JP2002202409A - Retardation film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a retardation film oriented in a molecular level and having the optical retardation and an optical axis direction arbitrarily produced in a polymer material and a method for manufacturing the same by making ultra violet rays irradiate a film of a mixture of a photosensitive polymer and a low molecular weight compound. SOLUTION: The mixture of the photosensitive polymer and the low molecular weight compound is applied on a substrate and film-formed. Side chains in the photosensitive polymer is made anisotropically to photo-react so as to induce birefringence in the film by making the ultraviolet rays irradiate the film using a device consisting of an ultraviolet lamp and a power source or an optical element transforming natural light to polarized light (e.g. a Glan- Taylor prism). The optical axis is oriented with arbitrary inclination by carrying out the irradiation from a direction inclined with respect to the film surface. As a result, the retardation film having the optical axis set to a desired direction is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a film of a mixture of a photosensitive polymer and a low-molecular compound, which is composed of a linearly polarized ultraviolet ray or an ultraviolet ray in which a completely polarized component and a non-polarized component are mixed or a non-polarized ultraviolet ray. Irradiation of ultraviolet rays (hereinafter referred to as exposure)
Accordingly, the present invention relates to a retardation film in which a molecular orientation is performed and a phase difference and an optical axis direction are arbitrarily developed in the polymer material, and a method for producing the same. (Particularly, a retardation film in which the 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 retardation film is a film having a birefringence which allows a linearly polarized light component oscillating in a principal axis direction perpendicular to each other to pass therethrough and gives a necessary phase difference between the two components.
Such a retardation film has been used in the field of liquid crystal display. In particular, a retardation film having an inclined optical axis is useful as an optical compensation film for expanding the viewing angle of a liquid crystal display device.
There are several conventional techniques for producing such a retardation film. One method is to stretch a polymer material such as polycarbonate, orient the polymer chains, and cause a difference between the refractive index in the stretching direction and the refractive index in the direction perpendicular to the stretching direction. Is that, because of the stretching step, molecules are oriented in the stretching direction, so that it is practically impossible to tilt the optical axis. JP-A-7-138308 discloses a method for developing a phase difference by polarized light exposure.
Polarized photopolymer such as polyvinyl cinnamate
Although a method of irradiating with UV light is described, in this method, anisotropy is expressed in a direction perpendicular to the electric field vibration of the irradiated polarized UV light, and the optical axis cannot be tilted, so that it is difficult to enlarge the viewing angle. . As a method for solving the above-mentioned problems, a method in which a liquid crystalline polymer or a liquid crystalline compound is fixed on a substrate on which an alignment treatment is performed is considered. Describes a method for aligning and fixing a liquid crystalline monomer on an alignment film obtained by oblique evaporation. Also, JP-A-7-287119,
JP-A-7-287120 also discloses a rubbing alignment film,
A method for arranging discotic liquid crystals on a SiO obliquely deposited alignment film is described.
No. 8123 describes a method of aligning a discotic liquid crystal containing a photopolymerization initiator on a photo-alignment film and fixing the alignment by light irradiation. However, in the method using an alignment film as described above, since the alignment treatment layer is provided, the alignment treatment of the alignment film, the alignment of the liquid crystal material, and the like become complicated, and a large-area retardation film having an inclined optical axis. Manufacturing costs increase. Further, as another method of manufacturing a retardation film having an inclined optical axis, a method of obliquely vapor-depositing an inorganic dielectric has been proposed, but in order to form a vapor-deposited film continuously on a long sheet. However, there are problems such as an increase in the size of the apparatus and a complicated process. The present inventor also proposed a method of manufacturing a retardation film having a tilted optical axis by polarizing exposure of a side chain type liquid crystalline polymer having photosensitivity in JP-A-10-278123. However, there is a problem that when the thickness of the film is increased in order to develop the haze, the degree of haze increases.

[0003]

In a retardation film produced by stretching a polymer film, the orientation of molecules is limited to the stretching direction, and it is extremely difficult to tilt the optical axis. On the other hand, a method of arranging a liquid crystalline compound on an alignment-treated substrate or a method of obliquely depositing an inorganic dielectric can produce a retardation film with an inclined optical axis, but the process is complicated. Therefore, a low-cost retardation film having a large-area optical axis inclined cannot be obtained. The present invention provides a retardation film having a low haze and suitable for mass production by a simple process, and a method for producing the same.

[0004]

According to the retardation film and the method for producing the same (retardation film) of the present invention, a mixture of a compatible photosensitive polymer and a low-molecular compound is formed and exposed. The photosensitive polymer and the low molecular compound can be oriented. When this exposure is performed in an oblique direction with respect to the film surface, the optical axis can be arbitrarily inclined for orientation, so that a retardation film in which the optical axis is set in a desired direction is realized.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The aforementioned photosensitive polymer is biphenyl, terphenyl, which is frequently used as a mesogen component of a liquid crystalline polymer,
Substituents such as phenylbenzoate and azobenzene,
It has a side chain containing a structure to which a photosensitive group such as a cinnamic acid group (or a derivative thereof) is bonded, and has a structure such as a hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, or siloxane in a main chain. It is a polymer. The polymer may be a homopolymer composed of the same repeating unit or a copolymer of units having different side chains having different structures, or it is also possible to copolymerize a unit having a side chain containing no photosensitive group. . The low-molecular compound to be mixed also has a substituent such as biphenyl, terphenyl, phenylbenzoate, or azobenzene, which is frequently used as a mesogen component. Functional group such as a derivative group) via a flexible component or
It is a compound having crystallinity or liquid crystallinity bonded without intervening. When mixing these low molecular weight compounds, not only a single compound but also a plurality of types of compounds can be mixed. A mixed solution of the photosensitive polymer and the low molecular compound is applied (spin-coated or cast) on a substrate to form a coating film. The film is isotropic at the time of film formation, and the side chain portion of the photosensitive polymer and the low molecular compound are not oriented in a specific direction. This state will be described with reference to FIG. The coating film 20 has a photosensitive group represented by a long ellipse and has an irradiated polarized ultraviolet ray L.
The side chain 2a having a high photosensitivity, the side chain 2b having a low photosensitivity, and the liquid crystal compound 2c represented by a cylinder are randomly distributed in the direction corresponding to the vibration direction m and the direction perpendicular to the irradiation light traveling direction. Coexist. When the film is subjected to polarized light exposure, the photoreaction of the side chains 2a arranged in a direction corresponding to the direction of the electric field oscillation of the irradiation light and the direction perpendicular to the direction of travel proceeds preferentially. In order to promote this photoreaction, irradiation of light having a wavelength at which the photosensitive groups of formulas 1 to 9 can react is required. This wavelength varies depending on the type of -R ₁ ~-R ₁₂ shown from Formula 1 in Formula 9, generally 200-5
00 nm, and in particular, the effectiveness of 250-400 nm is often high.

FIG. 3 shows the film 30 after the film 20 of FIG. 2 has been irradiated with light and the reaction has proceeded. As shown in FIG. 3, the side chain 3b (2b) of the polymer that did not cause a photoreaction and the low molecular compound 3c (2c) are reoriented by the molecular motion after the polarized light exposure. That is, the polymer side chain 3b (2b) and the low molecular compound 3c (2c), which did not cause a photoreaction, were not oriented perpendicularly to both the electric field oscillation direction of the polarized light and the irradiation light traveling direction. It is reoriented in the same direction as the reacted side chain 3a (2a). As a result, in the entire coating film, the side chains of the polymer and the molecules of the low-molecular compound are oriented in the direction of electric field oscillation of the irradiated linearly polarized light and in the direction perpendicular to the direction of irradiation light, birefringence is induced, and the retardation film and Become. The directions are different between polarized light exposure and non-polarized light exposure. At the time of non-polarized light exposure, the photoreaction of the side chains arranged in a direction corresponding to the direction perpendicular to the traveling direction of the irradiation light proceeds with priority. Because of the molecular motion after exposure, the polymer was placed in a direction parallel to the direction of irradiation light irradiation, so that the side chains of the polymer and the low-molecular compound in the film in the same direction as the side chains of the polymer that did not cause photoreaction. The molecules are oriented, and birefringence is induced to form a retardation film.
By performing this exposure in an oblique direction with respect to the film surface, the optical axis can be arbitrarily inclined for orientation.
As a result, a retardation film in which the optical axis is set in a desired direction can be provided. For measuring the tilt of the optical axis, Japanes
e Applied physics, Vol. 19,
The crystal rotation method described in 2013 (1980) for measuring the transmission intensity of polarized light while rotating a measurement sample was used. In this measuring method, the stereoscopic birefringence of a measurement sample can be measured from the angle dependence of the transmittance of polarized light.
The orientation by molecular motion after exposure 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 low molecular weight compounds. When the film that has been exposed and thus heated and the unreacted side chain is oriented or the film that has been exposed and oriented under heating is cooled below the softening point of the polymer, the molecules are frozen, and the oriented film of the present invention is obtained. Can be When the low-molecular compound has heat and / or photoreactivity with low-molecular compounds or with the polymer, the orientation is firmly fixed, so that improvement in heat resistance is expected. In such a case, it is necessary to control the density of photoreaction points by suppressing the amount of exposure or adjusting the reactivity so as not to hinder the molecular movement during reorientation.

[0007] The low molecular weight compound has an effect of suppressing the haze if it is in an appropriate amount.
This causes a decrease in orientation. From such a viewpoint, although it depends on the type of the photosensitive polymer or the low-molecular compound, a retardation film can be produced even when the low-molecular compound is added in an amount of 0.1 wt% to 80 wt%, but preferably 5 wt%. % To 5
Desirably, it is 0 wt%. Here, when the compatibility between the photosensitive polymer and the low molecular weight compound is not sufficient, a crystal having a size capable of inducing phase separation or scattering of visible light is generated by heating the substrate during film formation or after exposure. This causes an increase in cloudiness. In order to suppress the phase separation and the generation of microcrystals, it is necessary to adjust the compatibility between the polymer and the low molecular compound. As a measure of this compatibility, Polymer En
Gineering and Science, Vo
l. 7, No. 2,147 (1974), a solubility parameter (σ) calculated from the evaporation energy (ΔEv) and the molecular volume (V) by the calculation formula (1) can be used for convenience, The ratio of the solubility parameter (σ) of the low molecular compound: z is 0.93 <z <
Experiments have shown that when the ratio is in the range of 1.06, phase separation and generation of microcrystals can be effectively suppressed. σ = (ΔEv / V) ^1/2 calculation formula (1)

As a technique for increasing the film thickness and obtaining a larger phase difference, there is a method of laminating films. In this case, the material solution is applied and laminated on the film formed and exposed first,
In order to prevent the destruction of the previously formed film, it is effective to dissolve the polymer and the low-molecular compound in a solvent having reduced solubility. Further, by exposing the film of the mixture of the photosensitive polymer and the low-molecular compound from the front and back surfaces, the birefringence can be exhibited more efficiently. In this case, a mixture of the photosensitive polymer and the low-molecular compound is formed on the support by coating or the like, and the exposure may be performed directly on the film surface or via the support. When the support is interposed, the support may be made of any material as long as it has light transmittance of a wavelength that can react with the photosensitive polymer. Less is required, which is advantageous in the manufacturing process. Alternatively, a mixture of a photosensitive polymer and a low molecular compound may be formed on a peelable support, and after peeling, the film may be exposed from the front and back surfaces of the film.

A method for synthesizing a raw material compound and a low molecular compound of a photosensitive side chain type liquid crystalline polymer will be described below. (Monomer 1) 4,4′-biphenyldiol and 2-chloroethanol were heated under alkaline conditions to synthesize 4-hydroxy-4′-hydroxyethoxybiphenyl. Under alkaline conditions, the product
By reacting 6-dibromohexane, 4- (6-bromohexyloxy) -4′-hydroxyethoxybiphenyl was synthesized. Next, lithium methacrylate was reacted to synthesize 4-hydroxyethoxy-4 ′-(6′-biphenyloxyhexyl) methacrylate. Finally, cinnamoyl chloride was added under basic conditions to synthesize a methacrylic ester represented by Chemical Formula 13.

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(Monomer 2) 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 give 4-
(6-Bromohexyloxy) -4′-hydroxyethoxybiphenyl was synthesized. Next, lithium methacrylate was reacted to give 4-hydroxyethoxy-4′-
(6′-biphenyloxyhexyl) methacrylate was synthesized. Finally, under basic conditions, 4-methoxycinnamoyl chloride was added to synthesize a methacrylic acid ester represented by Chemical Formula 14.

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(Polymer 1) Polymer 1 is obtained by dissolving Monomer 1 in tetrahydrofuran and adding AIBN (azobisisobutyronitrile) as a reaction initiator to carry out polymerization.
Got. This polymer 1 exhibited liquid crystallinity in a temperature range of 47 to 75 ° C.

(Polymer 2) Polymer 2 was obtained by dissolving monomer 2 in tetrahydrofuran, adding AIBN as a reaction initiator, and polymerizing. This polymer 2 also exhibited liquid crystallinity.

(Low molecular weight compound 1) 4,4'-Biphenyldiol and 1,6-dibromohexane were reacted under alkaline conditions to synthesize 4,4'-bis (6-bromohexyloxy) biphenyl. Next, lithium methacrylate was reacted, and the product was purified by column to synthesize a low molecular compound 1 represented by Chemical Formula 15.

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(Low molecular weight compound 2) 4,4'-biphenyldiol and 2-chloroethanol are reacted under alkaline conditions to give 4,4'-bis (2-hydroxyethoxy)
Biphenyl was synthesized. Then, under basic conditions, cinnamoyl chloride was added and reacted, and the product was purified by column to synthesize a low-molecular compound 2 represented by Chemical Formula 16.

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(Low molecular weight compound 3) 4,4'-biphenyldiol and 6-bromohexanol were reacted under alkaline conditions to synthesize 4,4'-bis (6-bromohexyloxy) biphenyl. Then, under basic conditions, cinnamoyl chloride was added and reacted, and the product was purified by column to synthesize a low molecular compound 3 represented by Chemical Formula 17.

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(Low molecular weight compound 4) 4-Hydroxyethoxy-4 'is obtained by heating 4,4'-biphenyldiol and 6-bromohexanol under alkaline conditions.
-Hydroxyhexyloxybiphenyl was synthesized. This product is reacted with 1,6-dibromohexane under alkaline conditions to give 4- (6-bromohexyloxy)-
4′-Hydroxyhexyloxybiphenyl was synthesized. Then, lithium methacrylate was reacted and the product was purified by column to synthesize 4- (6-methacryloylhexyloxy) -4′-hydroxyhexyloxybiphenyl. Finally, under basic conditions, cinnamoyl chloride was added and reacted to synthesize a low-molecular compound 4 represented by Chemical Formula 18.

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[Low molecular weight compound 5 (comparative example)] 4,4'-
Biphenyldiol and 1,6-dibromodecane were reacted under alkaline conditions to synthesize 4,4′-bis (6-bromodecanyl) biphenyl. Next, a low molecular compound 5 represented by the chemical formula 19 was synthesized by reacting lithium methacrylate and purifying the product by a column.

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[Low Molecular Weight Compound 6 (Comparative Example)] Methyl 4-allyloxybenzoate was synthesized by heating methyl p-hydroxybenzoate and allyl bromide under alkaline conditions. The product is heated under alkaline conditions
-Allyloxybenzoic acid was synthesized. Then, the compound is reacted with thionyl chloride to synthesize 4-allyloxybenzoic acid chloride, and then reacted with hydroquinone to obtain a compound of the formula (2).
The low molecular compound 6 shown in No. 0 was synthesized.

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[0019]

FIG. 1 shows an example of a production method (apparatus) for producing a retardation film of the present invention by exposing it to linearly polarized ultraviolet light. However, the method for producing the retardation film of the present invention is not limited to this. Power supply 1
The disordered light 16 generated by the ultraviolet lamp 11 excited by the light 2 is converted into linearly polarized ultraviolet light 17 by an optical element 13 (for example, a Glan-Taylor prism).
The film 14 of the photosensitive side chain type liquid crystalline polymer and the liquid crystalline compound applied (coated) on the base material 15 is irradiated. Example 1
Examples 12 to 12 are examples in which a retardation film having an inclined optical axis was produced by the production method of the present invention.

Example 1 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 1 are dissolved in dichloroethane and placed on an optically isotropic substrate in a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 67 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 31 nm, and there was almost no haze, which was sufficient for practical use.

Example 2 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 2 are dissolved in dichloroethane, and about 1 μm thick on an optically isotropic substrate. Spin coated. The substrate was arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism at a room temperature in a direction perpendicular to the horizontal plane at 400 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 68 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 4 nm.

Example 3 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 3 are dissolved in dichloroethane, and about 1 μm thick on an optically isotropic substrate. Spin coated. The substrate was arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism at a room temperature in a direction perpendicular to the horizontal plane at 400 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 67 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 25 nm.

Example 4 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 4 are dissolved in dichloroethane and applied on an optically isotropic substrate to a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 200 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 67 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 43 nm.

EXAMPLE 5 3.75% by weight of Polymer 1 and 1.25% by weight of Monomer 1 are dissolved in dichloroethane and applied to an optically isotropic substrate to a thickness of about 1 μm. Spin coated. The substrate was placed at an angle of 45 degrees with respect to the horizontal plane, and the ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was irradiated at room temperature from a direction perpendicular to the horizontal plane at room temperature.
Irradiation was performed at 0 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained had an optical axis inclined by 69 ° from the normal direction of the substrate, and the phase difference in the substrate plane was 35 nm.

EXAMPLE 6 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 1 are dissolved in dichloroethane and applied to an optically isotropic substrate at a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 67 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 25 nm.

Example 7 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 2 are dissolved in dichloroethane, and about 1 μm thick on an optically isotropic substrate. Spin coated. The substrate was arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism at a room temperature in a direction perpendicular to the horizontal plane at 400 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 67 ° from the normal direction of the substrate.
The retardation in the plane of the substrate was 3 nm.

Example 8 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 3 are dissolved in dichloroethane and applied to an optically isotropic substrate at a thickness of about 1 μm. Spin coated. The substrate was arranged so as to be inclined by 45 degrees with respect to the horizontal plane, and irradiated with ultraviolet light converted to linearly polarized light using a Glan-Taylor prism at a room temperature in a direction perpendicular to the horizontal plane at 400 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is tilted by 65 ° from the normal direction of the substrate,
The in-plane retardation of the substrate was 23 nm.

Example 9 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 4 are dissolved in dichloroethane, and about 1 μm thick on an optically isotropic substrate. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 200 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis is inclined by 68 ° from the normal direction of the substrate.
The in-plane retardation of the substrate was 39 nm.

Example 10 3.75% by weight of polymer 2
And 1.25% by weight of Monomer 1 were dissolved in dichloroethane and spin-coated to a thickness of about 1 μm on an optically isotropic substrate. The substrate was placed at an angle of 45 degrees with respect to the horizontal plane, and the ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was applied at room temperature from a direction perpendicular to the horizontal plane at room temperature.
Irradiation was performed at 00 mJ / cm ² . Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained had an optical axis inclined by 67 ° from the normal direction of the substrate, and the phase difference in the substrate plane was 30 nm.

Example 11 3.75% by weight of polymer 1
And 1.25% by weight of the low-molecular compound 1 were dissolved in dichloroethane, and spin-coated at a thickness of about 1 μm on an optically isotropic substrate. The substrate was placed so as to be inclined 20 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 200 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. The optical axis of the substrate thus obtained was inclined by 81 ° from the normal direction of the substrate, and the phase difference in the substrate plane was 29 nm.

Example 12 3.75% by weight of polymer 1
And 1.25% by weight of the low-molecular compound 4 were dissolved in dichloroethane and spin-coated on an optically isotropic substrate to a thickness of about 1 μm. The substrate was placed so as to be inclined 20 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 200 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. In the substrate thus obtained, the optical axis was inclined by 80 ° from the normal direction of the substrate, and the phase difference in the substrate plane was 39 nm.

COMPARATIVE EXAMPLE 1 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 5 were dissolved in dichloroethane, and were applied to an optically isotropic substrate at a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained was cloudy and was not suitable for practical use.

COMPARATIVE EXAMPLE 2 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 6 were dissolved in dichloroethane, and about 1 μm thick on an optically isotropic substrate. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained was cloudy and was not suitable for practical use.

COMPARATIVE EXAMPLE 3 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 5 were dissolved in dichloroethane and placed on an optically isotropic substrate in a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained was cloudy and was not suitable for practical use.

COMPARATIVE EXAMPLE 4 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 6 were dissolved in dichloroethane, and were applied to an optically isotropic substrate at a thickness of about 1 μm. Spin coated. The substrate was placed to be inclined 45 degrees relative to the horizontal plane, the ultraviolet light is converted into linearly polarized light using a ground Taylor prism, and 100 mJ / cm ² irradiation at room temperature from a vertical direction with respect to the horizontal plane. Subsequently, after heating to 100 ° C., it was cooled to room temperature. The substrate thus obtained was cloudy and was not suitable for practical use.

Examples 1 to 12 and Comparative Examples 1 to 4
Table 1 summarizes the results. From these examples, it is possible to suppress the haze by exposure and effectively obtain a phase difference,
It was proved that a film in which the optical axis direction was controlled could be produced. In the retardation film of the present invention and its production method,
By irradiating the film, which has caused birefringence by exposure, with ultraviolet rays, the photoreaction of unreacted photosensitive groups can be promoted, and the orientation in the film can be firmly fixed.
Such a retardation film was excellent in heat resistance and light stability and was sufficient for practical use.

[Table 1]

[0037]

By the simple operation of exposure, a retardation film can be obtained without using a stretching step as in the prior art. Further, by changing the irradiation direction of the ultraviolet light, it is possible to produce regions having different optical axes in the same substrate, and it is expected to be used for various optical elements. Further, the retardation 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 large-area retardation film with an inclined optical axis could not be produced at low cost. However, the present invention makes it possible to increase the area by a simple operation of exposing from an oblique direction. Was.

[0038]

[Brief description of the drawings]

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

FIG. 2 is a schematic view of a side chain exposed by polarized light exposure.

FIG. 3 is a schematic diagram 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 ... Film (film) 15 ... Substrate 16 ... Disordered light 17 ... Linear polarization UV light

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13363 G02F 1/13363 F-term (Reference) 2H049 BA06 BA42 BB42 BC01 BC05 BC22 2H091 FA11X FA11Z FB02 FC22 FC23 LA12 LA19 4J011 AC04 PA69 PA74 PA99 PC02 QA03 QA08 UA01 VA01 WA01 WA10 4J026 AA45 AA50 AB44 AC09 BA27 BA34 BB01 DB06 DB36 GA08

Claims (7)

[Claims] 1. A method comprising irradiating a mixture of a photosensitive polymer and a low-molecular compound with light to produce a mixture of the photosensitive polymer and the low-molecular compound. When the parameter ratio z is 0.93 <
A retardation film and a method for producing the same, wherein z <1.06. 2. The retardation film according to claim 1, wherein the photosensitive polymer has liquid crystallinity, and a method for producing the same. 3. The photosensitive polymer according to claim 1, wherein at least one of the photosensitive polymers has at least one structure represented by the chemical formulas 1 to 9, and the main chain represented by the chemical formula 10 is a hydrocarbon. , Acrylate, methacrylate, maleimide, N-phenylmaleimide, a photosensitive homopolymer or copolymer such as siloxane,
A retardation film, wherein the low molecular compound has a molecular structure represented by Chemical Formula 11 or Chemical Formula 12, and a method for producing the same. Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image _{However, -R 1 ~-R 11 =} -H, halogen, -CN, alkyl such as an alkyl group or their fluoride and groups, -R ₁₂ = methyl group, an ethyl group, such as an alkyl group or a methoxy group A group or a group obtained by fluorinating them;
x: y = 100-0: 0-100, n = 1-12, m =
1-12, j = 1-12, o = 1-12, p = 1-1
2, q = 1 to 12, X, Y = none, -COO, -O
CO -, - N = N - , - C = C-or-C 6 H 4 -, W 1,
W ₂ , W ₃ , W ₄ , W ₅ , W ₆ = a structure represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, Chemical Formula 4, Chemical Formula 5, Chemical Formula 6, Chemical Formula 7, Chemical Formula 8, or Chemical Formula 9. 4. A retardation film in which light irradiated in claim 1, 2 or 3 is a mixture of linearly polarized light or perfectly polarized light and non-polarized light, and a method for producing the same. 5. The method according to claim 1, wherein the film of the mixture of the photosensitive polymer and the low molecular weight compound is irradiated with light from both directions of the front and back surfaces. A retardation film and a method for producing the same. 6. The retardation film and the method for producing the retardation film according to claim 1, 2, 3, 4, and 5, further comprising a step of heating and / or cooling. Retardation film and method for producing the same. 7. The retardation film and the method for producing the retardation film according to claim 1, 2, 3, 4, 5, and 6, the photosensitive polymer constituting the film. Or a method for producing a retardation film, comprising a step of crosslinking a low molecular compound.