JP2007268898A - Optical film manufacturing method, optical film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

［σ：高分子溶液の表面張力（ｄｙｎｅ／ｃｍ²）の温度（℃）に対する変化率、ｈ：流延時の高分子溶液の厚味（μｍ）、β^s：流延直前の高分子溶液の温度（℃）、β^a：流延時の環境と基板のうち、β^sとの温度差が大きい方の温度（℃）、ν：流延時の高分子溶液の粘度（Ｐａｓ）である。］
【選択図】 なし
The present invention provides a method for producing an optical film with little variation in optical performance.
A polymer solution in which a polymer compound is dissolved in a solvent is cast on a substrate, the solvent is volatilized and then peeled off from the substrate, and a value N represented by formula 1 is 20 to 19000. The manufacturing method of an optical film including making it become.
Formula 1

[Σ: Rate of change of surface tension (dyne / cm ² ) of polymer solution with respect to temperature (° C.), h: Thickness (μm) of polymer solution at casting, β ^s : Polymer solution just before casting Temperature (° C.), β ^a : Temperature (° C.) having a larger temperature difference from β ^s among the environment and substrate during casting, and ν: Viscosity (Pas) of the polymer solution during casting. ]
[Selection figure] None

Description

  The present invention relates to a method for producing an optical film, and an optical film, a polarizing plate, and a liquid crystal display device obtained thereby.

Liquid crystal display devices are widely used for personal computer and portable device monitors and television applications due to various advantages such as low voltage, low power consumption, and being capable of being reduced in size and thickness. In such a liquid crystal display device, various modes have been proposed depending on the alignment state of the liquid crystal in the liquid crystal cell. Conventionally, the liquid crystal display device is in an alignment state twisted by about 90 ° from the lower substrate to the upper substrate of the liquid crystal cell. The TN mode was mainstream.
In general, a liquid crystal display device includes a liquid crystal cell, an optical compensation sheet, and a polarizer. The optical compensation sheet is used for eliminating image coloring or expanding the viewing angle, and a stretched birefringent film or a film obtained by applying a liquid crystal compound to a transparent film is used. For example, Japanese Patent No. 2587398 discloses a technique for applying a discotic liquid crystal compound on a triacetylcellulose film, aligning it, and applying the fixed optical compensation sheet to a TN mode liquid crystal cell to widen the viewing angle. Yes. However, a liquid crystal display device for television that is expected to be viewed from various angles on a large screen has a strict requirement for viewing angle dependency, and even with the above-described method, the requirement cannot be satisfied. Therefore, liquid crystal display devices different from the TN mode, such as an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode, and a VA (Vertically Aligned) mode, have been studied. In particular, the VA mode is attracting attention as a liquid crystal display device for TV because of its high contrast and relatively high production yield.

On the other hand, the cellulose acylate film is characterized by high optical isotropy (low retardation value) as compared with other polymer films. Therefore, it is common to use a cellulose acetate film for an application requiring optical isotropy, for example, a polarizing plate. Patent Document 1 discloses a method for producing a cellulose acetate film having few insolubles and high transparency by defining the relationship between the viscosity average degree of polymerization of cellulose acetate and the viscosity of a dope obtained by dissolving the cellulose acetate in a solvent. Further, in Patent Document 2, in order to eliminate a planar failure called die stripe, the thickness d of the cellulose acetate film, the solid content concentration y (%) of the polymer solution used for forming the cellulose acetate film, and the polymer A preferred relationship of solution viscosity ρ is disclosed.
On the other hand, the optical compensation sheet (retardation film) of the liquid crystal display device is required to have optical anisotropy (high retardation value). In particular, an optical compensation sheet for VA requires in-plane retardation (Re) of 30 to 200 nm and thickness direction retardation (Rth) of 70 to 400 nm. Therefore, it is common to use a synthetic polymer film having a high retardation value such as a polycarbonate film or a polysulfone film as the optical compensation sheet.
As described above, in the technical field of optical materials, when a polymer film requires optical anisotropy (high retardation value), a synthetic polymer film is used and optical isotropy (low retardation value) is used. It was a general principle to use cellulose acetate film when required.

Patent Document 3 discloses a cellulose acetate film having a high retardation value that can be used for applications requiring optical anisotropy, overcoming the conventional general principle. In this document, in order to achieve a high retardation value with cellulose triacetate, an aromatic compound having at least two aromatic rings, particularly a compound having a 1,3,5-triazine ring, is added and subjected to stretching treatment.
Cellulose triacetate is generally a polymer material that is difficult to stretch, and it is known that it is difficult to increase the birefringence, but it is necessary to increase the birefringence by simultaneously orienting the additives in the stretching process. To achieve a high retardation value. Since this film can also serve as a protective film for the polarizing plate, there is an advantage that an inexpensive and thin liquid crystal display device can be provided.

  The method described in the above patent document is effective in that an inexpensive and thin liquid crystal display device can be obtained. However, in recent years, a higher retardation value is required, and it is necessary to increase the amount of addition of the retardation developer or increase the draw ratio. Streaky irregularities extending in the casting direction due to thickness variation in the width direction, which are called vertical stripes, become apparent, and bright spot foreign matter and luminance and color irregularities that become apparent only when assembled in a liquid crystal display device are problems. I came. In particular, an optical film used for a large-sized liquid crystal television has a maximum optical axis shift of −1 ° to + 1 ° depending on the position in the width direction and the length direction. Further, when the cellulose acylate film is assembled on a polarizing plate or when two polarizing plates are bonded to a liquid crystal cell, the optical axis is likely to be displaced by about 1 degree at maximum. When the deviation between the optical axis of the polarizer and the optical axis of the optical film or the deviation of the optical axis between the two polarizing plates becomes large, light leakage in black display becomes significant. The greater the deviation of the optical axis, the more uneven the brightness when viewed on a large screen even when the optical axis fluctuates at narrow intervals in the width direction of the optical film, even if the absolute value is small. Becomes visible. There has been a demand for a solution to such surface unevenness. Also, the larger the screen, the less the generation of bright spot foreign matter, the lower the yield of polarizing plates and liquid crystal display devices and the higher the production cost. Therefore, improvement in this aspect has also been demanded.

JP 2000-131524 A JP 2001-129838 A European Patent Application No. 91656

  An object of the present invention is to solve the above-described problems, and an object of the present invention is to provide a method for producing an optical film with little variation in optical performance.

The inventor of the present invention has made extensive studies to solve the above problems, and as a result, it has been clarified that unevenness can be particularly reduced by adding a leveling agent described later and increasing the viscosity of a polymer solution to be cast.
However, further studies have revealed that it becomes difficult to reduce unevenness as the difference between the temperature of the polymer solution to be cast and the ambient temperature (environmental temperature) increases.
In addition, it has also been clarified that undesirable unevenness increases as the thickness of the casting liquid film increases.
In other words, it has been found that the preferred ranges of the thickness, temperature difference, surface tension and viscosity of the polymer solution are not always constant, and if one condition changes, the other conditions must be changed.

［σ：高分子溶液の表面張力（ｄｙｎｅ／ｃｍ²）の温度（℃）に対する変化率、ｈ：流延時の高分子溶液の厚味（μｍ）、β^s：流延直前の高分子溶液の温度（℃）、β^a：流延時の環境と基板のうち、β^sとの温度差が大きい方の温度（℃）、ν：流延時の高分子溶液の粘度（Ｐａｓ）である。］
（２）流延時の高分子溶液の厚味（ｈ）を１５０μｍ〜７５０μｍにすることを含む、（１）に記載の光学フィルムの製造方法。
（３）前記高分子溶液を流延する速度を５０ｍ／ｍｉｎ〜３００ｍ／ｍｉｎとすることを含む、（１）または（２）に記載の光学フィルムの製造方法。
（４）前記高分子化合物として置換度２．５〜３のセルロースを用いることを含む、（１）〜（３）のいずれか１項に記載の光学フィルムの製造方法。
（５）前記高分子溶液に、該高分子溶液の表面張力の温度に対する変化率（σ）を０．０１ｄｙｎｅ／ｃｍ²℃以上低下させる化合物を含有させることを含む、（１）〜（４）のいずれか１項に記載の光学フィルムの製造方法。
（６）前記高分子溶液に、前記流延時の高分子溶液の粘度（ν）を３Ｐａｓ以上増大させる化合物を含有させることを含む、（１）〜（５）のいずれか１項に記載の光学フィルムの製造方法。
（７）（１）〜（６）のいずれか１項に記載の製造方法によって得られうる光学フィルム。
（８）４０≦Ｒｅ₍₆₃₀₎≦２００、かつ、７０≦Ｒｔｈ₍₆₃₀₎≦３５０を満たす（７）に記載の光学フィルム。
［Ｒｅ₍λ₎は波長λｎｍにおける正面レターデーション（Ｒｅ）値（単位：ｎｍ）、Ｒｔｈ₍λ₎は波長λｎｍにおける膜厚方向のレターデーション（Ｒｔｈ）値（単位：ｎｍ）である。］
（９）棒状化合物または円盤状化合物からなるレターデーション発現剤を少なくとも１種含む、（７）または（８）に記載の光学フィルム。
（１０）前記光学フィルムの任意の５ｃｍ×５ｃｍの面積中の２５０点の遅相軸の角度の最大変化幅が０．０２°〜０．２°である、光学フィルム。
（１１）偏光子と、該偏光子の少なくとも一方に設けられた保護膜とを有し、前記保護膜は、（７）〜（１０）のいずれか１項に記載の光学フィルムである、偏光板。
（１２）（１１）に記載の偏光板を有する液晶表示装置。 Specifically, it has been found that the above problems can be solved by the following means.
(1) A polymer solution in which a polymer compound is dissolved in a solvent is cast on a substrate, and after the solvent is volatilized, the polymer solution is peeled off from the substrate, and the value N represented by Formula 1 is 20 to 19000. The manufacturing method of an optical film including making it become.
Formula 1

[Σ: Rate of change of surface tension (dyne / cm ² ) of polymer solution with respect to temperature (° C.), h: Thickness (μm) of polymer solution at casting, β ^s : Polymer solution just before casting Temperature (° C.), β ^a : Temperature (° C.) having a larger temperature difference from β ^s among the environment and substrate during casting, and ν: Viscosity (Pas) of the polymer solution during casting. ]
(2) The manufacturing method of the optical film as described in (1) including making thickness (h) of the polymer solution at the time of casting into 150 micrometers-750 micrometers.
(3) The manufacturing method of the optical film as described in (1) or (2) including making the speed | rate which casts the said polymer solution into 50 m / min-300 m / min.
(4) The method for producing an optical film according to any one of (1) to (3), comprising using cellulose having a substitution degree of 2.5 to 3 as the polymer compound.
(5) The polymer solution contains a compound that reduces the rate of change (σ) of the surface tension of the polymer solution with respect to temperature by 0.01 dyne / cm ² ° C or more. (1) to (4) The manufacturing method of the optical film of any one of these.
(6) The optical system according to any one of (1) to (5), including containing in the polymer solution a compound that increases the viscosity (ν) of the polymer solution during casting by 3 Pas or more. A method for producing a film.
(7) An optical film obtainable by the production method according to any one of (1) to (6).
(8) The optical film according to (7), wherein 40 ≦ Re ₍₆₃₀₎ ≦ 200 and 70 ≦ Rth ₍₆₃₀₎ ≦ 350.
[Re ₍ λ ₎ is the front retardation (Re) value (unit: nm) at the wavelength λnm, and Rth ₍ λ ₎ is the retardation (Rth) value (unit: nm) in the film thickness direction at the wavelength λnm. ]
(9) The optical film according to (7) or (8), comprising at least one retardation developer comprising a rod-like compound or a discotic compound.
(10) The optical film having a maximum change width of 250 slow axis angles in an arbitrary area of 5 cm × 5 cm of the optical film of 0.02 ° to 0.2 °.
(11) Polarized light having a polarizer and a protective film provided on at least one of the polarizers, wherein the protective film is the optical film according to any one of (7) to (10) Board.
(12) A liquid crystal display device having the polarizing plate according to (11).

(13) The content of the additive added to the polymer solution is 10 to 30% by mass of the mass of the optical film, according to any one of (1) to (6). Manufacturing method of optical film.
(14) The optical film according to any one of (7) to (10), wherein the glass transition temperature (Tg) is 80 to 180 ° C.
(15) The optical film according to any one of (7) to (10), wherein the elastic modulus is 1500 to 5000 MPa.
(16) The optical film according to any one of (7) to (10), wherein the photoelastic coefficient is 50 × 10 ⁻¹³ cm ² / dyn (5 × 10 ⁻¹¹ Pa ⁻¹ ) or less.
(17) The optical film according to any one of (7) to (10), wherein the haze is 0.01 to 2%.
(18) The optical film according to any one of (7) to (10), having silica fine particles having a secondary average particle size of 0.2 to 1.5 μm.
(19) The optical film according to any one of (7) to (10), wherein the moisture permeability after standing at 60 ° C. and 95% relative humidity for 1 hour is 500 to 2000 g / m ² / hr.
(20) The optical film according to any one of (7) to (10), wherein a mass change is 0 to 3% when left to stand at 80 ° C. and 90% relative humidity for 48 hours.
(21) Any of (7) to (10) is a dimensional change of -1.2 to 0.2% when left to stand for 24 hours at 60 ° C and 90% relative humidity and 90 ° C and 3% RH. 2. The optical film according to item 1.

The optical film manufactured by the manufacturing method of the present invention and the polarizing plate using the same have little variation in optical performance depending on the position, and less surface unevenness.
In addition, the liquid crystal display device of the present invention has little luminance unevenness, little color variation and unevenness, and little change in viewing angle characteristics.

Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
“Dissolving” a polymer compound in a solvent in the present specification means that the polymer compound is in a state of forming a substantially uniform liquid phase in the solvent, and this state is called a polymer solution.

  The inventors of the present invention obtained an experimental rule from these relationships based on experiments, and as a result, setting a value such as Equation 1 and setting this value N to 20 to 19000 is a problem such as unevenness. It has been found that it is necessary for producing a liquid crystal display device having no optical film or an optical film for use in the liquid crystal display device.

［σ：高分子溶液の表面張力（ｄｙｎｅ／ｃｍ²）の温度（℃）に対する変化率、ｈ：流延時の高分子溶液の厚味（μｍ）、β^s：流延直前の高分子溶液の温度（℃）、β^a：流延時の環境と基板のうち、β^sとの温度差が大きい方の温度（℃）、ν：流延時の高分子溶液の粘度（Ｐａｓ）である。］ Formula 1

[Σ: Rate of change of surface tension (dyne / cm ² ) of polymer solution with respect to temperature (° C.), h: Thickness (μm) of polymer solution at casting, β ^s : Polymer solution just before casting Temperature (° C.), β ^a : Temperature (° C.) having a larger temperature difference from β ^s among the environment and substrate during casting, and ν: Viscosity (Pas) of the polymer solution during casting. ]

Here, the surface tension (dyne / cm ² ) of the polymer solution can be measured by a surface tension meter (for example, KYOWA CBVP SURFACE TENSIOMETER A3, manufactured by Kyowa Interface Science). Therefore, the rate of change (σ) with respect to the temperature (° C.) of the surface tension (dyne / cm ² ) of the polymer solution is obtained by dividing the difference in surface tension measured at two points near the casting temperature by the difference in measured temperature. It means the value that was made.
Moreover, the environment at the time of casting means the atmosphere under which casting is performed.

Conventionally, when optical films are obtained by casting, studies have been made focusing on the properties of polymer solutions such as viscosity and surface tension and drying conditions in order to improve the uniformity of the film. There was no finding that the preferred range of rolling conditions was closely related.
Equation 1 shows that the value of N is reduced by increasing the viscosity of the polymer solution. However, even if the viscosity is increased in the same way, if the value of βs-βa is large (ie, a sudden temperature change) N) increases, indicating that a phenomenon occurs in which unevenness (fluctuation of the optical axis) deteriorates. About such a point, it was not known at all conventionally.

The above equation is similar to the equation of the mechanism that causes convection of the coating liquid and causes uneven coating (general countermeasures for coating: Convertec 27 (4) 21-25 (1999). This phenomenon is Benard cell. As an image receiving sheet (for example, Japanese Patent Laid-Open No. 2003-312156), it is actively used. On the contrary, a polishing tape (for example, Japanese Patent Laid-Open No. 8-132352) and a magnetic recording material (Japanese Patent Laid-Open No. 10-501644) are used. Attempts have been made to alleviate this in the application of coating.
However, the film formation of the support, which is completely different from the case of producing a coating film in which another composition is coated on the support as described above, or the film formation of a polymer film as in the case of the present application However, there is no description in the publicly known material, and it is completely unexpected that similar and similar non-uniformity occurs. Furthermore, it was unpredictable to reduce the visibility of a liquid crystal display device using this optical film.

  A more preferable range of the value of N is 1000 to 15000, and a more preferable range is 3000 to 13000.

  The problem solved by the present invention is manifested by a relatively thick optical film, and tends to be difficult to recognize with a thin wrap film. Therefore, the method of the present invention can be preferably applied when the thickness (h) of the polymer solution during casting is 150 to 750 μm, more preferably 250 to 700 μm, and even more preferably 300 to 600 μm.

  In addition, the effect of the present invention is more conspicuous when the film must be dried rapidly in order to increase the production rate of the film. Therefore, the method of the present invention can be preferably applied when the casting speed is 50 to 300 m / min, more preferably 55 to 200 m / min, and even more preferably 60 to 150 m / min.

(Polymer compound)
As the polymer compound used in the production method of the present invention, cellulose is preferable, and cellulose having a substitution degree of 2.5 to 3 is more preferable.
Specifically, cellulose acylate (for example, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate), polyethylene terephthalate, polyethersulfone, polyacrylic resin, polyurethane resin, polyester, polycarbonate, Polysulfone, polyether, polymethylpentene, polyether ketone, (meth) acrylonitrile, cycloolefin, and the like can be used. A cellulose acylate or a cycloolefin polymer is preferable, and a cellulose acylate is more preferable.

(Cellulose acylate)
The cellulose acylate preferably used in the present invention will be described in detail. Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of these hydroxyl groups are esterified with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio in which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).
The total acyl substitution degree, that is, DS ² + DS ³ + DS ⁶ is preferably 2.50 to 3.00, more preferably 2.60 to 2.95, and particularly preferably 2.70 to 2.90. DS ⁶ / (DS ² + DS ³ + DS ⁶ ) is preferably 0.315 or more, particularly preferably 0.320 or more. Here, DS ² is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS ³ is the degree of substitution of the hydroxyl group at the 3-position with an acyl group ( Hereinafter, it is also referred to as “acyl substitution degree at the 3-position”), and DS ⁶ is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  The cellulose acylate used in the present invention may have one acyl group or two or more acyl groups. When two or more types of acyl groups are used, one of them is preferably an acetyl group. DSA + DSB, where DSA is the sum of the substitution degrees of the hydroxyl groups at the 2nd, 3rd and 6th positions with an acetyl group, and DSB is the sum of the substitution degrees of the 2nd, 3rd and 6th hydroxyl groups with an acyl group other than the acetyl group The value of is more preferably 2.50 to 2.95, and particularly preferably 2.60 to 2.85. The DSB is 1.70 or less, particularly 1.0 or less. Further, 28% or more of DSB is a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, more preferably 31% or more, and particularly 32% or more is a 6-position hydroxyl group. It is also preferable that it is a substituent. Further, a cellulose acylate film having a DSA + DSB value of 6-position of cellulose acylate of 0.75 or more, further 0.80 or more, and particularly 0.85 or more is preferable. Cellulose acylate having such an acylate group substitution property is preferable because it is a polymer solution that is excellent in solubility in a wide range of solvents and has few insolubles. Furthermore, it is possible to produce a polymer solution having a low viscosity and good filterability. As a result, the optical film obtained by the method of the present invention has few foreign matters, and in particular, when incorporated in a liquid crystal display device and displaying black, it is possible to reduce so-called bright spot foreign matters that shine due to light leakage. It becomes.

  The acyl group having 3 or more carbon atoms of the cellulose acylate used in the present invention may be an aliphatic acyl group or an aryl acyl group, and is not particularly limited. The cellulose acylate used in the present invention is, for example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester or the like, and each may further have a substituted group. Preferred examples of the acyl group include propionyl group, butanoyl group, keptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group, Examples thereof include tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, and cinnamoyl group. Among these, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are more preferable, and propionyl group and butanoyl group are particularly preferable. is there.

In the optical film of the present invention, the polymer component constituting the optical film is preferably made of cellulose acylate having substantially the above definition. “Substantially” means, for example, 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the polymer component. Cellulose acylate particles are preferably used as a raw material for film production. 90% by mass or more of the particles to be used preferably have a particle size of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle size of 1-4 mm. The cellulose acylate particles preferably have a shape as close to a sphere as possible. The bulk specific gravity (apparent density) of the particles thus produced is preferably 0.3 to 0.8 kg / L. If the bulk specific gravity is small, bridging is likely to occur when charging from the silo to the dissolution tank. Conversely, if the bulk specific gravity is large, the solubility is poor. Therefore, a more preferable bulk specific gravity is 0.4 to 0.6. The particle size and bulk specific gravity are adjusted by adjusting the stirring speed and aggregation speed when agglomerating and precipitating.
The viscosity average polymerization degree of the cellulose acylate preferably used in the present invention is 200 to 700, more preferably 250 to 550, still more preferably 250 to 400, and particularly preferably 265 to 380. The viscosity average degree of polymerization can be measured by Uda et al.'S limiting viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538. The viscosity average degree of polymerization is determined from the following formula from the intrinsic viscosity [η] of cellulose acylate measured with an Ostwald viscometer.
Viscosity average degree of polymerization DP = [η] / Km
In the formula, [η] is the intrinsic viscosity of cellulose acylate, and Km is a constant of 6 × 10 ⁻⁴ .

  The cellulose acylate used in the present invention preferably has a narrow molecular weight distribution represented by Mw / Mn (Mw is a weight average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 0.8 to 2, and more preferably 1 to 1.8. When the low molecular weight component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of ordinary cellulose acylate, which is useful. Cellulose acylate having a low low molecular weight component can be obtained by removing the low molecular weight component from cellulose acylate synthesized by a usual method. The removal of the low molecular weight component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular weight components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is in the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized. The cellulose acylate used in the present invention preferably has a moisture content of 2% by mass or less, more preferably 1% by mass or less, and still more preferably a cellulose acylate having a moisture content of 0.7% by mass or less. Rate. In general, cellulose acylate contains water and is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content is obtained.

  These cellulose acylates of the present invention are described in detail on pages 7 to 12 in the raw material cotton and the synthesis method in the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Society for Invention). It is described in.

(Additive)
In addition to the above, the polymer solution according to the present invention includes various additives (for example, plasticizers, ultraviolet inhibitors, deterioration inhibitors, retardation enhancers, fine particles, peeling accelerators) in each preparation step. , Infrared absorbers, etc.), which may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and similarly, mixing of a plasticizer is described in, for example, JP-A-2001-151901. Examples of the peeling accelerator include ethyl esters of citric acid. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any stage in the dope preparation process, but may be performed by adding an additive to the final preparation process of the dope preparation process. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a film is formed in a multilayer, the kind and addition amount of the additive of each layer may differ. Examples thereof are described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques. It is preferable to adjust the glass transition temperature Tg of the film to 80 to 180 ° C. and the elastic modulus measured with a tensile tester to 1500 to 3000 MPa depending on the selection of the types and addition amounts of these additives.
Further, for these details, materials described in detail on page 16 and after in the Invention Association Public Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Invention Association) are preferably used.

(Surfactant: Leveling agent)
The polymer solution of the present invention preferably contains a compound (for example, a surfactant or a leveling agent) that lowers the temperature change rate (σ) of the surface tension of the polymer solution by 0.01 dyne / cm ² ° C or more. . Such compound is preferably a compound that reduces 0.02~10dyne / cm ² ℃, more preferably a compound which decreases 0.025~2dyne / cm ² ℃.
Specifically, the leveling agent is preferably a fluorine leveling agent or a silicone leveling agent, and more preferably a fluorine leveling agent. Use of a fluorine-based leveling agent is preferable because it has high unevenness prevention ability.
The leveling agent is preferably an oligomer or a polymer rather than a low molecular compound.

As the fluorine leveling agent, a polymer having a fluoroaliphatic group is preferable, and a polymer of a repeating unit (polymerization unit) corresponding to the monomer (i) below or a repeating unit corresponding to the monomer (i) below. A copolymer of an acrylic resin, a methacrylic resin, and a vinyl monomer copolymerizable therewith containing a (polymerized unit) and a repeating unit (polymerized unit) corresponding to the monomer (ii) below is useful. Examples of such monomers include Polymer Handbook 2nd ed. , J .; Brandrup, Wiley interscience (1975) Chapter 2, Pages 1-483 can be used.
For example, compounds having one addition polymerizable unsaturated bond selected from acrylic acid, methacrylic acid, acrylic esters, methacrylic esters, acrylamides, methacrylamides, allyl compounds, vinyl ethers, vinyl esters, etc. Can give.

(I) Fluoroaliphatic group-containing monomer represented by the following general formula 1

In the general formula 1, R ¹ represents a hydrogen atom, a halogen atom or a methyl group, preferably a hydrogen atom or a methyl group. X represents an oxygen atom, a sulfur atom or —N (R ¹² ) —, more preferably an oxygen atom or —N (R ¹² ) —, and still more preferably an oxygen atom. R ¹² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms which may have a substituent, more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and further preferably a hydrogen atom or a methyl group. . R _f represents —CF ₃ or —CF ₂ H.
M in the general formula 1 represents an integer of 1 to 6, more preferably 1 to 3, and still more preferably 1.
N in the general formula 1 represents an integer of 1 to 11, more preferably 1 to 9, and still more preferably 1 to 6. R _f is preferably —CF ₂ H.
In addition, two or more kinds of polymer units derived from the fluoroaliphatic group-containing monomer represented by the general formula 1 may be contained in the fluoropolymer as a constituent component.

(Ii) Monomer represented by the following general formula 2 copolymerizable with the above (i)

  General formula 2

In the general formula 2, R ¹³ represents a hydrogen atom, a halogen atom or a methyl group, preferably a hydrogen atom or a methyl group. Y represents an oxygen atom, a sulfur atom or —N (R ¹⁵ ) —, more preferably an oxygen atom or —N (R ¹⁵ ) —, and still more preferably an oxygen atom. R ¹⁵ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and further preferably a hydrogen atom or a methyl group.
R ¹⁴ is a linear, branched or cyclic alkyl group having 1 to 60 carbon atoms which may have a substituent, or an aromatic group which may have a substituent (for example, a phenyl group or Naphthyl group). The alkyl group may include a poly (alkyleneoxy) group. Furthermore, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms is more preferable, and a linear or branched alkyl group having 1 to 10 carbon atoms is very preferable.

  The amount of the fluoroaliphatic group-containing monomer represented by the above general formula 1 used for the production of a preferred fluoropolymer is 10% by mass or more, preferably 50% by mass based on the total amount of the monomer of the fluoropolymer. % Or more, More preferably, it is 70-100 mass%, More preferably, it is the range of 80-100 mass%.

Hereinafter, although the specific structural example of a preferable fluorine-type polymer is shown, it is not this limitation.
In addition, the number in a formula shows the molar ratio of each monomer component. Mw represents a mass average molecular weight.

  The amount of the polymerization unit of the fluoroaliphatic group-containing monomer constituting the fluoropolymer is preferably more than 10% by mass, and more preferably 50 to 100% by mass.

Next, the silicone leveling agent will be described.
Examples of the silicone leveling agent include polydimethylsiloxane having various substituents such as oligomers such as ethylene glycol and propylene glycol, and the side chain and the terminal of the main chain are modified. KF-96 manufactured by Shin-Etsu Chemical Co., Ltd. X-22-945.

In addition, a nonionic surfactant having a hydrophobic group composed of dimethylpolysiloxane and a hydrophilic group composed of polyoxyalkylene can also be preferably used.
Specific examples of these nonionic surfactants include, for example, Nippon Unicar Co., Ltd., silicone surfactants SILWET L-77, L-720, L-7001, L-7002, L-7604, Y-7006, FZ-2101, FZ-2104, FZ-2105, FZ-2110, FZ-2118, FZ-2120, FZ-2122, FZ-2123, FZ-2130, FZ-2154, FZ-2161, FZ-2162, FZ- 2163, FZ-2164, FZ-2166, FZ-2191, and SUPERSILWET SS-2801, SS-2802, SS-2803, SS-2804, SS-2805, and the like.
Further, as a preferable structure of these nonionic surfactants composed of dimethylpolysiloxane having a hydrophobic group and polyoxyalkylene having a hydrophilic group, a dimethylpolysiloxane structure portion and a polyoxyalkylene chain are alternately bonded repeatedly. A linear block copolymer is preferable, and JP-A-6-49486 can be referred to.
Specific examples include silicone surfactants ABN SILWET FZ-2203, FZ-2207, and FZ-2208 manufactured by Nippon Unicar Co., Ltd.

  The amount of the leveling agent added to the polymer solution is preferably 0.001% by mass to 1.0% by mass, and more preferably 0.01% by mass to 0.5% by mass.

(Thickener)
The polymer solution used in the present invention preferably contains a compound (thickener) that increases the viscosity by 3 Pas or more. The thickener is preferably a compound that increases 5 to 100 Pas, and more preferably a compound that increases 8 to 80 Pas.

Although the following are mentioned as a thickener, It is not limited to this.
Poly-ε-caprolactone poly-ε-caprolactone diol poly-ε-caprolactone triol polyvinyl acetate poly (ethylene adipate)
Poly (1,4-butylene adipate)
Poly (1,4-butylene glutarate)
Poly (1,4-butylene succinate)
Poly (1,4-butylene terephthalate)
polyethylene terephthalate)
Poly (2-methyl-1,3-propylene adipate)
Poly (2-methyl-1,3-propylene glutarate)
Poly (neopentyl glycol adipate)
Poly (neopentyl glycol sebacate)
Poly (1,3-propylene adipate)
Poly (1,3-propylene glutarate)
Polyvinyl butyral polyvinyl formal polyvinyl acetal polyvinyl propanal polyvinyl hexanal polyvinyl pyrrolidone polyacrylate (polyacrylate)
Polymethacrylate Cellulose Acetate Cellulose Propionate Cellulose Acetate Butyrate

In addition, smectite, tetrasilica mica, bentonite, silica, montmorillonite and sodium polyacrylate described in JP-A-8-325491, ethylcellulose, polyacrylic acid and organic clay described in JP-A-10-219136 For example, known viscosity modifiers and thixotropic agents can be used.
The content of the thickener can be appropriately determined according to the target viscosity, and can be, for example, 0.001 to 0.5% by mass in the polymer solution.

(Plasticizer)
The film of the present invention preferably contains a plasticizer. Although it does not specifically limit as a plasticizer which can be used, Triphosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. In acid ester systems, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc., in glycolic acid ester systems, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl Less cellulose acylate such as glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate Specific preferred to singly or in combination one. Two or more plasticizers may be used in combination as required.

(Retardation expression agent)
The polymer solution of the present invention may contain a retardation developer. As the retardation developer, a compound having at least two aromatic rings is preferable. The retardation developing agent is preferably used in the range of 0.05 to 20 parts by mass, more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer compound. More preferably, it is used in the range of 2 to 5 parts by mass, and most preferably in the range of 0.5 to 2 parts by mass. Two or more retardation developers may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

In the present specification, the “aromatic ring” includes an aromatic heterocycle in addition to an aromatic hydrocarbon ring.
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, a benzene ring, a condensed benzene ring, and biphenyls are preferable. In particular, a 1,3,5-triazine ring is preferably used. For example, compounds disclosed in JP-A No. 2001-166144 are preferably used.

The number of carbon atoms of the aromatic ring contained in the retardation enhancer is preferably 2 to 20, more preferably 2 to 12, further preferably 2 to 8, and 2 to 6. Is most preferred.
The bond relationship between two aromatic rings can be classified into (a) a condensed ring, (b) a direct bond with a single bond, and (c) a bond through a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene group -O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene group -O-
c8: —CO-alkenylene group—
c9: -CO-alkenylene group -NH-
c10: -CO-alkenylene group -O-
c11: -alkylene group-CO-O-alkylene group-O-CO-alkylene group-
c12: -O-alkylene group -CO-O-alkylene group -O-CO-alkylene group -O-
c13: -O-CO-alkylene group -CO-O-
c14: —NH—CO-alkenylene group—
c15: -O-CO-alkenylene group-

The aromatic ring and the linking group may have a substituent.
Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group, and a non-aromatic heterocyclic group.

It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (for example, a hydroxy group, a carboxy group, an alkoxy group, an alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl, and 2- Each group of a diethylaminoethyl group is included.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.
The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include an acetoxy group.
The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (for example, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.
The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.
The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide.
The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamido group include a methanesulfonamido group, a butanesulfonamido group, and an n-octanesulfonamido group.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.
The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.
The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include a methylureido group.
Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.
The molecular weight of the retardation developer is preferably 300 to 800.

  In the present invention, a rod-like compound having a linear molecular structure can also be preferably used as a retardation developer. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation can be performed using molecular orbital calculation software (for example, WinMOPAC2000, manufactured by Fujitsu Limited) to obtain a molecular structure that minimizes the heat of formation of a compound. The molecular structure being linear means that in the thermodynamically most stable structure obtained by calculation as described above, the angle of the main chain constituting the molecular structure is 140 degrees or more.

As the rod-shaped compound having at least two aromatic rings, a compound represented by the following general formula (1) is preferable.
Formula (1): Ar ¹ -L ¹ -Ar ²
In general formula (1), Ar ¹ and Ar ² are each independently an aromatic group.
In the present specification, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group.
An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group. The heterocycle of the aromatic heterocyclic group is generally unsaturated. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable.
As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom (F, Cl, Br, I, etc.), a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkylamino group (for example, Methylamino group, ethylamino group, butylamino group, dimethylamino group), nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group (for example, N-methylcarbamoyl group, N-ethylcarbamoyl group, N, N -Dimethylcarbamoyl group), sulfamoyl group, alkylsulfamoyl group (for example, N-methylsulfamoyl group, N-ethylsulfamoyl group, N, N-dimethylsulfamoyl group), Ureido group, alkylureido group (for example, N-methylureido group, N, N-dimethylureido group, N, N, N′-tri Methylureido group), alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, heptyl group, octyl group, isopropyl group, s-butyl group, tert-amyl group, cyclohexyl group, Cyclopentyl group), alkenyl group (for example, vinyl group, allyl group, hexenyl group), alkynyl group (for example, ethynyl group, butynyl group), acyl group (for example, formyl, acetyl, butyryl, hexanoyl, Lauryl groups), acyloxy groups (eg, acetoxy group, butyryloxy group, hexanoyloxy group, lauryloxy group), alkoxy groups (eg, methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group) , Heptyloxy group, octyloxy group), aryloxy group ( For example, phenoxy group), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group, pentyloxycarbonyl group, heptyloxycarbonyl group), aryloxycarbonyl group (for example, phenoxy group) Carbonyl group), alkoxycarbonylamino group (for example, butoxycarbonylamino group, hexyloxycarbonylamino group), alkylthio group (for example, methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, heptylthio group, octylthio group) Group), arylthio group (for example, phenylthio group), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, butylsulfonyl group, Nylsulfonyl group, heptylsulfonyl group, octylsulfonyl group), amide group (for example, acetamido group, butyramide group, hexylamide group, laurylamide group) and non-aromatic heterocyclic group (for example, Morpholyl group, pyrazinyl group).

Among these, preferred substituents include halogen atoms, cyano groups, carboxyl groups, hydroxyl groups, amino groups, alkylamino groups, acyl groups, acyloxy groups, amide groups, alkoxycarbonyl groups, alkoxy groups, alkylthio groups, and alkyl groups. Can be mentioned.
The alkyl part and alkyl group of the alkylamino group, alkoxycarbonyl group, alkoxy group and alkylthio group may further have a substituent. Examples of the alkyl moiety and the substituent of the alkyl group include halogen atom, hydroxyl group, carboxyl group, cyano group, amino group, alkylamino group, nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group, sulfamoyl group, alkylsulfur group. Famoyl group, ureido group, alkylureido group, alkenyl group, alkynyl group, acyl group, acyloxy group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, Alkylsulfonyl groups, amide groups and non-aromatic heterocyclic groups are included. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, a hydroxyl group, an amino group, an alkylamino group, an acyl group, an acyloxy group, an acylamino group, an alkoxycarbonyl group, and an alkoxy group are preferable.

In the general formula (1), L ¹ is a divalent linking group selected from an alkylene group, an alkenylene group, an alkynylene group, —O—, —CO— and a combination thereof.
The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group.
The alkylene group preferably has 1 to 20 carbon atoms, more preferably 1 to 15, more preferably 1 to 10, still more preferably 1 to 8, and most preferably 1 to 6. It is.

The alkenylene group and alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure.
The alkenylene group and the alkynylene group preferably have 2 to 10 carbon atoms, more preferably 2 to 8, more preferably 2 to 6, still more preferably 2 to 4, and most preferably 2. (Vinylene group or ethynylene group).
The arylene group preferably has 6 to 20 carbon atoms, more preferably 6 to 16, and still more preferably 6 to 12.

In the molecular structure of the general formula (1), the angle formed by Ar ¹ and Ar ² across L ¹ is preferably 140 degrees or more. More preferably, it is 140 degrees or more and 220 degrees or less.
As the rod-like compound, a compound represented by the following formula (2) is more preferable.

In the general formula (2), Ar ¹ and Ar ² are each independently an aromatic group. The definition and examples of the aromatic group are the same as those for Ar ¹ and Ar ^{2 in} the general formula (I).

In the general formula (2), L ² and L ³ are each independently an alkylene group, —O—, —
It is a divalent linking group selected from the group consisting of CO- and combinations thereof.
The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure.
The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 4, and 1 or 2 (methylene group). Or ethylene group).
L ² and L ³ are particularly preferably —O—CO— or —CO—O—.

In the general formula (2), X is a 1,4-cyclohexylene group, a vinylene group or an ethynylene group.
Specific examples of the compound represented by the general formula (1) are shown below.

  Specific examples (1) to (34), (41), and (42) have two asymmetric carbon atoms at the 1-position and the 4-position of the cyclohexane ring. However, since the specific examples (1), (4) to (34), (41), and (42) have a symmetrical meso type molecular structure, there are no optical isomers (optical activity), and geometric isomers (trans Type and cis type). The trans type (1-trans) and cis type (1-cis) of specific example (1) are shown below.

As described above, it is preferable that the rod-like compound as the retardation enhancer has a linear molecular structure. Therefore, the trans type is preferable to the cis type.
Specific examples (2) and (3) have optical isomers (a total of four isomers) in addition to geometric isomers. As for geometric isomers, the trans type is similarly preferable to the cis type. The optical isomer is not particularly superior or inferior, and may be D, L, or a racemate.
In specific examples (43) to (45), the central vinylene bond includes a trans type and a cis type. For the same reason as described above, the trans type is preferable to the cis type.

A compound represented by the following general formula (3) is also preferable as the retardation developer used in the present invention.

In general formula (3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁹ and R ¹⁰ each independently represents a hydrogen atom or a substituent, and R ¹ , R ² , R ³ , R ⁴ and R ⁵ each represents an electron donating group. As the electron donating group, an alkoxy group, a sulfonamide group, and an amide group are preferable.
R ⁸ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or 1 carbon atom. Represents an alkoxy group having ˜12, an aryloxy group having 6 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 38 carbon atoms, an acylamino group having 2 to 12 carbon atoms, a cyano group, or a halogen atom, and having 2 carbon atoms An alkoxycarbonyl group of ˜28 is preferred.
Hereinafter, specific examples of the compound represented by the general formula (3) and other examples of the retardation enhancer that can be preferably used in the present invention will be shown, but the present invention is not limited thereto.

Two or more rod-like compounds having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the polymer solution may be used in combination as a retardation developer.
The rod-like compound can be synthesized with reference to methods described in literature. References include Mol. Cryst. Liq. Cryst., 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 Page (1989), J. Am. Chem. Soc., 113, 1349 (1991), 118, 5346 (1996), 92, 1582 (1970), J. Org Chem., 40, 420 (1975), Tetrahedron, 48, 16, 3437 (1992).

  Among the retardation developing agents, the aromatic compound is more preferably used in the range of 0.05 to 15 parts by mass and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer. Is more preferable. Two or more kinds of compounds may be used in combination.

(Matting agent)
The polymer solution used in the present invention may contain a matting agent.
It is preferable to add fine particles as a matting agent to the film of the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silica Mention may be made of magnesium and calcium phosphates. Fine particles containing silicon are preferable from the viewpoint of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle size is preferably 0.2 μm to 1.5 μm, more preferably 0.4 μm to 1.2 μm, and most preferably 0.6 μm to 1.0 μm. The primary and secondary particle sizes were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. 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.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the turbidity of the film low. This is particularly preferable because the effect of reducing is great.

Next, the organic solvent in which the cellulose acylate of the present invention is dissolved will be described.
(Chlorine solvent)
In preparing the polymer solution of cellulose acylate of the present invention, a chlorinated organic solvent is preferably used as the main solvent. In the present invention, the type of the chlorinated organic solvent is not particularly limited as long as the object can be achieved by dissolving, casting and forming a film of cellulose acylate. These chlorinated organic solvents are preferably methylene chloride (dichloromethane) and chloroform. Methylene chloride is particularly preferable. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is preferable to use at least 50% by mass of methylene chloride. The non-chlorine organic solvent used in combination with the chlorinated organic solvent in the present invention is described below. That is, as a preferable non-chlorine organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. Further, the ester, ketone, ether and alcohol may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.
Although the following can be mentioned as a combination of the chlorinated organic solvent which is a preferable main solvent of this invention, It is not limited to these.

-Methylene chloride / methanol / ethanol / butanol (75/10/5/5/5, parts by mass),
-Methylene chloride / acetone / methanol / propanol (80/10/5/5, parts by mass),
-Methylene chloride / methanol / butanol / cyclohexane (75/10/5/5/5, parts by mass),
Methylene chloride / methyl ethyl ketone / methanol / butanol (80/10/5/5, parts by mass)
Methylene chloride / acetone / methyl ethyl ketone / ethanol / isopropanol (75/8/5/5/7, parts by mass),
-Methylene chloride / cyclopentanone / methanol / isopropanol (80/7/5/8, parts by mass),
-Methylene chloride / methyl acetate / butanol (80/10/10, parts by mass),
Methylene chloride / cyclohexanone / methanol / hexane (70/20/5/5, parts by mass)
-Methylene chloride / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
Methylene chloride / 1, 3 dioxolane / methanol / ethanol (70/20/5/5, parts by mass),
-Methylene chloride / dioxane / acetone / methanol / ethanol (60/20/10/5/5, parts by mass),
Methylene chloride / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5, parts by mass)
Methylene chloride / methyl ethyl ketone / acetone / methanol / ethanol (70/10/10/5/5, parts by mass),
Methylene chloride / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5, parts by mass)
Methylene chloride / methyl acetoacetate / methanol / ethanol (65/20/10/5, parts by mass),
-Methylene chloride / cyclopentanone / ethanol / butanol (65/20/10/5, parts by mass),
Etc.

(Non-chlorine solvent)
Next, a non-chlorine organic solvent that is preferably used in preparing the polymer solution of cellulose acylate of the present invention will be described. In the present invention, the non-chlorine organic solvent is not particularly limited as long as the object can be achieved as long as the cellulose acylate can be dissolved, cast, and formed into a film. The non-chlorine organic solvent used in the present invention is preferably a solvent selected from esters, ketones and ethers having 3 to 12 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent, and other compounds such as alcoholic hydroxyl groups can be used. It may have a functional group. In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  The non-chlorine organic solvent used in the above cellulose acylate is selected from the various viewpoints described above, and is preferably as follows. That is, a preferred solvent for the cellulose acylate of the present invention is a mixed solvent of three or more different from each other, and the first solvent is selected from methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, and dioxane. And at least one kind or a mixture thereof, the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, and the third solvent is an alcohol or hydrocarbon having 1 to 10 carbon atoms And more preferably an alcohol having 1 to 8 carbon atoms. Note that when the first solvent is a mixed liquid of two or more kinds of solvents, the second solvent may not be provided. The first solvent is more preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be.

The alcohol as the third solvent may be linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. These alcohols and hydrocarbons as the third solvent may be used alone or as a mixture of two or more, and are not particularly limited.
As the third solvent, preferred specific compounds include alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, hexane, Are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.

  The above three types of mixed solvents preferably contain a first solvent in a proportion of 20 to 95% by mass, a second solvent in a proportion of 2 to 60% by mass, and a third solvent in a proportion of 2 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-90 mass%, a 2nd solvent is 3-50 mass%, and also 3-25 mass% of 3rd alcohol is contained. In particular, it is preferable that the first solvent is 30 to 90% by mass, the second solvent is 3 to 30% by mass, and the third solvent is alcohol and 3 to 15% by mass. In addition, when the first solvent is a mixed solution and the second solvent is not used, the first solvent is preferably contained in a ratio of 20 to 90% by mass and the third solvent in a ratio of 5 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-86 mass%, and also a 3rd solvent is contained 7-25 mass%. The non-chlorine-based organic solvent used in the present invention is more specifically described in pages 12 to 16 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Society for Invention). It is described in detail. Preferred combinations of non-chlorine organic solvents of the present invention can include the following, but are not limited thereto.

-Methyl acetate / acetone / methanol / ethanol / butanol (75/10/5/5/5, parts by mass),
-Methyl acetate / acetone / methanol / ethanol / propanol (75/10/5/5/5, parts by mass),
Methyl acetate / acetone / methanol / butanol / cyclohexane (75/10/5/5/5, parts by mass),
・ Methyl acetate / acetone / ethanol / butanol (81/8/7/4, parts by mass)
・ Methyl acetate / acetone / ethanol / butanol (82/10/4/4, parts by mass)
・ Methyl acetate / acetone / ethanol / butanol (80/10/4/6, part by mass)
Methyl acetate / methyl ethyl ketone / methanol / butanol (80/10/5/5, parts by mass),
-Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol (75/8/5/5/7, parts by mass)
Methyl acetate / cyclopentanone / methanol / isopropanol (80/7/5/8, parts by mass),
-Methyl acetate / acetone / butanol (85/10/5, parts by mass),
Methyl acetate / cyclopentanone / acetone / methanol / butanol (60/15/14/5/6, parts by mass),
-Methyl acetate / cyclohexanone / methanol / hexane (70/20/5/5, parts by mass)
Methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
Methyl acetate / 1, 3 dioxolane / methanol / ethanol (70/20/5/5, parts by mass),
Methyl acetate / dioxane / acetone / methanol / ethanol (60/20/10/5/5, parts by mass),
Methyl acetate / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5, parts by mass),

Methyl formate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
-Methyl formate / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5, parts by mass)
Acetone / methyl acetoacetate / methanol / ethanol (65/20/10/5, parts by mass)
Acetone / cyclopentanone / ethanol / butanol (65/20/10/5, parts by mass)
Acetone / 1,3 dioxolane / ethanol / butanol (65/20/10/5, part by mass),
1,3 dioxolane / cyclohexanone / methyl ethyl ketone / methanol / butanol (55/20/10/5/5/5, parts by mass)
Etc.
Furthermore, a cellulose acylate polymer solution can be prepared by the following method.
Prepare a cellulose acylate polymer solution with methyl acetate / acetone / ethanol / butanol (81/8/7/4, parts by mass), filter and concentrate, and then add 2 parts by weight of butanol.
Prepare a cellulose acylate polymer solution with methyl acetate / acetone / ethanol / butanol (84/10/4/2, parts by mass), add 4 parts by weight of butanol after filtration and concentration;
A cellulose acylate polymer solution is prepared with methyl acetate / acetone / ethanol (84/10/6, parts by mass), filtered and concentrated, and then 5 parts by mass of butanol is added additionally.

(Polymer solution properties)
In the polymer solution to be cast in the present invention, the polymer is preferably dissolved in an organic solvent in an amount of 10 to 30% by mass, more preferably 13 to 27% by mass, and particularly 15 to 25% by mass. It is preferable. The method of preparing these concentrations may be a predetermined concentration at the stage of dissolution, or a predetermined concentration by a concentration step described later after preparing in advance as a low-concentration polymer solution (for example, 9 to 14% by mass). You may adjust to a high concentration polymer solution. Furthermore, after preparing a high concentration polymer solution in advance, various additives may be added to obtain a predetermined low concentration cellulose acylate polymer solution.

Next, in the present invention, it is preferable that the aggregate molecular weight of the polymer compound in the diluted polymer solution in which the polymer solution is 0.1 to 5% by mass with an organic solvent having the same composition is 150,000 to 15 million. More preferably, the aggregate molecular weight is 180,000 to 9 million. This aggregate molecular weight can be determined by a static light scattering method. In this case, it is preferable to dissolve so that the inertial square radius simultaneously obtained is 10 to 200 nm. A more preferable inertial square radius is 20 to 200 nm. Furthermore, it is preferable to dissolve so that the second virial coefficient is −2 × 10 ⁻⁴ to 4 × 10 ^−4, and more preferably, the second virial coefficient is −2 × 10 ⁻⁴ to 2 × 10 ^−4. It is.

  Here, definitions of the molecular weight of the aggregate, the inertial square radius, and the second virial coefficient will be described. These were measured using the static light scattering method according to the following method. Although the measurement was performed in a dilute region for the convenience of the apparatus, these measured values reflect the behavior of the dope in the high concentration region of the present invention. First, cellulose acylate is dissolved in a solvent used for the dope to prepare a polymer solution of 0.1% by mass, 0.2% by mass, 0.3% by mass, and 0.4% by mass. In order to prevent moisture absorption, the cellulose acylate was dried at 120 ° C. for 2 hours and measured at 25 ° C. and 10% RH. The dissolution method is carried out according to the method employed at the time of dope dissolution (room temperature dissolution method, cooling dissolution method, high temperature dissolution method). Subsequently, these polymer solution and solvent are filtered through a 0.2 μm Teflon filter (Teflon: registered trademark). The filtered polymer solution is measured for static light scattering at intervals of 10 degrees from 30 degrees to 140 degrees at 25 ° C. using a light scattering measuring device (DLS-700 manufactured by Otsuka Electronics Co., Ltd.). . The obtained data is analyzed by the BERRY plot method. In addition, the refractive index required for this analysis uses the value of the solvent calculated | required with the Abbe refractive system, and the refractive index concentration gradient (dn / dc) uses the differential refractometer (Otsuka Electronics Co., Ltd. product DRM-1021). The measurement is performed using the solvent and polymer solution used in the light scattering measurement.

(Preparation of polymer solution)
Next, with respect to the preparation of the polymer solution (dope) in the present invention, the dissolution method is not particularly limited, and may be room temperature or may be carried out by a cooling dissolution method or a high temperature dissolution method, or a combination thereof. With respect to these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-95854 -45950, JP-A-2000-53784, JP-A-11-322946, JP-A-11-322947, JP-A-2-276830, JP-A-2000-273239, JP-A-11-. JP-A No. 71463, JP-A No. 04-259511, JP-A No. 2000-273184, JP-A No. 11-323017, JP-A No. 11-302388 and the like describe methods for preparing polymer solutions. As long as the dissolution method in these organic solvents described in the above publications is within the scope of the present invention, these techniques can be appropriately applied to the present invention. These details are also described in detail in pages 22 to 25 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued March 15, 2001, Japan Society of Invention and Innovation) for non-chlorine solvent systems. And can be done in this way. Furthermore, the polymer solution of the present invention is usually concentrated and filtered, and this is also the same as that of the Invention Association Public Technical Bulletin No. 2001-1745 (issued March 15, 2001, Invention Association). It is described in detail on the page. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

  The concentration of the polymer solution is characterized in that a high concentration dope can be obtained as described above, and a polymer solution having a high concentration and excellent stability can be obtained without relying on a means of concentration. Furthermore, in order to make it easy to melt | dissolve, after making it melt | dissolve at a low density | concentration, you may concentrate using a concentration means. The concentration method is not particularly limited. For example, the low-concentration polymer solution is guided between the cylinder and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and the polymer solution and A method of obtaining a high-concentration polymer solution while evaporating the solvent by giving a temperature difference between them (for example, JP-A-4-259511), a heated low-concentration polymer solution is blown into a container from a nozzle, A method in which the solvent is flash-evaporated until the molecular solution hits the inner wall of the container from the nozzle, and the solvent vapor is extracted from the container to extract the high-concentration polymer solution from the container bottom (for example, US Pat. No. 2,541,012, US Pat. No. 2,858,229, US Pat. No. 4,414,341, US Pat. No. 4,504,355, etc.) can be used.

  Prior to casting the polymer solution, it is preferable to filter off foreign matters such as undissolved matter, dust and impurities using an appropriate filter medium such as a wire mesh or flannel. For the filtration of the polymer solution, a filter having an absolute filtration accuracy of 0.1 to 100 μm is used, and a filter having an absolute filtration accuracy of 0.5 to 25 μm is preferably used. The thickness of the filter is preferably 0.1 to 10 mm, and more preferably 0.2 to 2 mm. In that case, the filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, further 1.0 MPa or less, and particularly preferably 0.2 MPa or less. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, fluororesins such as tetrafluoroethylene resin can be preferably used, and ceramics, metals and the like are particularly preferably used.

In the present invention, the polymer solution is preferably adjusted to have a certain range of viscosity of the polymer solution. The viscosity is measured, for example, by using about 1 mL of the sample polymer solution using a stress rheometer (CVO 120) manufactured by Bohlin Instruments. Viscosity (unit: Pas) is measured under the condition of applying a displacement of 1% at a dope temperature of 33 ° C. and a frequency of 1 Hz.
The preferred viscosity is 10 to 200 Pas (measurement temperature 33 ° C.). If the viscosity is higher than this range, the fluidity is poor and filtration or casting becomes difficult. If the viscosity is lower than this range, the internal pressure of the casting die is low. It becomes low and cannot be uniformly cast in the width direction, and the thickness variation in the width direction tends to increase. The viscosity of the dope is more preferably 25 to 160 Pas, and most preferably 30 to 120 Pas.
If the viscosity of the polymer solution is within the above range, the burden of filtration is reduced, so that it is possible to use a filter medium having a smaller pore diameter and higher accuracy than in the past. As a result, the cellulose acylate film of the present invention has less foreign matter, and in particular, when incorporated in a liquid crystal display device and displaying black, it is possible to reduce so-called bright spot foreign matter that shines due to light leakage. .

(Film formation)
Next, a method for producing a film using a polymer solution will be described. As the method and equipment for producing the optical film of the present invention, a dope (polymer solution) casting film forming method and a dope casting film forming apparatus are preferably used. The polymer solution prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the polymer solution is defoamed for final preparation. The polymer solution is fed from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a metered amount with high accuracy by, for example, the rotational speed, and the polymer solution is run endlessly from the die (slit) of the pressure die. The cast film is uniformly cast on the metal support in the casting portion, and the dry-dried dope film (also referred to as web) is peeled off from the metal support at the peeling point where the metal support has almost gone around. The both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In addition, in the dope casting film forming method used for the film provided with various functional layers, in addition to the dope casting film forming apparatus, the film such as the undercoat layer, the antistatic layer, the antihalation layer, the protective layer, etc. For surface processing, a coating device is often added. Although each manufacturing process is described briefly below, it is not limited to these.

First, when the prepared polymer solution (dope) is produced by a solvent cast method, the polymer solution is cast on a drum or a band, and the solvent is evaporated to form a film. The concentration of the polymer solution before casting is preferably adjusted so that the solid content is 5 to 40% by mass. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 30 ° C. or lower, and particularly preferably a metal support temperature of −10 to 20 ° C.
Further, JP-A Nos. 2000-301555, 2000-301558, 7-032391, JP-A 3-193316, JP-A-5-086212, JP-A-62-237113, JP-A-2-276607. The techniques described in JP-A-55-014201, JP-A-2-111511, and JP-A-2-208650 may be applied.

(Multilayer casting)
The polymer solution may be cast as a single layer solution on a smooth band or drum as a metal support, or a plurality of polymer solutions of two or more layers may be cast. When casting a plurality of polymer solutions, a film may be produced while casting and laminating polymer solutions from a plurality of casting ports provided at intervals in the traveling direction of the metal support, For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be applied.
Also, a method of forming a film by casting a polymer solution from two casting ports may be employed. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61- No. 947245, JP-A-61-110413, JP-A-61-158413, and JP-A-6-134933. Alternatively, a casting method described in JP-A-56-162617 may be a casting method in which a flow of a high-viscosity polymer solution is wrapped in a low-viscosity polymer solution and the high- and low-viscosity polymer solution is simultaneously extruded. Furthermore, it is preferable that the outer polymer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner polymer solution. It is an aspect. Alternatively, the film is formed by peeling the film formed on the metal support using the first casting port and performing the second casting on the side in contact with the metal support surface using the two casting ports. For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned. The polymer solution to be cast may be the same polymer solution or different polymer solutions, and is not particularly limited. In order to give a function to a plurality of layers, a polymer solution corresponding to the function may be extruded from each casting port. Furthermore, the polymer solution may be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer).

In the conventional single-layer liquid, it is necessary to extrude a high-concentration and high-viscosity polymer solution in order to obtain the required optical film thickness. In many cases, this causes a problem such as a fault or flatness. As a solution to this, a high-viscosity polymer solution can be extruded onto a metal support at the same time by casting a plurality of polymer solutions from a casting port. Not only can be produced, but also the use of a concentrated polymer solution can reduce the drying load and increase the production speed of the film.
In particular, the thickness h of one polymer solution necessary for obtaining a film having the same film thickness can be reduced by co-casting, and the value N expressed by Equation 1 can be reduced. This is a useful means for obtaining a film having a uniform slow axis direction.
In the case of co-casting, the inner and outer thicknesses are not particularly limited, but preferably the outer side is preferably 1 to 50% of the total film thickness, and more preferably 2 to 30%. Here, in the case of co-casting with three or more layers, the total thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness. In the case of co-casting, a film having a laminated structure can be produced by co-casting polymer solutions having different additive concentrations such as the above-mentioned plasticizer, ultraviolet absorber and matting agent. For example, an optical film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. More plasticizer and ultraviolet absorber can be contained in the core layer than in the skin layer, and they may be contained only in the core layer. It is also possible to change the type of plasticizer and UV absorber between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or UV absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Moreover, it is also a preferable aspect to contain a peeling accelerator only in the skin layer on the metal support side. It is also preferable to add more alcohol, which is a poor solvent, to the skin layer than the core layer in order to cool the metal support by the cooling drum method to gel the polymer solution. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Further, the viscosity of the polymer solution during casting may be different between the skin layer and the core layer, and the viscosity of the skin layer is preferably smaller than the viscosity of the core layer, but the viscosity of the core layer is higher than the viscosity of the skin layer. It may be small.

(Casting)
As a method for casting a polymer solution, a method of uniformly extruding the prepared dope from a pressure die onto a metal support, a doctor blade for adjusting the film thickness of the dope once cast on the metal support with a blade Or a reverse roll coater that adjusts with a reversely rotating roll, but a method using a pressure die is preferred. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods listed here, it can be carried out by various methods of casting a polymer solution known in the art. The same effects as those described in the above publication can be obtained. The endlessly running metal support used to manufacture the optical film of the present invention includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt (band) which is mirror-finished by surface polishing. ) Is preferably used. One or two or more pressure dies used for producing the film of the present invention may be installed above the metal support. Preferably 1 or 2 groups. When two or more are installed, the dope amount to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the polymer solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all of the steps may be at the same temperature or may be different at different points in the step. If they are different, it may be a desired temperature just before casting.

(Dry)
In general, the drying of the dope film on the metal support for production is performed by applying hot air from the surface side of the metal support (drum or belt), that is, from the surface of the web on the metal support, A method of applying hot air from the back side, a liquid heat transfer method of controlling the surface temperature by contacting the temperature-controlled liquid from the back side opposite the belt or drum dope casting surface and heating the drum or belt by heat transfer However, the backside liquid heat transfer method is preferable. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 degrees lower than the boiling point of the lowest boiling solvent. Is preferred. This is not the case when the casting dope is cooled and peeled off without drying.

(Extension process)
The retardation of the optical film of the present invention can be adjusted by stretching treatment. Furthermore, there is also a method of positively stretching in the width direction. For example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, JP-A-4-298310, and JP-A-11 -48271, and the like. In order to increase the in-plane retardation value of the film, the produced film is stretched.
The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The stretching of the film may be uniaxial stretching only in the longitudinal or lateral direction, or may be simultaneous or sequential biaxial stretching. Stretching is performed at 1 to 200%. The stretching is preferably 1 to 100%, particularly preferably 1 to 50%. The birefringence of the optical film is preferably such that the refractive index in the width direction is larger than the refractive index in the length direction. Therefore, it is preferable to stretch more in the width direction. In addition, the stretching process may be performed in the middle of the film forming process, or the raw film that has been formed and wound may be stretched. In the former case, the stretching may be performed in a state including the residual solvent amount, and the stretching can be preferably performed at a residual solvent amount of 2 to 30%.

  In the present invention, the thickness of the finished optical film (after drying) can be appropriately adjusted depending on the purpose of use, but it is usually in the range of 5 to 500 μm, preferably in the range of 20 to 180 μm, and particularly VA liquid crystal display. For an apparatus, it is preferable that it is 40-110 micrometers. On the other hand, by setting the film thickness to 110 to 180 μm, the drying load during casting film formation becomes large, but the size of the optical characteristics is proportional to the film thickness, so the desired film thickness can be increased by increasing the film thickness. Optical properties can be achieved. Further, since the moisture permeability also decreases in inverse proportion to the film thickness, increasing the film thickness reduces the moisture permeability and makes it more difficult for water to pass through. This is advantageous in a polarizing plate durability test at 60 ° C. and 90% RH for 500 hours.

The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness. The width of the film obtained as described above is preferably 0.5 to 3 m, more preferably 0.6 to 2.5 m, and still more preferably 0.8 to 2.2 m. The length is preferably 100 to 10,000 m per roll, more preferably 500 to 7000 m, and still more preferably 1000 to 6000 m. When winding, it is preferable to give a knurling to at least one end, the width is 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is 1 to 50 μm, preferably 2 to 20 μm, more preferably 3 to 10 μm. is there. This may be a single push or a double push.
The difference in film thickness in the width direction excluding the knurling part is preferably 5 μm or less, and more preferably 3 μm or less. When the film thickness difference in the width direction is large, when a long film exceeding 4000 m is wound, deformation due to the film thickness difference called a black belt is likely to occur. A sudden film thickness variation with a narrow width is not only a problem of vertical streak-like appearance, but also a problem of luminance unevenness when mounted on a liquid crystal display device. When the film thickness is measured continuously in the width direction, there is no film thickness difference exceeding 0.6 μm between 10 mm at any measurement location. The film thickness difference between 10 mm is preferably 0.5 μm or less.
In order to maintain transparency, the haze is preferably 0.01 to 2%. In order to reduce the haze, the added fine matting agent is sufficiently dispersed to reduce the number of aggregated particles, or the matting agent is used only in the skin layer in order to reduce the addition amount.

注記：
上記のRe(θ)は法線方向から角度θ傾斜した方向におけるレターデーション値を表す。
式（１）におけるnxは面内における遅相軸方向の屈折率を表し、nyは面内においてnxに直交する方向の屈折率を表し、nzはnx及びnyに直交する方向の屈折率を表す。

測定されるフィルムが1軸や2軸の屈折率楕円体で表現できないもの、いわゆる光学軸（optic axis)がないフィルムの場合には、以下の方法によりRth（λ）は算出される。
Ｒｔｈ(λ)は前記Ｒｅ(λ)を、面内の遅相軸（KOBRA 21ADHまたはWRにより判断される）を傾斜軸（回転軸）としてフィルム法線方向に対して−50度から＋50度まで10度ステップで各々その傾斜した方向から波長λnｍの光を入射させて11点測定し、その測定されたレターデーション値と平均屈折率の仮定値及び入力された膜厚値を基にKOBRA 21ADHまたはWRが算出する。
上記の測定において、平均屈折率の仮定値は ポリマーハンドブック（JOHN WILEY＆SONS，INC）、各種光学フィルムのカタログの値を使用することができる。平均屈折率の値が既知でないものについてはアッベ屈折計で測定することができる。主な光学フィルムの平均屈折率の値を以下に例示する： セルロースアシレート（１．４８）、シクロオレフィンポリマー（１．５２）、ポリカーボネート（１．５９）、ポリメチルメタクリレート（１．４９）、ポリスチレン（１．５９）である。これら平均屈折率の仮定値と膜厚を入力することで、KOBRA 21ADHまたはWRはｎｘ、ｎｙ、ｎｚを算出する。この算出されたnx、ny、nzよりNz=（nx-nz）/(nx-ny)が更に算出される。 (optical properties)
[Measurement method]
The characteristics of the optical film of the present invention were measured and measured by the following method.
(Retardation Re, Rth)
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and thickness direction retardation at a wavelength λ, respectively. Re (λ) is measured by making light with a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotating axis) (if there is no slow axis, any in-plane The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing the sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Rth can also be calculated from the following formula (1) and formula (2) based on the value, the assumed value of the average refractive index, and the input film thickness value.

Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. .

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optic axis, Rth (λ) is calculated by the following method.
Rth (λ) is from −50 degrees to +50 degrees with respect to the normal direction of the film, with Re (λ) as the slow axis (indicated by KOBRA 21ADH or WR) in the plane and the tilt axis (rotation axis). Measured at 11 points with light of wavelength λ nm from each inclined direction in 10 degree steps, and KOBRA 21ADH or based on the measured retardation value, average refractive index assumption and input film thickness value Calculated by WR.
In the above measurement, the assumed value of the average refractive index may be the value in the polymer handbook (JOHN WILEY & SONS, INC) and various optical film catalogs. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of the main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx-nz) / (nx-ny) is further calculated from the calculated nx, ny, and nz.

It is preferable that the optical characteristics Re value and Rth value of the film of the present invention satisfy the following formulas (V) and (VI), respectively.
(V): 40 nm ≦ Re ₍₆₃₀₎ ≦ 200 nm
(VI): 70 nm ≦ Rth ₍₆₃₀₎ ≦ 350 nm
In the formulas (V) and (VI), Re ₍ λ ₎ is the front retardation value (unit: nm) at the wavelength λnm, and Rth ₍ λ ₎ is the retardation value (unit: nm) in the film thickness direction at the wavelength λnm. .

More preferably, the following formulas (VII) and (VIII) are satisfied.
(VII): 46 nm ≦ Re ₍₆₃₀₎ ≦ 100 nm
(VIII): 160 nm ≦ Rth ₍₆₃₀₎ ≦ 350 nm
It is preferable for the VA liquid crystal display device using only one optical film and polarizing plate of the present invention to satisfy the following formulas (IX) and (X) in addition to the formulas (VII) and (VIII).
(IX): Rth ₍₆₃₀₎ = a-5.9 Re ₍₆₃₀₎ nm
(X): 520 ≦ a ≦ 600 nm
The central value of the y-intercept a of the straight line represented by the formula (IX) is 560 nm, and the black luminance value of the VA liquid crystal display device increases as a deviates from 560. That is, light is leaked and it is not black. Further, if a is shifted upward from 560, a change in color depending on the viewing angle of the liquid crystal display device becomes large, which is not preferable. Formula (X) shows the allowable range of the a value. For a VA liquid crystal display device using only one polarizing plate, it is particularly preferable that 55 nm ≦ Re ₍₆₃₀₎ ≦ 85 nm and 535 ≦ a ≦ 585 nm. Re ₍₆₃₀₎ and Rth ₍₆₃₀₎ vary depending on the Δnd value of the VA liquid crystal cell to be used. For example, when the Δnd value of the VA liquid crystal cell is 320 nm, the most preferable Re ₍₆₃₀₎ and Rth ₍₆₃₀₎ are 55 to 60 and 185 to 275, respectively. When the Δnd value of the VA liquid crystal cell is 300 nm, the most preferable Re ₍₆₃₀₎ and Rth ₍₆₃₀₎ are 60 to 65 and 160 to 240, respectively.
The variation in the Re value over the entire width is preferably ± 5 nm, and more preferably ± 3 nm. Further, the variation of the Rth value is preferably ± 10 nm, and more preferably ± 5 nm. Moreover, it is preferable that the variation in the Re value and the Rth value in the length direction is also within the range of the variation in the width direction.

According to the film manufacturing method of the present invention, unevenness that is a problem in a liquid crystal display device can be reduced. The unevenness that is a problem in display devices is largely controlled by the shift of the slow axis of the optical film used here. In order to make the unevenness uniform, it is necessary to reduce the fluctuation of this axial shift. It turns out that there is.
When the slow axis is obtained at 250 points in an arbitrary 5 cm × 5 cm area by the film production method of the present invention, the maximum change width of the slow axis angle is 0.02 ° to 0.2 °. An optical film can be obtained.
A preferable range of the change width of the angle is 0.03 ° to 0.18 °, and most preferably 0.04 ° to 0.15 °.

The optical characteristic values of Re and Rth change with changes in mass and dimensional changes due to changes in humidity and aging. The smaller the change in the Re and Rth values, the better. In order to reduce the change in optical properties due to humidity, in addition to using cellulose acylate having a high degree of acyl substitution at the 6-position, various hydrophobic additives (eg, plasticizers, retardation enhancers, UV absorbers, etc.) are used. By doing so, the moisture permeability and the equilibrium moisture content of the optical film are reduced. The preferred moisture permeability is 400 to 2300 g per square meter at 60 ° C. and 95% RH for 24 hours. A preferable equilibrium water content is 3.4% or less at 25 ° C. and 80% RH. When the humidity at 25 ° C. is changed from 10% RH to 80% RH, the change amount of the optical characteristics is preferably 12 nm or less in Re value and 32 nm or less in Rth value. A preferable amount of the hydrophobic additive is 10 to 30%, more preferably 12 to 25%, and particularly preferably 14.5 to 20% with respect to the cellulose acylate. When the additive has volatility or decomposability and a change in the mass or dimensional change of the film occurs, a change in optical properties occurs. Therefore, the amount of change in the mass of the film after 48 hours at 80 ° C. and 90% RH is preferably 5% or less. Similarly, the dimensional change after 24 hours at 60 ° C. and 90% RH or after 24 hours at 90 ° C. and 3% RH is preferably within ± 2%. Even if there is a small dimensional change or mass change, if the photoelastic coefficient of the film is small, the amount of change in optical characteristics is small. Therefore it is preferable photoelastic coefficient of the film is ^{50 × 10 -13 cm 2 /dyn(5.0×10 -10} m 2 / N) or less.

(Haze)
The haze of the optical film of the present invention is preferably 0.01 to 2%, more preferably 0.01 to 0.1%, and still more preferably 0.01 to 0.08%.
The haze can be measured in accordance with JIS K6714 using a haze meter (HGM-2DP, Suga test machine) at 25 ° C. and 60% RH for a sample of 40 mm × 80 mm.

(Mechanical identification)
Next, preferred mechanical properties of the optical film of the present invention will be described.
(Glass transition temperature Tg)
The optical film of the present invention preferably has a glass transition temperature (Tg) of 80 to 180 ° C, more preferably 100 to 170 ° C.
The glass transition temperature (Tg) in the present invention can be measured by the following method. A film sample (unstretched) 5 mm × 30 mm was conditioned at 25 ° C. and 60% RH for 2 hours or more, and then grasped with a dynamic viscoelasticity measuring device (Vibron, DVA-225 (made by IT Measurement Control Co., Ltd.)) Grip elasticity is measured at a gripping point) distance of 20 mm, a temperature increase rate of 2 ° C./min, a measurement temperature range of 30 ° C., 200 ° C., and a frequency of 1 Hz. (° C) is taken and plotted. At that time, a straight line 1 is drawn when a straight line 1 is drawn in the solid region and a straight line 2 is drawn in the glass transition region. The temperature at the intersection of the straight lines 2 is the temperature at which the storage elastic modulus suddenly decreases and the film begins to soften when the temperature rises, and the glass transition temperature Tg (dynamic viscoelasticity) It was.

(Elastic modulus)
The elastic modulus is preferably 1500 to 5000 MPa. More preferably, it is 2000-4000 MPa.
The elastic modulus in the present invention is a film sample of 10 mm × 200 mm, which is conditioned at 25 ° C. and 60% RH for 2 hours. The elastic modulus can be calculated from the initial tensile stress and elongation at 100 mm / min.

(Photoelastic coefficient)
The photoelastic coefficient is preferably 50 × 10 ⁻¹³ cm ² / dyn (5 × 10 ⁻¹¹ Pa ⁻¹ ) or less, preferably 5 × 10 ⁻¹³ cm ² / dyn (5 × 10 ⁻¹² Pa ⁻¹ ). The following is more preferable.
In the present invention, the photoelastic coefficient is a tensile stress applied to the long axis direction of a film sample of 10 mm × 100 mm, and Re at that time is measured with an ellipsometer (M150, JASCO Corporation). The photoelastic coefficient can be calculated from the quantity.

(Polarizer)
The polarizing plate is composed of a polarizer and a protective film (preferably a transparent film) disposed on at least one side (preferably both sides) of the polarizer, and the optical film of the present invention can be used as the protective film. Moreover, when providing a protective film on both surfaces, a normal cellulose acetate film may be used for the other protective film. Examples of the polarizer include an iodine polarizer, a dye polarizer using a dichroic dye, and a polyene polarizer. The iodine polarizer and the dye polarizer are generally produced using a polyvinyl alcohol film. When using the optical film of this invention as a protective film, the preparation methods of a polarizing plate are not specifically limited, It can manufacture by a general method. There is a method in which the obtained cellulose acylate film is alkali-treated, and a polyvinyl alcohol film is immersed and stretched in an iodine polymer solution and bonded to both sides of a polarizer using a completely saponified polyvinyl alcohol aqueous polymer solution. . Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film-treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and is further constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.

The optical film of the present invention is preferably bonded to the polarizer so that the transmission axis of the polarizer and the slow axis of the optical film of the present invention are matched. In addition, when the polarizing plate produced under polarizing plate crossed Nicols was evaluated, the orthogonality accuracy between the slow axis of the optical film of the present invention and the absorption axis of the polarizer (axis perpendicular to the transmission axis) was 1 °. When it was large, it was found that the polarization degree performance under the polarizing plate crossed Nicols was lowered and light leakage occurred. In this case, when combined with a liquid crystal cell, sufficient black level and contrast cannot be obtained. Accordingly, the deviation between the direction of the main refractive index nx of the film of the present invention and the direction of the transmission axis of the polarizing plate is preferably within 1 °, and more preferably within 0.5 °.
The single plate transmittance TT, parallel transmittance PT, and orthogonal transmittance CT of the polarizing plate can be measured using UV3100PC (manufactured by Shimadzu Corporation). The measurement was performed in the range of 380 nm to 780 nm, and the average value of 10 measurements was used for both single plate, parallel and orthogonal transmittance. The polarizing plate durability test was carried out as follows: (1) only the polarizing plate, (2) a polarizing plate attached to glass via an adhesive, and two types of forms. For the measurement of only the polarizing plate, two identical samples are prepared and measured so that the optical compensation sheet is sandwiched between the two polarizers. Two samples (about 5 cm × 5 cm) are prepared by attaching a polarizing plate on glass so that the optical compensation sheet is on the glass side. In single-plate transmittance measurement, the sample is set with the film side facing the light source. Each of the two samples is measured, and the average value is taken as the transmittance of the single plate. The preferable range of polarization performance is 40.0 ≦ TT ≦ 45, 0, 30.0 ≦ PT ≦ 40.0, CT ≦ 2 in the order of single plate transmittance TT, parallel transmittance PT, and orthogonal transmittance CT, respectively. 0.0, and more preferable ranges are 41.0 ≦ TT ≦ 44.5, 34 ≦ PT ≦ 39.0, and CT ≦ 1.3 (the unit is%). In the durability test of the polarizing plate, it is preferable that the amount of change is smaller.
In the polarizing plate of the present invention, the amount of change ΔCT (%) in orthogonal single plate transmittance and the amount of change in polarization ΔP when left at 60 ° C. and 95% RH for 500 hours have the following formulas (j) and (k ) Is satisfied.
(J) −6.0 ≦ ΔCT ≦ 6.0
(K) -10.0 ≦ ΔP ≦ 0.0
Here, the amount of change is a value obtained by subtracting the measured value before the test from the measured value after the test.
By satisfying this requirement, stability during use or storage of the polarizing plate is more effectively ensured.

(surface treatment)
The optical film of the present invention can achieve improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs in a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in JIII Journal of Technical Disclosure No. 2001-1745 (issued on March 15, 2001, Invention Association). In the plasma treatment at atmospheric pressure, which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 kGy is used under 10 to 1000 keV, and more preferably irradiation energy of 20 to 300 kGy is used under 30 to 500 keV. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

The alkali saponification treatment is preferably carried out by a method in which a cellulose acylate film is directly immersed in a saponification solution tank or a method in which a saponification solution is applied to a cellulose acylate film.
Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification treatment coating solution has good wettability because it is applied to the support of the saponification solution, and keeps the surface state good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, and more preferably 12 or more. The reaction conditions at the time of alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water.

(Antireflection layer)
It is preferable to provide a functional film such as an antireflection layer on the protective film disposed on the opposite side of the polarizing plate from the liquid crystal cell. In particular, in the present invention, an antireflection layer in which at least a light scattering layer and a low refractive index layer are laminated in this order on the protective film, or a middle refractive index layer, a high refractive index layer, and a low refractive index layer in this order on the protective film. The antireflection layer laminated with is preferably used.
Further, a hard coat layer, a forward scattering layer, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Hard coat layer)
The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the protective film provided with the antireflection layer. In particular, it is preferably provided between the transparent support and the high refractive index layer. The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound. The curable functional group is preferably a photopolymerizable functional group, and the hydrolyzable functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer. Specific examples of the composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and International Publication No. 00/46617.

(Antistatic layer)
In the case of providing an antistatic layer, it is preferable to impart conductivity with a volume resistivity of 10 ⁻⁸ (Ωcm ⁻³ ) or less. The use of hygroscopic substances, water-soluble inorganic salts, certain surfactants, cationic polymers, anionic polymers, colloidal silica, etc. can give a volume resistivity of 10 ⁻⁸ (Ωcm ⁻³ ). There is a problem that dependency is large, and sufficient conductivity cannot be secured at low humidity. Therefore, a metal oxide is preferable as the conductive layer material. Some metal oxides are colored, but using these metal oxides as the conductive layer material is not preferable because the entire film is colored. Zn, Ti, Al, In, Si, Mg, Ba, Mo, W, or V can be given as the metal that forms the metal oxide without coloring, and a metal oxide containing this as a main component should be used. preferable. Specific examples include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O ₅ , or a composite oxide thereof. In particular, ZnO, TiO ₂ and SnO ₂ are preferable. Examples of containing different atoms include, for example, additives such as Al and In for ZnO, addition of Sb, Nb and halogen elements for SnO ₂ , and Nb and TA for TiO ₂ . Addition is effective. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a material obtained by adhering the above metal oxide to other crystalline metal particles or fibrous materials (for example, titanium oxide) may be used. The volume resistance value and the surface resistance value are different physical properties and cannot be simply compared. However, in order to ensure conductivity of 10 ⁻⁸ (Ωcm ⁻³ ) or less in volume resistance, the conductivity It is sufficient that the layer has a surface resistance value of about 10 ⁻¹⁰ (Ω / □) or less, and more preferably 10 ⁻⁸ (Ω / □). The surface resistance value of the conductive layer needs to be measured as a value when the antistatic layer is the outermost layer, and can be measured in the middle of forming the laminated film described in this patent.

(Liquid crystal display device)
The optical film of the present invention and the polarizing plate using the optical film can be used for liquid crystal cells and liquid crystal display devices in various display modes. For example, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Frequential Liquid Nyst), OCB (Optically Liquid Nyst). ) And HAN (Hybrid Aligned Nematic) have been proposed and can be preferably used in the OCB mode or the VA mode.

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. OCB mode liquid crystal cells are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal compounds are aligned symmetrically between the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. For this reason, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

In the VA mode liquid crystal cell, the rod-like liquid crystal compound is aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which a rod-like liquid crystal compound is aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. 2-176625). (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceedings) 28 (1997) 845) in which VA mode is multi-domained (in MVA mode) for viewing angle expansion (3) A liquid crystal cell of a mode (n-ASM mode) in which a rod-like liquid crystal compound is substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary Proceedings 58-59 (1998) ) Description) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).
The VA mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. In one aspect of the transmissive liquid crystal display device, one optical film of the present invention is disposed between the liquid crystal cell and one polarizing plate, or two optical films are disposed between the liquid crystal cell and both polarizing plates. It is preferably used by arranging.

  In another aspect of the transmissive liquid crystal display device, an optical compensation sheet made of the optical film of the present invention is used as a protective film for a polarizing plate disposed between a liquid crystal cell and a polarizer. The above optical compensation sheet may be used only for the protective film (between the liquid crystal cell and the polarizer) of one polarizing plate, or two (between the liquid crystal cell and the polarizer) of both polarizing plates. The optical compensation sheet may be used for the protective film. When the optical compensation sheet is used only for one polarizing plate, it is particularly preferable to use it as a protective film for the liquid crystal cell side of the backlight side polarizing plate of the liquid crystal cell. For the lamination to the liquid crystal cell, the optical film of the present invention is preferably on the VA cell side. The protective film may be a normal cell rate acylate film, and is preferably thinner than the optical film of the present invention. For example, it is preferably 40 to 80 μm, and examples thereof include, but are not limited to, commercially available KC4UX2M (manufactured by Konica Capto Corporation, 40 μm), KC5UX (manufactured by Konica Capto Corporation, 60 μm), TD80 (manufactured by Fuji Photo Film, 80 μm), and the like. .

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Measurement method]
The characteristics of the optical film of the present invention were measured and measured by the following method.
(Retardation Re, Rth)
Retardation was measured by making light having a wavelength of λ nm incident in the normal direction of the film using a birefringence meter (KOBRA 21ADH (manufactured by Oji Scientific Instruments)) by the method described above.

(Axis misalignment)
A slow axis of 250 points in an arbitrary area of 5 cm × 5 cm was obtained, and the standard deviation of the shaft angle was obtained as an axis deviation.
(village)
The upper and lower polarizing plates of the sample film were adjusted to a crossed Nicol state, and the degree of unevenness was relatively evaluated by visual observation.

[Example 1]
Formation of Cellulose Acylate Film (1) Preparation of Cellulose Acylate Cellulose acylate having an acyl substitution degree of 2.81 was prepared. In this, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid was added, and an acylation reaction was performed at 40 ° C. Thereafter, the degree of substitution was adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
(2) Preparation of polymer solution (1) <1-1> Cellulose acylate solution (A)
The following cellulose acylate solution (A) composition is put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, and then a filter paper having an average pore size of 34 μm and a sintered metal having an average pore size of 10 μm. Filtered with a filter.

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Cellulose acylate solution (A) composition ―――――――――――――――――――――――――――――――――
Cellulose acylate having a degree of substitution of 2.81 100.0 parts by mass Triphenyl phosphate 8.0 parts by mass Biphenyl diphenyl phosphate 4.0 parts by mass Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass ――――――――――――――――――――――――――――

<1-2> Matting Agent Dispersion Next, the following matting agent dispersion composition containing the cellulose acylate solution (A) prepared above was charged into a dispersing machine to prepare a matting agent dispersion.
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Matting agent dispersion composition ――――――――――――――――――――――――――――――――――
Silica particles having an average particle size of 16 nm (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd. 2.0 parts by mass methylene chloride 72.4 parts by mass methanol 10.8 parts by mass cellulose acylate solution (A) 10.3 parts by mass ――――――――――――――――――――――――――――――

<1-3> Retardation developer solution A
Next, the following retardation developer solution A composition containing the cellulose acylate solution (A) prepared by the above method was put into a mixing tank and dissolved by stirring while heating to prepare a retardation developer solution A. .
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Retardation developer solution A composition ――――――――――――――――――――――――――――――――――
Retardation developer A 20.0 parts by mass Methylene chloride 58.3 parts by mass Methanol 8.7 parts by mass Cellulose acylate solution (A) 12.8 parts by mass ――――――――――――――― ――――――――――――――――――
100 parts by mass of the cellulose acylate solution (A), 1.35 parts by mass of the matting agent dispersion, and the retardation developer solution A in the amounts shown in Table 1 were mixed to prepare a dope for film formation.
Retardation expression agent A

<1-4> Retardation developer solution B
Furthermore, the following retardation developer solution B composition containing the cellulose acylate solution (A) prepared above was charged into a mixing tank and dissolved by stirring with heating to prepare retardation developer solution B.
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Retardation developer solution B composition ――――――――――――――――――――――――――――――――――
Retardation developer A 8.0 parts by mass Retardation developer B 12.0 parts by mass Methylene chloride 58.3 parts by mass Methanol 8.7 parts by mass Cellulose acylate solution (A) 12.8 parts by mass ――――――――――――――――――――――――――――

Retardation expression agent B

100 parts by mass of the cellulose acylate solution (A), 1.35 parts by mass of the matting agent dispersion, and 2 parts by mass of the retardation developer solution B are mixed to obtain a polymer solution for film formation ( 1). In addition, the addition ratio of a retardation developing agent is a mass part when the cellulose acylate amount is 100 parts by mass.
Next, the polymer solution (1) was used for film production.

(3) Preparation of polymer solutions (2) to (9) For polymer solution (1), as shown in Table 1, change of the type of polymer compound, change of the type of solvent, or thickener, interface Polymer solutions (2) to (9) were prepared by adding the activator. The content (%) of the thickener and the surfactant is% by mass.

(Casting)
The above polymer solution was cast under the conditions shown in Table 2 using a band casting machine.
Here, β ^s refers to the temperature (° C.) of the polymer solution immediately before casting, and was measured when the polymer solution came out of the pressure die. σ indicates the rate of change of the surface tension (dyne / cm ² ) of the polymer solution with respect to the temperature (° C.), and the surface tension meter (Kyowa) determines the temperature β ^s and the surface tension at a temperature 10 ° C. lower than β ^s. It measured by using the product made from Interface Science, KYOWA CBVP SURFACE TENSIOMETER A3). h represents the thickness (μm) of the polymer solution at the time of casting, and the amount (cc / min) of the polymer solution from the die was divided by the casting speed (m / min) and the casting width (m). Obtained as a value. ν represents the viscosity (Pas) of the polymer solution at the time of casting, and was obtained by measuring η of the prepared dope at a temperature β ^s with a rheometer.
In this example, a cellulose acylate film was produced by stretching a film peeled off from the band with a residual solvent amount of 25 to 35% by mass using a tenter in the width direction at 15%. The tenter was stretched in the width direction while being dried by applying hot air, then contracted by about 5%, then transferred from the tenter conveyance to the roll conveyance, further dried, knurled, and wound up with a width of 1500 mm.

  About the produced cellulose acylate film (optical compensation sheet), the Re value at a wavelength of 550 nm at a temperature of 25 ° C. and 60% relative humidity using a birefringence meter (KOBRA 21ADH (manufactured by Oji Scientific Instruments)) according to the method described above and The Rth value was measured, and the results of measuring the axial deviation are shown in Table 2.

It was confirmed that the glass transition temperature (Tg) of the produced optical film was between 138 ° C and 147 ° C.
Moreover, it was confirmed that the water content after humidity control of the produced optical film at 25 ° C. and 80% relative humidity is between 2.9% and 3.4%.
It was confirmed that the moisture permeability of the produced optical film after standing at 60 ° C. and 95% relative humidity for 24 hours was 800 to 2000 g / m ² / day.
It was confirmed that all the hazes of the produced optical films were in the range of 0.1 to 0.9%.
The secondary average particle size of the matting agent (silica) used was 1.0 μm or less.
It was confirmed that all the produced optical films had an elastic modulus of 4000 MPa or more.
It was confirmed that any change in mass of the produced optical film was allowed to stand for 48 hours under conditions of 80 ° C. and 90% relative humidity within the range of 0 to 3%.
The dimensional change when the produced optical film is allowed to stand for 24 hours under conditions of 60 ° C. and 90% relative humidity and 90 ° C. and 3% RH are both in the range of −1.2 to 0.2%. It was confirmed.
The photoelastic coefficients of the produced optical films were all 50 × 10 ⁻¹³ cm ² / dyn (5 × 10 ⁻¹¹ m ² / N) or less.

In addition, the Re value and the Rth value were measured by changing the wavelength at an environmental humidity of 25 ° C. and 60% relative humidity using an ellipsometer (M-150: manufactured by JASCO Corporation) of the produced optical film. According to this measured value, the Re value and Rth value of the produced optical film were both in the range of 46 ≦ Re ₍₆₃₀₎ ≦ 200 and 70 ≦ Rth ₍₆₃₀₎ ≦ 350.

In contrast to the sample 101, the sample 102 and the sample 103 have changed the axial temperature at the time of casting up or down by 15 ° C., but the axial deviation is hardly changed, and the environmental temperature has almost no influence. It was suggested that the temperature difference with the substrate was dominant.
It was recognized that the axial displacement of the sample 104 was further reduced by changing the substrate temperature with respect to the sample 101.
In contrast to Sample 101, Sample 103, and Sample 105, Sample 106, Sample 107, and Sample 108 to which the surfactant was not added had a large axial misalignment, and a lot of streak-like unevenness was observed visually.
In the sample 110 in which the casting speed was slower than that of the sample 108, although the N value was almost the same, it was recognized that the axial misalignment and unevenness were somewhat improved compared to the sample 108.

In sample 101 in which the solvent methanol was ethanol with respect to sample 115 and the viscosity was lowered, axial misalignment was more effectively suppressed, and visual evaluation also became better.
In contrast to the samples 115 and 106 using the solutions (6) and (1), the axial displacement was further reduced in the samples 116 and 114 using the solutions (7) and (5) to which the thickener was added.
In the samples 112, 113, and 114 using the solutions (2), (3), and (4) in which the methanol ratio is increased with respect to the sample 106 using the solution (1) or the viscosity is increased by using methanol as ethanol or butanol. Axial misalignment decreased more.
The sample 117 using the solution (9) obtained by diluting the solution (8) was much worse than the sample 101 even though the film thickness was almost the same after casting. This suggests that the liquid film thickness during casting is greatly affected.
It was found that the fluctuation of the axial deviation generally corresponds to the visual surface shape, and that the fluctuation width of the axial deviation should be 0.2 ° or less in order to quantify the surface shape.
It was found that the fluctuation range of the N value and the axis deviation is generally correlated, and that the fluctuation range of the axis deviation increases when the N value is high.

[Example 2]
(Preparation of polarizing plate)
A polarizer was produced by adsorbing iodine to a stretched polyvinyl alcohol film.
The films produced in Example 1 (samples 101 to 117: corresponding to TAC1 in FIGS. 1 to 3) were attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. As shown in FIG. 1, it arrange | positioned so that the transmission axis of a polarizer and the slow axis of the film produced in Example 1 might become parallel (FIG. 1).
The saponification treatment was performed under the following conditions.
A 1.5N aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.01 N dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The produced cellulose acylate film was immersed in the aqueous sodium hydroxide solution for 2 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Next, after immersing in the dilute sulfuric acid aqueous solution for 1 minute, the sample was sufficiently dried at 120 ° C. at the end after immersing in water and thoroughly washing away the dilute sulfuric acid aqueous solution.
A commercially available cellulose triacylate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd .: functional film TAC2 in FIG. 2, equivalent to TAC2-1 or 2-2 in FIG. 3) is subjected to saponification treatment, and polyvinyl alcohol type Using an adhesive, it was attached to the opposite side of the polarizer and dried at 70 ° C. for 10 minutes or more.

  As shown in FIG. 2, polarizing plates A1 to A17 were prepared by arranging them so that the transmission axis of the polarizer and the slow axis of the commercially available cellulose triacylate film were orthogonal to each other (FIG. 2).

[Example 3]
(Mounting on VA panel)
A liquid crystal display device as shown in FIG. 3 was produced. That is, an upper polarizing plate (TAC2-1, polarizer, TAC1-1), a VA mode liquid crystal cell, and a lower polarizing plate (TAC1-2, polarizer, TAC2-2) are stacked from the observation direction (upper), and A backlight source was placed.

<Production of liquid crystal cell>
The liquid crystal cell has a cell gap between substrates of 3.6 μm, and a liquid crystal material having negative dielectric anisotropy (“MLC6608”, manufactured by Merck & Co., Inc.) is dropped between the substrates and sealed. Prepared by forming a layer. The retardation of the liquid crystal layer (that is, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn) was set to 300 nm. The liquid crystal material was aligned so as to be vertically aligned.

A commercially available super high contrast product (HLC2-5618 manufactured by Sanlitz Co., Ltd.) was used as the upper polarizing plate (observer side) of the liquid crystal display device (FIG. 3) using the vertical alignment type liquid crystal cell. On the lower polarizing plate (backlight side), polarizing plates A3 to A17 prepared in Example 2 were placed so that the cellulose acylate film (corresponding to TAC1-2 in FIG. 3) was on the liquid crystal cell side. The upper polarizing plate and the lower polarizing plate were attached to the liquid crystal cell via an adhesive. A liquid crystal display device was produced with a crossed Nicol arrangement so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.
As a result of observing the manufactured liquid crystal display device, a neutral black display was realized in the front direction and the viewing angle direction. However, streaky irregularities could be visually recognized when the polarizing plates A106, 107, 108, 110, and 117 were used.

FIG. 1 is a schematic diagram showing a method for laminating films during the production of a polarizing plate produced in Example 2. FIG. FIG. 2 is a cross-sectional view schematically showing the cross-sectional structure of the polarizing plate produced in Example 2. FIG. 3 is a cross-sectional view schematically showing a cross-sectional structure of the liquid crystal display device manufactured in Example 3.

Claims (12)

A polymer solution in which a polymer compound is dissolved in a solvent is cast on a substrate, and after the solvent is volatilized, the polymer solution is peeled off from the substrate, and the value N represented by Formula 1 is 20 to 19000. The manufacturing method of an optical film including doing.
Formula 1

[Σ: Rate of change of surface tension (dyne / cm ² ) of polymer solution with respect to temperature (° C.), h: Thickness (μm) of polymer solution at casting, β ^s : Polymer solution just before casting Temperature (° C.), β ^a : Temperature (° C.) having a larger temperature difference from β ^s among the environment and substrate during casting, and ν: Viscosity (Pas) of the polymer solution during casting. ] The manufacturing method of the optical film of Claim 1 including making thickness (h) of the polymer solution at the time of casting into 150 micrometers-750 micrometers. The manufacturing method of the optical film of Claim 1 or 2 including making the speed | rate which casts the said polymer solution into 50m / min-300m / min. The method for producing an optical film according to claim 1, comprising using cellulose having a substitution degree of 2.5 to 3 as the polymer compound. 5. The method according to claim 1, further comprising containing in the polymer solution a compound that lowers the rate of change (σ) of the surface tension of the polymer solution with respect to temperature by 0.01 dyne / cm ² ° C. or more. The manufacturing method of the optical film of description. The method for producing an optical film according to any one of claims 1 to 5, comprising containing in the polymer solution a compound that increases the viscosity (ν) of the polymer solution during casting by 3 Pas or more. The optical film which can be obtained by the manufacturing method of any one of Claims 1-6. The optical film according to claim 7, wherein 40 ≦ Re ₍₆₃₀₎ ≦ 200 and 70 ≦ Rth ₍₆₃₀₎ ≦ 350 are satisfied.
[Re ₍ λ ₎ is the front retardation (Re) value (unit: nm) at the wavelength λnm, and Rth ₍ λ ₎ is the retardation (Rth) value (unit: nm) in the film thickness direction at the wavelength λnm. ] The optical film according to claim 7 or 8, comprising at least one retardation developer comprising a rod-like compound or a discotic compound. An optical film having a maximum change width of 250 slow axis angles in an arbitrary area of 5 cm × 5 cm of the optical film of 0.02 ° to 0.2 °. The polarizing plate which has a polarizer and the protective film provided in at least one of this polarizer, and the said protective film is an optical film of any one of Claims 7-10. A liquid crystal display device comprising the polarizing plate according to claim 11.

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