JP2007272100A - Optical film, and polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film that can prevent warpage of a panel in an image display device and achieve high display quality while causing no coloring of black display when observed in an oblique direction, and to provide a polarizing plate and a liquid crystal display device using the film. <P>SOLUTION: The optical film is characterized in that a value obtained by dividing a smaller one in a coefficient of linear thermal expansion in the film longitudinal direction and a coefficient of linear thermal expansion in a width direction almost perpendicular to the longitudinal direction, by the larger one is from 0.1 to 0.5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film, a polarizing plate using the same, and a liquid crystal display device.

  In recent years, many types of image display devices such as liquid crystal display devices, organic EL display devices, and PDPs have been developed. Although these uses are diverse, in recent years, developments for personal computer monitor applications and further TV applications have been promoted, and the enlargement of screens is progressing accordingly. The thinning of the entire image display device is progressing simultaneously with the enlargement of the screen, and the thin glass or resin substrate constituting the image display device is likely to warp, and the center of the panel when viewed from the front side (viewing side) It is a problem that the dents and the edge part warp to the front side. When such warping occurs, the edge portions or four corners of the panel may come into contact with the housing, which adversely affects the screen display performance.

On the other hand, various modes have been proposed for the liquid crystal display device depending on the alignment state of the liquid crystal molecules in the liquid crystal cell. Was the 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 to a transparent film is used. For example, Patent Document 1 discloses a technique for applying an optical compensation sheet in which a discotic liquid crystal is applied on a triacetyl cellulose film, aligned, and fixed to a TN mode liquid crystal cell to widen the viewing angle. 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.

However, in the VA mode, almost complete black display is possible in the normal direction of the panel, but when the panel is observed from an oblique direction, light leakage occurs and the viewing angle becomes narrow. To solve this problem, a first retardation plate having a positive refractive index anisotropy satisfying nx> ny = nz and a second phase having a negative refractive index anisotropy satisfying nx = ny> nz A method of reducing light leakage by using a phase difference plate in combination is proposed (for example, Patent Document 2). Further, it has been proposed to improve viewing angle characteristics of a VA mode liquid crystal display device by using an optically biaxial retardation plate of nx>ny> nz (for example, Patent Document 3). Here, nx, ny, and nz respectively indicate refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction in the retardation plate. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the retardation plate, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane, The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.
On the other hand, each liquid crystal system including the IPS system and the OCB system has improved the display system in accordance with the recent increase in demand for liquid crystal televisions (Patent Documents 4 to 7).
Japanese Patent No. 2587398 Japanese Patent No. 3027805 Japanese Patent No. 3330574 JP-A-9-212444 JP 11-316378 A JP 2003-15134 A Japanese Patent Laid-Open No. 10-54982

  Regarding warpage, various members laminated on the front and back sides of glass or resin substrates that do not inherently warp cause expansion / contraction due to heating, moisture absorption / release, etc., and there is a difference between the front and back sides. For this reason, the balance between the front and back forces of the image display device is lost, and the entire panel is warped. Furthermore, in a normal image display device, the front side surface is open, while the back side is incorporated in a housing and is in a semi-sealed state. For this reason, there is a difference in heating and absorption / moisture release between the laminate on the front side and the laminate on the back side that sandwich the substrate, and there is also a difference in expansion / contraction.

  Taking a liquid crystal display device as an example, the liquid crystal display device includes a polarizing plate that creates polarized light on both sides of a liquid crystal cell in which liquid crystal is sealed in a glass substrate, and a retardation plate, an antireflection film, and a brightness enhancement film as necessary. Are stacked together, and the outer peripheral part is fixed with a fixed frame made of a metal plate called stainless steel called “bezel” to form a liquid crystal module, and this liquid crystal module is assembled and housed in a housing together with other components. Manufactured.

  When the power source of the liquid crystal display device is turned on, a difference in temperature or humidity may occur between the front side (viewing side) and the backlight side due to the temperature rising by the backlight. In this case, the temperature and humidity conditions at which the laminate on the front side including the polarizing plate and the laminate on the backlight side are exposed are different from each other with the liquid crystal cell as the boundary. It is done. When the warp occurs, not only the edge portions or four corners of the panel come into contact with the housing, but also a problem in display performance occurs due to the influence of the close contact with the backlight installed on the back surface. Furthermore, when a black display screen is used, a “corner unevenness” phenomenon in which light leaks unevenly at the four corners of the panel (screen) may occur, which is a very large problem in display performance.

  On the other hand, the improvement techniques of the liquid crystal systems proposed in Patent Documents 1 to 7 only reduce light leakage with respect to a certain wavelength range (for example, green light near 550 nm), and other wavelength ranges. Light leakage with respect to (for example, blue light near 450 nm, red light near 650 nm) is not considered. For this reason, for example, when black is displayed and observed from an oblique direction, the so-called color shift problem of coloring blue or red has not been solved.

  An object of the present invention is to prevent warping of a panel of an image display device, and an optical film capable of high display quality in which black display does not cause coloration even when observed obliquely, a polarizing plate and a liquid crystal display using the same The purpose is to provide a device.

These objects have been achieved by the following means.
[1] Of the linear thermal expansion coefficient in the film longitudinal direction and the linear thermal expansion coefficient in the width direction, which is a direction substantially orthogonal to the longitudinal direction, a value obtained by dividing the smaller one by the larger one is 0.5 or less 0 An optical film characterized by being 1 or more.
[2] The optical film according to [1], wherein one of the linear thermal expansion coefficient in the longitudinal direction and the linear thermal expansion coefficient in the lateral direction is 42 or less and the other is 80 or more. .
[3] The above-described [1] or [2], wherein the front retardation Re and the retardation Rth in the film thickness direction at wavelengths of 450 nm, 550 nm, and 650 nm satisfy the following formulas (I) to (III): Optical film.
Formula (I): 0.4 <{(Re (450) / Rth (450)) / (Re (550) / R
th (550))} <0.95
And 1.05 <{(Re (650) / Rth (650)) / (Re (550) / Rth (550))} <1.9.
Formula (II): 0.1 <(Re (450) / Re (550)) <0.95
Formula (III): 1.03 <(Re (650) / Re (550)) <1.93
[Wherein, Re (λ) is a front retardation Re (unit: nm) at a wavelength λnm, and Rth (λ) is a retardation Rth (unit: nm) in a film thickness direction at a wavelength λnm. ]
[4] A method for producing an optical film comprising a stretching step for stretching a film and a shrinking step for shrinking, wherein the stretching end temperature is changed from (crystallization temperature −10 ° C.) to (crystallization temperature + 10 ° C.). The manufacturing method of the optical film characterized by setting it as a range.
[5] The optical film as described in any one of [1] to [3], which is produced by the method according to [4].
[6] The optical film according to any one of [1] to [3] and [5] above, wherein the optical film is a cellulose acylate film.
[7] The optical film as described in [6] above, wherein the acyl substituent of the cellulose acylate consists only of an acetyl group, and the total substitution degree is 2.56 to 3.00.
[8] The degree of substitution of the 2-position hydroxyl group of the cellulose acylate with the acyl group is DS2, the substitution degree of the 3-position hydroxyl group with the acyl group is DS3, and the substitution degree of the 6-position hydroxyl group with the acyl group is DS6. The optical film according to [6] or [7], wherein the following formulas (IV) and (V) are sometimes satisfied.
Formula (IV): 2.0 ≦ (DS2 + DS3 + DS6) ≦ 3.0
Formula (V): DS6 / (DS2 + DS3 + DS6) ≧ 0.315
[9] The above-mentioned [6], wherein the acyl substituent comprises at least two kinds of acetyl group / propionyl group / butanoyl group / benzoyl group, and the total substitution degree is 2.50 to 3.00. The optical film as described in [8].
[10] The optical film as described in any one of [1] to [3] and [5] to [9], which contains a retardation developer.
[11] A polarizing plate having a polarizing film and a pair of protective films sandwiching the polarizing film, wherein at least one of the protective films is [1] to [3] and [5] to [10]. A polarizing plate, which is an optical film according to any one of the above.
[12] A liquid crystal display device comprising the optical film according to any one of [1] to [3] and [5] to [11] or the polarizing plate according to [11].
[13] A liquid crystal display device having a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein the polarizing plate is the polarizing plate according to [11], OCB or VA mode liquid crystal display device.
[14] A VA mode liquid crystal display device using the polarizing plate according to [11] on a backlight side.

  In this specification, “45 °”, “substantially parallel”, or “substantially orthogonal” means that the angle is within a range of strictly less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °. Regarding the angle, “+” means the clockwise direction, and “−” means the counterclockwise direction. Further, the “slow axis” means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

In this specification, “polarizing plate” is cut into a size to be incorporated into a long polarizing plate and a liquid crystal device unless otherwise specified (in this specification, “cutting” includes “punching” and “cutting out”. It is used in the meaning including both of the polarizing plates. In this specification, “polarizing film” and “polarizing plate” are distinguished from each other, and “polarizing plate” is a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. Means.

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction 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 case where there is no slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following formulas (1) and (2).

The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In the 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. .
Formula (2)
Rth = ((nx + ny) / 2-nz) xd

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. This calculated nx
, ny, nz, Nz = (nx-nz) / (nx-ny) is further calculated.

  Since the liquid crystal display device using the film and polarizing plate according to the present invention suppresses warping of the panel due to environmental changes, excellent display performance can be maintained even when the environment changes. Furthermore, it is possible to obtain a high display quality image with little coloration when the black display is viewed from an oblique direction.

  In the present invention, an optical film has optical characteristics in which the wavelength dispersion of retardation is different between the normal direction and an oblique direction inclined with respect to the normal direction, for example, a polar angle direction of 60 degrees. It is characterized by the use. The scope of the present invention is not limited by the display mode of the liquid crystal layer, and can be used for a liquid crystal display device having a liquid crystal layer of any display mode such as VA mode, IPS mode, ECB mode, TN mode, and OCB mode. .

Details of the present invention will be described below.
[Coefficient of thermal expansion of film]
The optical film of the present invention has a value obtained by dividing the smaller one by the larger one out of the linear thermal expansion coefficient in the longitudinal direction of the film and the linear thermal expansion coefficient in the lateral direction, which is a direction substantially orthogonal to the longitudinal direction. .5 or less and 0.1 or more.

Of the linear thermal expansion coefficient in the longitudinal direction of the film and the linear thermal expansion coefficient in the lateral direction that is substantially perpendicular to the longitudinal direction, a value obtained by dividing the smaller one by the larger one is preferably 0.5 or less. 2 or more, more preferably 0.5 or less and 0.25 or more.
According to the study by the inventors, the value obtained by dividing the smaller one by the larger one out of the linear thermal expansion coefficient in the film longitudinal direction and the linear thermal expansion coefficient in the width direction, which is a direction substantially orthogonal to the longitudinal direction, It was a surprising discovery that the warpage of the panel due to the environmental change after the polarizing plate-processed film was bonded to the liquid crystal panel was improved by making the range as described above. The above-described effect is particularly prominent when the optical film is used on both sides of the liquid crystal cell. It is estimated that this is because the stress of warpage due to environmental changes is balanced between the front surface and the rear surface.
Further, it is preferable that one of the linear thermal expansion coefficient in the longitudinal direction and the linear thermal expansion coefficient in the lateral direction is 42 or less and the other is 80 or more.
Furthermore, the linear thermal expansion coefficient (B) in the direction substantially orthogonal to the longitudinal direction of the optical film of the present invention is preferably 42 or less and 2 or more. 35 or less and 3 or more are more preferable, and 30 or less and 5 or more are more preferable. On the other hand, the linear thermal expansion coefficient (A) in the longitudinal direction of the film is preferably 80 or more and 300 or less, and more preferably 90 or more and 250 or less. The warp due to the environmental change of the liquid crystal panel is remarkably improved by bonding the width direction of the film having such characteristics to the long axis direction of the liquid crystal panel. Here, the longitudinal direction refers to the “winding direction of a film wound in a roll shape”.

  The following method can be mentioned as a specific method for measuring the thermal expansion coefficient. That is, a film sample having a width of 3 mm and a length of 35 mm (measurement direction) is cut out. The sample is conditioned for 3 hours or more in an environment of a temperature of 25 ° C. and a relative humidity of 60%. Next, the sample was measured using a TMA (Thermal Mechanical Analyzer: TMA2940 type, manufactured by TA instruments) at a distance between chucks of 25.4 mm, a temperature rising condition of 30 ° C. to 100 ° C. (3 ° C./min), and a tension of 0.04 N. The value ΔL (80-40) (mm) obtained by subtracting the size between the chucks at 40 ° C. from the size between the chucks at 80 ° C. of the sample is calculated, and ΔL (80-40) / (25.4 × 40) is calculated. To obtain a thermal expansion coefficient. Measurement is performed at 10 points at equal intervals along the width direction of the film, and an average value of the measured values is defined as a thermal expansion coefficient. A value obtained by dividing the difference between the maximum value and the minimum value among the measured values by the average value is defined as a variation in the thermal expansion coefficient.

(Production method of the present invention)
As a result of intensive studies, the inventors of the present invention are methods for producing an optical film including a stretching process for stretching a film and a shrinking process for contracting, and the stretching end temperature is determined from (crystallization temperature −10 ° C.) of the film ( It has been found that an optical film with improved panel warpage can be obtained by the production method in the range of crystallization temperature + 10 ° C.
In the present invention, it is important to control the stretching end temperature. The stretching is preferably finished in the range of (crystallization temperature −10 ° C.) to (crystallization temperature + 10 ° C.) with respect to the crystallization temperature of the film after the stretching. If it is stretched at a temperature lower than this temperature range, a sufficient stretch ratio cannot be obtained. On the other hand, if it is stretched at a temperature higher than this temperature range, optical performance changes due to crystallization, which is not preferable.

  In the present invention, the start of the shrinking process refers to the time when a force is applied to the film and physical contraction is started, and the end of the shrinking process is the stop of the application of force to the film. The time when the contraction process is physically terminated. Similarly, the start of the stretching process refers to the time when a force is applied to the film and physical stretching is started, and the end of the stretching process is the stop of the application of force to the film. The time when the stretching process is physically terminated.

  In the present invention, an optical film manufacturing method including a stretching process of stretching in the film transport direction and a contraction process of contracting while gripping the film in a direction substantially orthogonal thereto, or shrinkage contracted in the film transport direction An optical film production method including a process and a stretching process that stretches in a direction substantially orthogonal to the process is preferably used.

First, an optical film manufacturing method including a stretching process of stretching in the film transport direction and a shrinking process of contracting while gripping the film in the width direction of the film will be described.
In this case, the film is stretched in the film transport direction. However, as a method of stretching in the film transport direction, the speed of the film transport roller is adjusted so that the film is wound more than the film peeling speed. A method of increasing the speed is preferably used.
In this case, the film can be contracted substantially perpendicular to the stretching direction by conveying the film while holding the film with a tenter and gradually reducing the width of the tenter.

  Specifically, it is held by a chain-type, screw-type, pantograph-type, linear motor-type tenter, etc., and stretched in the transport direction while stretching the film by gradually narrowing the tenter, and at the same time approximately perpendicular to this. It can shrink in the direction to do.

  On the other hand, in the optical film manufacturing method, including a shrinking process for shrinking in the film transport direction and a stretching process for stretching in a direction substantially perpendicular thereto, the film is held by a chain type, screw type, pantograph type, linear motor type, etc. The film can be shrunk by gradually narrowing the interval between the clips in the film transport direction while stretching in a direction substantially perpendicular to the film transport direction.

  The method described above is preferable because at least a part of the stretching step and the shrinking step can be performed simultaneously.

  In addition, as a stretching apparatus that specifically stretches one of the film transport direction as described above or a direction substantially perpendicular thereto and simultaneously contracts the other and simultaneously increases the film thickness of the film, A FITZ machine manufactured by Ichikin Kogyo Co., Ltd. can be desirably used. This apparatus is described in (Japanese Patent Laid-Open No. 2001-38802).

The stretching ratio in the stretching process and the shrinking ratio in the shrinking process can be arbitrarily selected depending on the values of the desired front retardation Re and the retardation Rth in the film thickness direction. Is preferably 10% or more, and the shrinkage rate in the shrinking step is preferably 5% or more.
In addition, the stretch rate as used in the field of this invention means the ratio of the length of the film after extending | stretching with respect to the length of the film before extending | stretching in a extending direction, and a shrinkage rate is the film before shrinking | contracting in a shrinking direction. It means the ratio of the contracted length of the film after contraction to the length.

  The stretching ratio is preferably 10 to 60%, and particularly preferably 20 to 50%. On the other hand, the shrinkage rate is preferably 5 to 40%, particularly preferably 15 to 35%.

  In order to achieve desired optical properties, the stretching and shrinking steps are preferably performed at the glass transition temperature of the film at the time of processing + (5 to 100) ° C., and the glass transition temperature + (10 to 80) degrees. More preferably,

The film produced by the production method of the present invention preferably satisfies the following formula (A).
(A): 10 ≧ | Rth (550) 10% RH−Rth (550) 60% RH |
(Where Rth (550) 10% RH and Rth (550) 60% RH are Rth (550) at 25 ° C. 10% and 60% RH, respectively)

That is, in the above formula (A), the absolute value of the difference between the value measured at 25 ° C. and 60% RH of the thickness direction retardation Rth (λ) and the value measured at 25 ° C. and 10% RH is preferably 10 nm or less. To express.
The absolute value of the difference between the thickness direction retardation Rth measured at 25 ° C. and 60% RH and the value measured at 25 ° C. and 10% RH is more preferably 5 nm or less.

  The crystallization temperature of the film is a value obtained by reading the peak temperature of an exothermic peak appearing on the high temperature side of the glass transition temperature using a DSC (differential thermal analyzer).

  The glass transition temperature was measured by adjusting a cellulose acylate film sample (unstretched) 5 mm × 30 mm at 25 ° C. and 60% RH for 2 hours or more, and then measuring a dynamic viscoelasticity measuring device “Vibron: DVA-225” { Measured by a distance between grips of 20 mm, a heating rate of 2 ° C./min, a measurement temperature range of 30 ° C. to 200 ° C., a frequency of 1 Hz, and a logarithmic axis as a logarithmic axis. The temperature at which the storage elastic modulus shifts from the solid region to the glass transition region when the temperature (° C.) is taken on the linear axis on the horizontal axis is the glass transition temperature Tg. It was. Specifically, on the obtained chart, when the straight line 1 is drawn in the solid region and the straight line 2 is drawn in the glass transition region, the intersection of the straight line 1 and the straight line 2 decreases rapidly when the temperature rises. The glass transition temperature Tg (dynamic viscoelasticity) was determined because the film started to soften and the temperature started to shift to the glass transition region.

  Moreover, the temperature of the said horizontal axis is the temperature of the film surface measured with the non-contact infrared thermometer.

  The stretching and shrinking treatment may be performed immediately after film formation or may be performed after winding after film formation. In addition, the stretching may be performed in one stage or in multiple stages. When performing in multiple stages, the product of each draw ratio may be within the above range. The shrinking process may be performed in one stage or in multiple stages.

The stretching speed is preferably 5% / min to 1000% / min, and more preferably 10% / min to 500% / min. The stretching is preferably performed by a heat roll or / and a radiant heat source (such as an IR heater) or warm air. Moreover, you may provide a thermostat in order to improve the uniformity of temperature. When performing uniaxial stretching by roll stretching, it is preferable that L / W which is a ratio of distance between rolls (L) and film width (W) is 2.0 to 5.0. The shrinkage rate is preferably 5% / min to 1000% / min, and more preferably 10% / min to 500% / min. Further, both the stretching speed and the shrinking speed may be constant, or the stretching and shrinking may be performed while changing the speed.

It is preferable to provide a preheating step before stretching. The preheating step may be appropriately provided before the stretching step or the shrinking step.
Further heat treatment may be performed after the stretching step or the shrinking step. The heat treatment temperature is preferably 20 ° C. to 10 ° C. higher than the glass transition temperature of the optical film, and the heat treatment time is preferably 1 second to 300 hours. The heating method may be zone heating or partial heating using an infrared heater. You may slit the both ends of a film in the middle or the end of a process. These slit scraps are preferably recovered and reused as raw materials.

In the production method of the present invention, the techniques described below can be used as appropriate.
Regarding the tenter, there is a disclosure in JP-A-11-0777718, and when drying the web while maintaining the width with the tenter, the dry gas blowing method, blowing angle, wind speed distribution, wind speed, air volume, temperature difference, air volume difference, Technology that ensures prevention of quality degradation such as flatness when increasing the speed by the solution casting method or widening the web width by appropriately controlling the ratio of up and down blowing air volume, use of high specific heat drying gas, etc. It is disclosed.

  Japanese Patent Application Laid-Open No. 11-077782 describes an invention in which a stretched thermoplastic resin film is heat treated by providing a temperature gradient in the width direction of the film in the thermal relaxation process after the stretching process in order to prevent unevenness. Yes.

  Furthermore, in order to prevent the occurrence of unevenness, Japanese Patent Application Laid-Open No. 4-204503 discloses an invention in which the film is stretched with the solvent content of 2 to 10% based on the solid content.

  Further, in order to suppress curling due to the regulation of the clip biting width, Japanese Patent Application Laid-Open No. 2002-248680 discloses stretching with a tenter clip biting width D ≦ (33 / (log stretch rate × log volatile content)). Describes an invention that suppresses curling and facilitates film conveyance after the stretching step.

  Furthermore, in order to achieve both high-speed soft film conveyance and stretching, Japanese Patent Application Laid-Open No. 2002-337224 describes an invention that switches tenter conveyance to a first half pin and a second half clip.

Japanese Patent Application Laid-Open No. 2002-187960 discloses that a cellulose ester dope solution is cast on a casting support for the purpose of easily improving the viewing angle characteristics and improving the viewing angle. The web (film) peeled from the support for stretching is stretched 1.0 to 4.0 times in at least one direction while the amount of residual solvent in the web is 100% by mass or less, particularly 10 to 100% by mass. An optically biaxial invention obtained by doing so is described. As a more preferred embodiment, it is described that the film is stretched 1.0 to 4.0 times in at least one direction while the amount of residual solvent in the web is in the range of 100% by mass or less, particularly 10 to 100% by mass. . In addition, as another stretching method, a circumferential speed difference is applied to a plurality of rolls, and a longitudinal stretching is performed using the difference between the circumferential speeds of the rolls, and both ends of the web are fixed with clips or pins. Examples include a method of extending the interval in the traveling direction and stretching in the vertical direction, a method of expanding in the horizontal direction and extending in the horizontal direction, a method of expanding the vertical and horizontal directions simultaneously and stretching in both the vertical and horizontal directions, a method using a combination of these, and the like. It has been. Further, in the case of the so-called tenter method, it is shown that it is preferable to drive the clip portion by the linear drive method because smooth stretching can be performed and the risk of breakage or the like can be reduced.

  Furthermore, in order to produce a retardation film with little additive bleed-out, no delamination phenomenon between layers, good slipperiness and excellent transparency, it is described in JP-A-2003-014933. In addition, a dope A containing a resin, an additive and an organic solvent, and a dope B containing no additive or a resin having a lower additive content than the dope A, an additive and an organic solvent are prepared. The co-cast on the support so that the dope A becomes the core layer and the dope B becomes the surface layer, and after evaporating the organic solvent until it can be peeled off, the web is peeled off from the support and further stretched. The invention describes that the residual solvent in the resin film is stretched 1.1 to 1.3 times in at least one axial direction in the range of 3 to 50% by mass. Furthermore, as a preferred embodiment, the web is peeled from the support and further stretched 1.1 to 3.0 times in the uniaxial direction at a stretching temperature in the range of 140 ° C. to 200 ° C., and a resin and an organic solvent are included. A dope B containing a dope A, a resin, fine particles, and an organic solvent is prepared, and the dope A is co-cast on the support so that the dope A becomes a core layer and the dope B becomes a surface layer, and is organic until it becomes peelable. After the solvent is evaporated, the web is peeled from the support, and the residual solvent amount in the resin film at the time of stretching is 1.1 to 3.0 times in at least one axial direction in the range of 3 to 50% by mass. Stretching, further stretching at least uniaxially in the range of 140 ° C to 200 ° C in a uniaxial direction, 1.1 to 3.0 times, dope A containing resin, organic solvent and additives, and additives Resin with less additive content than dope A A dope B containing an additive and an organic solvent, and a dope C containing a resin, fine particles, and an organic solvent are prepared. The dope A is a core layer, the dope B is a surface layer, and the dope C is a surface opposite to the dope B. After co-casting on the support so as to form a layer and evaporating the organic solvent until it can be peeled, the web is peeled from the support, and the amount of residual solvent in the resin film during stretching is 3 mass Stretching 1.1 to 3.0 times in at least uniaxial direction in the range of 50% by mass to 50% by mass, 1.1 to 3.0 times stretching in at least uniaxial direction in the range of 140 ° C to 200 ° C. The additive amount in the dope A is 1 to 30% by mass with respect to the resin, the additive amount in the dope B is 0 to 5% by mass with respect to the resin, and the additive is a plasticizer or UV absorber. Agent or retardation control agent, in dope A and dope Organic solvents have been described to be utilized by containing more than 50 wt% methylene chloride or methyl acetate with respect to the total organic solvents in.

  Furthermore, in Japanese Patent Application Laid-Open No. 2003-014933, as a method of stretching, a transverse stretching machine called a tenter that stretches in the lateral direction by fixing both ends of the web with clips and pins and widening the interval between the clips and pins in the lateral direction. It is described that can be preferably used. It is also disclosed that stretching or shrinking in the longitudinal direction can be performed by widening or shrinking the interval in the transport direction of the clip or pin in the transport direction (longitudinal direction) using a simultaneous biaxial stretching machine. . In addition, driving the clip portion by the linear drive method is preferable because it can be smoothly stretched and the risk of breakage can be reduced, and as a method of stretching in the longitudinal direction, a difference in peripheral speed is applied to a plurality of rolls. In the meantime, it is suggested that a method of stretching in the longitudinal direction by utilizing the difference in the circumferential speed of the roll can be used. These stretching methods may be used in combination, and the stretching process may be performed in two or more stages, such as (longitudinal stretching, lateral stretching, longitudinal stretching) or (longitudinal stretching, longitudinal stretching). It is described that it is good.

  Further, in order to prevent foaming of the tenter-dried web, improve detachability, and prevent dust generation, Japanese Patent Application Laid-Open No. 2003-004374 discloses that in the drying apparatus, hot air from the dryer is applied to both edges of the web. The invention is described in which the width of the dryer is formed shorter than the width of the web so as not to hit.

  Further, in order to prevent foaming of the tenter-dried web, improve releasability, and prevent dust generation, Japanese Patent Application Laid-Open No. 2003-019775 discloses that both ends of the web are prevented from hitting the holding portion of the tenter. An invention is described in which a wind shield is provided on the inside of the part.

  Furthermore, in order to stably carry and dry, Japanese Patent Application Laid-Open No. 2003-053749 discloses that the thickness after drying of both ends of the film carried by the pin tenter is X μm, the average after drying of the product part of the film When the thickness is T μm, the relationship between X and T is 40 ≦ X ≦ 200 when Equation (1) T ≦ 60, and 40+ (T−60) × 0 when Equation (2) 60 <T ≦ 120. The invention that satisfies the relationship of 52+ (T−120) × 0.2 ≦ X ≦ 400 when .2 ≦ X ≦ 300 or Formula (3) 120 <T is described.

  In order to prevent wrinkles from occurring in the multistage tenter, JP-A-2-182654 discloses a tenter device in which a heating chamber and a cooling chamber are provided in a dryer of the multistage tenter, and left and right clip chains are provided. A separate cooling invention is described.

  Furthermore, in order to prevent web breakage, wrinkles, and conveyance failure, Japanese Patent Application Laid-Open No. 9-077315 describes an invention in which the inner pin density is increased and the outer pin density is decreased in the pin tenter pins. Yes.

  In addition, in order to prevent foaming of the web itself and adhesion of the web to the holding means in the tenter, Japanese Patent Application Laid-Open No. 9-085846 discloses that both side edge holding pins of the web are blown-type cooled in the tenter drying apparatus. An invention is described in which a pin is cooled to below the foaming temperature of the web and the pin immediately before the web is entrapped is cooled to a gelling temperature of the dope + 15 ° C. or lower in the duct type cooler.

  Further, in order to prevent pin tenter losing and improve foreign matter, Japanese Patent Application Laid-Open No. 2003-103542 discloses a web surface that cools the insertion structure and contacts the insertion structure in the pin tenter. An invention relating to a solution casting method in which the temperature does not exceed the gelling temperature of the web is described.

  In order to prevent deterioration in quality such as flatness when the speed is increased by the solution casting method or the width of the web is widened by a tenter, JP-A-11-0777718 discloses a web in the tenter. Is dried at a wind speed of 0.5 to 20 (40) m / s, a transverse temperature distribution of 10% or less, a web up / down air volume ratio of 0.2-1, and a dry gas ratio of 30-250 J /. The invention of Kmol is described. Furthermore, preferable drying conditions are disclosed depending on the amount of residual solvent in drying in the tenter. Specifically, after the web is peeled off from the support, the angle at which the air blows from the blowout port is 30 ° to 150 ° with respect to the film plane until the amount of residual solvent in the web reaches 4% by mass. And the difference between the upper limit value and the lower limit value is within 20% of the upper limit value when the wind speed distribution on the film surface located in the direction in which the drying gas blows out is based on the upper limit value of the wind speed, the drying gas When the amount of residual solvent in the web is 130% by mass or less and 70% by mass or more, the wind speed of the dry gas blown from the blow type dryer on the web surface is 0.5 m / sec. When the residual solvent amount is less than 70% by mass and less than 4% by mass and the residual solvent amount is less than 70% by mass and less than 4% by mass, the dry gas wind blown out at a wind speed of 0.5m / sec to 40m / sec. When the temperature distribution of the drying gas in the width direction of the web is based on the upper limit value of the gas temperature, the difference between the upper limit value and the lower limit value should be within 10% of the upper limit value, the residual solvent in the web It is described that when the amount is 4% by mass or more and 200% by mass or less, the air flow ratio q of the dry gas blown out from the blow-out port of the blow-type dryer located above and below the conveyed web is 0.2 ≦ q ≦ 1. Has been. Furthermore, as a preferred embodiment, at least one kind of gas is used for the drying gas, the average specific heat is 31.0 J / K · mol or more and 250 J / K · mol or less, and the room temperature contained in the drying gas during drying. And the concentration of the liquid organic compound is dried with a drying gas having a saturated vapor pressure of 50% or less.

Further, in order to prevent the flatness and coating from deteriorating due to the generation of contaminants, Japanese Patent Application Laid-Open No. H11-11
Japanese Patent Publication No. 0777719 describes an invention in which a tenter clip incorporates a heated portion in a TAC (triacetyl cellulose) manufacturing apparatus. As a further preferable aspect, a device for removing foreign matter generated at the contact portion between the clip and the web between the time when the tenter clip releases the web and the time when the web is carried again, a jetting gas or liquid, and Remove foreign matter using a brush, the residual amount when the clip or pin contacts the web is 12% by mass or more and 50% by mass or less, and the surface temperature of the contact part between the clip or pin and the web is 60 ° or more. It is disclosed that it is 200 ° or less (more preferably 80 ° or more and 120 ° or less).

  In order to improve flatness, improve quality deterioration due to tearing in the tenter, and increase productivity, Japanese Patent Application Laid-Open No. 11-090943 discloses an arbitrary transport length Lt (m) of the tenter. The ratio Lr = Ltt / Lt of the total length Ltt (m) in the conveying direction of the portion where the clip of the tenter having the same length as Lt holds the web is 1.0 ≦ Lr ≦ 1.99 The invention is described. Furthermore, as a preferable aspect, it is disclosed that the portion holding the web is arranged without a gap when viewed from the web width direction.

  In addition, when introducing a web into a tenter, in order to improve flatness deterioration and instability due to web sagging, Japanese Patent Application Laid-Open No. 11-090944 discloses a plastic film manufacturing apparatus in front of a tenter entrance. Describes an invention having a sag suppressing device in the web width direction. Further, as a more preferable aspect, the sagging suppression device is a rotating roller that rotates in the direction range of 2 to 60 ° in the width direction, has an air intake device on the upper part of the web, and can blow air from under the web. Having a blower is also disclosed.

  In order to prevent deterioration of quality and sagging that hinders productivity, Japanese Patent Application Laid-Open No. 11-090945 discloses that a web peeled from a support has an angle with respect to the horizontal in the TAC manufacturing method. The invention to be introduced into the tenter is described.

  In order to make a film having stable physical properties, Japanese Patent Application Laid-Open No. 2000-289903 discloses a transport device that transports while applying tension in the width direction of the web when the solvent content is 50 to 12% by mass. A web width detecting means, a web holding means, and an invention that has two or more variable bending points, calculates the web width from a detection signal in web width detection, and changes the position of the bending point. Has been.

Furthermore, in order to improve the clipping property, prevent web breakage for a long period of time, and obtain a film with excellent quality, Japanese Patent Application Laid-Open No. 2003-033933 discloses the right and left sides of the web on both the left and right sides near the entrance of the tenter. A web side edge curl prevention guide plate is disposed at least below the upper and lower side edges, and the web facing surface of the guide plate is arranged in the web conveying direction and the web. It is described that it comprises a contact metal part. As a further preferred embodiment, the web contact resin portion of the web facing surface of the guide plate is disposed on the upstream side in the web conveyance direction, the web contact metal portion is disposed on the downstream side, the web contact resin portion of the guide plate, and The level difference (including the inclination) between the web contact metal parts is within 500 μm, and the width of the guide plate web contact resin part and the web contact metal part contacting the web is 2 to 2, respectively. It is 150 mm, the distance of the web contact direction of the web contact resin part of the guide plate and the web contact metal part in the web conveyance direction is 5 to 120 mm, respectively, and the web contact resin part of the guide plate is made of metal. Provided by surface resin processing or resin coating on the guide substrate, the web contact resin part of the guide plate is made of a single resin, the left and right side edges of the web The distance between the web facing surfaces of the guide plates arranged above and below is 3 to 30 mm, and the distance between the web facing surfaces of the upper and lower guide plates at the left and right side edges of the web. In the width direction of the web and inward, it is enlarged at a rate of 2 mm or more per 100 mm width, and the upper and lower guide plates have a length of 10 to 300 mm at the left and right side edges of the web, respectively. And the upper and lower guide plates are arranged so as to be displaced back and forth along the web conveying direction, and the distance of the deviation between the upper and lower guide plates is −200 to +200 mm, the upper guide The web facing surface of the plate is made of only resin or metal, the web contact resin portion of the guide plate is made of Teflon (registered trademark), and the web contact metal portion is It is disclosed that the surface roughness of the web facing surface of the guide plate or the web contact resin portion and / or the web contact metal portion provided on the guide plate is 3 μm or less. Yes. Further, it is also described that the installation position of the upper and lower guide plates for preventing web side edge curl generation is preferably between the peeling side end portion of the support and the tenter introduction portion, and more preferably installed near the tenter entrance. Has been.

  Furthermore, in order to prevent the cutting and unevenness of the web that occurs during drying in the tenter, Japanese Patent Application Laid-Open No. 11-048271 discloses a width stretching apparatus at the time when the solvent content of the web is 50 to 12% by mass after peeling. In the invention, the film is stretched and dried at a time when the web has a solvent content of 10% by mass or less, and a pressure device applies a pressure of 0.2 to 10 KPa from both sides of the web. As a more preferred embodiment, when applying pressure using a nip roll as a method of finishing applying the tension when the solvent content is 4% by mass or more and applying pressure from both sides of the web (film), the nip roll pair is 1 It is also disclosed that about 8 sets are preferable, and the temperature when pressurizing is preferably 100 to 200 ° C.

Japanese Patent Laid-Open No. 2002-036266, which is an invention for obtaining a high-quality thin TAC having a thickness of 20 to 85 μm, has, as a preferable aspect, tension acting on the web along the conveying direction before and after the tenter. The difference of 8 N / mm ² or less, after the peeling process, a preheating process for preheating the web, a stretching process for stretching the web using a tenter after the preheating process, and after the stretching process, And a relaxation step of relaxing the web by an amount smaller than the stretching amount in the stretching step.

  Further, JP 2002-225054 A, which aims to have a dry film thickness of 10 to 60 μm and a low durability with light weight and moisture permeability, has a residual solvent amount of 10 mass after peeling. %, The both ends of the web are gripped with clips, drying shrinkage suppression by holding the width and / or stretching in the width direction is performed, and the formula S = {(Nx + Ny) / 2} −Nz A film having a degree of plane orientation (S) of 0.0008 to 0.0020 (where Nx is the refractive index in the direction of the largest refractive index in the plane of the film, and Ny is relative to Nx) The refractive index in the direction perpendicular to the surface, Nz is the refractive index in the film thickness direction), the time from casting to peeling is set to 30 to 90 seconds, the web after peeling in the width direction and / or Drawing in the longitudinal direction is disclosed.

  Japanese Patent Application Laid-Open No. 2002-341144 discloses a solution film-forming method having a stretching process in which the mass concentration of a retardation increasing agent has a higher optical distribution as it approaches the center in the film width direction in order to suppress optical unevenness. Are listed.

Furthermore, in Japanese Patent Application Laid-Open No. 2003-071863, which is an invention for obtaining a film that does not cause fogging, the draw ratio in the width direction is preferably 0 to 100%, and when used as a polarizing plate protective film, It is described that 5 to 20% is more preferable, and 8 to 15% is most preferable. On the other hand, when used as a retardation film, 10 to 40% is more preferable, and 20 to 30% is most preferable. Ro can be controlled by the draw ratio, and a film having a higher draw ratio is completed. It is disclosed that it is preferable because of its excellent flatness. Further, when the tenter is used, the residual solvent amount of the film is preferably 20 to 100% by mass at the start of the tenter, and the residual solvent amount of the film is 10%.
It is preferable to perform drying while applying a tenter until the content becomes less than or equal to mass%, more preferably less than or equal to 5 mass%.

  Japanese Patent Laid-Open No. 2002-248639, which is an invention that reduces vertical and horizontal dimensional fluctuations during storage under high temperature and high humidity conditions, continuously casts a cellulose ester solution on a support. In the method for producing a film that is peeled and dried, the invention is such that the drying shrinkage satisfies the formula: 0 ≦ dry shrinkage (%) ≦ 0.1 × residual solvent amount (%) when peeling Are listed. Furthermore, as a preferred embodiment, when the residual solvent amount of the cellulose ester film after peeling is in the range of 40 to 100% by mass, at least the residual solvent amount is 30% by mass while holding both ends of the cellulose ester film by tenter conveyance. The amount of residual solvent at the tenter transport entrance of the cellulose ester film after peeling is 40 to 100% by mass, the amount of residual solvent at the exit is 4 to 20% by mass, and the cellulose ester film is transported by tenter transport. It is disclosed that the tension to be conveyed increases from the entrance to the exit of the tenter conveyance, the tension to convey the cellulose ester film by the tenter conveyance and the tension in the width direction of the cellulose ester film are substantially equal. Yes.

  In order to obtain a film having a thin film thickness and excellent optical isotropy and flatness, Japanese Patent Application Laid-Open No. 2000-239403 discloses a residual solvent ratio X at the time of peeling and a residual solvent at the time of introduction into a tenter. It is disclosed that film formation is performed with the relationship of the rate Y being in the range of 0.3X ≦ Y ≦ 0.9X.

  Japanese Patent Application Laid-Open No. 2002-286933 includes a method of stretching a film to be formed by casting, a method of stretching under heating conditions and a method of stretching under solvent-containing conditions, and stretching under heating conditions. In some cases, it is preferable to stretch at a temperature below the glass transition point of the resin. On the other hand, when the cast film is stretched under solvent-impregnated conditions, the once dried film is contacted with the solvent again. It is disclosed that it can be impregnated with a solvent and stretched.

The optical film of the present invention is preferably composed of a cellulose acylate film. Hereinafter, with respect to the optical film, first, cellulose as a raw material of the cellulose acylate film which is a preferred embodiment of the present invention will be described as an example, and then polymers other than cellulose acylate will be described.
(Cellulose acylate)
As the raw material cotton of cellulose acylate, a known raw material can be used (for example, refer to the Japanese Society for Invention and Innovation 2001-1745). Cellulose acylate can also be synthesized by a known method (for example, see Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968)). The viscosity average polymerization degree of cellulose acylate is preferably 200 to 700, more preferably 250 to 500, and most preferably 250 to 350. The number average molecular weight (Mn) of the cellulose ester used in the present invention is preferably 10,000 to 150,000, the weight average molecular weight (Mw) is 20,000 to 500,000, and the Z average molecular weight (Mz) is preferably 5,000 to 550000. Moreover, it is preferable that the molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography is narrow. The specific value of Mw / Mn is preferably 1.5 to 5.0, more preferably 2.0 to 4.5, and most preferably 3.0 to 4.0. preferable.

The acyl group of the cellulose acylate is not particularly limited, but an acetyl group, a propionyl group, a butyryl group (butanoyl group) or a benzoyl group is preferably used. The substitution degree of all acyl groups is preferably 2.0 to 3.0, more preferably 2.2 to 2.95. In this specification, the substitution degree of an acyl group is a value calculated according to ASTM D817.
The acyl group is most preferably an acetyl group alone, and when cellulose acetate having an acyl group as an acetyl group is used, the total substitution degree is preferably 2.56 to 3.00, more preferably 2.75-2.98. The acetylation degree is preferably 57.0 to 62.5%, and more preferably 58.0 to 62.0%. When the total substitution degree or acetylation degree is within this range, Re does not become larger than a desired value due to the conveying tension during casting, there is little in-plane variation, and there is little change in the retardation value due to temperature and humidity.
In particular, it is obtained by substituting the hydroxyl group of the glucose unit constituting the cellulose of cellulose acylate with an acyl group having 2 or more carbon atoms, and the substitution degree of the hydroxyl group at the 2-position of the glucose unit with the acyl group is at DS2, 3-position. When the degree of substitution of the hydroxyl group with an acyl group is DS3 and the degree of substitution of the hydroxyl group at the 6-position with DS6 is DS6, when the following formulas (IV) and (V) are satisfied, desired Re and Rth can be easily obtained. In addition, the Re value variation due to temperature and humidity becomes smaller, which is preferable.
(IV): 2.0 ≦ (DS2 + DS3 + DS6) ≦ 3.0
(V): DS6 / (DS2 + DS3 + DS6) ≧ 0.315
A more preferred range is
(IV): 2.2 ≦ (DS2 + DS3 + DS6) ≦ 2.9
(V): DS6 / (DS2 + DS3 + DS6) ≧ 0.322
It is.

Or, in particular, when the substitution degree of the hydroxyl group of the glucose unit of cellulose acylate with an acetyl group is A, and the substitution degree with a propionyl group, butyryl group or benzoyl group is B, A and B are represented by formulas (VI) and (VII). When it is satisfied, it is easy to obtain desired Re and Rth, and it is easy to realize a high draw ratio without breaking, which is preferable.
(VI): 2.0 ≦ A + B ≦ 3.0
(VII): 0 <B
A more preferred range is
(VI): 2.6 ≦ A + B ≦ 3.0
(VII): 0.5 ≦ B ≦ 1.5
It is.
It is also preferred that the acyl substituent is composed of at least two types of acetyl group / propionyl group / butanoyl group. In this case, the total substitution degree is preferably 2.50 to 3.00, and more preferably 2.75 to 2.98.

(Polymers other than cellulose acylate)
According to the present invention, the method for obtaining a film having preferable physical properties by a production method including a stretching step for stretching a film and a shrinking step for shrinking is not limited to cellulose acylate, and is applicable to all polymers usable as an optical film. Applicable and can be expected to have the same effect as cellulose acylate.
Examples of polymers that can be used as these optical films include polycarbonate copolymers and polymer resins having a cyclic olefin structure. When these polymers are used, a film having good resistance to environmental change may be obtained.

  Examples of the polycarbonate copolymer include a repeating unit represented by the following formula (A) and a repeating unit represented by the following formula (B), and the repeating unit represented by the above formula (A) is 80 to 30 mol in total. % Of the polycarbonate copolymer.

In the above formula (A), R _{1 to} R ₈ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include alkyl groups such as methyl group, ethyl group, isopropyl group, and cyclohexyl group, and aryl groups such as phenyl group. Among these, a hydrogen atom and a methyl group are preferable.

X is the following formula (X), and R ₉ and R ₁₀ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the halogen atom and the alkyl group having 1 to 3 carbon atoms include the same ones as described above.

In the above formula (B), R _{11 to} R ₁₈ are each independently selected from a hydrogen atom, a halon atom, and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include alkyl groups having 1 to 9 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, and a cyclohexyl group, and aryl groups such as a phenyl group, a biphenyl group, and a terphenyl group. It is done. Among these, a hydrogen atom and a methyl group are preferable.

Y is the following group of formulas, and R _{19 to} R ₂₁ , R ₂₃ and R ₂₄ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group are the same as those described above. R ₂₂ and R ₂₅ are each independently selected from hydrocarbon groups having 1 to 20 carbon atoms, such as a methylene group, ethylene group, propylene group, butylene group, cyclohexylene group, phenylene group, naphthylene group, A terphenylene group is mentioned. Examples of Ar _{1 to} Ar ₃ include aryl groups having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.

  As said polycarbonate copolymer, the polycarbonate copolymer which consists of 30-60 mol% of repeating units shown by the following formula (C), and 70-40 mol% of repeating units shown by the following formula (D) is preferable.

  More preferably, it is a polycarbonate copolymer composed of 45 to 55 mol% of the repeating unit represented by the above formula (C) and 55 to 45 mol% of the repeating unit represented by the above formula (D).

In the formula (C), R _{26 to} R ₂₇ are each independently a hydrogen atom or a methyl group, and preferably a methyl group from the viewpoint of handleability.

In the above formula (D), R _{28 to} R ₂₉ are each independently a hydrogen atom or a methyl group, and a hydrogen atom is preferable from the viewpoint of economy, film characteristics and the like.

The optical film in the present invention is preferably one using the above-described polycarbonate copolymer having a fluorene skeleton. As the polycarbonate copolymer having a fluorene skeleton, for example, a blend of polycarbonate copolymers having different composition ratios composed of the repeating unit represented by the above formula (A) and the repeating unit represented by the above formula (B) is often used. The content of the above formula (A) is preferably 80 to 30 mol% of the whole polycarbonate copolymer,
More preferably, it is 75-35 mol%, More preferably, it is 70-40 mol%.

  The copolymer may be a combination of two or more repeating units represented by the above formulas (A) and (B).

  Here, the molar ratio can be determined by, for example, a nuclear magnetic resonance (NMR) apparatus over the entire polycarbonate bulk constituting the optical film.

  The above polycarbonate copolymer can be produced by a known method. As the polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method or the like is preferably used.

  The intrinsic viscosity of the polycarbonate copolymer is preferably 0.3 to 2.0 dl / g. If it is less than 0.3, there is a problem that it becomes brittle and the mechanical strength cannot be maintained. There is a problem of becoming.

The optical film of the present invention may be a composition (blend) of the polycarbonate copolymer and other polymer compounds. In this case, since the polymer compound needs to be optically transparent, it is preferable that the polymer compound is compatible with the polycarbonate copolymer, or the refractive index of each polymer is substantially equal. Specific examples of other polymers include poly (styrene-co-maleic anhydride), and the composition ratio of the polycarbonate copolymer to the polymer compound is 80 to 30% by mass of the polycarbonate copolymer, The polymer compound body is 20 to 70 mass%, preferably the polycarbonate copolymer is 80 to 40 mass%, and the polymer compound body is 20 to 60 mass%. Also in the case of a blend, two or more kinds of repeating units of the polycarbonate copolymer may be combined. In the case of a blend, a compatible blend is preferable, but even if the blend is not completely compatible, the light scattering between the components can be suppressed and the transparency can be improved by adjusting the refractive index between the components. In addition, a blend body may combine 3 or more types of materials, and can combine multiple types of polycarbonate copolymer and another high molecular compound.
The weight average molecular weight of the polycarbonate copolymer is 1,000 to 1,000,000, preferably 5,000 to 500,000. The mass average molecular weight of the other polymer compound is 500 to 100,000, preferably 1,000 to 50,000.

  Examples of a polymer resin having a cyclic olefin structure (hereinafter also referred to as “cyclic polyolefin resin” or “cyclic polyolefin”) include (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) Polymers of cyclic conjugated dienes, (4) vinyl alicyclic hydrocarbon polymers, and hydrides of (1) to (4). Preferred polymers for the present invention are addition (co) polymer cyclic polyolefins containing at least one repeating unit represented by the following general formula (II), and if necessary, a repeating unit represented by the general formula (I) An addition (co) polymer cyclic polyolefin further comprising at least one of the above. Further, addition (co) polymers (including ring-opening (co) polymers) containing at least one cyclic repeating unit represented by the general formula (III) can also be suitably used. The addition (co) polymer cyclic further comprising at least one repeating unit represented by the general formula (III) and, if necessary, at least one repeating unit represented by the general formula (I). Polyolefins can also be preferably used.

In formula, m represents the integer of 0-4. R ^{1 to} R ⁶ are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms, X ^{1 to} X ³ and Y ^{1 to} Y ³ are hydrogen atoms, hydrocarbon groups having 1 to 10 carbon atoms, halogen atoms, halogen atoms in substituted hydrocarbon group having 1 to 10 carbon _{atoms, - (CH 2) n COOR} 11, - (CH 2) n OCOR 12, - (CH 2) n NCO, - (CH 2) n NO 2, - _{(CH 2) n CN, -} (CH 2) n CONR 13 R 14, - (CH 2) n NR 13 R 14, - (CH 2) n OZ, - (CH 2) n W or X ¹ and Y, ¹ , (—CO) ₂ O, (—CO) ₂ NR ¹⁵ composed of X ² and Y ² or X ³ and Y ³ is shown. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are hydrogen atoms, hydrocarbon groups having 1 to 20 carbon atoms, Z is a hydrocarbon group or a hydrocarbon group substituted with halogen, and W is SiR ¹⁶ _p. D _3-p (R ¹⁶ is a hydrocarbon group having 1 to 10 carbon atoms, D is a halogen atom —OCOR ¹⁶ or —OR ¹⁶ , p is an integer of 0 to 3), and n is an integer of 0 to 10 .

By introducing a polarizable large functional group in a substituent ^{X 1 ~X 3, Y 1 ~Y} 3, by increasing the thickness-direction retardation of the optical film (Rth), in-plane retardation (Re) The expression can be increased. A film having a high Re developability can increase the Re value by stretching in the film forming process.
Norbornene-based addition (co) polymers are disclosed in JP-A No. 10-7732, JP-T 2002-504184, US2004229157A1, or WO2004 / 070463A1. It can be obtained by addition polymerization of norbornene-based polycyclic unsaturated compounds. If necessary, norbornene-based polycyclic unsaturated compounds and conjugated dienes such as ethylene, propylene, butene, butadiene and isoprene; nonconjugated dienes such as ethylidene norbornene; acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride It is also possible to carry out addition polymerization with linear diene compounds such as acid, acrylic acid ester, methacrylic acid ester, maleimide, vinyl acetate and vinyl chloride. This norbornene-based addition (co) polymer is sold under the name of Apel by Mitsui Chemicals, Inc., and has different glass transition temperatures (Tg) such as APL8008T (Tg70 ° C), APL6013T (Tg125 ° C) or APL6015T ( Grades such as Tg145 ° C). Pellets such as TOPAS 8007, 6013 and 6015 are sold by Polyplastics Co., Ltd. Further, Appear 3000 is sold by Ferrania.

Norbornene-based polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196736, JP-A-60-26024, JP-A-62-19807, JP-A-2003-159767, or JP-A-2004-309799. As disclosed in No. 1, etc., a polycyclic unsaturated compound is produced by addition polymerization or metathesis ring-opening polymerization and then hydrogenation. In the norbornene-based polymer used in the present invention, R ^{5 to} R ⁶ are preferably a hydrogen atom or —CH ₃ , X ³ and Y ³ are preferably a hydrogen atom, Cl, —COOCH ₃ , and other groups are appropriately selected. The This norbornene resin is sold under the trade name Arton G or Arton F by JSR Co., Ltd., and Zeonor ZF14, ZF16, Zeonex 250 or Zeonex 250 by Nippon Zeon Co., Ltd. They are commercially available under the trade name 280 and can be used.

  The optical film of the present invention preferably contains a retardation developer (hereinafter also referred to as “retardation increasing agent”). Hereinafter, a method for controlling Re representing front retardation and Rth representing retardation in the film thickness direction will be described.

(Re control method Retardation increasing agent whose maximum absorption wavelength (λmax) is shorter than 250 nm)
In order to control the absolute value of Re of the cellulose acylate film of the present invention, it is preferable to use a compound having a maximum absorption wavelength (λmax) shorter than 250 nm as the retardation increasing agent in the ultraviolet absorption spectrum of the solution. By using such a compound, the absolute value can be controlled without substantially changing the wavelength dependency of Re in the visible region.
“Retardation-increasing agent” is measured at a wavelength of 550 nm of a cellulose acylate film produced in the same manner except that Re measured at a wavelength of 550 nm of a cellulose acylate film containing an additive does not contain the additive. It means “additive” which is 20 nm or more higher than Re (when converted to a film thickness of 80 μm). The increase in Re is preferably 30 nm or more, more preferably 40 nm or more, and most preferably 60 nm or more.
From the viewpoint of the function of the retardation increasing agent, rod-like compounds are preferable, preferably having at least one aromatic ring, and more preferably having at least two aromatic rings.

  The rod-like compound preferably has a linear molecular structure. 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 (eg, 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 the angle of the molecular structure is 140 degrees or more in the thermodynamically most stable structure obtained by calculation as described above.

The rod-shaped compound preferably exhibits liquid crystallinity. More preferably, the rod-like compound exhibits liquid crystallinity upon heating (has thermotropic liquid crystallinity). The liquid crystal phase is preferably a nematic phase or a smectic phase.
Preferred compounds are described in JP-A-2004-4550, but are not limited thereto. Two or more rod-shaped compounds having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.

  The rod-like compound can be synthesized with reference to methods described in literature. As literature, Mol. Cryst. Liq. Cryst. 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 (1989), J. Am. Am. Chem. Soc. 113, p. 1349 (1991), p. 118, p. 5346 (1996), p. 92, p. 1582 (1970). Org. Chem. 40, 420 (1975), Tetrahedron, 48, 16, 1637 (1992).

  The addition amount of the retardation increasing agent is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, based on the amount of cellulose acylate.

(Rth control method Retardation increasing agent whose maximum absorption wavelength (λmax) is longer than 250 nm)
In order to express desired Rth, it is preferable to use a retardation increasing agent.
The term “retardation increasing agent” as used herein means that the Rth measured at a wavelength of 550 nm of a cellulose acylate film containing an additive is exactly the same except that the additive does not contain the additive. Means an “additive” that is 20 nm or more higher than the Rth measured in (when converted to a film thickness of 80 μm). The increase in Rth is preferably 30 nm or more, more preferably 40 nm or more, and most preferably 60 nm or more.

The retardation increasing agent is preferably a compound having at least two aromatic rings. The retardation increasing agent is preferably used in the range of 0.01 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 cellulose acylate. 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 types of retardation increasing agents may be used in combination.
The retardation increasing agent preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.
The retardation increasing agent for controlling Rth preferably does not affect Re expressed by stretching, and a discotic compound is preferably used.
The discotic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring, and 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, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, compounds disclosed in JP-A No. 2001-166144 are preferably used.
The aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. The aromatic compound is preferably used in the range of 0.05 to 15 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 cellulose acylate. Two or more kinds of compounds may be used in combination.

(Control method of Rth Method using optically anisotropic layer)
As a method for controlling Rth without affecting Re expressed by stretching, a method of coating an optically anisotropic layer such as a liquid crystal layer is preferably used.
As a specific example of the liquid crystal layer, a method of aligning the discotic liquid crystal so that the angle between the disk surface and the optical film surface is within 5 degrees (Japanese Patent Laid-Open No. 10-312166), A method of aligning the major axis and the above-mentioned optical film surface to be within 5 degrees (Japanese Patent Laid-Open No. 2000-304932) can be mentioned.

  A cellulose acylate film (also referred to as an optical compensation film) having an optically anisotropic layer is a liquid crystal display device, in particular, an increase in viewing angle contrast of an OCB mode or VA mode liquid crystal display device, and color shift depending on the viewing angle. Contributes to mitigation. The optical compensation film may be disposed between the observer-side polarizing plate and the liquid crystal cell, may be disposed between the back-side polarizing plate and the liquid crystal cell, or may be disposed on both. For example, it can be incorporated into the liquid crystal display device as an independent member, or a protective film that protects the polarizing film can be provided with optical characteristics and function as a transparent film. It can also be incorporated inside the display device. An alignment film for controlling the alignment of the liquid crystalline compound in the optically anisotropic layer may be provided between the cellulose acylate film and the optically anisotropic layer. Moreover, as long as the optical properties described later are satisfied, the cellulose acylate and the optically anisotropic layer may each be composed of two or more layers. The optically anisotropic layer will be described in more detail.

[Optically anisotropic layer]
The optically anisotropic layer may be directly formed on the surface of the cellulose acylate film, or may be formed on the alignment film by forming an alignment film on the cellulose acylate film. It is also possible to transfer a liquid crystalline compound layer formed on another substrate onto a cellulose acylate film using an adhesive, an adhesive, or the like.
Examples of the liquid crystalline compound used for forming the optically anisotropic layer include a rod-like liquid crystalline compound and a discotic liquid crystalline compound (hereinafter, the discotic liquid crystalline compound may be referred to as a “discotic liquid crystalline compound”). The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal. Further, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, when a low-molecular liquid crystalline compound is used for the production of the optically anisotropic layer, the optically anisotropic layer In the process of forming, the compound may be cross-linked and no longer exhibits liquid crystallinity.

(Bar-shaped liquid crystalline compound)
Examples of the rod-like liquid crystalline compound that can be used in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, and cyano-substituted phenylpyrimidines. Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. The rod-like liquid crystalline compound includes a metal complex. A liquid crystal polymer containing a rod-like liquid crystal compound in a repeating unit can also be used. In other words, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline compounds, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemical Review Vol. Described in Chapter 3.

The birefringence of the rod-like liquid crystalline compound used in the present invention is preferably in the range of 0.001 to 0.7.
The rod-like liquid crystalline compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.

(Discotic liquid crystalline compounds)
Examples of discotic liquid crystalline compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  The discotic liquid crystalline compound exhibits liquid crystallinity with a structure in which a linear alkyl group, an alkoxy group or a substituted benzoyloxy group is radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation.

As described above, when an optically anisotropic layer is formed from a liquid crystalline compound, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, a low-molecular discotic liquid crystalline compound has a group that reacts with heat or light, and the group reacts with heat or light to polymerize or crosslink to increase the molecular weight. When a layer is formed, the compound contained in the optically anisotropic layer may no longer have liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. Moreover, about superposition | polymerization of a discotic liquid crystalline compound, Unexamined-Japanese-Patent No. 8-27284 has description.

  In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group.

  In the present invention, in the optically anisotropic layer, the molecules of the rod-like compound or the discotic compound are fixed in an oriented state. The orientation average direction of the molecular symmetry axis of the liquid crystal compound at the interface on the optical film side has an intersection angle with the slow axis in the plane of the optical film of about 45 degrees. In this specification, “approximately 45 °” refers to an angle in the range of 45 ° ± 5 °, preferably 42 to 48 °, and more preferably 43 to 47 °.

The orientation average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a material of the liquid crystal compound or the alignment film or by selecting a rubbing treatment method.
In the present invention, for example, in the case of producing an optical compensation film for the OCB method, an alignment film for forming an optically anisotropic layer is produced by rubbing treatment, and in the direction of 45 ° with respect to the slow axis of the cellulose acylate film. By rubbing, an optically anisotropic layer in which the orientation average direction of the molecular symmetry axis of the liquid crystalline compound at least at the cellulose acylate film interface is 45 ° with respect to the slow axis of the cellulose acylate film is formed. be able to.
For example, the optical compensation film can be continuously produced by using the long cellulose acylate film of the present invention in which the slow axis is perpendicular to the longitudinal direction. Specifically, a coating solution for forming an alignment film is continuously applied to the surface of the long cellulose acylate film to prepare a film, and then the surface of the film is continuously 45 ° in the longitudinal direction. Then, an alignment film is produced by rubbing in the direction of, and an optically anisotropic layer-forming coating solution containing a liquid crystalline compound is continuously applied on the prepared alignment film, and the molecules of the liquid crystalline compound are dispersed. By aligning and fixing in that state, an optically anisotropic layer can be produced, and a long optical compensation film can be produced continuously. The optical compensation film produced in a long shape is cut into a desired shape before being incorporated into the liquid crystal display device.

  In addition, with respect to the orientation average direction of the molecular symmetry axis on the surface side (air side) of the liquid crystalline compound, the orientation average direction of the molecular symmetry axis of the liquid crystalline compound on the air interface side is relative to the slow axis of the cellulose acylate film. It is preferably about 45 °, more preferably 42 to 48 °, and even more preferably 43 to 47 °. In general, the orientation average direction of the molecular symmetry axis of the liquid crystal compound on the air interface side can be adjusted by selecting the type of the liquid crystal compound or the additive used together with the liquid crystal compound. Examples of the additive used together with the liquid crystal compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. Similarly to the above, the degree of change in the orientation direction of the molecular symmetry axis can be adjusted by selecting the liquid crystal compound and the additive. In particular, regarding the surfactant, it is preferable that the surface tension control of the coating solution is compatible.

The plasticizer, surfactant and polymerizable monomer used together with the liquid crystal compound are compatible with the discotic liquid crystal compound and may change the tilt angle of the liquid crystal compound or do not inhibit the alignment. preferable. A polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferred. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the liquid crystal compound. In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, the adhesion between the alignment film and the optically anisotropic layer can be improved.

When a discotic liquid crystalline compound is used as the liquid crystalline compound, it is preferable to use a polymer that has a certain degree of compatibility with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound.
A cellulose ester can be mentioned as an example of a polymer. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass with respect to the discotic liquid crystalline compound so as not to inhibit the orientation of the discotic liquid crystalline compound, and 0.1 to 8% by mass. More preferably, it is in the range of 0.1 to 5% by mass.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

  In the present invention, Re (550) of the optically anisotropic layer is preferably 0 to 300 nm, more preferably 0 to 200 nm, and further preferably 0 to 100 nm. Rth (550) in the film thickness direction of the optically anisotropic layer is preferably 20 to 400 nm, and more preferably 50 to 200 nm. The thickness of the optically anisotropic layer is preferably 0.1 to 20 microns, more preferably 0.5 to 15 microns, and most preferably 1 to 10 microns.

Moreover, it is preferable that the cellulose acylate film of the present invention satisfies the following formulas (I) to (III).
Formula (I): 0.4 <{(Re (450) / Rth (450)) / (Re (550) / Rth (550))} <0.95
And 1.05 <{(Re (650) / Rth (650)) / (Re (550) / Rth (550))} <1.9.
Formula (II): 0.1 <(Re (450) / Re (550)) <0.95
Formula (III): 1.03 <(Re (650) / Re (550)) <1.93
More preferably,
Formula (I): 0.5 <[(Re (450) / Rth (450)) / (Re (550) / R
th (550))] <0.9
And 1.1 <{(Re (650) / Rth (650)) / (Re (550) / Rth (550))} <1.7
Formula (II): 0.2 <(Re (450) / Re (550)) <0.9
Formula (III): 1.1 <(Re (650) / Re (550)) <1.7
It is.
[Wherein, Re (λ) is the front retardation Re (unit: nm) at a wavelength λnm, and Rth (λ) is the retardation Rth (unit: nm) in the film thickness direction at a wavelength λnm. ]

The reason why such a range of optical performance is preferable will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a general VA mode liquid crystal display device. The VA mode liquid crystal display device includes a liquid crystal cell 3 having a liquid crystal layer in which the liquid crystal is vertically aligned with respect to the substrate surface when no voltage is applied, that is, black display, the liquid crystal cell 3 interposed therebetween, and mutual transmission axes. The polarizing plate 1 and the polarizing plate 2 are disposed so that the directions (shown by stripes in FIG. 1) are orthogonal to each other. In FIG. 1, light enters from the polarizing plate 1 side. When light traveling in the normal direction, that is, the z-axis direction is incident when no voltage is applied, the light that has passed through the polarizing plate 1 passes through the liquid crystal cell 3 while maintaining the linearly polarized state. Completely shaded. As a result, an image with high contrast can be displayed.

  However, as shown in FIG. 2, the situation is different in the case of oblique light incidence. When light is incident from an oblique direction that is not the z-axis direction, that is, an oblique direction with respect to the polarization direction of the polarizing plates 1 and 2 (so-called OFF AXIS), the incident light passes through the vertically aligned liquid crystal layer of the liquid crystal cell 3. When passing, the polarization state changes due to the influence of the oblique retardation. Furthermore, the apparent transmission axes of the polarizing plate 1 and the polarizing plate 2 deviate from the orthogonal arrangement. Due to these two factors, the incident light from the oblique direction in OFF AXIS is not completely shielded by the polarizing plate 2, and light leakage occurs during black display, resulting in a decrease in contrast.

  Here, polar angle and azimuth angle are defined. The polar angle is the normal direction of the film surface, that is, the inclination angle from the z-axis in FIGS. 1 and 2. For example, the normal direction of the film surface is the direction of polar angle = 0 degrees. The azimuth angle represents an azimuth rotated counterclockwise with respect to the positive direction of the x-axis. For example, the positive direction of the x-axis is the direction of the azimuth angle = 0 degrees, and the positive direction of the y-axis is Azimuth angle = 90 degrees. The diagonal direction in OFF AXIS described above mainly refers to the case where the polar angle is not 0 degree and the azimuth angle is 45 degrees, 135 degrees, 225 degrees, and 315 degrees.

In FIG. 3, the schematic diagram about the structural example for demonstrating the effect | action of this invention is shown. The configuration of FIG. 3 is a configuration in which an optical compensation film 4 is disposed between the liquid crystal cell 3 and the polarizing plate 1 in the configuration of FIG. The optical compensation film 4 is an optical film that satisfies the following relationships (I) to (III).
Formula (I): 0.4 <{(Re (450) / Rth (450)) / (Re (550) / Rth (550))} <0.95
And 1.05 <{(Re (650) / Rth (650)) / (Re (550) / Rth (550))} <1.9.
Formula (II): 0.1 <(Re (450) / Re (550)) <0.95
Formula (III): 1.03 <(Re (650) / Re (550)) <1.93
In the present invention, by using an optical compensation film having the above optical characteristics, optical compensation of R, G, and B wavelengths incident in an oblique direction is performed with a different slow axis and retardation for each wavelength. Is possible. As a result, as compared with the conventional liquid crystal display device, the viewing angle contrast of the black display is remarkably improved, and the coloring in the viewing angle direction of the black display is further reduced. Here, in this specification, as wavelengths of R, G, and B, R has a wavelength of 650 nm, G has a wavelength of 550 nm, and B has a wavelength of 450 nm. The wavelengths of R, G, and B are not necessarily represented by these wavelengths, but are considered to be suitable wavelengths for defining the optical characteristics that exhibit the effects of the present invention.

In particular, the present invention focuses on Re / Rth, which is the ratio of Re to Rth. This is because the Re / Rth value determines the two intrinsic polarization axes in the propagation of light traveling obliquely through the biaxial birefringent medium. FIG. 4 shows an example of the result of calculating the relationship between Re / Rth and the direction of one axis of two intrinsic polarizations when light traveling in an oblique direction is incident on the optical compensation film used in the present invention. The light propagation direction was assumed to be azimuth = 45 degrees and polar angle = 34 degrees. From the results shown in FIG. 4, it can be seen that if Re / Rth is determined, one axis of intrinsic polarization is determined. How the polarization state of incident light changes by passing through the optical compensation film is mainly determined by the in-plane slow axis direction of the optical compensation film and the retardation of the optical compensation film. In the present invention, by defining the Re / Rth relationship for each of the R, G, and B wavelengths, both the in-plane slow axis and the retardation, which are factors that mainly determine the change in the polarization state, are R, Optimized for G and B wavelengths. As a result, light is incident from an oblique direction, affected by the retardation in the oblique direction of the liquid crystal layer, and there are two factors, that is, the apparent transmission axes of the polarizing plate 1 and the polarizing plate 2 are deviated. However, complete compensation by one optical compensation film is possible, and reduction in contrast is reduced. If the parameters of the film are determined with R, G, and B representing the entire visible light region, almost complete compensation can be achieved in the entire visible light region.

  In the VA mode, since the liquid crystal is vertically aligned when no voltage is applied, that is, when displaying black, the polarization state of light incident from the normal direction is not affected by the retardation of the optical compensation film 4 when displaying black. As described above, the in-plane slow axis of the optical compensation film 4 is preferably perpendicular or parallel to the polarizing plate 1 or the polarizing plate 2. An optical compensation film may be disposed between the polarizing plate 2 and the liquid crystal cell 3, and in this case, the in-plane slow axis of the optical compensation film is made perpendicular or parallel to the polarizing plate 1 or the polarizing plate 2. Is preferred.

  FIG. 5 is a diagram illustrating the compensation mechanism in the configuration of FIG. 3 using a Poincare sphere. Here, the propagation directions of light are azimuth = 45 degrees and polar angle = 34 degrees. In FIG. 5, the S2 axis is an axis that penetrates vertically from the top to the bottom of the page, and FIG. 5 is a view of the Poincare sphere viewed from the positive direction of the S2 axis. Further, since FIG. 5 is shown in a plan view, the displacement of the point before and after the change of the polarization state is indicated by a straight arrow in the figure. The change in the polarization state due to the passage is expressed by rotating a specific angle on a Poincare sphere around a specific axis determined according to each optical characteristic.

  The polarization state of the incident light that has passed through the polarizing plate 1 in FIG. 3 corresponds to the point (i) in FIG. 5, and the polarization state shielded by the absorption axis of the polarizing plate 2 in FIG. Corresponds to (ii). Conventionally, in the VA mode liquid crystal display device, the light leakage of OFF AXIS in the oblique direction is caused by the deviation of the point (i) and the point (ii). The optical compensation film is generally used for changing the polarization state of incident light from the point (i) to the point (ii) including the change of the polarization state in the liquid crystal layer. Since the liquid crystal layer of the liquid crystal cell 3 exhibits positive refractive index anisotropy and is vertically aligned, the change in the polarization state of incident light due to passing through the liquid crystal layer is the top in FIG. 5 on the Poincare sphere. Indicated by a downward arrow from, and expressed as rotation about the S1 axis. Therefore, in order for the visible light after passing through the liquid crystal layer to be completely shielded by the polarizing plate 2, the starting point before rotation is the point (ii) rotated around the S1 axis for each of R, G, and B. It must be on the line. Further, the rotation angle is proportional to the value Δn′d ′ / λ obtained by dividing the effective retardation Δn′d ′ from the oblique direction of the liquid crystal layer by the wavelength, so that each of R, G, and B having different wavelengths is obtained. At the wavelength, the rotation angles do not match. Therefore, in order for all the polarization states of R, G, and B to be point (ii) after rotation, as shown in FIG. 5, the polarization states of R, G, and B before rotation are the points (ii). ) On the line rotated around the S1 axis, and at a point corresponding to each rotation angle. In the present invention, in order to change the polarization states of R, G, and B after passing through the optical compensation film 4 and before passing through the liquid crystal cell 3 to the above-described polarization states, Re / Optical compensation is performed by arranging an optical compensation film satisfying a certain relationship of Rth.

  On the other hand, an example of the prior art is similarly shown in FIG. The example shown in FIG. 6 is an example when an optical compensation film having a constant Re / Rth with respect to the wavelength is used. In this case, for example, even if the optical characteristics of the optical compensation film are adjusted so that the starting point before the rotation by the liquid crystal layer is positioned on the line rotated about the S1 axis with respect to the G light, R Light and B light cannot be positioned on such a line. Therefore, the R and B lights that have passed through the liquid crystal layer do not change to the polarization state at the point (ii) and cannot be completely shielded by the absorption axis of the polarizing plate. As a result, light loss of R light and B light occurs, and color misregistration occurs in black display. The same applies when using an optical compensation film optimized for only R light and B light.

The cellulose acylate film preferably used in the present invention can be obtained by forming a film using a solution prepared by dissolving the specific cellulose acylate and, if necessary, an additive in an organic solvent.

〔Additive〕
Examples of the additive that can be used in the cellulose acylate solution in the present invention include a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a retardation (optical anisotropy) developing agent, and a retardation (optical anisotropy). Examples thereof include a reducing agent, a wavelength dispersion adjusting agent, a dye, fine particles, a peeling accelerator, and an infrared absorber. In the present invention, it is preferable to use a retardation developer. Moreover, it is preferable to use at least one of a plasticizer, an ultraviolet absorber and a peeling accelerator.

  They may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, ultraviolet absorbers of 20 ° C. or lower and 20 ° C. or higher can be mixed and used, and plasticizers can also be mixed and used, for example, as described in JP-A-2001-151901.

[Ultraviolet absorber]
As the ultraviolet absorber, any type can be selected according to the purpose, and a salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex-based absorber or the like is used. Preferred are benzophenone series, benzotriazole series, and salicylic acid ester series.

  Examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2′-di-hydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- And methacryloxy) propoxybenzophenone.

  As a benzotriazole ultraviolet absorber, 2 (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-t-butylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-amylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5 Examples include chlorobenzotriazole, 2 (2′-hydroxy-5′-t-octylphenyl) benzotriazole, and the like.

  Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate.

  Among these exemplified ultraviolet absorbers, in particular, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-t-butyl- 5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-t-butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-t-amylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzotriazole is particularly preferred.

As the ultraviolet absorber, it is preferable to use a combination of a plurality of absorbers having different absorption wavelengths because a high blocking effect can be obtained in a wide wavelength range. The ultraviolet absorbent for liquid crystal is preferably one that is excellent in the ability to absorb ultraviolet light having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and that has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Particularly preferred ultraviolet absorbers are the benzotriazole compounds, benzophenone compounds, and salicylic acid ester compounds mentioned above. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose ester is small.

  As for the UV absorber, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-107854. 118233, 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, JP-A-2000-204173 These compounds can also be used.

  0.001-5 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a ultraviolet absorber, 0.01-1 mass% is more preferable. If the addition amount is 0.001% by mass or more, the effect of addition can be sufficiently exerted, and if the addition amount is 5% by mass or less, it is preferable because bleeding out of the ultraviolet absorber to the film surface can be suppressed.

  Further, the ultraviolet absorber may be added simultaneously with dissolution of cellulose acylate, or may be added to the dope after dissolution. In particular, a mode in which an ultraviolet absorbent solution is added to the dope immediately before casting using a static mixer or the like is preferable because spectral absorption characteristics can be easily adjusted.

[Deterioration inhibitor]
The deterioration inhibitor can prevent cellulose triacetate and the like from deteriorating and decomposing. Examples of the deterioration preventing agent include butylamine, hindered amine compounds (JP-A-8-325537), guanidine compounds (JP-A-5-271471), benzotriazole-based UV absorbers (JP-A-6-235819), and benzophenone-based compounds. There are compounds such as UV absorbers (JP-A-6-118233).

[Plasticizer]
The plasticizer is preferably a phosphate ester or a carboxylic acid ester. Examples of the phosphate ester plasticizer include triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate (BDP), trioctyl phosphate, tributyl phosphate and the like; Examples of the acid ester plasticizer include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), diethyl hexyl phthalate (DEHP), O-acetyl citrate. Triethyl acid (OACTE), O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate, oleic acid , Methyl ricinoleate, dibutyl sebacate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. The plasticizer used in the invention is more preferably selected from these exemplified plasticizers. Furthermore, the plasticizer is preferably (di) pentaerythritol esters, glycerol esters, diglycerol esters.

[Peeling accelerator]
Examples of the peeling accelerator include citric acid ethyl esters.
[Infrared absorber]
Furthermore, as an infrared absorber, it describes in Unexamined-Japanese-Patent No. 2001-194522, for example.

[Additional time]
These additives may be added at any time in the dope preparation step, but may be added to the final preparation step of the dope preparation step by adding the additive preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  Moreover, when a cellulose acylate film is a multilayer, the kind and addition amount of the additive of each layer may differ. For example, although described in Japanese Patent Application Laid-Open No. 2001-151902, these are conventionally known techniques.

  The glass transition point Tg measured by a dynamic viscoelasticity measuring device “Vibron: DVA-225” {manufactured by IT Measurement Control Co., Ltd.}} of a cellulose acylate film is selected by selecting the type and amount of these additives. It is preferable that the elastic modulus measured by a tensile tester “Strograph-R2” {manufactured by Toyo Seiki Seisakusho} is 1500 to 4000 MPa at ˜150 ° C. More preferably, the glass transition point Tg is 80 to 135 ° C. and the elastic modulus is 1500 to 3000 MPa. That is, the cellulose acylate film preferably used in the present invention preferably has a glass transition point Tg and an elastic modulus within the above ranges from the viewpoint of process suitability for polarizing plate processing and liquid crystal display device assembly.

  Furthermore, regarding the additive, the Japan Society of Invention and Innovation Technical Bulletin No. 2001-1745 (issued March 15, 2001, Japan Society of Invention) p. Those described in detail after 16 can be used as appropriate.

[Retardation reducing agent]
The retardation reducing agent used for reducing the optical anisotropy of the cellulose acylate film will be described.
Using a compound that suppresses the orientation of cellulose acylate in the film in the plane and in the film thickness direction, the optical anisotropy is sufficiently reduced, and Re and Rth can be made zero or close to zero. it can. For this purpose, it is advantageous that the compound that lowers the optical anisotropy is sufficiently compatible with cellulose acylate, and the compound itself does not have a rod-like structure or a planar structure. Specifically, when a plurality of planar functional groups such as aromatic groups are provided, a structure having these functional groups in a non-planar rather than the same plane is advantageous.

(Log P value)
In producing a cellulose acylate film having a low optical anisotropy, as described above, the cellulose anion in the film is prevented from being oriented in the plane and in the film thickness direction, thereby reducing the optical anisotropy. Of the compounds, compounds having an octanol-water partition coefficient (log P value) of 0 to 7 are preferred. If the log P value of the compound is 7 or less, the compatibility with the cellulose acylate is good, and problems such as white turbidity and powder blowing of the film are less likely to occur.
Moreover, if the logP value of the compound is 0 or more, the hydrophilicity does not become too high and the water resistance of the cellulose acylate film is not deteriorated, which is preferable. A more preferable range for the logP value is 1 to 6, and a particularly preferable range is 1.5 to 5.

  The octanol-water partition coefficient (log P value) can be measured by a flask soaking method described in JIS Z-7260-107 (2000). Further, the octanol-water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement.

As a calculation method, Crippen's fragmentation method {“J. Chem. Inf. Comput. Sci.”, 27, p21 (1987)}, Visw
anadhan's fragmentation method {"J. Chem. Inf. Comput. Sci.", 29, p163 (1989)}, Broto's fragmentation method {"Eur. J. Med. Chem.-Chim. Theor." 19 and p71 (1984)} are preferably used, but the Crippen's fragmentation method {"J. Chem. Inf. Comput. Sci.", 27, p21 (1987)} is more preferable.

  When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the above range by the Crippen's fragmentation method.

(Physical properties of compounds that reduce optical anisotropy)
The compound that reduces optical anisotropy may or may not contain an aromatic group. The compound that reduces the optical anisotropy preferably has a molecular weight of 150 or more and 3000 or less, preferably 170 or more and 2000 or less, and particularly preferably 200 or more and 1000 or less. A specific monomer structure may be used as long as these molecular weights are within the range, and an oligomer structure or a polymer structure in which a plurality of the monomer units are bonded may be used.

  The compound that reduces optical anisotropy is preferably liquid at 25 ° C. or a solid having a melting point of 25 to 250 ° C., more preferably liquid at 25 ° C. or a melting point of 25 to 200 ° C. It is a solid. Moreover, it is preferable that the compound which reduces optical anisotropy does not volatilize in the process of dope casting for cellulose acylate film production and drying.

  The addition amount of the compound that decreases the optical anisotropy is preferably 0.01 to 30% by mass of the cellulose acylate, more preferably 1 to 25% by mass, and 5 to 20% by mass. Is particularly preferred.

  The compound that decreases the optical anisotropy may be used alone, or two or more compounds may be mixed and used in an arbitrary ratio.

  The timing for adding the compound that decreases the optical anisotropy may be any time during the dope preparation process, or may be performed at the end of the dope preparation process.

  The compound that reduces the optical anisotropy is such that the average content of the compound in the portion from the surface on at least one side to 10% of the total film thickness is the average content of the compound in the central portion of the cellulose acylate film. It is preferable that it is 80 to 99% of. The amount of the compound that reduces the optical anisotropy can be determined by measuring the amount of the compound at the surface and in the central portion, for example, by a method using an infrared absorption spectrum described in JP-A-8-57879. .

[dye]
In the present invention, a dye for adjusting the hue may be added. The content of the dye is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm in terms of a mass ratio with respect to cellulose acylate. By containing the dye in this way, light piping of the cellulose acylate film can be reduced, and yellowness can be improved. These compounds may be added together with cellulose acylate and a solvent during the preparation of the cellulose acylate solution, or may be added during or after the solution preparation. Moreover, you may add to the ultraviolet absorber liquid added in-line. The dyes described in JP-A-5-34858 can be used.

[Matting agent fine particles]
It is preferable to add fine particles as a matting agent to the cellulose acylate film preferably used in 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, magnesium silicate and Mention may be made of calcium phosphate. As the fine particles, those containing silicon are preferable in terms 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 / L 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 / L or more, and more preferably 100 to 200 g / L or more. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  When silicon dioxide fine particles are used as the matting agent, the amount used is preferably 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the polymer component containing cellulose acylate.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, but are present as aggregates of primary particles in the film, and 0.1 to 3.0 μm on the film surface. Form irregularities. The average particle diameter of the secondary particles is preferably from 0.2 μm to 1.5 μm, more preferably from 0.4 μm to 1.2 μm, and most preferably from 0.6 μm to 1.1 μm. If the average particle diameter is 1.5 μm or less, the haze will not be too strong, and if it is 0.2 μm or more, the effect of preventing squeezing will be sufficiently exhibited, which is preferable.

  The primary and secondary particle diameters of the fine particles are determined by observing the particles in the film with a scanning electron microscope and using the diameter of a circle circumscribing the particles as the particle diameter. Also, 200 particles are observed at different locations, and the average value is taken as the average particle diameter.

  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, manufactured by Nippon Aerosil Co., Ltd.} can be used. . Zirconium oxide fine particles are commercially available under the trade names of “Aerosil” R976 and R811 {above, 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 / L or more, and low turbidity of the optical film. This is particularly preferable because the effect of reducing the coefficient of friction is large while maintaining it.

In the present invention, in order to obtain a cellulose acylate film containing particles having a small secondary average particle size, several methods are conceivable when preparing a dispersion of fine particles. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared cellulose acylate solution, dissolved by stirring, and further mixed with the main cellulose acylate dope solution. There is a way. This method is a preferable preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add the fine particles to this and disperse with a disperser to make this fine particle additive solution, and mix this fine particle additive solution with the dope solution using an in-line mixer. There is also a way to do it. In the present invention, although not limited to these methods, the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, and 10 to 25% by mass. Is more preferable, and 15 to 20% by mass is most preferable.
A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved. The addition amount of the matting agent in the final cellulose acylate dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and 0.08 to 0.16 g per 1 m ^2. Most preferred.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  Next, the organic solvent in which cellulose acylate preferably used in the present invention is dissolved will be described.

  In the present invention, as the organic solvent, any of a chlorinated solvent containing a chlorinated organic solvent as a main solvent and a non-chlorinated solvent not containing a chlorinated organic solvent can be used.

[Chlorine solvent]
In preparing the cellulose acylate solution preferably used in 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 as long as the cellulose acylate is dissolved and can be cast and formed into a film. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. 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 dichloromethane in the total amount of the organic solvent.

Other organic solvents used in combination with the chlorinated organic solvent in the present invention will be described below.
That is, as another preferable organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. 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. For example, other compounds such as alcoholic hydroxyl groups can be used. You may have a functional 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 preferably 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, t-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. In addition, hydrocarbons
It 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.

Examples of combinations of chlorinated organic solvents and other organic solvents include the following compositions, but are not limited thereto.
Dichloromethane / methanol / ethanol / butanol = 80/10/5/5 (parts by mass)
Dichloromethane / acetone / methanol / propanol = 80/10/5/5 (parts by mass)
Dichloromethane / methanol / butanol / cyclohexane = 80/10/5/5 (parts by mass)
Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/10/5/5 (parts by mass)
Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol = 75/8/5/5/7 (parts by mass)
Dichloromethane / cyclopentanone / methanol / isopropanol = 80/7/5/8 (parts by mass)
Dichloromethane / methyl acetate / butanol = 80/10/10 (parts by mass)
Dichloromethane / cyclohexanone / methanol / hexane = 70/20/5/5 (parts by mass),
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol = 50/20/20/5/5 (parts by mass),
Dichloromethane / 1, 3 dioxolane / methanol / ethanol = 70/20/5/5 (parts by mass),
Dichloromethane / dioxane / acetone / methanol / ethanol = 60/20/10/5/5 (parts by mass),
Dichloromethane / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane = 65/10/10/5/5/5 (parts by mass)
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol = 70/10/10/5/5 (parts by mass),
Dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane = 65/10/10/5/5/5 (parts by mass)
Dichloromethane / methyl acetoacetate / methanol / ethanol = 65/20/10/5 (parts by mass),
Dichloromethane / cyclopentanone / ethanol / butanol = 65/20/10/5 (parts by mass).

[Non-chlorine solvents]
Next, a non-chlorine organic solvent that is preferably used in preparing a cellulose acylate solution that is preferably used in 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 is dissolved and can be 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. It may have a functional group of 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, methylcyclohexanone and methyl acetyl acetate. 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 above-mentioned non-chlorine organic solvent used for cellulose acylate is selected from the various viewpoints described above, and is preferably as follows.
That is, the non-chlorine solvent is preferably a mixed solvent containing the non-chlorine organic solvent as a main solvent, and is a mixed solvent of three or more different solvents, wherein the first solvent is methyl acetate, ethyl acetate, At least one selected from methyl formate, ethyl formate, acetone, dioxolane, and dioxane, or a mixture thereof, wherein the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, The solvent is a mixed solvent selected from alcohols or hydrocarbons having 1 to 10 carbon atoms, more preferably alcohols 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, methyl acetyl acetate, or a mixture thereof. It may be a solvent.

  The alcohol as the third solvent may have a hydrocarbon chain that is linear, branched, or cyclic, and among them, a saturated aliphatic hydrocarbon chain 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, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. In addition, as the alcohol, a fluorine-based alcohol in which part or all of the hydrogen in the hydrocarbon chain is substituted with fluorine 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 in 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, and hydrocarbons such as cyclohexane and hexane. Particularly preferred are methanol, ethanol, 1-propanol, 2-propanol and 1-butanol.

The mixing ratio of the above three kinds of mixed solvents is that the first solvent is 20 to 95% by mass, the second solvent is 2 to 60% by mass, and the third solvent is 2 to 30% by mass in the total amount of the mixed solvent. %, Preferably the first solvent is 30 to 90% by mass, the second solvent is 3 to 50% by mass, and the third alcohol is 3 to 25% by mass. preferable. In particular, the first solvent is preferably 30 to 90% by mass, the second solvent is preferably 3 to 30% by mass, and the third solvent is an alcohol, and preferably 3 to 15% by mass.

  The non-chlorine-based organic solvent used in the present invention described above is more specifically described in JIII Journal of Technical Disclosure No. 2001-1745 (issued March 15, 2001, Invention Association) p. 12-16.

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 (parts 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 (parts 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 solution prepared by the following method can also be used.
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol / butanol = 81/8/7/4 (parts by mass), adding 2 parts by mass of butanol after filtration and concentration,
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol / butanol = 84/10/4/2 (parts by mass), adding 4 parts by mass of butanol after filtration and concentration,
A method of preparing a cellulose acylate solution with methyl acetate / acetone / ethanol = 84/10/6 (parts by mass), adding 5 parts by mass of butanol after filtration and concentration,

  In addition to the non-chlorine organic solvent of the present invention, the dope used in the present invention may contain dichloromethane in an amount of 10% by mass or less based on the total amount of the organic solvent of the present invention.

[Characteristics of cellulose acylate solution]
The cellulose acylate solution is a solution in which cellulose acylate is dissolved in the organic solvent, and the concentration thereof is preferably in the range of 10 to 30% by mass from the viewpoint of film-forming casting suitability, more preferably. It is 13-27 mass%, Most preferably, it is 15-25 mass%.
A method for bringing the cellulose acylate solution into such a concentration range may be a predetermined concentration at the stage of dissolution, and will be described later after it is prepared in advance as a low concentration solution (for example, 9 to 14% by mass). You may adjust to a predetermined high concentration solution by a concentration process. Furthermore, after preparing a high concentration cellulose acylate solution in advance, various additives may be added to obtain a predetermined low concentration cellulose acylate solution, and any method is preferably used in the present invention. There is no particular problem if it is carried out so as to have a concentration.

Next, in the present invention, when the cellulose acylate solution is made 0.1 to 5% by mass with an organic solvent having the same composition, the aggregate molecular weight of the cellulose acylate in the diluted solution is 150,000 to 15 million. Is preferable from the viewpoint of solubility in a solvent. The associated molecular weight is more preferably 180,000 to 9 million. This associated molecular weight can be determined by a static light scattering method. In that case, it is preferable to melt | dissolve so that the inertial radius calculated | required simultaneously may be 10-200 nm. A more preferable radius of inertia 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, the definition of the associated molecular weight, the radius of inertia, and the second virial coefficient in the present invention will be described. These are measured using the static light scattering method according to the following method. Although the measurement is 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 solutions of 0.1 mass%, 0.2 mass%, 0.3 mass%, and 0.4 mass%. In order to prevent moisture absorption, the cellulose acylate is dried at 120 ° C. for 2 hours, and is 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 solutions and the solvent are filtered through a 0.2 μm Teflon filter. Then, static light scattering of the filtered solution is measured at 10 ° intervals from 30 ° to 140 ° 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. The refractive index necessary for this analysis is the value of the solvent determined by the Abbe refractive system, and the refractive index concentration gradient (dn / dc) is a differential refractometer “DRM-1021” {manufactured by Otsuka Electronics Co., Ltd. }, And using the solvent and solution used for the light scattering measurement.

[Preparation of dope]
Next, preparation of a solution (dope) for casting and film formation of cellulose acylate will be described.
The method for dissolving cellulose acylate is not particularly limited, and may be a room temperature dissolution method, 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-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, Special JP-A-2000-273184, JP-A-11-323017, JP-A-11-302388, and the like describe the methods for preparing a cellulose acylate solution.

  The above-described method for dissolving cellulose acylate in an organic solvent can be applied to the present invention even within the scope of the present invention. For details on these, especially non-chlorine solvent systems, the Japan Society for Invention and Innovation, Publication No. 2001-1745 (issued March 15, 2001, Japan Society for Invention) p. 22-25, which can be carried out according to that method. Further, the cellulose acylate dope solution preferably used in the present invention is usually subjected to solution concentration and filtration, and these are similarly applied to the Japan Institute of Invention and Technology Publication No. 2001-1745 (March 2001). Issued on the 15th, Invention Association) p. 25 in detail. 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 carries out in a pressurized state.

It is preferable that the cellulose acylate solution has a viscosity and a dynamic storage elastic modulus within the ranges described below because it is easy to cast. These values are measured using 1 mL of the sample solution in a rheometer “CLS 500” and “Steel Cone” (both manufactured by TA Instruments) having a diameter of 4 cm / 2 °. Measurement conditions were measured by varying the range from 40 ° C. to −10 ° C. at 2 ° C./min using Oscillation Step / Temperature Ramp, and static non-Newtonian viscosity n ^* (Pa · s) at 40 ° C. and storage at −5 ° C. The elastic modulus G ′ (Pa) is obtained. Note that the sample solution is preliminarily kept at the measurement start temperature until the liquid temperature becomes constant, and then the measurement is started.

  In the present invention, the viscosity at 40 ° C. is 1 to 400 Pa · s, the dynamic storage elastic modulus at 15 ° C. is preferably 500 Pa or more, and more preferably the viscosity at 40 ° C. is 10 to 200 Pa · s. Therefore, the dynamic storage elastic modulus at 15 ° C. should be 100 to 1,000,000. Furthermore, the dynamic storage elastic modulus at low temperature is preferably as large as possible. For example, when the casting support is −5 ° C., the dynamic storage elastic modulus is preferably 10,000 to 1,000,000 Pa at −5 ° C. When the support is at −50 ° C., the dynamic storage elastic modulus at −50 ° C. is preferably 10,000 to 5 million Pa.

In the present invention, since the above-mentioned specific cellulose acylate is used, it is characterized in that a high concentration dope can be obtained. A cellulose acylate having a high concentration and excellent stability can be obtained without resorting to a means of concentration. A rate solution is obtained. Further, in order to facilitate dissolution, it may be concentrated using a concentration means after being dissolved at a low concentration. The concentration method is not particularly limited. For example, the low-concentration solution is guided between the cylindrical body and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and the temperature between the solution and the solution. A method of giving a difference and obtaining a high-concentration solution while evaporating the solvent (for example, JP-A-4-259511), until a heated low-concentration solution is blown into the container from the nozzle until the solution hits the inner wall of the container from the nozzle The solvent is flash evaporated between the container and the solvent vapor is withdrawn from the container and the concentrated solution is withdrawn from the container bottom (eg, US Pat. No. 2,541,012, US Pat. No. 2,858,229, US The method described in Japanese Patent No. 4,414,341, US Pat. No. 4,504,355, etc.) and the like.

  Prior to casting, the dope solution is preferably filtered off foreign matters such as undissolved matter, dust, and impurities using an appropriate filter medium such as a wire mesh or flannel. For filtration of the cellulose acylate solution, it is preferable to use a filter having an absolute filtration accuracy of 0.1 to 100 μm, and it is more preferable to use a filter having an absolute filtration accuracy of 0.5 to 25 μm. 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. The viscosity of the cellulose acylate solution immediately before film formation may be in a range that can be cast during film formation, and is usually prepared in a range of 10 Pa · s to 2000 Pa · s, preferably 30 Pa · s to 1000 Pa. · S is more preferable, and 40 Pa · s to 500 Pa · s is more preferable. The temperature at this time is not particularly limited as long as it is a temperature at the time of casting, but is preferably −5 to + 70 ° C., more preferably −5 to + 55 ° C.

[Film formation]
The cellulose acylate film preferably used in the present invention can be obtained by forming a film using the cellulose acylate solution (dope). As the film forming method and equipment, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is once stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressurizing die through a pressurizing quantitative gear pump capable of feeding the dope with high accuracy by the number of rotations, for example, and the dope is run endlessly from the die (slit) of the pressurizing die The dope film (also referred to as a web) is peeled off from the metal support at a peeling point where the metal support is almost cast around the metal support. The both ends of the obtained web are sandwiched between clips, transported by a tenter while maintaining the width, dried, and then transported by a roll group of a drying device to finish drying, and wound to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for the functional protective film for electronic displays, in addition to the solution casting film forming apparatus, surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. Therefore, a coating device is often added. Although each manufacturing process is described briefly below, it is not limited to these.

  In producing a cellulose acylate film by the solvent cast method, first, the prepared cellulose acylate solution (dope) is cast on a drum or a band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting 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. For the dope, a method of casting on a drum or band having a surface temperature of 30 ° C. or less is preferably employed, and the metal support temperature is particularly preferably in the range of −10 to 20 ° C. Further, in the present invention, JP 2000-301555 A, JP 2000-301558 A, JP 07-032391, JP 03-193316, JP 05-086212, JP 62-037113, JP The methods described in JP-A Nos. 02-276607, 55-014201, 02-111511, and 02-208650 can be used.

[Multilayer casting]
The cellulose acylate solution may be cast as a single layer liquid on a smooth band or a drum as a metal support, or a plurality of cellulose acylate liquids of two or more layers may be cast. When casting a plurality of cellulose acylate solutions, a solution containing cellulose acylate is cast from a plurality of casting openings provided at intervals in the traveling direction of the metal support, and the films are laminated while being laminated. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be applied. A film can also be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Further, the cellulose described in JP-A-56-162617, a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution, and the high-viscosity and low-viscosity cellulose acylate solutions are simultaneously extruded. An acylate film casting method may be used. Furthermore, as described in JP-A-61-94724 and JP-A-61-94725, it is also preferable that the outer solution contains a larger amount of an alcohol component that is a poor solvent than the inner solution. . Alternatively, two casting ports are used, and after the film formed on the metal support is peeled off by the first casting port, the second casting is performed on the side of the film that is in contact with the metal support surface. Thus, a film having a plurality of layers can also be produced, and examples thereof include a method described in Japanese Patent Publication No. 44-20235. The cellulose acylate solution to be cast may be the same solution or different cellulose acylate solutions, and is not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Further, the cellulose acylate 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 absorption layer, and a polarizing layer).

  In the conventional single-layer solution, in order to obtain the required film thickness, it is necessary to extrude a high-concentration and high-viscosity cellulose acylate solution, in which case the stability of the cellulose acylate solution tends to deteriorate. In many cases, a solid matter is generated, resulting in a failure or flatness. As a solution to this, by casting a plurality of cellulose acylate solutions from a plurality of casting ports relatively little by little, it becomes possible to extrude a highly viscous solution onto a metal support at the same time. In addition to producing an excellent planar film with improved properties, the use of a concentrated cellulose acylate solution can achieve a reduction in drying load and increase the production speed of the film.

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 of three or more layers, the total film 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 cellulose acylate film having a laminated structure can be produced by co-casting cellulose acylate solutions having different additive concentrations such as the plasticizer, ultraviolet absorber, and matting agent. For example, a cellulose acylate 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. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. It is also possible to change the type of plasticizer and ultraviolet absorber between the core layer and the skin layer. For example, the skin layer contains at least one of a low-volatile plasticizer and an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Furthermore, it is also a preferred embodiment that a peeling accelerator is contained only in the skin layer on the metal support side. Furthermore, 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 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 solution containing cellulose acylate 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. It may be smaller than the viscosity of the layer.

[Casting method]
As a solution casting method, a method in which the prepared dope is uniformly extruded from a pressure die onto a metal support, and a method using a doctor blade in which the dope once cast on the metal support is adjusted with a blade is used. Although there is a method using a reverse roll coater that adjusts with a reverse rotating roll, 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 mentioned here, it can be carried out by various known methods for casting a cellulose triacetate solution, and each condition is set in consideration of differences in the boiling point of the solvent used. Thus, the same effects as those described in the respective publications can be obtained.

  The endlessly running metal support used for producing the cellulose acylate film preferably used in the present invention includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt whose surface is mirror-finished by surface polishing ( May be referred to as a band). One or more pressure dies may be installed above the metal support. Preferably 1 or 2 groups. When two or more are installed, the amount of dope 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 cellulose acylate solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all solution temperatures in the process may be the same or different at different points in the process. If they are different, the temperature may be a desired temperature just before casting.

[Dry]
The dope drying on the metal support involved in the production of the cellulose acylate film is generally applied with hot air from the surface side of the metal support (drum or belt), that is, the surface of the web on the metal support. Method, method of applying hot air from the back of the drum or belt, contact the temperature-controlled liquid from the back of the belt or drum opposite the dope casting surface, and heat the drum or belt by heat transfer to control the surface temperature There is a back surface liquid heat transfer method, and the back surface 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 ° C. lower than the boiling point of the lowest boiling solvent used. Is preferred. This is not the case when the cast dope is cooled and peeled off without drying.

  In order to suppress light leakage when the polarizing plate is viewed obliquely, it is necessary to arrange the transmission axis of the polarizer and the in-plane slow axis of the cellulose acylate film in parallel. Since the transmission axis of the roll film-like polarizer produced continuously is generally parallel to the width direction of the roll film, it is composed of the roll film-like polarizer and the roll film-like cellulose acylate film. In order to continuously bond the protective film, the in-plane slow axis of the roll film-shaped protective film needs to be parallel to the width direction of the film. The stretching process may be performed in the middle of the film forming process, or the original fabric that has been formed and wound may be stretched. In the former case, stretching may be performed in a state containing a residual solvent, and the stretching can be preferably performed at a residual solvent amount of 2 to 30% by mass.

The film thickness of the cellulose acylate film preferably used in the present invention obtained after drying varies depending on the purpose of use, and is usually preferably in the range of 5 to 500 μm, more preferably in the range of 20 to 300 μm, particularly 30 to 30 μm. A range of 150 μm is preferred. Moreover, it is preferable that it is 40-110 micrometers for optical use, especially for VA liquid crystal display devices. 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 cellulose acylate 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 10000 m per roll, more preferably 500 to 7000 m, and still more preferably 1000 to 6000 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

  The variation in the Re (590) value in the width direction of the film is preferably ± 5 nm, and more preferably ± 3 nm. Further, the variation of the Rth (590) value in the width direction 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.

[Optical properties of cellulose acylate film]
The cellulose acylate film suitable for the present invention is used as a protective film for a polarizing plate, and can be preferably used also as a retardation film corresponding to various liquid crystal modes.
When the cellulose acylate film of the present invention is used as a retardation film, preferred optical properties of the cellulose acylate film vary depending on the liquid crystal mode.
For the OCB mode, Re is preferably 10 to 100 nm, more preferably 20 to 70 nm. Rth is preferably 50 to 300 nm, more preferably 100 to 250 nm.
For TN, Re is preferably 0 to 50 nm, more preferably 2 to 30 nm. Rth is preferably 10 to 200 nm, more preferably 30 to 150 nm.
For IPS, Re is preferably 0 to 5 nm, and more preferably 0 to 2 nm. Rth is preferably -20 to 20 nm, more preferably -10 to 10 nm.
In the OCB mode and the TN mode, an optically anisotropic layer can be coated on a cellulose acylate film having the retardation value and used as an optical compensation film.

  In addition, it is preferable that the birefringence ((DELTA) n: nx-ny) of a cellulose acylate film exists in the range of 0.00-0.002 micrometer. The birefringence {(nx + ny) / 2-nz} in the thickness direction of the support film and the counter film is preferably in the range of 0.00 to 0.04 μm.

When the cellulose acylate film preferably used in the present invention is used in the VA mode, it is used only on one of the upper and lower sides of the cell (two-sheet type) in which two sheets are used on both sides of the cell. There are two types of forms (single sheet type).
In the case of the two-sheet type, Re (590) is preferably 20 to 100 nm, and more preferably 30 to 70 nm. Rth (590) is preferably from 70 to 300 nm, more preferably from 100 to 200 nm.
In the case of a single sheet type, Re (590) is preferably 30 to 150 nm, and more preferably 40 to 100 nm. Rth (590) is preferably from 100 to 300 nm, more preferably from 150 to 250 nm.

The variation of the slow axis angle in the film plane of the cellulose acylate film preferably used in the present invention is preferably in the range of −2 ° to + 2 ° with respect to the reference direction of the roll film, from −1 ° to The range of + 1 ° is more preferable, and the range of −0.5 ° to + 0.5 ° is most preferable. Here, the reference direction is the longitudinal direction of the roll film when the cellulose acylate film is longitudinally stretched, and the width direction of the roll film when laterally stretched.

The cellulose acylate film preferably used in the present invention has a difference ΔRe (= Re _10% ) at 25 ° C. and 10% RH and a Re value (Re _80% ) at 25 ° C. and 80% RH. Re _10% -Re _80% ) is 0 to 10 nm, and the difference ΔRth between the Rth value (Rth _10% ) at 25 ° C. and ₁₀ % RH and the Rth value (Rth _80% ) at 25 ° C. and 80% RH = Rth _10% -Rth _80% ) is preferably from 0 to 30 nm in order to reduce the color change with time of the liquid crystal display device.

Further, the cellulose acylate film preferably used in the present invention has an equilibrium water content of not more than 3.2% at 25 ° C. and 80% RH in order to reduce the color change with time of the liquid crystal display device.
The moisture content was measured by using a cellulose acylate film sample 7 mm × 35 mm, a Karl Fischer method using a moisture measuring device and a sample drying apparatus {“CA-03”, “VA-05”, both Mitsubishi Chemical Corporation)}. Measure with It is calculated by dividing the amount of water (g) by the sample mass (g).

Furthermore, the cellulose acylate film preferably used in the present invention has a moisture permeability of 60 ° C., 95% RH, and 24 hours (in terms of a film thickness of 80 μm) of 400 g / m ² · 24 hr or more and 1800 g / m ² · 24 hr or less. It is preferable to reduce the change in color of the liquid crystal display device over time.

The moisture permeability decreases as the thickness of the cellulose acylate film increases, and increases as the thickness decreases. Therefore, it is necessary to provide and convert a reference film thickness in any film thickness sample. In the present invention, the film thickness was converted according to the following formula (13) with the standard film thickness set to 80 μm.
Formula (13): 80 μm-converted moisture permeability = measured moisture permeability × measured film thickness μm / 80 μm.

  The measurement method of moisture permeability is "Polymer Physical Properties II" (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount method) The method described in can be applied.

  The elastic modulus was measured by adjusting a cellulose acylate film sample 10 mm × 150 mm at 25 ° C. and 60% RH for 2 hours or more, and then a tensile tester “Strograph-R2” {manufactured by Toyo Seiki Seisakusho}} The chucking distance was 100 mm, the temperature was 25 ° C., and the stretching speed was 10 mm / min.

The measurement of the hygroscopic expansion coefficient is a value L _{80% obtained} by measuring the dimension of a film left at 25 ° C. and 80% RH for 2 hours or more with a pin gauge, and the dimension of a film left at 25 ° C. and 10% RH for 2 hours or more. Was obtained by the following formula (14) from the value L _10% measured with a pin gauge.
Formula (14): (L _80% -L _10% ) / (80% RH-10% RH) × 10 ⁶

The cellulose acylate film preferably used in the present invention preferably has a haze in the range of 0.01 to 2%. Here, the haze can be measured as follows.
The haze is measured by measuring a cellulose acylate film sample 40 mm × 80 mm at 25 ° C. and 60% RH with a haze meter “HGM-2DP” {manufactured by Suga Test Instruments Co., Ltd.}.
Measure according to 6714.

  Furthermore, the cellulose acylate film preferably used in the present invention preferably has a mass change in the range of 0 to 5% by mass when left for 48 hours under conditions of 80 ° C. and 90% RH.

  Furthermore, the cellulose acylate film preferably used in the present invention has a dimensional change when left standing for 24 hours under conditions of 60 ° C. and 95% RH, and is allowed to stand for 24 hours under conditions of 90 ° C. and 5% RH. It is preferable that the dimensional change when placed is in the range of 0 to 5%.

The photoelastic coefficient is preferably 50 × 10 ⁻¹³ cm ² / dyne or less in order to reduce the color change with time of the liquid crystal display device.
As a specific measuring method, a tensile stress was applied to the major axis direction of a cellulose acylate film sample 10 mm × 100 mm, and the retardation at that time was measured with an ellipsometer “M150” {JASCO Corporation}. The photoelastic coefficient was calculated from the amount of change in retardation with respect to stress.

[Melting film formation]
The method for producing the optical film of the present invention may be melt film formation. A raw material such as a polymer or an additive as a raw material may be heated and melted, and this may be extruded and formed into a film by injection molding, or the raw material may be sandwiched between two heated plates and pressed to form a film.

  The temperature for heating and melting is not particularly limited as long as the raw polymer is melted uniformly. Specifically, it is heated to a temperature equal to or higher than the melting point or softening point. In order to obtain a uniform film, the material is melted by heating to a temperature higher than the melting point of the starting polymer, preferably 5 to 40 ° C. higher than the melting point, particularly preferably 8 to 30 ° C. higher than the melting point. preferable.

[Alignment film]
The optical compensation film may have an alignment film between the optical film of the present invention (preferably a cellulose acylate film) and the optically anisotropic layer. In addition, the alignment film is used only when the optically anisotropic layer is prepared, and after the optically anisotropic layer is formed on the alignment film, only the optically anisotropic layer is formed on the cellulose acylate film of the present invention. You may transcribe.
In the present invention, the alignment film is preferably a layer made of a crosslinked polymer. The polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like; or a cross-linking agent that is a highly reactive compound Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

The alignment film composed of a crosslinked polymer can be usually formed by applying a coating solution containing the polymer or a mixture of a polymer and a crosslinking agent on a support, followed by heating.
In the rubbing process described later, it is preferable to increase the degree of cross-linking in order to suppress dust generation in the alignment film. The value (1- (Ma / Mb)) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. When Mb)) is defined as the degree of crosslinking, the degree of crosslinking is preferably 50% to 100%, more preferably 65% to 100%, and most preferably 75% to 100%.

In the present invention, the polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. Of course, a polymer having both functions can also be used. Examples of the polymer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyl toluene copolymer. , Chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, gelatin, polyethylene, polypropylene, polycarbonate, etc. Examples thereof include compounds such as polymers and silane coupling agents. Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyville alcohol, and modified polyvinyl alcohol, and gelatin, polyville alcohol, and modified polyvinyl alcohol are preferred. Mention may be made of bil alcohol and modified polyvinyl alcohol.
In the case of directly coating polyvinyl alcohol and modified polyvinyl alcohol on the cellulose acylate film of the present invention, a method of providing a hydrophilic undercoat layer or applying a saponification treatment is preferably used.

Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferable.
Examples of the polyvinyl alcohol include those having a saponification degree of 70 to 100%, generally those having a saponification degree of 80 to 100%, and more preferably those having a saponification degree of 82 to 98%. The degree of polymerization is preferably in the range of 100 to 3000.
Examples of the modified polyvinyl alcohol include those modified by copolymerization (modified groups such as COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ Na, C ₁₂ H _25, etc. Modified by chain transfer (for example, COONa, SH, SC ₁₂ H ₂₅ etc. are introduced as modifying groups), modified by block polymerization (modified groups such as COOH, for example) , CONH ₂ , COOR, C ₆ H _5, etc. are introduced). As a polymerization degree, the range of 100-3000 is preferable. Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100% is preferable, and unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is more preferable.
In order to impart adhesion between the cellulose acylate film and the optically anisotropic layer, it is preferable to introduce a crosslinking / polymerization active group into the polyvinyl alcohol, and preferable examples thereof include JP-A-8-338913. It is described in detail in the publication.
In the case of using a hydrophilic polymer such as polyvinyl alcohol for the alignment film, it is preferable to control the water content from the viewpoint of the degree of hardening, preferably 0.4% to 2.5%, 0.6% More preferably, it is -1.6%. The water content can be measured with a commercially available Karl Fischer moisture content measuring device.
The alignment film preferably has a thickness of 10 microns or less.

[Polarizer]
In the present invention, a polarizing plate comprising a polarizing film and a pair of protective films sandwiching the polarizing film, wherein at least one of the protective films includes the optical film (preferably a cellulose acylate film). A board is provided. For example, a polarizing film obtained by dyeing a polarizing film made of a polyvinyl alcohol film or the like with iodine, stretching, and laminating both surfaces with a protective film can be used. The polarizing plate is disposed outside the liquid crystal cell. It is preferable that a pair of polarizing plates each including a polarizing film and a pair of protective films sandwiching the polarizing film are disposed with the liquid crystal cell interposed therebetween. The protective film disposed on the liquid crystal cell side is preferably the optical film of the present invention (preferably a cellulose acylate film) or the optical compensation film 4.

"adhesive"
The adhesive between the polarizing film and the protective film is not particularly limited, but polyvinyl alcohol (PVA) resin (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, and oxyalkylene group), boron compound aqueous solution, etc. Among them, PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 10 microns after drying, and particularly preferably 0.05 to 5 microns.

《Integrated manufacturing process of polarizing film and protective film》
A polarizing plate that can be used in the present invention can be produced by having a drying process in which a polarizing film is stretched and then contracted to reduce the volatile content, and a protective film is applied on at least one side after drying or during drying. After combining, it is preferable to have a post-heating step. As a specific attaching method, a protective film is attached to the polarizing film with an adhesive while holding both ends during the drying process of the film, and then both ends are cut off, or after drying, polarized from the holding parts on both ends. There is a method in which the film for film is released, both ends of the film are cut off, and then a protective film is applied. As a method for cutting off the ears, general techniques such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After bonding, it is preferable to heat in order to dry the adhesive and improve the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° C. or higher, more preferably 40 ° C. to 100 ° C., and further preferably 50 ° C. to 90 ° C. It is more preferable in terms of performance and production efficiency that these processes are manufactured in a consistent line.

<Performance of polarizing plate>
The optical properties and durability (short-term and long-term storage stability) of the polarizing plate of the present invention may be equivalent to or better than commercially available super high contrast products (for example, HLC2-5618 manufactured by Sanlitz Co., Ltd.). preferable. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization {(Tp−Tc) / (Tp + Tc)} 1/2 ≧ 0.9995 (where Tp is parallel transmittance, and Tc is orthogonal transmission) The change rate of the light transmittance before and after being left in an atmosphere of 60 ° C. and a humidity of 90% RH for 500 hours and 80 ° C. in a dry atmosphere for 500 hours is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change in polarization degree is preferably 1% or less, more preferably 0.1% or less based on the absolute value.

[Surface treatment of cellulose acylate film]
The cellulose acylate film preferably used in 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. . As the 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 under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above-mentioned conditions, and examples thereof include chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Regarding these, the details are disclosed in the Invention Association Public Technical Bulletin No. 2001-1745 (issued March 15, 2001, Invention Association) p. 30-32. 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.

[Alkaline saponification]
The alkali saponification treatment is preferably carried out by a method in which the cellulose acylate film is directly immersed in a saponification solution tank or a method in which the saponification solution is applied to the 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 coating solution has good wettability in order to apply the saponification solution to the cellulose acylate film, and the surface of the cellulose acylate film surface is not formed by the saponification solution solvent without forming irregularities. It is preferred to select a solvent that remains good. 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 during 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.

Moreover, it is preferable that the polarizing plate regarding this invention provides an optically anisotropic layer on a protective film.
The material of the optically anisotropic layer is not limited, such as a liquid crystal compound, a non-liquid crystal compound, an inorganic compound, and an organic / inorganic composite compound. As the liquid crystalline compound, a low molecular compound having a polymerizable group is aligned, and then the alignment is fixed by polymerization by light or heat, or the liquid crystalline polymer is heated and aligned and then cooled and aligned in a glassy state. You can use what you want to fix. As the liquid crystalline compound, those having a disk-like structure, those having a rod-like structure, and those having a structure showing optical biaxiality can be used. As the non-liquid crystalline compound, a polymer having an aromatic ring such as polyimide or polyester can be used.
Various methods, such as application | coating, vapor deposition, sputtering, can be used for the formation method of an optically anisotropic layer.
When an optically anisotropic layer is provided on the protective film of the polarizing plate, the adhesive layer is further provided outside the optically anisotropic layer from the polarizer side.

  Furthermore, the polarizing plate according to the present invention is preferably one in which at least one layer of a hard coat layer, an antiglare layer or an antireflection layer is provided on the surface of the protective film on at least one side of the polarizing plate. That is, as shown in FIG. 7, when the polarizing plate is used in a liquid crystal display device, it is preferable to provide a functional film 81 such as an antireflection layer on the protective film 72 disposed on the side opposite to the liquid crystal cell. As such a functional film, it is preferable to provide at least one layer of a hard coat layer, an antiglare layer or an antireflection layer. In addition, it is not necessary to provide each layer as a separate layer, for example, by providing an antireflection layer and a hard coat layer with an antiglare function, instead of providing two layers of an antireflection layer and an antiglare layer, You may make it function as an anti-glare antireflection layer.

(Antireflection layer)
In the present invention, at least a light scattering layer and a low refractive index layer are laminated in this order on the protective film of the polarizing plate, or a medium refractive index layer, a high refractive index layer, and a low refractive index on the protective film. An antireflection layer in which rate layers are laminated in this order is suitably provided. Preferred examples thereof are described below. In the former configuration, the specular reflectance is generally 1% or more, which is referred to as a low reflection (LR) film. In the latter configuration, it is possible to realize a mirror reflectivity of 0.5% or less, and this is called an Anti Reflection (AR) film.

[LR film]
A preferred example of an antireflection layer (LR film) in which a light scattering layer and a low refractive index layer are provided on a protective film of a polarizing plate will be described.
In the light scattering layer, mat particles are preferably dispersed, and the refractive index of the material other than the mat particles in the light scattering layer is preferably in the range of 1.50 to 2.00, and the low refractive index The refractive index of the layer is preferably in the range of 1.20 to 1.49. In the present invention, the light scattering layer is
It has both antiglare properties and hard coat properties, and may be a single layer or a plurality of layers, for example, two to four layers.

  The antireflection layer has an uneven surface shape, centerline average roughness Ra is 0.08 to 0.40 μm, 10-point average roughness Rz is 10 times or less Ra, average unevenness distance Sm is 1 to 100 μm, unevenness The standard deviation of the height of the convex part from the deepest part is 0.5 μm or less, the standard deviation of the average unevenness distance Sm with respect to the center line is 20 μm or less, and the surface with the inclination angle of 0 to 5 ° is 10% or more. It is preferable that it is designed so that sufficient anti-glare property and visual uniform matte feeling can be achieved.

Further, the ratio between the minimum value and the maximum value of the reflectance when the color of the reflected light under the C light source is in the range of a ^* value −2 to 2, b ^* value −3 to 3 and 380 nm to 780 nm. It is preferable that the color is 5 to 0.99 because the color of the reflected light becomes neutral. Furthermore, it is preferable that the b ^* value of the transmitted light under the C light source is 0 to 3 because the yellow color of white display when applied to a display device is reduced. Furthermore, if a 120 μm × 40 μm grid is inserted between the surface light source and the antireflection layer and the luminance distribution is measured on the film, the standard deviation of the luminance distribution is 20 or less. Since glare when the polarizing plate of the invention is applied is reduced, it is preferable.

  The antireflection layer that can be used in the present invention suppresses reflection of external light by setting its optical properties to a specular reflectance of 2.5% or less, a transmittance of 90% or more, and a 60 ° glossiness of 70% or less. This is preferable because visibility is improved. In particular, the specular reflectance is more preferably 1% or less, and most preferably 0.5% or less. Haze 20% to 50%, ratio of internal haze / total haze value 0.3 to 1, haze value after formation of low refractive index layer from haze value up to light scattering layer within 15%, comb width 0 .Transparent image clarity at 5 mm, 20% to 50%, vertical transmission light / transmittance ratio in the direction inclined by 2 ° from vertical is 1.5 to 5.0, thereby preventing glare on a high-definition LCD panel. This is preferable because blurring of characters and the like is reduced.

(Low refractive index layer)
The refractive index of the low refractive index layer that can be used in the present invention is preferably 1.20 to 1.49, more preferably 1.30 to 1.44. Furthermore, the low refractive index layer preferably satisfies the following formula (19) from the viewpoint of reducing the reflectance.
Formula (19): (m / 4) λ × 0.7 <n _L d _L <(m / 4) λ × 1.3
In the formula, m is a positive odd number, n _L is the refractive index of the low refractive index layer, and d _L is the film thickness (nm) of the low refractive index layer. Further, λ is a wavelength and is a value in the range of 500 to 550 nm.

The material for forming the low refractive index layer will be described below.
The low refractive index layer preferably contains a fluorine-containing polymer as a low refractive index binder.
As the fluorine polymer, a fluorine-containing polymer which is crosslinked by heat or ionizing radiation and having a dynamic friction coefficient of 0.03 to 0.20, a contact angle with water of 90 to 120 °, and a sliding angle of pure water of 70 ° or less is preferable. When the polarizing plate according to the present invention is mounted on an image display device, the lower the peel strength from a commercially available adhesive tape, the easier it is to peel off after sticking a seal or memo, and the peel strength is measured when measured with a tensile tester. It is preferably 500 gf or less, more preferably 300 gf or less, and most preferably 100 gf or less. Further, the higher the surface hardness measured with a microhardness meter, the harder it is to scratch, and the surface hardness is preferably 0.3 GPa or more, more preferably 0.5 GPa or more.

  Examples of the fluorine-containing polymer used in the low refractive index layer include perfluoroalkyl group-containing silane compounds {for example, hydrolysates and dehydrated condensates of (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane}. In addition, a fluorine-containing copolymer having a fluorine-containing monomer unit and a structural unit for imparting crosslinking reactivity as constituent components can be mentioned.

  Specific examples of the fluorine-containing monomer include fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, perfluorooctylethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.), (Meth) acrylic acid partial or fully fluorinated alkyl ester derivatives [e.g. "Biscoat 6FM" {manufactured by Osaka Organic Chemical Industry Co., Ltd.} or "M-2020" {manufactured by Daikin Industries Ltd.}], complete or Partially fluorinated vinyl ethers and the like can be mentioned, and perfluoroolefins are preferable, and hexafluoropropylene is particularly preferable from the viewpoint of refractive index, solubility, transparency, availability, and the like.

  As a structural unit for imparting crosslinking reactivity, a structural unit obtained by polymerization of a monomer having a self-crosslinkable functional group in the molecule in advance, such as glycidyl (meth) acrylate or glycidyl vinyl ether, a carboxyl group or a hydroxy group, Polymerization of monomers having amino groups, sulfo groups, etc. {eg (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, maleic acid, crotonic acid, etc.} Or a structural unit obtained by introducing a crosslinking reactive group such as a (meth) acryloyl group into the structural unit by a polymer reaction (for example, a method in which acrylic acid chloride is allowed to act on a hydroxy group). ) It is.

  In addition to the fluorine-containing monomer unit and the structural unit for imparting crosslinking reactivity, a monomer that does not contain a fluorine atom can be copolymerized as appropriate from the viewpoint of solubility in a solvent, film transparency, and the like. There are no particular limitations on the monomer units that can be used in combination. For example, olefins (ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylic esters (methyl acrylate, methyl acrylate, ethyl acrylate, acrylic acid 2) -Ethylhexyl), methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinylbenzene, vinyltoluene, α-methylstyrene, etc.), vinyl ethers (methyl) Vinyl ether, ethyl vinyl ether, cyclohexyl vinyl ether, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl cinnamate etc.), acrylamides (Nt-butylacrylamide, N-cyclo) Hexyl acrylamide), methacrylamides, and acrylonitrile derivatives.

  As described in JP-A-10-25388 and JP-A-10-147739, the above polymer may be used in combination with a curing agent as appropriate.

(Light scattering layer)
The light scattering layer is formed for the purpose of imparting to the film a light diffusibility due to at least one of surface scattering and internal scattering and a hard coat property for improving the scratch resistance of the film. Therefore, it is formed including a binder for imparting hard coat properties, matte particles for imparting light diffusibility, and inorganic fillers for increasing the refractive index, preventing crosslinking shrinkage, and increasing the strength as necessary. The In addition, by providing such a light scattering layer, the light scattering layer also functions as an antiglare layer, and the polarizing plate has an antiglare layer.

  The thickness of the light scattering layer is preferably 1 to 10 μm and more preferably 1.2 to 6 μm for the purpose of imparting hard coat properties. If the film thickness of the light scattering layer is not less than the lower limit, problems such as insufficient hardware properties are unlikely to occur, and if the thickness is not more than the upper limit, inconveniences such as curling and brittleness are deteriorated and workability is insufficient. Is preferable because it is difficult to cause.

The binder of the light scattering layer is preferably a polymer having a saturated hydrocarbon chain or a polyether chain as the main chain, and more preferably a polymer having a saturated hydrocarbon chain as the main chain. The binder polymer preferably has a crosslinked structure. As the binder polymer having a saturated hydrocarbon chain as a main chain, a polymer of an ethylenically unsaturated monomer is preferable. As the binder polymer having a saturated hydrocarbon chain as the main chain and having a crosslinked structure, a (co) polymer of monomers having two or more ethylenically unsaturated groups is preferable. In order to make the binder polymer have a high refractive index, the monomer structure contains an aromatic ring and at least one atom selected from halogen atoms other than fluorine, sulfur atoms, phosphorus atoms, and nitrogen atoms. You can also choose.

  Examples of the monomer having two or more ethylenically unsaturated groups include esters of polyhydric alcohol and (meth) acrylic acid {for example, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, hexanediol di ( (Meth) acrylate, 1,4-cyclohexanediacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (Meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2,3- Chlorohexane tetramethacrylate, polyurethane polyacrylate, polyester polyacrylate}, modified ethylene oxide, vinylbenzene and derivatives thereof (for example, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4 -Divinylcyclohexanone), vinyl sulfone (e.g. divinyl sulfone), acrylamide (e.g. methylene bisacrylamide) and methacrylamide. Two or more of these monomers may be used in combination.

  Specific examples of the high refractive index monomer include bis (4-methacryloylthiophenyl) sulfide, vinyl naphthalene, vinyl phenyl sulfide, 4-methacryloxyphenyl-4′-methoxyphenyl thioether, and the like. Two or more of these monomers may be used in combination.

  Polymerization of these monomers having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator. Accordingly, a coating liquid containing a monomer having an ethylenically unsaturated group, a photo radical initiator or a thermal radical initiator, mat particles and an inorganic filler is prepared, and the coating liquid is applied onto a protective film, and then ionizing radiation or heat is applied. It can harden | cure by the polymerization reaction by and can form an antireflection layer. As these photo radical initiators, known ones can be used.

  The polymer having a polyether as the main chain is preferably a ring-opening polymer of a polyfunctional epoxy compound. The ring-opening polymerization of the polyfunctional epoxy compound can be performed by irradiation with ionizing radiation or heating in the presence of a photoacid generator or a thermal acid generator. Therefore, a coating solution containing a polyfunctional epoxy compound, a photoacid generator or a thermal acid generator, matte particles and an inorganic filler is prepared, and the coating solution is applied on a protective film and then cured by ionizing radiation or heat polymerization reaction. Thus, an antireflection layer can be formed.

  Instead of or in addition to a monomer having two or more ethylenically unsaturated groups, a monomer having a crosslinkable functional group is used to introduce a crosslinkable functional group into the polymer, and this crosslinkable functional group reacts. A crosslinked structure may be introduced into the binder polymer.

Examples of the crosslinkable functional group include an isocyanate group, an epoxy group, an aziridine group, an oxazoline group, an aldehyde group, a carbonyl group, a hydrazine group, a carboxyl group, a methylol group, and an active methylene group. Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. That is, in the present invention, the crosslinkable functional group may not react immediately but may exhibit reactivity as a result of decomposition.
These binder polymers having a crosslinkable functional group can form a crosslinked structure by heating after coating.

For the purpose of imparting antiglare properties, the light scattering layer contains matte particles having an average particle diameter of 1 to 10 μm, preferably 1.5 to 7.0 μm, for example, inorganic compound particles or resin particles, than filler particles. Is done. Specific examples of the matte particles include preferably particles of inorganic compounds such as silica particles and TiO ₂ particles; resin particles such as acrylic particles, crosslinked acrylic particles, polystyrene particles, crosslinked styrene particles, melamine resin particles, and benzoguanamine resin particles. It is done. Of these, crosslinked styrene particles, crosslinked acrylic particles, crosslinked acrylic styrene particles, and silica particles are preferable. The shape of the mat particles can be either spherical or irregular.

  Two or more kinds of mat particles having different particle diameters may be used in combination. It is possible to impart anti-glare properties with mat particles having a larger particle size and to impart other optical characteristics with mat particles having a smaller particle size.

  Further, the particle size distribution of the mat particles is most preferably monodisperse, and the particle sizes of the particles are preferably closer to each other. For example, when particles having a particle size of 20% or more than the average particle size are defined as coarse particles, the proportion of coarse particles is preferably 1% or less, more preferably 0.1% of the total number of particles. % Or less, more preferably 0.01% or less. Matt particles having such a particle size distribution are obtained by classification after a normal synthesis reaction, and a matting agent having a more preferable distribution can be obtained by increasing the number of classifications or increasing the degree of classification.

The mat particles are contained in the light scattering layer so that the amount of mat particles in the formed light scattering layer is preferably 10 to 1000 mg / m ² , more preferably 100 to 700 mg / m ² .
The particle size distribution of the mat particles is measured by a Coulter counter method, and the measured distribution is converted into a particle number distribution.

The light scattering layer is made of an oxide of at least one metal selected from titanium, zirconium, aluminum, indium, zinc, tin, and antimony, in addition to the matte particles, in order to increase the refractive index of the layer. Thus, it is preferable that an inorganic filler having an average particle diameter of 0.2 μm or less, preferably 0.1 μm or less, more preferably 0.06 μm or less is contained.
Conversely, in order to increase the difference in refractive index from the mat particles, it is also preferable to use a silicon oxide in order to keep the refractive index of the light scattering layer using the high refractive index mat particles low. The preferred particle size is the same as that of the aforementioned inorganic filler.

Specific examples of the inorganic filler to be used in the light scattering _{layer, TiO 2, ZrO 2, Al} 2 O 3, In 2 O 3, ZnO, SnO 2, Sb 2 O 3, ITO and SiO ₂ and the like. TiO ₂ and ZrO ₂ are particularly preferable in terms of increasing the refractive index. The surface of the inorganic filler is preferably subjected to a silane coupling treatment or a titanium coupling treatment, and a surface treatment agent having a functional group capable of reacting with a binder species on the filler surface is preferably used.

  The amount of these inorganic fillers added is preferably 10 to 90% of the total mass of the light scattering layer, more preferably 20 to 80%, and particularly preferably 30 to 75%.

  Such a filler does not scatter because the particle size is sufficiently smaller than the wavelength of light, and a dispersion in which the filler is dispersed in a binder polymer behaves as an optically uniform substance.

  The bulk refractive index of the mixture of binder and inorganic filler in the light scattering layer is preferably 1.50 to 2.00, more preferably 1.51 to 1.80. In order to make the refractive index within the above range, the kind and amount ratio of the binder and the inorganic filler may be appropriately selected. How to select can be easily known experimentally in advance.

  In order to ensure surface uniformity such as uneven coating, uneven drying, point defects, etc., the light scattering layer should be coated with either a fluorine-based or silicone-based surfactant, or both for forming the light scattering layer. Contained in the composition. In particular, a fluorine-based surfactant is preferably used because an effect of improving surface defects such as coating unevenness, drying unevenness, and point defects of the antireflection layer preferably used in the present invention appears in a smaller addition amount. The purpose is to increase productivity by giving high-speed coating suitability while improving surface uniformity.

[AR film]
Next, an antireflection layer (AR film) in which a middle refractive index layer, a high refractive index layer, and a low refractive index layer are laminated in this order on the protective film will be described.

An antireflection layer comprising at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) in order on the protective film is designed to have a refractive index satisfying the following relationship. .
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of protective film> refractive index of low refractive index layer

Further, a hard coat layer may be provided between the protective film and the medium refractive index layer. Further, it may be composed of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer. For example, JP-A-8-122504, 8-110401, 10-300902, Examples thereof include antireflection layers described in JP-A-2002-243906, JP-A No. 2000-11706, and the like.
Further, other functions may be imparted to each layer. For example, an antifouling low refractive index layer and an antistatic high refractive index layer (for example, JP-A Nos. 10-206603 and 2002-2002). 243906 publication etc.) etc. are mentioned.

  The haze of the antireflection layer is preferably 5% or less, more preferably 3% or less. Further, the surface strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400.

(High refractive index layer and medium refractive index layer)
The layer having a high refractive index of the antireflection layer is composed of a cured film containing at least an inorganic compound fine particle having a high refractive index having an average particle diameter of 100 nm or less and a matrix binder.

  Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.

In order to obtain such fine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agent, etc .: JP-A Nos. 1-295503, 11-153703, 2000-9908, Anionic compounds or organometallic coupling agents: JP 2001-310432 A, etc., core-shell structure with high refractive index particles as the core (JP 2001-166104 A, etc.), combined use of specific dispersant (For example, JP-A-11-15370
No. 3, U.S. Pat. No. 6,210,858, JP-A No. 2002-277609, etc.).

Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
More preferable materials include a polyfunctional compound-containing composition having at least two polymerizable groups of at least one of radically polymerizable and cationically polymerizable, a composition containing an organometallic compound containing a hydrolyzable group, And at least one composition selected from compositions containing the partial condensates thereof, for example, JP-A 2000-47004, 2001-315242, 2001-31871, 2001- And compounds described in Japanese Patent No. 296401.

  A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.

  The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

  The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70. The thickness is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

(Low refractive index layer)
The low refractive index layer is sequentially laminated on the high refractive index layer. The refractive index of the low refractive index layer is preferably 1.20 to 1.55. More preferably, it is 1.30-1.50.

  The low refractive index layer is preferably constructed as an outermost layer having scratch resistance and antifouling properties. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known means for thin film layers including introduction of silicone, introduction of fluorine, and the like can be applied.

The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing a fluorine atom in a range of 35 to 80% by mass, for example, paragraph numbers [0018] to [0026] of JP-A-9-222503. Examples thereof include the compounds described in paragraph Nos. [0019] to [0030] of JP-A-11-38202, paragraph numbers [0027] to [0028] of JP-A-2001-40284, JP-A 2000-284102, and the like.
The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47.

  The silicone compound is preferably a compound having a polysiloxane structure, containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone [for example, “Silaplane” {manufactured by Chisso Corporation etc.]], polysiloxane containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

The crosslinking or polymerization reaction of at least one of the fluorine-containing polymer and the siloxane polymer having a crosslinking or polymerizable group is performed simultaneously with the application of the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer and the like. Alternatively, it is preferable to form the low refractive index layer by light irradiation or heating after coating.

A sol / gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst is also preferable.
For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly (perfluoroalkyl ether) group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002-53804). Etc.) and the like.

  The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler {eg, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride) as additives other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820}, silane coupling agents, slip agents, surfactants, and the like. .

  When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.

  The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

(Hard coat layer)
The hard coat layer is provided on the surface of the protective film in order to impart physical strength to the protective film provided with the antireflection layer. In particular, it is preferably provided between the protective film 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 in the curable compound is preferably a photopolymerizable functional group. Also preferred are hydrolyzable functional group-containing organometallic compounds and organoalkoxysilyl compounds.

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 WO 00/46617.

  The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

  The hard coat layer can also serve as an antiglare layer containing particles having an average particle size of 0.2 to 10 μm and imparted with an antiglare function (antiglare function).

  The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

The surface strength of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400. Further, in the Taber test according to JIS K-5400, the smaller the wear amount of the test piece before and after the test, the better.

(Other layers of antireflection layer)
Further, a forward scattering layer, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Antistatic layer)
When an antistatic layer is provided, 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, Sn, Al, In, Si, Mg, Ba, Mo, W, or V can be used as the metal that forms the metal oxide without coloring, and a metal oxide containing these as main components is used. It is preferable.

Specific examples of the metal oxide include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , WO ₃ , V ₂ O _5, etc. These composite oxides are good, and ZnO, TiO ₂ and SnO ₂ are particularly 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 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. Note that the volume resistance value and the surface resistance value are different physical property values and cannot be simply compared. However, in order to secure conductivity of 10 ⁻⁸ (Ωcm ⁻³ ) or less in volume resistance value, The prevention layer should just have a surface resistance value of 10 ⁻¹⁰ (Ω / □) or less, more preferably 10 ⁻⁸ (Ω / □). The surface resistance value of the antistatic 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.

[Liquid Crystal Display]
The above-mentioned optical film (preferably a cellulose acylate film) or a polarizing plate obtained by laminating an optical film and a polarizing film is advantageously used for a liquid crystal display device, particularly a transmissive liquid crystal display device.
The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. A polarizing plate consists of a polarizing film and two transparent protective films arrange | positioned at the both sides. The liquid crystal cell carries a liquid crystal between two electrode substrates.
One polarizing plate of the present invention is disposed on one side of the liquid crystal cell, or two are disposed on both sides of the liquid crystal cell.
The liquid crystal cell is preferably in VA mode, OCB mode, IPS mode, or TN mode.
In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are 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 rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). (2) Liquid crystal cell (SID97, Digest of tech) in which VA mode is multi-domained (in MVA mode) for widening the viewing angle
. Papers 28 (1997) 845), (3) A liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied. (Preliminary collections 58-59 (1998) of the Japanese Liquid Crystal Discussion Group) and (4) SURVAVAL mode liquid crystal cells (presented at LCD International 98) are included.
In the case of a VA mode liquid crystal display device, when only one polarizing plate of the present invention is used, it is preferably used on the backlight side.
The OCB mode liquid crystal cell is 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. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions 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 a TN mode liquid crystal cell, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °.
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

[Example 1]
Formation of Cellulose Acylate Film (1) Cellulose Acylate Addition of sulfuric acid as a catalyst to cellulose as a raw material and further addition of carboxylic anhydride as a raw material for acyl substituents to carry out an acylation reaction, followed by neutralization It was prepared by saponification aging. At this time, by adjusting the amount of catalyst, the type and amount of carboxylic anhydride, the amount of neutralizing agent added, the amount of water added, the reaction temperature, and the aging temperature, the type of acyl group, the degree of substitution, the bulk density, and the degree of polymerization Different cellulose acylates were prepared. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
Among the cellulose acylates prepared as described above, the degree of acetyl group substitution is 2.79,
The following dope preparation was performed using cellulose acylate of DS6 / (DS2 + DS3 + DS6) = 0.322.

(2) Dope Preparation <1-1> Cellulose Acylate Solution The following 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 It filtered with the sintered metal filter with an average hole diameter of 10 micrometers.

―――――――――――――――――――――――――――――――――
Cellulose acylate solution ――――――――――――――――――――――――――――――――――
Cellulose acylate 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 Solution Next, the following composition containing the cellulose acylate solution prepared by the above method was charged into a dispersing machine to prepare a matting agent dispersion.

――――――――――――――――――――――――――――――――――
Matting agent dispersion ――――――――――――――――――――――――――――――――――
Silica particles having an average particle diameter 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 10.3 parts by mass ――――――――――――――――――――――――――――

<1-3> Retardation developer solution Next, the following composition containing the cellulose acylate solution prepared by the above method is put into a mixing tank and dissolved by stirring while heating to prepare a retardation developer solution A. did.

―――――――――――――――――――――――――――――――――
Retardation developer solution A
―――――――――――――――――――――――――――――――――
Retardation developer A 20.0 parts by mass Methylene chloride 58.3 parts by mass Methanol 8.7 parts by mass Cellulose acylate solution 12.8 parts by mass ――――――――――――――――― ―――――――――――――――

  100 parts by weight of the cellulose acylate solution, 1.35 parts by weight of the matting agent dispersion, and retardation developer solution A in an amount such that the amount of retardation developer A in the cellulose acylate film is 5.1 parts by weight. Were mixed to prepare a dope for film formation.

(Casting)
The above dope was cast using a glass plate casting apparatus. The film was dried for 6 minutes with warm air at a supply air temperature of 70 ° C., and the film peeled off from the glass plate was fixed to the frame. It dried and manufactured the cellulose acylate film with a film thickness of 108 micrometers. The glass transition temperature of the cellulose acylate film was 140 ° C.
This film was gripped on four sides with a biaxial stretching test apparatus (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and subjected to stretching and shrinking processes under the conditions shown in Table 1. As common conditions for the stretching and shrinking processes, after preheating for 2 minutes at the specified supply air temperature in each example before these processes, the film is stretched in the TD direction and contracted in the MD direction at this supply air temperature. It was. It was separately confirmed that the supply air temperature and the film temperature were the same. After completion of these steps, air cooling was performed for 5 minutes while holding the clip. MD in the table indicates the casting direction at the time of casting the glass plate, and TD indicates the width direction perpendicular to the casting direction. Let these films be films 1-3.

<Film crystallization temperature>
The crystallization temperature of this film was determined by DSC. The results are shown in Table 1.

<Re, Rth at film wavelengths of 450, 550 and 650 nm>
Re and Rth at wavelengths of 450, 550 and 650 nm of this film were measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments) according to the method described above.
The results are shown in Table 1. From Table 1, it can be seen that the values of Re and Rth at wavelengths of 450, 550 and 650 nm of the cellulose acylate film produced by the production method of the present invention satisfy all the relationships of the above formulas (I) to (III).

  From Table 1, the cellulose acylate film subjected to the stretching and shrinking step at a temperature within the range of the present invention was compared with the cellulose acylate film subjected to the step outside the range of the present invention, and the width direction of the linear thermal expansion coefficient was It can be seen that the longitudinal ratio and linear thermal expansion coefficient values can be controlled within the scope of the present invention.

<Preparation of polarizing plate>
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film.
The cellulose acylate films 1 to 8 produced above were each attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. The saponification treatment was performed under the following conditions.
A 1.5 mol / liter aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.01 mol / liter 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. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C.
A commercially available cellulose triacylate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is saponified, and is attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive, and at 70 ° C. for 10 minutes or more. Dried.
The transmission axis of the polarizing film and the slow axis of the cellulose acylate film produced as described above were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacylate film were arranged so as to be orthogonal to each other.

<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.

<Mounting on VA panel>
A commercially available super high contrast product (HLC2-5618 manufactured by Sanlitz Co., Ltd.) was used for the upper polarizing plate (observer side) of the liquid crystal display device using the vertical alignment type liquid crystal cell. A polarizing plate provided with films 1 to 3 was placed on the lower polarizing plate (backlight side) so that the cellulose acylate film 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. The crossed Nicols were arranged 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 left-right direction.
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally black mode with 5 V white display and 0 V black display was set. The black display transmittance (%) at the azimuth angle of 45 degrees and the polar angle of 60 degrees and the color shift Δx between the azimuth angle of 45 degrees polar angle of 60 degrees and the azimuth angle of 180 degrees and polar angle of 60 degrees were obtained. .
Color shift:
ΔCu'v 'at an azimuth angle of 45 °; u'v' (polar angle 60 °)-u'v '(polar angle 0 °) and ΔCu'v' at an azimuth angle 135 °; u'v '(pole Sum of angle 60 °) -u'v '(polar angle 0 °). (U′v ′: color coordinates in CIELAB space).
In addition, using the measurement ratio (EZ-Contrast 160D, manufactured by ELDIM) as a contrast ratio, the ratio of transmittance (white display / black display) is used in eight stages from black display (L1) to white display (L8). The angle (a polar angle range with a contrast ratio of 10 or more and no black-side gradation inversion) was measured. The results are shown in Table 1. As a result of observing the produced liquid crystal display device, the liquid crystal panel using the film of the present invention was able to realize a neutral black display in both the front direction and the viewing angle direction.

<Evaluation by wet heat treatment of liquid crystal display device>
The prepared liquid crystal display device was left for 48 hours in an environment of 60 ° C. and a relative humidity of 90%. It moved to the environment of 25 degreeC60% after a process. When the power was turned on and the black display state was observed, light leakage occurred around the liquid crystal display device using the films 4, 5 and 8. On the other hand, the liquid crystal display device using the films 1, 2 and 3 did not leak light, and a good black display was obtained.
Next, the panel produced from the liquid crystal display device was taken out and moved to an environment of 25 ° C. and 60%, and the amount of warpage in 20 minutes was measured. The amount of warpage w (mm) represents the distance between the short side and the plane when the panel is placed on the plane so that the center is in contact. L (mm) indicates the length in the long side direction of the panel.
The results are shown in Table 1. The panel of the present invention has a small amount of warpage, while the amount of warpage of the comparative example is large, and the effect of the present invention is remarkable.

Viewing angle (polar angle range with contrast ratio of 10 or more and no black-side gradation inversion)
○ Polar angle of 80 ° or more in the top, bottom, left, and right ○ △ Polar angle of 80 ° or more in three directions, up, down, left, and right △ Polar angle of 80 ° or more in two directions Angle 80 ° or more

Color shift when displaying black (Δx)
○ Less than 0.02 ○ △ 0.02-0.04
△ 0.04-0.06
× 0.06 or more

[Example 2]
In the film production conditions in Example 1, films were produced by changing the conditions of the stretching process and the shrinking process. Table 2 shows these process conditions.
A liquid crystal panel was prepared in the same manner as in Example 1, and panel warpage, peripheral light leakage, viewing angle, and color misregistration during black display were evaluated. The results are shown in Table 2.

  By including both the stretching step and the shrinking step according to the present invention and setting the temperature at the end of stretching within the range of the production method of the present invention, it is possible to obtain a liquid crystal display device having a wide viewing angle and a small color shift during black display. I understand that I can do it. It can also be seen that panel warpage after wet heat aging is suppressed to a level that does not cause light leakage in the peripheral portion by including both of these steps.

[Example 3]
<Creation of film>
Next, the relationship of the substitution degree DS2 with the acyl group of the hydroxyl group at the 2-position of the glucose unit of the cellulose acylate used, the substitution degree DS3 with the acyl group of the hydroxyl group at the 3-position, and the substitution degree DS6 with the acyl group of the hydroxyl group at the 6-position. Adjusted as shown in Table 3. Moreover, the cellulose acylate film was produced by the same method as Example 1 except having changed the quantity of the retardation expression agent with respect to Example 1. FIG. Let these films be the films 31-35. These films were subjected to polarizing plate processing in the same manner as in Example 1.

<Mounting on VA panel 2 sheets type>
A polarizing plate provided with films 31 to 34 on both the upper polarizing plate (observer side) and the lower polarizing plate (backlight side) of the liquid crystal display device using the vertical alignment type liquid crystal cell of Example 1, The cellulose acylate film was placed 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. The crossed Nicols were arranged 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 left-right direction.
As in Example 1, color misregistration and viewing angle were evaluated, and further wet heat treatment was performed to observe panel warpage and peripheral light leakage. The results are shown in Table 3.

  In Example 3, neutral black display with a wide viewing angle was realized. On the other hand, although the unevenness of the periphery due to the aging of wet heat was not observed, there was a difference in the warpage amount of the panel, and the warpage amount was smaller as the value of DS6 / (DS2 + DS3 + DS6) was larger.

[Example 4]
To the cellulose acylate films 31 to 34 produced in Example 3, a 1.0 mol / L potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass). Part) was applied at 10 cc / m ² and kept at a temperature of about 40 ° C. for 30 seconds, then the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second.
The contact angle of the alkali-treated surface with pure water was measured and found to be 41 °.

(Formation of alignment film)
An alignment film coating solution having the following composition was applied to the alkali-treated surface by a # 16 wire bar coater at 28 ml / m ² . The alignment film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.

────────────────────────────────────────
Alignment film coating solution composition ────────────────────────────────────────
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3, Sankyo Chemical Co., Ltd.) 0.35 parts by weight ────────────────────────────────────

(Rubbing process)
The transparent support on which the alignment film is formed is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, and rotated at 650 rpm. A rubbing treatment was performed on the alignment film installation surface. The contact length between the rubbing roll and the transparent support was set to 18 mm.

(Formation of optically anisotropic layer)
102 kg of methyl ethyl ketone, 40.01 kg of discotic liquid crystalline compound (discotic liquid crystalline compound described below), ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 4.06 kg, cellulose acetate butyrate Rate (CAB531-1, Eastman Chemical Co., Ltd.) 0.35 kg, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.31 kg, sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 47 kg was dissolved. To the solution, 0.1 kg of a fluoroaliphatic group-containing copolymer (Megafac F780 manufactured by Dainippon Ink Co., Ltd.) was added to prepare a coating solution. The coating solution was continuously applied to the alignment film surface of the transparent support being conveyed at 20 m / min by rotating a # 3.2 wire bar at 391 rotations in the same direction as the film conveyance direction.

  The temperature was continuously heated from room temperature to 100 ° C., the solvent was dried, and then the film surface wind speed of the disc-like optically anisotropic layer was 2.5 m / sec in a drying zone at 130 ° C. The disc-shaped liquid crystalline compound was aligned by heating for 2 seconds. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 100 ° C. Irradiation was performed for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystalline compound was fixed to the orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.

When the viscosity of the optically anisotropic layer was measured at a film surface temperature of 127 ° C., it was 695 cp. The viscosity is a result of measuring a liquid crystal layer (excluding the solvent) having the same composition as the optically anisotropic layer with a heating E-type viscosity system.
A part of the produced roll-shaped optical compensation film was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 36 nm. Further, the angle (tilt angle) between the disc surface of the discotic liquid crystalline compound in the optically anisotropic layer and the support surface varied continuously in the depth direction of the layer, and averaged 28 °. Furthermore, when only the optically anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optically anisotropic layer was measured, it was 45 ° with respect to the longitudinal direction of the optical compensation film.

<Evaluation of mounting on OCB panel>
These cellulose acylate film samples with an optically anisotropic layer were subjected to polarizing plate processing in the same manner as in Example 1.

<Mounting evaluation in liquid crystal display device> (Production of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.7 μm. A bend-aligned liquid crystal cell was prepared by injecting a liquid crystal compound (ZLI1132, manufactured by Merck & Co., Inc.) having a Δn of 0.1396 into the cell gap.
Two polarizing plates prepared so as to sandwich the prepared bend alignment cell were attached. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were arranged so as to be antiparallel.
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2V white display and 5V black display was set. A voltage at which the transmittance at the front is minimized, that is, a black voltage, is applied, and the black display transmittance (%) at an azimuth angle of 0 ° and a polar angle of 60 ° direction viewing angle and an azimuth angle of 0 ° and a polar angle of 60 ° A color shift Δx with an azimuth angle of 180 degrees and a polar angle of 60 degrees was determined. Further, using the measuring device (EZ-Contrast 160D, manufactured by ELDIM) as the contrast ratio, the transmittance ratio (white display / black display), the visual field is displayed in eight stages from black display (L1) to white display (L8). The corner was measured. The results are organized as in Example 1 and shown in Table 4. Both viewing angle and color shift during black display showed good performance.

[Example 5]
Among the prepared cellulose acylates, cellulose acylate having an acetyl group substitution degree of 1.10, a butyryl group substitution degree of 1.70, and a viscosity average polymerization degree of 350 was used. Cellulose acylate 100 parts by mass, ethylphthalylethylglyco Put 5 parts by mass of rate, 3 parts by mass of triphenyl phosphate, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol, gradually raise the temperature while slowly stirring the mixture, and raise to 80 ° C over 60 minutes to dissolve. did. The inside of the container was 1.5 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately, 5 parts by mass of the above cellulose acylate, 5 parts by mass of TINUVIN 109 (manufactured by Ciba Specialty Chemicals), 15 parts by mass of TINUVIN 326 (manufactured by Ciba Specialty Chemicals), AEROSIL A UV absorber solution was prepared by mixing 0.5 parts by mass of R972V (manufactured by Nippon Aerosil Co., Ltd.) with 94 parts by mass of methylene chloride and 8 parts by mass of ethanol, stirring and dissolving. R972V was previously dispersed in ethanol and added.

The ultraviolet absorbent solution was added at a ratio of 6 parts by mass with respect to 100 parts by mass of the dope and sufficiently mixed by a static mixer.
(Casting)
The dope thus prepared was cast in the same manner as described above in Example 1 (Casting) to produce a cellulose acylate film having a thickness of 108 μm. The crystallization temperature of this film was 155 ° C. This film was gripped on four sides by a biaxial stretching test apparatus in the same manner as described above (casting), and stretched and contracted under the conditions shown in Table 5. Let the obtained film be the films 51-54.

<Film evaluation>
Using the prepared film, measurement of <Re, Rth> at wavelengths of 450, 550, and 650 nm of the film was performed as in Example 1, and a polarizing plate was prepared. Further, in the same manner as in Example 1, <fabrication of liquid crystal cell> and <mounting on VA panel> were performed to evaluate the mounting. The results are shown in Table 5.
The panel according to the present invention has a small amount of warpage after the lapse of time of wet heat and light leakage around the panel at the time of black display, and the effect of the present invention is remarkable.

[Example 6]
Among the prepared cellulose acylates, cellulose acylate having an acetyl group substitution degree of 2.00, a propionyl group substitution degree of 0.60, and a viscosity average polymerization degree of 350 was used. Cellulose acylate 100 parts by mass, ethylphthalylethylglyco Put 5 parts by mass of rate, 3 parts by mass of triphenyl phosphate, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol, gradually raise the temperature of the mixture while stirring slowly, and raise to 80 ° C over 60 minutes to dissolve. did. The inside of the container was 1.5 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately, 5 parts by mass of the above cellulose acylate, 5 parts by mass of TINUVIN 109 (manufactured by Ciba Specialty Chemicals), 15 parts by mass of TINUVIN 326 (manufactured by Ciba Specialty Chemicals), AEROSIL A UV absorber solution was prepared by mixing 0.5 parts by mass of R972V (manufactured by Nippon Aerosil Co., Ltd.) with 94 parts by mass of methylene chloride and 8 parts by mass of ethanol, stirring and dissolving. R972V was previously dispersed in ethanol and added.

The ultraviolet absorbent solution was added at a ratio of 6 parts by mass with respect to 100 parts by mass of the dope and sufficiently mixed by a static mixer.
(Casting)
The dope thus prepared was cast in the same manner as described above in Example 1 (casting) to produce a cellulose acylate film having a thickness of 108 μm. The glass transition temperature of the cellulose acylate film was 140 ° C. This film was gripped on four sides by a biaxial stretching test apparatus in the same manner as described above (casting), and stretched and contracted under the conditions shown in Table 4. The resulting film is referred to as film 51.

<Creation of film using other substituents>
Films 52 to 54 were prepared by changing the substitution degree of butyryl group (Bt) and benzoyl group (Bz) as the substituents on film 51 as shown in Table 5.

<Film evaluation>
Using the prepared film, <Re, Rth at film wavelengths of 450, 550 and 650 nm> was measured in the same manner as in Example 1, and a polarizing plate was prepared in the same manner as in Example 1. Further, in the same manner as in Example 3, <production of liquid crystal cell>, and <mounting on VA panel> were performed to evaluate the mounting. The results are shown in Table 5.

  As described above, the cellulose acylate film of the present invention in which the degree of substitution with a propionyl group, butyryl group or benzoyl group is 0 or more can also realize a wide viewing angle and excellent color shift performance during black display. Recognize.

  According to the present invention, a cellulose acylate film, particularly for VA, IPS and OCB modes, which has a liquid crystal cell accurately optically compensated and improves color shift depending on the viewing angle direction during high contrast and black display, A production method and a polarizing plate using the cellulose acylate film are provided. Further, according to the present invention, there is provided a liquid crystal display device in which the warpage of the panel is suppressed and the light leakage at the periphery of the image after wet heat aging is improved.

It is a schematic diagram explaining the structural example of the liquid crystal display device of the conventional VA mode. It is a schematic diagram explaining the structural example of the liquid crystal display device of the conventional VA mode. It is a schematic diagram explaining the structural example of the liquid crystal display device of this invention. It is a graph which shows the optical characteristic about an example of the optical compensation film used for this invention. It is the schematic of the Poincare sphere used in order to demonstrate the change of the polarization state of the incident light in the liquid crystal display device of this invention. It is the schematic of the Poincare sphere used in order to demonstrate the change of the polarization state of the incident light in an example of the conventional liquid crystal display device. It is a figure which shows typically the cross-sectional structure of another example of the polarizing plate of this invention. It is a figure which shows the structural example of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 70 Polarizing plate 71 Polarizer 72, 73 Protective film 81 Functional film 101 Polarizing film 102 Absorption axis 103a Protective film 104a In-plane slow axis 105 Optical compensation film 106 Substrate 107 Liquid crystalline molecule 108 Substrate 109 Optical compensation film 109a In-plane slow Phase axis 203a Protective film 204a In-plane slow axis 201 Polarizing film 202 Absorption axis

Claims (14)

  Of the linear thermal expansion coefficient in the longitudinal direction of the film and the linear thermal expansion coefficient in the width direction that is substantially perpendicular to the longitudinal direction, a value obtained by dividing the smaller one by the larger one is 0.5 or less and 0.1 or more. An optical film characterized in that   2. The optical film according to claim 1, wherein one of the linear thermal expansion coefficient in the longitudinal direction and the linear thermal expansion coefficient in the width direction is 42 or less and the other is 80 or more. 3. The optical film according to claim 1, wherein the front retardation Re and the retardation Rth in the film thickness direction at wavelengths of 450 nm, 550 nm, and 650 nm satisfy the following formulas (I) to (III).
Formula (I): 0.4 <{(Re (450) / Rth (450)) / (Re (550) / Rth (550))} <0.95
And 1.05 <{(Re (650) / Rth (650)) / (Re (550) / Rth (550))} <1.9.
Formula (II): 0.1 <(Re (450) / Re (550)) <0.95
Formula (III): 1.03 <(Re (650) / Re (550)) <1.93
[Wherein, Re (λ) is the front retardation Re (unit: nm) at a wavelength λnm, and Rth (λ) is the retardation Rth (unit: nm) in the film thickness direction at a wavelength λnm. ]   A method for producing an optical film comprising a stretching step of stretching a film and a shrinking step of shrinking, wherein the stretching end temperature is in the range of (crystallization temperature −10 ° C.) to (crystallization temperature + 10 ° C.). A method for producing an optical film.   The optical film according to claim 1, which is produced by the method according to claim 4.   6. The optical film according to claim 1, wherein the optical film is made of a cellulose acylate film.   The optical film according to claim 6, wherein the acyl substituent of the cellulose acylate consists only of an acetyl group, and the total substitution degree is 2.56 to 3.00. When the substitution degree of the 2-position hydroxyl group of the cellulose acylate with the acyl group is DS2, the substitution degree of the 3-position hydroxyl group with the acyl group is DS3, and the substitution degree of the 6-position hydroxyl group with the acyl group is DS6, The optical film according to claim 6 or 7, wherein the following formulas (IV) and (V) are satisfied.
Formula (IV): 2.0 ≦ (DS2 + DS3 + DS6) ≦ 3.0
Formula (V): DS6 / (DS2 + DS3 + DS6) ≧ 0.315 The acyl substituent is composed of at least two types of acetyl group / propionyl group / butanoyl group / benzoyl group , and the total substitution degree is 2.50 to 3.00. Optical film.   The optical film according to any one of claims 1 to 3 and claims 5 to 9, further comprising a retardation developer. It is a polarizing plate which has a polarizing film and a pair of protective film which pinches | interposes this polarizing film, Comprising: At least 1 sheet of the said protective film is an optical film in any one of Claims 1-3 and Claims 5-10. There is a polarizing plate.   A liquid crystal display device comprising the optical film according to claim 1 or the polarizing plate according to claim 11.   An IPS, OCB, or VA mode, comprising: a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein the polarizing plate is the polarizing plate according to claim 11. Liquid crystal display device. A VA mode liquid crystal display device comprising the polarizing plate according to claim 11 on a backlight side.

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