WO2006033468A1

WO2006033468A1 - Transparent film, optical compensation film, polarizing plate and liquid crystal display

Info

Publication number: WO2006033468A1
Application number: PCT/JP2005/018054
Authority: WO
Inventors: Shigeaki Nimura; Yosuke Nishiura
Original assignee: Fujifilm Corporation; Nishiura, Takako
Priority date: 2004-09-22
Filing date: 2005-09-22
Publication date: 2006-03-30
Also published as: JP2006117908A; TW200624958A

Abstract

A transparent film is provided. When the tanδ value is obtained by measuring the dynamic viscoelasticity of the transparent film in the machine direction or in the direction perpendicular to the machine direction at 0 to 120°C, the absolute value T1' of the maximum variation of the tanδ value per unit temperature is from 0 to 0.005. The retardation value Re in the film plane of the transparent film and the retardation value Rth in the film thickness direction of the transparent film satisfies the formulae specified in the specification.

Description

DESCRIPTION

TRANSPARENT FILM, OPTICAL COMPENSATION FILM, POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY

Technical Field

The present invention relates to a transparent film, and an optical compensation film, a polarizing plate and a liquid crystal display each using the transparent film.

Background Art

A liquid crystal display (LCD) includes a liquid crystal cell and a polarizing plate. The polarizing plate has a protective film and a polarizing film and is produced, for example, by dyeing a polarizing film including a polyvinyl alcohol with iodine, stretching the polarizing film, and stacking a protective film on both surfaces thereof. In the transmission liquid crystal display, this polarizing plate is disposed on both sides of a liquid crystal cell, and one or more optical compensation film is further disposed in some cases. In the reflective liquid crystal display, a reflector, a liquid crystal cell, one or more optical compensation film, and a polarizing plate are disposed in this order.

The liquid crystal cell includes a liquid crystalline molecule, two substrates for enclosing the liquid crystalline molecule therebetween, and an electrode layer for applying a voltage to the liquid crystalline molecule. The liquid crystal cell switches the ON or OFF display by utilizing difference in the aligned state of liquid crystalline molecules, and display modes such as TN (twisted nematic), IPS (in-plane switching), OCB (optically compensatory bend), VA (vertically aligned) and ECB (electrically controlled birefringence), which are applicable to both the transmissive liquid crystal display and the reflective liquid crystal display, have been proposed.

Among these LCD devices, a TN-mode liquid crystal display (90°-twisted nematic liquid crystal display) is suitable for uses where a high display grade is required. This TN mode uses a nematic liquid crystal molecule having a positive dielectric anisotropy and is driven by a thin-film transistor. The TN mode has viewing angle characteristics such that when viewed from the front, excellent display properties are exhibited, but when viewed from the oblique direction, the contrast may decrease or gradation reversal of reversing the brightness in the gradation display occurs and thereby, the display properties are worsened. In this point, improvement is strongly demanded.

In order to solve this problem, liquid crystal displays employing a so-called IPS (in-plane switching) mode of applying a lateral electric field to the liquid crystal or a VA (vertically aligned) mode of vertically aligning the liquid crystal having a negative dielectric anisotropy and dividing the alignment by a protrusion formed in the panel or by a slit electrode have been proposed and put into practical use. In recent years, such a panel is not limited to usage as a monitor of personal computers or the like, but its development as TV usage is proceeding and to cope with this, the brightness of screen has been greatly enhanced. In turn, slight light leakage in the oblique incident direction at a diagonal position, which has been heretofore not a problem in the above- described operation modes, is elicited as a cause of reduction in the display quality.

As one of means to improve this color tone or viewing angle of black display, in the case of IPS mode, studies are being made to dispose an optical compensatory material having birefringent property between the liquid crystal layer and the polarizing plate. For example, a technique of disposing a birefringent medium between the substrate and the polarizing plate, thereby improving the color when a white or halftone display is directly viewed from the oblique direction, has been disclosed, where the birefringent medium has an activity of compensating for the increase or decrease in the retardation of the liquid crystal layer at the inclination and the optical axes thereof are orthogonalized to each other (see, JP-A-9-80424). Also, a method using an optical compensation film comprising a styrene-based polymer or discotic liquid crystalline compound having a negative intrinsic birefringence has been proposed (see, JP-A-10- 54982, JP-A-11-202323 and JP-A-9-292522).

However, many of these proposed systems are a system of canceling the anisotropy of birefringence of the liquid crystal in the liquid crystal cell and thereby improving the viewing angle. Therefore, when the orthogonal polarizing plate is viewed from the oblique direction, light leakage due to slippage from the orthogonal angle made by crossed polarizing axes cannot be satisfactorily overcome. Even in the system demonstrated that this light leakage can be compensated for, it is very difficult to perfectly optically compensate for the liquid crystal cell without problem. This is because even if light leakage can be completely compensated for at a certain wavelength, compensation is not always attained at other wavelengths. For example, even when light-through is compensated at a green wavelength having a largest visual sensitivity, light leakage of blue at a smaller wavelength or red at a larger wavelength disadvantageous^ occurs. In order to solve this problem, Jpn. J. Appl. Phys. 41.. 4553 (2002) proposes to laminate two sheets of biaxial film.

However, the method of Jpn. J. Appl. Phys. 41.. 4553 (2002) has a problem that since two sheets of biaxial film are used, axial slippage of biaxial film and in turn unevenness of screen are readily generated. Also, one of causes of the light leakage at the black display is the fact that in the triacetyl cellulose film conventionally used as a polarizing plate protective film between the liquid crystal cell and the polarizer, the in- plane retardation Re is about 5 nm and the retardation Rth in the film thickness direction is about 50 nm. Therefore, it is demanded to develop a transparent film small in both the in-plane retardation Re and the retardation Rth in the film thickness direction, and use it as the polarizing plate protective film.

In recent years, the liquid crystal display is sometimes used at an elevated temperature due to internal backlight or in a high-temperature high-humidity environ¬ ment. According to this temperature or humidity, the triacetyl cellulose film as the polarizing plate protective film undergoes change in the Re and Rth, as a result, the optical compensating ability is changed to cause problems such as leakage of light at black display or generation of unevenness in the image. Particularly in such a case, due to the fact that the length of the display differs between length and breadth and in some cases, the member originally has different physical properties between vertical and transverse directions, there arise problems such as phenomenon that light leaks from the periphery of the display frame at the originally black display time, or trouble that the color tint changes. Therefore, it is demanded to develop a film capable of giving a liquid crystal display where such change in the optical compensating function due to the environment is reduced.

Disclosure of the Invention

A first object of an illustrative, non-limiting embodiment of the present invention is to provide a transparent film capable of giving a polarizing plate protective film in which the retardation Re in the film plane (sometimes referred to as "the in- plane retardation") and the retardation Rth in the film thickness direction are decreased and at the same time, these Re and Rth are less changed due to change in the environment such as temperature and humidity.

A second object of an illustrative, non-limiting embodiment of the present invention is to provide an optical compensation film and a polarizing plate each using the above-described transparent film, and provide an excellent liquid display free from light leakage and change in color tint even when the environment such as temperature and humidity (particularly temperature) is changed.

The present invention is as follows. 1. A transparent film, wherein an absolute value Tl¹ of the maximum variation of tanδ value per unit temperature in a range from 0 to 120°C is from 0 to 0.005, the tanδ value is a loss tangent obtained by measuring a dynamic viscoelasticity of the transparent film at a measuring frequency of 1 Hz, and a retardation value Re in a film plane of the transparent film and a retardation value Rth in a thickness direction of the transparent film satisfies formulae (i) and (ii): (i) 0<Re<20

(ii) |Rth|<25.

2. The transparent film as described in the above 1, wherein an absolute value T2¹ of the maximum variation of tanδ value per unit temperature in a range from 120 to 200°C is from 0.005 to 0.05, the tanδ value is a loss tangent obtained by measuring a dynamic viscoelasticity of the transparent film at a measuring frequency of 1 Hz. 3. The transparent film as described in the above 1 or 2, wherein a ratio of T2¹ to

Tl¹ is 2 or more. 4. The transparent film as described in any one of the above 1 to 3, wherein the tan δ value is a value obtained by measuring a dynamic viscoelasticity in one direction of a machine direction of the transparent film and a direction perpendicular to the machine direction.

5. The transparent film as described in any one of the above 1 to 4, wherein a peak value tanδ(md) of the tanδ value in a machine direction of the transparent film and a peak value tanδ(td) of the tanδ value in a direction perpendicular to the machine direction each is from 0.4 to 0.8, and the peak values tanδ(md) and tanδ(td) satisfy a relationship of 0.7<tan δ(md)/tan δ(td)<1.4.

6. The transparent film as described in any one of the above 1 to 5, which comprises a cellulose acylate.

7. The transparent film as described in any one of the above 1 to 6, which has at least one layer of a hard coat layer, an antiglare layer and an antireflection layer.

8. An optical compensation film comprising: a transparent film according to any one of the above 1 to 7; and an optically anisotropic layer, wherein a retardation value Re¹ in a plane of the optically anisotropic layer and a retardation value Rth¹ in a thickness direction of the optically anisotropic layer satisfies formula (iii): (iii) Re'=0 to 200 (nm) and |Rth'|=0 to 300 (nm).

9. The optical compensation film as described in the above 8, wherein the optically anisotropic layer is formed by using a discotic liquid crystalline compound. 10. The optical compensation film as described in the above 8 or 9, wherein the optically anisotropic layer is formed by using a rod-like liquid crystalline compound.

11. The optical compensation film as described in any one of the above 8 to 10, wherein the optically anisotropic layer comprises a polymer film having a birefringence.

12. The optical compensation film as described in the above 11, wherein the polymer film comprises at least one polymer material selected from the group consisting of polyamide, polyimide, polyester, polyether ketone, polyamideimide polyesterimide and polyarylether ketone.

13. A polarizing plate comprising: a polarizer; and a protective film comprising at least one of a transparent film according to any one of the above 1 to 7 and an optical compensation film according to any one of the above 8 to 12.

14. A liquid crystal display comprising at least one of a transparent film according to any one of the above 1 to 7, an optical compensation film according to any one of the above 8 to 12 and a polarizing plate according to the above 13. 15. The liquid crystal display as described in the above 14, which is a display of VA or IPS mode.

According to the present invention, a transparent film capable of giving a polarizing plate protective film in which the in-plane retardation Re and the retardation Rth in the film thickness direction are decreased and at the same time, these Re and Rth are less changed due to change in the environment such as temperature and humidity, can be provided. Also according to the present invention, an optical compensation film and a polarizing plate each using the above-described transparent film can be provided, and an excellent liquid display free from light leakage and change in color tint even when the environment such as temperature and humidity (particularly temperature) is changed, can be provided.

Brief Description of the Drawings

Fig. 1 is a schematic view of the IPS-mode liquid crystal display in which an illustrative, non-limiting embodiment of a transparent film of the present invention is disposed.

Fig. 2 is a schematic view of the VA-mode liquid crystal display in which an illustrative, non-limiting embodiment of a transparent film of the present invention is disposed. Detailed Description of the Invention

An Exemplary embodiment of a transparent film of the present invention can be suitably used as a transparent protective film for a polarizing plate which is a fundamental constituent member of a liquid crystal display. An Exemplary embodiment of a transparent film of the present invention is described in detail below. (Physical Properties of Transparent Film)

Physical properties of the transparent film of the present invention are described below. (Dynamic Viscoelasticity) In the transparent film of the present invention, the absolute value (Tl¹) of the maximum variation of tanδ value per unit temperature in the range from 0 to 120° C is from 0 to 0.005, preferably from 0 to 0.003, more preferably from 0 to 0.002.

This tanδ value is a value also called a loss tangent and defined by tanδ =

GVG" (G¹: storage modulus, G": loss modulus). The storage modulus (G') and loss modulus (G") of the transparent film are measured with a dynamic viscoelasticity meter

DVA-225 (manufactured by IT Keisoku Seigyo K.K.). In the present invention, the tanδ value is a value at a measuring frequency of 1 Hz.

In obtaining Tl', the temperature dispersion curve of tanδ value is determined from the storage modulus (G¹) and the loss modulus (G") obtained by using the above- described measuring meter, and the variation per unit temperature is calculated from the obtained temperature dispersion curve. The Tl' is obtained as an absolute value of the maximum variation of tan δ value in the range from 0 to 120°C.

The dynamic viscoelasticity is preferably performed in the machine direction or in the direction perpendicular to the machine direction. Tl¹ is preferably from 0 to 0.005 in both the machine direction and the direction perpendicular to the machine direction. The term "machine direction" as used in the present invention means the same direction as the film casting direction when the transparent film is produced by the solvent casting method described later, and in this case, the mechanical direction agrees with the longitudinal direction of the transparent film. When TT of the transparent film of the present invention is from 0 to 0.005, the thermal stability of the film is enhanced and the film can be reduced in the change of retardation due to change of environment such as temperature. The Tl' can be adjusted to the range from 0 to 0.005 by appropriately controlling, for example, the kind and amount added of the polymer constituting the transparent film of the present invention or the additive.

In a transparent film of the present invention, the absolute value (T2¹) of the maximum variation of tan δvalue per unit temperature in the range from 120 to 200°C is preferably from 0.005 to 0.05, more preferably from 0.007 to 0.05, still more preferably from 0.01 to 0.05. The dynamic viscoelasticity is preferably measured in the machine direction or in the direction perpendicular to the machine direction, and T2¹ is preferably from 0.005 to 0.05 in both the machine direction and the direction perpendicular to the machine direction.

When T2¹ is from 0 to 0.005, this is advantageous in that the film is easily handleable and the mechanical strength of the film is increased. The T2¹ can be adjusted to the range from 0.005 to 0.05 by appropriately controlling, for example, the kind of the polymer or the amount added of the additive.

The ratio (T2VT1¹) of T2¹ to Tl' is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more. Assuming that the peak value of tanδ in the machine direction is tanδ(md) and the peak value of tanδ in the direction perpendicular to the machine direction is tanδ(td), these tan δ(md) and tan δ(td) each is preferably adjusted to fall in the range from 0.4 to 0,8. The peak value of tanδ as used herein means a highest tanδ value on a tanδ- temperature (°C) absorption curve (temperature range: from 0 to 200°C). The peak values of tanδ can be made to fall in the above-described range by appropriately controlling the formulation of film, the conditions of production process, and the like.

The peak values of tanδ more preferably satisfy the relationship of 0.7<tanδ(md)/tanδ(td)<1.4. The range of tanδ(md)/tanδ(td) is more preferably from 0.8 to 1.3, still more preferably from 0.9 to 1.1. The tanδ(md)/tanδ(td) can be adjusted to fall in the above-described range by controlling the conditions of production process, particularly, the tension imposed on the film in the machine direction and the direction perpendicular to the machine direction at the film formation.

When the peak values of tanδ satisfy these conditions, this contributes to the enhancement of dimensional stability to moisture and heat and provides an effect of reducing the unevenness. (Storage Modulus (G¹))

In a transparent film of the present invention, the storage modulus in the machine direction and the storage modulus in the direction perpendicular to the machine direction both are preferably from 15,000 to 80,000 kgf/cm², and the ratio of storage modulus in the machine direction/storage modulus in the direction perpendicular to the machine direction is preferably from 0.80 to 1.20.

More preferably, the storage modulus is from 18,000 to 75,000 kgf/cm² in both the machine direction and the direction perpendicular thereto, and the ratio of storage modulus in the machine direction/storage modulus in the direction perpendicular to the machine direction is from 0.82 to 1.18. Still more preferably, the storage modulus is from 20,000 to 70,000 kgf/cm² in both the machine direction and the direction perpendicular thereto, and the ratio of storage modulus in the machine direction/storage modulus in the direction perpendicular to the machine direction is from 0.84 to 1.16. (Loss Modulus (G"))

In a transparent film of the present invention, the loss modulus in the machine direction and the loss modulus in the direction perpendicular to the machine direction both are preferably from 10 to 1,000 kgf/cm², and the ratio of loss modulus in the machine direction/loss modulus in the direction perpendicular to the machine direction

The loss modulus is more preferably from 10 to 500 kgf/cm², still more preferably from 10 to 200 kgf/cm², in both the machine direction and the direction perpendicular thereto. (Elongation Modulus) In a transparent film of the present invention, the elongation modulus in the machine direction is preferably from 240 to 500 kgf/mm², and the elongation modulus in the direction perpendicular to the machine direction is preferably from 230 to 480 kgf7mm². The ratio of elongation modulus in the machine direction/elongation modulus in the direction perpendicular to the machine direction is preferably from 0.80 to 1.36.

More preferably, the elongation modulus in the machine direction is from 250 to 480 kgf/cm², the elongation modulus in the direction perpendicular to the machine direction is from 240 to 470 kgf/mm², and the ratio of elongation modulus in the machine direction/elongation modulus in the direction perpendicular to the machine direction is from 0.85 to 1.30. Still more preferably, the elongation modulus in the machine direction is from 260 to 460 kgf/cm², the elongation modulus in the direction perpendicular to the machine direction is from 250 to 450 kgf7mm², and the ratio of elongation modulus in the machine direction/elongation modulus in the direction perpendicular to the machine direction is from 0.88 to 1.25. The elongation modulus can be determined by measuring the stress with an elongation of 0.5% at a tensile speed of 10%/min in an atmosphere of 23°C-70% with use of a universal tensile tester, STM T50BP, manufactured by Toyo Baldwin Co., Ltd. (Photoelastic Coefficient) In a transparent film of the present invention, the photoelastic coefficient in the machine direction and the photoelastic coefficient in the direction perpendicular to the machine direction both are preferably 5OxIO^"13 cm²/dyne or less, and the ratio of photoelastic coefficient in the machine direction/photoelastic coefficient in the direction perpendicular to the machine direction is preferably from 0.80 to 1.20. More preferably, the photoelastic coefficient in the machine direction and the photoelastic coefficient in the direction perpendicular to the machine direction both are 4OxIO^'13 cmVdyne or less, and the ratio of photoelastic coefficient in the machine direction/photoelastic coefficient in the direction perpendicular to the machine direction is from 0.82 to 1.18. Still more preferably, the photoelastic coefficient in the machine direction and the photoelastic coefficient in the direction perpendicular to the machine direction both are 3OxIO^'13 cm²/dyne or less, and the ratio of photoelastic coefficient in the machine direction/photoelastic coefficient in the direction perpendicular to the machine direction is from 0.84 to 1.16.

In determining the photoelastic coefficient, the transparent film sample (12 mm x 120 mm) of the present invention is applied with a tensile stress in the long axis direction, the retardation at this time is measured by an ellipsometer (Ml 50, manufactured by JASCO Corporation), and the photoelastic coefficient is calculated from the variation of retardation based on the stress. (Rate of Dimensional Change)

In a transparent film of the present invention, the rate of dimensional change after 24 hours at 60°C-90% RH and the rate of dimensional change after 24 hours at 90°C-dry each is preferably ±0.5% or less in both the machine direction and the direction perpendicular to the machine direction, and in each condition, the ratio of (rate of dimensional change in the machine direction)/(rate of dimensional change in the direction perpendicular to the machine direction) is preferably from 0.3 to 2.5.

More preferably, the rate of dimensional change after 24 hours at 60°C-90% RH and the rate of dimensional change after 24 hours at 90°C-dry each is ±0.4% or less in both the machine direction and the direction perpendicular to the machine direction, and in each condition, the ratio of (rate of dimensional change in the machine direction)/(rate of dimensional change in the direction perpendicular to the machine direction) is from 0.4 to 2.2.

The rate of dimensional change can be calculated as follows. Two sheets of the transparent film sample (30 mm x 120 mm) are prepared and subjected to humidity conditioning at 25°C-60% RH for 24 hours, 6 mmφ holes are punched at a distance of 100 mm, and this is defined as the original dimension (LO) of hole distance. The dimension (Ll) of hole distance after one sheet of sample is treated at 60°C-90% RH for 24 hours is measured, and the dimension (L2) of hole distance after another sheet of sample is treated at 90°C-5% RH for 24 hours is measured. In all cases, the rate of dimensional change as used in the present invention is a value when the distance is measured to a minimum scale, that is, 1/1,000 mm. The rate of dimensional change under each condition can be determined by the following formula: Rate (%) of dimensional change at 60°C-90% RH

= ((LO-Ll)ZLO) x 100 Rate (%) of dimensional change at 90°C-5% RH

= {(L0-L2)/L0}xl00 (Hygroscopic Expansion Coefficient) In a transparent film of the present invention, the hygroscopic expansion coefficient is preferably 30xl0^"5/% RH or less, more preferably 15xl0^"5/% RH, still more preferably 10xl0^"5/% RH. The hygroscopic expansion coefficient is preferably smaller but is usually 1.0xl0^'5/% RH or more. The hygroscopic expansion coefficient is preferably almost equal between the machine direction and the direction perpendicular to the machine direction.

The hygroscopic expansion coefficient represents the variation in the length of a sample when the relative humidity is changed at a constant temperature. By adjusting this hygroscopic expansion coefficient, when the transparent film is used as the optical compensation film support, the optical compensation film can be prevented from frame-like increase of transmittance (i.e., light leakage due to strain) while maintaining the optical compensating function. (Retardation Re in Film Plane)

In a transparent film of the present invention, the retardation Re in the film plane (the in-plane retardation Re) is 0≤Re<20, preferably 0<Re<15, more preferably 0<Re<10.

The retardation Re in the film plane can be adjusted to 0<Re<20 by appropriately controlling the kind and amount added of the polymer or additive in the film or by appropriately setting the temperature condition, time or the like in the process of producing the film. (Retardation Rth in Film Thickness Direction)

In a transparent film of the present invention, the retardation Rth in the film thickness direction (i.e., a direction perpendicular to the film plane) is |Rth|<25, preferably |Rth|<23, more preferably |Rth|≤20. The retardation Rth in the film thickness direction can be adjusted to |Rth|<25 by optimizing the polymer, additives and the like.

In the present invention, the in-plane retardation value Re of the transparent film is defined as a value when a sample (70 mm x 100 mm) is subjected to humidity conditioning at 25°C-60% RH for 2 hours and then measured from the direction perpendicular to the film plane (hereinafter, this direction is sometimes referred to as "a film normal direction") at a measuring wavelength of 589 nm by an automatic birefringence meter (K0BRA-21ADH, manufactured by Oji Test Instruments).

The retardation value Rth in the film thickness direction of the transparent film is a value calculated by an automatic birefringence meter KOBRA-21ADH, manufactured by Oji Test Instruments, based on retardation values measured totally in three directions, that is, the above-described Re, a retardation value measured when light at a wavelength of λ nm is caused to be incident from the direction inclined at

+40° with respect to the film normal direction by using the slow axis (judged by the automatic birefringence meter KOBRA-2 IADH) as the inclination axis (rotation axis), and a retardation value measured when light at a wavelength λ nm is caused to be incident from the direction inclined at -40° with respect to the film normal direction by using the slow axis as the inclination axis (rotation axis).

Incidentally, nx, ny, nz, Re and Rth can be calculated by inputting the average refractive index (in the case of cellulose acylate, 1.48) and the film thickness d into an automatic birefringence meter, KOBRA 21ADH. Here, nx is a refractive index in the slow axis direction in the film plane, ny is a refractive index in the fast axis direction in the film plane, and nz is a refractive index in the film thickness direction.

As for the average refractive index, the catalogue values of various optical films described in Polymer Handbook. John Wiley & Sons, Inc. can be used. Main optical films with its average refractive index are cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) and polystyrene (1.59). In the case of an optical film of which average refractive index is not known, the average refractive index can be measured by an Abbe refractometer. (Light Leakage and Change of Color Tint on Panel due to Change in Humidity or Temperature of Polarizing Plate)

A transparent film of the present invention can be suitably used as a transparent protective film of a polarizer for liquid crystal displays. By mounting the transparent film of the present invention on a liquid crystal display, even when the temperature is elevated due to backlight inside the device or the device is used in a high-temperature high-humidity environment, an unevenness failure of causing light leakage from the periphery of the display frame or a trouble of bringing about change in the color tint particularly at the black display time where the entire screen should be originally black- displayed can be decreased as compared with conventional protective films for the polarizing plate. These failures or troubles are preferably null. (Thickness)

The thickness of the transparent film of the present invention is preferably from 20 to 200 μm, more preferably from 40 to 180 μm. (Production Method of Transparent Film) A transparent film of the present invention may be film-formed by heat- melting a thermoplastic polymer resin or by a solution film-forming method (solvent casting method) from a solution having uniformly dissolved therein a polymer, but the film is preferably produced by a solvent casting method. The solvent casting method is described below. (Method for Producing Film by Solvent Casting Method)

For producing a transparent film by using a solvent casting method, a solution (dope) is first prepared by dissolving a polymer as the film raw material in an appropriate organic solvent, the dope is cast on an appropriate support (preferably a metal support), the solvent is then dried, the film when gelled is stripped off from the support, and the solvent is thoroughly dried from the film, thereby forming a transparent film.

(Metal Support)

As for the endlessly traveling metal support for use in the production of a transparent film of the present invention, a drum with the surface being mirror-finished by chromium plating or a stainless steel belt (band) mirror-finished by surface polishing is used. In order to obtain a support with smooth surface, a material having less impurities is thoroughly polished to have a mirror surface in a clean environment from which foreign matters and the like are removed as much as possible. For example, the support surface is treated to have a center line average roughness Ra of 1 to 3 nm as described in JP-A-2000-84960, whereby roughening of the film surface or increase in the film cloudiness (haze value) is prevented. The smoothness of the film formed by such a solution casting film-forming method is higher as the support surface has less foreign matters or irregularities. The methods for casting and drying in the solvent casting method are described in U.S. Patents 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069 and 2,739,070, British Patents 640,731 and 736,892, JP-B-45-4554, JP-B-49-5614, JP- A-60- 176834, JP-A-60-203430 and JP-A-62- 115035. The dope is preferably cast on a drum or band of which surface temperature is 30°C or less. Particularly, the temperature of the metal support is preferably from - 40 to 4O⁰C. A method of using a drum is preferred because the film formation speed can be increased, and in this case, the temperature of the metal support is preferably from 0 to -40°C. (Residual Solvent Amount at Stripping)

At the time of stripping the film, the residual solvent amount in the film is preferably from 60 to 300%. The residual solvent amount is represented by the following formula. Incidentally, the weight of residual volatile matter is a value obtained by subtracting the film weight after heat treatment from the film weight before heat treatment when the film is heat-treated at 120°C for 2 hours. Residual solvent amount = weight of residual volatile matter/film weight after heat treatment x 100 (%) (Tension Imposed at Conveyance of Film) In the drying step after stripping from the support, the film generally undergoes shrinkage in the width direction (direction perpendicular to the machine direction) due to evaporation of the solvent. In the production of a transparent film of the present invention, it is preferred to effect control such that the film is not strongly stretched in either the machine direction or the direction perpendicular thereto. More specifically, at the conveyance of the film in the machine direction, the tension imposed in the machine direction of the film from the film-conveying roll is preferably adjusted to a strength of 10 to 50 kgf/m. The tension imposed in the direction perpendicular to the machine direction is also preferably adjusted to the same strength. In this case, a tenter system of holding the film in the perpendicular direction and using tenter clips for adjusting the tension can also be preferably used. For example, a method (tenter system) disclosed in JP-A-62-46625 of drying the web while keeping the width by nipping both ends in the width direction with clips in the entire or partial process of the drying step can be preferably used. (Construction Material of Transparent Film) A material for forming a transparent film of the present invention is preferably a polymer excellent in the optical performance, transparency, mechanical strength, thermal stability, moisture blocking property, isotropy and the like and as long as the above-described Re and Rth satisfy formulae (i) and (ii), any material may be used. Examples thereof include a polycarbonate-based polymer, a polyester-based polymer such as polyethylene terephthalate and polyethylene naphthalate, an acryl-based polymer such as polymethyl methacrylate, and a styrene-based polymer such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Other examples include a polyolefin such as polyethylene and polypropylene, a polyolefin-based polymer such as ethylene-propylene copolymer, a vinyl chloride-based polymer, an amide-based polymer such as nylon and aromatic polyamide, an imide-based polymer, a sulfone- based polymer, a polyethersulfone-based polymer, a polyether ether ketone-based polymer, a polyphenylene sulfide-based polymer, a vinylidene chloride-based polymer, a vinyl alcohol-based polymer, a vinyl butyral-based polymer, an arylate-based polymer, a polyoxymethylene-based polymer, an epoxy-based polymer and a polymer obtained by mixing these polymers. A transparent film of the present invention can also be formed as a cured layer of a ultraviolet-curable or heat-curable resin such as acryl type, urethane type, acrylurethane type, epoxy type and silicone type.

Also, a thermoplastic norbornene-based resin can be preferably used as the material of forming the transparent film of the present invention. Examples of the thermoplastic norbornene-based resin include Zeonex and Zeonoah produced by Zeon Corp., and Arton produced by JSR.

Furthermore, a cellulose-based polymer (hereinafter referred to as a "cellulose acylate") which has been conventionally used as the transparent protective film for a polarizing plate can also be preferably used as the material of forming the transparent film of the present invention. Representative examples of the cellulose acylate include triacetyl cellulose. The cellulose acylate is described in detail below. (Raw Material Cotton of Cellulose Acylate)

Examples of the cellulose as the raw material of cellulose acylate used for a transparent film of the present invention include cotton linter and wood pulp (e.g., hardwood pulp, softwood pulp). A cellulose acylate obtained from any raw material cellulose may be used and depending on the case, the raw material celluloses may be mixed. These raw material celluloses are described in detail, for example, in Maruzawa and Uda, Plastic Zairyo Koza (17). Seni-kei Jushi (Plastic Material Lecture (17). Fiber-Based Resin). Nikkan Kogyo Shinbun Sha (1970), and JIII Journal of Technical Disclosure. No. 2001-1745, pp. 7-8, Japan Institute of Invention and Innovation, and celluloses described therein can be used. (Cellulose Acylate Substitution Degree)

The cellulose acylate is resulting from acylation of the hydroxyl group of cellulose, and the substituent may be any acyl group having a carbon atom number of 2 (acetyl group) to 22. In the cellulose acylate, the substitution degree to the hydroxyl group of cellulose is not particularly limited but is preferably from 2.50 to 3.00, more preferably from 2.75 to 3.00, still more preferably from 2.85 to 3.00. In determining the substitution degree to the hydroxyl group of cellulose, the bonding degree of acetic acid and/or fatty acid having a carbon atom number of 3 to 22 substituted to the hydroxyl group of cellulose is measured and the substitution degree is obtained by calculation. As for the measurement of bonding degree, the method according to ASTM D-817-91 may be used. Out of the acetic acid and/or fatty acid having a carbon atom number of 3 to 22 substituted to the hydroxyl group of cellulose, the acyl group having a carbon atom number of 2 to 22 is not particularly limited and may be an aliphatic group or an allyl group or may be a single acyl group or a mixture of two or more acyl groups. Examples thereof include an alkylcarbonyl ester of cellulose, an alkenylcarbonyl ester of cellulose, an aromatic carbonyl ester of cellulose, and an aromatic alkylcarbonyl ester of cellulose, and these esters each may further have a substituted group. Preferred examples of the acyl group therefor include an acetyl group, a propionyl group, a butanoyl group, a heptanoyl group, a hexanoyl group, an octanoyl group, a decanoyl group, a dodecanoyl group, a tridecanoyl group, a tetradecanoyl group, a hexadecanoyl group, an octadecanoyl group, an iso-butanoyl group, a tert-butanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group and a cinnamoyl group. Among these, preferred are acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, tert-butanoyl, oleoyl, benzoyl, naphthylcarbonyl and cinnamoyl, and more preferred are acetyl, propionyl and butanoyl. In the case where the acyl substituent substituted to the hydroxyl group of cellulose is substantially two kinds of substituents selected from an acetyl group, a propionyl group and a butanoyl group, the entire substitution degree is preferably from 2.50 to 3.00, because the optical anisotropy of the cellulose acylate film can be decreased. In this case, the acyl substitution degree is more preferably from 2.60 to 3.00, still more preferably from 2.65 to 3.00. (Polymerization Degree of Cellulose Acylate)

The polymerization degree of the cellulose acylate is, in terms of the viscosity average polymerization degree, preferably from 180 to 700, and in the case of using a cellulose acetate, more preferably 180 to 550, still more preferably from 180 to 400, yet still more preferably from 180 to 350. If the polymerization degree is too high, the dope solution of cellulose acylate is elevated in the viscosity and the film can be hardly produced by casting, whereas if the polymerization degree is too low, the strength of the produced film may decrease. The average polymerization degree can be measured according to the limiting viscosity method by Uda, et al. (Kazuo Uda and Hideo Saito, JOURNAL OF THE SOCIETY OF FIBER SCIENCE AND TECHNOLOGY. JAPAN. Vol. 18, No. 1, pp. 105-120 (1962)). Furthermore, this is described in detail in JP-A- 9-95538.

The cellulose acylate particularly preferred as a transparent film of the present invention is a cellulose acylate in which the acyl substituent substantially containing only an acetyl group and the average polymerization degree is from 180 to 550. By using such a cellulose acylate, the optical anisotropy can be decreased.

The molecular weight distribution of the cellulose acylate can be evaluated by the gal permeation chromatography and it is preferred that the polydispersity index Mw/Mn (Mw is a mass (weight) average molecular weight, and Mn is a number average molecular weight) is small and the molecular weight distribution is narrow. The specific value of Mw/Mn is preferably from 1.0 to 3.0, more preferably from 1.0 to 2.0, and most preferably from 1.0 to 1.6.

The cellulose acylate having a small low molecular component content is useful because the viscosity is lower than normal cellulose acylates, though the average molecular weight (polymerization degree) is high. The cellulose acylate having a small low molecular component content can be obtained by removing low molecular components from a cellulose acylate synthesized through a normal process. The low molecular components can be removed by washing the cellulose acylate with an appropriate organic solvent. In the case of producing a cellulose acylate having a small low molecular component content, the amount of the sulfuric acid catalyst in the acetylation reaction is preferably adjusted to 0.5 to 25 parts by mass (weight) per 100 parts by mass (weight) of the cellulose. When the amount of the sulfuric acid catalyst is adjusted to this range, a cellulose acylate advantageous also in view of the molecular weight distribution (uniform molecular weight distribution) can be synthesized.

The water content of the cellulose acylate is preferably 2 mass% (weight%) or less, more preferably 1 mass% or less, still more preferably 0.7 mass% or less. In general, the cellulose acylate contains water and the water content thereof is known to be from 2.5 to 5 mass%. In order to reduce the water content of the cellulose acylate as above, the cellulose acylate is preferably dried and the method therefor is not particularly limited as long as the objective water content can be attained.

The preparation method of such a cellulose acylate is described in detail in JIII Journal of Technical Disclosure. No. 2001-1745, pp. 7-12, Japan Institute of Invention and Innovation (March 15, 2001).

Also, either a single cellulose acylate or a mixture of two or more cellulose acylates may be used as long as the substituent, substitution degree, polymerization degree, molecular weight distribution and the like are in respective ranges described above. (Additives to Transparent Film)

In the production stage of a transparent film of the present invention, various additives can be added. Examples of the additive include a compound of decreasing the optical anisotropy, a wavelength dispersion adjusting agent, an ultraviolet inhibitor, a plasticizer, a deterioration inhibitor, a fine particle and an optical property adjusting agent. The timing of adding the additives is not particularly limited, but when the transparent film is film-formed by heat-melting a thermoplastic resin, the additives may be added at the heat-melting. In the case of film-forming the transparent film by a solution film-forming method (solvent casting method) from a solution having uniformly dissolved therein the polymer, the additives can be added in the step of producing the polymer solution (hereinafter referred to as a "dope"). In this case, a step of adding the additives and preparing the dope may be provided as the final preparation step in the dope preparation step. (Compound of Decreasing Optical Anisotropy of Transparent Film) As for the additive used in a transparent film of the present invention, a compound of decreasing the optical anisotropy can be used.

By containing this compound of decreasing the optical anisotropy, the optical anisotropy can be satisfactorily decreased with use of a compound of preventing the polymer in the film from aligning in the plane and in the film thickness direction, and both Re and Rth can be made to come close to zero. It is advantageous for the compound of decreasing the optical anisotropy that the compound has sufficiently high compatibility with the polymer and the compound itself does not have a rod-like structure or a planar structure. More specifically, in the case of having a plurality of planar functional groups like aromatic group, a structure where these functional groups do not have the same planarity but have non-planarity is advantageous.

A transparent film of the present invention preferably contains at least one compound of decreasing the optical anisotropy in the range of satisfying the following formulae (1) and (b):

(a) (Rth(A)-Rth(0))/A<-1.0 (b) 0.01≤A<30.

Formulae (a) and (b) are preferably

(al) (Rth(A)-Rth(0))/A≤-2.0 (bl) 0.05<A<25, more preferably (a2) (Rth(A)-Rth(0))/A<-3,0

(b2) 0.1<A<20.

In the formulae, Rth(A) represents Rth in nm of the transparent film that contains a compound of decreasing Rth in an amount of A%, Rth(O) represents Rth in nm of the transparent film that contains no compound of decreasing Rth, and A represents a mass (%) of the compound of decreasing Rth when the mass of the raw material polymer of the film is taken as 100.

Specific examples of the compound of decreasing the optical anisotropy, which is preferably used in the present invention, include the compounds represented by the following formulae (1) to (4) but are not limited to these compounds.

The compounds of formulae (1) and (2) are described below. , Formula (1):

Formula (2):

In formula (1), R^la represents an alkyl group or an aryl group, R^2a and R^3a each independently represents a hydrogen atom, an alkyl group or an aryl group, the total number of carbon atoms in R^la, R^2a and R^3a is preferably 10 or more, and the alkyl group and the aryl group of R^la, R^2a and R^3a each may have a substituent. In formula (2), R^4a and R^5a each independently represents an alkyl group or an aryl group, the total number of carbon atoms in R^4a and R^5a is preferably 10 or more, and the alkyl group and the aryl group each may have a substituent.

The substituent of the alkyl or aryl group is preferably a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group or a sulfonamide group, more preferably an alkyl group, an aryl group, an alkoxy group, a sulfone group or sulfonamide group. The alkyl group may be linear, branched or cyclic and preferably an alkyl group having a carbon atom number of 1 to 25, more preferably from 6 to 25, still more preferably from 6 to 20 (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, amyl, isoamyl, tert-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclooctyl, nonyl, adamantyl, decyl, tert-octyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl). The acryl group is preferably an aryl group having a carbon atom number of 6 to 30, more preferably from 6 to 24 (e.g., phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, triphenylphenyl).

Preferred examples of the compounds represented by formulae (1) and (2) are set forth below, but the present invention is not limited to these specific examples.

U-C₆H₁₃

A-4 A-5 A-6

A-IO A-I l

A-14 A-15

A-17 A-18 A-19

A-20 A-21 A-22

A-30 A-31

A-32 A-33

A-39

25

A-43 A-44 A-45

B-4 -5 -6

B-32 B-33

B-34 B-35

The compound of formula (3) is described below. Formula (3):

, 3d

O R-¹

Id , 2d

R- -C— N— R wherein R represents an alkyl group or an aryl group, R and R each independently represents a hydrogen atom, an alkyl group or an aryl group, and the alkyl group an the

28 aryl group each may have a substituent.

Among the compounds of formula (3), preferred are the compounds represented by the following formula (4): Formula (4):

O R^6d R^4d— C— N— R^5d wherein R^4d, R^5d and R^6d each independently represents an alkyl group or an aryl group. The aryl group may be linear, branched or cyclic and is preferably an alkyl group having a carbon atom number of 1 to 20, more preferably from 1 to 15, and most preferably from 1 to 12. The cyclic alkyl group is preferably a cyclohexyl group, and the aryl group is preferably an aryl group having a carbon atom number of 6 to 36, more preferably from 6 to 24.

The alkyl group and the aryl group each may have a substituent and the substituent is preferably a halogen atom (e.g., chlorine, bromine, fluorine, iodine), an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a sulfonylamino group, a hydroxy group, a cyano group, an amino group or an acylamino group, more preferably a halogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a sulfonylamino group or an acylamino group, still more preferably an alkyl group, an aryl group, a sulfonylamino group or an acylamino group. Preferred examples of the compounds represented by formulae (3) and (4) are set forth below, but the present invention is not limited to these specific examples.

FA-I FA-2 FA-3

FA-4 FA-5 FA-6

FA-Il FA- 12

FA-23 FA-24

FB-Il FB- 12

FB- 17 FB-18

FB- 19 FB-20

FB-21 FB-22

FB-23 FB-24

FC-I FC-2 FC-3

FC-4 FC-5 FC-6

FC-7 FC-8

FC-I l FC- 12

FC-18 FC-19

FC-20 FC-21

FC-22 FC-23

FC-24 FC-25

FD-I FD-2 FD-3

FD-4 FD-5

FD-6 FD-7

(Wavelength Dispersion Adjusting Agent)

A transparent film of the present invention preferably has small dependency of Re and Rth on the wavelength, that is, small wavelength dispersion. For decreasing the wavelength dispersion, it is effective in the present invention to add a compound of adjusting the wavelength dispersion (hereinafter sometimes referred to as a "wavelength dispersion adjusting agent") to the transparent film.

The wavelength dispersion adjusting agent is preferably a compound of decreasing the wavelength dispersion ΔRth^r=|Rth(400)-Rth(700)| of Rh, represented by the following formula (c), and a transparent film of the present invention preferably contains at least one of such compounds in the range of satisfying the following formulae (d) and (e): (c) ΔRth=|Rth(400)-Rth(700)|

(d) (ΔRth(B)-ΔTh(0))/B<-2.0

(e) 0.01<B<30 Formulae (c) and (d) are preferably

(cl) (ΔRth(B)-ΔRth(0))/B<-3.0 (dl) 0.05<B<25, more preferably

(c2) (ΔRth(B)-ΔRth(0))/B<-4.0 (d2) 0.1<B<20.

In the formulae, Rth(400) and Rth(700) are Rth(nm) at a measurement wavelength of 400 nm and 700 nm, respectively.

ΔRth(B) is ΔRth(nm) of a film containing B mass% of a compound added as the wavelength dispersion adjusting agent, ΔRth(0) is ΔRth(nm) of a film not containing the compound, and B is a mass (%) of the compound when the mass of the raw material polymer of the film is taken as 100. As for the wavelength dispersion adjusting agent, a compound having a wavelength dispersion opposite to the wavelength dispersion of the raw material polymer constituting the film is preferably used.

In the case of using a polymer having a large wavelength dispersion on the long wavelength side as in cellulose acylate which is preferably used in the present invention, the wavelength dispersion adjusting agent is more preferably a compound having absorption in the ultraviolet region of 200 to 400 nm and decreasing ΔRe=|Re(400)-Re(700)| and ΔRth=|Rth(400)-Rth(700)|, and by containing at least one of such compounds, the wavelength dispersion of Re and Rth of the optical film can be more effectively adjusted. Here, Re(400) and Re(700) are Re(nm) at a measurement wavelength of 400 nm and 700 nm, respectively.

A transparent film generally has wavelength dispersion characteristics such that the Re and Rth values are larger on the long wavelength side than on the short wavelength side. Accordingly, it is demanded to smooth the wavelength dispersion by making relatively large the Re and Rth on the short wavelength side. On the other hand, the compound having absorption in the ultraviolet region of 200 to 400 nm has wavelength dispersion characteristics such that the absorbancy is larger on the long wavelength side than on the short wavelength side. When this compound itself is isotropically present inside the transparent film, the birefringence of the compound itself and in turn the wavelength dispersion of Re and Rth are expected to be, similarly to the wavelength dispersion of absorbancy, larger on the short wavelength side.

Accordingly, by using the above-described compound having absorption in the ultraviolet region of 200 to 400 nm, in which the Re and Rth of the compound itself are expected to be larger on the short wavelength side, the wavelength dispersion of Re and Rth of the transparent can be adjusted. For this purpose, the compound of adjusting the wavelength dispersion must be satisfactorily and uniformly compatibilized with the polymer solid content. The absorption band of such a compound in the ultraviolet region is preferably from 200 to 400 nm, more preferably from 220 to 395 nm, still more preferably from 240 to 390 nm. Recently, in a liquid crystal display used for televisions, laptop computers, mobile-type personal digital assistance and the like, the optical members used for the liquid crystal display are demanded to have excellent transmittance so as to elevate the brightness with a smaller electric power. Therefore, in the case of adding the wavelength dispersion adjusting agent to the transparent film, a compound having excellent spectral transmittance is preferably used. As for the spectral transmittance of the wavelength dispersion adjusting agent, the spectral transmittance at a wavelength of 380 nm is preferably from 45 to 95%, and the spectral transmittance at a wavelength of 350 nm is preferably 10% or less.

The wavelength dispersion adjusting agent is preferably not vaporized in the process of casting the dope and drying the film at the production of the transparent film and therefore, the molecular weight thereof is preferably from 250 to 1,000, more preferably from 260 to 800, still more preferably from 270 to 800, yet still more preferably from 300 to 800. As long as the molecular weight is in this range, the compound may have a specific monomer structure or may have an oligomer or polymer structure where a plurality of the monomer units are bonded.

The amount of the wavelength dispersion adjusting agent added is preferably from 0.01 to 30 wt%, more preferably from 0.1 to 20 wt%, still more preferably from

0.2 to 10 wt One of these wavelength dispersion adjusting agents may be used alone, or two or more of the compounds may be mixed at an arbitrary ratio and used.

Specific examples of the wavelength dispersion adjusting agent which is suitably used in the present invention include a benzotriazole-based compound, a benzophenone-based compound, a cyano group-containing compound, an oxybenzophenone-based compound, a salicylic acid ester-based compound and a nickel complex salt-based compound, but the present invention is not limited to these compounds.

The benzotriazole-based compound is preferably a compound represented by the following formula (101): Formula (101):

(wherein Q¹ represents a nitrogen-containing aromatic heterocyclic ring and Q² represents an aromatic ring).

Ql is a nitrogen-containing aromatic heterocyclic ring, preferably a 5-, 6- or 7- membered nitrogen-containing aromatic heterocyclic ring, more preferably a 5- or 6- membered nitrogen-containing aromatic heterocyclic ring (e.g., imidazole, pyrazole, triazole, tetrazole, thiazole, oxazole, selenazole, benzotriazole, benzothiazole, benzoxazole, benzoselenazole, thiadiazole, oxadiazole, naphthothiazole, naphthoxazole, azabenzimidazole, purine, pyridine, pyrazine, pyrimidine, pyridazine, triazine, triazaindene, tetrazaindene), still more preferably a 5-membered nitrogen-containing aromatic heterocyclic ring (specifically, imidazole, pyrazole, triazole, tetrazole, thiazole, oxazole, benzotriazole, benzothiazole, benzoxazole, thiadiazole or oxadiazole), and yet still more preferably benzotriazole. The nitrogen-containing aromatic heterocyclic ring represented by Q¹ may further have a substituent and as for the substituent, the substituent T described later can be applied. When a plurality of substituents are present, respective substituents may be annelated to further form a ring.

The aromatic ring represented by Q² is not particularly limited and may be either an aromatic hydrocarbon ring or an aromatic heterocyclic ring but is preferably an aromatic hydrocarbon ring. Also, the aromatic ring may be a monocyclic ring or may form a condensed ring with another ring.

The aromatic hydrocarbon ring is preferably a monocyclic or bicyclic aromatic hydrocarbon ring having from 6 to 30 carbon atoms (e.g., benzene rig, naphthalene ring), more preferably an aromatic hydrocarbon ring having from 6 to 20 carbon atoms, still more preferably an aromatic hydrocarbon ring having from 6 to 12 carbon atoms, yet still more preferably a naphthalene ring or a benzene ring, and most preferably a benzene ring.

The aromatic heterocyclic ring is not particularly limited but is preferably an aromatic heterocyclic ring containing a nitrogen atom or a sulfur atom. Specific examples of the aromatic heterocyclic ring include thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiazole, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline, phthalazine, naphthylidine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzothiazole, benzotriazole and tetrazaindene. Among these, pyridine, triazine and quinoline are preferred.

Q² may further have a substituent and the substituent is preferably the substituent T described later. Examples of the substituent T include an alkyl group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, still more preferably from 1 to 8 carbon atoms, e.g., methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n- hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 12 carbon atoms, still more preferably from 2 to 8 carbon atoms, e.g., vinyl, allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 12 carbon atoms, still more preferably from 2 to 8 carbon atoms, e.g., propargyl, 3- pentynyl), an aryl group (preferably having from 6 to 30 carbon atoms, more preferably from 6 to 20 carbon atoms, still more preferably from 6 to 12 carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), a substituted or unsubstituted amino group (preferably having from 0 to 20 carbon atoms, more preferably from 0 to 10 carbon atoms, still more preferably from 0 to 6 carbon atoms, e.g., amino, methylamino, dimethylamino, diethylamino, dibenzylamino), an alkoxy group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, still more preferably from 1 to 8 carbon atoms, e.g., methoxy, ethoxy, butoxy), an aryloxy group (preferably having from

6 to 20 carbon atoms, more preferably from 6 to 16 carbon atoms, still more preferably from 6 to 12 carbon atoms, e.g., phenyloxy, 2-naphthyloxy), an acyl group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., acetyl, benzoyl, formyl, pivaloyl), an alkoxycarbonyl group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms, still more preferably from 2 to 12 carbon atoms, e.g., methoxycarbonyl, ethoxycarbonyl), an aryloxycarbonyl group (preferably having from

7 to 20 carbon atoms, more preferably from 7 to 16 carbon atoms, still more preferably from 7 to 10 carbon atoms, e.g., phenyloxycarbonyl), an acyloxy group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms, still more preferably from 2 to 10 carbon atoms, e.g., acetoxy, benzoyloxy), an acylamino group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms, still more preferably from 2 to 10 carbon atoms, e.g., acetylamino, benzoylamino), an alkoxycarbonylamino group (preferably having from 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms, still more preferably from 2 to 12 carbon atoms, e.g., methoxycarbonylamino), an aryloxycarbonylamino group (preferably having from 7 to 20 carbon atoms, more preferably from 7 to 16 carbon atoms, still more preferably from 7 to 12 carbon atoms, e.g., phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., methanesulfonylamino, benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 20 carbon atoms, more preferably from 0 to 16 carbon atoms, still more preferably from 0 to 12 carbon atoms, e.g., sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., methylthio, ethylthio), an arylthio group (preferably having from 6 to 20 carbon atoms, more preferably from 6 to 16 carbon atoms, still more preferably from 6 to 12 carbon atoms, e.g., phenylthio), a sulfonyl group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., mesyl, tosyl), a sulfmyl group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., methanesulfinyl, benzenesulfinyl), a ureido group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., ureido, methylureido, phenylureido), a phosphoric acid amide group (preferably having from 1 to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g., diethylphosphoric acid amide, phenylphosphoric acid amide), a hydroxy group, a mercapto group, a halogen atom (e.g., fluorine, chlorine, bromine, iodine), a cyano group, a sulfo group, a carboxyl group, a nitro group, a hydroxamic acid group, a sulfino group, a hydrazino group, an imino group, a heterocyclic group (preferably having from 1 to 30 carbon atoms, more preferably from 1 to 12 carbon atoms; examples of the heteroatom include a nitrogen atom, an oxygen atom and a sulfur atom; specific examples of the heterocyclic group include imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl and benzothiazolyl), and a silyl group (preferably having from 3 to 40 carbon atoms, more preferably from 3 to 30 carbon atoms, still more preferably from 3 to 24 carbon atoms, e.g., trimethylsilyl, triphenylsilyl).

These substituents each may be further substituted. When two or more substituents are present, the substituents may be the same or different and, if possible, may combine with each other to form a ring.

The compound of formula (101) is preferably a compound represented by the following formula (101 -A): Formula (101-A):

(wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently represents a hydrogen atom or a substituent).

R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently represents a hydrogen atom or a substituent and as for the substituent, the substituent T can be applied. The substituent may be further substituted by another substituent, and the substituents may be annelated with each other to form a cyclic structure.

R¹ and R³ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or an alkyl group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

R² and R⁴ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or an alkyl group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom. R⁵ and R⁸ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or an alkyl group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

R⁶ and R⁷ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or a halogen atom, yet still more preferably a hydrogen atom or a chlorine atom.

The compound of formula (101) is more preferably a compound represented by the following formula (101 -B): Formula (101-B):

(wherein R¹, R³, R⁶ and R⁷ have the same meanings as in formula (101-A) and preferred ranges are also the same).

Specific examples of the compound represented by formula (101) are set forth below, but the present invention is not limited to these specific examples.

UV-Il UV-18

UV-12

Among these benzotriazole-based compounds, when the transparent film is produced without containing a compound having a molecular weight of 320 or less, this is advantageous in view of retentivity.

The benzophenone-based compound used as the wavelength dispersion adjusting agent is preferably a compound represented by the following formula (102): Formula (102):

(wherein Q¹ and Q² each independently represents an aromatic ring and X represents Ml (R represents a hydrogen atom or a substituent), an oxygen atom or a sulfur atom). The aromatic ring represented by Q¹ and Q² may be either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. Also, the aromatic ring may be a monocyclic ring or may form a condensed ring with another ring.

The aromatic hydrocarbon ring represented by Q¹ and Q² is preferably a monocyclic or bicyclic aromatic hydrocarbon ring (preferably having from 6 to 30 carbon atoms) (e.g., benzene rig, naphthalene ring), more preferably an aromatic hydrocarbon ring having from 6 to 20 carbon atoms, still more preferably an aromatic hydrocarbon ring having from 6 to 12 carbon atoms, yet still more preferably a naphthalene ring or a benzene ring, and most preferably a benzene ring.

The aromatic heterocyclic ring represented by Q¹ and Q² is preferably an aromatic heterocyclic ring containing at least one of an oxygen atom, a nitrogen atom and a sulfur atom. Specific examples of the heterocyclic ring include furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiazole, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline, phthalazine, naphthylidine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzothiazole, benzotriazole and tetrazaindene. The aromatic heterocyclic ring is preferably pyridine, triazine or quinoline. The aromatic ring represented by Q¹ and Q² is preferably an aromatic hydrocarbon ring, more preferably an aromatic hydrocarbon ring having from 6 to 10 carbon atoms, still more preferably a substituted or unsubstituted benzene ring.

Q¹ and Q² each may further have a substituent and the substituent is preferably the substituent T, but a carboxylic acid, a sulfonic acid and a quaternary ammonium salt are not included in the substituent. If possible, the substituents may combine with each other to form a cyclic structure.

X represents NR (R represents a hydrogen atom or a substituent; as for the substituent, the substituent T can be applied), an oxygen atom or a sulfur atom. When X is NR, R is preferably an acyl group or a sulfonyl group and this substituent may be further substituted. X is preferably NR or an oxygen atom, more preferably an oxygen atom.

The compound of formula (102) is preferably a compound represented by the following formula (102-A); Formula (102-A):

(wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independently represents a hydrogen atom or a substituent).

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independently represents a hydrogen atom or a substituent and as for the substituent, the substituent T can be applied. The substituent may be further substituted by another substituent, and the substituents may be annelated with each other to form a cyclic structure.

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or an alkyl group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

R² is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an amino group having from 0 to 20 carbon atoms, an alkoxy group having from 1 to 12 carbon atoms, an aryloxy group having from 6 to 12 carbon atoms or a hydroxy group, still more preferably an alkoxy group having from 1 to 20 carbon atoms, yet still more preferably an alkoxy group having from 1 to 12 carbon atoms.

R⁷ is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an amino group having from 0 to 20 carbon atoms, an alkoxy group having from 1 to 12 carbon atoms, an aryloxy group having from 6 to 12 carbon atoms or a hydroxy group, still more preferably a hydrogen atom or an alkyl group having from 1 to 20 carbon atoms (preferably an alkyl group having from 1 to 12 carbon atoms, more preferably an alkyl group having from 1 to 8 carbon atoms, still more preferably a methyl group), yet still more preferably a methyl group or a hydrogen atom.

The compound of formula (102) is more preferably a compound represented by the following formula (102-B): Formula (102-B):

(wherein R . 10 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group or a substituted or unsubstituted aryl group).

R¹⁰ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group or a substituted or unsubstituted aryl group, and as for the substituent, the substituent T can be applied.

R¹⁰ is preferably a substituted or unsubstituted alkyl group, more preferably a substituted or unsubstituted alkyl group having from 5 to 20 carbon atoms, still more preferably a substituted or unsubstituted alkyl group having from 5 to 12 carbon atoms (e.g., n-hexyl, 2-ethylhexyl, n-octyl, n-decyl, n-dodecyl, benzyl), yet still more preferably a substituted or unsubstituted alkyl group having from 6 to 12 carbon atoms (e.g., 2-ethylhexyl, n-octyl, n-decyl, n-dodecyl, benzyl).

The compound represented by formula (102) can be synthesized by the method described in JP-A-11-12219. Specific examples of the compound represented by formula (102) are set forth below, but the present invention is not limited to these specific examples.

UV-101

The cyano group-containing compound used as the wavelength dispersion adjusting agent is preferably a compound represented by the following formula (103): < Formula (103):

(wherein Q¹ and Q² each independently represents an aromatic ring, X¹ and X² each represents a hydrogen atom or a substituent, and at least either one of X¹ and X² is a cyano group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring). The aromatic ring represented by Q¹ and Q² may be either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. Also, the aromatic ring may be a monocyclic ring or may form a condensed ring with another ring.

The aromatic hydrocarbon ring is preferably a monocyclic or bicyclic aromatic

53

SI IRSTITI ITF SHFFT /RI II F 9fi^ hydrocarbon ring (preferably having from 6 to 30 carbon atoms) (e.g., benzene rig, naphthalene ring), more preferably an aromatic hydrocarbon ring having from 6 to 20 carbon atoms, still more preferably an aromatic hydrocarbon ring having from 6 to 12 carbon atoms, yet still more preferably a benzene ring. The aromatic heterocyclic ring is preferably an aromatic heterocyclic ring containing a nitrogen atom or a sulfur atom. Specific examples of the heterocyclic ring include thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiazole, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline, phthalazine, naphthylidine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzothiazole, benzotriazole and tetrazaindene. The aromatic heterocyclic ring is preferably pyridine, triazine or quinoline.

The aromatic ring represented by Q¹ and Q² is preferably an aromatic hydrocarbon ring, more preferably a benzene ring. Q¹ and Q² each may further have a substituent and the substituent is preferably the substituent T.

X¹ and X² each represents a hydrogen atom or a substituent, and at least either one of X¹ and X² is a cyano group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring. As for the substituent represented by X¹ and X², the substituent T can be applied. Also, the substituent represented by X¹ and X² may be further substituted by another substituent, and X¹ and X² may be annelated to form a cyclic structure.

X¹ and X² each is preferably a hydrogen atom, an alkyl group, an aryl group, a cyano group, a nitro group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring, more preferably a cyano group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring, still more preferably a cyano group or a carbonyl group, yet still more preferably a cyano group or an alkoxycarbonyl group (-C(=O)OR (R: an alkyl group having from 1 to 20 carbon atoms, an aryl group having from 6 to 12 carbon atoms or a combination thereof)). The compound of formula (103) is preferably a compound represented by the following formula (103 -A): Formula (103-A):

(wherein R , R , R , R , R , R , R , R , R and R each independently represents a hydrogen atom or a substituent; and Xl and X2 have the same meanings as in formula (103) and preferred ranges are also the same).

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ each independently represents a hydrogen atom or a substituent and as for the substituent, the substituent T can be applied. The substituent may be further substituted by another substituent, and the substituents may be annelated with each other to form a cyclic structure.

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom or an alkyl group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

R³ and R⁸ each is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group or a halogen atom, more preferably a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an amino group having from 0 to 20 carbon atoms, an alkoxy group having from 1 to 12 carbon atoms or an aryloxy group having from 6 to 12 carbon atoms, still more preferably a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms or an alkoxy group having from 1 to 12 carbon atoms, yet still more preferably a hydrogen atom.

The compound of formula (103) is more preferably a compound represented by the following formula (103-B): Formula (103-B):

(wherein R³ and R⁸ have the same meaning as in formula (103 -A) and preferred ranges are also the same; and X³ represents a hydrogen atom or a substituent).

X³ represents a hydrogen atom or a substituent and as for the substituent, the substituent T can be applied. Also, if possible, the substituent may be substituted by another substituent. X³ is preferably a hydrogen atom, an alkyl group, an aryl group, a cyano group, a nitro group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring, more preferably a cyano group, a carbonyl group, a sulfonyl group or an aromatic heterocyclic ring, still more preferably a cyano group or a carbonyl group, yet still more preferably a cyano group or an alkoxycarbonyl group (-C(^O)OR (R: an alkyl group having from 1 to 20 carbon atoms, an aryl group having from 6 to 12 carbon atoms or a combination thereof)).

The compound of formula (103) is still more preferably a compound represented by formula (103 -C): Formula (103-C):

(wherein R³ and R⁸ have the same meanings as in formula (103-A) and preferred ranges are also the same; and R²¹ represents an alkyl group having from 1 to 20 carbon atoms). When R³ and R⁸ both are a hydrogen atom, R²¹ is preferably an alkyl group having from 2 to 12 carbon atoms, more preferably an alkyl group having from 4 to 12 carbon atoms, still more preferably an alkyl group having from 6 to 12 carbon atoms, yet still more preferably an n-octyl group, a tert-octyl group, a 2-ethylhexyl group, an n- decyl group or an n-dodecyl group, and most preferably a 2-ethylhexyl group.

When R³ and R⁸ are not hydrogen, R²¹ is preferably an alkyl group having 20 or less carbon atoms and causing the compound represented by formula (103-C) to have a molecular weight of 300 or more.

The compound represented by formula (103) can be synthesized by the method described in Journal of American Chemical Society. Vol. 63, page 3452 (1941).

Specific examples of the compound represented by formula (103) are set forth below, but the present invention is not limited to these specific examples.

UV-201 -

UV-202

UV-203

UV-205 - 0

UV-213 UV-218

UV-225

(Release Agent)

In a transparent film of the present invention, a release agent is preferably added to decrease the load at the separation.

A known surfactant is effective as the release agent. The surfactant is not particularly limited and, for example, a phosphonic acid-based surfactant, a sulfonic acid-based surfactant, a carboxylic acid-based surfactant, a nonionic surfactant and a cationic surfactant can be used. Examples of the surfactant which can be used here include those described in JP-A-61-243837. As for the release agent, JP-A-2003-055501 describes a cellulose acylate solution dissolved in a non-chlorine-type solvent, in which an additiye selected from a polybasic acid partial ester form having an acid dissociation exponent pKA of 1.93 to 4.5, an alkali metal salt and an alkaline earth metal salt is added so as to prevent the cellulose acylate solution from becoming white turbid and improve the releasability at the production of film as well as the film surface state.

As for the additive, JP-A-2003-128838 describes a cellulose acylate dope solution in which at least one crosslinking agent having two or more groups reacting with active hydrogen is added in an amount of 0.1 to 10 mass% based on the cellulose acylate so as to improve the strippability, surface state and film strength. Also, JP-A-2003-165868 proposes a film in which good moisture permeability and excellent dimensional stability are attained by adding an additive.

In the present invention, the release agents described in these patent publications can be used. (Usage) A transparent film of the present invention is applied to optical usage, photographic light-sensitive material and the like. The optical usage is preferably a liquid crystal display, and a transparent film of the present invention can be used as a transparent protective film of a polarizing element. The liquid crystal display is preferably fabricated such that two polarizing elements are disposed on both sides of a liquid crystal cell comprising two electrode substrates having held therebetween a liquid crystal, and at least one optical compensatory sheet is disposed between the liquid crystal cell and the polarizing element. This liquid crystal display is preferably TN, IPS, FLC, AFLC, OCB, STN, ECB, VA or HAN. (Functional Layer) In the case of using a transparent film of the present invention for optical usage as above, various functional layers can be provided on the transparent film. Examples of the functional layer include an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easily adhesive layer, an antiglare layer, an optical compensatory layer, an orientation layer and a liquid crystal layer. In such a functional layer, a surfactant, a slipping agent, a matting agent and the like can be added. The functional group applicable to the transparent film of the present invention includes those described in JIII Journal of Technical Disclosure. No. 2001-1745, pp. 32-45, Japan Institute of Invention and Innovation (March 15, 2001). In the case of using a transparent film of the present invention for other usage, functional layers such as undercoat layer and back layer may also be provided on the transparent film. (Hard Coat Film, Antiglare Film, Antireflection Film)

A transparent film of the present invention is preferably used as a hard coat film, an antiglare film or an antireflection film by forming any one or all of a hard coat layer, an antiglare layer and an antireflection layer on one surface or both surfaces of the transparent film of the present invention so as to enhance the visibility of a flat panel display of LCD, PDP, CRT, EL and the like. Preferred embodiments of these antiglare film and antireflection film are described in detail in JIII Journal of Technical Disclosure. No. 2001-1745, pp. 54-57, Japan Institute of Invention and Innovation (March 15, 2001), and the contents therein can be applied to the transparent film of the present invention. (Surface Treatment)

A transparent film of the present invention may be surface-treated, if desired. By performing the surface treatment, the adhesion of the transparent film to respective functional layers (for example, undercoat layer and back layer) can be enhanced.

Examples of the surface treatment which can be used include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment and acid or alkali treatment. The glow discharge treatment as used herein may be a low- temperature plasma occurring in a low-pressure gas of 10^"3 to 20 Torr. A plasma treatment in an atmospheric pressure is also preferred. The plasma-exciting gas means a gas which is plasma-excited under such a condition, and examples thereof include argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, fluorocarbons such as tetrafluoromethane, and a mixture thereof. These are described in detail in HTI Journal of Technical Disclosure. No. 2001-1745, pp. 30-32, Japan Institute, of Invention and Innovation (March 15, 2001). The compounds described in this publication can be preferably used in the present invention. (Contact Angle of Film Surface after Alkali Saponification) In the case of using a transparent film of the present invention as a transparent protective film for a polarizing plate, a surface treatment by alkali saponification treatment is effective. In this case, the contact angle of the film surface after the alkali saponification is preferably 55° or less, more preferably 50° or less, still more preferably 45° or less. The contact angle is used as one index for evaluating the hydrophilicity/hydrophobicity. The contact angle may be measured by an ordinary method. More specifically, a method of dropping a 3 mm-diameter water droplet on the alkali-saponified film surface and determining the angle made by the film surface and the water droplet can be used. (Usage (Polarizing Plate))

A transparent film of the present invention is particularly useful as a polarizing plate protective film. In the case of using a transparent film of the present invention as a polarizing plate protective film, the polarizing plate is not particularly limited in its production method and can be produced by a general method. More specifically, a method where a transparent film of the present invention is saponified by an alkali treatment and on both surfaces of a polarizer produced by dipping and stretching a polyvinyl alcohol film in an iodine solution, the saponified transparent film is stacked by using an aqueous solution of completely saponified polyvinyl alcohol, may be used. In place of the alkali treatment, an adhesion facilitating process described in JP-A-6- 94915 and JP-A-6-118232 may be applied.

Examples of the adhesive used for stacking the treated surface of the transparent film to the polarizer include a polyvinyl alcohol-based adhesive such as polyvinyl alcohol and polyvinyl butyral, and a vinyl-based latex such as butyl acrylate. A polarizing plate includes a polarizer and protective films protecting both surfaces of the polarizer. Furthermore, a protect film may be stacked on one surface of the polarizing plate and a separate film may be stacked on the opposite surface. The protect film and separate film are used for protecting the polarizing plate, for example, at the shipment of polarizing plate or at the inspection of product. In this case, the protect film is stacked for protecting the surface of the polarizing plate and used on the side opposite the surface through which the polarizing plate is stacked to the liquid crystal plate. The separate film is used for covering the adhesive layer which is stacked to the liquid crystal plate, and used on the side of the surface through which the polarizing plate is stacked to the liquid crystal plate. In a liquid crystal display, a substrate including a liquid crystal is disposed between two polarizing plates and on whichever site the polarizing plate protective film utilizing a transparent film of the present invention is disposed, excellent display property can be obtained. In particular, a transparent hard coat layer, an antiglare layer, an antireflection layer and the like are provided on the polarizing plate protective film as the outermost surface on the display side of a liquid crystal display and therefore, the polarizing plate protective film using a transparent film of the present invention is preferably disposed in this portion. (Usage (Optical compensation film))

A transparent film of the present invention may be used for various uses but is particularly effective when an optically anisotropic layer is provided on the transparent film and the resulting film is used as an optical compensation film of a liquid crystal display. Incidentally, the optical compensation film is used in a liquid crystal display and indicates an optical material of compensating the phase difference, and this film has the same meaning as the retardation plate, optical compensatory sheet or the like. The optical compensation film has birefringence and is used for the purpose of eliminating the coloration on the display screen of a liquid crystal display or improving the viewing angle property.

In the case of using a transparent film of the present invention for an optical compensation film of a liquid crystal display, the liquid crystal display in which the optical compensation film is used is not limited in the optical performance of the liquid crystal cell or in the driving system, but any optically anisotropic layer required as the optical compensation film can be provided.

The optically anisotropic layer for an optical compensation film of the present invention is preferably an optically anisotropic layer satisfying the following formula

(ϋi):

(iii) Re-O to 200 (nm) and |Rth'|=0 to 300 (urn).

The optically anisotropic layer may be formed from a composition containing a liquid crystalline compound or may be formed from a polymer film having birefringence. The liquid crystalline compound is preferably a discotic liquid crystalline compound or a rod-like liquid crystalline compound. (Discotic Liquid Crystalline Compound)

Examples of the discotic liquid crystalline compound usable in the present invention include the compounds described in various publications (e.g., C. Destrade et a!.. MoI. Crysr. Liq. Cryst. Vol. 71. page 111 (1981): Kikan Kagaku Sosetsu (Quarterly Chemistry Survey), No. 22, "Ekisho no Kagaku (The Chemistry of Liquid Crystal)", Chapter 5 and Chapter 10, Section 2, Nippon Kagaku Kai (compiler) (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm.. page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc. Vol. 116, page 2,655 (1994)). The discotic liquid crystalline compound preferably has a polymerizable group so that the compound can be fixed by polymerization. As for the discotic compound having a polymerizable group, for example, a structure where a polymerizable group is bonded as a substituent to the discotic core of the discotic liquid crystalline compound may be considered. However, when the polymerizable group is directly bonded to the discotic core, it is difficult to keep the aligned state during the polymerization reaction. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferred. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula:

D(-L-P)n wherein D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12. Specific preferred examples of the discotic core (D), divalent linking group (L) and polymerizable group (P) in the formula above include (Dl) to (DlS), (Ll) to (L25), and (Pl) to (P 18), respectively, described in JP-A-2001- 4837. (Rod-Like Liquid Crystalline Compound)

Examples of the rod-like liquid crystalline compound include compounds of azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles. Other than these low-molecular liquid crystalline compounds, a polymer liquid crystalline compound may also be used as the rod-like liquid crystalline compound. In the optically anisotropic layer, the rod-like liquid crystalline molecules are preferably fixed in the aligned state and most preferably fixed by a polymerization reaction. Examples of the polymerizable rod-like liquid crystalline compound usable in the present invention include the compounds described in Makromol. Chem.. Vol. 190, page 2255 (1989), Advanced Materials. Vol. 5, page 107 (1993), U.S. Patents 4,683,327, 5,622,648 and 5,770,107, International Publication Nos. (WO)95/22586, 95/24455, 9700600, 98/23580 and 98/5205, JP-A-1-272551, JP-A-6-16616, JP-A-7- 110469, JP-A-11-80081 and JP-A-2001-328973. (Optically Anisotropic Layer Comprising Polymer Film)

The optically anisotropic layer may also be formed from a polymer film. The polymer film is formed of a polymer capable of expressing optical anisotropy. Examples of such a polymer include polyolefin (e.g., polyethylene, polypropylene, norboraene-based polymer), polycarbonate, polyarylate, polysulfone, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester and cellulose ester (e.g., cellulose triacetate, cellulose diacetate). Also, a copolymer of such a polymer or a mixture of these polymers may be used.

The optical anisotropy of the polymer film is preferably obtained by stretching. The stretching is preferably uniaxial stretching or biaxial stretching. More specifically, longitudinal uniaxial stretching utilizing peripheral velocity difference of two or more rolls, tenter stretching of stretching the polymer film in the width direction by nipping both sides, or biaxial stretching using these in combination is preferred. It is also possible that two or more polymer films are used and the optical property of two or more films as the whole satisfies the above-described conditions. The polymer film is preferably produced by a solvent casting method so as to lessen unevenness of birefringence. The thickness of the polymer film is preferably from 20 to 500 μm, and most preferably from 40 to 100 μm.

The polymer film constituting the optically anisotropic layer may also be preferably produced by a method using at least one polymer material selected from the group consisting of polyamide, polyimide, polyester, polyether ketone, polyamideimide polyesterimide and polyarylether ketone, in which a solution obtained by dissolving the polymer material in a solvent is coated on a substrate, and the solvent is dried to form a film. At this time, a method of stretching the polymer film with the substrate to express optical anisotropy and using the film as the optically anisotropic layer is also preferably used. The transparent film of the present invention can be preferably used as the substrate. It is also preferred that the polymer film is produced on a separate substrate and after separating the polymer film from the substrate, laminated with the transparent film of the present invention and the resulting laminate is used as the optically anisotropic layer. According to this method, the thickness of the polymer film can be decreased and is preferably 50 μm or less, more preferably from 1 to 20 μm. (Usage (Liquid Crystal Display))

In a liquid crystal display of the present invention, a liquid crystal cell including two electrode substrates having held therebetween a liquid crystal, and two polarizers disposed on both sides of the liquid crystal cell are provided. At least one optical compensatory sheet is preferably disposed between the liquid crystal cell and the polarizer.

A transparent film of the present invention can be used as a protective film of the polarizer in the liquid crystal display. Also, a transparent film of the present invention can be used in the liquid crystal display by providing an optically anisotropic layer on the transparent film to produce an optical compensation film as above, and disposing the optical compensation film between the liquid crystal cell and the polarizer. In the case of using a transparent film of the present invention as the optical compensation film, the transmission axis of the polarizer and the slow axis of the optical compensation film equipped with the transparent film may be arranged at any angle. Incidentally, the liquid crystal layer of the liquid crystal cell for use in a liquid crystal display of the present invention is usually formed by enclosing a liquid crystal in a space formed by interposing a spacer between two substrates. The transparent electrode layer is formed as a transparent film containing an electrically conducting substance, on the substrate. In the liquid crystal cell, a gas barrier layer, a hard coat layer and an undercoat layer (used for adhesion of the transparent electrode layer) may be further provided. These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm. (Kind of Liquid Crystal Display)

^•A transparent film of the present invention can be used for liquid crystal cells in various display modes. Various display modes such as TN (twisted nematic), IPS (in-plane switching), FLC (ferroelectric liquid crystal), AFLC (anti-ferroelectric liquid crystal), OCB (optically compensatory bend), STN (super twisted nematic), VA (vertically aligned), ECB (electrically controlled birefringence) and HAN (hybrid aligned nematic) are proposed. A display mode resulting from orientation-dividing the display mode above is also proposed. A transparent film of the present invention is effective for a liquid crystal display in any display mode and also effective for any of transmission, reflection and transflection type liquid crystal displays. (TN-Type Liquid Crystal Display) A transparent film of the present invention may also be used as the support for an optical compensation film of a TN-type liquid crystal display having a TN-mode liquid crystal cell. The TN-mode liquid crystal cell and the TN-type liquid crystal display are conventionally known. The optical compensatory sheet for use in the TN- type liquid crystal display is described in JP-A-3-9325, JP-A-6- 148429, JP-A-8-50206, JP-A-9-26572, and papers by Mori et al. (that is, Jpn. J. Appl. Phvs.. Vol. 36, page 143 (1997), and Jpn. J. Appl. Phys.. Vol. 36, page 1068 (1997)). (STN-Type Liquid Crystal Display)

A transparent film of the present invention may also be used as the support for an optical compensation film of an STN-type liquid crystal display having an STN- mode liquid crystal cell. In the STN-type liquid crystal display, the rod-like liquid crystalline molecules in the liquid crystal cell are generally twisted in the range from 90 to 360°, and the product (Δnd) of the refractive index anisotropy (Δn) and the cell gap (d) of the rod-like liquid crystalline molecule is from 300 to 1,500 nm. The optical compensatory sheet for use in the STN-type liquid crystal display is described in JP-A- 2000-105316.

(VA-Type Liquid Crystal Display)

A transparent film of the present invention is advantageously used particularly as the support for an optical compensation film of a VA-type liquid crystal display having a VA-mode liquid crystal cell. The optical compensation film for use in the VA-type liquid crystal display is preferably adjusted to have an Re retardation value of 0 to 150 nm and an Rth retardation value of 70 to 400 nm. The Re retardation value is more preferably from 20 to 70 nm. In the case of using two sheets of optical compensation film for the VA-type liquid crystal display, the Rth retardation value of the film is preferably from 70 to 250 nm. In the case of using one sheet of optical compensation film for the VA-type liquid crystal display, the Rth retardation value of the film is preferably from 150 to 400 nm. The VA-type liquid crystal display may employ an orientation-divided system as described, for example, in JP-A- 10- 123576. (IPS-Type Liquid Crystal Display and ECB-Type Liquid Crystal Display) A transparent film of the present invention is advantageously used particularly as the support for an optical compensation film or as the protective film for a polarizing plate of an IPS-type liquid crystal display or ECB-type liquid crystal display having an IPS-mode or ECB-mode liquid crystal cell. These are a mode of causing the liquid crystal material to be aligned nearly in parallel at the black display, where the liquid crystal molecules are aligned in parallel to the substrate plane in the voltage-unapplied state to provide black display. In these modes, the polarizing plate using a transparent film of the present invention contributes to the enlargement of viewing angle and elevation of contrast. In these modes, the retardation value of the protective film for the polarizing plate and the optically anisotropic layer disposed between the protective layer and the liquid crystal cell is preferably set to 2 times or less the Δn-d value of the liquid crystal layer, and the absolute value |Rth| of the Rth value is preferably set to 25 nm or less, more preferably 20 nm or less, still more preferably 15 nm or less. Therefore, a transparent film of the present invention is advantageously used. (OCB-Type Liquid Crystal Display and HAN-type Liquid Crystal Display) A transparent film of the present invention is also advantageously used as the support for an optical compensation film of an OCB-type liquid crystal display having an OCB-mode liquid crystal cell or an HAN-type liquid crystal display having an HAN- mode liquid crystal cell. In the optical compensation film used for the OCB-type liquid crystal display or HAN-type liquid crystal display, the direction having a minimum absolute value of retardation is preferably present neither in the plane nor in the normal direction of the optical compensation film. The optical property of the optical compensation film used for the OCB-type liquid crystal display or HAN-type liquid crystal display is also determined by the optical property of the optically anisotropic layer, the optical property of the support, and the configuration of the optically anisotropic layer and the support. The optical compensation film for use in the OCB-type liquid crystal display or HAN-type liquid crystal display is described in JP-A-9-197397 and paper by Mori et al. (Tpn. J. Appl. Phvs.. Vol. 38, page 2837 (1999)). (Reflective Liquid Crystal Display)

A transparent film of the present invention is also advantageously used as the optical compensation film of a TN-type, STN-type, HAN-type or GH (guest-host)-type reflective liquid crystal display. These display modes have long been well known. The TN-type reflective liquid crystal display is described in JP-A-10-123478, WO9848320 and Japanese Patent No. 3022477, and the optical compensation film used for the reflective liquid crystal display is described in WOOO-65384. (Other Liquid Crystal Displays)

A transparent film of the present invention is also advantageously used as the optical compensation film of an ASM-type liquid crystal display having an ASM (axially symmetric aligned microcell)-mode liquid crystal cell. The ASM-mode liquid crystal cell is characterized in that the thickness of the sell is maintained by a position- adjustable resin spacer. Other properties are the same as those of the TN-mode liquid crystal cell. The ASM-mode liquid crystal cell and the ASM-type liquid crystal display are described in paper by Kume et al. (Kume et al., SID 98 Digest. 1089 (1998)).

Examples

The present invention is described in greater detail below by referring to Examples. The materials, reagents, ratios, operations and the like used in the following Examples can be appropriately changed or modified without departing from the technical idea of the present invention, and the scope of the present invention is not limited to these specific examples. (Example 1) 1. Production of Transparent Film

Using a cellulose acylate as the material for the transparent film, transparent film samples of the present invention and transparent film samples of Comparative Example were produced. Two cellulose acylates differing in the acylation degree, that is, Ce-I (Ac:OH = 2.96:0.04) and Ce-2 (Ac:Pro:OH = 1.7:1.0:0.3), were used (in the parentheses, Ac is an acetyl substituent, Pro is a propionyl substituent, OH is an unsubstituted hydroxyl group, and the ratio is an acylation degree ratio). (Production of Transparent Film Sample 101)

A cellulose acylate solution having the following composition was cast by using a band casting machine and the film having a residual solvent amount of 30% was separated from the band and dried at 140°C for 40 minutes to produce Transparent Film Sample 101. The residual solvent amount of Transparent Film Sample 101 was 0.1% and the film thickness was 80 μm. Composition of Cellulose Acylate Solution:

Cellulose acylate (Ce-2) 100.0 parts by mass (weight)

Methylene chloride (first solvent) 480.0 parts by mass

Methanol (second solvent) 71.7 parts by mass

Liquid dispersion of silica particles having 0.15 parts by mass an average particle diameter of 16 nm

Compound (KI) of decreasing optical 11.7 parts by mass anisotropy

Wavelength dispersion adjusting agent 1.2 parts by mass

(HB)

Ester mixture (a mixture of monoethyl 0.1 part by mass ester, diethyl ester and triethyl ester; mixing ratio: 20:80:1)

The cellulose acylate (Ce), compound (KI) of decreasing optical anisotropy and wavelength dispersion adjusting agent (HB) used are shown in Table 1. (Production of Transparent Film Samples 102 to 104 and Comparative Samples 001 to 004)

Transparent Film. Samples 102 to 104 and Comparative Samples 001 to 004 were produced in the same manner as Sample 101 except that the cellulose acylate (Ce), compound (KI) of decreasing optical anisotropy and wavelength dispersion adjusting agent (HB) used and the amounts added were changed as shown in Table 1. (Transparent Film Sample 105)

The cellulose acylate (Ce), compound (KI) of decreasing optical anisotropy, and wavelength dispersion adjusting agent (HB) used and the amounts added were changed as shown in Table 1. Furthermore, Cellulose Acetate Solution A was cast by using a drum cooled to -10⁰C, and the film having a residual solvent amount of 250% was separated from the drum and conveyed by a tenter. The film was formed at a film- forming rate of 70 m/min by setting the average temperature in the drying zone to 140°C.

(Comparative Transparent Film Sample 005)

The cellulose acylate (Ce), compound (KI) of decreasing optical anisotropy, and wavelength dispersion adjusting agent (HB) used and the amounts added were changed as shown in Table 1. Furthermore, Cellulose Acetate Solution A was cast by using a drum cooled to -10° C, and the film having a residual solvent amount of 290% was separated from the drum and conveyed by a tenter. The film was formed at a film- forming rate of 90 m/min by setting the average temperature in the drying zone to 140°C.

With respect to the produced transparent film samples of the present invention and comparative samples, the dynamic viscoelasticity in the machine direction (casting direction) (MD direction) and the dynamic viscoelasticity in the direction perpendicular to the machine direction (TD direction) were measured in the range of 0 to 200°C to determine the tan δ value, and Tl¹, T2' and T2VT1¹ were calculated. Also, tanδ(md) and tanδ(td), which are peak values of tanδ in respective directions, were measured and tanδ(md)/tanδ(td) was determined. In the measurement of dynamic viscoelasticity, a dynamic viscoelasticity meter DVA-225 (manufactured by IT Keisoku Seigyo K.K.) was used. The measuring frequency was set to 1 Hz.

Also, after humidity conditioning at 25°C-60% RH for 2 hours, transparent film samples and comparative samples were measured on the retardation Re in the film plane and the retardation Rth in the film thickness direction by using an automatic birefringence meter (K0BRA-21ADH, manufactured by Oji Test Instruments). The measuring wavelength was set to 589 nm. The measurement results are shown in Table 1.

Table 1

Table 1 (Continued)

2. Production of IPS-Mode Liquid Crystal Display

The transparent film produced in 1 above was processed to a polarizing plate, and an IPS-mode liquid crystal display 10 having a construction shown in Fig. 1 was produced. The liquid crystal display 10 shown in Fig. 1 comprises a liquid crystal cell 30 in which a liquid crystal layer 17 containing liquid crystalline molecules 17a is interposed between a pair of substrates 16 and 18.

On the lower side of the substrate 18, a lower polarizing plate 40 in which a lower polarizing film lib is sandwiched by two sheets of transparent film 19 is provided. For the transparent film 19, Transparent Film Sample 101 produced above was used.

The relationship between the transmission axis 12a or 12b of the upper polarizing film 11a or lower polarizing film l ib and the slow axis 15a of the first optical compensation film is revealed below in the description of respective members.

In Fig. 1, for the sake of convenience, each member is drawn as an independent member but in some cases, each member is integrated with other members, for example, the transparent film 19 as the protective film is integrated with the polarizing film l ib, and then incorporated into a device.

The production method of each member is described in detail below. (Production of IPS-Mode Liquid Crystal Cell 30) Two electrodes were disposed with a space to give a distance of 20 μm between electrodes. A polyimide film was provided on these two electrodes and subjected to a rubbing treatment to form an orientation film, thereby producing a substrate 18. Also, a polyimide film was provided on the surface of one separately prepared glass plate and subjected to a rubbing treatment to form an orientation film, thereby producing a substrate 16.

The orientation films were opposed to arrange the rubbing directions of two substrates 16 and 18 in parallel and the gap (d) between substrates was kept to 3.9 μm. Subsequently, a nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a positive dielectric anisotropy (Δε) of 4.5 was enclosed between the orientation films to form a liquid crystal layer 17, thereby producing a liquid crystal cell 30. The d-Δn value of the liquid crystal layer 17 was 300 nm. (Production of Lower Polarizing Plate 40)

Transparent Film Sample 101 of the present invention was dipped in an aqueous 1.5 N sodium hydroxide solution at 55°C for 2 minutes, then washed in a water washing bath at room temperature and neutralized with use of 0.1 N sulfuric acid at 3O⁰C. The film was again washed in a water washing bath at room temperature and dried with hot air at 100°C. The resulting surface-saponified Transparent Film Sample 101 was used as the transparent film 19 of Fig. 1. Separately, a 80 μm-hick rolled polyvinyl alcohol film was continuously stretched at a draw ratio of 5 times in an aqueous iodine solution and dried to produce a 20 μm-thick lower polarizing film 1 Ib.

Two sheets of transparent film 19 comprising Transparent Film Sample 101 were prepared and bonded with the intervention of the lower polarizing film l ib by using an aqueous 3% polyvinyl alcohol (PVA-117H, produced by Kuraray Co., Ltd.) solution as the adhesive to produce a lower polarizing plate 40 of with both surfaces being protected by the transparent film 101. At this time, the transparent film were bonded such that the slow axis of Transparent Film Sample 101 on both sides came to run in parallel with the transmission axis 12b of the lower polarizing film 1 Ib. Using Transparent Film Samples 102 to 105 and Comparative Samples 001 to

005, lower polarizing plates 40 were produced in the same manner. The lower polarizing plates 40 produced by using Transparent Film Samples 102 to 105 and Comparative Samples 001 to 005 all had a sufficiently high polarization degree. (Production of Second Optical compensation film 13) Fujitac TD80UF (produced by Fuji Photo Film Co., Ltd.) was longitudinally uniaxially stretched at 150°C to a stretching percentage of 15%, thereby producing an optical compensation film 13. This film had an optical property of Re=5 nm and Rth=70 nm.

(Production of First Optical compensation film 15) The surface of the second optical compensation film 13 produced above was saponified by the same method as the saponification of the transparent film above and on this film, a coating solution for orientation film having a composition shown below was coated by a wire bar coater to a coverage of 20 ml/m². This coating was dried with hot air at 60°C for 60 seconds and further with hot air at 100°C for 120 seconds. The dried coating was subjected to a rubbing treatment in the direction parallel to the slow axis direction of the film, thereby forming an orientation film. Composition of Coating Solution for Orientation Film:

Modified polyvinyl alcohol shown below 10 parts by mass

Water 371 parts by mass

Methanol 119 parts by mass

Glutaraldehyde 0.5 parts by mass

Tetramethylammonium fluoride 0.3 parts by mass

Subsequently, a solution obtained by dissolving 1.8 g of a discotic liquid crystalline compound shown below, 0.2 g of an ethylene oxide-modified trimethylolpropane triacrylate (V#360, produced by Osaka Organic Chemical Industry Ltd.), 0.06 g of a photopolymerization initiator (Irgacure 907, produced by Ciba Geigy), 0.02 g of a sensitizer (Kayacure DETX, produced by Nippon Kayaku Co., Ltd.) and 0.01 g of a fluorine-containing polymer (air interface vertically aligning agent) shown below in 3.9 g of methyl ethyl ketone was coated on the orientation film by a #5 wire bar, and the resulting film was stacked on a metal frame and heated in a constant- temperature bath at 125°C for 3 minutes to align the discotic liquid crystal compound.

Thereafter, using a high-pressure mercury lamp of 120 W/cm² at 100° C, UV was irradiated for 30 seconds to cross-link the discotic liquid crystal compound. The resulting film was allowed to cool to room temperature. In this way, a retardation film 21 including the second optical compensation film 13 having formed thereon the first optical compensation film 15 was produced. Discotic Liquid Crystalline Compound:

The light incident angle dependency of Re of the retardation film 21 produced above was measured and by subtracting therefrom the previously measured contribution of the second optical compensation film, the optical property of only the first optical compensation film 15 (discotic liquid crystal retardation layer) was calculated, as a result, Re was 110 nm, Rth was -55 nra, and the average tilt angle of liquid crystal was 89.9°. Thus, it could be confirmed that the discotic liquid crystal was aligned vertically to the film plane. Incidentally, the slow axis direction was parallel to the rubbing direction of the orientation film. (Production of Upper Polarizing Plate 20)

A polarizer was produced by adsorbing iodine to a stretched polyvinyl alcohol film, and a cellulose acetate film (Fujitac TD80UF, produced by Fuji Photo Film Co., Ltd.) was laminated to one surface of the obtained polarizer by using a polyvinyl alcohol-base adhesive, thereby producing an upper polarizing film 11a. The retardation film 21 was stacked on another surface of the upper polarizing film 11a such that the second optical compensation film 13 came to the upper polarizing film 11a side, thereby producing an upper polarizing plate 20 integrated with the second optical compensatory layer. Incidentally, the low axis 15a of the first optical compensation film 15 was arranged to run in parallel with the transmission axis 12a of the polarizing film 11a.

(Production of Liquid Crystal Display 10)

The upper polarizing plate 20 was stacked to the IPS-mode liquid crystal cell

30 such that the first optical compensation film 15 side came to the liquid crystal cell 30 side. Here, the slow axis (not shown) of the liquid crystal layer 17 of the liquid crystal cell 30 was arranged to run in parallel with the transmission axis' 12a of the upper polarizing film 11a.

Subsequently, the lower polarizing plate 40 was laminated to the lower side of the liquid crystal cell 30 such that the transmission axis 12b of the lower polarizing film 1 Ib came to be orthogonal to the transmission axis 12a of the upper polarizing film 11a, thereby producing a liquid crystal display 10 shown in Fig. 1. 3. Production of VA-Mode Liquid Crystal Display

By processing the transparent film produced in 1 above, a VA-mode liquid crystal display 50 shown in Fig. 2 was produced. The liquid crystal display 50 shown in Fig. 2 includes a liquid crystal cell 60 in which liquid crystalline molecules 57a are interposed between a pair of substrates 56 and 58.

On the upper side of the substrate 56 of the liquid crystal cell 60, an upper polarizing plate 70 in which an optical compensation film 55, a polarizer 51 and a cellulose acetate film 54 was stacked upward in this order was provided. Also, on the lower side of the substrate 58, a lower polarizing plate 80 in which a polarizer 51 was sandwiched by two sheets of cellulose acetate film 54 was provided. (Production of Optical compensation film 55)

Using the transparent film sample of the present invention, an optical compensation film sample was produced according to the method described in Example 1 of JP-A-2003-315541. A polyimide having a weight average molecular weight (Mw) of 70,000 and Δn of about 0.04, which was synthesized from 2,2'-bis(3,4- dicarboxyphenyl)hexafluoropropane dianhydride (6FD A) and 2,2'-bis(trifluoromethyl)- 4,4'-diaminobiphenyl (TFMB), was formulated into a 25 wt% solution by using cyclohexanone as the solvent, and this solution was coated on Transparent Film Samples 101 to 105 and Comparative Samples 001 to 005 produced in 1 above.

Subsequently, the film was heat-treated at 100°C for 10 minutes and then longitudinally uniaxially stretched at 160°C to a stretching percentage of 15% to obtain an optical compensation film 55 in which a 6 μm-thick polyimide film was coated on the transparent film of the present invention. As for the optical property of this optical compensation film 55, Re=72 nm, Rth=220 nm, the slippage angle • of the orientation axis was within ±3°, and a birefringent layer of nx>ny>nz was present. (Mounting on VA-Type Liquid Crystal Display)

The thus-produced optical compensation film 55 on the side not coated with the polyimide film was bonded to a polarizer 51 by using an alkali-saponified polyvinyl alcohol-based adhesive, thereby directly stacking the optical compensation film 55 and the polarizer 51, and a cellulose acetate film 54 (Fujitac TD80UF, produced by Fuji Photo Film Co., Ltd.) was stacked on the opposite side of the polarizer 51 to produce an upper polarizing plate 70 with an optical compensation film. At this time, the film was stacked such that the nx direction 55a of the optical compensation film came to be orthogonal to the absorption axis 5a of the polarizing plate. As for the polarizer 51, the same polarizer used in the polarizing plate 20 (Fig. 1) was used.

This upper polarizing plate 70 was bonded to the liquid crystal cell 60 by an adhesive such that the optical compensation film 55 came to the liquid crystal cell 60 side. Incidentally, on the opposite side of the liquid crystal cell 60, a polarizing plate 80 in which a cellulose acetate film 54 (Fujitac TD80UF, produced by Fuji Photo Film Co., Ltd.) was stacked on both surfaces of the polarizer 51 was bonded to the liquid crystal cell 60 through a pressure-sensitive adhesive such that the absorption axes 51a of the upper and lower polarizing plates came to be orthogonal to each other, thereby producing a VA-type liquid crystal display 50.

4. Evaluation of Retardation Film and Measurement of Leakage Light of Liquid Crystal Display

The viewing angle dependency of the transmittance of the liquid crystal displays produced in 2 and 3 above was measured. The elevation angle was measured from the front face to the oblique direction until 80° in steps of 10°, and the azimuth angle was measured until 360° based on the horizontal right direction (0°) in steps of 10°. As for the brightness at the black display, it was found that as the elevation angle increases from the front face direction, the leakage light transmittance increases and takes a maximum value near the elevation angle of 70° and also found that since the black display transmittance increases, the contrast changes for the worse. Therefore, the viewing angle property was evaluated by the maximum values of the black display transmittance of the front face and the leakage light transmittance at an elevation angle of 60°. Furthermore, as an endurance test, the display unevenness after standing at

60°C-90% RH for 500 hours and the display unevenness after standing at 80°C-0% RH for 500 hours were observed. The unevenness was generated mainly at four corners of the panel. The results obtained are shown in Table 2. (Evaluation of Display Property) Leakage Light at Corners:

A: Good with very slight difference in viewing angle property.

B: Small difference in viewing angle property.

C: Large difference in viewing angle property. Viewing Angle Property: A: Good with very slight unevenness.

B : Small unevenness .

C: Large unevenness.

Table 2

It will be apparent to those skilled in the art that various modifications and variations can be made to the described preferred embodiments of the invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover all modifications and variations of this invention consistent with the scope of the appended claims and their equivalents.

This application is based on Japanese Patent Application Nos. JP2004-275834 and JP2005-185271, filed on September 22 of 2004 and June 24 of 2005, respectively, the contents of which is incorporated herein by reference.

Industrial Applicability A transparent film according to the invention can be applied to a polarizing plate and a liquid crystal display (LCD), in which the in-plane retardation Re and the retardation Rth in the film thickness direction are decreased and at the same time, these

Re and Rth are less changed due to change in the environment such as temperature and humidity.

Claims

1. A transparent film, wherein an absolute value Tl' of the maximum variation of tanδ value per unit temperature in a range from 0 to 120°C is from 0 to 0.005, the tanδ value is a loss tangent obtained by measuring a dynamic viscoelasticity of the transparent film at a measuring frequency of 1 Hz, and a retardation value Re in a film plane of the transparent film and a retardation value Rth in a thickness direction of the transparent film satisfies formulae (i) and (ii):

(i) 0<Re<20 (ii) |Rth|<25.

2. The transparent film as claimed in claim I₃ wherein an absolute value T2¹ of the maximum variation of tanδ value per unit temperature in a range from 120 to 200°C is from 0.005 to 0.05, the tanδ value is a loss tangent obtained by measuring a dynamic viscoelasticity of the transparent film at a measuring frequency of 1 Hz.

3. The transparent film as claimed in claim 1 or 2, wherein a ratio of T2¹ to Tl¹ is 2 or more.

4. The transparent film as claimed in any one of claims 1 to 3, wherein the tan δ value is a value obtained by measuring a dynamic viscoelasticity in one direction of a machine direction of the transparent film and a direction perpendicular to the machine direction.

5. The transparent film as claimed in any one of claims 1 to 4, wherein a peal- value tanδ(md) of the tanδ value in a machine direction of the transparent film and a peak value tanδ(td) of the tanδ value in a direction perpendicular to the machine direction each is from 0.4 to 0.8, and the peak values tanδ(md) and tanδ(td) satisfy a relationship of 0.7<tan δ(md)/tan δ(td)<1.4.

6. The transparent film as claimed in any one of claims 1 to 5, which comprises a cellulose acylate.

7. The transparent film as claimed in any one of claims 1 to 6, which has at least one layer of a hard coat layer, an antiglare layer and an antireflection layer.

8. An optical compensation film comprising: a transparent film according to any one of claims 1 to 7; and an optically anisotropic layer, wherein a retardation value Re¹ in a plane of the optically anisotropic layer and a retardation value Rth¹ in a thickness direction of the optically anisotropic layer satisfies formula (iii): (iii) Re'=0 to 200 (ran) and |Rth'|=O to 300 (ran).

9. The optical compensation film as claimed in claim 8, wherein the optically anisotropic layer is formed by using a discotic liquid crystalline compound.

10. The optical compensation film as claimed in claim 8 or 9, wherein the optically anisotropic layer is formed by using a rod-like liquid crystalline compound.

11. The optical compensation film as claimed in any one of claims 8 to 10, wherein the optically anisotropic layer comprises a polymer film having a birefringence.

12. The optical compensation film as claimed in claim 11, wherein the polymer film comprises at least one polymer material selected from the group consisting of polyamide, polyimide, polyester, polyether ketone, polyamideimide polyesterimide and polyarylether ketone.

13. A polarizing plate comprising: a polarizer; and a protective film comprising at least one of a transparent film according to any one of claims 1 to 7 and an optical compensation film according to any one of claims 8 to 12.

14. A liquid crystal display comprising at least one of a transparent film according to any one of claims 1 to 7, an optical compensation film according to any one of claims 8 to 12 and a polarizing plate according to claim 13.

15. The liquid crystal display as claimed in claim 14, which is a display of VA or IP S mode.