polymer block (A) -b-polymer block (B) -b-polymer block (A) and a tetra-block copolymer of polymer block (A) -fa- polymer block (B) -b-polymer block (A) -b-polymer block (B). Of these, a tri-block copolymer of polymer block (A) -b- polymer block (B) -b-polymer block (A) is more preferable from

the viewpoints of ease of preparation and little surface sticking.

[0028] The glass transition temperatures of the polymer block (A) and the polymer block (B) in the invention are extrapolated initial temperatures (Tgi) in the transition regions of the polymer block (A) and the polymer block (B) , which are observed in a curve obtained by DSC measurement of the acrylic block copolymer. As a specific measuring method, a method described in detail in the measuring items of the later-described working examples is adopted. On the basis of the curve obtained in the DSC measurement, plural glass transition temperatures derived from the polymer block (A) and the polymer block (B) are determined with regard to the acrylic block copolymer for use in the invention. The glass transition temperatures derived from the polymer block (A) and the polymer block (B) are temperatures equal or close to glass transition temperatures of polymers having the same chemical structures (monomer components, stereoregularity, etc.) as those of the polymer blocks, and therefore, which polymer blocks these plural glass transition temperatures are derived from respectively can be readily judged. The polymers having the same chemical structures as those of the polymer block (A) and the polymer block (B) can be readily prepared by analyzing the acrylic block copolymer through ¹ H-

NMR, ¹³ C-NMR, etc. to determine the chemical structures, such as monomer components and stereoregularity, of the polymer block (A) and the polymer block (B) and appropriately carrying out polymerization so that the chemical structures may be reproduced.

[0029] The molecular weight of the acrylic block copolymer is not specifically restricted, but from the viewpoint of moldability into the optical component of the invention, the weight-average molecular weight of the copolymer in terms of polystyrene, as determined by gel permeation chromatography (GPC) measurement, is in the range of preferably 10,000 to 500,000, more preferably 20,000 to 300,000.

[0030] Examples of molding methods to produce the optical component of the invention include melt extrusion, melt injection molding and solution casting, and in any of these molding methods, the weight-average molecular weight of the above range is preferable from the viewpoint of flowability in the molding process. [0031] The molecular weight distribution of the acrylic block copolymer is not specifically restricted, but from the viewpoints of surface sticking and transparency of the optical component of the invention, the value of weight- average molecular weight/number-average molecular weight is

in the range of preferably 1.01 to 2.20, more preferably 1.05 to 1.60. If the molecular weight distribution is more than the upper limit of the above range, a high-molecular weight component is increased and transparency is sometimes impaired, or a low-molecular weight component is increased and a defect of severe surface sticking sometimes occurs. If the molecular weight distribution is less than the lower limit of the above range, a compositional ratio of a low-molecular weight component having good influence on moldability or a high-molecular weight component favorably contributing to mechanical properties is lowered, and as a result, moldability is sometimes impaired, or mechanical properties necessary for the optical component are sometimes impaired. [0032] The acrylic block copolymer may have a functional group, such as hydroxyl group, carboxyl group, acid anhydride group, amino group or trimethoxysilyl group, in a molecular chain or at a molecular chain end, when necessary.

[0033] Since the optical component of the invention requires particularly excellent light transmission properties depending upon the use purpose, the acrylic block copolymer needs to be sufficiently transparent. Therefore, the total light transmittance of a sheet having a thickness of 3 mm

obtained from the acrylic block copolymer is preferably not less than 88%, more preferably not less than 90%.

[0034] The acrylic block copolymer preferably has the above-mentioned optical properties. In order to possess such optical properties, the acrylic block copolymer is required to have high purity. As a process for preparing such an acrylic block copolymer of high purity, a living polymerization process capable of highly controlling molecular structure is preferable. [0035] The living polymerization process is a process in which a monomer for a polymer block to constitute a block copolymer is polymerized and prior to deactivation or termination of this polymerization another polymer is polymerized to synthesize a block copolymer. Examples of such polymerization processes include a process comprising carrying out polymerization using an organic rare earth metal complex as a polymerization initiator (see patent document 9) , a process comprising carrying out anionic polymerization in the presence of a mineral acid salt such as a salt of an alkali metal or an alkaline earth metal using an organoalkali metal compound as a polymerization initiator (see patent document 10) , a process comprising carrying out anionic polymerization in the presence of an organoaluminum compound using an organoalkali metal compound as a polymerization

initiator (see patent document 11) , and an atom transfer radical polymerization process (ATRP) (see non-patent document 1) .

[0036] Of the above preparation processes, the process comprising carrying out anionic polymerization in the presence of an organoaluminum compound using an organoalkali metal compound as a polymerization initiator has the following advantages. Because of little deactivation in the course of polymerization, a homopolymer that is a deactivation component is introduced in a small amount, and as a result, the resulting acrylic block copolymer has high transparency. Further, because of high polymerization conversion of a monomer, the amount of a residual monomer in the manufactured article is small, and an odor is inhibited. Furthermore, when the monomer to constitute the polymer block (A) is a methacrylic ester, the molecular structure of the resulting polymer block becomes highly syndiotactic, and an effect of enhancing heat resistance is exerted. Moreover, living polymerization under relatively mild temperature conditions is feasible, and therefore, in the case of industrial production, there is an advantage of small environmental burden (low energy required for a refrigerator for mainly controlling polymerization temperature) . From the above viewpoints, the acrylic block copolymer is preferably

prepared by the process comprising carrying out anionic polymerization in the presence of an organoaluminum compound using an organoalkali metal compound as a polymerization initiator. [0037] In the anionic polymerization process in the presence of an organoaluminum compound, there are used, for example, an organolithium compound and a compound represented by the following formula (I) :

AlR ₁ R ₂ R ₃ (I) wherein R ₁ , R ₂ and R ₃ are each independently an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an N,N~di-substituted amino group which may have a substituent, or a halogen atom. Two of R ₁ , R ₂ and R ₃ may be bonded to each other to form an alkylene group which may have a substituent, an arylene group which may have a substituent, an arylenedialkyl group which may have a substituent, an alkylenedioxy group which may have a substituent, or an arylenedioxy group which may have a substituent .

[0038] As the organoalkali metal compound, an organolithium compound can be preferably employed. Examples

of the organolithium compounds include alkyllithiums or alkylenedilithiums, such as methyllithium, ethyllithium, n- propyllithium, isopropyllithium, n-butyllithium, sec- butyllithium, isobutyllithium, t-butyllithium, n- pentyllithium, n-hexyllithium, tetramethylenedilithium and pentamethylenedilithium and hexamethylenedilithium; aryllithiums or aryldilithiums, such as phenyllithium, iti- tolyllithium, p-tolyllithium, xylyllithium and lithium naphthalenide; aralkyllithiums or aralkyldilithiums, such as benzyllithium, diphenylmethyllithium, trityllithium, 1,1- diphenyl-3-methylpentyllithium, α-methylstyryllithium, and dilithium formed by the reaction of diisopropenylbenzene with butyllithium; lithium amides, such as lithium dimethylamide, lithium diethylamide and lithium diisopropylamide; and lithium alkoxides, such as methoxylithium, ethoxylithium, n- propoxylithium, isopropoxylithium, n-butoxylithium, sec- butoxylithium, t-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium and 4-methylbenzyloxylithium.

[0039] Of the above organoalkali metal compounds, t- butyllithium and see-butyllithium are preferable, and sec- butyllithium is more preferable, because the polymerization initiation efficiency is high.

Examples of the organoaluminum compounds represented by the above formula (I) include trialkylaluminums, such as trimethylaluminum, triethylaluminum, tri-n-butylaluminum, tri-see-butylaluminum, tri-t-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, tri-2-ethylhexylaluminum and triphenylaluminum; dialkylphenoxyaluminums, such as dimethyl (2, 6-di-tert- butylphenoxy) aluminum, dimethyl (2, 6-di-tert-butyl-4- methylphenoxy) aluminum, diethyl (2, 6-di-tert- butylphenoxy) aluminum, diethyl (2, 6-di-tert-butyl-4- methylphenoxy) aluminum, diisobutyl (2, 6-di-tert- butylphenoxy) aluminum and diisobutyl (2, β-di-tert-butyl-4- methylphenoxy) aluminum; alkyldiphenoxyaluminums, such as methylbis (2, 6-di-tert-butylphenoxy) aluminum, methylbis (2,6- di-tert-butyl-4-methylphenoxy) aluminum, methyl [2, 2' ~ methylenebis (4-methyl-6-tert-butylphenoxy) ] aluminum, ethylbis (2, 6-di-tert-butylphenoxy) aluminum, ethylbis (2, 6-di- tert-butyl-4-methylphenoxy) aluminum, ethyl [2,2'- methylenebis (4-methyl-6-tert-butylphenoxy) ] aluminum, isobutylbis (2, 6-di-tert-butylphenoxy) aluminum, isobutylbis (2, 6-di-tert-butyl-4-methylphenoxy) aluminum, isobutyl [2, 2' -methylenebis (4-methyl-6-tert- butylphenoxy) ] aluminum, n-octylbis (2, 6-di-tert- butylphenoxy) aluminum, n-octylbis (2, 6-di-tert-butyl-4-

methylphenoxy) aluminum and n-octyl [2, 2' -methylenebis (4- methyl-β-tert-butylphenoxy) ] aluminum; alkoxydiphenoxyaluminums, such as methoxybis (2, 6-di-tert- butylphenoxy) aluminum, methoxybis (2, 6-di-tert-butyl-4- methylphenoxy) aluminum, methoxy [2, 2' -methylenebis (4-methyl-6- tert-butylphenoxy) ] aluminum, ethoxybis (2, 6-di-tert- butylphenoxy) aluminum, ethoxybis (2, 6-di-tert-butyl-4- methylphenoxy) aluminum, ethoxy [2,2' -methylenebis (4-methyl-β- tert-butylphenoxy) ] aluminum, isopropoxybis (2, 6-di-tert- butylphenoxy) aluminum, isopropoxybis (2, 6-di-tert-butyl-4- methylphenoxy) aluminum, isopropoxy [2, 2' -methylenebis (4- methyl-6-tert-butylphenoxy) ] aluminum, tert-butoxybis (2, 6-di- tert-butylphenoxy) aluminum, tert-butoxybis (2, 6-di-tert-butyl- 4-methylphenoxy) aluminum and tert-butoxy [2, 2' -methylenebis (4- methyl-6-tert-butylphenoxy) ] aluminum; and triphenoxyaluminums, such as tris (2, 6-di-tert-butyl-4-methylphenoxy) aluminum and tris (2, β-diphenylphenoxy) aluminum.

[0040] Of the above organoaluminum compounds, isobutylbis (2, β-di-tert-butylphenoxy) aluminum, isobutylbis (2, β-di-tert-butyl-4-methylphenoxy) aluminum and isobutyl [2, 2' -methylenebis (4-methyl-β-tert- butylphenoxy) ] aluminum are preferable from the viewpoints of high living properties of the polymerization and ease of handling.

[0041] The polymerization to prepare the acrylic block copolymer may be carried out by allowing ethers, such as dimethyl ether, dimethoxyethane, diethoxyethane and 12- crown-4, and nitrogen-containing compounds, such as triethylamine, N, N, N' ,N' -tetramethylethylenediamine,

N, N, N' ,N",N"-pentamethyldiethylenetriamine, 1,1,4,7,10,10- hexamethyltriethylenetetramine, pyridine and 2, 2' -dipyridyl, to coexist in the reaction system, when necessary, in addition to the above organoaluminum compounds . [0042] The anionic polymerization is carried out usually in the presence of an inert solvent. Examples of the inert solvents include hydrocarbon solvents, such as benzene, toluene and xylene; halogenated hydrocarbon solvents, such as chloroform, methylene chloride and carbon tetrachloride; and ether solvents, such as tetrahydrofuran and diethyl ether. [0043] The process for preparing the acrylic block copolymer by anionic polymerization in the presence of an organoaluminum compound is illustrated more specifically. For example, the acrylic block copolymer can be prepared through 3 or more polymerization steps including a first step of polymerizing a monomer for forming the polymer block (A) , a second step of polymerizing a monomer for forming the polymer block (B) and a third step of polymerizing a monomer for forming the polymer block (A) , said polymerization in

each step being carried out in the presence of an organoaluminum compound using a polymerization initiator comprising an organoalkali metal compound.

[0044] In the above preparation process, at the end of a living polymer formed in each step, a desired polymer block is formed in the next step. Therefore, if the active end of the polymer obtained after polymerization of the above-mentioned continuous 3 steps is allowed to react with an alcohol or the like to terminate the polymerization reaction, a tri-block copolymer constituted of polymer block (A) -polymer block (B) -polymer block (A) can be prepared. A tetra- or higher block copolymer can be prepared by carrying out a step of polymerizing a monomer to form a desired polymer block (polymer block (A) , polymer block (B) or the like) desired times in addition to the above-mentioned 3 steps and then allowing the active end of the resulting polymer to react with an alcohol or the like to terminate the polymerization reaction.

[0045] The composition containing the acrylic block copolymer, which is used for the optical component of the invention, requires an elastic modulus enabling retention of shape of the optical component and flexibility when it is used for the optical component. On this account, the acrylic

block copolymer has a tensile modulus at 25 ⁰ C of preferably 100 MPa to 2500 MPa, more preferably 200 MPa to 2000 MPa.

[0046] In order to obtain an acrylic block copolymer having an elastic modulus of the above range, the compositional ratio of the polymer block (A) to the polymer block (B) (polymer block (A) /polymer block (B) ) in the acrylic block copolymer is in the range of 20/80 to 70/30, preferably 30/70 to 50/50. If the compositional ratio of polymer block (A) /polymer block (B) is less than the lower limit of the above range, tackiness becomes severe, and because of scratches and adhesion of dusts, surface properties are sometimes impaired. Further, retention of shape of the resulting optical component is deteriorated, and handling properties are sometimes lowered. If the compositional ratio of polymer block (A) /polymer block (B) is more than the upper limit of the above range, flexibility of the acrylic block copolymer tends to be not exhibited sufficiently.

[0047] In the composition used for the optical component of the invention, the acrylic block copolymer is contained as an essential component. In the composition, one kind of the acrylic block copolymer may be contained, or two or more kinds thereof may be contained.

[0048] Since the composition is used for the optical component of the invention, the acrylic block copolymer is preferably contained in a sufficient amount in the composition within limits not detrimental to the effect of the present invention. Although the content of the acrylic block copolymer in the composition is not specifically restricted, it is in the range of preferably 30% by weight to 100% by weight, more preferably 50% by weight to 100% by weight, based on the total weight of the composition. [0049] Since the composition is used for the optical component, it needs particularly excellent light transmission properties depending upon the use purpose. Therefore, the total light transmittance of a sheet having a thickness of 3 mm obtained from the composition is preferably not less than 88%, more preferably not less than 90%.

[0050] A preferred light transmittance of the composition can be appropriately determined according to the wavelength required for the practical use of an optical component produced from the composition. Typical examples of the wavelengths measured include near infrared rays (700 to 2,500 nm) , medium infrared rays (2,500 to 4,000 nm) , far infrared rays (4,000 to 1,000,000 nm) , visible rays (360 to 730 nm) , ultraviolet rays (10 to 400 nm) , far ultraviolet rays and laser beam.

[0051] When the composition is used for an optical component, the composition requires an elastic modulus enabling retention of shape of the optical component and flexibility. On this account, the composition containing the acrylic block copolymer has a tensile modulus at 25 ⁰ C of preferably 100 MPa to 2500 MPa, more preferably 200 MPa to 2000 MPa. If the tensile modulus at 25 ⁰ C is more than the upper limit of the above range, bending processability and flexural properties are poor because of shortage of flexibility, so that such a tensile modulus is undesirable. Contrary to this, if the tensile modulus is less than the lower limit of the above range, sticking or blocking occurs when the composition is molded into an optical component, and the optical component suffers inconvenient handling depending upon the use purpose.

[0052] The elastic modulus of the optical component of the invention can be appropriately selected according to the use purpose. For example, when the optical component is used in the form of a film, a tube, a rod or the like, a tensile modulus at 25°C of 500 MPa to 2000 MPa can be selected, and when the optical component is used as a component having cushioning properties or elastomeric properties in addition to the optical properties, a tensile modulus at 25°C of 100 MPa to 500 MPa can be selected. When

the optical component of the invention is used as a sealing component or an adhesive component, a tensile modulus at 25°C of 10 MPa to 100 MPa can be selected.

[0053] In the composition, other polymers, such as resin and rubber, and additives, such as softener, lubricant, plasticizer, adhesive, tackifier, heat stabilizer, antioxidant, light stabilizer, antistatic agent, flame retardant, blowing agent, colorant, dye and filler, may be further contained within limits not detrimental to the effect of the present invention. In the composition, these other polymers and additives may be contained singly or in combination of two or more kinds .

[0054] Examples of the other polymers include acrylic block copolymers other than the acrylic block copolymers used in the invention.

Examples of the resins include acrylic resins, such as polymethyl methacrylate and methacrylic ester copolymer; olefin-based resins, such as polyethylene, ethylene/vinyl acetate copolymer, polypropylene, poly-1-butene, poly-4- methyl-1-pentene and polynorbornene; ethylene-based ionomers; styrene-based resins, such as polystyrene, styrene/maleic anhydride copolymer, high-impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin and MBS resin; methyl methacrylate/styrene copolymer; polyester resins, such as

polyethylene terephthalate, polybutylene terephthalate and polylactic acid; polyamides, such as nylon 6, nylon 66 and polyamide elastomer; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene/vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, and silicone rubber modified resin. Of these resins, acrylic resin, ethylene/vinyl acetate copolymer, AS resin, polylactic acid and polyvinylidene fluoride are preferably used from the viewpoint of compatibility with the acrylic block copolymer contained in the composition.

[0055] Examples of the rubbers include acrylic rubbers; silicone-based rubbers; styrene-based TPE (thermoplastic elastomers) , such as SEPS, SEBS and SIS; and olefin-based rubbers, such as IR, EPR and EPDM.

[0056] Examples of the softeners include mineral oils, such as paraffinic oil and naphthenic oil. When such a softener is contained in the composition, flowability of the composition in the molding process is improved. Examples of the fillers include inorganic fibers, such as glass fiber and carbon fiber; organic fibers; and inorganic fillers, such as calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate and magnesium carbonate. When the inorganic fiber or the organic

fiber is contained in the composition, reinforcing effect is given to the resulting optical component. When the inorganic filler is contained in the composition, heat resistance and weathering resistance are given to the resulting optical component .

[0057] When the heat stabilizer or the antioxidant is contained in the composition, heat resistance and weathering resistance are further improved, and therefore, such an additive is preferably contained in the composition from the viewpoint of practical use.

These other polymers and additives may be added when the composition is molded to produce an optical component.

[0058] The optical component of the invention can be produced by molding the above-mentioned composition. The optical component of the invention can be applied to general optical uses, but because of its excellent light resistance and transparency, it is preferably used as an optical component having such a light transmitting function that the light which has been emitted from a light source and entered the component is transmitted by the component and goes outside the component. The light source is not specifically restricted, and examples of the light sources include sunlight, natural light, incandescent lamp, fluorescent lamp, cold-cathode tube, ultraviolet light, neon

tube and organic/inorganic light emitting diode (LED) . Since the acrylic block copolymer used for the optical component of the invention is excellent in light transmittance particularly in the ultraviolet range, it can be particularly preferably used for an optical component of an optical element using ultraviolet light and LED as a light source.

[0059] Since the composition used for the optical component of the invention has excellent melt processability, it can be readily molded into various forms according to the use purpose. The method to mold the composition into the optical component of the invention is not specifically restricted as long as an optical component in a desired form can be produced by molding the composition.

[0060] Examples of the forms of the optical component include a film, a sheet, a tube, a column, a cone and a cone frustum. In the forms of a tube and a column, forms of a rod and a fiber can be also included. In the optical components in the form of a film, a component whose main part is in the form of a film can be also included. The same shall apply also to the optical components in the forms of a sheet, a tube, a column, a cone and a cone frustum. Further, in the forms of a column, a cone and a cone frustum, forms of nearly a column, nearly a cone and nearly a cone frustum, such as forms of a capsule and a bullet, can be also included.

Although the outside of the optical component is typically in the above form, the inside thereof may be hollow or solid depending upon the use purpose.

[0061] When the optical component of the invention is in the form of a film or a sheet, the optical component can be produced by, for example, melt extrusion method or solution casting method.

As the melt extrusion method, a general method used for producing a component in the form of a film or a sheet is employable. Specifically, a method using a die, an inflation method or the like is employable, and a method using a die is preferable because this method is superior in productivity and accuracy of thickness.

[0062] When a component in the form of a film or a sheet is produced by the melt extrusion method using a die, the component can be produced by, for example, melting the composition containing the acrylic block copolymer in an extruder, extruding the composition into a sheet or a film from a die installed on the extruder and taking off the extruded sheet or film with adhering to at least one cooling roll.

[0063] The die is not specifically restricted, and examples of the dies include publicly known dies, such as T- die and coat hanger type die. The material of the die is,

for example, steel of SCM type or stainless steel such as SUS, but the material is not limited thereto.

[0064] As the solution casting method, a general method used for producing a component in the form of a film or a sheet is employable. Specifically, there can be mentioned, for example, a method in which a heat-resistant material such as polyethylene terephthalate, a flat plate or a roll such as a steel belt, is used as a substrate, and a solution containing the above composition is cast on the substrate by the use of a bar coater, a roll coater, a die coater, a comma coater or the like and dried to remove the solvent .

[0065] The method to remove the solvent by drying is not specifically restricted, and a method hitherto publicly known is employable. However, it is preferable to carry out drying in plural stages. When the drying is carried out in plural stages, it is more preferable that drying in the first stage is carried out at a relatively low temperature in order to inhibit foaming caused by rapid evaporation of the solvent, and drying in the second or later stage is carried out at a high temperature in order to sufficiently remove the solvent.

[0066] In the solution casting method, the solvent used for dissolving the composition containing the acrylic block copolymer is not specifically restricted as long as it

is a solvent capable of dissolving the composition, and examples of such solvents include toluene, ethyl acetate, ethylbenzene, methylene chloride, chloroform, THF, methyl ethyl ketone, DMSO, and a toluene-ethanol mixed solvent. Of these, toluene, ethylbenzene, ethyl acetate and methyl ethyl ketone are preferable.

[0067] The concentration of the solvent in the solution is appropriately determined taking into account solubility of the composition in the solvent, viscosity of the resulting solution, etc., but a preferred lower limit is 5% by weight, and a preferred upper limit is 50% by weight.

[0068] When the optical component of the invention is in the form of a tube, a column, a cone or a cone frustum, the optical component can be produced by, for example, melt extrusion method or melt injection molding method.

As the melt extrusion method, a general method used for producing a component in the form of a tube, a column, a cone or a cone frustum is employable.

[0069] Specifically, the component in the form of a tube, a column, a cone or a cone frustum can be produced by a melt extrusion method using a die. In the case of production by the melt extrusion method using a die, the component in the form of a tube, a column, a cone or a cone frustum can be produced by, for example, melting the composition containing

the acrylic block copolymer in an extruder, then extruding the molten composition into a desired form from a die installed on the extruder and if necessary cutting the extrudate. [0070] As the melt injection molding method, a general method used for producing a component in the form of a tube, a column, a cone or a cone frustum is employable. Specifically, the component can be produced by, for example, melting the composition containing the acrylic block copolymer in an injection molding machine and injecting the molten composition in a mold of a desired shape.

[0071] Although the aforesaid forms of a sheet, a film, a tube, a column, a cone, a cone frustum, etc. are typical examples of the forms of the optical components of the invention, other forms can be also taken depending upon the use purpose. When the optical component of the invention takes other forms, the optical component can be produced by the aforesaid molding method publicly known, such as melt extrusion, melt injection molding or solution casting, or by combining these molding methods.

[0072] The optical component of the invention may be provided with patterns depending upon the use purpose, or the surface of the optical component may have been subjected to surface treatment. Examples of the surface treatments

include corona treatment, plasma treatment, ultraviolet ray- irradiation treatment, electron ray irradiation treatment, ion bombardment treatment, heat treatment under vacuum, antifouling treatment, antistatic treatment and antireflection treatment.

[0073] The surface of the optical component of the invention may be provided with a dielectric layer, a transparent conductive layer, etc.

As the dielectric to constitute the dielectric layer, a transparent material is usually used, and the dielectric layer is formed by the use of an oxide of a metal, such as Si, Al, Ti, Zr, In or Sn, as a raw material. Metals of such metal oxides may be used singly or in combination of two or more kinds. When two or more metals are combined, there can be used, for example, combinations of Zr and Ti, Al and Zr, In and Sn, etc. The dielectric layer is usually transparent, and above all, a colorless transparent layer is preferable. The dielectric layer can be produced by a physical vapor deposition (PVD) method, such as deposition, sputtering or ion plating, and from the viewpoint of productivity, deposition, particularly electron beam deposition, is preferable.

[0074] The transparent conductive layer is produced by the use of a metal, such as Sn, In, Ti, Pb, Au, Pt or Ag,

an oxide of such a metal, carbon or carbon nanotube, as a raw material. For example, the transparent conductive layer can be produced by forming a layer of such a single metal on the surface of the optical component and if necessary oxidizing the single metal layer. Further, the transparent conductive layer may be produced by depositing such a metal oxide itself on the surface of the optical component. Moreover, the transparent conductive layer may be produced by forming a single metal layer or a lower oxide layer first and then subjecting the layer to oxidation treatment such as thermal oxidation, anodizing or liquid phase oxidation.

[0075] Although the optical component of the invention can be applied to general optical uses, it basically has excellent light transmitting function because it is excellent in light resistance and transparency, and for example, by adding other components to the composition used for the optical component or by giving a desired form to the optical component in the molding process, other optical functions can be given to the optical component. The "optical function" in the invention means a function of giving a change to the light incident on the optical component from a light source, and examples of such functions include a reflecting function to reflect at least a part of light, a light absorption function to absorb at least a part

of light and a phase difference function to give phase difference to the incident light.

[0076] Since the optical component of the invention is excellent in flexibility, light resistance and transparency, it can be used for various purposes.

In the case where the optical component of the invention is in the form of a film or a sheet, examples of such optical components include a polarizing film, a polarizing plate, a retardation film, a field angle enlarging film, a luminance enhancing film, an anti-reflecting film, an antiglare film, a color filter, a light guide plate, a light diffusion film, a semi-transmission reflecting film, a prism sheet, an electromagnetic wave shield film, a near infrared ray absorbing film, a plate applied to UV nano imprint, and a combined functional optical film having plural optical functions combined.

[0077] Films composed of a thermoplastic resin and used for a device that treats polarized light, such as a liquid crystal display device, are required to be optically transparent and to have not only small birefringence but also optical homogeneity. On this account, in the case of polarizer protective films of polarizing plates, film substrates for plastic liquid crystal display devices using resin films instead of glass substrates, etc., it is

requested that the phase difference represented by the product of birefringence and thickness should be small and the phase difference of the film should be hardly changed by external stress, deformation or the like. That is to say, if the phase difference is large or the phase difference is changed by external stress, deformation or the like, a problem of markedly lowering image quality of the liquid crystal display device occurs. For example, troubles, such as a color skip phenomenon that the color is partially lightened and distortion of image, take place.

The optical component of the invention has excellent transparency and flexibility, and in addition, it is excellent in optical homogeneity because the phase difference is small and the phase difference of a film is hardly changed by external stress, deformation or the like. Therefore, the optical component of the invention can be favorably used as an optical component for a liquid display device, particularly for a flexible display that is used while it is bent under application of a stress. [0078] Further, by subjecting the optical component of the invention to stretch treatment to give a phase difference function to the component, a retardation film can be produced. The method of stretch treatment is not specifically restricted, and a method hitherto publicly known

is employable. For example, stretch treatment methods, such as monoaxial stretching, simultaneous biaxial stretching and successive biaxial stretching, are employable.

[0079] Because of the properties of the retardation film that the phase difference of the film is hardly changed by external stress, deformation or the like, the phase difference function of the film is hardly changed by external stress, deformation or the like, and therefore, the retardation film can be favorably used for a liquid crystal display device. In particular, it can be favorably used as an optical component for a flexible display that is used while it is bent under application of a stress.

[0080] If the retardation film produced by stretch treatment of the optical component of the invention is laminated on a polarizing plate with an adhesive or is directly laminated onto a polarizer, the resulting film can be used as a polarizer protective film also having a function of a retardation film.

[0081] The retardation of the retardation film is appropriately adjusted according to the use purpose. When the retardation film is used for, for example, a twisted nematic (TN) liquid crystal display device, the retardation is in the range of usually about 20 to 300 nm; when the retardation film is used for a super twisted nematic (STN)

liquid crystal display device, the retardation is in the range of usually about 150 to 2000 nm; when the retardation film is used for a vertically aligned (VA) liquid crystal display device, the retardation is in the range of usually about 0 to 200 nm; and when the retardation film is used for an optically compensated bend (OCB) liquid crystal display device, the retardation is in the range of usually about 20 to 200 nm. Further, the retardation film can be also used as a λ/4 plate or a λ/2 plate that is used in a composite polarizing plate such as a circularly polarizing plate or an elliptically polarizing plate. When the retardation film is used as a λ/4 plate, the retardation of the film is in the range of usually about 100 to 200 nm; and when the retardation film is used as a λ/2 plate, the retardation of the film is in the range of usually about 200 to 300 nm.

[0082] Also the ratio (R ₄₀ /R ₀ ) of a retardation (R ₄₀ ) measured when the retardation axis is inclined as an inclination axis by 40° from the vertical direction to a retardation (Ro) measured from the vertical direction to the plane of the retardation film is appropriately adjusted according to the use purpose. For example, when the retardation film is used for a TN liquid crystal display device, the ratio (R40/R0) is in the range of usually about 0.9 to 1.5; when the retardation film is used as a λ/4 plate

or a λ/2 plate, the ratio (R4 ₀ /R0) is in the range of usually about 0.9 to 1.5; and when the retardation film is used for a STN liquid crystal display device, the ratio (R40/R0) is in the range of usually about 0.9 to 1.1. When the retardation film is used for a VA liquid crystal display device or an OBC liquid crystal display device, the ratio (R40/R0) is usually not less than 1..0, and the upper limit is not specifically restricted, and R ₀ may be 0. Although the thickness of the retardation film is appropriately adjusted according to the use purpose, it is in the range of usually about 30 to 300 μm.

[0083] When the optical component of the invention is used as a luminance enhancing film, it is enough to produce a film wherein particles are dispersed so that anisotropy of reflectance may occur by virtue of refractive index anisotropy, a film wherein inorganic particles are dispersed so that anisotropy of reflectance may occur based on a difference in scattering power due to size, or the like.

[0084] When the optical component of the invention is used as a light diffusion film, the light diffusion film can be produced by adding a light diffusing agent having a refractive index different from that of a composition used for the optical component to the composition and molding the mixture into a film.

[0085] A difference δnD (i.e., I nD (c) - (nD (a) | ) between the refractive index (nD(c)) of the light diffusing agent and the refractive index (nD(a)) of the composition is preferably not less than 0.005, more preferably not less than 0.01. The δnD is preferably not more than 0.3. If the difference δnD in refractive index exceeds 0.3, the total light transmittance tends to be lowered, and if it is less than the above value, the diffusivity tends to be lowered. The light diffusing agent is not specifically restricted as long as it is transparent and preferably satisfies the above conditions of the refractive index, but from the viewpoint of obtaining more excellent light diffusion effect, transparent particles are preferably employed. Examples of the transparent particles include various inorganic particles and organic particles.

[0086] Examples of the inorganic particles include silica particles, alumina particles, silica alumina particles, talc, barium carbonate particles and metal particles. Examples of the organic particles include silicone resin particles, acrylic resin particles, nylon resin particles, urethane resin particles, styrene resin particles, polyethylene resin particles and polyester resin particles. As the transparent particles, further, particles in each of which a thin film composed of a metal oxide, such as silicon

oxide, zinc oxide, titanium oxide or zirconium oxide, or a thin film composed of a metal fluoride such as MgF ₂ , is formed on a surface of a core of glass, metal, synthetic resin or the like are also employable. [0087] Although the particle diameters of these particles are not specifically restricted, the mean particle diameter is in the range of usually about 0.5 μm to 30 μm, preferably 1 μm to 20 μm, more preferably 1 μm to 15 μm. If the mean particle diameter is less than the lower limit of the above range, light diffusion properties are enhanced, but light transmission properties tend to be lowered. If the mean particle diameter is more than the upper limit of the above range, light transmission properties are enhanced, but light diffusion properties tend to be lowered and nonuniformity of luminance tends to occur.

[0088] The shape of the transparent particle that is preferably used as the light diffusing agent is preferably spherical. When the spherical particle is used as the light diffusing agent, such a spherical particle acts as a kind of a lens, so that more effective light diffusion effect is obtained. The term "spherical" used herein means a shape having a miner axis/major axis ratio of a fine particle of preferably not less than 0.6, more preferably not less than 0.8, particularly preferably not less than 0.9, and having no

corner. The "minor axis" means a smallest diameter of one particle, and the "major axis" means a largest diameter of the same particle. The proportion of the spherical particles contained in the transparent particles used herein is preferably not less than 80%, more preferably not less than 90%, particularly preferably not less than 95%. The minor axis, the major axis, presence of corner and the mean particle diameter of the particle are measured on the basis of an image of a microphotograph. If there are a large number of non-spherical particles, dispersing is made nonuniformly in the molding process, or it becomes difficult to obtain a molded article which has orientation properties and uniform light diffusion properties. The light diffusing agents for the light diffusion film may be used singly or may be used in combination of plural kinds.

[0089] The light transmission properties and the light diffusion properties of the light diffusion film can be controlled by, for example, adding appropriate amounts of plural kinds of the light diffusing agents to the composition. When the optical component of the invention is used as a semi-transmission reflecting film, the semi-transmission reflecting film can be produced by, for example, dispersing pearl mica particles or the like in a composition used for

the optical component of the invention and molding the composition into a film.

[0090] When the optical component of the invention is used as an electromagnetic wave shield film, the electromagnetic wave shield film can be produced by a method of laminating a transparent conductive film on at least one surface of a film, a method of laminating a conductive net material on at least one surface of a film, a method of embedding a conductive net material inside a film to unite them, or the like.

[0091] The transparent conductive film can be produced by, for example, vacuum depositing or sputtering a metal, a metal oxide or the like, or coating the optical component with a resin solution in which fine particles having conductivity such as metal fine particles or metal oxide fine particles are dispersed. Examples of the metals include silver, platinum, palladium, copper, titanium, chromium, molybdenum, nickel and zirconium. Of these, silver is preferable because a conductive layer having excellent conductivity is readily obtained. In the case where the metal layer is provided as the conductive layer, it is preferable to form a multilayer film consisting of this metal layer and a dielectric layer in order to prevent reflection of the metal layer. Examples of the dielectric layers

include layers composed of various metal oxides, metal nitrides and metal sulfides. Examples of the metal oxides include silicon oxide, titanium oxide, tantalum oxide, tin oxide, indium oxide, zirconium oxide, zinc oxide, and a composite oxide of indium oxide and tin oxide.

[0092] These metals and metal oxides may be used singly, or may be used in combination of two or more kinds. Examples of the methods to laminate the conductive net material include a method of laminating a metal net material or a resin conductive mesh whose surface has been coated with a metal layer, a method of printing a lattice pattern on a surface of a transparent resin plate using a conductive ink or the like, and a method comprising providing a thin film of a metal such as copper or aluminum on a film surface and then forming a lattice pattern by means of etching or the like.

[0093] Examples of fibers to constitute the conductive mesh include copper fiber, stainless steel fiber, and synthetic fiber such as polyester fiber whose surface has been coated with a layer of a metal such as gold, silver or copper. The diameter of the fiber to constitute a net of the conductive mesh is in the range of usually 10 to 60 μm, and the mesh size is in the range of preferably 40 to 200 meshes. The mesh size is a size defined by a Tyler standard sieve. In order to prevent metallic luster, the surface of such a

conductive mesh may be colored black with a conductive coating material or by plating or the like.

[0094] The electromagnetic wave shield film obtained as above can be used for, for example, shielding electromagnetic waves emitted from a front face of a plasma display.

When the optical component of the invention is used as a near infrared absorbing film, this film can be produced by dispersing a near infrared absorbing dye, typically a near infrared absorbing dye which has high visible light transmittance and absorbs light of near infrared region much, such as diimonium-based near infrared absorbing agent, aminium-based near infrared absorbing agent, anthraquinone- based near infrared absorbing agent, phthalocyanine-based near infrared absorbing agent, particularly fluorine- containing phthalocyanine-based near infrared absorbing agent, nickel complex-based near infrared absorbing agent, polymethine-based near infrared absorbing agent, diphenylmethane-based near infrared absorbing agent, triphenylmethane-based near infrared absorbing agent or cyanine-based near infrared absorbing agent, in a composition used for the optical component of the invention and molding the composition into a film.

[0095] The near infrared absorbing film obtained as above can be used for, for example, shielding near infrared rays released based on luminescence of an inert gas in a cell of a plasma display. [0096] The optical component of the invention can be used as a light guide plate. Although the light guide plate is basically in the form of a sheet or a film, it may be in the form of a block or a rod, or in a bent shape, a curved shape or another publicly known shape. At least one surface of the light guide plate may be provided with dots by screen printing, or a surface of the light guide plate may be provided with a linear pattern such as a V groove, a semi- spherical lens-like concavity or convexity, or an embossed pattern. Although the thickness of the light guide plate is appropriately adjusted according to the use purpose, it is in the range of usually 0.01 mm to 10 mm from the viewpoint of securing moldability and strength in practical use and the viewpoint of weight reduction.

[0097] At least one surface of the light guide plate may have been subjected to light reflection treatment, light diffusion treatment or light condensing treatment. These light reflection treatment, light diffusion treatment and light condensing treatment are carried out by publicly known techniques. In general, one surface of the light guide plate

is subjected to light reflection treatment, and a surface opposite to the surface having been subjected to the light reflection treatment is subjected to light diffusion treatment or light condensing treatment. The light reflection treatment, the light diffusion treatment or the light condensing treatment may be carried out by bonding a light reflecting sheet, a light diffusion sheet or a light condensing sheet on a surface of the light guide plate.

[0098] Although the light guide plate can be produced by the aforesaid melt extrusion method, it can be produced by- other publicly known methods, such as melt injection molding, hot pressing and cutting. Of these, melt extrusion, melt injection molding and hot pressing are preferable from the viewpoint of productivity. [0099] By combining the thus obtained light guide plate with a light source, a light diffusion sheet, a light reflecting sheet and a transmission type display element, an image display device can be produced. In this image display, the light source is arranged so as to face the side end surface of the light guide plate, the light reflecting sheet is arranged on one surface side of the light guide plate, and on the opposite surface, the light diffusion sheet is arranged. The transmission type display element is arranged on the front of the light exit surface of the light guide

plate where the light diffusion sheet is arranged. By virtue of such arrangement, the light from the light source is lead into the light guide through the side end surface of the light guide, the light having passed inside the light guide is effectively diffused by the light diffusion sheet and goes outside, and then the transmission type display element is irradiated with the light. A typical example of the transmission type display element is a liquid crystal panel. Examples of such image display devices include television and personal computer monitor. The light guide can be also used for an optical element such as an image display device having different constitution.

[0100] In the case where the optical component of the invention is in the form of a tube, a column, a cone or a cone frustum, an example of the optical component is an optical fiber used for a light guide, a photoelectric sensor or the like.

[0101] When the optical component of the invention is used as the optical fiber, the optical fiber can be produced by melting a composition used for the optical component of the invention, spinning the molten composition from a nozzle and if necessary stretching it by a take-off roller or the like. When the composition used for the optical component of the invention is used for one layer of the optical fiber, the

optical fiber can be produced by replacing the nozzle with a nozzle for composite spinning and carrying out spinning together with other molten resins in the same manner as above.

[0102] The optical fiber obtained as above can be used as a usual plastic optical fiber by further coating the surface of the optical fiber with a coating material.

Further, the optical fiber obtained as above can be used for, for example, a light guide in which the optical fiber is allowed to undergo surface luminescence by arranging a light source such as LED at the end of the optical fiber without providing a coating layer on the optical fiber. Since the optical component of the invention is rich in flexibility, it is possible to arrange the optical fiber while being bent, so that the optical fiber can be efficiently used for, for example, a light emitting device consisting of this optical fiber and a light source by replacing an electric bulb or a fluorescent lamp used in an internal illumination type display device such as a traffic signal machine with the optical fiber. [0103] Moreover, the optical component of the invention can be used as a micro lens, a lens sheet or the like. When the optical component of the invention is used as the lens sheet or the micro lens in the form of a sheet, such a lens sheet or a micro lens can be produced by forming a

sheet from a composition used for the optical component of the invention through melt extrusion or the like and hot pressing the sheet using a press plate engraved with a shape of a lens. [0104] The optical component of the invention is particularly excellent in light transmittance in the ultraviolet region, and therefore, it can be particularly preferably used as an optical component of an optical element using LED as a light source. Examples of such optical components include the aforesaid light guide for LED, an LED lamp cover and a component for an LED display device.

[0105] In addition, the optical component of the invention can be applied to every optical use irrespective of shape, etc., by taking advantage of its excellent flexibility, light resistance and transparency. For example, the optical component of the invention can be used for various mobile communication keys of cell phones and the like, illuminated keys used as various terminal keys of electronic notebooks and the like, touch panel, VDT filter, PDP front plate, projection television front plate, image display face plate of CRT, optical disc, cover material of automobile auxiliary lamp, head lamp, tail lamp or the like, display component provided on automobile side mirror, component for automobile instrument panel, sun visor, component for luminescent room

mirror, lenses used for spectacle, sunglass, camera, telescope, microscope and projection television, prism, mirror, illumination plate, signboard, window glass, and illumination apparatus.

EXAMPLES

[0106] The present invention is further described with reference to the following examples, but it should be construed that the invention is in no way limited to those examples. Various properties in the examples and the comparative examples were measured or evaluated in the following manner . (1) Weight-average molecular weight (Mw)

Weight-average molecular weights (Mw) of an acrylic block copolymer and an acrylic resin were determined as weights in terms of polystyrene by means of gel permeation chromatography (abbreviated to GPC hereinafter) .

Apparatus: GPC apparatus "HLC-8020" manufactured by Tosoh Corporation Separation column: "TSKgel GMHXL", "G400OHXL" and

"G5000HXL" available from Tosoh Corporation were connected in series .

Eluent: tetrahydrofuran

Flow rare of eluent: 1.0 ml/min

Column temperature: 40 ⁰ C

Detection method: differential refractive index (RI) (2) Compositional ratio of polymer block

The compositional ratio of each polymer block to acrylic polymer blocks was determined by ¹ H-NMR ( ¹ H-nuclear magnetic resonance) measurement.

Apparatus: nuclear magnetic resonance apparatus "JNM- LA400" manufactured by JEOL Ltd.

Heavy solvent: deuterated chloroform (3) Glass transition temperature (Tg) of polymer block

An extrapolated initial temperature (Tgi) in a curve obtained by DSC measurement using a DSC measuring device (DSC-822) manufactured by Mettler Co. under the conditions of a heating rate of 10°C/min was regarded as a glass transition temperature (Tg) . (4) Transparency

Using a composition containing an acrylic block copolymer obtained in each of the following examples and comparative examples, a molded product having a length of 5 cm, a width of 5 cm and a thickness of 3 mm was prepared by an injection molding machine at a given cylinder temperature and a given mold temperature. Then, a haze value of the molded product was measured by a direct reading haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.) in

accordance with JIS K7136, and a total light transmittance of the molded product was measured in accordance with JIS K7361. (5) Flexibility (tensile modulus)

A composition containing an acrylic block copolymer obtained in each of the following examples and comparative examples was molded by a press molding machine at a given temperature to prepare a test specimen having a thickness of 1 mm. Then, tensile dynamic viscoelasticity of the test specimen was measured, and elastic modulus (E') at 25°C was measured.

Apparatus: wide-area dynamic viscoelasticity measuring apparatus (forced oscillation, non-resonant method) , "PVE-V4 FT Rheospectler" manufactured by Rheology Co., Ltd.

Measuring frequency: 11 Hz Measuring mode: tensile test

Measuring temperature: 25 ⁰ C

Strain: 0.03%

Sample: in the form of strip (pressed sheet) of 20 mm (length) x 5 mm (width) x 1 mm (thickness) (6) Flex resistance (film)

A composition containing an acrylic block copolymer obtained in each of the following examples and comparative examples was molded into a molded product in the form of a sheet having a thickness of 0.1 mm by the use of a T-die

extruder at a cylinder temperature of 220 ⁰ C and a die temperature of 220 ⁰ C. Then, occurrence of a crack of the molded product when the molded product was bent was evaluated.

AA: A crack did not occur. cracked: A crack occurred. (7) Punchability (film)

A composition containing an acrylic block copolymer obtained in each of the following examples and comparative examples was molded into a molded product in the form of a sheet having a thickness of 0.1 mm by the use of a T-die extruder at a given cylinder temperature and a given die temperature. From the molded product, a test specimen was punched by a JIS No. 3 punching blade to observe the test specimen. AA: Punchability was good. cracked: The test specimen suffered a crack.

[0107] (8) Light guide properties

Using a composition containing an acrylic block copolymer obtained in each of the following examples and comparative examples, a molded test specimen was prepared by the use of injection molding machine NADEM5000 manufactured by Meiki Co., Ltd. The test specimen was in the form of a flat plate light guide having a size of 200 mm (length) * 270 mm (width) x 4.0 mm (thickness), as shown in Fig. 1. In the

mold, a gate having a size of a width of 40 mm and a thickness of 3.8 mm was provided at the center of the transverse side. The gate of light guide molded by injection was cut by a heat nipper or a saw blade to obtain a test specimen. The molding was carried out under the molding conditions of a resin temperature of 250 ⁰ C, a mold temperature of 60 ⁰ C, an injection time of 4 sec, a holding pressure of 300 MPa, a holding pressure time of 10 sec and a cooling time of 60 sec. On the resulting molded product, a reflecting pattern layer was printed by screen printing, and its luminance was measured by a color luminance meter BM-7 manufactured by Topcon Corporation. Specifically, each luminance at 9 points in a plane of the light guide was measured at a height of 50 cm and at an angle of field of 2°, as shown in Fig. 2, and a mean luminance and a uniformity ratio of luminance (minimum luminance/maximum luminance at 9 points) were evaluated. In the measurement, two light sources were arranged, as shown in Fig. 3, and the measurement was carried out at a luminance of 37000 cd/m ² of the cold-cathode tube and using two sheets of D124 (available from Tsujiden Co., Ltd.) as diffusion sheets or one sheet of E60L (available from Toray Industries, Inc.) as a reflecting sheet.

[0108] In the following synthesis examples, compounds having been dried and purified in conventional ways and having been deaerated by the use of nitrogen were used. Further, transfer and feed of compounds were carried out in a nitrogen atmosphere. Reference Example 1

Preparation of organoaluminum compound (isobutylbis (2, 6-di-t- butyl-4-methylphenoxy) aluminum

In a flask having an internal volume of 200 ml, which had been purged with argon as an internal atmosphere, 25 ml of dry toluene obtained by drying toluene over sodium and then distilling it in an argon atmosphere and 11 g of 2,6-di- t-butyl-4-methylphenol were placed, and they were stirred at room temperature to give a solution. To the resulting solution, 6.8 ml of triisobutylaluminum was added, and they were stirred at 80 ⁰ C for about 18 hours to prepare a toluene solution containing the corresponding organoaluminum compound (isobutylbis (2, β-di-t-butyl-4-methylphenoxy) aluminum) in a concentration of 0.6 mol/1.

[0109] Reference Example 2 Synthesis of acrylic block copolymer (Al)

A 2-liter three-neck flask was equipped with a three-way cock, and the inside was deaerated and purged with nitrogen.

Thereafter, 1040 g of dry toluene, 100 g of 1,2- dimethoxyethane and 48 g of the toluene solution containing 32 mmol of isobutylbis (2, 6-di-t-butyl-4- methylphenoxy) aluminum obtained in Reference Example 1 were placed at room temperature, and then 8.1 mmol of sec- butyllithium was further added. To the mixture, 72 g of methyl methacrylate was added, and they were reacted at room temperature for 1 hour. Thereafter, 0.1 g of the reaction solution was withdrawn. This solution was regarded as a test sample 1. Subsequently, the internal temperature of the polymerization solution was lowered to -25°C, and 307 g of n- butyl acrylate was dropwise added over a period of 2 hours. After the dropwise addition was completed, 0.1 g of the reaction solution was withdrawn. This solution was regarded as a test sample 2. Subsequently, 72 g of methyl methacrylate was added, then the temperature of the reaction solution was returned to room temperature, and the solution was stirred for 8 hours. To the reaction solution was added 4 g of methanol to terminate the polymerization. The reaction solution obtained after termination of the reaction was poured into a large amount of methanol to obtain a precipitate. This precipitate was regarded as a test sample 3. The test samples 1 to 3 were subjected to ¹ H-NMR measurement and GPC measurement, and on the basis of the

results, Mw (weight-average molecular weight) , Mw/Mn (molecular weight distribution) , ratios by mass of methyl methacrylate polymer (PMMA) block and n-butyl acrylate polymer (PnBA) block, etc. were determined. As a result, the precipitate finally obtained was a tri-block copolymer of

PMMA block-PnBA block-PMMA block (PMMA-b-PnBA-b-PMMA) . Mw of the PMMA block was 9,900, and Mw/Mn thereof was 1.08. Mw of the whole of the tri-block copolymer was 62,000, and Mw/Mn thereof was 1.19. The ratios of the polymer blocks were PMMA (16% by mass) -PnBA (68% by mass) -PMMA (16% by mass) .

[0110] Reference Example 3 Synthesis of acrylic block copolymer (A2)

The same procedure as in Reference Example 2 was carried out to synthesize a tri-block copolymer (A2) having a molecular weight and a copolymerization compositional ratio different from those of the copolymer of Reference Example 2. Mw of the whole of the tri-block copolymer obtained was 62,000, and Mw/Mn thereof was 1.11. The proportion of the PMMA block in the tri-block copolymer was 50% by mass.

[0111] Reference Example 4 Synthesis of acrylic block copolymer (A3)

The same procedure as in Reference Example 2 was carried out to synthesize a tri-block copolymer (A3) having a molecular weight and a copolymerization compositional ratio different from those of the copolymer of Reference Example 2. Mw of the whole of the tri-block copolymer obtained was

118,000, and Mw/Mn thereof was 1.20. The proportion of the PMMA block in the tri-block copolymer was 23.0% by mass.

[0112] Examples 1 to 5, Comparative Examples 1 and 2 The acrylic block copolymers (Al) to (A3) prepared in Reference Examples 2 to 4 and the following resins were evaluated under the aforesaid conditions (4) to (8) . The results are set forth in Table 1.

PMMA resin (1) : Parapet GF, available from Kuraray Co., Ltd.

PMMA resin (2) : Parapet GH-1000S, available from Kuraray Co. , Ltd.

Non-yellowed TPU resin: XN-2002, available from Nippon Polyurethane Industry Co., Ltd. In Examples 4 and 5, pellets of a thermoplastic polymer composition were prepared by melt kneading the components in the blending ratio shown in Table 1 using a twin-screw extruder at 230 ⁰ C, then extruding the kneadate and cutting

the extrudate. Then, the pellets were evaluated under the above conditions. [0113]

Table 1

OJ

[0114] From the results shown in Table 1, it can be seen that the optical component using the acrylic block copolymer not only was excellent in transparency and light guide properties but also had properties compatible with flex resistance and punchability because of excellent flexibility, as shown in Examples 1 to 3. Further, it can be seen that the optical component using plural acrylic block copolymers exhibited excellent light guide properties, as shown in Example 4. Furthermore, even in the optical component obtained from the composition of the acrylic block copolymer and the PMMA resin, transparency was not impaired, as shown in Example 5. On the other hand, the optical component obtained from the PMMA resin (2) in Comparative Example 1 exhibited excellent light guide properties, but because the acrylic block copolymer was not contained, the optical component was rigid and inferior in flex resistance and punchability. The optical component obtained from the non- yellowed TPU resin in Comparative Example 2 was excellent in flex resistance and punchability, but it was insufficient in transparency, particularly in light guide properties.