JP5983424B2 - Optical film, circularly polarizing plate, and organic EL display device - Google Patents

Description

  The present invention relates to an optical film, a circularly polarizing plate, and an organic EL display device.

  The λ / 4 retardation film can convert linearly polarized light into circularly polarized light and elliptically polarized light, or convert circularly polarized light and elliptically polarized light into linearly polarized light. Such a λ / 4 retardation film is widely used for various optical applications in image display devices and optical pickup devices.

  In recent years, a self-luminous display device such as an organic electroluminescence display device (organic EL display) has attracted attention as a new image display device. In the organic EL display, a reflector such as an aluminum plate is provided on the back side of the display in order to increase the light extraction efficiency. For this reason, there is a problem that external light incident on the display is reflected by the reflector and the contrast of the image is lowered. In order to suppress such a decrease in contrast of light and dark due to external light reflection, a circularly polarizing plate obtained by bonding a λ / 4 retardation film and a polarizer is disposed on the surface side of the display. In addition, the circularly polarizing plate may be used for a so-called 3D liquid crystal display device that displays a stereoscopic image.

  The circularly polarizing plate needs to be bonded so that the in-plane slow axis of the λ / 4 retardation film is inclined at a desired angle with respect to the absorption axis of the polarizer.

  However, since a general polarizer is obtained by stretching at a high magnification in the transport direction, the absorption axis thereof coincides with the transport direction (long direction) of the film. On the other hand, since a conventional retardation film is obtained by longitudinal stretching or transverse stretching, its in-plane slow axis is a direction of 0 ° or 90 ° with respect to the longitudinal direction of the film. Therefore, in order to bond the polarizer so that the absorption axis of the polarizer and the in-plane slow axis of the retardation film form a desired angle, the long polarizer and the retardation film cut obliquely are combined. A batch method of laminating one sheet at a time has been unavoidable, and a decrease in product yield due to deterioration of productivity and adhesion of chips etc. has been cited as a problem. In particular, in recent years when organic EL displays are being increased in size, the method of cutting the obtained retardation film obliquely and pasting it on a polarizer is required to be improved because the film utilization efficiency is low and the productivity is low. It was.

  On the other hand, various methods for producing a long retardation film that has been stretched in an oblique direction and whose in-plane slow axis is oblique to the width direction (or the long direction) of the film have been proposed. Unlike the conventional batch-type bonding, such a retardation film can be used to manufacture a circularly polarizing plate by bonding with a long polarizer and a roll-to-roll. As a result, productivity can be dramatically improved and yield can be greatly improved. In addition, since a circularly polarizing plate can be manufactured by laminating with a roll-to-roll, when manufacturing a circularly polarizing plate used for a large display, the use area of the long retardation film can be increased, The manufacturing cost of the circularly polarizing plate can be significantly reduced.

  By the way, a retardation film used for an optical device using a laser light source of a specific wavelength, such as an optical pickup device, has a quarter-wave retardation (hereinafter also referred to as retardation) with respect to only light of a specific wavelength. It suffices if it can be given. However, a retardation film constituting an antireflection film (circularly polarizing plate) such as a color image display device or an organic EL display has a flat wavelength where the retardation value does not fluctuate with respect to light in the entire wavelength range of visible light. It is required to give a phase difference of ¼ wavelength to light in the entire wavelength region of the phase difference value or visible light.

  In particular, a retardation film used in an organic EL display having an R (red) light emitting layer, a G (green) light emitting layer, and a B (blue) light emitting layer may have negative wavelength dispersion (reverse wavelength dispersion). Desired. Negative wavelength dispersion means a characteristic in which a phase difference imparted to long wavelength light is larger than a phase difference imparted to short wavelength light. However, a film that imparts a quarter-wave phase difference and exhibits sufficient negative wavelength dispersion (reverse wavelength dispersion); in particular, a single layer and a wavelength of λ / 4 with respect to light in a wide wavelength region It was difficult to obtain a film capable of imparting a phase difference.

  Conventionally, it is known that the film which has a cellulose ester as a main component shows reverse wavelength dispersion. However, in order to obtain a phase difference of λ / 4 wavelength with a film containing cellulose ester as a main component, it is necessary to increase the draw ratio. For this purpose, it is necessary to increase the film thickness. Moreover, it is difficult for a film mainly composed of cellulose ester to obtain a λ / 4 wavelength retardation in a wide wavelength region. For this reason, a method has been studied in which a specific additive is contained to improve the phase difference and to obtain a λ / 4 phase difference with respect to light in a wide wavelength region.

  For example, in Patent Document 1, as an additive for controlling wavelength dispersion (wavelength dispersion adjusting agent), the magnitude of a dipole moment in a direction orthogonal to the molecular long axis direction is a dipole in a direction parallel to the molecular long axis direction. An optical film containing a low molecular compound larger than the magnitude of the moment has been proposed. As such a low molecular weight compound, a compound having a phenyl group as a basic skeleton is disclosed.

JP 2007-249180 A

  However, an organic EL display using a circularly polarizing plate having a retardation film containing the compound described in Patent Document 1 as an antireflection film has a problem in that contrast is lowered and color variation occurs. The decrease in contrast and color variation were particularly remarkable when a retardation film obtained by stretching at high magnification at a high temperature was used.

  As a result of intensive studies on the cause of the decrease in contrast and color variation, the present inventors have found that the retardation and wavelength dispersion of the retardation film are uneven. And it discovered that the nonuniformity of retardation and wavelength dispersibility arises in the manufacturing process of retardation film, when a film shrink | contracts at the time of high magnification extending | stretching.

  The present invention has been made in view of the above circumstances, and provides an optical film having a high phase difference and good reverse wavelength dispersion, and having reduced retardation and wavelength dispersion. With the goal. Another object of the present invention is to provide a circularly polarizing plate including the optical film and an image display device having high contrast and little color variation.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have added a specific compound having an alkyleneoxy group, thereby having high in-plane retardation and good reverse wavelength dispersion. In addition, it has been found that an optical film with little retardation and wavelength dispersion can be obtained.

  The mechanism is not necessarily clear, but is presumed as follows. That is, an alkyleneoxy group contained in a specific compound causes an interaction due to a hydrogen bond with a hydroxyl group of the cellulose ester, or a dipolar interaction with a carbonyl group of the cellulose ester. Thereby, it is considered that an interaction occurs between the molecules of the cellulose ester or between the cellulose ester and the specific compound, thereby expressing a plasticizing effect. Moreover, it is thought that the alkyleneoxy group contained in a specific compound imparts a highly flexible partial structure to the cellulose ester and increases the flexibility of the film. It is thought that the shrinkage at the time of high magnification stretching can be suppressed by them. That is, the problem of the present invention is solved by the following means.

（一般式（１）中、
Ｄは、芳香族炭化水素環、非芳香族炭化水素環、芳香族複素環または非芳香族複素環を表し；
Ａは、単結合、−Ｏ−、−Ｓ−、−ＣＯ−、−ＣＳ−、−ＮＲ_１−、アルキレン基、アルケニレン基またはこれらの組み合わせからなる群より選ばれる連結基（Ｒ_１は、水素原子またはアルキル基）を表し；
Ｂは、下記式で表される連結基を表し；

（一般式（２）中、Ｒは、アルキレン基を表し、ｌは、２〜１０の整数を表す）
Ｒ_１１は、水素原子、アルキル基、または芳香族環を有さないアシル基を表し；
ｍは、１または２を表し；ｍが２の場合、複数のＢおよびＲ_１１は、それぞれ互いに同じでも異なっていてもよく；
ｎは、１または２を表し；ｎが２の場合、複数のＡ、ＢおよびＲ_１１は、それぞれ互いに同じであっても異なっていてもよく；
Ｌ_１１は、−Ｏ−、−Ｓ−、−ＣＯ−、−ＣＳ−、−ＮＲ_２−またはこれらの組み合わせからなる群より選ばれる連結基を表し（Ｒ_２は、それぞれ独立に水素原子またはアルキル基を表し）；
Ｒ_１２は、置換基を有してもよい、アルキル基、アリール基、シクロアルキル基またはヘテロ環基を表し；
ｐは、１または２を表し；ｐが２の場合、複数のＬ_１１およびＲ_１２は、それぞれ互いに同じでも異なっていてもよく；
Ｒ_１３は、置換基を表し；
ｑは、０〜４の整数を表し；ｑが２〜４の場合、複数のＲ_１３は互いに同じでも異なっていてもよい）
［２］ 前記一般式（１）で表される化合物において、ｐが２である、［１］に記載の光学フィルム。
［３］ 前記一般式（１）で表される化合物が、下記一般式（３）で表される化合物である、［１］または［２］に記載の光学フィルム。

（一般式（３）中、
ＡおよびＢは、前記一般式（１）におけるＡおよびＢと同義であり；
Ｒ_２１は、水素原子、アルキル基、または芳香族環を有さないアシル基を表し；
ｍは、１または２を表し；ｍが２の場合、複数のＢおよびＲ_２１は、互いに同じでも異なっていてもよく；
ｎは、１または２を表し；ｎが２の場合、複数のＡ、ＢおよびＲ_２１は、互いに同じであっても異なっていてもよく；
Ｌ_２１およびＬ_２２は、それぞれ独立して−Ｏ−、−Ｓ−、−ＣＯ−、−ＣＳ−、−ＮＲ_２−またはこれらの組み合わせからなる群より選ばれる連結基を表し（Ｒ_２は、それぞれ独立に水素原子またはアルキル基を表し）；
Ｒ_２２およびＲ_２４は、それぞれ独立して置換基を有してもよい、アリール基、シクロアルキル基またはヘテロ環基を表し；
Ｒ_２３は、置換基を表し；
ｒは、０〜３の整数を表し、かつｎ＋ｒ≦４であり；ｒが２または３である場合、複数のＲ_２３は互いに同じでも異なっていてもよい）
［４］ 前記一般式（１）または（３）で表される化合物が、芳香族炭化水素環または芳香族複素環を１つだけ有する、［１］〜［３］のいずれかに記載の光学フィルム。
［５］ 前記一般式（１）または（３）で表される化合物が、溶液吸収スペクトルにおいて、２５０ｎｍ以上４００ｎｍ以下の範囲に少なくとも１つの極大吸収波長を有する、［１］〜［４］のいずれかに記載の光学フィルム。
［６］ 前記一般式（１）で表される化合物の含有量が、前記セルロースエステルを含む熱可塑性樹脂の合計に対して１〜１５質量％である、［１］〜［５］のいずれかに記載の光学フィルム。
［７］ 前記光学フィルムの面内の遅相軸と、前記光学フィルムの幅方向とのなす角度が４０°以上５０°以下である、［１］〜［６］のいずれかに記載の光学フィルム。
［８］ 前記セルロースエステルのアシル基の総置換度が２．０以上２．６以下である、［１］〜［７］のいずれかに記載の光学フィルム。
［９］ 厚みが、１０〜７０μｍである、［１］〜［８］のいずれかに記載の光学フィルム。 [1] Including in-plane retardation values measured at wavelengths of 450 nm, 550 nm, and 650 nm, each of which includes a cellulose ester and at least one compound represented by the following general formula (1): R0 (450), An optical film satisfying the formulas (a) to (c) when R0 (550) and R0 (650) are set.
(A) 110 nm ≦ R0 (550) ≦ 170 nm
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.03
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.03

(In general formula (1),
D represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocycle or a non-aromatic heterocycle;
A represents a linking group selected from the group consisting of a single bond, —O—, —S—, —CO—, —CS—, —NR ₁ —, an alkylene group, an alkenylene group, or a combination thereof (R ₁ represents hydrogen Represents an atom or an alkyl group;
B represents a linking group represented by the following formula;

(In General Formula (2), R represents an alkylene group, and l represents an integer of 2 to 10)
R ₁₁ represents a hydrogen atom, an alkyl group, or an acyl group having no aromatic ring;
m represents 1 or 2; when m is 2, the plurality of B and R ₁₁ may be the same or different from each other;
n represents 1 or 2; when n is 2, the plurality of A, B and R ₁₁ may be the same as or different from each other;
L ₁₁ represents a linking group selected from the group consisting of —O—, —S—, —CO—, —CS—, —NR ₂ — or a combination thereof (R ₂ is independently a hydrogen atom or an alkyl group; Represents a group);
R ₁₂ represents an alkyl group, aryl group, cycloalkyl group or heterocyclic group which may have a substituent;
p represents 1 or 2; when p is 2, the plurality of L ₁₁ and R ₁₂ may be the same or different from each other;
R ₁₃ represents a substituent;
q represents an integer of 0 to 4; when q is 2 to 4, a plurality of R ₁₃ may be the same or different from each other)
[2] The optical film according to [1], wherein in the compound represented by the general formula (1), p is 2.
[3] The optical film according to [1] or [2], wherein the compound represented by the general formula (1) is a compound represented by the following general formula (3).

(In general formula (3),
A and B have the same meanings as A and B in the general formula (1);
R ₂₁ represents a hydrogen atom, an alkyl group, or an acyl group having no aromatic ring;
m represents 1 or 2; when m is 2, the plurality of B and R ₂₁ may be the same or different from each other;
n represents 1 or 2; when n is 2, the plurality of A, B and R ₂₁ may be the same or different from each other;
L ₂₁ and L ₂₂ each independently represent a linking group selected from the group consisting of —O—, —S—, —CO—, —CS—, —NR ₂ — or a combination thereof (R ₂ represents Each independently represents a hydrogen atom or an alkyl group);
R ₂₂ and R ₂₄ each independently represents an aryl group, a cycloalkyl group or a heterocyclic group, which may have a substituent;
R ₂₃ represents a substituent;
r represents an integer of 0 to 3 and n + r ≦ 4; when r is 2 or 3, a plurality of R ₂₃ may be the same or different from each other)
[4] The optical system according to any one of [1] to [3], wherein the compound represented by the general formula (1) or (3) has only one aromatic hydrocarbon ring or aromatic heterocyclic ring. the film.
[5] Any of [1] to [4], wherein the compound represented by the general formula (1) or (3) has at least one maximum absorption wavelength in a range of 250 nm to 400 nm in a solution absorption spectrum. An optical film according to any one of the above.
[6] Any one of [1] to [5], wherein the content of the compound represented by the general formula (1) is 1 to 15% by mass with respect to the total of the thermoplastic resin including the cellulose ester. The optical film described in 1.
[7] The optical film according to any one of [1] to [6], wherein an angle formed by an in-plane slow axis of the optical film and a width direction of the optical film is 40 ° or more and 50 ° or less. .
[8] The optical film according to any one of [1] to [7], wherein the total substitution degree of acyl groups of the cellulose ester is 2.0 or more and 2.6 or less.
[9] The optical film according to any one of [1] to [8], wherein the thickness is 10 to 70 μm.

[10] A circularly polarizing plate comprising the optical film according to any one of [1] to [9].
[11] An image display device comprising the circularly polarizing plate according to [10].

  The optical film of the present invention has a high retardation and good reverse wavelength dispersion, and can reduce unevenness in retardation and wavelength dispersion. In addition, the image display device including the optical film of the present invention has high contrast, and color variation can be reduced.

It is a schematic diagram which shows an example of a structure of an organic electroluminescence display. It is a schematic diagram explaining the reflection preventing function by a circularly-polarizing plate. It is a schematic diagram which shows an example of a structure of a liquid crystal display device.

1. Optical film The optical film of this invention contains a cellulose ester and the compound represented by General formula (1).

Cellulose ester Cellulose ester is a compound obtained by esterifying cellulose and at least one of aliphatic carboxylic acid and aromatic carboxylic acid having about 2 to 22 carbon atoms.

  Specific examples of cellulose esters include cellulose mixed acetates such as cellulose triacetate, cellulose diacetate, cellulose propiate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, etc. Is mentioned. The butyryl group that can be contained in the cellulose ester may be linear or branched.

  The total substitution degree of the acyl group of the cellulose ester can be about 1.9 to 3.0. From the viewpoint of improving the retardation development property, the total substitution degree of the acyl group is preferably low. On the other hand, when the degree of substitution is low, the interaction between cellulose esters increases. Therefore, the additive tends to aggregate, and the retardation value in the in-plane direction of the film and the haze unevenness are likely to increase. For this reason, the total substitution degree of the acyl group is more preferably 1.9 to 2.8, and further preferably 2.0 to 2.6.

  The acyl group contained in the cellulose ester preferably has 2 to 6 carbon atoms. Among these, when having an acyl group having 3 or more carbon atoms, the degree of substitution is preferably 0.5 or more, and more preferably 0.8 or more, in order to make the stretchability of the film constant or more. More preferred. On the other hand, in order to ensure the strength of the film, the substitution degree of the acyl group having 3 or more carbon atoms is preferably 2.6 or less, and more preferably 1.0 or less.

  The substitution degree of the acyl group of cellulose ester can be measured by the method prescribed in ASTM-D817-96.

The number average molecular weight of the cellulose ester is preferably in the range of 5 × 10 ^{4 to} 3 × 10 ⁵ in order to increase the mechanical strength of the resulting film, and is preferably 5.5 × 10 ⁴ to 2 × 10 ⁵ . A range is more preferable.

  The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the cellulose ester is preferably 1.0 to 3.0, and more preferably 2.2 to 2.9.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of a cellulose ester are measured using gel permeation chromatography (GPC). The measurement conditions are as follows.
Solvent: methylene chloride;
Column: Three Shodex K806, K805, K803G (made by Showa Denko KK) are connected and used;
Column temperature: 25 ° C .;
Sample concentration: 0.1% by mass;
Detector: RI Model 504 (manufactured by GL Sciences);
Pump: L6000 (manufactured by Hitachi, Ltd.);
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples of Mw = 100000 to 500 is used. Thirteen samples are used at approximately equal intervals.

  The content of residual sulfuric acid in the cellulose ester is preferably in the range of 0.1 to 45 mass ppm in terms of elemental sulfur, and more preferably in the range of 1 to 30 mass ppm. Sulfuric acid is considered to remain in the film in a salt state. When the content of the residual sulfuric acid exceeds 45 ppm by mass, the film tends to break when the film is stretched hot or when slitting is performed after the hot stretch. The residual sulfuric acid content can be measured by a method prescribed in ASTM D817-96.

  The content of free acid in the cellulose ester is preferably 1 to 500 ppm by mass, more preferably 1 to 100 ppm by mass, and further preferably 1 to 70 ppm by mass. When the content of the free acid is in the above range, it is difficult to break when the film is hot stretched or slitted after the hot stretch, as described above. The content of free acid can be measured by the method prescribed in ASTM D817-96.

  Cellulose esters may contain trace amounts of metal components. It is thought that a trace amount metal component originates in the water used in the cellulose ester synthesis process. Like these metal components, the content of components that can become insoluble nuclei is preferably as small as possible. In particular, metal ions such as iron, calcium, and magnesium may form an insoluble matter by forming a salt with a resin decomposition product or the like that may contain an organic acidic group. In addition, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and many ligands. There is a risk of forming an insoluble starch or turbidity.

  Specifically, the content of the iron (Fe) component in the cellulose ester is preferably 1 mass ppm or less. Moreover, content in the calcium (Ca) component in a cellulose ester becomes like this. Preferably it is 60 mass ppm or less, More preferably, it is 30 mass ppm or less. The content of the magnesium (Mg) component in the cellulose ester is preferably 70 mass ppm or less, and particularly preferably 20 mass ppm or less.

  The content of metal components such as iron (Fe) component, calcium (Ca) component, and magnesium (Mg) component is pre-treated by microdigest wet decomposition equipment (sulfuric acid decomposition) and alkali melting After performing, it can measure using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

  The contents of residual alkaline earth metal, residual sulfuric acid and residual acid can be adjusted by thoroughly washing the cellulose ester obtained by synthesis.

  The cellulose ester can be synthesized by a known method, for example, by referring to the method described in JP-A-10-45804. Although the cellulose used as the raw material of the cellulose ester is not particularly limited, it can be cotton linter, wood pulp, kenaf and the like.

  The optical film of the present invention may contain a plurality of cellulose esters of different raw materials. Moreover, the optical film of the present invention may further contain other resins other than the cellulose ester.

  Other resins include cellulose derivatives other than the aforementioned cellulose esters (for example, cellulose ether resins), polycarbonate resins, polystyrene resins, polysulfone resins, polyester resins, polyarylate resins, (meth) acrylic resins. Resin, olefin resin (for example, norbornene resin, cyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin) and the like. Of these, cellulose derivatives, (meth) acrylic resins, polycarbonate resins and cyclic olefin resins are preferred, and cellulose derivatives are more preferred.

Cellulose derivative A cellulose derivative is a compound (compound having a cellulose skeleton) that uses cellulose as a raw material. Examples of cellulose derivatives include cellulose ethers (eg, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, etc.), cellulose ether esters (eg, acetyl methyl cellulose, acetyl ethyl cellulose, acetyl hydroxyethyl cellulose, benzoyl hydroxypropyl cellulose, etc.) , Cellulose carbonate (for example, cellulose ethyl carbonate), cellulose carbamate (for example, cellulose phenylcarbamate) and the like.

(Meth) acrylic resin The (meth) acrylic resin may be a homopolymer of (meth) acrylic acid ester or a copolymer of (meth) acrylic acid ester and another copolymerizable monomer. The (meth) acrylic resin may be one type or a mixture of two or more types.

  The (meth) acrylic acid ester is preferably methyl methacrylate. The content ratio of the structural unit derived from methyl methacrylate in the copolymer is preferably 50% by mass or more, and more preferably 70% by mass or more.

  Examples of copolymer monomers that form a copolymer with methyl methacrylate include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl moiety; alkyl acrylates having 1 to 18 carbon atoms in the alkyl moiety; and a lactone ring structure described below. Obtained alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl moiety having a hydroxy group (hydroxyl group); α, β-unsaturated acids such as acrylic acid and methacrylic acid; maleic acid, fumaric acid, itaconic acid and the like Unsaturated group-containing divalent carboxylic acids; aromatic vinyl compounds such as styrene and α-methylstyrene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted maleimide, glutaric acid Acrylamide derivatives such as anhydrides and acryloylmorpholine (ACMO); N-vinylpyrrolidone ( VP) and the like. These may be used alone or in combination of two or more.

  Of these, alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate; Alkyl (meth) acrylates having a hydroxy group such as methyl (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferred. In order to enhance the compatibility with the cellulose ester, acryloylmorpholine and the like are preferable.

The (meth) acrylic resin preferably contains a lactone ring structure from the viewpoint of enhancing the heat resistance of the obtained optical film or adjusting the photoelastic coefficient. The lactone ring structure contained in the (meth) acrylic resin is preferably represented by the following general formula (A).

In the formula (A), R ^{1 to} R ³ each independently represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. Examples of the organic residue include a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, an —OAc group (Ac is an acetyl group), a —CN group, and the like.

The lactone ring structure represented by the formula (A) is a structure derived from an alkyl (meth) acrylate having a hydroxy group, as will be described later. The (meth) acrylic resin containing a lactone ring structure further contains a structural unit derived from an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl portion, and if necessary, a monomer containing a hydroxy group, unsaturated A structural unit derived from a carboxylic acid, a monomer represented by the general formula (B), or the like may be further included.

R ⁴ in the formula (B) represents a hydrogen atom or a methyl group. X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, -OAc group (Ac is an acetyl group), -CN group, acyl group or -C-OR group (R is a hydrogen atom or 1 to 20 organic residues).

  The content ratio of the lactone ring structure represented by the general formula (A) in the (meth) acrylic resin containing a lactone ring structure is preferably in the range of 5 to 90% by mass, more preferably 10 to 80% by mass. %, And more preferably in the range of 15 to 70% by mass. When the content of the lactone ring structure is 5% by mass or more, a film having a necessary retardation is easily obtained, and the heat resistance, solvent resistance, and surface hardness of the film are sufficient. When the content of the lactone ring structure is 90% by mass or less, the moldability is high, and the flexibility of the obtained film tends to be high.

  The content ratio of the structural unit derived from the alkyl (meth) acrylate in the (meth) acrylic resin containing a lactone ring structure is preferably in the range of 10 to 95% by mass, more preferably 20 to 90% by mass. It is in the range, and more preferably in the range of 30 to 85% by mass.

  In the (meth) acrylic resin containing a lactone ring structure, the content ratio of the structural unit derived from the hydroxy group-containing monomer, the unsaturated carboxylic acid, or the monomer represented by the general formula (B) is preferably independently 0. It is in the range of -30 mass%, More preferably, it is 0-20 mass%, More preferably, it exists in the range of 0-10 mass%.

  A (meth) acrylic resin containing a lactone ring structure is polymerized by a monomer component containing at least an alkyl (meth) acrylate having a hydroxy group and another alkyl (meth) acrylate to form a hydroxy group in the molecular chain. It can be produced through a step of obtaining a polymer having a group and an ester group, and a step of introducing a lactone ring structure by heat-treating the obtained polymer.

The weight average molecular weight Mw of the (meth) acrylic resin is preferably in the range of 8.0 × 10 ^{4 to} 5.0 × 10 ⁵ , more preferably 9.0 × 10 ^{4 to} 4.5 × 10 ⁵ . It is in the range, and more preferably in the range of 1.0 × 10 ^{5 to} 4.0 × 10 ⁵ . If the weight average molecular weight Mw of the (meth) acrylic resin is 8.0 × 10 ⁴ or more, the brittleness resistance of the film is easily improved, and if it is 5.0 × 10 ⁵ or less, the haze of the film tends to be low.

  The weight average molecular weight Mw of the (meth) acrylic resin can be measured by gel permeation chromatography in the same manner as the method for measuring the weight average molecular weight Mw of the cellulose ester.

  The content of the other resin with respect to the total amount of the cellulose ester and the other resin is preferably about 5 to 70% by mass.

About the compound represented by the general formula (1) The optical film of the present invention is characterized by containing at least one compound represented by the general formula (1).

  D in the general formula (1) represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring.

  The aromatic hydrocarbon ring may be a single ring or a condensed ring, but is preferably a single ring. Preferred examples of the aromatic hydrocarbon ring include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzopyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, fluoranthene ring, fluorene ring, etc. More preferably, it is a benzene ring.

  The non-aromatic hydrocarbon ring may be a single ring or a condensed ring, but is preferably a single ring. Preferred examples of the non-aromatic hydrocarbon ring include cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclobutene ring, cyclopentene ring, cyclohexene ring, cycloheptene ring, cyclooctene ring, Examples thereof include an adamantane ring, a bicyclononane ring, a norbornane ring, a norbornene ring, a cyclonorbornene ring, a dicyclopentadiene ring, a hydrogenated naphthalene ring, and a hydrogenated biphenyl ring. Of these, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclonorbornene ring, and the like are more preferable.

  The aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, but is preferably a monocyclic ring. Preferred examples of the aromatic heterocycle include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, azacarbazole ring (azacarbazole ring) Is one in which at least one carbon atom constituting the carbazole ring is replaced with a nitrogen atom), triazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, fluropyrrole ring, Furofuran ring, thienofuran ring, benzoisoxazole ring, benzothiazole ring, benzoxazole ring, benzisothiazole ring, benzimidazole ring, indoline ring, isoindoline-1,3-dione ring, pyridine ring, pyrazine ring, pyridazine ring, Limidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, silole ring, dibenzofuran ring, dibenzothiophene ring, dibenzocarbazole ring, benzodifuran Ring, benzodithiophene ring, phenanthroline ring, acridine ring, benzoquinoline ring, phenazine ring, phenanthridine ring, cyclazine ring, kindrin ring, tepenidine ring, quinindrine ring, triphenodithiazine ring, triphenodioxazine ring, phenant Includes azine ring, anthrazine ring, perimidine ring, naphthofuran ring, naphthothiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, anthrathiophene ring, etc. . Of these, a pyridine ring, a benzothiazole ring, a benzoxazole ring, and the like are more preferable.

  The non-aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, and is preferably a monocyclic ring. Preferred examples of the non-aromatic heterocycle include tetrahydrofuran ring, tetrahydropyran ring, dioxolane ring, dioxane ring, pyrrolidine ring, pyridone ring, pyridazinone ring, imide ring, piperidine ring, dihydropyrrole ring, dihydropyridine ring, tetrahydropyridine ring, Piperazine ring, morpholine ring, dihydrooxazole ring, dihydrothiazole ring, piperidine ring, aziridine ring, azetidine ring, azepine ring, azepan ring, imidazolidine ring, diazepine ring, tetrahydrothiophene ring and the like are included. Of these, a pyridone ring, an imide ring, a pyrrolidine ring and the like are more preferable.

  Among these, D in the general formula (1) is preferably an aromatic hydrocarbon ring or an aromatic heterocyclic ring, more preferably an aromatic hydrocarbon ring, and particularly preferably a benzene ring.

A in the general formula (1) is a divalent group selected from the group consisting of a single bond, —O—, —S—, —CO—, —CS—, —NR ₁ —, an alkylene group, an alkenylene group, or a combination thereof. Represents a linking group. Examples of combinations of two or more groups described above include —CO—O—, —CS—O—, —O—CO—, —O—CS—, —CH═C (—CO—O—) ₂ —. , —CO—NR ₁ — and the like. Two or more groups to be combined may be the same or different from each other. Two or more groups to be combined may be bonded via an alkyl group or an aryl group.

In order to increase the reverse wavelength dispersion of the compound represented by the general formula (1), the compound preferably has at least one linking group having a conjugated system or electron-withdrawing linking group. Therefore, A is preferably an alkenylene group, —O—, —CO—, —CS—, —CO—O—, —CS—O—, or —CO—NR ₁ —, wherein —CO—, — More preferably, it is CO—O— or —CO—NR ₁ —.

R ₁ in —NR ₁ — may be a hydrogen atom or a substituent. Examples of the substituent represented by R ₁ include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), a cycloalkyl group. (Cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidinyl) Group, 2-benzothiazolyl group, 2-pyridyl group and the like), cyano group and the like, preferably an alkyl group, more preferably a methyl group or an ethyl group.

B in the general formula (1) represents a linking group represented by the following general formula (2).
General formula (2)

  R in the general formula (2) represents an alkylene group. The alkylene group may be linear or branched. The number of carbon atoms of the alkylene group is preferably 1-6, and more preferably 2-3. Examples of the alkylene group include methylene group, ethylene group, propylene group, isopropylene group, butylene group, isobutylene group and the like.

  Among these, an alkylene group having relatively low hydrophobicity is preferable from the viewpoint of easy interaction with the cellulose ester. For this reason, the alkylene group is preferably an ethylene group or a propylene group, and a propylene group having a branched structure is more preferable from the viewpoint of suppressing aggregation of the compound.

  L in the general formula (2) is preferably an integer of 2 to 10, more preferably an integer of 2 to 5, and particularly preferably 2 or 3. When l exceeds 10, the interaction between the cellulose ester and the linking group B may be too large. Thereby, the orientation of the compound represented by the general formula (1) is lowered, and the effect of the present invention may not be obtained.

R _{11 in the} general formula (1) represents a hydrogen atom, an alkyl group, or an acyl group having no aromatic ring. When the acyl group has an aromatic group, the retardation of the film and the unevenness of wavelength dispersion cannot be sufficiently suppressed. This is because the aromatic group contained in the acyl group interacts hydrophobically, and the compounds represented by the general formula (1) form an aggregate, whereby the compound represented by the general formula (1) This is probably because the cellulose ester is less likely to interact with the linking group B.

  It is preferable that carbon number of an alkyl group is 1-10, and it is more preferable that it is 1-3. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, an isobutyl group, a pentyl group, a hexyl group, and a 2-ethylhexyl group, and preferably a methyl group, an ethyl group, or a propyl group. It is a group.

  The number of carbon atoms in the acyl group having no aromatic ring is preferably 2-15, and more preferably 2-9. Examples of the acyl group having no aromatic group include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a 2-ethylhexanoyl group, and the like, and preferably an acetyl group, a propionyl group, and an isobutyryl group.

M in the general formula (1) represents 1 or 2. When m is 2, the plurality of B and R ₁₁ may be the same as or different from each other. n represents 1 or 2. When n is 2, the plurality of A, B, and R ₁₁ may be the same as or different from each other.

L _{11 in the} general formula (1) represents a divalent linking group selected from the group consisting of —O—, —S—, —CO—, —CS—, —NR ₂ — or a combination thereof. Examples of combinations of two or more groups described above include —O—CO—, —CO—O—, —O—CS—, —CS—O—, —NR ₃ —CO—, and —CO—NR ₃ —. Etc. are included. Two or more groups to be combined may be the same or different from each other. Two or more groups to be combined may be bonded via an alkyl group or an aryl group.

The linking group represented by L ₁₁ of the compound represented by the general formula (1) can impart orientation to the compound represented by the general formula (1) by interacting with the cellulose ester. Therefore, the linking group represented by L ₁₁ is preferably a polarized group. Specifically, the linking group represented by L ₁₁ is —O—, —CO—, —CO—O—, —O—CO—, —CO—NR ₂ — or —NR ₂ —CO—. Of these, —CO—O—, —O—CO—, —CO—NR ₂ — or —NR ₂ —CO— is more preferable.

R ₂ in —NR ₂ — may independently be a hydrogen atom or a substituent. Examples of the substituent represented by R ₂ include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), a cycloalkyl group. (Cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidinyl) Group, 2-benzothiazolyl group, 2-pyridyl group and the like), cyano group and the like. An alkyl group is preferable, and a methyl group or an ethyl group is particularly preferable.

R _{12 in the} general formula (1) represents an alkyl group, an aryl group, a cycloalkyl group, or a heterocyclic group, which may have a substituent.

  It is preferable that carbon number of an alkyl group is 1-20. Examples of the alkyl group include a decanyl group and the like.

  The aryl group is preferably an aryl group having 6 to 20 carbon atoms. Examples of the aryl group include a substituted or unsubstituted phenyl group, a naphthyl group, etc., preferably a substituted or unsubstituted phenyl group, more preferably a substituted phenyl group, particularly preferably 4 It is a phenyl group having a substituent at the position. As the heterocyclic group, a heteroaryl group having 4 to 20 carbon atoms is preferable.

  The cycloalkyl group is preferably a cycloalkyl group having 4 to 8 carbon atoms. Examples of the cycloalkyl group include a substituted or unsubstituted cyclohexyl group, a cyclopentyl group, etc., preferably a substituted or unsubstituted cyclohexyl group, more preferably a substituted cyclohexyl group, still more preferably. It is a cyclohexyl group having a substituent at the 4-position.

Among these, in order to obtain a certain degree of orientation, R ₁₂ is preferably an aryl group, a cycloalkyl group or a heterocyclic group which may have a substituent, and may have a substituent. An aryl group and a heterocyclic group are more preferable.

Examples of substituents that the alkyl group, aryl group and heteroaryl group may have include
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.);
An alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.);
A cycloalkyl group (a cyclohexyl group, a cyclopentyl group, a 4-n-dodecylcyclohexyl group, etc.);
Alkenyl group (vinyl group, allyl group, etc.);
Cycloalkenyl groups (such as 2-cyclopenten-1-yl and 2-cyclohexen-1-yl groups), alkynyl groups (such as ethynyl groups and propargyl groups);
An aryl group (phenyl group, p-tolyl group, naphthyl group, etc.);
Heteroaryl groups (2-furyl, 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl, 2-pyridyl, etc.);
A cyano group;
A hydroxy group;
A nitro group;
A carboxy group;
An alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.);
Aryloxy groups (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.);
An acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.);
An amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.);
An acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.);
Alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.);
A mercapto group;
Alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.);
An arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.);
Sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N -(N 'phenylcarbamoyl) sulfamoyl group etc.);
A sulfo group;
An acyl group (acetyl group, pivaloylbenzoyl group, etc.);
A carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) and the like are included.

P in the general formula (1) represents 1 or 2. The compound represented by the general formula (1) has orientation because L ₁₁ interacts with the cellulose ester. Therefore, p is preferably 2. When p is 2, the plurality of L ₁₁ and R ₁₂ may be the same as or different from each other. The two groups represented by-(L ₁₁ -R ₁₂ ) may be at the substitution positions at the p-position, 1-position or 4-position of the ring represented by D to enhance the orientation of the compound. preferable.

R _{13 in the} general formula (1) represents a substituent. Examples of the substituent include the same substituents represented by R ₁₂ described above, and preferably an alkyl group or an alkyloxy group.

Q of General formula (1) represents the integer of 0-4. When q is 2 to 4, the plurality of R ₁₃ may be the same as or different from each other.

As described above, in the compound represented by the general formula (1), it is preferable that p is 2 because L ₁₁ exhibits orientation by interacting with the cellulose ester. Further, in order to enhance the orientation, two groups represented by-(L ₁₁ -R ₁₂ ) may be in substitution positions at the p-position, 1-position or 4-position of the ring represented by D. preferable. Therefore, the compound represented by the general formula (1) is preferably a compound represented by the following general formula (3).

A and B in the general formula (3) have the same meanings as A and B in the general formula (1), respectively. R _{21 in the} general formula (3) has the same meaning as R _{11 in the} general formula (1). M and n in the general formula (3) have the same meanings as m and n in the general formula (1), respectively.

L ₂₁ and L ₂₂ in the general formula (3) have the same meaning as L _{11 in the} general formula (1). R ₂₂ and R ₂₄ in the general formula (3) have the same meaning as R _{12 in the} general formula (1).

R _{23 in the} general formula (3) has the same meaning as R _{13 in the} general formula (1). R in the general formula (3) represents an integer of 0 to 3 and satisfies n + r ≦ 4. When r is 2 or 3, the plurality of R ₂₃ may be the same as or different from each other.

  From the standpoint of achieving both retardation development and wavelength dispersion, the compound represented by the general formula (1) or (3) may have a total number of aromatic hydrocarbon rings or aromatic heterocycles of 7 or less. Preferably there is only one. When the compound represented by the general formula (1) or (3) has 8 or more aromatic hydrocarbon rings or aromatic heterocycles, the reverse wavelength dispersibility tends to decrease as the retardation increases. There is.

Specific examples of the compound represented by the general formula (1) are shown below. The compound represented by the general formula (1) is not limited by the following specific examples. First, the example in case the coupling group shown by A contains an alkenylene group is shown.

Next, the example in case the coupling group shown by A contains -CO- or -CS- is shown.

Next, the example in case the coupling group shown by A contains -O- is shown.

Next, the example in case the coupling group shown by A is a single bond is shown.

  In the specific example of the compound represented by the general formula (1), when geometric isomers (trans isomer and cis isomer) exist, either isomer may be used unless otherwise specified. A trans isomer is preferable to a cis isomer because of higher phase difference expression.

  The compound represented by the general formula (1) thus configured exhibits high retardation and good reverse wavelength dispersion. In addition, since the compound represented by the general formula (1) has an alkyleneoxy group derived from B, the interaction between cellulose ester molecules is adjusted without impairing the orientation, and the cellulose ester is flexible. Or can be granted. As a result, as will be described later, it is possible to suppress the retardation unevenness and wavelength dispersion unevenness of the film after being stretched at a high magnification in an oblique direction.

The compound represented by the general formula (1) or (3) can be synthesized by a known method. For example, the exemplary compound A1 can be synthesized according to the following scheme.

  In a reaction vessel equipped with an ester tube, 125 ml of toluene, 12.5 g (0.12 mol) of malonic acid, 31.7 g (0.26 mol) of diethylene glycol monomethyl ether and 11.42 g of p-toluenesulfonic acid monohydrate are charged. Then, the mixture is stirred for 5 hours while heating under reflux in a nitrogen atmosphere. As the reaction progresses, water is distilled off. Thereafter, the solvent is distilled off from the resulting reaction solution under reduced pressure, and the residue is purified by silica gel chromatography (ethyl acetate / heptane) to obtain 27.7 g of compound (l). The yield is 75% based on malonic acid.

  To 200 ml of N, N-dimethylformamide, 6.9 g (0.05 mol) of 2,5-dihydroxybenzaldehyde, 31.6 g (0.11 mol) of the compound (m), 13.8 g of potassium carbonate and 3.3 g of potassium iodide were added. In addition, the mixture is stirred at 100 ° C. for 5 hours under a nitrogen atmosphere. After cooling the reaction mixture, water and ethyl acetate are added for extraction. The solvent is distilled off from the organic layer under reduced pressure, and the resulting crude crystals are purified by silica gel chromatography (ethyl acetate / heptane) to obtain 13.2 g of compound (n). The yield is 48% based on 2,5-dihydroxybenzaldehyde.

  A reaction vessel equipped with an ester tube was charged with 50 ml of toluene, 5.5 g (0.01 mol) of compound (n), 3.1 g (0.01 mol) of compound (l) and 1.5 g of piperidine, and in a nitrogen atmosphere, Stir for 5 hours while heating to reflux. As the reaction progresses, water is distilled off. The resulting reaction solution is cooled, and extracted by adding water and ethyl acetate. The solvent is distilled off from the organic layer under reduced pressure, and the resulting crude crystals are purified by silica gel chromatography (ethyl acetate / heptane) to obtain 6.1 g of exemplary compound A1. The yield is 72% based on the compound (n).

The compound represented by the general formula (1) preferably has an absorption maximum wavelength at 250 nm to 400 nm in the solution absorption spectrum from the viewpoint of imparting sufficient reverse wavelength dispersibility to the film. The maximum absorption wavelength is the absorption wavelength of a solution obtained by dissolving the compound represented by the general formula (1) in tetrahydrofuran (not including a polymerization inhibitor) at a concentration of 1.0 × 10 ⁻⁵ mol / L. The maximum point of the absorption peak when measured at 25 ° C. with an absorption spectrophotometer. The maximum absorption wavelength is not necessarily the maximum absorption wavelength, and a plurality of maximum points may exist.

  If the maximum absorption wavelength is less than 250 nm, the effect of improving wavelength dispersion is small, and if the maximum absorption wavelength is more than 400 nm, the film is likely to be colored, so the amount added needs to be limited. When the compound represented by the general formula (1) has a maximum absorption wavelength between 250 nm and 400 nm, the compound can have sufficient reverse wavelength dispersion.

  The content of the compound represented by the general formula (1) is appropriately set to such an extent that the required wavelength dispersion adjusting ability and phase difference can be imparted. Specifically, the content of the compound represented by the general formula (1) is preferably 1 to 15% by mass, and preferably 1.5 to 10% by mass with respect to the total thermoplastic resin. More preferably, it is 1.5-5 mass%. The thermoplastic resin refers to a resin that is a main component such as the aforementioned cellulose ester. When the content of the compound is less than 1% by mass, it is difficult to obtain desired retardation development and wavelength dispersion adjusting function. If it exceeds 15% by mass, the optical film tends to bleed out. When the content of the compound is within the above range, sufficient wavelength dispersibility and high retardation can be imparted to the optical film of the present invention.

  The optical film of the present invention may further contain various additives as required.

(Sugar ester compound)
The optical film of the present invention can further contain a sugar ester compound other than the cellulose ester described above from the viewpoint of improving the plasticity of the optical film.

The sugar ester compound may be a compound having 1 to 12 furanose structures or pyranose structures, in which all or part of the hydroxy groups in the compound are esterified. Preferable examples of such sugar ester compounds include sucrose esters represented by the following general formula (FA).

R _{1 to} R _{8 in} formula (FA) each independently represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group. R _{1 to} R ₈ may be the same as or different from each other.

  The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of the substituted or unsubstituted alkylcarbonyl group include a methylcarbonyl group (acetyl group). Examples of the substituent that the alkyl group has include an aryl group such as a phenyl group.

  The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of the arylcarbonyl group include a phenylcarbonyl group. Examples of the substituent that the aryl group has include an alkyl group such as a methyl group, an alkoxyl group such as a methoxy group, and the like.

  The average substitution degree of the acyl group of the sucrose ester is preferably in the range of 3.0 to 7.5. When the average substitution degree of the acyl group is within this range, sufficient compatibility with the cellulose ester is easily obtained.

Specific examples of the sucrose ester represented by the general formula (FA) include the following exemplary compounds (FA-1) to (FA-24). The table below, the _R 1 to R ₈ in the general formula of the exemplified compound (FA-1) ~ (FA -24) (FA), shows the average degree of substitution of acyl groups.

  Examples of other sugar ester compounds include those described in JP-A Nos. 62-42996 and 10-237084.

  The content of the sugar ester compound is preferably 0.5 to 35.0% by mass and more preferably 5.0 to 30.0% by mass with respect to the cellulose ester.

  The optical film of the present invention may further contain a plasticizer in order to improve the fluidity of the composition during film production and the flexibility of the film. Examples of plasticizers include polyester plasticizers, polyhydric alcohol ester plasticizers, polycarboxylic acid ester plasticizers (including phthalate ester plasticizers), glycolate plasticizers, ester plasticizers ( Citrate ester plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, trimellitic ester plasticizers, etc.). These may be used alone or in combination of two or more.

  The polyester plasticizer is a compound obtained by reacting a 1-4 carboxylic acid and a 1-6 valent alcohol, preferably a compound obtained by reacting a divalent carboxylic acid with a glycol. It is.

  Examples of the divalent carboxylic acid include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. In particular, a compound using adipic acid, phthalic acid or the like as the divalent carboxylic acid can impart good plasticity.

  Examples of glycols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol and the like. included. Each of the divalent carboxylic acid and glycol may be one kind, or two or more kinds may be used in combination.

  The polyester plasticizer may be any of ester, oligoester, and polyester. The molecular weight of the polyester plasticizer is preferably in the range of 100 to 10000, and more preferably in the range of 600 to 3000 since the effect of imparting plasticity is great.

  The viscosity of the polyester plasticizer depends on the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the compatibility with the cellulose ester is high and the effect of imparting plasticity is high. It is preferably in the range of s (25 ° C.). The polyester plasticizer may be used alone or in combination of two or more.

  The polyhydric alcohol ester plasticizer is an ester compound (alcohol ester) of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, preferably a 2-20 valent aliphatic polyhydric alcohol ester. The polyhydric alcohol ester compound preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  Examples of the aliphatic polyhydric alcohol include ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol and the like.

  The monocarboxylic acid can be an aliphatic monocarboxylic acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, or the like. One type of monocarboxylic acid may be sufficient and a 2 or more types of mixture may be sufficient as it. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The number of carbon atoms of the aliphatic monocarboxylic acid is more preferably 1-20, and still more preferably 1-10. Examples of such aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, and the like, and acetic acid may be preferable in order to enhance compatibility with the cellulose ester.

  Examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and the like.

  Examples of aromatic monocarboxylic acids include: benzoic acid; one having 1 to 3 alkyl groups or alkoxy groups (for example, methoxy group or ethoxy group) introduced into the benzene ring of benzoic acid (for example, toluic acid); benzene ring Aromatic monocarboxylic acids having two or more (for example, biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, etc.) are included, and benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. In order to make it hard to volatilize, the one where molecular weight is larger is preferable. In order to improve moisture permeability and compatibility with the cellulose ester, a smaller molecular weight is preferable.

  Specific examples of the polyhydric alcohol ester plasticizer include trimethylolpropane triacetate, pentaerythritol tetraacetate, ester compound (A) represented by the general formula (I) described in JP-A-2008-88292, and the like. It is.

  The polycarboxylic acid ester plasticizer is an ester compound of a divalent or higher, preferably 2-20 valent polycarboxylic acid and an alcohol compound. The polyvalent carboxylic acid is preferably a 2-20 valent aliphatic polyvalent carboxylic acid, a 3-20 valent aromatic polyvalent carboxylic acid, or a 3-20 valent alicyclic polyvalent carboxylic acid.

  Examples of the polyvalent carboxylic acids include trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid or derivatives thereof; Contains aliphatic polycarboxylic acids such as fumaric acid, maleic acid and tetrahydrophthalic acid; oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid and citric acid, etc., and suppresses volatilization from the film. For this, oxypolycarboxylic acids are preferred.

  Examples of the alcohol compound include an aliphatic saturated alcohol compound having a straight chain or a side chain, an aliphatic unsaturated alcohol compound having a straight chain or a side chain, an alicyclic alcohol compound, an aromatic alcohol compound, and the like. Carbon number of an aliphatic saturated alcohol compound or an aliphatic unsaturated alcohol compound becomes like this. Preferably it is 1-32, More preferably, it is 1-20, More preferably, it is 1-10. Examples of the alicyclic alcohol compound include cyclopentanol, cyclohexanol and the like. Examples of the aromatic alcohol compound include phenol, paracresol, dimethylphenol, benzyl alcohol, cinnamyl alcohol and the like. One kind of alcohol compound may be used, or a mixture of two or more kinds may be used.

  The molecular weight of the polycarboxylic acid ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. A larger molecular weight of the polyvalent carboxylic acid ester plasticizer is preferable from the viewpoint of suppressing bleeding out. From the viewpoint of moisture permeability and compatibility with cellulose ester, a smaller one is preferable.

  The acid value of the polyvalent carboxylic acid ester plasticizer is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. The acid value refers to the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxy group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

  Examples of the polycarboxylic acid ester plasticizer include an ester compound (B) represented by the general formula (II) described in JP-A-2008-88292.

  The polyvalent carboxylic acid ester plasticizer may be a phthalic acid ester plasticizer. Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like.

  Examples of glycolate plasticizers include alkylphthalyl alkyl glycolates. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate and the like. .

  The ester plasticizer includes a fatty acid ester plasticizer, a citrate ester plasticizer, a phosphate ester plasticizer, a trimellitic acid plasticizer, and the like.

  Examples of the fatty acid ester plasticizer include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and the like. Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate and the like. Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like. Examples of trimellitic acid plasticizers include octyl trimellitic acid, n-octyl trimellitic acid, isodecyl trimellitic acid, and isononyl trimellitic acid.

  It is preferable that content of a plasticizer is 0.5-30.0 mass% with respect to a cellulose ester. If the content of the plasticizer is 30.0% by mass or less, the optical film hardly causes bleed out.

(UV absorber)
The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber may be benzotriazole, 2-hydroxybenzophenone, salicylic acid phenyl ester, or the like. Specifically, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- Triazoles such as (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4 -Benzophenones such as methoxybenzophenone.

  Especially, the ultraviolet absorber whose molecular weight is 400 or more is hard to volatilize at a high boiling point, and is not easily scattered during high temperature molding. Therefore, even if the addition amount is relatively small, weather resistance can be imparted to the obtained film.

Examples of ultraviolet absorbers having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- Benzotriazoles such as (1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol];
Hindered amines such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate;
2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy]- A hybrid system having both hindered phenol and hindered amine structures in the molecule such as 2,2,6,6-tetramethylpiperidine;
Preferably, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole or 2,2-methylenebis [4- (1,1,3, 3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol]. These may be used alone or in combination of two or more.

(Fine particles)
The optical film of the present invention may contain fine particles composed of an inorganic compound or an organic compound.

  Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate , Calcium phosphate and the like.

  Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine Resin, polyolefin-based powder, polyester-based resin, polyamide-based resin, polyimide-based resin, pulverized classification of organic polymer compound (polyfluorinated ethylene-based resin, starch, etc.), polymer compound synthesized by suspension polymerization method, spray drying High molecular compounds made spherical by the method or dispersion method are included.

  The fine particles can be composed of a compound containing silicon, preferably silicon dioxide, from the viewpoint that the haze of the obtained film can be kept low.

  Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.) and the like. Among these, Aerosil 200V and Aerosil R972V are particularly preferable because they can increase the slipperiness of the film surface while keeping the haze of the optical film low. Examples of the fine particles of zirconium oxide include Aerosil R976, R811 (manufactured by Nippon Aerosil Co., Ltd.) and the like.

  Examples of the polymer compound include a silicone resin, a fluororesin, a (meth) acrylic resin, and the like, preferably a silicone resin, and more preferably a silicone resin having a three-dimensional network structure. Examples of such silicone resins include Tospearl 103, 105, 108, 120, 145, 3120, 240 (above, manufactured by Toshiba Silicone Co., Ltd.) and the like.

  The average particle diameter of the primary particles of the fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. The fine particles may mainly form secondary aggregates having a particle size in the range of 0.05 to 0.30 μm. If the average particle size of the fine particles is in the range of 100 to 400 nm, they can exist as primary particles without agglomeration.

  It is preferable to contain fine particles so that the dynamic friction coefficient of at least one surface of the optical film is in the range of 0.2 to 1.0.

  The content of the fine particles is preferably in the range of 0.01 to 1.00% by mass, more preferably in the range of 0.05 to 0.50% by mass with respect to the cellulose ester.

(Dispersant)
The optical film of the present invention may further contain a dispersant from the viewpoint of enhancing the dispersibility of the fine particles. The dispersant is one or more selected from amine-based dispersants and carboxy group-containing polymer dispersants.

  The amine dispersant is preferably an alkylamine or an amine salt of polycarboxylic acid, for example, polyester acid, polyether ester acid, fatty acid, fatty acid amide, polycarboxylic acid, alkylene oxide, polyalkylene oxide, polyoxyethylene fatty acid. It may be a compound obtained by aminating an ester, polyoxyethylene glycerin fatty acid ester or the like. Examples of amine salts include amidoamine salts, aliphatic amine salts, aromatic amine salts, alkanolamine salts, polyvalent amine salts and the like.

  Specific examples of the amine dispersant include polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, tripropylamine, diethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine and the like. Examples of commercially available products include Solspers series (manufactured by Lubrizol), Ajisper series (manufactured by Ajinomoto Co., Inc.), BYK series (manufactured by Big Chemie), EFKA series (manufactured by EFKA), and the like.

  The carboxy group-containing polymer dispersant is preferably a polycarboxylic acid or a salt thereof, and may be, for example, polycarboxylic acid, ammonium polycarboxylate, sodium polycarboxylate, or the like. Specific examples of the carboxy group-containing polymer dispersant include polyacrylic acid, ammonium polyacrylate, sodium polyacrylate, ammonium polyacrylate copolymer, polymaleic acid, ammonium polymaleate, sodium polymaleate and the like.

  The amine-based dispersant and the carboxy group-containing polymer dispersant may be used after being dissolved in a solvent component, or may be commercially available.

The content of the dispersant is preferably 0.2% by mass or more based on the fine particles, although it depends on the type of the dispersant. When the content of the dispersant is 0.2% by mass or more with respect to the fine particles, the dispersibility of the fine particles can be sufficiently improved.
When the optical film of the present invention further contains a surfactant or the like, adsorption of the dispersant to the surface of the fine particles is less likely to occur than the surfactant, and the fine particles may be easily reaggregated. Since the dispersant is expensive, its content is preferably as small as possible. On the other hand, when the content of the dispersant is too small, poor wettability of fine particles and a decrease in dispersion stability are likely to occur. Therefore, the content of the dispersant when the optical film of the present invention further contains a surfactant or the like can be about 0.05 to 10.00 parts by mass with respect to 10.00 parts by mass of the fine particles.

(Phase difference control agent)
The optical film of the present invention may further contain a retardation control agent that imparts optical compensation capability in order to improve the display quality of the image display device.

  Examples of the retardation control agent include aromatic compounds having two or more aromatic rings as described in European Patent No. 911,656A2, and rod-like compounds described in JP-A-2006-2025. included. Two or more aromatic compounds may be used in combination. The aromatic ring of this aromatic compound is preferably an aromatic hydrocarbon ring or an aromatic heterocycle. The aromatic heterocycle is generally an unsaturated heterocycle; and preferably 1,3,5-triazine ring described in JP-A-2006-2026.

  The addition amount of the retardation control agent is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 1 to 10% by mass with respect to 100% by mass of the resin constituting the film. .

  The optical film of the present invention may further have a liquid crystal layer through an alignment film. Thereby, the optical film of the present invention can have a function as a polarizing plate protective film and a retardation adjustment function derived from the liquid crystal layer.

(Other additives)
The optical film of the present invention may further contain an antioxidant, an antistatic agent, a flame retardant and the like for preventing thermal decomposition during molding and coloring due to heat.

  Phosphorus flame retardants include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphate ester, One or more kinds selected from halogen condensed phosphoric acid ester, halogen-containing condensed phosphonic acid ester, halogen-containing phosphorous acid ester and the like can be mentioned. Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) phosphate. , Tris (tribromoneopentyl) phosphate, and the like.

Physical Properties of Optical Film The optical film of the present invention preferably has an in-plane retardation value R0 (550) measured at a wavelength of 550 nm under the condition of 23 ° C. and 55% RH and satisfies the following (a): .
(A) 110 nm ≦ R0 (550) ≦ 170 nm

  An optical film in which R0 (550) satisfies the following range can preferably function as, for example, a λ / 4 retardation film. The optical film of the present invention preferably satisfies 120 nm ≦ R0 (550) ≦ 160 nm, and more preferably satisfies 130 nm ≦ R0 (550) ≦ 150 nm.

  In the optical film of the present invention, the retardation value Rth (550) in the thickness direction measured at a wavelength of 550 nm under the condition of 23 ° C. and 55% RH preferably satisfies 50 nm ≦ Rth (550) ≦ 250 nm.

When the retardation values in the in-plane direction measured at wavelengths of 450 nm and 650 nm under conditions of 23 ° C. and 55% RH are R0 (450) and R0 (650), respectively, the optical film of the present invention has the following ( It is preferable that b) and (c) are further satisfied.
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.03
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.03

  An optical film in which R0 (450) / R0 (550) or R0 (550) / R0 (650) satisfies the above range can preferably function as a retardation film for light in a wide wavelength region, for example. Further, light leakage or the like when the display device displays black can be reduced. In particular, when (b) 0.72 ≦ R0 (450) / R0 (550) ≦ 0.96 is satisfied, blue reproducibility is high; (c) 0.83 ≦ R0 (550) / R0 (650) ≦ It is more preferable to satisfy 0.97 because red reproducibility is high.

R0 and Rt are defined by the following formulas (I) and (II), respectively.
Formula (I): R0 = (nx−ny) × d
Formula (II): Rt = {(nx + ny) / 2−nz} × d
[In the formulas (I) and (II), nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the optical film. ny represents the refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the optical film. nz represents the refractive index in the thickness direction z of the optical film. d represents the film thickness (nm) of the optical film. )

R0 and Rt can be measured using an automatic birefringence meter, for example, AxoScan manufactured by Axometric, and KOBRA-21ADH manufactured by Oji Scientific Instruments. When using AxoScan, specifically, it can be measured by the following method.
1) Condition the optical film at 23 ° C. and 55% RH. The average refractive index of the optical film after humidity adjustment at each of wavelengths of 450 nm, 550 nm and 650 nm is measured using an Abbe refractometer and a spectral light source. Moreover, the film thickness d (nm) of an optical film is measured using a film thickness meter.
2) Retardation values R0 (450) and R0 (550) in the in-plane direction when light having a wavelength of 450 nm, 550 nm or 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface. And R0 (650) are measured with an AxoScan. The measurement is performed under conditions of 23 ° C. and 55% RH.
3) Check the in-plane slow axis of the optical film by AxoScan. When light having wavelengths of 450 nm, 550 nm, and 650 nm is incident from an angle of φ (incident angle (φ)) with respect to the normal of the surface of the optical film, with the confirmed slow axis as the tilt axis (rotation axis) The retardation value R (φ) is measured. R (φ) can be measured at 6 points every 10 ° in the range of 0 to 50 °. The measurement is performed under conditions of 23 ° C. and 55% RH.
4) R0 (450), R0 (550) and R0 (650) measured in 2) above, R (φ) measured in each wavelength of 450 nm, 550 nm or 650 nm in 3) above, and 1) above Nx, ny and nz are calculated by AxoScan from the average refractive index and the film thickness d measured in step (1). Then, retardation values Rt (450), Rt (550), and Rt (650) in the thickness direction at the respective wavelengths of 450 nm, 550 nm, and 650 nm are calculated based on the above formula (II).

In the optical film of the present invention, Nz defined by the following formula (d1) preferably satisfies the following formula (d2).
(D1) Nz = Rt (550) / Ro (550) +0.5
(D2) 0 ≦ Nz ≦ 1
If Nz satisfies the formula (d2), the retardation value Rt in the thickness direction is relatively smaller than the retardation value R0 in the in-plane direction, so that the image display device including the optical film of the present invention is inclined. It is possible to reduce the change in color when observed from above.

  The angle θ (orientation angle) formed by the in-plane slow axis of the optical film of the present invention and the width direction of the film is preferably 40 ° or more and 50 ° or less. When the orientation angle is within the above range, the optical film is unwound from the roll body and has a slow axis in an oblique direction with respect to the long direction, and the transmission axis is unwound from the roll body and parallel to the long direction. A circularly polarizing plate can be easily manufactured by laminating the polarizers having a roll-to-roll so that the longitudinal directions thereof overlap each other. Thereby, there is little cut loss of a film and it is advantageous on production. The orientation angle θ is more preferably 45 ± 2 °, and particularly preferably 45 °.

  The orientation angle θ of the optical film can be measured with an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  The film thickness of the optical film is preferably 250 μm or less, more preferably 100 μm or less, and even more preferably 70 μm or less in order to reduce the variation in retardation due to heat or humidity. On the other hand, the film thickness of the optical film is preferably 10 μm or more, and more preferably 20 μm or more, in order to express a certain level of film strength or retardation. When the film thickness of the optical film is within these ranges, it is preferable from the viewpoint of thinning and productivity of the image display device.

  The haze (total haze) of the optical film is preferably less than 1%, more preferably 0.5% or less, and even more preferably 0.2% or less. If the haze is less than 1%, the transparency of the film does not decrease and the film functions sufficiently as an optical film.

  The haze (total haze) of the optical film can be measured with a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. The light source of the haze meter may be a 5V9W halogen sphere, and the light receiving portion may be a silicon photocell (with a relative visibility filter). The haze can be measured under conditions of 23 ° C. and 55% RH.

  The visible light transmittance of the optical film of the present invention is preferably 90% or more, and more preferably 93% or more. In the optical film of the present invention, the elongation at break in at least one direction measured in accordance with JIS-K7127-1999 is preferably 10% or more, more preferably 20% or more, and further preferably 30. % Or more.

  Since the optical film of the present invention contains the compound represented by the above general formula (1), the retardation value in the in-plane direction is high and has sufficient reverse wavelength dispersion. Therefore, the optical film of the present invention has a high retardation in a wide wavelength region. Moreover, since the shrinkage | contraction of the film at the time of high magnification extending | stretching is suppressed, the phase difference nonuniformity and the wavelength dispersion nonuniformity can also be reduced.

  The optical film of the present invention is used as an optical film of an image display device such as an organic EL display or a liquid crystal display device; specifically, a polarizing plate protective film, a retardation film, an optical compensation film, or an antireflection film, preferably Used as a λ / 4 retardation film.

  The λ / 4 retardation film has an in-plane retardation R0 of about ¼ of a predetermined wavelength of light (usually in the visible light region). The λ / 4 retardation film is preferably composed of a single layer of the optical film of the present invention. The λ / 4 retardation film is preferably used as an antireflection film for an organic EL display.

2. Method for Producing Optical Film The optical film of the present invention can be produced by a solution casting method or a melt casting method. The solution casting method is preferable from the viewpoint of suppressing optical defects such as coloring of the optical film, foreign matter defects, and die lines, and the melt casting method is preferable from the viewpoint of suppressing the solvent from remaining in the optical film.

A) Solution Casting Method A method for producing an optical film containing a cellulose ester by a solution casting method is as follows. A1) At least a cellulose ester and a compound represented by the above formula (1) are dissolved in a solvent to form a dope. A2) casting the dope on an endless metal support, A3) evaporating the solvent from the cast dope to obtain a web, A4) peeling the web from the metal support, and A5. ) After drying the web, it includes a step of drawing to obtain a film.

A1) Step of obtaining a dope In a dissolution vessel, a dope is prepared by dissolving a cellulose ester and, if necessary, other additives in a solvent.

  A solvent can be used without a restriction | limiting, if a cellulose ester, another additive, etc. are melt | dissolved. For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Preferably, methylene chloride, methyl acetate, ethyl acetate, acetone or the like can be used.

  The dope preferably further contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of the alcohol in the dope is high, the web is gelled and peeling from the metal support becomes easy. On the other hand, when the ratio of alcohol in the dope is small, dissolution of cellulose acetate in a non-chlorine organic solvent system can be promoted.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like. Of these, ethanol is preferred because of high dope stability, relatively low boiling point, and high drying properties.
Especially, it is preferable that dope contains the methylene chloride of a solvent, and a C1-C4 linear or branched aliphatic alcohol.

  The concentration of the cellulose ester in the dope is preferably high in order to reduce the drying load, but if the concentration of the cellulose ester is too high, it is difficult to filter. Therefore, the concentration of the cellulose ester in the dope is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 25% by mass.

  The method for dissolving the cellulose ester in a solvent may be, for example, a method for dissolving under heating and pressure. A higher heating temperature is preferable from the viewpoint of increasing the solubility of the cellulose ester. If the temperature is too high, the pressure needs to be increased, and the productivity is lowered. Therefore, the heating temperature is preferably within the range of 45 to 120 ° C.

  The additive may be added batchwise to the dope, or an additive solution may be separately prepared and added inline. In particular, it is preferable to add all or part of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester to facilitate mixing with the dope. The content of the preferred thermoplastic resin can be in the range of 1 to 10 parts by mass, more preferably in the range of 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  For in-line addition and mixing, for example, a static mixer (manufactured by Toray Engineering), an in-line mixer such as SWJ (Toray Static In-Pipe Mixer Hi-Mixer), or the like is preferably used.

  The obtained dope may contain insoluble matters such as impurities contained in the cellulose ester as a raw material, for example. Such an insoluble matter can become a bright spot foreign material in the obtained film. In order to remove insoluble matter, it is preferable to further filter the obtained dope.

The dope filtration is preferably performed so that the number of bright spot foreign substances in the obtained film is a certain value or less. Specifically, the number of bright spot foreign matters having a diameter of 0.01 mm or more is 200 / cm ² or less, preferably 100 / cm ² or less, more preferably 50 / cm ² or less, and still more preferably 30 Filtration is performed so that the number of particles / cm ² or less, particularly preferably 10 / cm ² or less.

The bright spot foreign matter having a diameter of 0.01 mm or less is also preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, It is more preferably 30 pieces / cm ² or less, particularly preferably 10 pieces / cm ² or less, and most preferably none.

The number of bright spot foreign matter on the film can be measured by the following procedure.
1) Two polarizing plates are arranged in a crossed Nicol state, and the obtained film is arranged between them.
2) When light is applied from the side of one polarizing plate and observed from the side of the other polarizing plate, the number where the light appears to leak is counted as a foreign object.

A2) Casting step The dope is cast on the endless metal support from the slit of the pressure die.

  As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The surface of the metal support is preferably mirror-finished.

  The width of the cast can be in the range of 1-4 m. The surface temperature of the metal support in the casting process is set to −50 ° C. or higher and below the temperature at which the solvent boils and does not foam. A higher temperature is preferable because the web can be dried at a higher speed, but it is within a temperature range in which foaming of the web and deterioration of flatness can be prevented.

  The surface temperature of the metal support is preferably in the range of 0 to 100 ° C, more preferably in the range of 5 to 30 ° C. Alternatively, the metal support may be cooled so that the web is gelled and can be peeled off from the drum in a state containing a large amount of residual solvent.

  The method for adjusting the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of bringing hot water into contact with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short.

  When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the intended temperature is used while preventing foam . In particular, it is preferable to efficiently dry by changing the temperature of the metal support and the temperature of the drying air during the period from casting to peeling.

A3) Solvent evaporation step The web (dope film obtained by casting the dope on the metal support) is heated on the metal support to evaporate the solvent. The drying method and drying conditions of the web can be the same as in the above-described A2) casting step.

A4) Peeling Step The web obtained by evaporating the solvent on the metal support is peeled off at the peeling position on the metal support. The residual solvent amount of the web at the time of peeling at the peeling position on the metal support is preferably within the range of 10 to 150% by mass in order to improve the flatness of the obtained film. % Or in the range of 60 to 130 mass%, more preferably in the range of 20 to 30 mass% or 70 to 120 mass%.

The amount of residual solvent in the web is defined by the following formula.
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount means a heat treatment at 115 ° C. for 1 hour.

A5) Drying and stretching step The web obtained by peeling from the metal support is dried as necessary and then stretched. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips.

  The method of drying the web may be a method of drying with hot air, infrared rays, a heating roller, microwaves, or the like, and a method of drying with hot air is preferable because it is simple.

  An optical film having a desired retardation is obtained by stretching the web. The retardation of the optical film can be controlled by adjusting the magnitude of tension on the web.

  In the optical film of the present invention, the web is stretched in an oblique direction (obliquely stretched) in order to make the angle formed by the slow axis in the plane of the optical film and the transport direction of the film within a range of 40 to 50 °. . The oblique direction is a direction having an angle in the range of 40 to 50 ° with respect to the web conveyance direction, and is preferably stretched in a direction at an angle of 45 ° with respect to the web conveyance direction.

  As described above, a polarizing film unwound from a roll body and having a transmission axis in the longitudinal direction, and an optical film unwound from the roll body and having a slow axis in a direction at an angle of 45 ° with respect to the longitudinal direction. Can be easily manufactured by simply laminating them in a roll-to-roll manner so that their longitudinal directions overlap each other. Moreover, the cut loss of the film can be reduced, which is advantageous in production.

  The draw ratio is represented by the ratio W / W0 of the width of the film before and after stretching (W is before stretching, W0 is the width after stretching), and the film thickness of the obtained optical film and the required retardation However, it is preferably in the range of 1.3 to 3.0 times, more preferably in the range of 1.5 to 2.8 times.

  The stretching temperature is preferably in the range of 120 to 230 ° C, more preferably in the range of 150 to 220 ° C, and even more preferably greater than 150 ° C and 210 ° C or less.

  It does not restrict | limit especially as a method of producing the film in which a slow axis inclines within the range of 40-50 degrees with respect to a conveyance direction. For example, there is a method in which the right and left in the width direction are gripped by the gripping means, and the web is stretched using a tenter that can independently control the gripping length of the web (distance from the start of gripping to the end of gripping).

  Examples of the stretching apparatus having a mechanism for stretching in an oblique direction include the stretching apparatus described in Example 1 of Japanese Patent Application Laid-Open No. 2003-340916, the stretching apparatus illustrated in FIG. The stretching apparatus described in 2007-30466, the stretching apparatus used in Example 1 of JP 2007-94007 A, and the like are included.

  Moreover, the method of using the linear diagonal stretch apparatus (simultaneous biaxial stretching apparatus) and not having to incline the direction which pays out a long film and the direction which winds up the long film after extending | stretching is also mentioned. Specifically, gripping both ends of the film with a plurality of gripping tools, and conveying the film, the difference in travel speed between the gripping tool gripping one end and the gripping tool gripping the other end. And a method of obliquely stretching the film. For example, the method described in JP2008-23775A can be mentioned.

  The residual solvent of the web at the start of stretching is preferably 20% by mass or less, more preferably 15% by mass or less.

  The stretched film is dried as necessary and then wound. As described above, the film may be dried while being transported by a large number of rollers arranged above and below (roller method), or the both ends of the web may be fixed with clips and dried while being transported. Also good (tenter method).

B) Melt Casting Method The method for producing the optical film of the present invention by the melt casting method is as follows: B1) Step of producing molten pellets (pelletizing step), B2) Step of extruding after melting and kneading the molten pellets (melting) Extruding step), B3) a step of cooling and solidifying the molten resin to obtain a web (cooling solidification step), and B4) a step of stretching the web (stretching step).

B1) Pelletization process It is preferable that the resin composition containing the cellulose ester which is the main component of the optical film is previously kneaded and pelletized. Pelletization can be performed by a known method. For example, a resin composition containing the aforementioned cellulose ester and, if necessary, an additive such as a plasticizer, is melt-kneaded with an extruder, and then from a die. Extrude into a strand. The molten resin extruded in a strand form can be cooled with water or air, and then cut to obtain pellets.

  The pellet raw material is preferably dried before being supplied to the extruder in order to prevent decomposition.

  The mixture of the antioxidant and the cellulose ester may be mixed with each other, or the cellulose ester may be mixed with an antioxidant dissolved in a solvent, or the antioxidant may be mixed with the cellulose ester. You may spray and mix. The atmosphere around the feeder part of the extruder and the outlet part of the die is preferably an atmosphere of dehumidified air or nitrogen gas in order to prevent deterioration of the raw material of the pellet.

  In an extruder, kneading is preferably performed at a low shearing force or at a low temperature so as not to cause deterioration of the resin (decrease in molecular weight, coloring, gel formation, etc.). For example, when kneading with a twin screw extruder, it is preferable to use a deep groove type screw and to rotate the two screws in the same direction. In order to knead uniformly, it is preferable that two screw shapes mesh with each other.

  Instead of pelletizing the resin composition containing cellulose ester, an optical film may be produced by melt-kneading a cellulose ester not melt-kneaded as a raw material with an extruder.

B2) Melt extrusion step The obtained molten pellets and other additives as required are supplied from the hopper to the extruder. The supply of pellets is preferably performed under vacuum, reduced pressure, or an inert gas atmosphere in order to prevent oxidative decomposition of the pellets. And it melt-kneads the melt pellet which is a film material, and another additive as needed with an extruder.

  The melting temperature of the film material in the extruder is preferably in the range of Tg to (Tg + 100) ° C., more preferably when the glass transition temperature of the film is Tg (° C.), although it depends on the type of film material. Is within the range of (Tg + 10) to (Tg + 90) ° C.

  Furthermore, when additives such as plasticizers and fine particles are added in the middle of the extruder, a mixing device such as a static mixer is further arranged on the downstream side of the extruder to uniformly mix these components. May be.

  The molten resin extruded from the extruder is filtered through a leaf disc filter or the like as necessary, and further mixed with a static mixer or the like, and extruded from a die into a film.

  The extrusion flow rate is preferably stabilized using a gear pump. Moreover, it is preferable that the leaf disk filter used for removal of a foreign material is a stainless fiber sintered filter. The stainless steel fiber sintered filter is an integrated, intricately intertwined stainless steel fiber body that is compressed and sintered by integrating the contact points. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is adjusted. it can.

  The melting temperature of the resin at the exit portion of the die can be in the range of about 200-300 ° C.

B3) Cooling and solidifying step The resin extruded from the die is nipped between the cooling roller and the elastic touch roller to make the film-like molten resin a predetermined thickness. Then, the film-like molten resin is cooled and solidified stepwise by a plurality of cooling rollers.

  The surface temperature of the cooling roller can be Tg (° C.) or lower when the glass transition temperature of the film is Tg (° C.). The surface temperatures of the plurality of cooling rollers may be different.

  The elastic touch roller is also called a pinching rotary body. A commercially available elastic touch roller can also be used. The film surface temperature on the elastic touch roller side can be in the range of Tg to (Tg + 110) ° C. of the film.

  The film-like molten resin solidified from the cooling roller is peeled off by a peeling roller or the like to obtain a web. When peeling the film-like molten resin, it is preferable to adjust the tension in order to prevent deformation of the obtained web.

B4) Stretching step As in the solution casting method, the obtained web is stretched in an oblique direction with a stretching machine to obtain a film. The web stretching method, stretching ratio, and stretching temperature may be the same as in the solution casting method.

  Thus, the optical film of the present invention is obtained through a step of stretching the original film in an oblique direction at a high magnification. The raw film containing the compound represented by the general formula (1) has appropriate flexibility and good stretchability. Thereby, the shrinkage | contraction of the film at the time of high magnification extending | stretching can be reduced, and the retardation of an optical film and the nonuniformity of wavelength dispersion can be decreased.

3. Circularly polarizing plate The circularly polarizing plate of this invention has a polarizer (linearly-polarizing film) and the optical film of this invention arrange | positioned on the at least one surface. The optical film of the present invention may be disposed directly on the polarizer or may be disposed via another layer or film.

  The polarizer may be an iodine polarizing film, a dye polarizing film using a dichroic dye, or a polyene polarizing film. The iodine-based polarizing film and the dye-based polarizing film may be generally a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing with iodine or a dichroic dye; After the film is dyed with iodine or a dichroic dye, it may be a uniaxially stretched film (preferably a film further subjected to a durability treatment with a boron compound). The absorption axis of the polarizer is parallel to the stretching direction of the film.

  The polyvinyl alcohol film may be a film formed from a polyvinyl alcohol aqueous solution. The polyvinyl alcohol film is preferably an ethylene-modified polyvinyl alcohol film because it is excellent in polarizing performance and durability performance, and has few color spots.

  Examples of dichroic dyes include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes and anthraquinone dyes.

  The thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm.

  In order to obtain the function as a circularly polarizing plate, the angle formed by the absorption axis (or transmission axis) of the polarizer and the in-plane slow axis of the optical film of the present invention is within the range of 40 to 50 °. It is preferable that it is 45 °, and more preferably 45 °.

  A reflective polarizing plate may be further disposed between the polarizer and the optical film of the present invention. The reflective polarizing plate transmits linearly polarized light in a direction parallel to the transmission axis of the polarizer and reflects linearly polarized light in a direction different from the transmission axis. The organic EL display device having such a circularly polarizing plate can emit more light emitted from the light emitting layer to the outside.

  Examples of the reflective polarizing plate include a birefringent optical polarizer (described in JP-A-8-503313) in which polymer thin films having different refractive indexes in one direction are alternately laminated, and a polarization separation film having a cholesteric structure (special Described in Kaihei 11-44816). Moreover, you may arrange | position a protective film further on the surface of a polarizer.

  When the optical film of the present invention is disposed on one surface of the polarizer, a transparent protective film other than the optical film of the present invention may be disposed on the other surface of the polarizer. The transparent protective film is not particularly limited, and may be a normal cellulose ester film or the like. Examples of the cellulose ester film include commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-X8 -C, KC8UXW-RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Advanced Layer Co., Ltd.) and the like are preferably used.

  The thickness of the transparent protective film is not particularly limited, but can be in the range of about 10 to 200 μm, preferably in the range of 10 to 100 μm, and more preferably in the range of 10 to 70 μm.

  When the optical film or the transparent protective film of the present invention is disposed on the outermost surface of the display, a transparent hard coat layer, an antiglare layer, an antireflection layer, or the like may be further provided on the outermost surface of these films. .

  The circularly polarizing plate can be manufactured through a step of laminating the polarizer and the optical film of the present invention. As the adhesive used for bonding, for example, a completely saponified polyvinyl alcohol aqueous solution or the like is preferably used.

  The circularly polarizing plate can be preferably used for an image display device such as an organic EL display device or a liquid crystal display device described later.

4). Image display device The image display device of the present invention has the optical film of the present invention. The image display device of the present invention can be an organic EL display device or a liquid crystal display device.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of an organic EL display device. As shown in FIG. 1, the organic EL display device 10 includes a light reflecting electrode 12, a light emitting layer 14, a transparent electrode layer 16, a transparent substrate 18, and a circularly polarizing plate 20 in this order.

  The light reflecting electrode 12 is preferably made of a metal material having a high light reflectance. Examples of the metal material include Mg, MgAg, MgIn, Al, LiAl, and the like. The flatter surface of the light reflecting electrode 12 is preferable because irregular reflection of light can be prevented.

  The light reflecting electrode 12 can be formed by a sputtering method. The light reflecting electrode 12 may be patterned. Patterning can be performed by etching.

  The light emitting layer 14 includes R (red), G (green), and B (blue) light emitting layers. Each light emitting layer contains a light emitting material. The light emitting material may be an inorganic compound or an organic compound, and is preferably an organic compound.

  Each of the R, G, and B light-emitting layers further includes a charge transport material, and may further have a function as a charge transport layer. Each of the R, G, and B light emitting layers further includes a hole transport material, and may further have a function as a hole transport layer. When each of the R, G, and B light emitting layers does not include a charge transport material or a hole transport material, the organic EL display device 10 may further include a charge transport layer or a hole transport layer.

  The light emitting layer 14 can be formed by evaporating a light emitting material. Each of the R, G, and B light emitting layers is obtained by patterning. Patterning can be performed using a photomask or the like.

  The transparent electrode layer 16 can generally be an ITO (indium tin oxide) electrode. The transparent electrode layer 16 can be formed by a sputtering method or the like. The transparent electrode layer 16 may be patterned. Patterning can be performed by etching.

  The transparent substrate 18 may be any material that can transmit light, and may be a glass substrate, a plastic film, or the like.

  The circularly polarizing plate 20 is disposed such that the λ / 4 retardation film 20A is located on the transparent substrate 18 side and the polarizer 20B is located on the viewing side.

  When the organic EL display device 10 is energized between the light reflecting electrode 12 and the transparent electrode layer 16, the light emitting layer 14 emits light and can display an image. In addition, since each of the R, G, and B light-emitting layers is configured to be energized, a full-color image can be displayed.

  The circularly polarizing plate 20 includes a λ / 4 retardation film 20A and a polarizer 20B. The λ / 4 retardation film 20A can be used as the optical film of the present invention. The polarizer 20B is a linearly polarizing film.

  The optical film of the present invention or the circularly polarizing plate including the optical film is not limited to the organic EL display device having the above-described configuration, but also includes international patent applications WO96 / 34514, JP-A-9-127858, and 11-45058. The present invention can also be applied to the organic EL display device described in the publication. In that case, the optical film or the circularly polarizing plate of the present invention may be disposed in place of or together with the antireflection means of the organic EL display device provided in advance. The optical film or circularly polarizing plate of the present invention can also be applied to an inorganic EL display device described in, for example, “Electroluminescence Display” (Toshio Higuchi, Sangyo Tosho Co., Ltd., published in 1991).

  FIG. 2 is a schematic diagram for explaining the antireflection function of the circularly polarizing plate 20. As shown in FIG. 2, when light including linearly polarized light a1 and b1 enters from the outside in parallel to the normal line of the display screen of the organic EL display device 10, linearly polarized light b1 parallel to the transmission axis direction of the polarizer 20B. Only passes through the polarizer 20B. The other linearly polarized light a1 that is not parallel to the transmission axis of the polarizer 20B is absorbed by the polarizer 20B. The linearly polarized light b2 that has passed through the polarizer 20B is converted to circularly polarized light c2 by passing through the λ / 4 retardation film 20A. When the circularly polarized light c2 is reflected by the light reflecting electrode 12 (see FIG. 1) of the organic EL display device 10, the circularly polarized light c2 becomes reverse circularly polarized light c3. The reversely polarized circularly polarized light c3 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. This linearly polarized light b3 is absorbed by the polarizer 20B and cannot pass through.

  Thus, since all the light (including linearly polarized light a1 and b1) incident on the organic EL display device 10 from the outside is absorbed by the polarizer 20B, it is reflected by the light reflecting electrode 12 of the organic EL display device 10. However, it does not exit to the outside. Therefore, it is possible to prevent a decrease in image display characteristics due to the reflection of the background.

  As described above, the λ / 4 retardation film 20A made of the optical film of the present invention includes the compound represented by the formula (1). Therefore, the λ / 4 retardation film 20A exhibits sufficient reverse wavelength dispersion, and the unevenness of wavelength dispersion is reduced. Thereby, it can have a phase difference of λ / 4 with respect to light in a wide wavelength region. Therefore, most of the light incident from the outside can be prevented from leaking outside the organic EL display device 10. Therefore, the light leakage in the front direction when the organic EL display device 10 is displayed in black can be suppressed, and reflection can be prevented.

  Furthermore, since the λ / 4 retardation film 20A made of the optical film of the present invention has a high retardation, the thickness of the film can be reduced. As a result, it is possible to reduce the difference between the color in the front direction and the color in the oblique direction in the display device, and to improve the visibility from the oblique direction.

  Moreover, the light from the inside of the organic EL display device 10, that is, the light from the light emitting layer 14, includes two circularly polarized components of circularly polarized light c3 and c4. One circularly polarized light c3 is converted to linearly polarized light b3 by passing through the λ / 4 retardation film 20A as described above, and is absorbed without passing through the polarizer 20B. The other circularly polarized light c4 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. The linearly polarized light b4 passes through the polarizer 20B and becomes linearly polarized light b4, which is recognized as an image.

  A reflective polarizing plate (not shown) may be further disposed between the polarizer 20B and the λ / 4 retardation film 20A to reflect the linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. The reflective polarizing plate can reflect the linearly polarized light b3 without being absorbed by the polarizer 20B, reflect it again by the light reflecting electrode 12, and convert it into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. . By further disposing the reflective polarizing plate, all of the light emitted by the light emitting layer 14 (circularly polarized light c3 and c4) can be emitted to the outside.

  FIG. 3 is a schematic diagram illustrating an example of the configuration of the liquid crystal display device. As shown in FIG. 3, the liquid crystal display device 30 includes a liquid crystal cell 40, two polarizing plates 50 and 60 that sandwich the liquid crystal cell 40, and a backlight 70.

  The display method of the liquid crystal cell 40 is not particularly limited, and is a TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, IPS (In-Plane Switching) method, OCB (Optically Compensated Birefringence) method, VA (Vertical Alignment). There are methods (including MVA: Multi-domain Vertical Alignment, PVA: Patterned Vertical Alignment), and HAN (Hybrid Aligned Nematic). In order to increase the contrast, the VA (MVA, PVA) method is preferable.

  A VA liquid crystal cell includes a pair of transparent substrates and a liquid crystal layer sandwiched between them.

  Of the pair of transparent substrates, one transparent substrate is provided with a pixel electrode for applying a voltage to the liquid crystal molecules. The counter electrode may be disposed on one transparent substrate (transparent substrate on which the pixel electrode is disposed) or may be disposed on the other transparent substrate.

  The liquid crystal layer includes liquid crystal molecules having negative or positive dielectric anisotropy. When the liquid crystal molecules are not applied with voltage due to the alignment regulating force of the alignment film provided on the liquid crystal layer side surface of the transparent substrate and no electric field is generated between the pixel electrode and the counter electrode, the liquid crystal molecules The major axis is oriented so as to be substantially perpendicular to the surface of the transparent substrate.

  In the liquid crystal cell configured as described above, an electric field is generated between the pixel electrode and the counter electrode by applying a voltage corresponding to the image signal to the pixel electrode. Thereby, the liquid crystal molecules initially aligned perpendicularly to the surface of the transparent substrate are aligned so that the major axis thereof is in the horizontal direction with respect to the substrate surface. In this way, the liquid crystal layer is driven, and the image display is performed by changing the transmittance and reflectance of each sub-pixel.

  The polarizing plate 50 is disposed on the viewing side of the liquid crystal cell 40, and includes a polarizer 52, a protective film 54 disposed on the viewing side of the polarizer 52, and a protective film disposed on the liquid crystal cell side of the polarizer 52. 56. The polarizing plate 60 is disposed on the backlight 70 side of the liquid crystal cell 40, is disposed on the backlight side of the polarizer 62, the protective film 64 disposed on the surface of the polarizer 62 on the liquid crystal cell side, and the polarizer 62. And a protective film 66. One of the protective films 56 and 64 may be omitted as necessary.

  Any of the protective films 54, 56, 64 and 66; preferably the protective film 66 can be the optical film of the present invention.

  In the following, the invention will be described in more detail with reference to examples. These examples do not limit the scope of the present invention.

1. Optical Film Material 1) Cellulose Ester The cellulose ester shown in the table below was prepared.

2) Additive Compound represented by general formula (1) Exemplary compounds A1, A2, A3, A7, A13, A14, A16, A23, A24, A27, A28, A29, A37

(Synthesis Example 1)
Synthesis of exemplary compound A1

(Synthesis of Intermediate A)
In a reaction vessel equipped with an ester tube, 125 ml of toluene, 12.5 g (0.12 mol) of malonic acid, 31.7 g (0.26 mol) of diethylene glycol monomethyl ether and 11.42 g of p-toluenesulfonic acid monohydrate are charged. The mixture was stirred for 5 hours while heating under reflux in a nitrogen atmosphere. Distillation of water was confirmed as the reaction progressed. Then, the solvent was depressurizingly distilled from the reaction liquid, and it refine | purified by the silica gel chromatography, and 27.7g of intermediate bodies A were obtained.

(Synthesis of Intermediate B)
To 200 ml of N, N-dimethylformamide, 6.9 g (0.05 mol) of 2,5-dihydroxybenzaldehyde, 31.6 g (0.11 mol) of bromomethyl-trans-4- (trans-4′-ethylcyclohexyl) cyclohexane, carbonic acid Potassium 13.8g and potassium iodide 3.3g were added, and it stirred at 100 degreeC under nitrogen atmosphere for 5 hours. After cooling the reaction solution, extraction was performed by adding water and ethyl acetate. The solvent was distilled off from the organic layer under reduced pressure, and the resulting crude crystals were purified by silica gel chromatography to obtain 13.2 g of Intermediate B.

(Synthesis of Exemplary Compound A1)
A reaction vessel equipped with an ester tube was charged with 50 ml of toluene, 5.5 g (0.01 mol) of intermediate B, 3.1 g (0.01 mol) of intermediate A and 1.5 g of piperidine, and heated in a nitrogen atmosphere. The mixture was stirred for 5 hours while refluxing. Distillation of water was confirmed as the reaction progressed. After cooling the reaction solution, extraction was performed by adding water and ethyl acetate. The solvent was distilled off from the organic layer under reduced pressure, and the resulting crude crystals were purified by silica gel chromatography to obtain 6.1 g of Exemplified Compound A1.

(Synthesis Example 2)
Synthesis of exemplary compound A14

(Synthesis of Intermediate C)
A reaction vessel equipped with an ester tube was charged with 3.0 g (15.1 mmol) of 2,5-dihydroxyterephthalic acid, 60 ml of dipropylene glycol monomethyl ether, and 6.4 g (45.1 mmol) of boron trifluoride diethyl ether, The mixture was stirred at 130 ° C. for 5 hours under a nitrogen atmosphere. Then, after distilling off excess dipropylene glycol monomethyl ether from the reaction solution, 100 ml of ethyl acetate was added, and the extract was washed with water. The organic layer was concentrated and purified by silica gel column chromatography to obtain 5.6 g of Intermediate C.

(Synthesis of Exemplary Compound A14)
45 ml of tetrahydrofuran and 4.0 g (50.0 mmol) of pyridine were added to 4.6 g (10.0 mmol) of the intermediate C, followed by cooling with ice water. A solution in which 5.6 g (22.0 mmol) of trans-4- (trans-4′-ethylcyclohexyl) cyclohexanecarboxylic acid chloride was dissolved in 10 ml of tetrahydrofuran was dropped, and the mixture was stirred at 25 ° C. for 2 hours after completion of the dropwise addition. 30 ml of water was added, and the precipitate was collected by filtration and washed with methanol to obtain 5.4 g of Exemplary Compound A14.

(Synthesis Example 3)
Synthesis of exemplary compound A23

(Synthesis of Intermediate D)
70 ml of acetone and 12.0 g (0.15 mol) of pyridine were added to 13.8 g (0.10 mol) of p-hydroxybenzoic acid, followed by cooling with ice water. A solution obtained by dissolving 23.2 g (0.11 mol) of 4-pentylbenzoyl chloride in 20 ml of acetone was added dropwise thereto. After completion of dropping, the mixture was stirred at room temperature for 3 hours. The reaction solution was concentrated under reduced pressure, and 300 ml of ethyl acetate was added. The obtained organic layer was washed with 1N hydrochloric acid and then with water until neutrality. The organic layer was concentrated under reduced pressure, and toluene was added and stirred. And after filtering a deposit, it was made to dry and 18.5g of intermediate bodies D were obtained.

(Synthesis of Intermediate E)
After adding 150 ml of toluene to 15.6 g (0.05 mol) of Intermediate D, 17.8 g (0.15 mol) of thionyl chloride and 1 ml of dimethylformamide were sequentially added, followed by stirring at 110 ° C. for 4 hours. The reaction solution was concentrated under reduced pressure to obtain 16.3 g of Intermediate E.

(Synthesis of Exemplary Compound A23)
45 ml of tetrahydrofuran and 4.0 g (50.0 mmol) of pyridine were added to 4.6 g (10.0 mmol) of the intermediate C, followed by cooling with ice water. A solution prepared by dissolving 7.2 g (22.0 mmol) of the intermediate E in 10 ml of tetrahydrofuran was added dropwise thereto. After completion of dropping, the mixture was stirred at 25 ° C. for 2 hours. 30 ml of water was added thereto, and the precipitate was collected by filtration and washed with methanol to obtain 8.4 g of Exemplified Compound A23.

(Synthesis Example 4)
Synthesis of exemplary compound A32

(Synthesis of Intermediate F)
After adding 20 ml of toluene to 5.0 g (23.8 mmol) of trimesic acid, 15.5 ml (214.2 mmol) of thionyl chloride and 0.5 ml of dimethylformamide were added, and the mixture was stirred at 120 ° C. for 2 hours. The reaction solution was concentrated under reduced pressure to obtain 6.3 g of Intermediate F.

(Synthesis of Exemplary Compound A32)
6.3 g (23.7 mmol) of intermediate F was dissolved in 100 ml of dimethylacetamide, 16.8 g (213.3 mmol) of pyridine was added, and the mixture was cooled to −5 ° C. A solution prepared by dissolving 0.94 g of 2- (2-methoxyethoxy) ethanamine in 20 ml of dimethylacetamide was slowly added dropwise thereto, followed by stirring at −5 ° C. for 1 hour. A solution prepared by dissolving 5.2 g (47.4 mmol) of p-aminophenol in 20 ml of dimethylacetamide was further added dropwise thereto, and the mixture was stirred at 10 ° C. for 1 hour. To this was added 9.4 g (47.4 mmol) of p-acetoxybenzoic acid chloride dissolved in 20 ml of dimethylacetamide, and the mixture was stirred at 25 ° C. for 2 hours. Water was added to the resulting reaction solution, and the precipitate was collected by filtration and purified by silica gel column chromatography to obtain 2.7 g of exemplary compound A32.

(Synthesis Example 5)
Synthesis of exemplary compound A29

(Synthesis of Intermediate G)
50 ml of tetrahydrofuran was added to 5.5 g (40.0 mmol) of p-hydroxybenzoic acid, and ice water cooling was performed. To this, 4.2 g (20.0 mmol) of trans-1,4-cyclohexanedicarboxylic acid chloride dissolved in 10 ml of tetrahydrofuran was dropped, and the mixture was stirred at 25 ° C. for 3 hours. 100 ml of ethyl acetate was added to the resulting reaction solution, washed with 1N hydrochloric acid, and the organic layer was washed with water until neutrality. After the organic layer was concentrated under reduced pressure, the residue was suspended in methanol to obtain 5.8 g of Intermediate G.

(Synthesis of Exemplary Compound A29)
50 g of toluene was added to 4.1 g (10.0 mmol) of Intermediate G, 5.9 g (50.0 mmol) of thionyl chloride and 0.5 ml of dimethylformamide were added, and the mixture was stirred at 110 ° C. for 3 hours. The obtained reaction solution was concentrated under reduced pressure, 50 ml of tetrahydrofuran and 2.4 g (30.0 mmol) of pyridine were added, and the mixture was cooled with ice water. A solution prepared by dissolving 3.3 g (20.0 mmol) of dipropylene glycol in 10 ml of tetrahydrofuran was added dropwise thereto, and after completion of the addition, the mixture was stirred at 25 ° C. for 4 hours. The obtained reaction solution was concentrated under reduced pressure, 100 ml of ethyl acetate was added, and the mixture was washed with 1N hydrochloric acid, and then washed with water until the organic layer became neutral. The organic layer was concentrated under reduced pressure and then purified by silica gel column chromatography to obtain 4.0 g of exemplary compound A29.

  Other exemplary compounds were synthesized in the same manner as in any of the synthesis examples described above, except that the types of raw materials were changed.

Comparative compounds The following comparative compounds-1 to 3 were used.

[Measurement of solution absorption spectrum]
The prepared exemplary compounds and comparative compounds of the present invention were dissolved in tetrahydrofuran (without stabilizer) to obtain a solution having a concentration of 10 ⁻⁵ mol / L. The obtained solution was put into a quartz cell (10 mm long square cell), and the absorbance of the solution was measured using an absorption spectrophotometer (U-570, manufactured by JASCO Corporation). The maximum absorption wavelength in the wavelength region of 200 to 370 nm in the obtained solution absorption spectrum was defined as λmax. When there are a plurality of maximum absorptions in the above wavelength range, the maximum absorption on the longest wavelength side is defined as λmax.

2. Production of optical film (Example 1)
Preparation of Fine Particle Dispersion 1 The following components were stirred and mixed with a dissolver for 50 minutes and then dispersed with Manton Gorin to obtain fine particle dispersion 1.
(Composition of fine particle dispersion 1)
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.): 11 parts by mass Ethanol: 89 parts by mass

Preparation of Fine Particle Additive Solution 1 The obtained fine particle dispersion 1 was slowly added to a dissolution tank charged with methylene chloride with sufficient stirring. The obtained solution was dispersed with an attritor so that the particle size of the secondary particles of the fine particles became a predetermined size, and then filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. 1 was obtained.
(Composition of fine particle additive liquid 1)
Methylene chloride: 99 parts by mass Fine particle dispersion 1: 5 parts by mass

Preparation of Dope Solution Methylene chloride and ethanol were charged into a pressure dissolution tank, and cellulose ester C, sugar ester compound, exemplary compound A1 and fine particle additive solution 1 were charged with stirring. The resulting solution was heated and completely dissolved with stirring. The obtained solution was used as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. Filtration using 244 gave a dope solution.
(Dope solution composition)
Methylene chloride: 520 parts by weight Ethanol; 45 parts by weight Cellulose ester C: 100 parts by weight The following sugar ester compound A: 5 parts by weight Illustrative compound A1: 3 parts by weight Fine particle additive solution 1: 1 part by weight

  The obtained dope solution was uniformly cast on a stainless steel belt support using an endless belt casting apparatus. After the solvent in the cast film cast on the stainless steel belt support was evaporated until the residual solvent amount became 75%, the obtained web was peeled from the stainless steel belt support. The obtained web was conveyed while being gripped by a clip of a tenter stretching apparatus. The obtained web was dried in a drying zone while being conveyed by a number of rolls. Then, after slit-removing the width direction edge part of the web currently hold | gripped with the tenter clip with a laser cutter, it wound up and obtained the original fabric film.

  The obtained raw film is unwound and stretched in an oblique direction (45 ° with respect to the width direction of the film) at a glass transition temperature + 20 ° C. of the original film at a draw ratio of 2.5 times. Film 101 was obtained. The film thickness of the obtained optical film 101 was 30 μm. The angle θ formed by the in-plane slow axis of the obtained optical film 101 and the width direction of the film was 45 °.

(Examples 2-22, Comparative Examples 1-9)
In the production of the optical film 101, the optical films 102 to 131 were prepared in the same manner as in Example 1 except that the cellulose ester C, the type and addition amount of the exemplified compound A1, and the film thickness of the film were changed as shown in Table 2. Obtained. The film thickness of the optical film was adjusted by the flow rate of the dope solution. Further, the angles θ formed between the in-plane slow axis of the optical film and the width direction of the film were all 45 °.

  R0, wavelength dispersion characteristics (R0 (450) / R0 (550)) and unevenness of the obtained optical film were evaluated by the following methods.

[R0, Rth and wavelength dispersion characteristics]
1) The optical film was conditioned at 23 ° C. and 55% RH. The average refractive index of the optical film after humidity control at 450 nm, 550 nm and 650 nm was measured using an Abbe refractometer and a spectral light source, respectively. Moreover, the thickness of the optical film was measured using the film thickness meter.
2) In-plane phase difference R0 (450), R0 (550) when light having a measurement wavelength of 450 nm, 550 nm, or 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface R0 (650) was measured with an AxoScan manufactured by Axometric.
3) Using AxoScan manufactured by Axometric, the wavelength measured from the angle of φ (incident angle (φ)) with respect to the normal to the surface of the optical film, with the slow axis in the plane of the optical film as the tilt axis (rotation axis) The phase difference R (φ) when light of 450 nm, 550 nm, or 650 nm was incident was measured, respectively. The phase difference R (φ) was measured at 6 points every 10 ° in the range of φ from 0 ° to 50 °. The in-plane slow axis of the optical film was confirmed by AxoScan manufactured by Axometric.
4) From R0 and R (φ) measured at each wavelength (λ) and the above-mentioned average refractive index and film thickness, nx, ny and nz are calculated by AxoScan made by Axometric, and the following formula Based on (I) and (II), the thickness direction retardation Rth (450), Rth (550) or Rth (650) at the measurement wavelength of 450 nm, 550 nm or 650 nm was calculated, respectively. The phase difference was measured under conditions of 23 ° C. and 55% RH.
Formula (I): R0 (λ) = (nx (λ) −ny (λ)) × d (nm)
Formula (II): Rth (λ) = {(nx (λ) + ny (λ)) / 2−nz (λ)} × d (nm)
(In formulas (I) and (II),
nx (λ) represents a refractive index in the slow axis direction x at which the refractive index is maximum in the in-plane direction of the optical film when light having a wavelength λ is incident;
ny (λ) represents a refractive index in a direction y perpendicular to the slow axis direction x in the in-plane direction of the optical film when light having a wavelength λ is incident;
nz (λ) represents the refractive index in the thickness direction z of the optical film when light having a wavelength λ is incident;
d (nm) represents the thickness of the optical film)
Furthermore, R0 (450) / R0 (550) was calculated from the obtained R0 (450) and R0 (550).

[Unevenness of R0]
Measurement of R0 (550) of the obtained optical film was performed at 50 points in the width direction of the film at 10 points. The difference between the maximum value and the minimum value of all measured values obtained was evaluated as “R0 unevenness” according to the following criteria.
A: Unevenness of R0 is less than 1 nm B: Unevenness of R0 is not less than 1 nm and less than 2 nm C: Unevenness of R0 is not less than 2 nm and less than 4 nm D: Unevenness of R0 is not less than 4 nm and less than 6 nm E: Unevenness of R0 is 6 nm or more If it is above the level, there is no practical problem, but the B level is preferred, and the A level is particularly preferred.

[Unevenness of R0 (450) / R0 (550)]
R0 (550) and R0 (450) of the obtained optical film were measured at 10 points at intervals of 50 mm in the width direction of the film. The difference between the maximum value and the minimum value of all the measured values of R0 (450) / R0 (550) thus obtained was evaluated as “R0 (450) / R0 (550) unevenness” according to the following criteria.
A: Unevenness of R0 (450) / R0 (550) is less than 0.01 B: Unevenness of R0 (450) / R0 (550) is not less than 0.01 and less than 0.02 C: R0 (450) / R0 (550 ) Non-uniformity of 0.02 or more and less than 0.03 D: R0 (450) / R0 (550) non-uniformity of 0.03 or more Here, if it is B level or more, there is no practical problem, but it is A level. Is preferred.

The evaluation results of the optical films of Examples 1 to 19 are shown in Table 2; the evaluation results of the optical films of Examples 20 to 22 and Comparative Examples 1 to 9 are shown in Table 3.

  As shown in Tables 2 and 3, the optical films of Examples 1 to 20 have high retardation and reverse wavelength dispersion, and both the retardation unevenness and the wavelength dispersion unevenness are small. Recognize. On the other hand, it can be seen that the optical films of Comparative Examples 1 to 9 have low retardation or positive wavelength dispersion, and large retardation dispersion and wavelength dispersion dispersion.

3. Preparation of circularly polarizing plate and display device (Example 23)
Production of Polarizer A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched under conditions of a stretching temperature of 110 ° C. and a stretching ratio of 5 times. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was washed with water and dried to obtain a polarizer having a thickness of 20 μm.

Production of Circular Polarizing Plate 201 The surface of the optical film 101 produced above was bonded to a polarizer and subjected to alkali saponification treatment. Similarly, a Konica Minolta tack film KC6UA (manufactured by Konica Minolta Opto Co., Ltd.) was prepared, and the bonding surface with the polarizer was subjected to alkali saponification treatment. Then, the optical film 101 is bonded to one surface of the polarizer via a 5% aqueous solution of polyvinyl alcohol as an adhesive; the other surface of the polarizer is Konica Minolta Tack Film KC6UA (Konica Minolta Opto Co., Ltd.). The circularly polarizing plate 201 was prepared by pasting together a 5% polyvinyl alcohol aqueous solution. The optical film 101 and the polarizer were bonded so that the angle formed by the transmission axis of the polarizer and the slow axis of the optical film 101 was 45 °.

Production of Display Device 301 A light-reflecting electrode made of chromium having a thickness of 80 nm was formed on a glass substrate by a sputtering method. An ITO thin film having a thickness of 40 nm was formed as an anode on the light reflecting electrode. Next, a hole transport layer made of poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) having a thickness of 80 nm was formed on the anode by sputtering. On the hole transport layer, RGB light emitting layers (red light emitting layer, green light emitting layer, and blue light emitting layer) were respectively formed by patterning using a shadow mask. The thickness of the light emitting layer was 100 nm for each color. The red light-emitting layer contains tris (8-hydroxyquinolinate) aluminum (Alq3) as a host and a light-emitting compound [4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H-pyran] (DCM). Was formed by co-evaporation (mass ratio 99: 1). The green light emitting layer is formed by co-evaporation (mass ratio 99: 1) of Alq3 and the luminescent compound coumarin 6 as a host; the blue light emitting layer is co-evaporated (mass of Balq and the luminescent compound Perylene as a host). Ratio 90:10).

  On the obtained RGB light emitting layer, a thin film having a thickness of 4 nm made of calcium having a low work function was formed as a first cathode capable of efficiently injecting electrons by vacuum deposition. On this 1st cathode, the thin film which consists of aluminum with a thickness of 2 nm was formed as a 2nd cathode, and the organic light emitting layer was obtained. The aluminum used as the second cathode has a role of preventing the first cathode calcium from being chemically altered when a transparent electrode is formed thereon by sputtering.

  Next, a transparent conductive film made of ITO and having a thickness of 80 nm (the first cathode, the second cathode, and the transparent conductive film were combined to form a transparent electrode layer) was formed on the second cathode by sputtering. Furthermore, a thin film having a thickness of 200 nm made of silicon nitride was formed on the transparent conductive film by a CVD method to obtain an insulating film (transparent substrate).

  On the obtained insulating film (transparent substrate), the circularly polarizing plate 201 was bonded via an adhesive to obtain an organic electroluminescence display device 301. The circularly polarizing plate 201 was bonded so that the optical film 101 was on the insulating film side.

(Examples 24-44, Comparative Examples 10-18)
Circular polarizers 202 to 231 and display devices 302 to 331 were obtained in the same manner as in Example 23 except that the optical film 101 was changed to the optical films 102 to 131. The display device was evaluated in the same manner as in Example 23.

  Color unevenness and contrast unevenness of the obtained organic EL display device were evaluated by the following methods.

[Color unevenness]
Color unevenness when the obtained organic EL display device was displayed in black was evaluated according to the following criteria.
A: There is no difference in the color of each part on the screen of the organic EL display device.
B: Although there is a difference in color for each part of the screen of the organic EL display device, there is no problem in use.
C: On the screen of the organic EL display device, there is a difference in color for each part, and it cannot be used as a product.
D: On the screen of the organic EL display device, there is a large difference in color for each part, so that it cannot be used as a product.

[Contrast unevenness]
In the environment of the obtained organic EL display device at 23 ° C. and 55% RH, the luminance during white display and the luminance during black display were measured. The measurement of luminance was performed by EZ-Contrast 160D manufactured by ELDIM. The measured value was applied to the following formula to obtain the front contrast.
Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)

The front contrast of any 10 points of the organic EL display device was measured. And the average value of the 10 front contrasts obtained was calculated | required. Furthermore, among the obtained 10 front contrasts, the maximum value or the minimum value of the front contrast that maximizes the absolute value of the difference from the average value was obtained. These values were applied to the following formula to determine the front contrast variation (%).
Variation in front contrast (%) = | (maximum or minimum value of front contrast) − (average value of front contrast) | / (average value of front contrast) × 100
And the dispersion | variation in front contrast was evaluated based on the following references | standards.
A: There is no variation in front contrast, and there is no unevenness. B: The variation in front contrast is less than 1 to 5%, and the variation is small. C: The front contrast is less than 5 to 10%, and the variation is slightly. Yes D: Front contrast is a variation of 10% or more, and unevenness is large

Table 4 shows the evaluation results of the organic EL display devices of Examples 23 to 44 and Comparative Examples 10 to 18.

  As shown in Table 4, it can be seen that the display devices of Examples 23 to 44 including the optical film of the present invention have less color unevenness and contrast unevenness than the display devices of Comparative Examples 10 to 16.

  According to the present invention, it is possible to provide an optical film that has a high retardation and good reverse wavelength dispersion, and that has reduced retardation and wavelength dispersion.

DESCRIPTION OF SYMBOLS 10 Organic electroluminescent display device 12 Light reflection electrode 14 Light emitting layer 16 Transparent electrode layer 18 Transparent substrate 20 Circularly-polarizing plate 20A (lambda) / 4 phase difference film 20B Polarizer 30 Liquid crystal display device 40 Liquid crystal cell 50, 60 Polarizing plate 70 Backlight 52, 62 Polarizer 54, 56, 64, 66 Protective film

Claims (9)

Cellulose ester and at least one compound represented by the following general formula ( 3 ),
When the in-plane retardation values measured at wavelengths of 450 nm, 550 nm, and 650 nm are R0 (450), R0 (550), and R0 (650), respectively, the expressions (a) to (c) are satisfied. Optical film.
(A) 110 nm ≦ R0 (550) ≦ 170 nm
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.03
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.03

(In general formula ( 3 ) ,
A represents a linking group selected from the group consisting of a single bond, —O—, —S—, —CO—, —CS—, —NR ₁ —, an alkylene group, an alkenylene group, or a combination thereof (R ₁ represents hydrogen Represents an atom or an alkyl group;
B represents a linking group represented by the following formula;

(In General Formula (2), R represents an alkylene group, and l represents an integer of 2 to 10)
R ₂₁ represents a hydrogen atom, an alkyl group, or an acyl group having no aromatic ring;
m represents 1 or 2; when m is 2, the plurality of B and R ₂₁ may be the same or different from each other;
n represents 1 or 2; when n is 2, the plurality of A, B and R ₂₁ may be the same or different from each other;
L ₂₁ and _{L 22} are each independently -O -, - S -, - CO -, - CS -, - NR 2 - or represents a linking group selected from the group consisting of _{(R 2} is Each independently represents a hydrogen atom or an alkyl group);
R ₂₂ and R ₂₄ each independently represents an aryl group, a cycloalkyl group or a heterocyclic group, which may have a substituent;
R ₂₃ represents a substituent;
r represents an integer of 0 to 3 and n + r ≦ 4; when r is 2 or 3, a plurality of R ₂₃ may be the same or different from each other) The optical film according to claim 1, wherein the compound represented by the general formula ( 3) has only one aromatic hydrocarbon ring . The optical film according to claim 1 or 2 , wherein the compound represented by the general formula ( 3) has at least one maximum absorption wavelength in a range of 250 nm to 400 nm in a solution absorption spectrum. Content of the compound represented by the said general formula ( 3 ) is 1-15 mass% with respect to the sum total of the thermoplastic resin containing the said cellulose ester, As described in any one of Claims 1-3 . Optical film. The optical film as described in any one of Claims 1-4 whose angle which the slow axis in the surface of the said optical film makes and the width direction of the said optical film is 40 degrees or more and 50 degrees or less. The optical film as described in any one of Claims 1-5 whose total substitution degree of the acyl group of the said cellulose ester is 2.0 or more and 2.6 or less. Thickness of 10 to 70 [mu] m, the optical film according to any one of claims 1-6. To any one of claims 1-7 comprising the optical film according, circularly polarizing plate. An image display device comprising the circularly polarizing plate according to claim 8 .

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