JP5983418B2 - Optical film, circularly polarizing plate, and image display device - Google Patents

Description

  The present invention relates to an optical film, a circularly polarizing plate, and an image 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 (hereinafter also referred to as an organic EL display) has attracted attention as a new image display device. In an 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. Therefore, external light incident on the display is reflected by the reflector to reduce the image contrast. There is a problem of lowering. For this reason, it is known that a circularly polarizing plate formed by laminating a λ / 4 retardation film and a polarizer is used on the surface side of the display in order to improve contrast of light and darkness by preventing reflection of external light. Moreover, such a circularly polarizing plate may be used also in what is called a 3D liquid crystal display device which displays a three-dimensional image.

  When manufacturing a circularly polarizing plate, it is necessary to bond them together 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, a general polarizer (polarizing film) is obtained by stretching at a high magnification in the transport direction, and its absorption axis coincides with the transport direction. In addition, since a conventional retardation film is produced by longitudinal stretching or transverse stretching, in principle, the in-plane slow axis is in the direction of 0 ° or 90 ° with respect to the longitudinal direction of the film. Therefore, as described above, a long polarizing film and / or retardation film is cut out at a specific angle in order to bond the polarizer so that the absorption axis of the polarizer and the slow axis of the stretched film are inclined at a desired angle. Therefore, it is necessary to manufacture by a batch method in which the film pieces are bonded one by one, so that the deterioration of the productivity and the decrease in the yield of the product due to the attachment of chips etc. have been cited as problems. In particular, in recent years when organic EL displays are becoming larger, the method of cutting the obtained retardation film obliquely and pasting it on a polarizer further improves the efficiency of use of the film and decreases productivity. Was needed.

  On the other hand, there is a method for producing a long retardation film that is stretched obliquely at a desired angle and whose slow axis is freely controllable in a direction that is neither 0 ° nor 90 ° with respect to the width direction of the film. Various proposals have been made. By using such a phase difference film, it is possible to produce a circularly polarizing plate by laminating a long polarizing film and a phase difference film with a roll-to-roll rather than a conventional batch type lamination. It becomes possible. As a result, productivity can be dramatically improved and yield can be greatly improved. In addition, since a circularly polarizing plate can be produced by laminating with rolls, tows and rolls, it is possible to increase the area of use of a long stretched film as a retardation film, even when used for large displays. The manufacturing cost of the circularly polarizing plate can be greatly 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 used for an antireflection film of a color image display device or an organic EL display is required to give a flat wavelength or a quarter wavelength retardation to light in the entire visible light range.

  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 has a retardation imparted to light having a long wavelength. It is required to have a negative wavelength dispersion (reverse wavelength dispersion) larger than the phase difference imparted to the 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 a film using a cellulose ester resin exhibits reverse wavelength dispersion. However, in order to obtain a phase difference of λ / 4 wavelength with a film using cellulose ester alone, it is necessary to increase the draw ratio or to increase the film thickness. In addition, since it is difficult to achieve λ / 4 in a wide wavelength region, the use of a specific additive increases the expression of phase difference, and the position of λ / 4 with respect to light in a wide wavelength region. Methods for obtaining the phase difference are being studied.

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

JP 2007-249180 A

  However, according to the study by the present inventors, using the compound of Patent Document 1, it is obtained when a stretching process at a high temperature and a high stretching ratio as required in the oblique stretching as described above is performed. It has been found that haze occurs in the stretched film.

  The present invention has been made for the purpose of solving such problems in the prior art. That is, the present invention minimizes the increase in haze when an optical film (λ / 4 retardation film) is produced by stretching at a high temperature and a high draw ratio in an optical film that can be used as a λ / 4 retardation film. An object of the present invention is to provide a means capable of preventing the occurrence of display unevenness such as contrast unevenness in an image display device when used for a circularly polarizing plate, for example, by exhibiting sufficient reverse wavelength dispersion while suppressing. .

  The present inventors have intensively studied to solve the above problems. In the process, it has been found that the occurrence of haze in the optical film according to the prior art as described above is due to local aggregation of the wavelength dispersion adjusting agent. This is because, according to the stretching process at a high temperature and a high stretching ratio, even when the wavelength dispersion adjusting agent is uniformly dispersed at the time of film formation, the state becomes easier to move at the time of stretching, and aggregation is promoted. it was thought. In addition, it was considered that the wavelength dispersion adjusting agent was more easily aggregated because a large force was suddenly applied to the film during stretching at a high stretch ratio. Furthermore, in particular, in the case of oblique stretching treatment, there was a circumstance that the method of applying force was not uniform, and it was considered that further non-uniform aggregation occurred in the film.

  Subsequently, the present inventors examined a method for improving the wavelength dispersion by improving the cohesiveness under the above-described situation. Then, the present inventors have arranged an electron-donating group and an electron-withdrawing group at the para position in the benzene ring existing in the molecule as in the compound represented by the general formula (1), respectively. Polarization is promoted, and the OH group present in the cellulose ester and the chromatic dispersion adjusting agent strengthen the interaction, so that the chromatic dispersion adjusting agent is placed in the vicinity of the molecular chain of the cellulose ester, thereby adjusting the chromatic dispersion even at high temperatures. It was thought that the aggregation of the agent was suppressed. Furthermore, by arranging the wavelength dispersion adjusting agent in the vicinity of the cellulose ester molecular chain, the wavelength dispersion adjusting agent is oriented with the orientation of the cellulose ester at the time of stretching, and also has high refractive index anisotropy due to polarization. It was speculated that the chromatic dispersion performance would be improved by the expression. As a result of searching for a compound based on the technical idea, it has been found that the use of a compound represented by the general formula (1) described later as a wavelength dispersion adjusting agent can solve the above-described problems, leading to the completion of the present invention. It was.

That is, the said subject regarding this invention is solved by the following means.
1. The optical film containing cellulose ester contains at least one compound represented by the following general formula ( 2 ), and the in-plane retardation measured at wavelengths of 450 nm, 550 nm, and 650 nm is R ₀ (450), respectively. , R ₀ (550) and R ₀ (650) satisfying the following formulas (a) to (c):

(Wherein L ₁ and L ₂ each independently represent a single bond or a divalent linking group, and R ₂₁ and R ₂₂ each independently represent an aromatic hydrocarbon ring which may have a substituent or Represents an aromatic hydrocarbon ring R ₂₃ represents — (C═O) CHR ₂₅ R ₂₆ , — (C═O) OR ₂₇ , — (C═O) NR ₂₇ R ₂₈ , —SO ₂ NR ₂₇ R ₂₈ or —CH═C (R ₂₉ ) represents R ₃₀ , R ₂₄ represents a hydroxy group, an alkyl group, an alkoxy group, an amino group, or an alkylamino group, and R ₂₅ and R ₂₆ each independently represents a hydrogen atom or an alkyl group. R ₂₇ and R ₂₈ each independently represents a hydrogen atom or a substituent, and R ₂₇ and R ₂₈ may combine to form a ring, and R ₂₉ and R ₃₀ each independently represent a hydrogen atom. Or replace , And _the at least one of _{R 29} and _{R 30} represents an electron-withdrawing group.)
(A) 110 nm ≦ Ro (550) ≦ 170 nm
(B) 0.72 ≦ Ro (450) / Ro (550) ≦ 1.03
(C) 0.83 ≦ Ro (550) / Ro (650) ≦ 1.03
2. 2. The optical film as described in 1 above, wherein an angle θ formed by a slow axis of the film with respect to a longitudinal direction of the film satisfies 0 ° <θ <90 ° ;

3 . 3. The optical film as described in 1 or 2 above, wherein the compound represented by the general formula (2) has at least one maximum absorption wavelength at 250 nm or more and 400 nm or less;
4 . 4. The optical film as described in any one of 1 to 3 above, wherein the total degree of substitution of acyl groups in the cellulose ester is 2.0 or more and 2.6 or less;
5 . The circularly-polarizing plate characterized by including the optical film of any one of said 1-4 .
6 . An image display device comprising the circularly polarizing plate as described in 5 above;
7 . Compound represented by the following general formula ( 2 ):

(Where L ₁ And L ₂ Each independently represents a single bond or a divalent linking group, R ₂₁ And R ₂₂ Each independently represents an aromatic hydrocarbon ring or a non-aromatic hydrocarbon ring which may have a substituent. R ₂₃ Is-(C = O) CHR ₂₅ R ₂₆ ,-(C = O) OR ₂₇ ,-(C = O) NR ₂₇ R ₂₈ , -SO ₂ NR ₂₇ R ₂₈ Or -CH = C (R ₂₉ ) R ₃₀ Represents. R ₂₄ Represents a hydroxy group, an alkyl group, an alkoxy group, an amino group or an alkylamino group. R ₂₅ And R ₂₆ Each independently represents a hydrogen atom or an alkyl group. R ₂₇ And R ₂₈ Each independently represents a hydrogen atom or a substituent. R ₂₇ And R ₂₈ And may combine to form a ring. R ₂₉ And R ₃₀ Each independently represents a hydrogen atom or a substituent, and R ₂₉ And R ₃₀ At least one of them represents an electron withdrawing group. )

  According to the present invention, in an optical film that can be used as a λ / 4 retardation film, an increase in haze is minimized when an optical film (λ / 4 retardation film) is produced by stretching at a high temperature and a high stretching ratio. Displaying sufficient reverse wavelength dispersion while suppressing the occurrence of display unevenness such as contrast unevenness in an image display device when used in a circularly polarizing plate, for example.

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.

  Hereinafter, specific embodiments for carrying out the present invention will be described in detail, but the technical scope of the present invention is not limited to the following specific embodiments.

  One embodiment of the present invention relates to an optical film containing a cellulose ester. In the present invention, the “optical film” is a functional film used for various display devices such as a liquid crystal display, a plasma display, and an organic EL display, and more specifically, a polarizing plate protective film for a liquid crystal display device, a retardation film. Films, antireflection films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, and the like are included.

  The optical film contains at least one compound represented by the following general formula (1).

(In the formula, EDG represents an electron-donating group. EWG represents an electron-withdrawing group. L ₁ and L ₂ each independently represent a single bond or a divalent linking group, and R ₁ and R ₂ each represent Independently represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocycle or a non-aromatic hydrocarbon ring which may have a substituent.
The optical film has the following formula (a) when the in-plane retardation measured at wavelengths of 450 nm, 550 nm, and 650 nm is R ₀ (450), R ₀ (550), and R ₀ (650), respectively. ) To (c) are satisfied.

(A) 110 nm ≦ R ₀ (550) ≦ 170 nm
(B) 0.72 ≦ R ₀ (450) / R ₀ (550) ≦ 1.03
(C) 0.83 ≦ R ₀ (550) / R ₀ (650) ≦ 1.03
The mechanism by which the aggregation of the wavelength dispersion adjusting agents that cause haze is suppressed by containing the compound represented by the general formula (1) is not completely clear, but is represented by the general formula (1). In the benzene ring existing in the molecule, the electron donating group and the electron withdrawing group are arranged in the para position on the benzene ring, respectively, so that the polarization in the compound is promoted, and the OH group existing in the cellulose ester and wavelength dispersion adjustment. It is considered that the chromatic dispersion adjusting agent is arranged in the vicinity of the molecular chain of the cellulose ester by strengthening the interaction with the agent, thereby suppressing aggregation of the chromatic dispersion adjusting agent even in a high temperature state. Furthermore, by arranging the wavelength dispersion adjusting agent in the vicinity of the cellulose ester molecular chain, the wavelength dispersion adjusting agent is oriented with the orientation of the cellulose ester at the time of stretching, and also has high refractive index anisotropy due to polarization. It is considered that the chromatic dispersion performance is improved by the development.

1. Optical film The optical film according to the present invention contains a cellulose ester.
<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. Can be given. The butyryl group that can be contained in the cellulose ester may be linear or branched.

  In the present invention, the total substitution degree of the acyl group of the cellulose ester can be about 1.9 to 3.0. The total substitution degree of the acyl group is preferably smaller from the viewpoint of enhancing the retardation development. On the other hand, when the degree of substitution becomes small, the interaction between cellulose esters becomes strong, so that the additives easily aggregate, and the in-plane retardation value and haze unevenness increase. For this reason, it is preferable that the total substitution degree of an acyl group is 1.9-2.8, and it is especially preferable that it is 2.0-2.6.

  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 6 × 10 ^{4 to} 3 × 10 ⁵ in order to increase the mechanical strength of the obtained film, and in the range of 7 × 10 ⁴ to 2 × 10 ⁵ . More preferably.

  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 of the calcium (Ca) component in a cellulose ester becomes like this. Preferably it is 60 mass ppm or less, More preferably, it is 0-30 mass ppm. The content of the magnesium (Mg) component in the cellulose ester is preferably 0 to 70 ppm by mass, and particularly preferably 0 to 20 ppm by mass.

  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 content 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 produced by a known method. Specifically, for example, it can be synthesized with reference to the method described in JP-A-10-45804. The cellulose that is the raw material of the cellulose ester is not particularly limited, and may be cotton linter, wood pulp, kenaf, and the like. You may mix and use the cellulose ester from which a raw material differs.

  The optical film of the present invention may be used by mixing a plurality of cellulose esters having an acyl group having 3 to 6 carbon atoms.

  In addition to the cellulose ester having an acyl group having 3 to 6 carbon atoms, the optical film of the present invention may be a cellulose derivative (for example, a cellulose ester resin, a cellulose ether resin, etc.), a polycarbonate resin, or a polystyrene resin. Resins, polysulfone resins, polyester resins, polyarylate resins, (meth) acrylic resins, olefin resins (eg, norbornene resins, cyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbons) Resin) may be used in combination. As the resin used in combination, a cellulose derivative, a (meth) acrylic resin, a polycarbonate resin, and a cyclic olefin resin are preferable, a cellulose derivative is more preferable, and a cellulose ester resin is most preferable.

  A cellulose derivative is a compound (compound having a cellulose skeleton) using cellulose as a raw material. Examples of cellulose derivatives include cellulose ether (eg, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, etc.), cellulose ester (details will be described later), cellulose ether ester (eg, acetyl methyl cellulose, acetyl ethyl cellulose, acetyl hydroxy). Ethyl cellulose, benzoyl hydroxypropyl cellulose, etc.), cellulose carbonate (eg, cellulose ethyl carbonate, etc.), cellulose carbamate (eg, cellulose phenyl carbamate, etc.) and the like, and cellulose ester is preferred.

(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 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 the copolymerization monomer in the copolymer of methyl methacrylate and other copolymerization monomers 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; An alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl moiety having a hydroxyl group, which can form a lactone ring structure described later; an α, β-unsaturated acid such as acrylic acid or methacrylic acid; maleic acid, fumaric acid, Unsaturated divalent carboxylic acids such as itaconic acid; aromatic vinyl compounds such as styrene and α-methylstyrene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted Acrylamide such as maleimide, glutaric anhydride, acryloylmorpholine (ACMO) Derivatives; N-vinylpyrrolidone (VP) and the like are included. 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 hydroxyl 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 resulting 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 (3).

  In the general formula (3), Ra to Rc each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. Examples of organic residues include linear or branched alkyl groups, linear or branched alkylene groups, aryl groups, -OAc groups (Ac is an acetyl group), -CN groups, and the like. The lactone ring structure represented by the formula (3) is a structure derived from an alkyl (meth) acrylate having a hydroxyl group, as will be described later.

  The (meth) acrylic resin containing a lactone ring structure further includes 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 hydroxyl group, an unsaturated carboxylic acid A structural unit derived from an acid, a monomer represented by the following general formula (4), or the like may further be included. Rd in the general formula (4) 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: acetyl group), -CN group, acyl group or -C-OR group (R is a hydrogen atom or 1 to carbon atoms) 20 organic residues).

  The content ratio of the lactone ring structure represented by the formula (3) in the (meth) acrylic resin containing a lactone ring structure is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, More preferably, it is 15-70 mass%. When the content of the lactone ring structure is more than 90% by mass, the molding processability is low, and the flexibility of the obtained film tends to be low. When the content of the lactone ring structure is less than 5% by mass, it is difficult to obtain a film having a necessary retardation, and heat resistance, solvent resistance, and surface hardness may not be sufficient.

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

  In the (meth) acrylic resin containing a lactone ring structure, the content ratio of the structural unit derived from the hydroxyl group-containing monomer, the unsaturated carboxylic acid or the monomer represented by the general formula (4) is preferably preferably 0 to 30. It is mass%, More preferably, it is 0-20 mass%, More preferably, it is 0-10 mass%.

  The (meth) acrylic resin containing a lactone ring structure is obtained by polymerizing a monomer component containing at least an alkyl (meth) acrylate having a hydroxyl group and another alkyl (meth) acrylate to form a hydroxyl group in the molecular chain. It can be produced through a step of obtaining a polymer having an ester group; 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 less than 8.0 × 10 ⁴ , the resulting film tends to be brittle, and if it exceeds 5.0 × 10 ⁵ , the resulting film has a high haze. Prone.

  The weight average molecular weight Mw of the (meth) acrylic resin can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
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: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2800000-500 calibration curves with 13 samples are used. The 13 samples are preferably used at approximately equal intervals.

  The (meth) acrylic resin may be one type or a mixture of two or more types.

The content of the other resin in the mixture of the cellulose ester having an acyl group having 3 or more carbon atoms and the other resin is preferably about 5 to 70% by mass with respect to the entire resin component.
<Compound represented by the general formula (1)>
The optical film according to the present invention contains a compound represented by the following general formula (1).

  Hereinafter, the compound represented by the general formula (1) will be described in detail.

In the general formula (1), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. Here, as a bivalent coupling group, a C1-C10 alkylene group, a C2-C10 alkenylene group, a C2-C10 alkynylene group, -O-,-(C = O), for example. -,-(C = O) -O-, -NR _L- , -S-,-(O = S = O)-,-(C = O) -NR _L -and -NR _L- (C = O )-(Wherein _RL is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), one or more selected from the group consisting of. L ₁ and L ₂ are preferably —O—, — (C═O) —O—, —O— (C═O) —, — (C═O) —NH— or —NH— (C═O ) −.

In the general formula (1), each of R ₁ and R ₂ independently represents an optionally substituted aromatic hydrocarbon ring, non-aromatic hydrocarbon ring, aromatic heterocycle or non-aromatic heterocycle. Represent.

  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 a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornene ring, and the like, more preferably a cyclohexane ring and a cyclopentane ring. It is.

  The aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, and 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, triazole ring, benzimidazole ring, Pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, benzimidazole ring, perimidine ring, quinazoline ring, azulene ring, dibenzofuran ring, dibenzothiophene ring, dibenzocarbazole ring, benzodifuran ring, benzodithiophene ring, A phenanthroline ring and the like are included, and a pyridine ring, a benzothiazole ring, and a benzoxazole ring are preferable.

  The non-aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, but 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, piperidine ring and the like are included, and pyridone ring, imide ring and pyrrolidine ring are more preferable.

Here, R ₁ and / or R ₂ in the general formula (1) may further have a substituent, and examples of the substituent include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.). , Alkyl groups (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl groups (cyclohexyl group, cyclopentyl group, 4-n-dodecyl) Cyclohexyl group etc.), alkenyl group (vinyl group, allyl group etc.), cycloalkenyl group (2-cyclopenten-1-yl, 2-cyclohexen-1-yl group etc.), alkynyl group (ethynyl group, propargyl group etc.), Aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidi) Group, 2-benzothiazolyl group, 2-pyridyl group, etc.), cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group) , 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group ( Formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-) Anilino group, diphenylamino group, etc.), acyl Amino 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.), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), 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 − Nzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N , N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, and the like. R ₁ and R ₂ are each independently preferably an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring or an aromatic heterocyclic ring, more preferably an aromatic hydrocarbon ring or a non-aromatic hydrocarbon ring. . The aromatic hydrocarbon ring is preferably a substituted or unsubstituted benzene ring, more preferably a benzene ring having a substituent, and still more preferably a benzene ring having a substituent at the 4-position. The non-aromatic hydrocarbon ring is preferably a substituted or unsubstituted cyclohexane ring, more preferably a cyclohexane ring having a substituent, and still more preferably a cyclohexane ring having a substituent at the 4-position.

  In the general formula (1), EWG represents an electron withdrawing group. The electron withdrawing group is a group having a Hammett's substituent constant σp value larger than 0, more preferably a group having a σp value larger than 0.1, and a group having a σp value larger than 0.3. More preferably. Regarding the Hammett's substituent constant σp value, for example, Naoki Inamoto's “Hammett's rule-structure and reactivity-” (Maruzen), edited by the Chemical Society of Japan “New Experimental Chemistry Course 14 Synthesis and Reaction V of Organic Compounds” 2605 (Maruzen) and Tadao Nakatani's "Explanation on Theoretical Organic Chemistry", page 217 (Tokyo Kagaku Dojin), etc., and Chemical Review, 91, 165-195 (1991) are described in detail.

Preferably, EWG is preferably a cyano group (σp = 0.66), — (C═O) CHR ₂₅ R ₂₆ (σp = 0.50), — (C═O) OR ₂₇ (σp = 0.45), — (C═O) NR ₂₇ R ₂₈ (σp = 0.36), —O (C═O) R ₂₇ (σp = 0.31), —OSO ₂ R ₂₇ (σp = 0.36), —SO ₂ R ₂₇ (σp = 0.72), —SO ₂ NR ₂₇ R ₂₈ (σp = 0.57) or —CH═ (R ₂₉ ) R ₃₀ may be mentioned. Here, R ₂₅ and R ₂₆ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R ₂₇ and R ₂₈ each independently represent a hydrogen atom or a substituent, and examples of the substituent include all the examples of the substituent described above for R ₁ and R ₂ . R ₂₇ and R ₂₈ may combine to form a ring. R ₂₉ and R ₃₀ are each independently a hydrogen atom or a substituent, and at least one of R ₂₉ and R ₃₀ represents an electron withdrawing group, and a group preferable as EWG is also preferable. As EWG, a cyano group, — (C═O) OR ₂₇ , —SO ₂ R ₂₇ or —CH═ (R ₂₉ ) R ₃₀ is more preferable, and a cyano group or —CH═ (R ₃₁ ) R ₃₂ is more preferable. .

  In the general formula (1), EDG represents an electron donating group. The electron donating group is a group having a Hammett's substituent constant σp value of 0 or less, more preferably a group of −0.85 to 0.

  EDG is preferably a hydroxy group (σp = −0.37), an alkyl group (methyl group (σp = −0.17), an ethyl group (σp = −0.15), an n-propyl group, an isopropyl group (σp). = −0.15), tert-butyl group (σp = −0.20), n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (cyclohexyl group (σp = −0.22), cyclopentyl group ( σp = −0.02), 4-n-dodecylcyclohexyl group, etc.), alkoxy group (methoxy group (σp = −0.27), ethoxy group (σp = −0.24), isopropoxy group (σp = −) 0.45), tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), amino group (amino group (σp = −0.66), methylamino group (σp = −0.84)), Dimethylamino (Σp = −0.83), anilino group (σp = −0.40), N-methyl-anilino group, diphenylamino group, etc.), more preferably an alkyl group, an alkoxy group, and an amino group, an alkyl group, Alkoxy groups are particularly preferred.

  A preferred form of the compound represented by the general formula (1) is a compound of the following general formula (2).

(In the formula, L ₁ and L ₂ have the same meanings as in the general formula (1). R ₂₁ and R ₂₂ are each independently an aromatic hydrocarbon ring or a non-aromatic group which may have a substituent. R ₂₃ represents — (C═O) CHR ₂₅ R ₂₆ , — (C═O) OR ₂₇ , — (C═O) NR ₂₇ R ₂₈ , —SO ₂ NR ₂₇ R _28, or —CH. ═C (R ₂₉ ) R ₃₀ R ₂₄ represents a hydroxy group, an alkyl group, an alkoxy group, an amino group or an alkylamino group, and R ₂₅ and R ₂₆ each independently represent a hydrogen atom or an alkyl group. R ₂₇ and R ₂₈ each independently represents a hydrogen atom or a substituent, and R ₂₇ and R ₂₈ may combine to form a ring, and R ₂₉ and R ₃₀ each independently represent a hydrogen atom or a substituent. Base At least one of R ₂₉ and _{R 30} represents an electron-withdrawing group.)
The compounds represented by the general formula (1) and the general formula (2) described above preferably have at least one absorption maximum wavelength at 250 nm or more and 400 nm or less. The maximum absorption wavelength referred to here is obtained by dissolving the compounds represented by the general formulas (1) and (2) in tetrahydrofuran (no polymerization inhibitor) at a concentration of 1.0 × 10 ⁻⁵ mol / L. The maximum of the absorption peak when the absorption wavelength is measured at 25 ° C. with a normal absorption spectrophotometer. The maximum absorption wavelength is not necessarily the maximum absorption wavelength, and a plurality of maximum points may exist. When the maximum absorption wavelength is less than 250 nm, the effect of improving the wavelength dispersibility is reduced. When the maximum absorption wavelength is 400 nm or more, the film is colored, so that the amount of the compound added is limited.

  Hereinafter, although the example of a compound represented by General formula (1) is given, of course, it is not restrict | limited to these.

  <Examples of compounds>

  The compound represented by the general formula (1) can be synthesized by a known method. For example, the exemplary compound D-8 can be synthesized according to the following scheme.

  [Synthesis Example of Exemplified Compound D-8]

  The content of the compound represented by the general formula (1) in the optical film according to the present invention is appropriately set to such an extent that desired wavelength dispersion adjusting ability and retardation development property can be imparted. Specifically, the content of the compound represented by the general formula (1) is preferably 1 to 15% by mass and more preferably 2 to 10% by mass with respect to 100% by mass of the cellulose ester. . If content of the said compound is 1 mass% or more, desired retardation development and wavelength dispersion property can be provided to an optical film. Moreover, if content of the said compound is 15 mass% or less, an optical film will not produce bleeding out easily.

  The optical film according to the present invention may further contain various additives as described below as necessary.

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

  The sugar ester that can be used in the present invention is 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 esters 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 esters include the compounds described in JP-A No. 62-42996 and JP-A No. 10-237084.

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

(Plasticizer)
The optical film of the present invention may 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, and the like). 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 succinic acid, glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. In particular, a compound using succinic acid, 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 carbon number 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, etc.); 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 exists in the range of 0.5-30.0 mass% with respect to 100 mass% of cellulose esters. 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.

  Among them, an ultraviolet absorber having a molecular weight of 400 or more is difficult to volatilize at a high boiling point, and is difficult to scatter even at high temperature molding. Therefore, even if the addition amount is relatively small, weather resistance is imparted to the obtained film. Can do.

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. Specific examples thereof include polyester acid, polyether ester acid, fatty acid, fatty acid amide, polycarboxylic acid, alkylene oxide, and polyalkylene oxide. , A compound obtained by aminating polyoxyethylene fatty acid ester, polyoxyethylene glycerin fatty acid ester, and 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.

(Retardation control agent)
In order to improve the display quality of display devices such as liquid crystal display devices, a retardation control agent is added to the optical film, or an alignment film is formed to provide a liquid crystal layer. An optical compensation ability can be imparted to the optical film by combining the foundation. As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in the specification of European Patent 911,656A2 may be used as a retardation control agent. it can. Or the rod-shaped compound of Unexamined-Japanese-Patent No. 2006-2025 is mentioned. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound is particularly preferably an aromatic heterocyclic ring including an aromatic heterocyclic ring in addition to an aromatic hydrocarbon ring, and the aromatic heterocyclic ring is generally an unsaturated hetero ring. It is a ring. Of these, the 1,3,5-triazine ring described in JP-A-2006-2026 is particularly preferable.

  The addition amount of these retardation control agents is preferably 0.5 to 20% by mass and more preferably 1 to 10% by mass with respect to 100% by mass of the resin used as the film substrate.

(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 has in-plane retardation values Ro measured at wavelengths of 450 nm, 550 nm, and 650 nm under the conditions of a temperature of 23 ° C. and a relative humidity of 55%, respectively, Ro (450) and Ro (550). And Ro (650), Ro (450), Ro (550), and Ro (650) satisfy the following formulas (a) to (c).

(A) 110 nm ≦ Ro (550) ≦ 170
(B) 0.72 ≦ Ro (450) / Ro (550) ≦ 1.03
(C) 0.83 ≦ Ro (550) / Ro (650) ≦ 1.03
An optical film in which Ro (550) satisfies the formula (a) can preferably function as a λ / 4 retardation film. Especially, it is more preferable to satisfy | fill 120 <= Ro (550) <= 160, and it is still more preferable to satisfy | fill 130 <= Ro (550) <= 150.

  An optical film in which Ro (450), Ro (550), and Ro (650) satisfy the above formulas (b) and (c) is excellent in wavelength dispersion, and can function more preferably as a λ / 4 retardation film. In addition, light leakage or the like when an image display device using an optical film is displayed in black can be reduced. Specifically, when the formula (b) is satisfied, the blue reproducibility is high, and when the formula (c) is satisfied, the red reproducibility is high. Especially, it is more preferable to satisfy | fill 0.79 <= Ro (450) / Ro (550) <= 0.89, and it is more preferable to satisfy | fill 0.84 <= Ro (550) / Ro (650) <= 0.93. .

  Ro (550) representing phase difference development, Ro (450) / Ro (550) and Ro (550) / Ro (650) representing wavelength dispersion should be adjusted according to the compound used in the present invention and stretching conditions. Can do. In order to satisfy all of the above formulas (a) to (c), the compound represented by the general formula (1) used in the present invention may be contained, and the stretching conditions may be further adjusted.

  The optical film of the present invention has a thickness direction retardation value Rt measured at a wavelength of 550 nm under the conditions of 23 ° C. and 55% RH, where Rt (550) is Rt (550), It is preferable to satisfy 50 ≦ Rt (550) ≦ 250.

  The above Ro and Rt are defined by the following formulas (I) and (II), respectively.

Formula _{(I): Ro = (n} x -n y) × d
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d
In [Formula (I) and (II), n _x represents a refractive index in the slow axis direction x in which the refractive index is maximized in the plane direction of the optical film. n _y represents a 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. )
The above Ro 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) In-plane retardation values Ro (450) and Ro (550) 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 Ro (650) are measured on 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 phase difference 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) Ro (450), Ro (550) and Ro (650) measured in 2) above, and R (φ) measured in each wavelength of 450 nm, 550 nm or 650 nm in 3) above, and 1) above in the measured average refractive index and the film thickness d, by _AxoScan, calculates the n x, _{n y} and _{n z.} Based on the above formula (II), thickness direction retardation values Rt (450), Rt (550), and Rt (650) at wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are calculated.

The optical film of the present invention, N _z defined by the following formula (d) preferably satisfies the following formula (e).

(D) N _z = Rt (550) / Ro (550) +0.5
(E) 0 ≦ N _z ≦ 1
Satisfies N _z is the formula of (e), the phase difference value Rt in the thickness direction, because relatively smaller than the retardation value Ro in the plane direction, an image display device comprising the optical film of the present invention obliquely The change in color when observed from the direction can be reduced.

  The angle θ (orientation angle) formed by the slow axis in the film plane with respect to the longitudinal direction (conveying direction) of the optical film of the present invention is preferably 0 ° <θ <90 °, more preferably 30 to 30 °. 60 °, particularly preferably 40 ° <θ <50 °, and most preferably θ = 45 °.

  If θ is within this range, an optical film having a slow axis in an oblique direction with respect to the long direction (transport direction) and a polarizing film having a transmission axis parallel to the long direction (transport direction), A circularly polarizing plate can be easily manufactured by unwinding from the rolls and pasting them together in a roll-to-roll manner so that the longitudinal directions of the rolls overlap each other. There is little cut loss of the film, which is advantageous in production. The orientation angle 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.

  As described above, the optical film of the present invention has a high retardation in the in-plane direction and exhibits sufficient reverse wavelength dispersion. Therefore, the optical film of the present invention can impart a high retardation to light in a wide wavelength region.

  The optical film of the present invention is used as an optical film for image display devices such as organic EL display devices and liquid crystal display devices. Specifically, it is used as a polarizing plate protective film, a retardation film, an optical compensation film, and an antireflection film, and preferably used as a λ / 4 retardation film.

The λ / 4 retardation film has an in-plane retardation value Ro of about ¼ of a predetermined light wavelength (usually 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 for an antireflection film of an organic EL display device.
<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 An optical film containing a cellulose ester is produced by the solution casting method. A1) A step of preparing a dope by dissolving at least a cellulose ester and, if necessary, other additives in a solvent. A2) a step of casting the dope on an endless metal support, A3) a step of evaporating the solvent from the cast dope to form a web, A4) a step of peeling the web from the metal support, and A5) After drying, it includes a step of drawing to obtain a film.

A1) Dope preparation step In a dissolution vessel, a dope is prepared by dissolving cellulose ester and other additives as required 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 cellulose ester is preferably 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 angle θ formed by the slow axis in the plane of the optical film and the film transport direction is in the range of 0 <θ <90 °, and therefore the web is stretched in an oblique direction (diagonal) Stretched). The oblique direction is a direction having an angle in the range of more than 0 ° and less than 90 ° 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 (W0 is before stretching, W is the width after stretching), and the film thickness of the obtained optical film and the required retardation It is possible to set appropriately according to the above.

  However, according to the present invention, the aggregation of the wavelength dispersion adjusting agent (the compound represented by the general formula (1)) hardly occurs even when the stretching treatment is performed at a high temperature and / or a high stretching ratio. There is one. Therefore, in a preferred embodiment of the present invention, the draw ratio is preferably in the range of 1.3 to 3.0 times, more preferably in the range of 1.5 to 2.8 times. Moreover, the temperature at the time of an extending | stretching process becomes like this. Preferably it exists in the range of 120-230 degreeC, More preferably, it exists in the range of 150-220 degreeC, More preferably, it exists in the range of 150-210 degreeC.

  The method for producing the film by oblique stretching is not particularly limited. 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 shape 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 less 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.
<Circularly polarizing plate>
The circularly polarizing plate of the present invention includes a polarizer (linearly polarizing film) and the optical film of the present invention disposed on at least one surface thereof. The optical film of the present invention may be directly bonded to 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 polarizing film and the dye polarizing film may generally be a film obtained by uniaxially stretching a polyvinyl alcohol 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 transmission 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.

  The angle formed by the transmission axis of the polarizer and the in-plane slow axis of the optical film of the present invention is in the range of more than 0 ° and less than 90 °, 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 transparent protective film or the λ / 4 retardation film is disposed on the outermost surface of the display, the transparent hard coat layer, the antiglare layer, the outermost surface of the transparent protective film or the λ / 4 retardation film, An antireflection layer or the like may be further provided.

  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.
<Image display device>
The image display device of the present invention includes the optical film of the present invention. Examples of the image display device of the present invention include an organic EL display device and 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 circularly polarizing plate 20 includes a λ / 4 retardation film 20A and a polarizer 20B. The λ / 4 retardation film 20A can be the optical film of the present invention, and the polarizer 20B is a linear polarizing film.

  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 only needs to be capable of transmitting 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 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 disclosed in International Publication No. 96/34514, JP-A Nos. 9-127885 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.

  When light including linearly polarized light a1 and b1 is incident from the outside in parallel to the normal line of the display screen of the organic EL display device 10, only linearly polarized light b1 parallel to the transmission axis direction of the polarizer 20B 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.

  And, in the λ / 4 retardation film 20A using the optical film of the present invention, since the wavelength dispersion adjusting agent (compound represented by the general formula (1)) exhibits sufficient reverse wavelength dispersion, A phase difference of λ / 4 can be imparted to the light. 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 using the optical film of the present invention has high retardation development and excellent wavelength dispersion, the thickness of the film can be reduced. Therefore, the difference between the color in the front direction and the color in the oblique direction can be reduced. As a result, visibility from an oblique direction can be improved.

  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, and includes a polarizer 52 and protective films 54 and 56 that sandwich the polarizer 52.

  The polarizing plate 60 is disposed on the backlight 70 side, and includes a polarizer 62 and protective films 64 and 66 that sandwich the polarizer 62. One of the protective films 56 and 64 may be omitted as necessary.

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

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" may be used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

[Example 1]
Various cellulose esters A to E shown in Table 1 below were prepared and used for the production of the following optical films.

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

Among the components of the following fine particle addition liquid, methylene chloride was put into a dissolution tank, and the prepared fine particle dispersion was slowly added with sufficient stirring with the following addition amount. Subsequently, after being dispersed with an attritor so that the particle size of the secondary particles of the fine particles becomes a predetermined size, the fine particles are filtered through Finemet NF (manufactured by Nippon Seisen Co., Ltd.) to obtain a fine particle additive solution. :
(Fine particle additive)
Methylene chloride: 99 parts by mass Fine particle dispersion: 5 parts by mass.

Among the main dope components below, methylene chloride and ethanol were charged into a pressure dissolution tank. Next, the following cellulose ester C, sugar ester S, exemplary compound D-2 and the fine particle addition liquid prepared above were added with stirring, and heated and stirred to completely dissolve. The obtained solution was used as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244:
(Main dope composition)
Methylene chloride: 520 parts by mass Ethanol: 45 parts by mass Cellulose ester: Cellulose ester C (acetyl group substitution degree 2.2, total acyl group substitution degree 2.2, number average molecular weight (Mn) is 57000) 100 parts by mass Sugar ester S : 5 parts by mass Wavelength dispersion regulator: Exemplified compound D-2 4 parts by mass Fine particle additive solution: 1 part by mass

  The structure of sugar ester S is shown below.

  The obtained dope was uniformly cast on a stainless belt support using an endless belt casting apparatus. On the stainless steel belt support, the solvent in the dope film cast (cast) was evaporated until the residual solvent amount became 75%, and the obtained web was peeled off from the stainless steel belt support. The peeled web was conveyed while being gripped by a clip of a tenter stretching apparatus. Next, the obtained film was dried while being conveyed by a number of rollers in a drying zone. The width direction end of the film held by the tenter clip was slit-removed with a laser cutter, and then wound up to obtain an original film.

  Unwinding the obtained raw film, stretched in an oblique direction inclined by 45 ° with respect to the film conveying direction at a glass transition temperature Tg + 20 ° C stretching temperature of the raw film, and a stretching ratio of 2.5 times, An optical film 1 was obtained. The film thickness of the optical film 1 was 40 μm. The angle formed by the in-plane slow axis of the optical film 1 and the film transport direction was 45 °.

<Preparation of optical films 2-22>
In the production of the optical film 1, optical films 2 to 21 were produced in the same manner except that the types of the cellulose ester and the wavelength dispersion adjusting agent were changed as shown in Table 2 below.

  Further, in the production of the optical film 1, the optical film 22 was produced in the same manner except that the wavelength dispersion adjusting agent was not added.

  The angles formed by the in-plane slow axes of the obtained optical films 2 to 22 and the film transport direction were all 45 °. Moreover, all the film thicknesses of the optical films 2-22 were 40 micrometers.

  Furthermore, D-1 to D-48 described in Table 2 below represent the exemplified compounds D-1 to D-48 described above as specific examples of the wavelength dispersion adjusting agent. Moreover, the structures of the comparative compounds CO-1 to CO-4 described in Table 2 below are as follows.

<Evaluation>
(Optical characteristics of optical film)
Ro (550) representing the retardation development property of each of the optical films 1 to 22, Ro (450) / Ro (550) and Ro (550) / Ro (650) representing the wavelength dispersion characteristics were measured as follows. did.

1) The optical film was conditioned at 23 ° C. and 55% RH. The average refractive index at each of wavelengths 450 nm, 550 nm and 650 nm was measured for the optical film after humidity control using an Abbe refractometer and a spectral light source, respectively;
2) In-plane phase difference (retardation value) Ro (450) when light having wavelengths of 450 nm, 550 nm, and 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface, The values of Ro (550) and Ro (650) were measured with AxoScan. The measurement was performed under conditions of 23 ° C. and 55% RH;
3) Ro (450) / Ro (550) was calculated from Ro (450) and Ro (550) measured in 2).

(Uneven phase difference)
<R0 unevenness>
Ten points of R0 (550) were measured at intervals of 50 mm in the width direction of the optical film, and the difference between the maximum value and the minimum value of all measured values was evaluated as the unevenness of R0 according to the following criteria.
A: R0 unevenness of less than 1 nm B: R0 unevenness of 1 nm or more and less than 2 nm C: R0 unevenness of 2 nm or more and less than 4 nm D: R0 unevenness of 4 nm or more and less than 6 nm E: R0 unevenness of 6 nm or more where C 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)>
Measure 10 points, R0 (550) and R0 (450) at intervals of 50 mm in the width direction of the optical film, and find the difference between the maximum value and the minimum value with R0 (450) / R0 (550) of all measured values. The unevenness of R0 (450) / R0 (550) was evaluated 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 0.01 or more 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. Is preferred. The evaluation results are shown in Table 2 below.

  As is clear from Table 2, it can be seen that the optical film according to the present invention has high retardation and excellent wavelength dispersion. Moreover, it is clear that the optical film according to the present invention has little retardation unevenness. On the other hand, the optical film according to the comparative example, particularly the optical film 22 that does not contain the wavelength dispersion adjusting agent, has very low retardation and is inferior in wavelength dispersion. Even if such an optical film is used in an organic EL display device, reflection of external light cannot be sufficiently suppressed.

[Example 2]
<Preparation of Circular Polarizing Plate 1>
(Production of polarizer)
A 120 μm-thick polyvinyl alcohol film 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 composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds. Subsequently, it was immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water, washed with water and dried to obtain a polarizer having a thickness of 20 μm.

  One surface of the optical film 1 produced in Example 1 was subjected to alkali saponification treatment. Konica Minolta Tack Film KC6UA (manufactured by Konica Minolta Advanced Layer Co., Ltd.) was prepared, and one surface was similarly subjected to alkali saponification treatment. In any case, the saponified surface is a bonding surface with the polarizer. Then, the saponified surface of the optical film 1 was bonded to one surface of the polarizer via a 5% aqueous solution of polyvinyl alcohol as an adhesive. In addition, the saponified surface of the Konica Minolta-tack film KC6UA was bonded to the other surface of the polarizer through a 5% aqueous solution of polyvinyl alcohol to produce a circularly polarizing plate 1. The optical film 1 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 1 was 45 °.

<Production of circularly polarizing plates 2 to 22>
In the production of the circularly polarizing plate 1, the circularly polarizing plates 2 to 22 were produced in the same manner as the circularly polarizing plate 1 except that the optical film 1 was changed to each of the optical films 2 to 22.

<Production of Organic EL Display Device 1>
A light reflecting electrode made of chromium having a thickness of 80 nm was formed on a glass substrate by sputtering. 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. Further, each of the RGB light emitting layers was formed by patterning on the hole transport layer 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 (Alq ₃ ) as a host and a light-emitting compound [4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H-pyran] (DCM). Were co-evaporated (mass ratio 99: 1), and the green light-emitting layer was formed by co-evaporating Alq ₃ and the luminescent compound coumarin 6 (mass ratio 99: 1) as a host. The blue light emitting layer was formed by co-evaporating the following compound Balq and the light emitting compound Perylene as a host (mass 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 the first cathode, a thin film made of aluminum having a thickness of 2 nm was formed as a second cathode to obtain an organic light emitting layer. 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 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. . Further, 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 produced circularly polarizing plate 1 was bonded via an adhesive to produce an organic EL display device 1. The circularly polarizing plate 1 was bonded so that the optical film 1 was positioned on the insulating film side.

<Production of organic EL display devices 2 to 22>
In the production of the organic EL display device 1, organic EL display devices 2 to 22 were produced in the same manner as the organic EL display device 1 except that the circularly polarizing plate 1 was changed to the respective circularly polarizing plates 2 to 22.

<Evaluation>
Color unevenness when each organic EL display device 1 to 22 was displayed in black was evaluated by the following method.

(Evaluation criteria for uneven color)
A: No difference in color depending on the position B: A difference in color is observed depending on the position, but there is no problem in use C: There is a difference in color depending on the position, and it cannot be used as a product Yes D: The color difference is large depending on the position, and the evaluation result is such that it cannot be used as a product. The evaluation results are shown in Table 3 below.

  As is apparent from Table 3, the organic EL display device of the present invention shows almost no color unevenness even when displaying black. It can be seen that the organic EL display device of the present invention is superior in image reproducibility as compared with the organic EL display device according to the comparative example.

DESCRIPTION OF SYMBOLS 10 Organic electroluminescent display device 14 Light emitting layer 20 Circular polarizing plate 20A (lambda) / 4 phase difference film 20B Polarizer 30 Liquid crystal display device 40 Liquid crystal cell 50, 60 Polarizing plate 52, 62 Polarizer 54, 56, 64, 66 Protective film

Claims (7)

In the optical film containing cellulose ester, it contains at least one compound represented by the following general formula ( 2 ), and the retardation in the in-plane direction measured at wavelengths of 450 nm, 550 nm and 650 nm is respectively Ro (450), An optical film characterized by satisfying the following formulas (a) to (c) when Ro (550) and Ro (650):
(Wherein L ₁ and L ₂ each independently represent a single bond or a divalent linking group, and R ₂₁ and R ₂₂ each independently represent an aromatic hydrocarbon ring which may have a substituent or Represents an aromatic hydrocarbon ring R ₂₃ represents — (C═O) CHR ₂₅ R ₂₆ , — (C═O) OR ₂₇ , — (C═O) NR ₂₇ R ₂₈ , —SO ₂ NR ₂₇ R ₂₈ or —CH═C (R ₂₉ ) represents R ₃₀ , R ₂₄ represents a hydroxy group, an alkyl group, an alkoxy group, an amino group, or an alkylamino group, and R ₂₅ and R ₂₆ each independently represents a hydrogen atom or an alkyl group. R ₂₇ and R ₂₈ each independently represents a hydrogen atom or a substituent, and R ₂₇ and R ₂₈ may combine to form a ring, and R ₂₉ and R ₃₀ each independently represent a hydrogen atom. Or replace , And _the at least one of _{R 29} and _{R 30} represents an electron-withdrawing group.)
(A) 110 nm ≦ Ro (550) ≦ 170 nm
(B) 0.72 ≦ Ro (450) / Ro (550) ≦ 1.03
(C) 0.83 ≦ Ro (550) / Ro (650) ≦ 1.03   2. The optical film according to claim 1, wherein an angle θ formed by a slow axis of the film with respect to a longitudinal direction of the film satisfies 0 ° <θ <90 °. The compound represented by the general formula (2), characterized in that it has at least one maximum absorption wavelength in the 250nm or 400nm or less, the optical film according to claim 1 or 2. The optical film according to any one of claims 1 to 3 , wherein the total degree of substitution of acyl groups in the cellulose ester is 2.0 or more and 2.6 or less. Characterized in that it comprises an optical film of any one of claims 1-4, circularly polarizing plate. An image display device comprising the circularly polarizing plate according to claim 5 . Compound represented by the following general formula ( 2 ):
( Wherein L ₁ and L ₂ each independently represent a single bond or a divalent linking group, and R ₂₁ and R ₂₂ each independently represent an aromatic hydrocarbon ring which may have a substituent or Represents an aromatic hydrocarbon ring, and R ₂₃ represents — (C═O) CHR ₂₅ R ₂₆ , — (C═O) OR ₂₇ , — (C═O) NR ₂₇ R ₂₈ , —SO ₂ NR ₂₇ R ₂₈ or —CH═C (R ₂₉ ) represents R ₃₀ , R ₂₄ represents a hydroxy group, an alkyl group, an alkoxy group, an amino group, or an alkylamino group, and R ₂₅ and R ₂₆ each independently represents a hydrogen atom or an alkyl group. R ₂₇ and R ₂₈ each independently represents a hydrogen atom or a substituent, and R ₂₇ and R ₂₈ may combine to form a ring, and R ₂₉ and R ₃₀ each independently represent a hydrogen atom. Or replace , And _the at least one of _{R 29} and _{R 30} represents an electron-withdrawing group.)