JP5666989B2 - Optical film and image display device - Google Patents

Description

  The present invention relates to a resin composition containing a (meth) acrylic polymer and a cellulose ester polymer, an optical film and a retardation film composed of the resin composition, and an image display device including the retardation film.

  Conventionally, cellulosic polymers and (meth) acrylic polymers have been used in optical films including polarizer protective films and retardation films. Patent Document 1 describes a retardation film using a (meth) acrylic polymer having a ring structure in the main chain.

  In Patent Document 2, a (meth) acrylic polymer having a ring structure in the main chain is useful as a modifier for a cellulose ester film, and a (meth) acrylic polymer having a ring structure in the main chain is used as a cellulose ester film. In addition, it is described that the horse's spine failure and deformation failure of the film represented by the core transfer are suppressed, and that an example of the cellulose ester film is a retardation film.

Japanese Patent Laid-Open No. 2008-9378 JP 2009-1744

  When a resin composition containing a (meth) acrylic polymer and a cellulose ester polymer is molded, the haze ratio of the surface increases, and the transparency of the resulting molded product often decreases. In particular, this tendency is remarkable when the resin composition is formed into a film. Films with reduced transparency cannot be used as optical films.

  The present invention is a resin composition comprising a (meth) acrylic polymer and a cellulose ester polymer, and a decrease in transparency associated with an increase in haze ratio during molding, particularly during molding into a film, is suppressed. An object of the present invention is to provide a resin composition, and an optical film and a retardation film that are made of the resin composition and are excellent in transparency.

The optical film of the present invention is an optical film comprising a resin composition, and the glass transition temperature of the optical film is 110 ° C. or higher, and the resin composition comprises (meth) acrylic polymer (A) and cellulose ester. and a polymer (B), wherein the (meth) acrylic polymer (a), which has shown in the following formula (1) and (meth) acrylic acid alkyl ester units and methyl methacrylate units as constituent units, The main chain has a ring structure having an ester group, an imide group or an acid anhydride group, and the (meth) acrylic polymer (A) has a weight average molecular weight of 80,000 or more.

In the formula (1), R ¹ is an alkyl group having 2 to 18 carbon atoms, and R ² is H or CH ₃ .

The image display device of the present invention includes the optical film of the present invention which is a retardation film .

  According to the present invention, there is provided a resin composition comprising a (meth) acrylic polymer and a cellulose ester polymer, in which a decrease in transparency associated with an increase in haze ratio during molding, particularly during molding into a film, is suppressed. Realize. From the resin composition, for example, the optical film of the present invention excellent in transparency and the retardation film of the present invention excellent in transparency can be obtained.

[(Meth) acrylic polymer (A)]
The (meth) acrylic polymer contains (meth) acrylic acid ester units in an amount of 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, A polymer having 99% by weight or more is preferable. The (meth) acrylic polymer may have a ring structure that is a derivative of the (meth) acrylic acid ester unit in the main chain, and in this case, the total of the (meth) acrylic acid ester unit and the ring structure is entirely composed. If it is 50 weight% or more of a unit, it will become a (meth) acrylic polymer.

  (Meth) acrylic acid ester units are, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t- (meth) acrylic acid t- Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acryl Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2, 3,4,5,6-pentahydroxyhexyl, 2,3,4,5-tetrahydro (meth) acrylic acid Cypentyl, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, normal butyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) acrylic It is a structural unit formed by polymerization of monomers such as t-butyl acid. The (meth) acrylic polymer may have two or more of these structural units. From the viewpoint of heat resistance and transparency of a resin composition and a molded product obtained by molding the resin composition, the (meth) acrylic polymer (A) has a methyl methacrylate (MMA) unit as a constituent unit. Is preferred.

  The (meth) acrylic polymer (A) contained in the resin composition of the present invention has a (meth) acrylic acid alkyl ester unit X represented by the following formula (1) as a constituent unit.

In the formula (1), R ¹ is an alkyl group having 2 to 18 carbon atoms, and R ² is H (hydrogen atom) or CH ₃ (methyl group). When R ² is H, the unit shown in Formula (1) is an acrylic acid alkyl ester unit, and when R ² is CH ₃ , the unit shown in Formula (1) is a methacrylic acid alkyl ester unit.

R ¹ is not limited as long as it is an alkyl group having 2 to 18 carbon atoms. R ¹ is, for example, an ethyl group (carbon number 2), a propyl group (carbon number 3), a butyl group (carbon number 4), a pentyl group (carbon number 5), a hexyl group (carbon number 6), a heptyl group (carbon 7), octyl group (carbon number 8), nonyl group (carbon number 9), decyl group (carbon number 10), undecyl group (carbon number 11) and dodecyl group (carbon number 12) and their structural isomers. is there.

The proportion of the (meth) acrylic acid alkyl ester unit X in all the structural units of the (meth) acrylic polymer (A) varies depending on the specific molecular structure of the unit X, but is, for example, 5% by weight or more. The proportion is preferably 10% by weight or more, more preferably 15% by weight or more, since the effect of the present invention can be obtained more reliably. As long as the effect of the present invention is obtained, the upper limit of the ratio is not particularly limited, and is 50% by weight, for example. The proportion of the (meth) acrylic acid alkyl ester unit X in the total structural units of the (meth) acrylic polymer (A) can be determined by ¹ H nuclear magnetic resonance ( ¹ H-NMR) or infrared spectroscopic analysis (IR). it can. In addition, the ratio of each monomer used for the polymerization of the (meth) acrylic polymer (A) and, if necessary, the reaction mechanism from the monomer to the (meth) acrylic polymer (A). It can also be obtained by reference.

  The (meth) acrylic polymer (A) may have two or more (meth) acrylic acid alkyl ester units X as constituent units.

  The (meth) acrylic polymer (A) may have a structural unit other than the (meth) acrylic acid ester unit. The structural unit includes, for example, (meth) acrylic acid, styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, It is a structural unit formed by polymerization of monomers such as propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone and N-vinyl carbazole. .

  The (meth) acrylic polymer (A) preferably has (meth) acrylic acid alkyl ester units X, MMA units and 2- (hydroxymethyl) acrylic acid ester units as constituent units. The (meth) acrylic polymer (A) preferably has (meth) acrylic acid alkyl ester units X, MMA units, 2- (hydroxymethyl) acrylic acid ester units and N-vinylcarbazole units as constituent units. . In these cases, an increase in haze ratio is further suppressed, and high optical characteristics can be obtained when an optical film is obtained. In these cases, the content of the MMA unit in the (meth) acrylic polymer (A) is preferably 10 to 80% by weight, and more preferably 20 to 60% by weight. The content of 2- (hydroxymethyl) acrylic acid ester units is preferably 10 to 60% by weight, and more preferably 20 to 40% by weight. The content of the unit X is preferably 5 to 70% by weight, and more preferably 10 to 50% by weight. The content of the N-vinylcarbazole unit is preferably 1 to 20% by weight, and more preferably 3 to 8% by weight. The 2- (hydroxymethyl) acrylic acid ester unit is, for example, a 2- (hydroxymethyl) methyl acrylate (MHMA) unit, a 2- (hydroxymethyl) ethyl acrylate unit, a 2- (hydroxymethyl) acrylic acid isopropyl unit, These are normal butyl units of 2- (hydroxymethyl) acrylate and t-butyl units of 2- (hydroxymethyl) acrylate. Of these, MHMA units and 2- (hydroxymethyl) ethyl acrylate units are preferred, and MHMA units are particularly preferred from the viewpoint of transparency and heat resistance of the optical film.

  The (meth) acrylic polymer (A) may have a ring structure in the main chain. In this case, the increase in haze rate is further suppressed. Further, the glass transition temperature (Tg) of the (meth) acrylic polymer (A) having a ring structure in the main chain is high, for example, 110 ° C. or higher, and depending on the configuration of the polymer, 120 ° C. or higher, and further 130 ° C. or higher. is there. By including the (meth) acrylic polymer (A) having a high Tg as described above, the heat resistance of the resin composition of the present invention and a molded body comprising the resin composition, for example, the optical film and the retardation film of the present invention. Improves. Optical films with high heat resistance, such as retardation films, can be placed near heat-generating parts such as light sources and are therefore suitable for use in image display devices such as liquid crystal display devices (LCD). .

  In addition, the fact that the (meth) acrylic polymer (A) has a ring structure in the main chain improves the optical properties of the optical film comprising the resin composition of the present invention, such as a large in-plane retardation. Contribute.

  When the (meth) acrylic polymer (A) has a ring structure in the main chain, the content of the ring structure in the polymer (A) is preferably 25 to 90% by weight, more preferably 35 to 90% by weight, Particularly preferred is 40 to 90% by weight. When the content rate of the ring structure in a polymer (A) exceeds 90 weight%, the moldability of the resin composition containing a polymer (A) may fall.

  The ring structure that the (meth) acrylic polymer (A) may have in the main chain is, for example, a ring structure having an ester group, an imide group, or an acid anhydride group.

  A more specific example of the ring structure is at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure.

  The ring structure is preferably at least one selected from a lactone ring structure and a glutarimide structure, and more preferably a lactone ring structure. The (meth) acrylic polymer (A) having a lactone ring structure in the main chain has particularly high compatibility with the cellulose ester polymer (B). When both compatibility is high, the fall of the transparency at the time of shape | molding the resin composition of this invention is further suppressed.

  The specific lactone ring structure that the (meth) acrylic polymer (A) may have in the main chain is not particularly limited, and may be, for example, a 4- to 8-membered ring. It is preferably a 5-membered or 6-membered ring, more preferably a 6-membered ring. The lactone ring structure which is a 6-membered ring is a structure disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-168882. High polymerization yield of the precursor (a (meth) acrylic polymer (A) having a lactone ring structure in the main chain is obtained by subjecting the precursor to a cyclization condensation reaction), a cyclization condensation reaction of the precursor From the reasons such that a (meth) acrylic polymer (A) having a high lactone ring content can be obtained and a polymer having a MMA unit as a constituent unit can be used as a precursor, the following formula (2) The structure shown is preferred.

In the formula (2), R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The organic residue is, for example, an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, or a propyl group; an unsaturated aliphatic carbonization having 1 to 20 carbon atoms such as an ethenyl group or a propenyl group. A hydrogen group; an aromatic hydrocarbon group having 1 to 20 carbon atoms such as a phenyl group or a naphthyl group; one of hydrogen atoms in the alkyl group, the unsaturated aliphatic hydrocarbon group and the aromatic hydrocarbon group; One or more groups are substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group and an ester group.

The lactone ring structure represented by the formula (2) is adjacent to each other in the obtained copolymer after copolymerization of a monomer group including, for example, MMA and methyl 2- (hydroxymethyl) acrylate (MHMA). It can be formed by dealcoholization cyclocondensation of MMA units and MHMA units. At this time, R ³ is H, and R ⁴ and R ⁵ are CH ₃ .

  When the (meth) acrylic polymer (A) has a lactone ring structure in the main chain, the content of the lactone ring structure in the polymer (A) is the cellulose ester polymer (B), particularly the cellulose acetate polymer, From the viewpoint of compatibility, the content is preferably 25 to 70% by weight, more preferably 30 to 60% by weight. The content of the lactone ring structure in the (meth) acrylic polymer (A) can be determined by the method described in JP-A-2001-151814.

  The weight average molecular weight (Mw) of the (meth) acrylic polymer (A) is preferably 80,000 or more, and more preferably 100,000 or more. The molecular weight dispersity (= weight average molecular weight Mw / number average molecular weight Mn) in the (meth) acrylic polymer (A) is preferably 3.5 or less, and more preferably 3 or less. The Mw and dispersity of the (meth) acrylic polymer (A) can be determined by gel permeation chromatography (GPC). When the (meth) acrylic polymer (A) satisfies the above Mw and dispersion ranges, the branched structure of the polymer (A) is suppressed. This contributes to the improvement of thermal stability during processing of the resin composition of the present invention and the formation of an optical film having high strength and a desirable appearance.

  The (meth) acrylic polymer (A) can be produced by a known method. The same applies to the (meth) acrylic polymer (A) having a ring structure in the main chain. The (meth) acrylic polymer (A) having a glutaric anhydride structure or a glutarimide structure in the main chain can be produced, for example, by the method described in WO2007 / 26659 or WO2005 / 108438. The (meth) acrylic polymer (A) having a maleic anhydride structure or an N-substituted maleimide structure in the main chain is produced, for example, by the method described in JP-A-57-153008 and JP-A-2007-31537. it can. The (meth) acrylic polymer (A) having a lactone ring structure in the main chain is produced, for example, by the method described in JP-A-2006-96960, JP-A-2006-171464, or JP-A-2007-63541. it can.

  As an example, a method for producing a (meth) acrylic polymer (A) having a lactone ring structure in the main chain will be described. The polymer (A) has a hydroxyl group and an ester group in the molecular chain, and the polymer (a) having a (meth) acrylic acid alkyl ester unit X as a constituent unit is heated in the presence of an arbitrary catalyst, It can be obtained by proceeding with a lactone cyclization condensation reaction involving dealcoholization.

  The polymer (a) can be formed, for example, by polymerization of a monomer group including a monomer represented by the following formula (3) and a monomer represented by the following formula (4).

In the formula (3), R ⁶ and R ⁷ are each independently a group exemplified as a hydrogen atom or an organic residue in the formula (2). The monomer represented by the formula (3) gives a hydroxyl group and an ester group in the molecular chain of the polymer (a) by polymerization.

In the formula (4), R ⁸ is the same group as R ^{1 in the} formula (1). In the formula (4), R ⁹ is H (hydrogen atom) or CH ₃ (methyl group). The monomer ((meth) acrylic acid alkyl ester monomer Y) represented by the formula (4) becomes a (meth) acrylic acid alkyl ester unit X by polymerization.

  Specific examples of the monomer represented by the formula (3) are methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- (hydroxy Methyl) normal butyl acrylate, 2- (hydroxymethyl) acrylate t-butyl. Of these, methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferred, and methyl 2- (hydroxymethyl) acrylate (MHMA) is particularly preferred from the viewpoints of transparency and heat resistance.

  Specific examples of the monomer represented by the formula (4) include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and hexyl (meth) acrylate. , Heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, and dodecyl (meth) acrylate.

  In the monomer group used for forming the polymer (a), the content of the monomer represented by the formulas (3) and (4) is adjusted according to the molecular structure of the desired (meth) acrylic polymer (A). it can.

  The monomer group used for forming the polymer (a) may contain two or more monomers represented by the formula (3), and may comprise two or more monomers represented by the formula (4).

  The monomer group used for forming the polymer (a) may include monomers other than the monomers represented by the formulas (3) and (4). Such a monomer is not particularly limited as long as it is a monomer copolymerizable with the monomers represented by formulas (3) and (4). The said monomer is (meth) acrylic acid ester other than the monomer shown to Formula (3), (4), for example.

  Examples of the (meth) acrylic acid ester include acrylic acid esters such as methyl acrylate, cyclohexyl acrylate, and benzyl acrylate; and methacrylic acid esters such as methyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. From the viewpoint of transparency and heat resistance, MMA is preferred.

  The monomer group used for forming the polymer (a) may contain two or more of these (meth) acrylic acid esters.

  The monomer group used for forming the polymer (a) includes monomers such as (meth) acrylic acid, styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, You may contain 1 type, or 2 or more types. However, the content of (meth) acrylic acid in the monomer group is preferably 30% by weight or less, more preferably 20% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less. When the content of (meth) acrylic acid exceeds 30% by weight, gelation may proceed in the polymerization process of the monomer group.

  When forming the polymer (a) by polymerization of the monomer group, a polymerization initiator may be used as necessary. Examples of the polymerization initiator include cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, and t-amyl peroxy-2- Organic peroxides such as ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2,4-dimethylvaleronitrile) ), Dimethyl 2,2′-azobisisobutyrate; Two or more polymerization initiators can be used in combination. The usage-amount of a polymerization initiator can be suitably set according to the combination of the monomer contained in a monomer group, and polymerization conditions.

  It is preferable to use a known cyclization catalyst for the lactone cyclization condensation reaction involving dealcoholization of the polymer (a). The cyclization catalyst is, for example, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid. Organic carboxylic acids such as acetic acid, propionic acid, benzoic acid, acrylic acid, and methacrylic acid can also be used as the cyclization catalyst. Further, as disclosed in, for example, JP-A-61-254608 and JP-A-61-261303, a basic compound; an organic carboxylate such as zinc acetate; a carbonate is used as a cyclization catalyst. You can also

  The cyclization catalyst may be an organophosphorus compound. The organophosphorus compound includes, for example, alkylphosphonic acid or arylphosphonous acid such as methylphosphonous acid, ethylphosphonous acid, and phenylphosphonous acid (however, these are alkyl phosphinic acid or aryl which are tautomers) As well as monoesters or diesters thereof; dialkylphosphinic acids such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid, diarylphosphinic acids or alkylaryls Phosphinic acids and their esters; alkyl phosphonic acids or aryl phosphonic acids such as methyl phosphonic acid, ethyl phosphonic acid, trifluoromethyl phosphonic acid, phenyl phosphonic acid and Monoesters or diesters thereof; alkylphosphinic acid or arylphosphinic acid such as methylphosphinic acid, ethylphosphinic acid, phenylphosphinic acid, and esters thereof; methylphosphite, ethylphosphite, phosphorous acid Phosphorous acid monoesters, diesters or triesters such as phenyl, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, phosphorus Ethyl acetate, 2-ethylhexyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, octyl phosphate, Diisodecyl phosphate, dilauryl phosphate Phosphoric acids such as distearyl phosphate, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate Monoester, diester or triester; mono-, di- or trialkyl (aryl) phosphine such as methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine ; Methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, diphenylchlorophosphine Alkyl (aryl) halogen phosphines such as: methyl phosphine oxide, ethyl phosphine oxide, phenyl phosphine oxide, dimethyl phosphine oxide, diethyl phosphine oxide, diphenyl phosphine oxide, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide mono- Di- or tri-alkyl (aryl) phosphines; tetraalkyl phosphonium halides such as tetramethylphosphonium chloride, tetraethylphosphonium chloride, tetraphenylphosphonium chloride; Two or more of these organophosphorus compounds may be used in combination. Among them, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester, and alkyl (aryl) phosphonic acid are preferable because of high catalytic activity and low colorability. ) Phosphorous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester are more preferred, and alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester is particularly preferred.

  It is also possible to use a basic cyclization catalyst. The cyclization catalyst is, for example, a group 12 element compound described in JP-A-2009-144112, and a zinc compound is particularly preferable. Examples of the zinc compound include organic zinc compounds such as zinc acetate, zinc propionate, and zinc octylate; inorganic zinc compounds such as zinc oxide, zinc chloride, and zinc sulfate; organic zinc compounds containing fluorine such as zinc trifluoromethanesulfonate; It is.

  When a resin composition containing the obtained (meth) acrylic polymer (A) is molded by an unreacted reactive group remaining after a lactone cyclization condensation reaction, foaming or cross-linking between the polymers may occur. May occur. This phenomenon can be suppressed by adding a cyclization catalyst deactivator after the cyclization condensation reaction. The addition of the deactivator is also effective for suppressing deterioration of the cellulose ester polymer (B) contained in the resin composition. An acidic substance or a basic substance is often used for the cyclization catalyst. When the cyclization catalyst is an acidic substance, it is preferable to use a basic deactivator. When the cyclization catalyst is a basic substance, it is preferable to use an acidic deactivator. The basic deactivator is, for example, a metal carboxylate, a metal complex, or a metal oxide, preferably a metal carboxylate or metal oxide, and more preferably a metal carboxylate. The metal used for the deactivator is not limited as long as it does not inhibit the physical properties of the resin composition. For example, alkali metals such as lithium, sodium and potassium; alkaline earth metals such as magnesium, calcium, strontium and barium; Zinc; zirconium. The carboxylic acid constituting the metal carboxylate is, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid. Acid, behenic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, lactic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, and adipic acid. An organic component in the metal complex is, for example, acetylacetone. Examples of the metal oxide include zinc oxide, calcium oxide, and magnesium oxide, and zinc oxide is preferable. Acidic deactivators are, for example, organic phosphoric acid compounds and carboxylic acids. Two or more quenchers can be used in combination. The form of the quenching agent is not limited, and it may be in the form of a solid, powder, dispersion, suspension, aqueous solution or the like.

[Cellulose ester polymer (B)]
The cellulose ester polymer (B) is not limited, and examples thereof include a cellulose aromatic carboxylic acid ester polymer and a cellulose fatty acid ester polymer. Since an optical film having excellent optical properties can be obtained, the cellulose polymer (B) is preferably a cellulose lower fatty acid ester polymer. A lower fatty acid means a fatty acid having 5 or less carbon atoms. The cellulose lower fatty acid ester polymer is, for example, cellulose acetate, cellulose propionate, cellulose butyrate, or cellulose pivalate. The cellulose ester polymer (B) may be a cellulose mixed fatty acid ester polymer such as cellulose acetate propionate or cellulose acetate butyrate. In this case, the film forming property of the resin composition of the present invention and the composition It is possible to achieve compatibility with mechanical properties in a molded article made of a product, such as the optical film of the present invention. From the viewpoint of compatibility with the (meth) acrylic polymer (A), the cellulose ester polymer (B) is preferably cellulose acetate, particularly cellulose triacetate or cellulose acetate propionate.

  The Mn of the cellulose ester polymer (B) is preferably 50,000 to 150,000, more preferably 55,000 to 120,000, and still more preferably 60,000 to 100,000. The Mw of the cellulose ester polymer (B) is preferably 100,000 to 300,000, more preferably 100,000 to 250,000, and further preferably 120,000 to 200,000. The molecular weight dispersity (= Mw / Mn) in the cellulose ester polymer (B) is preferably 1.3 to 5.5, more preferably 1.5 to 5.0, and further preferably 1.7 to 4.0. 2.0 to 3.5 is preferable and particularly preferable.

  The cellulose ester polymer (B) can be produced by a known method. For example, it can be produced by substituting the hydroxyl group of the raw material cellulose with an acetyl group, a propionyl group and / or a butyl group by a conventional method using acetic anhydride, propionic anhydride and / or butyric anhydride. In that case, the methods described in JP-A-10-45804 and JP-A-6-501040 are helpful. The raw material cellulose is not particularly limited, and examples thereof include wood pulp and cotton linter. The wood pulp may be softwood pulp or hardwood pulp, but softwood pulp is preferred. From the viewpoint of releasability when forming a film, a cotton linter is preferred. The resin composition of the present invention may contain two or more cellulose ester polymers (B).

[Resin composition]
The content rates of the (meth) acrylic polymer (A) and the cellulose ester polymer (B) in the resin composition of the present invention are not particularly limited. The resin composition of the present invention contains, for example, 20 to 95% by weight of (meth) acrylic polymer (A) and 5 to 80% by weight of cellulose ester polymer (B), preferably (meth) acrylic polymer ( A) 30 to 90% by weight and cellulose ester polymer (B) 10 to 70% by weight, more preferably (meth) acrylic polymer (A) 40 to 85% by weight and cellulose ester polymer (B) 15 Up to 60% by weight.

  The content of the (meth) acrylic polymer (A) in the resin composition of the present invention is preferably 30% by weight or more, more preferably 40% by weight or more, and further preferably 50% by weight or more.

  Patent Document 2 does not describe how much a (meth) acrylic polymer having a ring structure in the main chain should be added to the cellulose ester film as a modifier. Only the example which added 4-12 weight part of the said (meth) acrylic polymer to the cellulose ester 100 weight part in the Example is described.

  When these ranges relating to the contents of the (meth) acrylic polymer (A) and the cellulose ester polymer (B) are satisfied, a resin composition in which a decrease in transparency associated with an increase in the haze ratio during molding is suppressed, and Not only can an optical film excellent in transparency be obtained, but also the moisture permeability and photoelastic coefficient of the optical film are lower than those of an optical film made of a cellulose ester polymer. Moreover, depending on the kind and content range of the (meth) acrylic polymer (A) and the cellulose ester polymer (B), a retardation film having a high degree of freedom in controlling the wavelength dispersion of the retardation can be obtained.

  The resin composition of the present invention may contain two or more (meth) acrylic polymers (A) and / or two or more cellulose ester polymers (B).

  As long as the effect of the present invention is obtained, the resin composition of the present invention has a polymer other than the (meth) acrylic polymer (A) and the cellulose ester polymer (B) as the content in the resin composition. It may be contained in the range of not more than wt%, preferably not more than 10 wt%.

  Examples of the polymer include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins; polystyrene, Styrene polymers such as styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; nylon 6, nylon 66, polyamides such as nylon 610, polyacetal, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyether ether ketone, polyether nitrile, polysulfone, poly Polyether sulfone; a; polyoxyethylene Penji alkylene; polyamideimide.

  Among these polymers, vinyl cyanide monomer has a good compatibility with (meth) acrylic polymer (A), particularly (meth) acrylic polymer (A) having a lactone ring structure in the main chain. A copolymer containing a structural unit derived from a body and a structural unit derived from an aromatic vinyl monomer, such as a styrene-acrylonitrile copolymer, is preferred.

  As long as the effect of this invention is acquired, the resin composition of this invention may contain arbitrary materials. The material includes, for example, an ultraviolet absorber; an antioxidant; a stabilizer such as a light stabilizer, a weather stabilizer and a heat stabilizer; a reinforcing material such as a glass fiber and a carbon fiber; a near infrared absorber; and tris (dibromopropyl). Flame retardants such as phosphate, triallyl phosphate and antimony oxide; antistatic agents represented by anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers Resin modifiers; anti-blocking agents; matting agents; acid scavengers; metal deactivators; plasticizers; lubricants; rubber masses such as ASA and ABS. The content rate of these materials in the resin composition of this invention is 0 to 5 weight%, for example, Preferably it is 0 to 2 weight%, More preferably, it is 0 to 0.5 weight%.

  Ultraviolet absorbers are, for example, benzophenone compounds, salicinate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n- Octyloxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1,4-bis (4-benzoyl-3-hydroxyphenone) -butane. The silicate compound is, for example, pt-butylphenyl silicate. The benzoate compound is, for example, 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate. Triazole compounds include, for example, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3 5-Di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl)- 4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-t-butylphenol, 2- [5-chloro (2H) -benzotriazole-2 -Yl] -4-methyl-6- (t-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-t-butylphenol, 2- (2H-ben Triazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5, 6-tetrahydrophthalimidylmethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction product, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3 , 5-Bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-benzotriazol-2-yl) -5- ( , 1-dimethylethyl) -4-hydroxy -C7-9 side chain and straight-chain alkyl ester. Examples of triazine compounds include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-ethoxy). Phenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-butoxy) Phenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy) -4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, , 4-Diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3 , 5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3,5-triazine, 2,4-bis [2-hydroxy-4-butoxyphenyl] -6 (2,4-dibutoxyphenyl) -1,3-5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-alkyloxy-2-hydroxy) Propyloxy) -5-α-cumylphenyl] -s-triazine and alkyloxy, for example, long-chain alkyloxy such as octyloxy, nonyloxy, decyloxy, etc. And a compound having a group. “Tinuvin 1577”, “Tinuvin 460”, and “Tinuvin 477” (all manufactured by Ciba Specialty Chemicals) are commercially available as triazine-based UV absorbers, and “Adeka Stub LA-31” (Asahi Denka Kogyo Co., Ltd.) as a triazole-based UV absorber. Manufactured) is commercially available.

  The resin composition of the present invention may contain two or more kinds of ultraviolet absorbers. When the resin composition of this invention contains a ultraviolet absorber, the content rate of the ultraviolet absorber in the said resin composition is not specifically limited. In the state of the optical film, the content is preferably 0.01 to 25% by weight, more preferably 0.05 to 10% by weight. If the content of the ultraviolet absorber is excessively large, the mechanical properties of the finally obtained molded body (optical film) may be deteriorated, or the molded body (optical film) may be yellowed.

  Antioxidants are, for example, hindered phenol compounds, phosphorus compounds and sulfur compounds. The resin composition of the present invention may contain two or more kinds of antioxidants.

  The antioxidant may be a phenolic compound, such as n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, n-octadecyl-3- (3,5- Di-t-butyl-4-hydroxyphenyl) acetate, n-octadecyl-3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl-3,5-di-t-butyl-4-hydroxyphenyl Benzoate, n-dodecyl-3,5-di-t-butyl-4-hydroxyphenylbenzoate, neododecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl-β- (3 , 5-Di-t-butyl-4-hydroxyphenyl) propionate, ethyl-α- (4-hydroxy-3,5-di-t-butylphenyl) ) Isobutyrate, octadecyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl-α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate 2- (2-hydroxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol Bis- (3,5-di-tert-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate , Stearamide-N, N-bis- [ethylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene-3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl-3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyl) Oxyethylthio) ethyl-7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], neopentyl glycol Bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1- n-octadecanoate-2,3-bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), pentaerythritol tetrakis- [3- (3 ′, 5′-di-t-butyl) -4'-hydroxyphenyl) propionate], 1,1,1-trimethylolethanetris- [3- (3,5-di-tert-butyl-4- Roxyphenyl) propionate], sorbitol hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl-7- (3-methyl-5-t-butyl-4 -Hydroxyphenyl) propionate, 2-stearoyloxyethyl-7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol bis [(3 ', 5'-di -T-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate), 3,9-bis [1,1-dimethyl-2- [ β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] -2,4,8,1 - tetraoxaspiro [5,5] - undecanoic.

  It is preferable to use an antioxidant (phenolic antioxidant) composed of a phenolic compound in combination with a thioether antioxidant or a phosphoric acid antioxidant. The content of both antioxidants in the resin composition of the present invention is, for example, 0. 0 for each of the phenol-based antioxidant and the thioether-based antioxidant based on the weight of the (meth) acrylic polymer (A). 01% by weight or more, and each of the phenolic antioxidant and the phosphoric acid antioxidant is 0.025% by weight or more.

  Examples of the thioether-based antioxidant include pentaerythrityl tetrakis (3-lauryl thiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl- 3,3′-thiodipropionate.

  Examples of the phosphoric acid antioxidant include tris (2,4-di-t-butylphenyl) phosphite, 2-[[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d. , F] [1,3,2] dioxaphosphin-6-yl] oxy] -N, N-bis [2-[[2,4,8,10-tetrakis (1,1 dimethylethyl) dibenzo [D, f] [1,3,2] dioxaphosphin-6-yl] oxy] -ethyl] ethanamine, diphenyltridecyl phosphite, triphenyl phosphite, 2,2-methylenebis (4,6- Di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite DOO, cyclic neopentanetetraylbis (2,6-di -t- butyl-4-methylphenyl) is phosphite.

  The content of the antioxidant in the resin composition of the present invention is not particularly limited, and is, for example, 0 to 10% by weight, preferably 0 to 5% by weight, more preferably 0.01 to 2% by weight. Yes, most preferably 0.05 to 1% by weight. When the content of the antioxidant is excessively large, the antioxidant may bleed out or silver streaks may occur when the resin composition of the present invention is molded by melt extrusion.

  The resin composition of the present invention can be molded into various shapes depending on the application. The shape of the molded body obtained by molding the resin composition of the present invention is, for example, a film, a sheet, a plate, a disk, a block, a ball, a lens, a rod, a strand, a cord, and a fiber. The molding method of the resin composition of the present invention is not particularly limited, and a known molding method can be applied.

  Since a molded product, particularly a film, in which a decrease in transparency due to an increase in haze rate is suppressed, a resin composition of the present invention is used for optical purposes, specifically, an optical lens, an optical prism, an optical film. It is suitable for applications such as optical fibers and optical disks, and particularly suitable for optical films including retardation films.

[Optical film]
The optical film of the present invention comprises the above-described resin composition of the present invention.

  The optical film of the present invention has a small haze ratio and excellent transparency. The haze ratio of the optical film of the present invention is, for example, 5% or less as measured at a thickness of 50 μm, measured according to JIS K7165. Types of (meth) acrylic polymer (A) and cellulose ester polymer (B) included in the optical film of the present invention (included in the resin composition of the present invention), (meth) acrylic polymer in the optical film of the present invention ( Depending on the content of A) and the cellulose ester polymer (B), and the molding method of the optical film of the present invention from the resin composition, the haze value is 4% or less, 3.5% or less, 3% or less, Furthermore, it becomes 1% or less.

In the optical film of the present invention, the absolute value of the photoelastic coefficient for light having a wavelength of 590 nm is, for example, 5 × 10 ⁻¹² Pa ⁻¹ or less. Types of (meth) acrylic polymer (A) and cellulose ester polymer (B) contained in the optical film of the present invention, and (meth) acrylic polymer (A) and cellulose ester polymer (B in the optical film of the present invention) ), The absolute value is 4 × 10 ⁻¹² Pa ⁻¹ or less, and further 3 × 10 ⁻¹² Pa ⁻¹ or less.

The moisture permeability per 100 μm thickness in the optical film of the present invention is, for example, 200 g / m ² · 24 hours or less as a value measured in accordance with JIS Z0208. Types of (meth) acrylic polymer (A) and cellulose ester polymer (B) contained in the optical film of the present invention, and (meth) acrylic polymer (A) and cellulose ester polymer (B in the optical film of the present invention) ), The value is 150 g / m ² · 24 hours or less, 130 g / m ² · 24 hours or less, and further 120 g / m ² · 24 hours or less.

  When the optical film of the present invention contains a (meth) acrylic polymer (A) having a ring structure in the main chain, the optical film exhibits high heat resistance based on the (meth) acrylic polymer (A), and its Tg Is, for example, 110 ° C. or higher. Kinds of the (meth) acrylic polymer (A) and cellulose ester polymer (B) contained in the optical film of the present invention, and the (meth) acrylic polymer (A) and cellulose ester polymer in the optical film of the present invention Depending on the content of (B), Tg is 120 ° C. or higher, 125 ° C. or higher, and further 130 ° C. or higher.

  The thickness of the optical film of the present invention is not particularly limited, and is, for example, 10 to 500 μm, preferably 20 to 300 μm, and particularly preferably 30 to 100 μm.

  The total light transmittance of the optical film of the present invention is preferably 85% or more, more preferably 90% or more, and still more preferably 91% or more as a value measured according to JIS K7361-1.

  The use of the optical film of the present invention is not particularly limited, and can be used for the same use as a conventional optical film. The optical film of the present invention is, for example, an optical protective film, specifically, a protective film for various optical disk (VD, CD, DVD, MD, LD, etc.) substrates, and an image display device such as a liquid crystal display (LCD). It can be used as a polarizer protective film used for a polarizing plate provided in. The optical film of the present invention is a retardation film, a viewing angle compensation film, a light diffusion film, a reflection film, an antireflection film, an antiglare film, a brightness enhancement film, a conductive film for a touch panel, or a diffusion plate, a light guide, a prism. Can be used as a sheet.

  Various functional coating layers may be formed on the surface of the optical film of the present invention as necessary. The functional coating layer is, for example, an antistatic layer; an adhesive layer such as a pressure-sensitive adhesive layer or an adhesive layer; an easy adhesion layer; an antiglare layer (non-glare) layer; an antifouling layer such as a photocatalyst layer; an antireflection layer; An ultraviolet shielding layer, a heat ray shielding layer, an electromagnetic wave shielding layer, and a gas barrier layer.

  The optical film of the present invention can be used in combination with other optical members as necessary, for example, in a state of being bonded to each other. Other optical members are, for example, optical films exemplified as applications of the optical film of the present invention.

  The optical film of the present invention is a known film forming method from the resin composition of the present invention or from the (meth) acrylic polymer (A) and the cellulose ester polymer (B) before making the resin composition of the present invention. Can be manufactured. When the optical film of the present invention is a retardation film, the retardation film can be produced by stretching the unstretched film (original film) thus formed by a known film stretching method.

  Examples of the film forming method include a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Of these, the solution casting method and the melt extrusion method are preferable.

  A known uniaxial stretching method or biaxial stretching method can be applied to the stretching of the original film.

  Examples of the melt extrusion method include a T-die method and an inflation method. In the T-die method, a T-die is disposed at the tip of a melt extruder, and a film melt-extruded from the T-die is wound to obtain a film wound in a roll shape. At this time, it is also possible to adjust the temperature and speed of winding and to apply stretching (uniaxial stretching) in the film extrusion direction.

  In the case of melt extrusion, it is preferable to devolatilize volatile components from the vent portion of the melt extruder. Moreover, it is preferable to use together filtration of the resin composition by a polymer filter in the case of melt extrusion.

  The solution casting method generally has (1) a dissolution step, (2) a casting step, and (3) a drying step. A known method can be applied to each step.

  The specific procedure of the dissolution step is not limited as long as a solution containing the (meth) acrylic polymer (A) and the cellulose ester polymer (B) is obtained. As a solvent for dissolving both polymers, a good solvent such as methylene chloride, methyl acetate and dioxolane can be used, and at the same time, a poor solvent such as methanol, ethanol and butanol can be used in combination. As long as the cellulose ester polymer (B) is dissolved, a polymerization solvent used when the (meth) acrylic polymer (A) is polymerized may be used.

  A known solution coating method can be applied to the casting process. This method is, for example, a coating method using a die coater, a doctor blade coater, a roll coater, a comma coater, a lip coater or the like.

  The specific procedure of the drying step is not particularly limited as long as the film is formed by drying the coating film formed by the casting step.

[Phase difference film]
The retardation film of the present invention is a kind of the optical film of the present invention, and has the characteristics of the optical film of the present invention described above. The retardation film of the present invention may further have the following characteristics depending on the type and content of the (meth) acrylic polymer (A) and the cellulose ester polymer (B) included in the retardation film.

  The in-plane retardation (Re) exhibited by the retardation film of the present invention varies depending on the stretched state of the film, but is, for example, 50 nm or more as a value per 100 μm of film thickness with respect to light having a wavelength of 590 nm. Kinds of (meth) acrylic polymer (A) and cellulose ester polymer (B) contained in the retardation film of the present invention, and (meth) acrylic polymer (A) and cellulose ester polymer in the retardation film of the present invention Depending on the content of (B), it is 140 nm or more, and further 150 nm or more and 500 nm or less.

  The retardation film of the present invention can have a high degree of freedom for controlling the wavelength dispersion of the retardation. For example, the phase difference film exhibits a reverse wavelength dispersibility (wavelength dispersibility in which the phase difference decreases as the wavelength of light decreases, at least in the visible light range), or the retardation film has a flat wavelength dispersibility of the phase difference. . As a specific example, the in-plane phase differences Re (447), Re (590), and Re (750) for light of wavelengths 447, 590, and 750 nm are expressed by the following equation: 0.8 ≦ Re (447) / Re (590 ) ≦ 1.0, and 1.0 ≦ Re (750) / Re (590) ≦ 1.2.

  The Nz coefficient of the retardation film of the present invention is preferably less than 1.20, more preferably 1.15 or less, and even more preferably 1.10 or less and 0.95 or more in terms of light with a wavelength of 590 nm. The Nz coefficient is a value represented by the formula Nz = (Rth / Re) +0.5, where Re is the in-plane retardation of the retardation film and Rth is the retardation in the thickness direction.

[Image display device]
The image display device of the present invention includes the retardation film of the present invention. As a result, the image display device is excellent in image display characteristics, for example, an image display device with high contrast and a wide viewing angle.

  The image display device of the present invention is, for example, a liquid crystal display device (LCD).

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

[Average molecular weight]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined by polystyrene conversion using gel permeation chromatography (GPC) according to the following measurement conditions.
Measurement system: Tosoh GPC system HLC-8220
Developing solvent: Chloroform (Wako Pure Chemical Industries, special grade)
Solvent flow rate: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Measurement side column configuration: Tosoh, TSK-GEL super HZM-M 6.0X150, 2 in series
Tosoh, TSK-GEL super HZ-L 4.6X35, 1 Reference column configuration: Tosoh, TSK-GEL SuperH-RC 6.0X150, 2 in series Column temperature: 40 ° C.

[Glass-transition temperature]
The glass transition temperature (Tg) was determined according to JIS K7121. Specifically, it is obtained by using a differential scanning calorimeter (manufactured by Rigaku, DSC-8230) to raise a temperature of about 10 mg from room temperature to 200 ° C. (temperature increase rate 20 ° C./min) in a nitrogen gas atmosphere. The DSC curve was evaluated by the starting point method. Α-alumina was used as a reference.

[Haze ratio]
The haze ratio of the produced optical film was evaluated using a turbidimeter (Nippon Denshoku Industries Co., Ltd., NDH5000). In addition, the turbidimeter performs measurement based on JIS K7165.

[Photoelastic coefficient Cd]
The photoelastic coefficient with respect to the light of wavelength 590nm in the produced optical film was evaluated using an ellipsometer (manufactured by JASCO, M-150). Specifically, the produced optical film is cut into 20 mm × 50 mm with the stretching direction as the long side to obtain a measurement sample, which is attached to the photoelasticity measurement unit of the ellipsometer, and is 5 to 25 N parallel to the stretching direction. Three-point birefringence was measured while applying a stress load, and the slope of birefringence with respect to stress when using light having a wavelength of 590 nm was defined as a photoelastic coefficient.

[Moisture permeability]
The moisture permeability of the produced optical film was determined according to JIS Z0208 under the measurement condition of 40 ° C. Table 1 below shows values converted per film thickness of 100 μm.

[Optical properties of retardation film]
An in-plane retardation Re and a thickness direction retardation Rth with respect to light having a wavelength of 590 nm in the produced retardation film were measured at an incident angle of 40 ° using a retardation film / optical material inspection apparatus RETS-100 (manufactured by Otsuka Electronics). Evaluation was performed under the conditions of The in-plane phase difference Re is defined by the formula Re = (nx−ny) × d, and the thickness direction phase difference Rth is defined by the formula Rth = [(nx + ny) / 2−nz] × d. Here, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to nx in the film plane, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film ( nm). The slow axis direction is the direction in which the refractive index is maximum in the film plane. The Nz coefficient of the produced retardation film was calculated by the formula Nz coefficient = (Rth / Re) +0.5 from the values of Re and Rth obtained as described above.

  Separately from this, the in-plane retardation Re (447) and Re (750) for the light having a wavelength of 447 nm and 750 nm in the produced retardation film was similarly evaluated, and the in-plane retardation Re for the light having the wavelength of 590 nm was determined. By taking the ratio with (590), the values of Re (447) / Re (590) and Re (750) / Re (590) were obtained.

(Production Example 1)
A reactor having an internal volume of 30 L (liter) equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe was charged with 52 parts by weight of methyl methacrylate (MMA) and 30 parts by weight of 2- (hydroxymethyl) methyl acrylate (MHMA). Part by weight, 18 parts by weight of normal butyl methacrylate (BMA), and 67 parts by weight of a mixed solvent (weight ratio 9: 1) of methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK) as a polymerization solvent The temperature was raised to 105 ° C. When refluxing with increasing temperature started, 0.06 parts by weight of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and 33 parts by weight of the above mixed solvent. While the solution in which 0.12 parts by weight of t-amylperoxyisononanoate was dissolved in was added dropwise over 3 hours, solution polymerization was allowed to proceed under reflux at about 95 to 110 ° C., and the aging was further continued for 4 hours. went.

Next, 0.2 parts by weight of an octyl phosphate / dioctyl mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-8) is added to the resulting polymerization solution as a cyclization condensation catalyst (cyclization catalyst). The cyclization condensation reaction was allowed to proceed for 2 hours under reflux at about 85-100 ° C. Then, it was further heated at 240 ° C. for 90 minutes in an autoclave pressurized to a maximum gauge pressure of about 2 MPa. Next, the obtained polymerization solution was a vent type screw twin screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4. (Φ = 30 mm, L / D = 40) was introduced at a processing rate of 2.0 kg / hour in terms of resin amount, and further progress and devolatilization of the cyclization condensation reaction were carried out in the extruder. Thereafter, the polymer in a molten state is extruded from the extruder, and the main chain has a lactone ring structure and the (meth) acrylic polymer (A-1) having a BMA unit of 18% by weight of the total constituent units. Pellets were obtained. The weight average molecular weight of the polymer (A-1) was 1260,000, and Tg was 123 ° C. The BMA unit is a (meth) acrylic acid alkyl ester unit represented by the formula (1), in which R ¹ is an n-butyl group and R ² is CH ₃ (methyl group).

(Production Example 2)
Similar to Production Example 1, except that the amount of each monomer charged to the reactor was 60 parts by weight of MMA, 30 parts by weight of MHMA, and 10 parts by weight of BMA, and the main chain had a lactone ring structure, and all the BMA units were composed. A pellet of (meth) acrylic polymer (A-2) having 10% by weight of the unit was obtained. The weight average molecular weight of the polymer (A-2) was 134,000, and Tg was 130 ° C.

(Production Example 3)
The main chain has a lactone ring structure in the same manner as in Production Example 1, except that the reactor is not charged with BMA, the amount of MMA charged into the reactor is 70 parts by weight, and the amount of MHMA is 30 parts by weight. The pellet of the (meth) acrylic polymer (C-1) which does not have the structural unit shown in (1) was obtained. The weight average molecular weight of the polymer (C-1) was 17,000 and Tg was 122 ° C.

(Production Example 4)
In a reactor having an internal volume of 30 L (liter) equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe, 24.5 parts by weight of MMA, 26 parts by weight of MHMA, 45 parts by weight of ethyl methacrylate (EMA), N-vinylcarbazole (NVCz) 4.5 parts by weight and, as a polymerization solvent, a mixed solvent of 86.5 parts by weight of toluene and 3.5 parts by weight of methanol was charged, and the temperature was raised to 95 ° C. while introducing nitrogen. When refluxing with increasing temperature started, 0.01 parts by weight of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 575) was added as a polymerization initiator, and toluene 10 The solution polymerization was allowed to proceed under reflux at about 90 to 100 ° C. while dropwise adding 0.10 parts by weight of the above-mentioned t-amylperoxy-2-hexylhexanoate to 8 parts by weight over 8 hours. Further, aging was performed for 12 hours.

Next, 0.2 parts by weight of an octyl phosphate / dioctyl mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-8) is added to the resulting polymerization solution as a cyclization condensation catalyst (cyclization catalyst). The cyclization condensation reaction was allowed to proceed for 2 hours under reflux at about 80 to 100 ° C. Then, it was further heated at 240 ° C. for 90 minutes in an autoclave pressurized to a maximum gauge pressure of about 2 MPa. Next, the obtained polymerization solution was dried at 240 ° C. under reduced pressure for 1 hour to have a lactone ring structure in the main chain, and a (meth) acrylic polymer having 45% by weight of EMA units based on the total constituent units ( A-3) was obtained. The weight average molecular weight of the polymer (A-3) was 17,000 and Tg was 122 ° C. The EMA unit is a (meth) acrylic acid ester unit represented by the formula (1), in which R ¹ is an ethyl group and R ² is CH ₃ (methyl group).

(Production Example 5)
The main chain has a lactone ring structure in the same manner as in Production Example 4 except that the amount of each monomer charged in the reactor is 44.5 parts by weight of MMA, 26 parts by weight of MHMA, 25 parts by weight of EMA, and 4.5 parts by weight of NVCz. And a (meth) acrylic polymer (A-4) having EMA units at 25% by weight of all the structural units was obtained. The weight average molecular weight of the polymer (A-4) was 17,000 and Tg was 129 ° C.

(Production Example 6)
EMA was not charged into the reactor, but the amount of MMA charged into the reactor was 69.5 parts by weight, the amount of MHMA was 26 parts by weight, and the amount of NVCz was 4.5 parts by weight. A (meth) acrylic polymer (C-2) having a lactone ring structure in the main chain and having no structural unit represented by the formula (1) was obtained. The weight average molecular weight of the polymer (C-2) was 163,000, and Tg was 138 ° C.

Example 1
70 parts by weight of the polymer (A-1) produced in Production Example 1 and cellulose acetate propionate (B-1) [acetyl group substitution degree 2.5% by weight, hydroxyl group substitution degree 1.8% by weight, propionyl A group substitution degree of 46% by weight, a number average molecular weight Mn = 63,000, a weight average molecular weight Mw = 175,000] and 30 parts by weight were dissolved in methylene chloride, and the resulting solution was stirred to form a polymer ( A-1) and cellulose acetate propionate (B-1) were mixed uniformly. Next, the obtained mixed solution was dried at 120 ° C. under reduced pressure for 1 hour to obtain 100 parts by weight of a solid resin composition.

  Next, the obtained resin composition was press-molded at 220 ° C. with a press molding machine to obtain an unstretched film having a thickness of 50 μm. The evaluation results of the obtained film are shown in Table 1 below.

(Example 2)
A film was obtained in the same manner as in Example 1 except that 50 parts by weight of the polymer (A-1) and 50 parts by weight of cellulose acetate propionate (B-1) were uniformly mixed. The evaluation results of the obtained film are shown in Table 1 below.

Example 3
A film was obtained in the same manner as in Example 1 except that the polymer (A-2) produced in Production Example 2 was used instead of the polymer (A-1). The evaluation results of the obtained film are shown in Table 1 below.

(Comparative Example 1)
A film was obtained in the same manner as in Example 1 except that the polymer (C-1) produced in Production Example 3 was used instead of the polymer (A-1). The evaluation results of the obtained film are shown in Table 1 below.

Example 4
A film was obtained in the same manner as in Example 1 except that the polymer (A-3) produced in Production Example 4 was used instead of the polymer (A-1). The evaluation results of the obtained film are shown in Table 1 below.

(Example 5)
A film was obtained in the same manner as in Example 4 except that 50 parts by weight of the polymer (A-3) and 50 parts by weight of cellulose acetate propionate were uniformly mixed. The evaluation results of the obtained film are shown in Table 1 below.

(Example 6)
A film was obtained in the same manner as in Example 1 except that the polymer (A-4) produced in Production Example 5 was used instead of the polymer (A-1). The evaluation results of the obtained film are shown in Table 1 below.

(Comparative Example 2)
A film was obtained in the same manner as in Example 1 except that the polymer (C-2) produced in Production Example 6 was used instead of the polymer (A-1). The evaluation results of the obtained film are shown in Table 1 below.

  As shown in Table 1, the film of the example had a small haze ratio and excellent transparency as compared with the film of the comparative example. And the tendency for the haze rate of the produced film to become small was confirmed, so that the content rate of the BMA unit or EMA unit in a (meth) acryl polymer was large. In addition, depending on the composition of the (meth) acrylic polymer (A) in the film of the example and the content of the (meth) acrylic polymer (A) in the produced film, the moisture permeability and photoelastic coefficient of the film However, it became low compared with the water vapor transmission rate and photoelastic coefficient of the film of the comparative example.

(Example 7)
The unstretched optical film produced in Example 1 (however, the thickness of the film was 120 μm) was measured using the tensile tester (manufactured by Instron) at a stretch ratio of 2 and a stretch temperature of 128 ° C. in the MD direction. The film was uniaxially stretched to obtain a stretched film (retardation film) having a thickness of 87 μm. The evaluation results of the obtained retardation film are shown in Table 2 below.

(Example 8)
Except for using the unstretched optical film produced in Example 2 (however, the thickness of the film was 120 μm), a stretched film (retardation film) having a thickness of 85 μm was obtained in the same manner as in Example 7. Obtained. The evaluation results of the obtained retardation film are shown in Table 2 below.

Example 9
The unstretched optical film produced in Example 3 (however, the thickness of the film was 120 μm) and the stretching temperature was 133 ° C., and the stretching was 82 μm in the same manner as in Example 7. A film (retardation film) was obtained. The evaluation results of the obtained retardation film are shown in Table 2 below.

(Example 10)
The unstretched optical film produced in Example 4 (however, the thickness of the film was 123 μm) and the stretching temperature was 127 ° C., and the stretching was 86 μm in the same manner as in Example 7. A film (retardation film) was obtained. The evaluation results of the obtained retardation film are shown in Table 2 below.

(Example 11)
A stretched film (retardation film) having a thickness of 84 μm was prepared in the same manner as in Example 7, except that the unstretched optical film prepared in Example 5 (however, the thickness of the film was 121 μm) was used. Obtained. The evaluation results of the obtained retardation film are shown in Table 2 below.

(Example 12)
A stretched film (retardation film) having a thickness of 87 μm was prepared in the same manner as in Example 7, except that the unstretched optical film prepared in Example 6 (however, the thickness of the film was 126 μm) was used. Obtained. The evaluation results of the obtained retardation film are shown in Table 2 below.

  As shown in Table 2, each of the retardation films produced in Examples 7 to 12 showed a large in-plane retardation Re and a positive thickness retardation Rth in the thickness direction, and an inverse wavelength dispersion for the in-plane retardation Re. showed that.

  In addition, the haze rate which the retardation film produced in Examples 7-12 showed was converted into the same film thickness, and was the same as the haze rate which the unstretched film (Examples 1-6) before extending | stretching shows. Moreover, as for the photoelastic coefficient which the retardation film produced in Examples 7-12 and the water vapor transmission rate per thickness of 100 micrometers are all, the photoelastic coefficient which the unstretched film (Examples 1-6) before extending | stretching and It was the same as moisture permeability.

  The optical film and retardation film of the present invention can be used in the same applications as conventional optical films and retardation films.

Claims (12)

An optical film comprising a resin composition,
The glass transition temperature of the optical film is 110 ° C. or higher,
The resin composition includes (meth) acrylic polymer (A) and cellulose ester polymer (B),
The (meth) acrylic polymer (A) has a (meth) acrylic acid alkyl ester unit and a methyl methacrylate unit represented by the following formula (1) as constituent units, and an ester group, an imide group or an acid anhydride. Having a ring structure having a group in the main chain;
The optical film whose weight average molecular weights of the said (meth) acrylic polymer (A) are 80,000 or more .

In the formula (1), R ¹ is an alkyl group having 2 to 18 carbon atoms, and R ² is H or CH ₃ . The optical film according to claim 1, wherein a content of the (meth) acrylic polymer (A) in the resin composition is 30% by weight or more. The optical film according to claim 1, wherein the ring structure is at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure. The optical film according to claim 1, wherein the ring structure is a lactone ring structure. The optical film according to claim 1, wherein the cellulose ester polymer (B) has a weight average molecular weight of 100,000 to 300,000. The optical film according to claim 1, wherein the cellulose ester polymer (B) is cellulose triacetate or cellulose acetate propionate. The optical film according to any one of claims 1 to 6, wherein the (meth) acrylic polymer (A) has a glass transition temperature of 110 ° C or higher. The optical film according to any one of claims 1 to 7, which has a haze ratio of 5% or less when measured in accordance with JIS K7165 and has a thickness of 50 µm. The optical film according to claim 1, which is a retardation film . The optical film according to claim 9 , wherein an absolute value of a photoelastic coefficient for light having a wavelength of 590 nm is 5 × 10 ⁻¹² Pa ⁻¹ or less. In-plane phase differences Re (447), Re (590), and Re (750) for light of wavelengths 447, 590, and 750 nm, respectively,
0.8 ≦ Re (447) / Re (590) ≦ 1.0, and 1.0 ≦ Re (750) / Re (590) ≦ 1.2
The optical film according to claim 9 or 10 satisfying the relationship: An image display device comprising the optical film according to any one of claims 9-11.