JP2009162801A - Phase difference film for vertical orientation type liquid crystal display device, its manufacturing method, polarizing plate using it, and vertical orientation type liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference film for a vertical orientation type liquid crystal display device having high transparency and capable of achieving excellent unevenness in color taste and front contrast of the vertical orientation type liquid crystal display device and to provide a polarizing plate using it and the vertical orientation type liquid crystal display device. <P>SOLUTION: This phase difference film for the vertical orientation type liquid crystal display device is constituted in such a way that an angle formed by the direction for forming the film and a lag axis within a film face is 40-50° and difference in light intensity between a case where the direction for mounting the film on a sample base agrees with the lag axis and a case where the direction for mounting the film on the sample base is set to the orthogonally crossing direction is 0.05 or less when measuring intensity of film scattered light of incident light 90° of scattered light profile of a goniophotometer by detecting intensity of scattered light at a position of 130° from a light source. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a retardation film for a vertical alignment type liquid crystal display device, a polarizing plate using the same, and a vertical alignment type liquid crystal display device.

  In recent years, the development and commercialization of technology for increasing the size and thickness of display devices have been actively promoted. Typical display devices include liquid crystal televisions, plasma televisions, organic EL televisions, etc. Among them, particularly rapid growth of liquid crystal televisions is remarkable, and in the future, both high image quality and cost reduction are strongly expected. Among them, a vertical alignment type liquid crystal display device (hereinafter also referred to as a VA mode type liquid crystal display device) is excellent in black tightening due to liquid crystal characteristics and widely used in large liquid crystal televisions.

  The above-mentioned liquid crystal television is characterized by high contrast in a bright place. In addition to the characteristics of the liquid crystal, it utilizes the technology of a backlight, a brightness enhancement film, a light guide plate and a diffusion plate. However, although these techniques are essential for improving the brightness, the cost of the members is high and disadvantageous for increasing the size. Therefore, the development of techniques for reducing the number of light sources and the brightness improving film is progressing.

  On the other hand, it has been known that the λ / 4 plate is effective as another brightness enhancement technique, and is used in many small and medium transmissive and transflective liquid crystal displays such as mobile phones and mobile displays. . However, in making a polarizing plate using a λ / 4 plate, conventionally, after forming a transparent resin film, it is stretched in the film forming direction or the width direction of the film and optically in the film plane. A method has been adopted in which the slow axis appears and the necessary area is cut out, and the slow axis and the transmission axis of the linearly polarizing plate are arranged at an angle of 45 ° and bonded to the linearly polarizing plate. . Therefore, it results from the problem that the productivity cannot be increased due to the loss at the time of cutting out the λ / 4 plate, the labor of the cutting operation itself, and the variation in the bonding axis adjustment between the individual λ / 4 plate and the linear polarizing plate. It has not been used for large LCD TVs because it has problems such as performance fluctuations.

There is a technical disclosure of an oblique stretching method for this problem (for example, see Patent Documents 1 to 3), and a retardation film having a slow axis existing obliquely is bonded to a linearly polarizing plate. By doing so, it became possible to make a circularly polarizing plate with much higher productivity. However, there are technical problems such as insufficient accuracy of the slow axis in the width direction, increased haze of the film, resulting in lower contrast in the dark, and variations in color. It is desired.
International Publication No. 2003/102639 Pamphlet JP 2005-284024 A JP 2007-30466 A

  Accordingly, an object of the present invention is to provide a retardation film for a vertical alignment type liquid crystal display device that has high transparency and is excellent in color unevenness and front contrast of the vertical alignment type liquid crystal display device, and a highly productive polarizing plate using the same. An object of the present invention is to provide a vertical alignment type liquid crystal display device having excellent display characteristics.

  The above object of the present invention is achieved by the following configurations.

  1. The angle between the film forming direction and the slow axis in the film plane is 40 to 50 °, and when the film scattered light intensity of 90 ° incident light of the scattered light profile of the goniophotometer is measured, 130 ° from the light source In the measurement for detecting the scattered light intensity at the position of the film, the difference in scattered light intensity between the case where the film is set on the sample stage and the direction perpendicular to the slow axis is 0.05 or less A retardation film for a vertical alignment type liquid crystal display device.

2. 2. The retardation film for a vertical alignment type liquid crystal display device according to 1 above, wherein the following formulas (1) to (3) are simultaneously satisfied.
(1) 130 ≦ Ro ≦ 160
(2) 150 ≦ Rt ≦ 230
(3) 0.78 ≦ Ro (480) / Ro (650) ≦ 0.96
Here, Ro = (nx−ny) × d (nm)
Rt = ((nx + ny) / 2−nz) × d (nm)
In the formula, the refractive index in the slow axis direction in the plane of the retardation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, and d is the retardation. Represents the thickness (nm) of the film. The measurement wavelength of the refractive index is 590 nm. Ro (480) and Ro (650) represent Ro when measured at wavelengths of 480 nm and 650 nm, respectively.

  3. 2. The vertical alignment type liquid crystal display device according to 1 above, wherein the retardation film for a vertical alignment type liquid crystal display device contains a cellulose ester, and the cellulose ester satisfies the following formulas (i) and (ii): Retardation film.

Formula (i) 2.1 ≦ X + Y ≦ 2.8
Formula (ii) 0.5 ≦ Y ≦ 1.6
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group.

  4). The retardation film for a vertical alignment type liquid crystal display device has an acrylic polymer and at least one of at least one of a pyranose structure or a furanose structure, and has all or a part of OH groups in the structure esterified. 2. The retardation film for a vertical alignment type liquid crystal display device as described in 1 above, wherein the retardation film is a cellulose ester film containing at least one ester compound.

  5). 5. A method for producing a retardation film for a vertical alignment type liquid crystal display device according to any one of 1 to 4, wherein a heated melt containing a cellulose ester is extruded into a film by a melt extrusion method, A method for producing a retardation film for a vertical alignment type liquid crystal display device, comprising a step of stretching in a slanting direction with respect to a longitudinal direction of the film or regulating shrinkage.

  6). 5. A polarizing plate comprising the retardation film for a vertically aligned liquid crystal display device according to any one of 1 to 4 on at least one surface.

  7. 7. A vertical alignment type liquid crystal display device comprising the polarizing plate according to 6 above on at least one surface of a liquid crystal cell.

  According to the present invention, a retardation film for a vertical alignment type liquid crystal display device which is highly transparent and has excellent color unevenness and front contrast of the vertical alignment type liquid crystal display device, and a highly productive polarizing plate and display using the same. A vertically aligned liquid crystal display device having excellent characteristics can be provided.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  In the retardation film for vertical alignment type liquid crystal display device of the present invention (hereinafter simply referred to as VA retardation film), the slow axis is present in the film plane, and the angle formed with the film forming direction is θ1. θ1 is 40 ° to 50 °, and preferably 42 ° to 48 °.

  In the VA retardation film of the present invention, the film forming direction coincides with the longitudinal direction.

When the retardation film for VA of the present invention is used as a circularly polarizing plate, it preferably has a retardation that simultaneously satisfies the following formulas (1) to (3).
(1) 130 ≦ Ro ≦ 160
(2) 150 ≦ Rt ≦ 230
(3) 0.78 ≦ Ro (480) / Ro (650) ≦ 0.96
Note that Ro = (nx−ny) × d (nm)
Rt = ((nx + ny) / 2−nz) × d (nm)
(In the formula, nx is the refractive index in the slow axis direction in the plane of the VA retardation film, ny is the refractive index in the direction perpendicular to the slow axis in the plane, nz is the refractive index in the thickness direction, d represents the thickness (nm) of the retardation film for VA, the refractive index measurement wavelength is 590 nm, and Ro (480) and Ro (650) represent Ro when measured at wavelengths of 480 nm and 650 nm, respectively. )
The refractive index can be obtained at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH (Oji Scientific Instruments).

<Scattered light measured by goniophotometer>
The retardation film for VA of the present invention is characterized in that the scattered light measured by a goniophotometer is in a certain range even when it is stretched to obtain the retardation.

  In order to improve the front contrast, it has been said that it is necessary to reduce the haze of the VA retardation film. It turns out that you can't.

  In contrast, the present inventors have found that it is necessary to eliminate anisotropic scattering. Anisotropic scattering refers to the difference in scattered light intensity between the slow axis direction of the film and the direction orthogonal thereto. This anisotropic scattering is measured with a goniophotometer.

<Anisotropic scattering measurement device>
FIG. 1 shows an outline of a goniophotometer (model: GP-1-3D, manufactured by Optec Corporation). G1. Light source lamp, G2. Spectrometer, G3. Sample stage (also called stage), G4. Sample (not shown), G5. It is a light receiving part.

  The light source uses a 12V50W halogen bulb, and the light receiving section uses a photomultiplier tube (Photomaru Hamamatsu Photonics R636-10).

  (A) shows the arrangement of a light source lamp, a spectroscope, a sample stage (stage), and an integrating sphere for measuring light intensity at the time of reference measurement for measuring reference light or transmittance measurement.

  (B) shows the arrangement of the light source lamp, the spectroscope, the sample stage, and the integrating sphere when the measurement sample is placed on the sample stage and the reflectance is measured.

  The sample stage is usually a measurement sample vertical hanging type, and the measurement sample is fixed with a clamp, and the lower part of the stage is an angle indexing rotary table. The transmittance is changed by changing the angle between the sample surface and the incident surface. It is a structure that can measure the reflectance.

  The anisotropic scattered light intensity according to the present invention can be measured by the arrangement (a). That is, the measurement of the scattered light intensity of a film having an incident light of 90 ° in the scattered light profile of the goniophotometer refers to the scattered light intensity when light is applied perpendicularly to the sample from the light source of the goniophotometer.

  When measuring the scattered light intensity at a position of 130 ° from the light source, the direction connecting the normal direction of the light source, the observation point of the sample, and the integrating sphere shown in FIG. This is the scattered light intensity measured when the angle θ formed by is 130 °.

  In the present invention, in the measurement of scattered light intensity at a position where θ is 130 °, the difference in scattered light intensity between the case where the film slow axis is horizontally installed on the sample stage and the case where the film is vertically installed is 0.05. It is characterized by the following.

  In order to satisfy the horizontal and vertical conditions, a normal level can be used.

  Various angles can be selected as θ, but in the present invention, it is set to 130 °, which has the highest correlation with the front contrast as the liquid crystal display device.

  When horizontal, the scattered light intensity when vertical is preferably in the range of 0.01 to 0.25, more preferably 0.20 or less, and even more preferably 0.10 or less.

  The difference in the scattered light intensity is 0.05 or less in the present invention, but the smaller the smaller the better.

  In order to achieve the scattered light intensity of the present invention, the retardation film for VA of the present invention includes at least one of the following cellulose ester, acrylic polymer, and pyranose structure or furanose structure. It is preferably a cellulose ester film containing at least one ester compound obtained by esterifying all or part of the OH group having the structure (hereinafter, the VA retardation film of the present invention may be referred to as a cellulose ester film). is there).

<Cellulose ester>
The cellulose ester used in the present invention is not particularly limited, but the cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an aromatic carboxylic acid ester, particularly a lower fatty acid ester having 6 or less carbon atoms. It is preferable that

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, the cellulose ester includes cellulose acetate propionate, cellulose acetate butyrate, or a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate butyrate. Can be used.

  The butyryl group forming butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

  In the present invention, the preferred cellulose ester for the purpose of adjusting retardation and reducing variation in retardation with respect to stretching preferably satisfies the following formulas (i) and (ii) simultaneously.

Formula (i) 2.1 ≦ X + Y ≦ 2.8
Formula (ii) 0.5 ≦ Y ≦ 1.6
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 1.6 and 1.0 ≦ Y ≦ 1.6, and preferably 2.1 ≦ X + Y ≦ 2.6. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
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 Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The cellulose used as a raw material of the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  Cellulose esters such as cellulose acetate propionate can be produced by known methods. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Acrylic polymer>
In the present invention, it is preferable to add an acrylic polymer to the cellulose ester film for the purpose of adjusting the retardation and reducing the variation in retardation with respect to stretching. Here, the acrylic polymer includes a methacrylic polymer.

  As an acrylic polymer used in the present invention, when it is contained in a cellulose ester film, it preferably exhibits negative birefringence as a function of the stretching direction, and the structure is not particularly limited. A polymer having a weight average molecular weight of 500 to 30,000 obtained by polymerizing an ethylenically unsaturated monomer is preferred.

(Test method for birefringence of acrylic polymer)
The acrylic polymer was dissolved in a solvent to form a cast film, and then dried by heating. The film having a transmittance of 80% or more was evaluated for birefringence.

  Refractive index measurement was performed using an Abbe refractometer-4T (manufactured by Atago Co., Ltd.) using a multiwavelength light source. The refractive index ny in the stretching direction and the refractive index in the in-plane direction perpendicular to each other were defined as nx. For films with (ny−nx) <0 for each refractive index at 550 nm, the acrylic polymer is judged to be negatively birefringent with respect to the stretch direction.

  The acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less used in the present invention may be an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain.

  As for the acrylic polymer having an aromatic ring in the side chain or the acrylic polymer having a cyclohexyl group in the side chain, if the weight average molecular weight is 500 or more and 10,000 or less, in addition to the above, cellulose after film formation The transparency of the ester film is excellent, the moisture permeability is extremely low, and it exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  In particular, the acrylic polymer used in the cellulose ester film according to the present invention includes an ethylenically unsaturated monomer Xa that does not have an aromatic ring and a hydroxyl group in the molecule, and does not have an aromatic ring in the molecule and has a hydroxyl group. Polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerizing ethylenically unsaturated monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, or having no aromatic ring The polymer Y is preferably a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya and an ethylenically unsaturated monomer copolymerizable with Ya.

[Polymer X, Polymer Y]
The method for adjusting Ro and Rt of the cellulose ester film according to the present invention includes ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule, and ethylene having a hydroxyl group and no aromatic ring in the molecule. High molecular weight polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of the polymerizable unsaturated monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, and more preferably, Contains a low molecular weight polymer Y having a weight average molecular weight of 500 to 3,000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring and an ethylenically unsaturated monomer copolymerizable with Ya It is preferable.

  The polymer X used in the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule and an ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group, Xa and Xb. Is a polymer having a weight average molecular weight of 2000 or more and 30000 or less obtained by copolymerization with a copolymerizable ethylenically unsaturated monomer other than.

  Preferably, Xa is an acrylic or methacrylic monomer having no aromatic ring and hydroxyl group in the molecule, and Xb is an acrylic or methacrylic monomer having no aromatic ring and having a hydroxyl group in the molecule.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
− [Xa] _m − [Xb] _n − [Xc] _p −
In the general formula (X), Xa represents an ethylenically unsaturated monomer having no aromatic ring and hydroxyl group in the molecule, and Xb represents an ethylenically unsaturated monomer having no aromatic ring and having a hydroxyl group in the molecule. Xc represents a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Furthermore, the polymer X is preferably a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R 1} ) (- CO 2 R 2)] m - [CH 2 -C (-R 3) (- CO 2 R 4 -OH) -] n - [Xc] p -
In the general formula (X-1), R ₁ and R ₃ each represent a hydrogen atom or a methyl group. R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R4 is _{-CH 2 -, - C 2 H} 4 - or -C ₃ H ₆ - represents a. Xc represents a monomer unit that can be polymerized to [CH ₂ —C (—R ₁ ) (— CO ₂ R ₂ )] or [CH ₂ —C (—R ₃ ) (— CO ₂ R ₄ —OH) —]. To express. m, n, and p represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

  In X, the hydroxyl group means not only a hydroxyl group but also a group having an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i-, s). -, T-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i -), Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), etc. The thing changed into acid ester can be mentioned.

  Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group, such as acrylic acid (2-hydroxyethyl), acrylic acid. (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing these acrylic acids with methacrylic acid. Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  Xc is not particularly limited as long as it is a monomer other than Xa and Xb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high.

  Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  The molecular weight of the high molecular weight polymer X is more preferably 5,000 or more and 30,000 or less, and still more preferably 8,000 or more and 25,000 or less.

  By setting the weight average molecular weight to 5000 or more, advantages such as little dimensional change under high temperature and high humidity of the cellulose ester film can be obtained.

  When the weight average molecular weight is 30000 or less, compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity and further haze generation immediately after film formation are suppressed.

  The weight average molecular weight of the polymer X used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  In addition, a weight average molecular weight etc. can be calculated | required according to the above-mentioned method.

  The low molecular weight polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferred because the residual monomer in the polymer is reduced.

  Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance. Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
− [Ya] _k − [Yb] _q −
In the general formula (Y), Ya represents an ethylenically unsaturated monomer having no aromatic ring, and Yb represents an ethylenically unsaturated monomer copolymerizable with Ya. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

  The polymer Y according to the present invention is more preferably a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R 5} ) (- CO 2 R 6)] k - [Yb] q -
In the general formula (Y-1), R ₅ represents a hydrogen atom or a methyl group, respectively. R ₆ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Yb represents a monomer unit copolymerizable with [CH ₂ —C (—R ₅ ) (— CO ₂ R ₆ )]. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with [CH ₂ —C (—R ₅ ) (— CO ₂ R ₆ )] which is Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing the ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate ( i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), acrylic Acid heptyl (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid ( 2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Used.

  In particular, the polymer Y is preferably a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility of Y and cellulose ester can be adjusted by this terminal residue.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

  The hydroxyl value is measured in accordance with JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated.

  Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C.

  After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid.

  Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point.

  Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
In the formula, B is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of a 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount 56.11 of potassium hydroxide.

  The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimension stability. Excellent in properties.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (a) and (b). When the content of the polymer X is Xg (mass% = (mass of polymer X / mass of cellulose ester) × 100) and the content of the polymer Y is Yg (mass%),
Formula (a) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (b) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of (Xg + Yg) in the formula (a) is 10 to 35% by mass. If the polymer X and the polymer Y are 5 mass% or more as a total amount with respect to the total mass of the cellulose ester, the polymer X and the polymer Y have a sufficient effect for adjusting the retardation value Rt.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope solution described later, or can be added to the dope solution after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<Ester compound in which at least one of pyranose structure or furanose structure is 1 or more and 12 or less and all or part of OH groups of the structure are esterified>
The retardation film for VA of the present invention has at least one pyranose structure or at least 12 furanose structures for the purpose of adjusting retardation and reducing variation in retardation with respect to stretching. It is preferable to include an ester compound obtained by esterifying all or part of the group.

  The proportion of esterification is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.

  In the present invention, ester compounds are collectively referred to as sugar ester compounds.

  Examples of sugar ester compounds include the following, but the present invention is not limited to these.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid is particularly preferable.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or furanose structure according to the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, and xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ (p is 0 to 5), and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and further, these alkyl groups, alkenyl groups, and phenyl groups. May have a substituent. Oligosaccharides can also be produced in the same manner as the ester compound used in the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

  The cellulose ester film according to the present invention preferably contains a sugar ester compound in an amount of 1 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. It is preferable to contain 5-30 mass%.

<Other additives>
(Plasticizer)
The retardation film for VA of the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (c).

Formula (c) R _1- (OH) _n
However, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as alkyl group, methoxy group or ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  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, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  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.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (d).

Formula (d) R ₂ (COOH) _m (OH) _n
(Where R ₂ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improving the retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The polyester plasticizer is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by the following general formula (c) can be used.

Formula (c) B- (GA) _n -GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (c), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer that can be used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-penta Diol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as a seed or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The polyester plasticizer used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Specific examples of the aromatic terminal ester plasticizer that can be used in the present invention are shown below, but the present invention is not limited thereto.

(UV absorber)
The cellulose ester film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products manufactured by Ciba Specialty Chemicals and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The VA retardation film according to the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method for adding the UV absorber is to add the UV absorber to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane, or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the VA retardation film is 30 to 200 μm, it is 0.5 to 10 with respect to the film. % By mass is preferable, and 0.6 to 4% by mass is more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film may be deteriorated.

  The antioxidant has a role of delaying or preventing the cellulose ester film from being decomposed by, for example, a residual solvent amount of halogen in the cellulose ester film or phosphoric acid of a phosphoric acid plasticizer. It is preferable to make it contain in a film.

  As the antioxidant or the heat deterioration preventing agent, commonly known ones can be used. In particular, phenol-based, lactone-based, sulfur-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  As the phenolic compound, those having a 2,6-dialkylphenol structure are preferable, for example, those commercially available under the trade names of Ciba Specialty Chemicals, Inc., “Irganox 1076” and “Irganox 1010” are preferable.

  As the lactone compound, those including those commercially available from Ciba Specialty Chemicals under the trade names of “IrgafosXP40” and “IrgafosXP60” are preferable.

  Phosphorus compounds are, for example, from Sumitomo Chemical Co., Ltd. “Sumilizer GP”, ADEKA Co., Ltd. “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Specialty Chemicals Co., Ltd. A commercially available product under the trade name “IRGAFOS P-EPQ” from the company and “GSY-P101” from API Corporation is preferable.

  As the hindered amine compound, for example, those commercially available from Ciba Specialty Chemicals Co., Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and ADEKA Corporation as “ADK STAB LA-52” are preferable.

  As the sulfur-based compound, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D” are preferable.

  Moreover, as a double bond type compound, what is marketed by Sumitomo Chemical Co., Ltd. by the brand name of "Sumilizer GM" and "Sumilizer GS" is preferable.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the cellulose ester film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a VA retardation film having a multi-layer structure formed by a co-casting method, it is preferable that this amount of fine particles is contained on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the VA retardation film low. In the VA retardation film according to the present invention, it is preferable that the dynamic friction coefficient of at least one surface is 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all 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 in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Method for producing retardation film for VA>
Next, the manufacturing method is demonstrated taking the cellulose ester film preferable for the retardation film for VA of this invention as an example.

  The cellulose ester film according to the present invention can be preferably used as a film produced by a solution casting method or a film produced by a melt casting method. In this case, it is preferable to use a melt casting method in which the influence of the residual solvent need not be considered.

  Manufacture of cellulose ester film according to the present invention includes a step of dissolving a cellulose ester and an additive in a solvent to prepare a dope, a step of casting and drying on an endless metal support that moves the dope indefinitely, a metal support It is performed by a step of peeling from the body, a stretching step, a step of further drying, and a step of winding up the finished film.

<Solution casting method>
(Dope adjustment process)
The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

  Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos.

  Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

(Casting, drying process)
The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling 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 contacting hot water 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 warm air is used, wind at a temperature higher than the target temperature may be used.

(Peeling process)
In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Especially preferably, it is 0-0.01 mass% or less. Peeling is preferably performed at a peeling tension of 300 N / m or less.

(Stretching process)
In order to obtain the target retardation values Ro and Rt in the present invention, it is preferable to further control the refractive index of the cellulose ester film having the preferred structure of the present invention by a stretching operation.

  In the present invention, the slow axis in the film plane forms an angle of 40 ° to 50 ° with respect to the film forming direction. For this purpose, a method of stretching by adjusting the angle is employed.

  As a method of adjusting the angle, it is preferable to stretch or regulate shrinkage in the film forming direction, and then stretch or regulate shrinkage in the inclined direction with respect to the film forming direction. For example, JP-A-2003-340916 A method using a stretching apparatus used in Example 1 of Japanese Patent Publication No. 2005-284024, a method using a stretching apparatus described in Production Example 2, a stretching method described in Japanese Patent Laid-Open No. 2007-30466, The method using the stretching apparatus used in Example 1 of JP-A-2007-94007 can be preferably used, and the film may be stretched online after casting, or may be stretched again after film formation. .

  Among them, it is particularly preferable to use the method described in JP-A-2005-30466.

Further, the following methods may be used in combination.
(1) Method of bending the left and right path by bending the conveyance (2) Method of setting the right and left clip speed difference by the spindle (3) Method of giving the right and left speed difference by giving independent left and right bending angles The embodiment will be described with reference to the drawings in the case of oblique stretching. However, the present invention is not limited to the following embodiments.

  2 and 3 show a plane and a cross section of a film stretching apparatus (stretching apparatus) 1 which is an embodiment of the present invention. The film stretching apparatus 1 includes a supply device 3 that supplies the film 2, a longitudinal stretching device 4 that heats the film, and a longitudinal stretching process (longitudinal stretching process) 6 that includes an intermediate transport device 5 that transports the film 2 downstream. An oblique stretching machine 7 that is inclined with respect to the transport direction while transporting the film 2 and that stretches in the direction, and an oblique stretching heating device that is provided so as to cover the central portion of the oblique stretching machine 7 and heats the film 2 8 includes an oblique stretching process (orthogonal expansion / contraction process) 9 and a winding device 10 for winding the film 2.

  The supply device 3 is mounted with an original reel 11 around which a film 2 is wound, and the film 2 is sandwiched between a reference roll 12 and a nip roll 13 and sent out at a predetermined transport speed. The longitudinal stretching device 4 is a box made of a heat insulating material having hot air ducts (heating means) 14 for spraying hot air alternately on the film 2 from above and below. The intermediate conveyance device 5 sandwiches and conveys the film 2 between the ratio roll 15 and the nip roll 16 and stretches it in the E1 direction parallel to the conveyance direction.

  The oblique stretching machine 7 stretches the film 2 in the E2 direction inclined by an angle α with respect to the transport direction while transporting the film 2 with the stretching chains 17 disposed on both sides of the film 2. Details will be described later. The oblique stretching furnace 8 is a box made of a heat insulating material having a hot air duct 18 for blowing hot air from above and below the film 2. The winding device 10 winds the film 2 around the product reel 20 while adjusting the tension with the tension roll 19.

  FIG. 4 shows the configuration of the oblique stretching machine 7. The oblique stretching machine 7 includes two parallel stretching chains 17, a plurality of bases 21 provided in the stretching chain 17 at regular intervals, and arms 22 attached to the respective bases 21 so as to be slidable in a certain direction. , And a clip 23 provided at the tip of each arm 22. The clip 23 can grip both side edges of the film 2, and the stretching chain 17 is looped around a sprocket 24 perpendicular to the surface of the film 2. Further, the clip 23 may move on the arm or change its angle appropriately with respect to the transport direction while holding the film 2.

  FIG. 5 shows a more detailed structure of the oblique stretching machine 7. A base 21 is fixed to the extending chain 17 every other frame. The base 21 is provided with two sliding shafts 25 each inclined by 45 ° (angle α in FIG. 2) with respect to the extending chain 17, and an arm 22 is attached to be slidable along each sliding shaft 25. ing. A positioning member 26 made of a bearing is provided on the upper portion of the arm 22, and the arm 22 is projected and retracted by guiding the positioning member 26 with a guide 27. The clip 23 provided at the tip of the arm 22 is a known film gripping mechanism, and is opened and closed by the guide 28 (the film 2 is gripped or released).

  The oblique stretching machine 7 causes the arm 22 to protrude from the base 21 of the stretching chain 17, grips both side edges of the film 2 with the clips 23, and transports the film 2 as the stretching chain 17 advances. During this time, the film 22 is retracted in the direction in which the arm 22 slides (direction E2 in FIG. 1) by widening the film 22 by retracting the arm 22 while holding the film 2 with the clip 23. At the time of widening, the retreat amounts of the arms 22 facing the sliding direction of the arms 22 are equal. After the film 2 is widened, the clip 23 may be released from the clip 23 through a certain holding process and relaxation process. In the case of stretching on-line after casting, the holding time in the holding process varies depending on the left and right, and there is a possibility that the retardation in the thickness direction may vary, and it is preferable that the shape of the hot air supply port be parallel to the inclined direction. Then, the arm 22 is further retracted so that the clip 23 does not contact the film 2 when the extending chain 17 is folded back along the sprocket 24.

  Then, the extending | stretching of the film 2 in the film extending apparatus 1 which consists of the above structure is demonstrated.

  In the longitudinal stretching section 6, when the film 2 is sent out at a predetermined speed by the reference roll 12 and is transported by the ratio roll 15 at a speed higher than that of the reference roll 12, a portion heated in the longitudinal stretching furnace 4 is transported. The film is stretched in the direction (E1 direction) at the same ratio as the ratio of the conveyance speed of the ratio roll 15 to the reference roll 12. By this stretching in the longitudinal direction, the molecules of the film 2 are arranged in the transport direction, and an orientation angle in the longitudinal direction is given.

  Further, in the oblique stretching section 9, the film 2 is stretched in the E2 direction in an inclined downward direction by an angle α with respect to the transport direction. By this stretching in the tilt direction, the film 2 is subjected to a tensile force in the E2 direction and a stress for deformation of the film 2, and a stretching force that attempts to align molecules at a larger angle with respect to the transport direction than in the E2 direction. Acts to provide an orientation angle in the tilt direction.

  As a result, the film 2 obtains an orientation angle in a direction obtained by adding the orientation angle imparted in the longitudinal stretching portion 6 and the orientation angle imparted in the oblique stretching portion 9, and the longitudinal stretching portion 6 and the oblique stretching are obtained. A retardation value is given in accordance with the strength of stretching (stretching ratio) in the portion 9.

  When the oriented film is produced by obliquely stretching the film 2 with the film stretching apparatus 1, the film 2 is actually stretched by the longitudinal stretching portion 6 and the oblique stretching portion 9, and the orientation angle of the obtained film 2 is measured. The stretching ratio in the longitudinal stretching section 6 is adjusted by increasing or decreasing the speed of the ratio roll 15 so that a desired orientation angle is obtained. Moreover, a desired retardation value is obtained by adjusting the stretch ratio in the oblique stretched portion 9.

  The draw ratio in the biaxial direction is preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively, and 0 in the casting direction. It is preferable to carry out in the range of 0.8 to 1.0 times and 1.2 to 2.0 times in the width direction.

  The stretching temperature is preferably 150 ° C. to 210 ° C., more preferably 160 ° C. to 200 ° C., and more preferably 170 ° C. to 200 ° C. or less.

  The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%.

  Specifically, it is preferable that the residual solvent is stretched at 11% at 175 ° C, or the residual solvent is stretched at 2% at 175 ° C. Alternatively, it is preferable that the residual solvent is stretched at 11% at 185 ° C, or the residual solvent is stretched at less than 1% at 185 ° C.

(Drying process)
In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  The means for drying is not particularly limited and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but is preferably performed with hot air from the viewpoint of simplicity.

  The drying temperature in the drying step is preferably increased stepwise from 40 to 200 ° C.

  Although the film thickness of a cellulose-ester film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  The cellulose ester film according to the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

<Melt casting method>
FIG. 6 is an example of a manufacturing apparatus used in the melt casting method. However, the present invention is not limited to this.

  Extruder 101, filter 102, static mixer 103, die (including thickness adjusting means) 104, touch roll 105, first cooling roll 106, second cooling roll 107, peeling roll 108, dancer roll 109, stretching machine 110, slitter 111, a thickness measuring means 112, an embossing ring and back roll 113, a winder 114, and a wound film 115.

  The cellulose ester used in the present invention is usually obtained in powder form. In the method for producing a cellulose ester film according to the present invention, powdery cellulose ester may be used, but it is preferable from the viewpoint of handling that the powder is formed into a pellet.

  When the powder is formed into a pellet, a known single-screw extruder or twin-screw extruder can be used. For example, after putting powdery cellulose ester from the hopper of an extruder, melt kneading the cellulose ester at a temperature of about (Tg + 100) ° C., extruding a strand from the die, and cooling the strand by a method such as water cooling The pellet can be obtained by cutting with a pelletizer.

  Add various antioxidants such as phenolic antioxidants and phosphorus antioxidants, lubricants such as higher fatty acid amides and higher fatty acid residual metal salts, etc. as necessary when adding powdered cellulose ester to the hopper And may be pelletized.

  The powder is preferably dried at a temperature near Tg in advance. Further, when forming into a pellet form, it is preferable to use a vented extruder while sucking the inside of the extruder.

  Pellets made of cellulose ester are preferably used after sufficiently drying at a temperature near Tg. In order to prevent the polymer from being oxidized and deteriorated during drying, drying under nitrogen is desirable.

  The cellulose ester is melt-kneaded in a single-screw or twin-screw extruder and extruded into a sheet form from a casting die. Usually, the temperature of the extruder is set so that the resin temperature is in the range of (Tg + 100) ° C. to (Tg + 200) ° C.

  In addition, the extruder hopper is sealed with nitrogen to suppress degradation of cellulose ester in the extruder, a leaf disk filter is used to suppress the generation of foreign objects such as fish eyes, and extrusion fluctuations are suppressed. For this purpose, a gear pump may be used.

  It is preferable to use a casting die having a shape in which the tip portion is processed into a sharp edge (curvature radius R = 0.1 μm or less) from the viewpoint of suppressing occurrence of a crack.

  A melted cellulose ester extruded from a casting die into a sheet is made of a cooling casting roll that is a rotating support, and a metal that is a pressing rotary body provided in pressure contact with the casting roll along its circumferential direction. A nip is formed by the elastic touch roll or endless belt, and a sheet-like molten cellulose ester is passed through the nip portion, so that the desired surface shape is sandwiched between the casting roll and the elastic touch roll or endless belt. A cellulose ester film having a thickness and optical performance is formed.

  Examples of the elastic touch roll include Japanese Patent Laid-Open No. 03-124425, Japanese Patent Laid-Open No. 08-224772, Japanese Patent Laid-Open No. 07-1000096, Japanese Patent Laid-Open No. 10-272676, WO 97-028950, Japanese Patent Laid-Open No. 11-235747, and Japanese Patent Laid-Open No. 2002-36332. No. 2005-172940 and JP-A 2005-280217 can use a thin rubber sleeve-coated silicon rubber roll, but a touch roll having elasticity is preferable.

  The endless belt is a flexible metal sleeve belt that is held by a plurality of rolls arranged in parallel with the casting roll in the circumferential direction of the casting roll, and preferably has a thickness of 100 to 1500 μm. .

  If the endless belt is too thin, the strength of the belt is weak, and the belt may be deformed when the molten cellulose ester is sandwiched. If the endless belt is too thick, the pressure for sandwiching the molten cellulose ester becomes too strong, and a bank may be formed.

  The endless belt is preferably held by two or more rolls having a diameter of 100 to 300 mm. By holding the endless belt with the roll as described above, the molten cellulose ester can be pinched with a stable pressure.

  The surface temperature of the endless belt is preferably 50 ° C. or more and (Tg−5) ° C. or less from the viewpoint of peeling failure.

  In the manufacturing apparatus used in the present invention, the length (air gap) until the molten cellulose ester extruded from the lip of the casting die comes into contact with the elastic touch roll endless belt or the casting roll is 30 to 300 mm. Preferably, it is 70-200 mm.

  By producing under such conditions, an optically uniform film can be obtained. The air gap is the shortest length from the lip of the casting die until the molten cellulose ester contacts either the endless belt or the casting roll.

  For example, when the molten cellulose ester comes into contact with the endless belt first, it is the shortest length from the casting die lip to the point where the endless belt and the molten cellulose ester start to contact.

  The air gap when the molten cellulose ester comes into contact with the casting roll is also determined in the same manner. The value of the air gap can be determined by the size of the endless belt and the casting roll, the shape of the casting die tip, and the positional relationship between the casting roll, the endless belt and the casting die.

  In order to make the air gap 150 mm or less, it is preferable to use a 200 to 400 mmφ casting roll. The surface of the casting roll is preferably a mirror finish with high smoothness.

  The lower limit value of the surface temperature of the casting roll is preferably equal to or higher than the surface temperature of the elastic touch roll or the endless belt from the viewpoint of suppressing generation of wavy wrinkles and peeling, and the upper limit value is It is preferable that it is (Tg-5) degrees C or less.

  The distance for sandwiching the molten cellulose ester between the casting roll and the elastic touch roll or the endless belt is 50 to 150 mm, preferably 70 to 130 mm, from the viewpoint of the effect of improving the appearance defect such as die line. .

  The cellulose ester film sandwiched between an elastic touch roll or an endless belt and a casting roll and solidified by cooling is preferably further stretched by 1.01 to 5.0 times in at least one direction. The sharpness of the streaks becomes gentle by stretching and can be highly corrected.

  The stretching apparatus is preferably the same as that used in the solution casting method described above.

  Thereafter, the film is taken up by a take-up machine, and after the film is slit and removed, the film is taken up in a roll by a take-up machine.

  A protective film can also be bonded using a nip roll of a take-up machine. As the protective film, a film made of a commercially available ethylene-vinyl acetate copolymer or the like can be used, and can be bonded to one side or both sides of a cellulose ester film.

  The film made of cellulose ester obtained in the present invention may be a multilayer film. In the case of a multilayer film, it is only necessary to have one or more layers made of cellulose ester.

  When using the film obtained by this invention for an optical product, it is preferable that all the layers are multilayer films which consist of a cellulose ester. When a multilayer film is produced according to the present invention, a multi-manifold type casting die or a feed block type casting die can be used. Since it is easy to accurately control the thickness of each layer, it is preferable to use a multi-manifold casting die.

<Physical properties of cellulose ester film>
The moisture permeability of the cellulose ester film according to the present invention, 40 ° C., preferably 10~1200g / m ² · 24h at 90% RH, preferably more ^{20~1000g / m 2 · 24h, 20~850g} / m 2 · 24h Is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The cellulose ester film according to the present invention preferably has a breaking elongation of 10 to 80%, more preferably 20 to 50%.

  The visible light transmittance of the cellulose ester film according to the present invention is preferably 90% or more, and more preferably 93% or more.

  In addition, by further applying a liquid crystal layer to the cellulose ester film according to the present invention, retardation values over a wider range can be obtained.

(Configuration of polarizing plate)
The polarizing plate which used the cellulose-ester film which concerns on this invention as a polarizing plate protective film, and the liquid crystal display device of this invention using the same are demonstrated.

  The polarizing plate of the present invention is preferably a polarizing plate bonded to at least one surface of a polarizer using the VA retardation film of the present invention as a polarizing plate protective film. In the liquid crystal display device of the present invention, it is preferable that the polarizing plate according to the present invention is bonded to at least one liquid crystal cell surface via an adhesive layer.

<Linear polarizing film>
The linear polarizing film is not limited as long as it is an absorption linear polarizing film, and various known forms can be applied. Generally, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as polyvinyl chloride is treated to produce polyene. In addition to a polarizing film made of an oriented film or the like, a film in which the polarizing film is covered with a sealing film and protected is used.

<Configuration of circularly polarizing film>
The cross-sectional structure of the circularly-polarizing film which concerns on this invention is shown with a figure. 7 to 9 are schematic views of the embodiment of the present invention, but the present invention is not limited to this.

  FIG. 7 shows a circle obtained by bonding one side of a VA retardation film of the present invention to a normal polarizing plate (having a structure of TAC (cellulose triacetate) / polarizer / TAC) using an adhesive or an adhesive. It is a polarizing plate. In this case, a commercially available polarizing plate can be used as it is.

  FIG. 8 shows a VA retardation film (λ / 4) of the present invention, a conventional retardation film (λ / 2) formed only by oblique stretching, and a normal linear polarizing plate. It is the circularly-polarizing plate bonded by the axial angle which exists in.

  FIG. 9 shows a circularly polarizing plate in which the VA retardation film of the present invention is used as a polarizing plate protective film on one side, and is laminated and bonded together with another polarizing plate protective film so as to sandwich a linear polarizer film.

  Another polarizing plate protective film is bonded to the other surface. For example, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4UE, KC8UE, KC8UY-HA, KC8UY-HA, KC8UY-C8 -RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) and acrylic resin films are preferably used.

  In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.

<Liquid crystal display device>
By using the polarizing plate bonded with the retardation film for VA of the present invention for a VA (MVA, PVA) mode liquid crystal display device, the VA mode liquid crystal display device of the present invention having excellent visibility can be produced. it can.

  FIG. 10 shows an example of a VA mode liquid crystal display device of the present invention. The retardation film for VA of the present invention is bonded by tilting the slow axis in the film plane at 45 ° with respect to the absorption axis of the linear polarizer to form a circularly polarizing plate. The slow axes are arranged so as to be orthogonal to each other.

  In this manner, a liquid crystal display device having a high front contrast and a high front contrast can be obtained even when the screen is a large-screen liquid crystal display device having a screen size of 30 or more.

  Hereinafter, although an example is given and the present invention is explained, the present invention is not limited to these.

(Production of retardation film 1 for VA)
<Fine particle dispersion>
Fine particles 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
The following cellulose acetate propionate was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi Filter Paper No. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

Methylene chloride 99 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.65, propionyl group substitution degree 0.8, number average molecular weight 80000, weight average molecular weight 220,000) 4 parts by weight Fine particle dispersion 11 parts by weight A dope solution was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The following cellulose acetate propionate was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

  In addition to adding 100 parts by mass of the main dope solution and 2 parts by mass of the fine particle additive solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting apparatus to adjust the width. It was cast uniformly on a 2 m stainless steel band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. Then, using the apparatus described in Example 1 of JP-A-2007-94007 (stretching machine A: FIG. 11), the slow axis forms 45 ° with the film width direction at a temperature of 170 ° C. and a magnification of 1.5 times. In this manner, the film was stretched in an oblique direction and dried to obtain a long VA retardation film 1.

<Composition of main dope solution>
Methylene chloride 300 parts by mass Ethanol 57 parts by mass Cellulose acetate propionate (acetyl group substitution degree 0.8, propionyl group substitution degree 1.65, number average molecular weight 80000, weight average molecular weight 220,000) 100 parts by mass Acrylic polymer C 5 Mass parts Sugar ester compound exemplified compound 3 10 parts by mass Plasticizer (a), (b), (c) 1: 1: 1 mass ratio 0.5 parts by mass Trimethylolpropane tris (3,4,5-trimethoxy Benzoate)
1 part by mass

  The acrylic polymer was bulk polymerized by the polymerization method described in JP-A No. 2000-128911.

(Preparation of retardation film 2 for VA)
From the retardation film 1 for VA, the stretching apparatus is changed to the apparatus described in JP-A-2003-340916, Example-1 (stretching machine B: Fig. 12), and the slow axis is set at a temperature of 170 ° C and a magnification of 1.5 times Was stretched in an oblique direction so as to form 45 ° with the film width direction to produce a long VA retardation film 2.

(Preparation of VA retardation film 3)
Change from the retardation film 1 for VA to the stretching apparatus (stretching machine C) shown in FIGS. 2 to 5 so that the slow axis forms 45 ° with the film width direction at a temperature of 170 ° C. and a magnification of 1.5 times. Stretched in an oblique direction to produce a long VA retardation film 3.

(Preparation of retardation film 4 for VA)
For the VA retardation film 3, except that the stretching machine C was used, the acrylic polymer was removed, and trimethylolpropane tris (3,4,5-trimethoxybenzoate) was changed to 5.5 parts by mass. Similarly, a long VA retardation film 4 was produced.

(Preparation of retardation film 5 for VA)
Except for the acrylic polymer and the sugar ester compound, the total amount of plasticizers (a), (b), and (c) was changed to 5.5 parts by mass with respect to the retardation film 3 for VA. A long VA retardation film 5 was produced.

(Preparation of retardation film 6 for VA)
A long VA retardation film 6 was prepared in the same manner as in the VA retardation film 3 except that the stretching machine C was used and the acrylic polymer was changed as shown in Table 2.

(Preparation of retardation film 7 for VA)
(Pellet preparation)
Cellulose acetate propionate (acetyl group substitution degree 1.23, propionyl group substitution degree 1.31, number average molecular weight 75000) 100 parts by mass Acrylic polymer C 5.5 parts by mass Sugar ester compound exemplified compound 3 5.5 parts by mass Part trimethylolpropane tris (3,4,5-trimethoxybenzoate)
1 part by weight IRGANOX-1010 (manufactured by Ciba Specialty Chemicals) 1 part by weight Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) 0.5 parts by weight To the above materials, 0.05 part by weight of silica particles is added, and nitrogen gas is enclosed V After mixing with a mold mixer for 30 minutes, it is melted at 240 ° C. using a twin screw extruder (PCM30, Ikegai Co., Ltd.) equipped with a strand die to produce a cylindrical pellet having a length of 4 mm and a diameter of 3 mm. did. At this time, the shear rate was set to 25 (mm / s). The obtained pellets were dried at 100 ° C. for 5 hours to have a water content of 100 ppm and fed to a single screw extruder (GT-50; manufactured by Plastic Engineering Laboratory Co., Ltd.) equipped with a 300 mm wide T die. And T-die was set to 250 degreeC and it formed into a film. The surface of the T die was subjected to hard chrome plating and finished with a mirror finish with a surface roughness of 0.1S. The film from the T-die was dropped onto a first cooling roll with a chrome-plated mirror surface adjusted to 110 ° C.

  The film in close contact with the first cooling roll was pressed with an elastic touch roll after being transported around the circumference of the first cooling roll by a central angle of 10 °. At this time, it contacted with the pressure of 4 N / mm with respect to the whole width 250mm of a film. After the pressed film is brought into contact with the circumferential portion of the first cooling roll having a central angle of 150 °, a total of three cooling films, ie, a second cooling roll (temperature 110 ° C.) and a third cooling roll (temperature 80 ° C.) are cooled. The film was sequentially circumscribed on the roll, cooled and solidified to form a film, and peeled off by a peeling roll. Thereafter, using the apparatus (stretching machine A) described in Example 1 of Japanese Patent Application Laid-Open No. 2007-94007, the temperature is 170 ° C., the magnification is 2 times, and the slow axis is inclined at 45 ° to the film width direction. The film was stretched and dried to produce a long VA retardation film 7.

(Production of retardation films 8 to 17 for VA)
Furthermore, as shown in Table 2, for the VA, except that the stretching machine (stretching machine B, stretching machine C), stretching angle, stretching temperature, stretching ratio, cellulose ester substitution degree, acrylic polymer, sugar ester compound were changed. In the same manner as the retardation film 7, long VA retardation films 8 to 17 were produced.

(Preparation of retardation film 18 for VA)
Except for the acrylic polymer from the retardation film 7 for VA, except that trimethylolpropane tris (3,4,5-trimethoxybenzoate) was changed to 5.5 parts by mass addition, a long VA A retardation film 18 was prepared.

(Preparation of VA retardation film 19)
Except for the acrylic polymer and the sugar ester compound exemplary compound 3 from the retardation film 7 for VA, except that trimethylolpropane tris (3,4,5-trimethoxybenzoate) was changed to 10 parts by mass addition, In the same manner, a long VA retardation film 19 was produced.

<Evaluation>
The following evaluation was performed using the produced retardation film for VA.

(Difference in scattered light intensity)
Goniophotometer model: GP-1-3D, manufactured by Optec Corporation (light source: 12V50W halogen bulb, light receiving part: photomultiplier tube (Photomaru Hamamatsu Photonics R636-10)).

  The amount of light at the time of measurement was corrected with the amount of light at θ = 180 ° (photomal light receiving sensitivity: −185 V), and the measured value at this amount of light was taken as the scattered light intensity.

  The sample was measured by fixing the slow axis of the film horizontally and vertically on the sample stage, and the difference in scattered light intensity was determined.

(Measurement of retardation Ro and Rt)
A 35 mm × 35 mm sample was cut out from the obtained film, conditioned at 25 ° C. and 55% RH for 2 hours, and measured with an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.) from the vertical direction at 590 nm and the film. It calculated from the extrapolation value of the retardation value measured similarly, inclining a surface.

(Haze)
Measurement was performed according to JIS K-6714 using a haze meter 1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.

  Tables 2 and 3 show the configuration and evaluation results of the retardation film for VA.

  It can be seen that the sample of the present invention has a desired retardation value by oblique stretching and a low haze.

  Next, a polarizing plate and a liquid crystal display device were produced using the produced VA retardation film.

(Preparation of polarizing plate)
A 120 μm-thick polyvinyl alcohol long film was uniaxially stretched in the MD direction (temperature: 110 ° C., stretch ratio: 5 times). This 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, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film (polarizer).

  Next, according to the following steps 1 to 5, a polarizer, a VA retardation film 1 to 19, and a long Konica Minolta Tack KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) on the back side across the polarizer are polarizing plate protective films As a result, a laminated polarizing plate was prepared. In that case, it bonded so that the longitudinal direction of each of a polarizer, retardation film for VA, and KC4UY might be aligned.

  Step 1: A VA retardation film 1-19 and a cellulose ester film, which are immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to a polarizer. KC4UY was obtained.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was lightly wiped off and placed on the VA retardation film and cellulose ester film treated in Step 1.

Step 4: The VA retardation film, the polarizer and the back side cellulose ester film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveying speed of about 2 m / min.

  Process 5: The sample which bonded together the polarizer produced in process 4 in the dryer of 80 degreeC, the phase difference film for VA, and the back side cellulose-ester film was dried for 2 minutes, and the polarizing plates 1-19 were produced.

(Production of liquid crystal display device)
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the SONY 40-type display KLV-40J3000, which is a vertical alignment type liquid crystal display device, were peeled off in advance, and the prepared polarizing plates 1 to 19 were pasted on both sides of the glass surface of the liquid crystal cell, respectively. Combined.

  At this time, the polarizing plate is bonded so that the surface of the VA retardation film of the present invention is on the liquid crystal cell side and the absorption axis of the polarizer is orthogonal to the liquid crystal display device. 1 to 19 were produced.

  The liquid crystal display device was evaluated for color variation and front contrast. The results are shown in Table 4.

<Evaluation>
(Evaluation of color variation)
About each produced said liquid crystal display device, the color fluctuation was measured using the measuring machine (EZ-Contrast160D, ELDIM company make). In the CIE 1976 and UCS coordinates, the maximum hue variation width Δu′v ′ in the vertical direction (80 ° to 80 ° below the display normal) was compared.

(Evaluation of front contrast)
The measurement was performed after the backlight of each liquid crystal display device was lit continuously for one week in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast.

  Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)

  From the results of Table 4, it is clear that the liquid crystal display devices 1 to 3, 6 to 8 and 10 to 16 using the VA retardation film of the present invention are liquid crystal display devices excellent in hue variation and front contrast. is there.

It is the schematic of a goniophotometer. It is one schematic of the extending | stretching apparatus of this invention. It is one schematic of the extending | stretching apparatus of this invention. It is one schematic of the extending | stretching apparatus of this invention. It is one schematic of the extending | stretching apparatus of this invention. It is the schematic of the melt casting film forming apparatus of this invention. It is one of the embodiments of the circularly polarizing plate of the present invention. It is one of the embodiments of the circularly polarizing plate of the present invention. It is one of the embodiments of the circularly polarizing plate of the present invention. It is an example of the liquid crystal display device of this invention. It is the schematic of the extending | stretching apparatus (stretching apparatus A) used for the Example. It is the schematic of the extending | stretching apparatus (stretching apparatus B) used for the Example.

Explanation of symbols

G1 Light source lamp G2 Spectrometer G3 Sample stage (stage)
G5 light-receiving portion G6 Sample pressing spring G7 Angle indexing rotary table θ Angle formed by the normal direction of the light source and the direction connecting the observation point of the sample and the integrating sphere 1 Stretching device 2 Film 3 Film supply device 4 Longitudinal stretching device 5 Intermediate Conveying device 6 Longitudinal stretching step 7 Oblique stretching device 8 Oblique stretching heating device 9 Oblique stretching step 10 Winding device 11 Raw material reel 12 Reference roll 13 Nip roll 14 Hot air duct 15 Ratio roll 16 Nip roll 17 Stretch chain 18 Hot air duct 19 Tension roll 20 Winding device E1 Direction parallel to transport direction (film forming direction) E2 Direction inclined by angle α with respect to transport direction (film forming direction) 21 Base 22 Arm 23 Clip 24 Sprocket 25 Slide shaft 26 Positioning member 27 Guide 28 Guide 101 Extruder 10 Filter 103 static mixer 104 die (including thickness adjusting means)
DESCRIPTION OF SYMBOLS 105 Touch roll 106 1st cooling roll 107 2nd cooling roll 108 Peeling roll 109 Dancer roll 110 Stretching machine 111 Slitter 112 Thickness measuring means 113 Embossing ring and back roll 114 Winding machine 115 Rolled film 201 Film 210 Constant temperature chamber 211 Rail 212 Grasping means 213 Boundary between preheating zone and stretching zone 214 Boundary between stretching zone and fixed zone 221 Pulling roll 222 Winding roll 301 Film 302 Preheating zone 303 Heating stretching zone 304 Cooling zone 305 Stretched films 306, 307 Screw 308, 381 Clip 309, 391 Belt

Claims (7)

The angle between the film forming direction and the slow axis in the film plane is 40 to 50 °, and when the film scattered light intensity of 90 ° incident light of the scattered light profile of the goniophotometer is measured, 130 ° from the light source In the measurement for detecting the scattered light intensity at the position of the film, the difference in scattered light intensity between the case where the film is set on the sample stage and the direction perpendicular to the slow axis is 0.05 or less A retardation film for a vertical alignment type liquid crystal display device. The retardation film for a vertical alignment type liquid crystal display device according to claim 1, wherein the following expressions (1) to (3) are simultaneously satisfied.
(1) 130 ≦ Ro ≦ 160
(2) 150 ≦ Rt ≦ 230
(3) 0.78 ≦ Ro (480) / Ro (650) ≦ 0.96
Here, Ro = (nx−ny) × d (nm)
Rt = ((nx + ny) / 2−nz) × d (nm)
In the formula, the refractive index in the slow axis direction in the plane of the retardation film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction is nz, and d is the retardation. Represents the thickness (nm) of the film. The measurement wavelength of the refractive index is 590 nm. Ro (480) and Ro (650) represent Ro when measured at wavelengths of 480 nm and 650 nm, respectively. The vertical alignment type liquid crystal display according to claim 1, wherein the retardation film for a vertical alignment type liquid crystal display device contains a cellulose ester, and the cellulose ester satisfies the following formulas (i) and (ii). Retardation film for equipment.
Formula (i) 2.1 ≦ X + Y ≦ 2.8
Formula (ii) 0.5 ≦ Y ≦ 1.6
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group. The retardation film for a vertical alignment type liquid crystal display device has an acrylic polymer and at least one of at least one of a pyranose structure or a furanose structure, and has all or a part of OH groups in the structure esterified. The retardation film for a vertical alignment liquid crystal display device according to claim 1, wherein the retardation film is a cellulose ester film containing at least one ester compound. It is a manufacturing method of the phase difference film for perpendicular alignment type liquid crystal display devices given in any 1 paragraph of Claims 1-4, Comprising: After extruding the heating melt containing a cellulose ester in the shape of a film by the melt extrusion method, A method for producing a retardation film for a vertical alignment type liquid crystal display device, comprising a step of stretching in a slanting direction with respect to the longitudinal direction of the film or regulating shrinkage. A polarizing plate comprising the retardation film for a vertical alignment type liquid crystal display device according to any one of claims 1 to 4 on at least one surface. A vertically aligned liquid crystal display device comprising the polarizing plate according to claim 6 on at least one surface of a liquid crystal cell.

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