JP2002090540A - Birefringent film and method for producing the same - Google Patents

Abstract

(57) [Abstract] [Object] A birefringent film (optical compensation film) having a tilted optical axis prepared by polarizing exposure of a laminated photoreactive polymer material, and a method for producing the same. A photoreactive polymer material represented by Chemical Formula 10 is applied on a substrate to form a film. In the film, the side chains of the polymer material are non-oriented, but when subjected to polarized light exposure using a device comprising an ultraviolet lamp, a power supply, and a polarizing element (for example, a Glan-Taylor prism), it follows the direction of the electric field oscillation of the irradiation light, and The crosslinking reaction proceeds selectively only between the side chain photosensitive components arranged in the direction perpendicular to the irradiation light traveling direction to fix the arrangement. Since they are not arranged in the direction of the electric field oscillation of the irradiation light and in the direction perpendicular to the direction of the irradiation light, the unreacted side chains are arranged in the same direction as the photoreacted portion due to the molecular motion after the polarization exposure. As a result, all the side chains in the polymer coating film are arranged in the direction of the electric field oscillation of the irradiation light and in the direction perpendicular to the direction of the irradiation light. By repeating the application of the polymer material and the exposure of polarized light in this manner, lamination is performed, and a birefringent film having an arbitrary phase difference and optical axis can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a photosensitive side-chain type polymer liquid crystal film with linearly polarized ultraviolet rays to orient the molecules, thereby causing a phase difference and an optical axis direction in the polymer material. And a method for producing the same. (Especially, a birefringent film whose optical axis is inclined with respect to the film surface is effective for expanding the viewing angle in a liquid crystal display device.)

[0002]

2. Description of the Related Art A birefringent film is a film having a birefringence that allows a linearly polarized light component oscillating in a direction of a principal axis perpendicular to each other to pass therethrough and gives a necessary phase difference between the two components.
Conventionally, such a birefringent film is stretched by stretching a polymer material such as polycarbonate, orienting the polymer chains, and causing a difference between the refractive index in the stretching direction and the refractive index in the direction perpendicular to the stretching direction. Film is widely used. Such birefringent films have been used in the field of liquid crystal displays. In particular, birefringent films having an inclined optical axis are effective as optical compensation films for expanding the viewing angle of liquid crystal display devices.

[0003] Compared with a CRT display device, the liquid crystal display device is "flat and can be installed even in a small space", "light and easy to carry", and is adapted to high-speed video communication because it is a digital image. , And "low power consumption due to driving at low voltage", and is rapidly growing as a powerful video information display means. Many of the currently popular liquid crystal display devices use a twisted nematic liquid crystal.

[0004] Liquid crystal molecules exhibit birefringence because they have different refractive indexes in the major axis direction and the minor axis direction of the molecules. As shown in FIG. 2, there is a phase difference between the case where light is perpendicularly incident on such a birefringent body and the case where light is incident obliquely. As shown in FIG. 2, when a space having an α-axis, a β-axis, and a γ-axis is formed in the liquid crystal, the refractive index is anisotropic ellipsoid (21
0). In a liquid crystal display device having a structure in which a liquid crystal is sandwiched between two polarizers, such optical anisotropy causes a viewing angle characteristic in which a display color and a display contrast change depending on a viewing direction. That is, even if the emitted light is the same, the visual field (211) in the direction of the major axis (201) of the refractive index ellipsoid is different from the visual field (212) in the direction shifted from the major axis of the refractive index ellipsoid. . Since this kind of viewing angle characteristic lowers the visibility of the liquid crystal display device, development of a birefringent film (and a rational manufacturing method thereof) having an optional optical compensation function suitable for solving the problem has been an issue. I have.

On the other hand, as shown in FIG. 3, the refractive index ellipsoid of the liquid crystal molecules arranged obliquely by the pretilt angle at the interface with the alignment film for aligning the liquid crystal molecules,
There have been proposals (literature or patent) for compensating by disposing a refractive index ellipsoid obliquely. The major axis (2
Above the liquid crystal layer (200) containing the refractive index ellipsoid (310) having the major axis (301).
Birefringent film having optical anisotropy represented by
0), the field of view (211) and the field of view (2)
The brightness and the like sensed in 12) are homogenized. A technique for manufacturing a birefringent film having such arbitrary optical characteristics (tilt of the optical axis) is required.

In order to improve the viewing angle characteristics, use of a birefringent film has been proposed.
Japanese Patent Application Laid-Open No. 3-291601 discloses a method in which a polymer liquid crystal is applied to a substrate on which an alignment film is formed to form an optical compensation film. in this way,
Since the molecules are arranged in a direction perpendicular to the substrate, the viewing angle characteristics have not been sufficiently improved. JP 4
No.-113301 and JP-A-5-80323,
A method of obliquely slicing uniaxial polycarbonate is described. However, with this method, it is difficult to obtain a large-area birefringent film at low cost. JP-A-5-58
No. 23 describes a method using a photoisomerizable substance, but the birefringent film obtained by the method has insufficient heat and light stability. JP-A-7-287119 and JP-A-7-287120 also describe a method of applying a discotic liquid crystal to a rubbing alignment film or a SiO oblique deposition alignment film and heating / cooling the same. Since it is used, it is difficult to obtain an optical compensation film at low cost. Japanese Patent Application Laid-Open No. H11-189665 discloses a method in which a polymer coating film containing a photosensitive group is irradiated with linearly polarized ultraviolet rays to promote a dimerization reaction of the photosensitive group and tilt the optical axis in an arbitrary direction. Has been described. In order to exhibit a sufficiently large phase difference by this method, the film thickness must be increased, but when the film thickness is increased, haze (cloudiness) is generated, and it is difficult to use the film.

[0007]

The retardation of a birefringent film produced by stretching the polymer film is determined by the product of the birefringence caused by the orientation and the thickness of the stretched film. For this reason, in the stretched film, it is necessary to precisely control the stretching degree and the thickness on the entire surface of the film, and it has been difficult to accurately and uniformly maintain the retardation.
In addition, since the molecules are oriented in the stretching direction by the stretching process, it is substantially impossible to tilt the optical axis. As a birefringent element with a tilted optical axis, an inorganic crystal such as calcite may be cut obliquely to the optical axis and the surface polished, but these inorganic crystals have small anisotropy in refractive index. However, the thickness of the optical element becomes considerably thick, resulting in high cost. Therefore, it is impossible to obtain a thin-layer optical element having a large-area optical axis inclined at a low cost. The present invention provides a method for producing a birefringent film that has solved the above problems.

[0008]

Means for Solving the Problems An object of the present invention is to provide a method for producing a birefringent film which is excellent in thermal stability and light stability while controlling the phase difference of light and the direction of an optical axis. A birefringent film characterized by laminating at least two layers of photosensitive side-chain type polymer films and irradiating it with linearly polarized light to obtain a birefringent film having any phase difference and any optical axis direction. The method for producing a birefringent film, wherein the side chain comprises at least one structure represented by Chemical Formula 1 to Chemical Formula 7 as a structure of the photosensitive side chain type polymer compound, The side chain of the side chain type polymer contains a structure represented by Formula 8 or 9 and has a structure represented by Formula 10
A method for producing a birefringent film, wherein the main chain represented by has a structure of hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, siloxane, or the like, A method for producing a birefringent film, wherein the temperature of the hydrophilic side-chain type polymer film is within a range of 10 ° C. or less from the transition temperature of the side-chain type polymer to the isotropic phase. A method for producing a birefringent film, comprising a step of heating and / or cooling the side chain type polymer or a support thereof.
And a birefringent film obtained by the method for producing a birefringent film.

[0009]

The production method of the present invention and the birefringent film obtained by this production method have the following unique optical functions. The orientation of side chains can be controlled by irradiation with linearly polarized ultraviolet light and by the copolymer composition.
Further, by laminating the birefringent films, the phase difference of light can be controlled. As a result, a birefringent film having an optical axis inclined with respect to the film surface and having an arbitrary phase difference is realized.

By forming a film using the polymer of the present invention and irradiating a linearly polarized ultraviolet ray from a specific direction, a direction parallel to the electric field vibration direction of the linearly polarized ultraviolet ray irradiated on the side chain of the polymer is obtained. A birefringent film oriented in the direction perpendicular to the direction of irradiation light can be produced. By performing the irradiation in an oblique direction with respect to the film surface, the side chains of the polymer can be tilted and oriented, and the tilt can be set in any direction by changing the incident angle of light. Here, the side chain represented by the chemical formulas 8 and 9 is a refractive index ellipsoid having a long axis and a short axis, and becomes a material exhibiting birefringence when the side chain is oriented. The polymer film in which the side chains are inclined is a birefringent film in which the optical axis is inclined. The degree of side chain orientation is controlled by the irradiation amount of linearly polarized ultraviolet light, and the phase difference can be controlled by the degree of side chain orientation. Furthermore, the retardation of the birefringent film is determined by the product of the birefringence caused by the orientation and the film thickness. Therefore, by controlling the thickness of the polymer coating film and the number of the laminated layers, an arbitrary size can be obtained. A birefringent film having a phase difference can be produced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The above-mentioned homopolymer or copolymer includes a substituent such as biphenyl, terphenyl, phenylbenzoate, or azobenzene, which is frequently used as a mesogen component of a liquid crystalline polymer, and a cinnamic acid group (or a derivative group thereof). Having a side chain containing a structure to which a photosensitive group is bonded and containing a proportion of a side chain containing a mesogen component to which a photosensitive group is not bonded or a side chain not containing a mesogen component to which a photosensitive group is bonded. , A polymer having a structure such as hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, or siloxane in the main chain.

The polymer solution is applied (spin-coated) on a substrate to form a polymer coating film. The polymer coating film is non-oriented at the time of film formation, and the photosensitive side chain does not face a specific direction. This state will be described with reference to FIG. 4. In the coating film (40), a photosensitive side chain (41) indicated by a long ellipse and corresponding to the direction of the electric field oscillation of the irradiation linearly polarized light.
And the side chain (42) having poor photosensitivity exist in a non-oriented state. When the film is irradiated with a linearly polarized ultraviolet ray, a photosensitive group such as a cinnamic acid group (or a derivative group thereof) disposed in a direction perpendicular to the electric field oscillation direction D1 and the irradiation light traveling direction D2 of the irradiated linearly polarized light. The dimerization of 41) occurs most sharply. This dimerization reaction forms a cyclobutane ring as shown in Reaction Formula 1. To proceed with this dimerization reaction, linearly polarized light having a wavelength at which the photosensitive group portion of Chemical Formulas 1 to 7 can react is used. Irradiation is required. This wavelength varies from Formula 1 according to the type of -R ₁ ~-R ₁₁ shown by Formula 7, generally a 200-500 nm,
In particular, the effectiveness of 250 to 400 nm is often high.

[0013]

Embedded image The rectangle described in the reaction formula 1 is a molecular chain connecting the main chain of the polymer and the photosensitive group in the side chain type polymer liquid crystal, and includes a mesogen component and a bent component.

Even if there is a side chain having no photosensitive group or a photosensitive group, dimerization does not occur because they are not arranged in the direction of electric field oscillation of linearly polarized light and in the direction perpendicular to the direction of irradiation light travel. As shown in FIG. 5, the side chains (42) are arranged in the same direction as the dimerized side chains (51) due to the molecular motion after the light irradiation. As a result, the entire polymer coating film (5
In 0), the side chains are arranged in a direction perpendicular to the electric field oscillation direction D1 and the irradiation light traveling direction D2 of the irradiated linearly polarized light.

The alignment by the molecular motion after the light irradiation is promoted by heating the substrate. The heating temperature of the substrate is desirably lower than the softening point of the photoreacted portion and higher than the softening points of the unreacted side chains and the side chain portions having no photosensitive group. In addition, under heating (from room temperature to _Ti
Polarization exposure at up to + 10 ° C.) can promote alignment. Here, _Ti indicates a phase transition temperature when the liquid crystal phase changes to an isotropic phase. Preferably, it is effective to perform polarized light exposure around T _i . When the film subjected to the polarized light exposure and heated and the unreacted side chains are arranged or the film subjected to the polarized light exposure and orientation under heating is cooled to the softening point temperature of the polymer or less, the molecules are frozen, and the molecules of the present invention are frozen. A refractive film is obtained. Here, the side chain having no photosensitive group is light 2
It lowers the density of cross-linking points in the quantification reaction, improves the degree of freedom of molecular motion during reorientation, and promotes reorientation by its own molecular orientation.

In the present invention, the polymer film after light irradiation can be further coated with a film. When the laminated film is irradiated with linearly polarized ultraviolet light, similarly to the above, dimerization of the photosensitive group disposed in the direction of the electric field oscillation of the linearly polarized light and in the direction perpendicular to the direction of the irradiation light occurs. Side chains that do not undergo dimerization because they are not aligned in the direction of electric field oscillation of linearly polarized light and in the direction perpendicular to the direction of irradiation light even though they have a photosensitive group or a photosensitive group. Are arranged in the same direction as the dimerized side chain by the subsequent molecular motion. As a result, as in the first layer, the side chains are arranged in the direction of the electric field oscillation of the irradiated linearly polarized light and in the direction perpendicular to the traveling direction of the irradiation light. Since the retardation of the birefringent film is determined by the product of the birefringence caused by the orientation and the thickness of the film, a birefringent film having transmitted light having an arbitrary magnitude of retardation can be obtained by this lamination. In addition, in order to exhibit a sufficiently large phase difference, it has been necessary to increase the film thickness. Therefore, haze has been generated. However, in this method, it is effective to reduce the film thickness per layer sufficiently. The haze can be suppressed effectively.

A method for synthesizing a raw material compound of a polymer material will be described below. (Monomer 1) 4,4′-biphenyldiol and 2-chloroethanol were heated under alkaline conditions to synthesize 4-hydroxy-4′-hydroxyethoxybiphenyl. This product is added under alkaline conditions with 1,
6-Dibromohexane was reacted to synthesize 4- (6-bromohexyloxy) -4′-hydroxyethoxybiphenyl. Next, lithium methacrylate was reacted to synthesize 4-hydroxyethoxy-4 ′-(6-methacryloylhexyloxy) biphenyl. Finally,
Under basic conditions, cinnamoyl chloride was added to synthesize a methacrylic ester represented by Chemical Formula 11.

Embedded image

(Monomer 2) 4-hydroxy-4'-cyanobiphenyl is reacted with 1,6-dibromohexane under alkaline conditions to give 4- (6-bromohexyloxy)-
4′-cyanobiphenyl was synthesized. Next, lithium methacrylate was reacted to synthesize a methacrylate ester represented by the chemical formula 12.

Embedded image

(Monomer 3) 4-Hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chlorohexanol under alkaline conditions. This product was reacted with 1,6-dibromohexane under alkaline conditions to obtain 4-
(6-Bromohexyloxy) -4′-hydroxyethoxybiphenyl was synthesized. Next, lithium methacrylate was reacted to give 4-hydroxyethoxy-4′-
(6-Methacryloylhexyloxy) biphenyl was synthesized. Finally, under basic conditions, 4-methoxycinnamoyl chloride was added to synthesize a methacrylic acid ester represented by Chemical Formula 13.

Embedded image

(Polymer 1) Polymer 1 is obtained by dissolving Monomer 1 and Monomer 2 in tetrahydrofuran, adding AIBN (azobisisobutyronitrile) as a reaction initiator, and polymerizing. (X: y = 29: 71). This polymer 1 exhibited liquid crystallinity in a temperature range of 46 to 101 ° C.

(Polymer 2) Polymer 1 was obtained by dissolving Monomer 1 and Monomer 2 in tetrahydrofuran and adding AIBN as a reaction initiator to carry out polymerization (x: y = 4).
7:53). This polymer 2 exhibited liquid crystallinity in a temperature range of 47-95 ° C.

(Polymer 3) Monomer 1 and Monomer 2 were dissolved in tetrahydrofuran, and AIBN was added as a reaction initiator and polymerized to obtain Polymer 3 (x: y = 8).
0:20). This polymer 3 exhibited liquid crystallinity in a temperature range of 42 to 75 ° C.

(Polymer 4) Polymer 4 was obtained by dissolving monomer 3 in tetrahydrofuran, adding AIBN as a reaction initiator, and polymerizing. This polymer 4 also exhibited liquid crystallinity.

The polymer material of the present invention was confirmed to be a liquid crystal material from the appearance of a phase transition temperature by thermal analysis and the appearance of a birefringent optical pattern in the liquid crystal temperature range by observation with a polarizing microscope. . In the chemical formula 10, x: y: z =
47: 53: 0, n = 6, m = 2, k = 6, X, Y = n
_one, W ₁ = formula _{1, W 2 = -CN, -R} 1 ~-R 7 =
H, the thermal analysis curve of the polymer material of the present invention in which the main chain is methacrylate shows an endothermic peak at 47 ° C. during the temperature rise process, and 95 ° C.
An endothermic peak was also observed, and it was a liquid crystal material that exhibited a birefringent optical pattern in the temperature region under observation with a polarizing microscope.

FIG. 1 shows a method (apparatus) for producing a liquid crystal alignment film using the polymer of the present invention. The unpolarized light (1) generated by the ultraviolet lamp (11) excited by the power supply (12)
6) is converted into polarized ultraviolet light (17) via an optical element (13) (for example, a Glan-Taylor prism), and is applied to the resin film (14) applied on the substrate (15) (in the normal direction of the substrate). The irradiation is not limited to this.)

EXAMPLES Examples 1 to 9 are examples in which a birefringent film having an inclined optical axis was produced using the polymer material of the present invention.

(Example 1) Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be inclined by 20 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 15 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. Crystal rotation method (Liquid Crystal Research Group: “The Latest in Liquid Crystal Display”,
(1983), the orientation angle of the side chain was measured, and it was confirmed that the optical axis was approximately 20 degrees with respect to the horizontal plane. The in-plane retardation of this substrate is 250 nm.
Met.

Example 2 Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be tilted by 20 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 20 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 380 nm.

Example 3 Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and was irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism at room temperature from a direction perpendicular to the horizontal plane. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 30 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 350 nm.

Example 4 Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and ultraviolet irradiation were repeated, and the substrate having 30 layers was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 30 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 570 nm.

Example 5 Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 150 nm on an optically isotropic substrate. The substrate was arranged so as to be tilted by 20 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted into linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by the crystal rotation method.
Degree was confirmed. The in-plane retardation of this substrate was 630 nm.

Example 6 Polymer 1 was dissolved in chloroform and spin-coated with a thickness of about 45 nm on an optically isotropic substrate. The substrate was arranged so as to be tilted by 20 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted into linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 20 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 190 nm.

Example 7 The polymer 2 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 30 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 260 nm.

Example 8 The polymer 3 was dissolved in chloroform, and one layer of about 90 nm was spin-coated on an optically isotropic substrate. The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 30 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 170 nm.

Example 9 The polymer 4 was dissolved in chloroform and spin-coated with a thickness of about 90 nm on an optically isotropic substrate. The substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 20 seconds. Spin coating and irradiation with ultraviolet light were repeated, and the substrate having 20 layers laminated was heated at 100 ° C. for 10 minutes and then cooled to room temperature. The orientation angle of the side chain was measured by a crystal rotation method, and it was confirmed that the optical axis was approximately 30 degrees with respect to the horizontal plane. The in-plane retardation of this substrate was 85 nm.

From these examples, it was proved that a relatively simple method of irradiating linearly polarized light from an oblique direction enables the production of a birefringent film in which the optical axis is inclined and the phase difference is controlled. Also, these have almost no haze,
It was enough for practical use.

[0036]

[Table 1]

[0037]

According to the simple operation of irradiating linearly polarized light,
A birefringent film can be obtained without using a stretching step as in the prior art. Furthermore, by changing the number of layers, a birefringent film having an arbitrary phase difference can be manufactured. In addition, by changing the irradiation amount of polarized ultraviolet light, regions having different phase differences can be manufactured in the same substrate. Is also possible, and it is expected to be used for various optical elements. Also,
In the birefringent film of the polymer material of the present invention, a film in which side chains are oriented by irradiation of linearly polarized ultraviolet rays is further irradiated with ultraviolet rays to promote a dimerization reaction of a photosensitive group, thereby strengthening the orientation of side chains. Can be fixed. Such a birefringent film was excellent in heat resistance and light stability and was sufficient for practical use. A birefringent film having an inclined optical axis can be used as an optical compensation film for expanding a viewing angle in a liquid crystal display device using a twisted nematic liquid crystal utilizing an optical rotation mode and a birefringence mode. Conventionally, such a birefringent film having an inclined optical axis could not be produced at a low cost in a large area. However, according to the present invention, the optical axis was inclined by a simple operation of irradiating linearly polarized light obliquely. Large-sized birefringent films can also be manufactured.

[0038]

[Brief description of the drawings]

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

FIG. 2 is an explanatory conceptual diagram of refractive index anisotropy depending on a viewing direction of liquid crystal molecules.

FIG. 3 is an explanatory view of a refractive index ellipsoid for optically compensating for the refractive index anisotropy of liquid crystal molecules.

FIG. 4 is a schematic view of a side chain exposed by oblique polarization exposure.

FIG. 5 is a schematic view of side chains arranged by molecular motion after polarized light exposure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ultraviolet lamp 12 ... Power supply 13 ... Optical element (Glan-Taylor prism) 14 ... Resin film (polymer) 15 ... Substrate 16 ... Non-polarized light 17 ... Polarized ultraviolet light 40 ... Polymer coating film 41 ... Side chain exposed 42 ... Side chain hardly exposed

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // B29D 11/00 B29D 11/00 C08L 33:14 C08L 33:14 F term (reference) 2H049 BA12 BA42 BC05 BC09 BC22 4F073 AA32 BA18 BB01 CA45 4F100 AK01A AK01B AK24A AK24B AK25A AK25B AK49A AK49B AK52A AK52B BA02 EJ54 JN17A JN17B JN18 4F213 AA21 AA34 AH34 AP06 AP11 WA18 WB07 WB02 AL08P AL08Q AL71P AL71Q BA02P BA02Q BA05P BA05Q BA15P BA15Q BA40P BA40Q BA45P BA45Q BB01P BB01Q BC04P BC04Q BC43P BC43Q BC44P BC44Q CA01 CA04 DA66 JA39

Claims (6)

[Claims] 1. A photosensitive side-chain type polymer film having at least two
Laminate more than one layer, irradiate it with linearly polarized ultraviolet light,
A method for producing a birefringent film, characterized in that a uniaxial birefringent film having an optical axis inclined in an arbitrary direction is obtained. 2. The method for producing a birefringent film according to claim 1, wherein the photosensitive side chain-type polymer has at least one structure represented by Chemical Formula 1 to Chemical Formula 7 in the side chain. A method for producing a birefringent film. Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image _{However, -R 1 ~R 11 = -H,} -CN, halogen group, an alkyl group such as an alkyl group or a methoxy group. 3. The method for producing a birefringent film according to claim 1, wherein the side chain of the photosensitive side-chain type polymer includes a structure represented by Chemical Formula 8 or 9 and a main chain represented by Chemical Formula 10. Has a structure of hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, siloxane or the like. Embedded image Embedded image Embedded image Where x + y + z = 1, n = 1 to 12, m = 1 to 12,
k = 1 to 12, X, Y = none, -COO, -OC
O, -N = N -, - C = C-or-C 6 H 4 -, - R 1 ~
R ₁₁ = -H, -CN, alkyl group such as a halogen group, an alkyl group or a methoxy _{group, W 1, W 2, W} 3 = -
H, -CN, a halogen group, an alkyl group, an alkoxy group,
An alkenyl group, an alkenyloxy group, a cyclohexyl group, a cyclohexenyl group and a group obtained by fluorinating them, at least one of which is any one of the chemical formula 1, the chemical formula 2, the chemical formula 3, the chemical formula 4, the chemical formula 5, the chemical formula 6, or the chemical formula 7 It is a structure represented by 4. The method for producing a birefringent film according to claim 1, wherein the temperature of the photosensitive side-chain type polymer film when irradiating linearly polarized ultraviolet light is changed to an isotropic phase of the side-chain type polymer. A method for producing a birefringent film, wherein the difference from the transition temperature is within 10 ° C. 5. The method for producing a birefringent film according to claim 1, further comprising a step of heating and / or cooling the photosensitive side chain type polymer film or its support. Production method. 6. A birefringent film obtained by the method for producing a birefringent film according to claim 1.