JP2003075640A - Method for manufacturing optical retardation film and optical retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for manufacturing an optical retardation film by irradiation of non-polarized light or ultraviolet rays in which a completely polarized component and a non-polarized component are mixed. SOLUTION: A film is formed by application (spin coating or casting) of a mixture of a photosensitive polymer and a low molecular weight compound. Although a side chain of the photosensitive polymer and the low molecular weight compound are not oriented in the film, the optical retardation film in which three principal refractive indexes nx, ny and nz of an index ellipsoid in the film and the slope of nx axis are controlled with respect to the direction normal to the film surface is manufactured by an irradiation operation of the non-polarized light or light in which the completely polarized component and the non-polarized component are mixed. The film is useful as the optical retardation film to enlarge a viewing angle of a liquid crystal display device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a retardation film used for expanding the viewing angle of a liquid crystal display device.

[0002]

2. Description of the Related Art Retardation films are films having birefringence that allow linearly polarized light components vibrating in mutually perpendicular principal axis directions to pass therethrough and give a required retardation between the two components.
By imparting specific optical characteristics, such a retardation film serves as an optical compensation film for expanding the viewing angle of a liquid crystal display device. Several conventional techniques for producing such a retardation film have been reported. For example, in Japanese Patent No. 2640083, three main refractive indices nx, ny, and nz are nx on a rubbing alignment film and a SiO oblique vapor deposition alignment film.
There is described a phase film in which discotic liquid crystal with = ny> nz is arranged in a tilted manner. In addition, JP-A-10
In −332933, the three main refractive indices are nx> ny =
A retardation film composed of a rubbing alignment film, a film in which a liquid crystal polymer having an index ellipsoid of nz is obliquely arranged on a SiO oblique vapor deposition alignment film, and a layer of a negative index ellipsoid is described. Has been done. Furthermore, JP-A-2000-
No. 121831 discloses a retardation film in which tantalum pentoxide, which is an inorganic compound, is obliquely vapor-deposited and three biaxial index ellipsoids each having a principal refractive index of nx>ny> nz are arranged obliquely. . However, the method using the alignment film as described above has a problem that the process such as the alignment treatment of the alignment film and the alignment of the liquid crystal material is complicated, and the method of obliquely vapor-depositing the inorganic compound is used on the long sheet. In order to continuously form the vapor-deposited film, there are problems that the apparatus becomes large and the process becomes complicated.

As a method of exhibiting a phase difference by light irradiation, JP-A-7-138308 describes a method of irradiating a photosensitive polymer such as polyvinyl cinnamate with linearly polarized light, and also the present invention. The person in charge of the invention is also JP-A-10-27
Japanese Patent No. 8123 proposes a method for producing a retardation film having an inclined optical axis by irradiating a side-chain type liquid crystalline polymer having photosensitivity with a linearly polarizing ultraviolet ray. In this method, the three main refractive indices are nx> n
It is possible to manufacture a retardation film in which a refractive index ellipsoid in which y = nz is tilt-oriented. However, when the retardation film is used for the purpose of enlarging the viewing angle in a liquid crystal display device, a sufficient effect may not be obtained, and birefringence or 3 It is desirable to control the two main refractive indices nx, ny, nz and the inclination of the X axis.

[0004]

In the present invention, as shown in FIG. 1, a film 11 made of a photosensitive polymer having a positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound is used. By the operation of irradiating non-polarizing light or light (L) in which a completely polarized component composed of P component (Lp) and S component (Ls) and a non-polarized component are mixed, birefringence or a refractive index ellipsoid in the film The three main refractive indices nx (1a) of
It is possible to provide a retardation film in which the inclinations of ny (1b), nz (1c) and the nx axis with respect to the film surface normal direction are controlled. Here, controlling the birefringence means expressing the birefringence equivalent to the case where a bend- or tilt-aligned index ellipsoid or a combination of these with a non-tilted uniaxial index ellipsoid. Say.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below. In the production of the retardation film of the present invention, the present inventor
Japanese Patent Application Laid-Open No. 11-189665, Japanese Patent Application 2000-
As described in No. 400356, a material that causes birefringence upon irradiation with light and heating / cooling can be used. These materials include substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are often used as mesogenic components of liquid crystalline polymers, and cinnamoyl groups,
It has a side chain containing a structure in which a photosensitive group such as a chalcone group, a cinnamylidene group, a β- (2-furyl) acryloyl group (or a derivative thereof) is bonded, and has a hydrocarbon, acrylate, methacrylate, maleimide, N- Examples thereof include polymers having a structure such as phenylmaleimide and siloxane in the main chain. The polymer may be a homopolymer of the same repeating unit or a copolymer of units having side chains with different structures, or it is also possible to copolymerize units having side chains containing no photosensitive group. . When the low molecular weight compound is mixed, the low molecular weight compound may be a compound having a crystallinity or a liquid crystallinity, which has a substituent such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are often used as mesogenic components. The low molecular weight compound to be mixed is not limited to a single compound, and a plurality of kinds of compounds can be mixed. Furthermore, addition of an alignment aid for improving the alignment property and a cross-linking agent for improving the heat resistance to the extent that the liquid crystallinity is not impaired, and a monomer that does not exhibit the liquid crystallinity without impairing the liquid crystallinity May be copolymerized with a photosensitive polymer. However, the photosensitive polymer and the low molecular weight compound are not limited to the above. These photosensitive polymers are disclosed in JP-A-7-138.
Unlike 308, in which a photosensitive polymer such as polyvinyl cinnamate is irradiated with linearly polarized light to develop birefringence only by a photoreaction, the irradiation energy amount of light is accompanied by alignment by heating and cooling after the photoreaction. However, the principle of manifesting birefringence is completely different. In addition, although there have been some proposals to develop a phase difference by light irradiation, from the viewpoint of controlling the three main refractive indices of birefringence or refractive index ellipsoid by light irradiation, polarization of irradiation light of the present invention It was confirmed for the first time that such a retardation film is effective for widening the viewing angle of a liquid crystal display device.

Based on FIG. 2, a mixture of a photosensitive polymer and a low molecular weight compound is applied (spin coating or casting).
The film thus formed will be described. FIG. 2 schematically shows the film (film) after the film formation. The film (22) is isotropic at the time of film formation, and the side chain part of the photosensitive polymer and the low molecular weight compound are not oriented in a specific direction. That is, in the film (22), the side chains (2a, 2b) having a photosensitive group represented by a long ellipse and the low molecular weight compound (2c) represented by a cylinder are randomly present (coexisting).
When this film is irradiated with an ultraviolet pseudo-parallel light flux (L), which is a mixture of completely polarized components and non-polarized components of P component (Lp) and S component (Ls), side chains oriented in the direction perpendicular to the traveling direction of the irradiated ultraviolet rays. (2a) is a side chain (2
b) Since it is more sensitive to light, the reaction proceeds selectively. This is because the conjugated system of the photosensitive moiety containing a benzene ring etc. extends in the long axis direction of the side chain, and when such side chain is placed in a radiation field such as light, the electric field of light is changed. This is because the interaction becomes maximum when the vibration direction matches the long-axis direction of the side chain, and the interaction becomes minimum when the traveling direction of light and the long-axis direction of the side chain match. From this, the irradiation of ultraviolet rays containing a completely polarized component and a non-polarized component,
The film can be a film in which a photoreaction in a specific direction is advanced. In order to proceed with this photoreaction, it is necessary to irradiate light having a wavelength with which the photosensitive group moiety can react. This wavelength is generally 200 to 500 nm, although it depends on the type of the photosensitive group, and 250 to 400 nm is particularly effective in many cases.

FIG. 3 is a schematic view of a film (33) whose orientation is promoted after irradiation of the film of FIG. 2 with photo-ultraviolet light in which a completely polarized component composed of a P component and an S component and a non-polarized component are mixed. .
As shown in FIG. 3, the side chain (3b) or the low molecular weight compound (3c) in the film (33) that did not undergo photoreaction is the molecular motion after irradiation of ultraviolet rays in which a completely polarized component and a non-polarized component are mixed. Due to this, the film is oriented under the influence of anisotropy developed in the film in which the photoreaction in a specific direction has progressed (the side chain (3a) is exposed to light containing a mixture of a completely polarized component and a non-polarized component and reacted with it). The chain and the side chain (3b) represent the side chains that did not react because they were oriented in the direction parallel to the traveling direction of the irradiation ultraviolet light.). As a result, birefringence is induced in the entire film,
Its birefringence or the three principal indices of refraction of the film nx, ny,
The ratio of nz and the inclination of the nx axis with respect to the normal to the film surface can be controlled by the ratio of the P component and S component of the light in which the completely polarized component and the non-polarized component are mixed, the irradiation angle thereof, and the characteristics of the photosensitive material. . Furthermore, by irradiating a light-sensitive material such as an example described later with non-polarizing light or light in which a completely polarized component and a non-polarized component are mixed, a bend- or tilt-aligned refractive index ellipsoid or these It is also possible to exhibit the same birefringence as in the case of combining with a non-tilted uniaxial index ellipsoid.

Alignment due to molecular motion after irradiation of non-polarizing light or ultraviolet rays in which a completely polarized component and a non-polarized component are mixed is promoted by heating the film. It is desirable that the heating temperature of the film is lower than the softening point of the photoreacted portion and higher than the softening points of the side chains and the low molecular weight which are not photoreacted. Further, in order to promote the orientation of the film, it is also effective to irradiate ultraviolet rays containing a completely polarized component and a non-polarized component under heating (from room temperature to Ti + 5 ° C.). Here, Ti indicates a phase transition temperature when the liquid crystal phase changes to an isotropic phase. Preferably, it is effective to irradiate with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed before and after Ti. In this way, after irradiating ultraviolet rays containing a completely polarized component and a non-polarized component, heating, or by irradiating the film irradiated with ultraviolet rays having a completely polarized component and non-polarized component mixed under heating to a temperature below the softening point of the polymer. The molecules are frozen, and the retardation film of the present invention is obtained.

In the present invention, when the low molecular weight compounds mixed with the photosensitive polymer have heat or photoreactivity with each other or with respect to the polymer, the orientation is firmly fixed. Therefore, improvement in heat resistance is expected. In such a case, it is necessary to control the density of photoreactive points by suppressing the exposure dose or adjusting the reactivity so as not to hinder the molecular movement during reorientation. The low molecular weight compound has an effect of suppressing the haze when it is added in an appropriate amount, but when added in an excessive amount, it causes an increase in the haze and a decrease in orientation. From such a viewpoint, although depending on the type of the photosensitive polymer or the low molecular weight compound, the retardation film can be produced by adding the low molecular weight compound in an amount of 0.1 wt% to 80 wt%, but preferably 5 wt%. % To 50 wt% is desirable. here,
If the photopolymer and the low-molecular compound are not sufficiently compatible, heating of the substrate during film formation or after exposure will produce crystals of a size that can induce phase separation or visible light scattering, resulting in haze. Cause the increase of.

As a method of increasing the film thickness to obtain a film having a larger retardation, there is a method of laminating films. In this case, in order to prevent the destruction of the film formed earlier in the step of coating and laminating the material solution on the film irradiated with ultraviolet rays in which the completely polarized component and the non-polarized component are mixed, the film is first formed. It is effective to dissolve and use the polymer and the low molecular weight compound in a solvent having reduced solubility. Further, when the film of the photosensitive compound is irradiated from the front and back surfaces with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed, birefringence is more efficiently developed. The photosensitive compound may be formed into a film by coating it on a support, and the compound may be directly or through the support irradiated with ultraviolet rays containing a completely polarized component and a non-polarized component. In the case of interposing a support, any material may be used as long as the support has a property of transmitting light having a wavelength at which a photosensitive compound can react, but the higher the light transmittance, the smaller the irradiation dose. The manufacturing process is advantageous. It is also possible to form a film of a photosensitive compound on a releasable support and, after peeling, irradiate the front and back surfaces of the film with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed.

FIG. 4 shows an example of the method (apparatus) for producing the retardation film of the present invention. The non-polarizing ultraviolet ray (46) generated by the ultraviolet lamp (41) excited by the power source (42) is applied (coated) on the support (45) through a polarizer capable of obtaining a desired degree of polarization. The film (44) of the mixture of the photosensitive polymer and the low molecular weight compound is irradiated. Examples 1 to 10 are birefringent or have three main refractive indices nx, ny and nz in the film according to the production method of the present invention.
3A and 3B are each an example in which a retardation film in which the inclination of the nx axis with respect to the film surface normal direction is controlled is produced. Example 1 3.75% by weight of poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,
Dissolve 4′-bis (isobutyloxyhexyloxy) biphenyl in dichloroethane and deposit about 1.
It was applied in a thickness of 5 μm. Place the substrate on the horizontal plane 45
Arranged so as to incline, and the degree of polarization: P-S / P + S (P and S
Are the transmitted light intensities of the P component and the S component, respectively, and the intensity of the completely polarized component is indicated by P−S, and P + S is the total transmitted light intensity of the completely polarized component and the unpolarized component. ) Is 1
5.6 (%) of ultraviolet rays is applied from the direction perpendicular to the horizontal plane at room temperature to 500 mJ / c from both the front and back surfaces of the substrate.
After irradiating m ² each, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The refractive index ellipsoid of the substrate thus obtained is 3
The ratio of the two main refractive indices is nx = 1.6, ny = 1.5, nz
= 1.5, and the nx axis is 0 to 9 with respect to the substrate surface normal direction.
0 °, the ratio of the bend-oriented refractive index ellipsoid and the three main refractive indices is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is 0 with respect to the normal direction to the substrate surface. It was equivalent to a combination of uniaxially oriented films having a temperature of °.

Example 2 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,4'-bis (isobutyryloxyhexyloxy) biphenyl are dissolved in dichloroethane and about 1. It was applied in a thickness of 5 μm. The substrate is arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and the polarization degree is -15.6.
UV light (%) was irradiated at a room temperature in the direction perpendicular to the horizontal plane at room temperature from both front and back surfaces of the substrate at 500 mJ / cm ^2, respectively, and then heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The refractive index ellipsoid of the substrate thus obtained has a ratio of three main refractive indices of nx = 1.55, ny = 1.6, nz =
It was 1.5, and the nx axis was inclined by 45 ° with respect to the direction normal to the substrate surface.

Example 3 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,4'-bis (isobutyryloxyhexyloxy) biphenyl are dissolved in dichloroethane and about 1. It was applied in a thickness of 5 μm. The substrate is arranged so as to be inclined at 45 degrees with respect to the horizontal plane, and the polarization degree: PS / P
+ S (P and S are the transmitted light intensities of the P component and the S component, respectively, and the intensity of the completely polarized component is represented by P−S, P + S
Is the total transmitted light intensity including the completely polarized component and the non-polarized component. ) Is 7.9 (%), and ultraviolet rays are applied from the direction perpendicular to the horizontal plane at room temperature to 50
After irradiation with 0 mJ / cm ² each, the mixture was heated to 100 ° C. and cooled to room temperature. Then, in order to promote the reaction of the unreacted photosensitive group and strengthen the alignment, 1 J / c of non-polarizing ultraviolet light is applied.
m ² irradiation. The refractive index ellipsoid of the substrate thus obtained has a ratio of three main refractive indices of nx = 1.65 and ny =
It was 1.51 and nz = 1.5, which was the same as in the case of the refractive index ellipse in which the nx axis was bend-aligned with 10 to 40 ° with respect to the substrate surface normal direction. .

Example 4 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,4'-bis (isobutyryloxyhexyloxy) biphenyl are dissolved in dichloroethane and about 1. It was applied in a thickness of 5 μm. The substrate is arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and the polarization degree is -7.9.
UV light (%) was irradiated at a room temperature in the direction perpendicular to the horizontal plane at room temperature from both front and back surfaces of the substrate at 500 mJ / cm ^2, respectively, and then heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The refractive index ellipsoid of the substrate thus obtained has a ratio of three main refractive indices of nx = 1.6, ny = 1.54, nz =
It was 1.5, and the nx axis was inclined by 25 ° with respect to the normal direction to the substrate surface.

Example 5 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,4'-bis (isobutyryloxyhexyloxy) biphenyl are dissolved in dichloroethane and about 1. It was applied in a thickness of 5 μm. The substrate was placed so as to be inclined at 45 degrees with respect to the horizontal plane, and non-polarizing ultraviolet light [polarization degree = 0 (%)] was applied to each of the front and back surfaces of the substrate at 500 mJ / cm ² at room temperature from the direction perpendicular to the horizontal plane. After irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . In the index ellipsoid of the substrate thus obtained, the ratios of the three main refractive indices are nx = 1.6, ny = 1.53, and nz =
It was 1.5, and the nx axis was inclined by 32 ° with respect to the normal direction to the substrate surface.

(Example 6) 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4'-cyanobiphenyl are dissolved in dichloroethane and coated on a glass substrate to a thickness of about 1.5 μm. did. The substrate is arranged so as to be inclined at 45 degrees with respect to the horizontal plane, and the polarization degree: P−S / P + S (P and S are the transmitted light intensities of the P component and the S component, respectively, and the intensity of the completely polarized component is P−. It is represented by S, and P + S is the total transmitted light intensity obtained by combining the completely polarized component and the non-polarized component.) Is 15.6 (%).
After irradiating the front and back surfaces of the substrate with 500 mJ / cm ² each at room temperature from the direction perpendicular to the horizontal plane at room temperature, it was heated to 100 ° C. and cooled to room temperature. continue,
Irradiation with 1 J / cm ² of non-polarizing ultraviolet rays was carried out in order to accelerate the reaction of unreacted photosensitive groups and strengthen the orientation. The birefringence of the substrate thus obtained is such that the ratios of the three main refractive indices are nx = 1.6, ny = 1.5 and nz = 1.5,
The ratio of the refractive index ellipse in which the nx axis is bend-aligned by 50 to 90 ° with respect to the substrate surface normal direction and the three main refractive indices is nx = 1.6,
It was ny = 1.5 and nz = 1.5, and was equivalent to a combination of uniaxially oriented films in which the nx axis was 0 ° with respect to the normal direction to the substrate surface.

Example 7 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4'-cyanobiphenyl are dissolved in dichloroethane and coated on a glass substrate to a thickness of about 1.5 μm. did. The substrate is arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and the ultraviolet ray having a polarization degree of -15.6 (%) is
After irradiating 500 mJ / cm ² each from the front and back surfaces of the substrate at room temperature in the direction perpendicular to the horizontal plane, the substrate was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The refractive index ellipsoid of the substrate thus obtained has a ratio of three main refractive indices of nx = 1.
6, ny = 1.59, nz = 1.5, and the nx axis was tilted by 37 ° with respect to the substrate surface normal direction.

Example 8 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4'-cyanobiphenyl are dissolved in dichloroethane and coated on a glass substrate to a thickness of about 1.5 μm. did. The substrate is arranged so as to be inclined at 45 degrees with respect to the horizontal plane, and the polarization degree: P−S / P + S (P and S are the transmitted light intensities of the P component and the S component, respectively, and the intensity of the completely polarized component is P−. It is indicated by S, and P + S is the total transmitted light intensity that combines the completely polarized component and the non-polarized component.) Is 7.9 (%). Each of the above was irradiated with 500 mJ / cm ² and heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The birefringence of the substrate thus obtained is such that the ratios of the three main refractive indices are nx = 1.58, ny = 1.5 and nz = 1.5,
It was the same as in the case of a refractive index ellipse in which the nx axis was bend-aligned with 0 to 30 ° with respect to the substrate surface normal direction.

Example 9 3.75% by weight of poly (4-
Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4'-cyanobiphenyl are dissolved in dichloroethane and coated on a glass substrate to a thickness of about 1.5 μm. did. The substrate is arranged so as to be inclined at 45 degrees with respect to the horizontal plane, and the polarization degree: P−S / P + S (P and S are the transmitted light intensities of the P component and the S component, respectively, and the intensity of the completely polarized component is P−. It is represented by S, and P + S is the total transmitted light intensity obtained by combining the completely polarized component and the non-polarized component.) Is -7.9 (%).
After irradiating the front and back surfaces of the substrate with 500 mJ / cm ² each at room temperature from the direction perpendicular to the horizontal plane at room temperature, it was heated to 100 ° C. and cooled to room temperature. continue,
Irradiation with 1 J / cm ² of non-polarizing ultraviolet rays was carried out in order to accelerate the reaction of unreacted photosensitive groups and strengthen the orientation. The birefringence of the substrate thus obtained is such that the ratios of the three main refractive indices are nx = 1.58, ny = 1.56, nz = 1.5, and the nx axis is the direction normal to the substrate surface. In contrast, the ratio of the 0-90 ° bend-aligned refractive index ellipse and the three main refractive indices is nx = 1.5.
5, ny = 1.5, and nz = 1.5, which was equivalent to a combination of uniaxially oriented films in which the nx axis was 0 ° with respect to the substrate surface normal direction.

Example 10 3.75% by weight of poly (4
-Methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25
Weight percent 4-pentyl-4′-cyanobiphenyl was dissolved in dichloroethane and coated on a glass substrate to a thickness of about 1.5 μm. The substrate is arranged so as to be inclined at 45 degrees with respect to the horizontal plane, and non-polarizing ultraviolet light [polarization degree = 0 (%)]
After irradiating 500 mJ / cm ² each from the front and back surfaces of the substrate at room temperature in the direction perpendicular to the horizontal plane, the substrate was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of unreacted photosensitive groups and strengthen the alignment, non-polarizing ultraviolet rays were irradiated at 1 J / cm ² . The birefringence of the substrate thus obtained is such that the ratio of the three main refractive indices is nx = 1.6, n
y = 1.53, nz = 1.5, and the ratio of the refractive index ellipse in which the nx axis is inclined 30 ° with respect to the substrate surface normal direction and the three main refractive indices is nx = 1.6, ny = 1. 5, nz = 1.5, which was equivalent to a combination of uniaxially oriented films in which the nx axis was 0 ° with respect to the substrate surface normal direction.

(Evaluation method) A coating film similar to that in Example 5 was used.
A layer formed on a TAC film having a phase difference of 40 nm in a direction inclined by 40 ° with respect to the normal direction of the film surface to a thickness of about 1.5 μm, and inclining the TAC film and a biaxial refractive index ellipsoid. Remove the polarizing sheet of Casio LCD color TV EV-510 from the retardation film
One sheet was attached to the upper surface or the lower surface of the liquid crystal cell, and then, one polarizing sheet (HEG1425DU manufactured by Nitto Denko) was attached to each of the upper and lower sides. The axial arrangement of each optical element was as shown in FIG. In FIG. 5, 61 is the retardation film of the present invention, and a is nx of the refractive index ellipsoid in the film.
The reference numeral 52 indicates a liquid crystal cell, and b, b '.
Indicates the pretilt direction, 53 and 53 ′ indicate polarizing sheets, and c and c ′ indicate the respective light absorption axis directions. When the liquid crystal color television was driven with such a configuration and the contrast ratio when white display and black display was 5 was defined as the viewing angle, the viewing angle in the vertical and horizontal directions was measured. To measure the contrast ratio, BM-5A made by Topcon
Was used. As shown in Table 1, it was also confirmed that when the retardation film produced in the example of the present invention was mounted on a liquid crystal display device, the viewing angle was enlarged by one sheet.

[0022]

[Table 1]

[0023]

EFFECTS OF THE INVENTION A film made of a photosensitive polymer having a positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound contains non-polarizing light or a completely polarized component and a non-polarized component. The three main refractive indices nx, ny, nz and n of the refractive index ellipsoid in the film are controlled by irradiating the
It was possible to manufacture a retardation film in which the inclination of the x-axis with respect to the normal to the film surface was controlled. Such a retardation film can be used as an optical compensation film for enlarging a viewing angle in a liquid crystal display device using a twisted nematic liquid crystal using an optical rotation mode and a birefringence mode. Conventionally, such a large area retardation film could not be produced at low cost, but according to the present invention, a simple operation of irradiating non-polarizing light or light in which a non-polarizing component and a non-polarizing component are mixed. Larger area is possible.

[0024]

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a method for producing a retardation film of the present invention.

FIG. 2 is a schematic diagram showing a side chain exposed by irradiation with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed.

FIG. 3 is a schematic diagram showing a film oriented by molecular motion after irradiation with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed.

FIG. 4 is a conceptual diagram showing a method for producing a retardation film of Example.

FIG. 5: Optical system when evaluating viewing angle characteristics

[Explanation of Codes] 11 ... Film (retardation film) 12 ... Refractive index ellipsoid nx (1a), ny (1b), nz (1c) ... Main refractive index (direction axis) L ... Light in which completely polarized components and non-polarized components are mixed Lp ... P component Ls ... S component

Continued front page    F term (reference) 2H049 BA06 BA42 BB42 BC02 BC05                       BC22                 2H091 FA11X FA11Z FC02 FC22                       FC23 GA06 LA19

Claims (11)

[Claims] 1. A film made of a photosensitive polymer having a positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound has a non-polarizing light or a completely polarizing component and a non-polarizing component. A method for producing a retardation film, wherein birefringence is controlled by an operation of irradiating mixed light. 2. A non-polarizing light or a completely polarized component and a non-polarized component are mixed in a film made of a photosensitive polymer having a positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound. The retardation film is characterized in that the ratio of the three main refractive indices nx, ny, nz of the refractive index ellipsoid in the film and the inclination of the nx axis with respect to the normal direction to the film surface are controlled by the operation of irradiating the light. Manufacturing method. 3. The control has the same birefringence as a combination of a tilt-aligned index ellipsoid, a bend-aligned index ellipsoid, or a non-tilted uniaxial index ellipsoid. The method for producing a retardation film according to claim 1, wherein the retardation film is expressed. 4. The method for producing a retardation film according to claim 1, wherein the photosensitive polymer containing the positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound. The method for producing a retardation film, comprising the steps of irradiating the film made of (1) with non-polarizing light or light in which a completely polarized component and a non-polarized component are mixed, and an operation of heating and cooling the film. 5. The method for producing a retardation film according to claim 1, wherein the photosensitive polymer containing the positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular compound is used. The method for producing a retardation film, comprising the step of irradiating the film made of with non-polarizing light or light with a mixture of a completely polarized component and a non-polarized component from both front and back directions. 6. The method for producing a retardation film according to claim 1, wherein the photosensitive polymer containing the positive refractive index ellipsoidal structure or a mixture of the polymer and a low molecular weight compound. The film made of is irradiated with non-polarizing light or light in which a completely polarized component and a non-polarized component are mixed, is made from a direction inclined with respect to the normal direction of the film surface. Manufacturing method. 7. The method for producing a retardation film according to claim 1, wherein the photosensitive polymer has liquid crystallinity. 8. The method for producing a retardation film according to claim 1, wherein the low molecular weight compound has crystallinity or liquid crystallinity. 9. The method for producing a retardation film according to claim 1, wherein the low molecular weight compound has a reactive group that is crosslinked or polymerized by light or heat. Method. 10. The method for producing a retardation film according to any one of claims 1 to 3, which comprises a step of crosslinking a photosensitive polymer or / and a low molecular weight compound. Method. 11. A retardation film produced by the method for producing a retardation film according to any one of claims 1 to 10.