WO2011152060A1 - Retardation film and image display device provided with same - Google Patents

Abstract

The disclosed retardation film contains a layer comprising a resin composition containing 30-95 wt% of a (meth)acrylate polymer having a ring structure at the backbone, and 5-70 wt% of a cellulose ester polymer. The retardation film has low moisture permeability and a low photoelastic coefficient, and has a high degree of freedom of controlling retardation wavelength dispersion; for example the film exhibits a retardation reverse wavelength dispersion, or has a flat retardation wavelength dispersion. The retardation film is suitable for optical compensation applications in an image display device such as a liquid crystal display (LCD) device.

Description

Retardation film and image display device including the same

The present invention relates to a retardation film and an image display device including the film.

Conventionally, cellulosic polymers have been used in optical films including polarizer protective films and retardation films. Unlike a retardation film made of a general polymer such as polycarbonate, a retardation film made of a cellulosic polymer generally has a wavelength dispersibility (the retardation becomes smaller as the wavelength of light becomes shorter at least in the visible light region ( (Inverse wavelength dispersion of phase difference). Thereby, the improvement of the image display characteristic in a liquid crystal display device (LCD) provided with the said retardation film is anticipated. However, due to the characteristics of the cellulosic polymer, the retardation film has problems such as high moisture permeability, a high photoelastic coefficient, and a sufficiently large retardation.

Separately, a (meth) acrylic polymer having a ring structure in the main chain is used for the retardation film (see Patent Document 1: JP 2008-9378 A). A retardation film made of a (meth) acrylic polymer having a ring structure in the main chain has high transparency and heat resistance, while ensuring mechanical properties, particularly flexibility. The mechanical properties of the retardation film are improved by adding or stretching elastic particles such as rubber. However, when elastic particles are added, aggregation of the added particles must be suppressed to ensure transparency as a retardation film. In addition to this, a retardation film made of a (meth) acrylic polymer having a ring structure in the main chain has a shorter light wavelength at least in the visible light region, similar to a retardation film made of a general polymer. The wavelength dispersibility (forward wavelength dispersibility of the phase difference) that increases the phase difference is shown.

Patent Document 2 (Japanese Unexamined Patent Publication No. 2009-1744) discloses that a (meth) acrylic polymer having a ring structure in the main chain is useful as a modifier for a cellulose ester film, and has a ring structure in the main chain. By adding the (meth) acrylic polymer to the cellulose ester film, the horse's spine failure, deformation failure of the film represented by the core transfer is suppressed, and there is a retardation film as an example of the cellulose ester film. Is described. However, JP-A-2009-1744 does not describe how much a (meth) acrylic polymer having a ring structure in the main chain should be added as a modifier to the cellulose ester film. In the examples, only an example in which 4 to 12 parts by weight of the (meth) acrylic polymer is added to 100 parts by weight of cellulose ester is described.

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

The present invention is a retardation film comprising a layer comprising a resin composition comprising a (meth) acrylic polymer having a ring structure in the main chain and a cellulose ester polymer, and has a low photoelastic coefficient and moisture permeability, Providing a retardation film having a high degree of freedom in controlling the wavelength dispersion of the retardation (for example, it can exhibit reverse wavelength dispersion of the retardation, or the retardation can be flat at least in the visible light region). With the goal.

The retardation film of the present invention comprises a resin composition comprising 30 to 95% by weight of a (meth) acrylic polymer (A) having a ring structure in the main chain and 5 to 70% by weight of a cellulose ester polymer (B). A layer comprising (C).

The image display device of the present invention includes the retardation film of the present invention.

The retardation film of this invention contains the layer which consists of a resin composition which contains the (meth) acryl polymer (A) which has a ring structure in a principal chain, and a cellulose polymer (B) in the range of a specific content rate. As a result, the retardation film has a low photoelastic coefficient and moisture permeability and a high degree of freedom in controlling the wavelength dispersion of the retardation.

It is a top view which shows typically an example of the phase difference film of this invention.

[(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 ring structure that the (meth) acrylic polymer (A) has in the main chain can be a derivative of a (meth) acrylic acid ester unit. In this case, if the total of the (meth) acrylic acid ester unit and the ring structure is 50% by weight or more of all the structural units, a (meth) acrylic polymer is obtained.

The (meth) acrylic acid ester unit includes, 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, (meth) acrylic acid 2,3,4,5-tetrahydride Xipentyl, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, normal butyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) acrylic A structural unit formed by polymerization of monomers such as t-butyl acid. The (meth) acrylic polymer can have two or more of these structural units. From the viewpoint of thermal stability, the (meth) acrylic polymer (A) preferably has methyl methacrylate (MMA) units.

The (meth) acrylic polymer (A) preferably 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.

When a resin composition containing a (meth) acrylic polymer and a cellulose ester polymer is molded, the surface haze 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. A film with reduced transparency cannot be used as a retardation film. When the (meth) acrylic polymer (A) contains the (meth) acrylic acid alkyl ester unit X, such an increase in haze is suppressed, and a retardation film excellent in transparency is obtained.

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 ratio is preferably 10% by weight or more, and more preferably 15% by weight or more because the effect of suppressing the increase in haze can be obtained with certainty. The upper limit of the said ratio is not specifically limited, For example, it is 50 weight%. The proportion of the (meth) acrylic acid alkyl ester unit X in all the 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). The ratio is the ratio of each monomer used for the polymerization of the (meth) acrylic polymer (A) and, if necessary, the reaction from the monomer to the (meth) acrylic polymer (A). It can also be obtained by referring to the mechanism.

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

(Meth) acrylic polymer (A) may have structural units other than (meth) acrylic acid ester units. The structural unit is, for example, (meth) acrylic acid, styrene, vinyl toluene, α-methyl styrene, α-hydroxymethyl styrene, α-hydroxyethyl styrene, 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 is further suppressed, and high optical characteristics can be obtained when a retardation 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, more preferably 20 to 60% by weight. The content of 2- (hydroxymethyl) acrylic acid ester units is preferably 10 to 60% by weight, 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 N-vinylcarbazole units is preferably 1 to 20% by weight, more preferably 3 to 8% by weight. Examples of 2- (hydroxymethyl) acrylic acid ester units include 2- (hydroxymethyl) methyl acrylate (MHMA) units, 2- (hydroxymethyl) ethyl acrylate units, 2- (hydroxymethyl) acrylic acid isopropyl units, 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 retardation film.

(Meth) acrylic polymer (A) has a ring structure in the main chain. The (meth) acrylic polymer (A) having a ring structure in the main chain contributes to the retardation film of the present invention exhibiting a large in-plane retardation and suppression of haze increase.

In addition, the (meth) acrylic polymer (A) having a ring structure in the main chain has a high glass transition temperature (Tg), for example, 110 ° C. or higher, 120 ° C. or higher depending on the structure of the polymer, and 130 It is above ℃. By including the (meth) acrylic polymer (A) having such a high Tg, the heat resistance of the retardation film of the present invention is improved. Since the retardation film having high heat resistance can be disposed near a heat generating portion such as a light source, it is suitable for use in an image display device such as an LCD.

The content of the ring structure in the (meth) acrylic polymer (A) is preferably 25 to 90% by weight, more preferably 35 to 90% by weight, and particularly preferably 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) will fall, and manufacture of retardation film may become difficult.

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

More specific examples of the ring structure are 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. These ring structures have a large contribution to the large in-plane retardation described above.

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 or a glutarimide structure, particularly a lactone ring structure, in the main chain has particularly low birefringence wavelength dispersion. For this reason, the freedom degree of control of the wavelength dispersion of retardation in the retardation film of this invention becomes higher between flat wavelength dispersion and reverse wavelength dispersion. In addition, the (meth) acrylic polymer (A) having a lactone ring structure in the main chain has particularly high compatibility with the cellulose ester polymer (B). High compatibility contributes to suppression of haze rise.

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, but it is excellent in stability as a ring structure. A membered ring or a 6-membered ring is preferable, and a 6-membered ring is more preferable. 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 MMA units as constituent units can be used as a precursor, the following formula ( The structure represented by 2) 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 can 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 obtained by, for example, copolymerizing a monomer group containing MMA and MHMA, and then subjecting adjacent MMA units and MHMA units to dealcoholization cyclization in the obtained copolymer. It can be formed by condensation. 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 determined with the cellulose ester polymer (B), particularly the cellulose acetate polymer. From the viewpoint of compatibility, it is preferably 25 to 90% by weight, more preferably 25 to 70% by weight, particularly preferably 30 to 60% by weight, and most preferably 35 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, 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 improves the thermal stability of the resin composition containing the polymer (A), and contributes to the production of a retardation film having high strength and a desirable appearance.

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

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) is formed by heating the polymer (a) having a hydroxyl group and an ester group in the molecular chain in the presence of an arbitrary catalyst to advance a lactone cyclization condensation reaction accompanied by dealcoholization. sell.

The polymer (a) is formed, for example, by polymerization of a monomer group including a monomer represented by the following formula (3). When the polymer (A) has a (meth) acrylic acid alkyl ester unit X represented by the formula (1) as a constituent unit, the polymer (a) includes, for example, a monomer represented by the following formula (3) and It can be formed by polymerization of a monomer group containing 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) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- (hydroxy Methyl) normal butyl acrylate, t-butyl 2- (hydroxymethyl) acrylate. Of these, methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferred, and methyl 2- (hydroxymethyl) acrylate (MHMA) is particularly preferred from the viewpoint 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). Yes.

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

The monomer group used for forming the polymer (a) may contain 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.

The (meth) acrylic acid ester is, for example, an acrylic acid ester such as methyl acrylate, cyclohexyl acrylate, or benzyl acrylate; a methacrylic acid ester such as methyl methacrylate, cyclohexyl methacrylate, or 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, vinyltoluene, α-methylstyrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, One type or two or more types may be included. 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 monomer groups, a polymerization initiator can 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, t-amyl peroxy-2- Organic peroxides such as ethyl hexanoate; 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 in the polymer (a). The cyclization catalyst is, for example, an esterification catalyst such as p-toluenesulfonic acid or a transesterification catalyst. Organic carboxylic acids such as acetic acid, propionic acid, benzoic acid, acrylic acid and methacrylic acid can 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. Yes.

The cyclization catalyst can 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 mono- or diesters thereof; dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid and the like dialkylphosphinic acids, diarylphosphinic acids or alkylarylphosphinic acids and These esters; alkylphosphonic acids or arylphosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid, and their Esters or diesters; alkylphosphinic acids or arylphosphinic acids such as methylphosphinic acid, ethylphosphinic acid, phenylphosphinic acid and their esters; methyl phosphite, ethyl phosphite, phenyl phosphite, Phosphorous acid monoesters, diesters or triesters such as dimethyl phosphate, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 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 acid Phosphate monoesters such as stearyl, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate, Diesters or triesters; mono-, di- or trialkyl (aryl) phosphines such as methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine; methyldichloro Phosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, diphenylchlorophosphine, etc. Ruyl (aryl) halogen phosphines; mono- and di-oxides 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 -Or tri-alkyl (aryl) phosphines; tetraalkyl (aryl) phosphonium halides such as tetramethylphosphonium chloride, tetraethylphosphonium chloride, tetraphenylphosphonium chloride; Two or more of these organophosphorus compounds can 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 formed into a film by an unreacted reactive group remaining in a trace amount even after the lactone cyclization condensation reaction, foaming or between the polymers Cross-linking 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 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 a retardation 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, both the film formability of the resin composition (C) containing the cellulose polymer (B) and the mechanical properties of the finally obtained retardation film can be achieved. 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 550,000 to 120,000, and further 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 preferred, and particularly preferred.

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. Two or more cellulose ester polymers (B) can be used.

[Resin composition (C)]
The resin composition (C) contains 30 to 95% by weight of the (meth) acrylic polymer (A) having a ring structure in the main chain and 5 to 70% by weight of the cellulose ester polymer (B). The resin composition (C) preferably contains 50 to 90% by weight of the (meth) acrylic polymer (A) and 10 to 50% by weight of the cellulose ester polymer (B), more preferably the (meth) acrylic polymer. (A) 70 to 90% by weight and cellulose ester polymer (B) 10 to 30% by weight are included.

When the content of the (meth) acrylic polymer (A) in the resin composition (C) is excessively large, the degree of freedom in controlling the wavelength dispersion of the retardation in the finally obtained retardation film is lowered. On the other hand, when the content of the cellulose ester polymer (B) in the resin composition (C) is excessively high, the photoelastic coefficient and moisture permeability of the finally obtained retardation film are increased.

Resin composition (C) 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 (C) has a content other than the (meth) acrylic polymer (A) and the cellulose ester polymer (B) in the resin composition (C). Up to 40% by weight, preferably up to 10% by weight.

Examples of the polymer include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, 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; polyacetals; polycarbonates; polyphenylene oxides; polyphenylene sulfides: polyether ether ketones; polyether nitriles; Li polyether sulfone; a; polyoxyethylene Penji alkylene; polyamideimide.

Among these polymers, vinyl methacrylate is a single monomer because of its excellent 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 polymer and a structural unit derived from an aromatic vinyl monomer, such as a styrene-acrylonitrile copolymer, is preferred.

Resin composition (C) may contain any material as long as the effects of the present invention are obtained. The material includes, for example, an ultraviolet absorber; an antioxidant; a stabilizer such as a light-resistant stabilizer, a weather-resistant stabilizer and a heat stabilizer; a reinforcing material such as a glass fiber and a carbon fiber; a near-infrared absorber; 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 modifier; anti-blocking agent; matting agent; acid scavenger; metal deactivator; plasticizer; lubricant; rubber mass such as ASA and ABS. The content of these materials in the resin composition (C) is, for example, 0 to 5% by weight, preferably 0 to 2% by weight, and more preferably 0 to 0.5% by weight.

UV absorbers are, for example, benzophenone compounds, salicinate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of the 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 the triazine compound 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.

Resin composition (C) may contain two or more ultraviolet absorbers. When the resin composition (C) contains an ultraviolet absorber, the content of the ultraviolet absorber in the resin composition (C) is not particularly limited. In the state of the retardation 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 retardation film may be deteriorated, or the retardation film may be yellowed.

The antioxidant is, for example, a hindered phenol compound, a phosphorus compound, or a sulfur compound. The resin composition (C) can contain two or more 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-butylpheny L) 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-hydroxy Benzoate, 2- (2-hydroxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, diethylglycol Rubis- (3,5-di-t-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl-3- (3,5-di-t-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-tert-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-t-butyl-4- Droxyphenyl) propionate], sorbitol hexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl-7- (3-methyl-5-tert-butyl- 4-hydroxyphenyl) propionate, 2-stearoyloxyethyl-7- (3-methyl-5-tert-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, 0 tetraoxaspiro [5,5] - undecanoic.

It is preferable to use an antioxidant composed of a phenolic compound (phenolic antioxidant) in combination with a thioether antioxidant or a phosphoric acid antioxidant. The content of both antioxidants in the resin composition (C) 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 antioxidant include pentaerythrityl tetrakis (3-lauryl thiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl- 3,3′-thiodipropionate.

Examples of phosphoric acid-based antioxidants 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 (1,1dimethylethyl) 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 Ito, cyclic neopentanetetraylbis (2,6-di -t- butyl-4-methylphenyl) is phosphite.

The content of the antioxidant in the resin composition (C) 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. More preferably 0.05 to 1% by weight. When the content of the antioxidant becomes excessively large, the antioxidant may bleed out or silver streaks may occur when the retardation film is formed from the resin composition (C) by melt extrusion. is there.

[Phase difference film]
FIG. 1 shows an example of the retardation film of the present invention. The retardation film 1 of the present invention shown in FIG. 1 has a (meth) acrylic polymer (A) having a ring structure in the main chain of 30 to 95% by weight and a cellulose ester polymer (B) of 5 to 70% by weight. It is comprised from the layer which consists of a resin composition (C) containing. The retardation film of the present invention can be provided with an arbitrary layer other than the layer composed of the resin composition (C) as necessary, but in order to obtain the effects of the present invention more reliably, as shown in FIG. Furthermore, it is preferable that it is comprised from the layer which consists of a resin composition (C), ie, it is comprised from the resin composition (C). However, the layer can have a functional coating layer on its surface.

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

The in-plane retardation Re indicated 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), the in-plane retardation Re is 140 nm or more, further 150 nm or more and 500 nm or less as a value per 100 μm of film thickness.

The degree of freedom in controlling the wavelength dispersion of the retardation in the retardation film of the present invention is high. For example, the retardation film exhibits a reverse wavelength dispersion of the retardation or has a flat wavelength dispersion. 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 ) ≦ 1.2, and 0.8 ≦ Re (750) / Re (590) ≦ 1.2. In the retardation film of the present invention, Re (447), Re (590) and Re (750) have the formulas 0.8 ≦ Re (447) / Re (590) ≦ 1.1 and 0.9 ≦ Re ( 750) / Re (590) ≦ 1.2 and satisfy the formulas 0.8 ≦ Re (447) / Re (590) ≦ 1.0 and 1.0 ≦ Re (750) / Re ( 590) ≦ 1.2 is more preferable.

The moisture permeability per 100 μm thickness in the retardation film of the present invention is, for example, 300 g / m ² · 24 hours or less as a value measured according to JIS Z0208. 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), the value may be 250 g / m ² · 24 hours or less, 200 g / m ² · 24 hours or less, 150 g / m ² · 24 hours or less, 130 g / m ² · 24 hours or less, Is 120 g / m ² · 24 hours or less.

The retardation film of the present invention exhibits high heat resistance based on the (meth) acrylic polymer (A) having a ring structure in the main chain, and its Tg is, for example, 110 ° C. or higher. 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), Tg is 120 ° C. or higher, 125 ° C. or higher, and further 130 ° C. or higher.

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

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.

The total light transmittance of the retardation 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 in accordance with JIS K7361-1.

The haze of the retardation film of the present invention is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less as measured at a thickness of 50 μm as measured according to JIS 7165.

In the retardation film of the present invention, various functional coating layers can be formed on the surface of the layer made of the resin composition (C) 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 application of the retardation film of the present invention is not particularly limited, and can be used for the same application as a conventional retardation film. The retardation film of the present invention is suitable for optical compensation in an image display device such as an LCD. Further, in addition to the LCD, it can be used for various image display devices and optical devices.

The retardation 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.

The retardation film of the present invention is a known film formed from the resin composition (C), or from the (meth) acrylic polymer (A) and the cellulose ester polymer (B) before making the resin composition (C). It can be produced by a method and a film stretching method. Specifically, for example, the resin composition (C) is formed into a film to form an original film (unstretched film), and the obtained original film is stretched.

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 method of the original film.

The melt extrusion method is, for example, a T-die method or an inflation method. In the T-die method, a T-die is placed at the tip of a melt extruder, and a film melt-extruded from the T-die is taken up, whereby an original film wound in a roll shape is obtained. 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.

During 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 a (meth) acrylic polymer (A) and a cellulose ester polymer (B) having a ring structure in the main chain is obtained. A good solvent such as methylene chloride, methyl acetate, and dioxolane can be used as a solvent for dissolving both polymers, and a poor solvent such as methanol, ethanol, and butanol can be used in combination. As long as the cellulose ester polymer (B) is dissolved, the polymerization solvent used when the (meth) acrylic polymer (A) is polymerized can 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 process is not particularly limited as long as a film is formed by drying the coating film formed by the casting process.

[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, an 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 connection Tosoh, TSK-GEL super HZ-L 4.6X35, 1 Reference side 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.

[Melt flow rate (MFR)]
The MFR was determined in accordance with JIS K6874 with a test temperature of 240 ° C. and a test load of 10 kg.

[Optical properties of retardation film]
The in-plane retardation Re and the 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 phase difference Rth in the thickness direction 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.

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

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

[Haze]
The haze of the produced retardation film was evaluated using a turbidimeter (Nippon Denshoku Industries Co., Ltd., NDH5000). In addition, the turbidimeter performs measurement based on JIS K7165. The table below shows the values per 50 μm of film thickness.

(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 6000 g of methyl methacrylate (MMA), 3000 g of methyl 2- (hydroxymethyl) acrylate (MHMA), and methacrylic acid. Normal butyl (BMA) 1000 g and a mixed solvent of methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK) 6667 g as a polymerization solvent (9: 1 by weight) were charged, and the temperature was raised to 105 ° C. through nitrogen. . When refluxing with a rise in temperature started, 6.0 g of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and the above-mentioned t- While a solution in which 12.0 g of amyl peroxyisononanoate was dissolved was added dropwise over 3 hours, solution polymerization was allowed to proceed under reflux at about 95 to 110 ° C., followed by further aging for 4 hours. The polymerization reaction rate was 90.5%, and the content of MHMA units in the obtained polymer was 29.7% by weight.

Next, 20 g of an octyl phosphate / dioctyl mixture (manufactured by Sakai Chemical Co., Ltd., trade name: Phoslex A-8) is added to the resulting polymerization solution as a catalyst for the cyclization condensation reaction (cyclization catalyst). The cyclization condensation reaction was allowed to proceed for 2 hours under reflux at 100 ° C. Furthermore, after heating at 240 ° C. for 90 minutes in an autoclave pressurized to a maximum of about 2 MPa as a gauge pressure, the obtained polymerization solution was devolatilized in a vent type screw twin screw extruder, extruded, and formed into a main chain. A transparent (meth) acrylic polymer (A-1) having a lactone ring structure was obtained. The weight average molecular weight of the polymer (A-1) was 134,000, the MFR was 14.5 g / 10 min, and the Tg was 130 ° C.

Example 1
90 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] 10 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. by a press molding machine to obtain a film (unstretched film) having a thickness of 126 μm. Next, the produced film was uniaxially stretched in the MD direction at a stretching ratio of 2 and a stretching temperature of 133 ° C. by a tensile tester (Instron) to obtain a stretched film (F1) having a thickness of 85 μm. The evaluation results of the stretched film (F1) are shown in Table 1 below.

(Example 2)
Example except that 70 parts by weight of polymer (A-1) and 30 parts by weight of cellulose acetate propionate (B-1) were dissolved in methylene chloride, and a 120 μm-thick original film was prepared. 1, a stretched film (F2) having a thickness of 82 μm was obtained. The evaluation results of the stretched film (F2) are shown in Table 1 below.

(Example 3)
Example except that 50 parts by weight of polymer (A-1) and 50 parts by weight of cellulose acetate propionate (B-1) were dissolved in methylene chloride, and an original film having a thickness of 118 μm was prepared. 1, a stretched film (F3) having a thickness of 83 μm was obtained. The evaluation results of the stretched film (F3) are shown in Table 1 below.

(Comparative Example 1)
10 parts by weight of polymer (A-1) and 90 parts by weight of cellulose acetate propionate (B-1) were dissolved in methylene chloride, an original film having a thickness of 104 μm was prepared, and the stretching temperature was A stretched film (F4) having a thickness of 72 μm was obtained in the same manner as in Example 1 except that the temperature was 135 ° C. The evaluation results of the stretched film (F4) are shown in Table 1 below.

As shown in Table 1, the stretched films of Examples 1 to 3 had lower moisture permeability and photoelastic coefficient than the stretched film of Comparative Example 1, yielded a large in-plane retardation, and had a small Nz coefficient. . Further, the retardation in the stretched films of Examples 1 to 3 showed flat wavelength dispersion or reverse wavelength dispersion.

(Production Example 2)
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 methyl 2- (hydroxymethyl) 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-amylperoxyisononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and 33 parts by weight of the above mixed solvent was added. While the solution in which 0.12 part 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 converted into 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 the molten state is extruded from the extruder, and the (meth) acrylic polymer (A-2) having a lactone ring structure in the main chain and having 18% by weight of BMA units in all the structural units. Pellets were obtained. The polymer (A-2) had a weight average molecular weight of 1260,000 and a Tg of 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 3)
The main chain has a lactone ring structure and all the BMA units as in Production Example 2 except that the amount of each monomer charged into the reactor is 60 parts by weight of MMA, 30 parts by weight of MHMA, and 10 parts by weight of BMA. A pellet of (meth) acrylic polymer (A-3) having 10% by weight of the unit was obtained. The polymer (A-3) had a weight average molecular weight of 134,000 and a Tg of 130 ° C.

(Production Example 4)
The main chain has a lactone ring structure in the same manner as in Production Example 2 except that BMA is not charged into the reactor, the amount of MMA charged into the reactor is 70 parts by weight, and the amount of MHMA is 30 parts by weight. A pellet of the (meth) acrylic polymer (C-1) not having 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 5)
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 24.5 parts by weight of MMA, 26 parts by weight of MHMA, 45 parts by weight of ethyl methacrylate (EMA), and 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. At the start of reflux accompanying the temperature increase, 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 While a solution in which 0.10 parts by weight of the above t-amylperoxy-2-heptylhexanoate was dissolved in parts by weight was added dropwise over 8 hours, the solution polymerization was allowed to proceed under reflux at about 90 to 100 ° C. 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-4) was obtained. The weight average molecular weight of the polymer (A-4) 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 6)
The main chain has a lactone ring structure in the same manner as in Production Example 5 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. In addition, a (meth) acrylic polymer (A-5) having EMA units and 25% by weight of all structural units was obtained. The polymer (A-5) had a weight average molecular weight of 17,000 and a Tg of 129 ° C.

(Production Example 7)
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. As a result, 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 the Tg was 138 ° C.

(Production Example 8)
70 parts by weight of the polymer (A-2) produced in Production Example 2 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-2) 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 2 below.

(Production Example 9)
An unstretched film was obtained in the same manner as in Production Example 8, except that 50 parts by weight of the polymer (A-2) 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 2 below.

(Production Example 10)
An unstretched film was obtained in the same manner as in Production Example 8, except that the polymer (A-3) produced in Production Example 3 was used instead of the polymer (A-2). The evaluation results of the obtained film are shown in Table 2 below.

(Production Example 11)
An unstretched film was obtained in the same manner as in Production Example 8, except that the polymer (C-1) produced in Production Example 4 was used instead of the polymer (A-2). The evaluation results of the obtained film are shown in Table 2 below.

(Production Example 12)
An unstretched film was obtained in the same manner as in Production Example 8, except that the polymer (A-4) produced in Production Example 5 was used instead of the polymer (A-2). The evaluation results of the obtained film are shown in Table 2 below.

(Production Example 13)
An unstretched film was obtained in the same manner as in Production Example 12, except that 50 parts by weight of the polymer (A-4) 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 2 below.

(Production Example 14)
An unstretched film was obtained in the same manner as in Production Example 8, except that the polymer (A-5) produced in Production Example 6 was used instead of the polymer (A-2). The evaluation results of the obtained film are shown in Table 2 below.

(Production Example 15)
A film was obtained in the same manner as in Production Example 8, except that the polymer (C-2) produced in Production Example 7 was used instead of the polymer (A-2). The evaluation results of the obtained film are shown in Table 2 below.

As shown in Table 2, the films of Production Examples 8 to 10 and Production Examples 12 to 14 were smaller in haze than the films of Production Examples 11 and 15, and were excellent in transparency. And the tendency for the haze 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 to this, depending on the composition of the (meth) acrylic polymer (A) in the films of Production Examples 8 to 10 and Production Examples 12 to 14 and the content of the (meth) acrylic polymer (A) in the produced films, The moisture permeability and photoelastic coefficient of the film were lower than the moisture permeability and photoelastic coefficient of the films of Production Examples 11 and 15.

Example 4
The unstretched film produced in Production Example 8 (however, the thickness of the film was 120 μm) was uniaxially oriented in the MD direction at a stretching ratio of 2 and a stretching temperature of 128 ° C. using a tensile tester (manufactured by Instron). The film was 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 3 below.

(Example 5)
A stretched film (retardation film) having a thickness of 85 μm was obtained in the same manner as in Example 4 except that the unstretched film produced in Production Example 9 (however, the thickness of the film was 120 μm) was used. . The evaluation results of the obtained retardation film are shown in Table 3 below.

(Example 6)
A stretched film having a thickness of 82 μm (as in Example 4), except that the unstretched film produced in Production Example 10 (however, the thickness of the film was 120 μm) and the stretching temperature was 133 ° C. Retardation film) was obtained. The evaluation results of the obtained retardation film are shown in Table 3 below.

(Example 7)
Except for using the unstretched film produced in Production Example 12 (however, the thickness of the film was 123 μm) and the stretching temperature was 127 ° C., a stretched film having a thickness of 86 μm ( Retardation film) was obtained. The evaluation results of the obtained retardation film are shown in Table 3 below.

(Example 8)
A stretched film (retardation film) having a thickness of 84 μm was obtained in the same manner as in Example 4 except that the unstretched film produced in Production Example 13 (however, the thickness of the film was 121 μm) was used. . The evaluation results of the obtained retardation film are shown in Table 3 below.

Example 9
A stretched film (retardation film) having a thickness of 87 μm was obtained in the same manner as in Example 4 except that the unstretched film produced in Production Example 14 (however, the thickness of the film was 126 μm) was used. . The evaluation results of the obtained retardation film are shown in Table 3 below.

As shown in Table 3, each of the retardation films produced in Examples 4 to 9 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.

Note that the haze exhibited by the retardation films produced in Examples 4 to 9 and the haze exhibited by the stretched films produced by stretching the unstretched films produced in Production Examples 11 and 15 in the same manner as in Example 4 were the same film. It was the same as the haze indicated by the corresponding unstretched film before stretching (Production Examples 8 to 15) in terms of thickness. In addition, the photoelastic coefficient and moisture permeability per 100 μm thickness shown in the retardation films prepared in Examples 4 to 9 and the unstretched films prepared in Production Examples 11 and 15 were drawn in the same manner as in Example 4. The stretched film exhibited the same photoelastic coefficient and moisture permeability per 100 μm thickness as the corresponding unstretched film (Production Examples 8 to 15) before stretching.

The present invention can be applied to other embodiments without departing from the intent and essential features thereof. The embodiments disclosed in this specification are illustrative in all respects and are not limited thereto. The scope of the present invention is shown not by the above description but by the appended claims, and all changes that come within the meaning and scope of the claims are included therein.

The retardation film of the present invention can be used in the same applications as conventional retardation films, for example, various image display devices including LCD and optical devices.

Claims (9)

1. 30 to 95% by weight of (meth) acrylic polymer (A) having a ring structure in the main chain;
   A retardation film comprising a layer comprising a resin composition (C) comprising 5 to 70% by weight of a cellulose ester polymer (B).
2. The retardation film according to claim 1, wherein the (meth) acrylic polymer (A) has a (meth) acrylic acid alkyl ester unit represented by the following formula (1) as a structural unit.
   

   

   In the formula (1), R ¹ is an alkyl group having 2 to 18 carbon atoms, and R ² is H or CH ₃ .
3. The retardation film according to claim 2, wherein the (meth) acrylic polymer (A) has a methyl methacrylate unit and a 2- (hydroxymethyl) acrylic ester unit.
4. 3. The retardation film according to claim 2, wherein the (meth) acrylic polymer (A) has a methyl methacrylate unit, a 2- (hydroxymethyl) acrylic acid ester unit, and an N-vinylcarbazole unit.
5. The retardation film according to claim 1, wherein the (meth) acrylic polymer (A) has a methyl methacrylate unit.
6. The retardation film according to claim 1, wherein an absolute value of a photoelastic coefficient with respect to light having a wavelength of 590 nm is 5 × 10 ⁻¹² Pa ⁻¹ or less.
7. 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) ≦ 1.2, and 0.8 ≦ Re (750) / Re (590) ≦ 1.2
   The retardation film according to claim 1 satisfying the relationship:
8. The retardation film according to claim 1, wherein the haze at a thickness of 50 µm, measured in accordance with JIS K7165, is 5% or less.
9. An image display device comprising the retardation film according to any one of claims 1 to 8.

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