JP2002202408A - Retardation film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a retardation film having significant wavelength dispersion and temperature compensation effect to transmitted light and a controlled opti cal axis direction and a method for manufacturing the same by exposing and orienting in a molecular level a film of a mixture of a photosensitive polymer and a low molecular weight compound. SOLUTION: The film of the mixture of the photosensitive polymer and the low molecular weight compound is formed. The retardation film having the significant wavelength dispersion and the temperature compensation effect toward the transmitted light is obtained by exposing 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) and enhancing a photoreaction of photosensitive groups aligned in a specified direction. 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 significant wavelength dispersion and the temperature compensation effect toward the transmitted light and the optic axis set to a desired direction is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film of a mixture of a photosensitive polymer and a low-molecular compound, which is irradiated with ultraviolet rays (hereinafter referred to as "exposure") to orient the molecules, thereby providing a large wavelength dispersion and a high temperature. The present invention relates to a retardation film in which a compensation effect and an optical axis direction are arbitrarily expressed, 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 phase difference film is required for monochrome or color conversion in an STN type liquid crystal display device. This retardation film is a film having a birefringence that allows a linearly polarized light component oscillating in a main axis direction perpendicular to each other to pass and provides a necessary phase difference between the two components, and has been transmitted through an STN type liquid crystal cell. , G, B elliptically polarized light is reduced, or the principal axes of R, G, B elliptically polarized light are rotated in a certain direction, thereby enabling monochrome or colorization. As such a retardation film, there is a film in which a polymer material such as polycarbonate is stretched, polymer chains are oriented, and a difference is caused between a refractive index in a stretching direction and a refractive index in a direction orthogonal to the stretching direction. . However, in a liquid crystal display device requiring high-speed response, a liquid crystal material having a large birefringence is used, so that the wavelength dispersion of the liquid crystal cell becomes large. To compensate for this, a retardation film having a large wavelength dispersion is desired. ing. Further, since the retardation of the STN-type liquid crystal cell changes with an increase in temperature, when the liquid crystal display device is used for a vehicle, color shift occurs at a high temperature and the display characteristics deteriorate. This is because, in a liquid crystal cell of an STN liquid crystal display device, the temperature rise causes relaxation of the alignment of liquid crystal molecules. To solve these problems, a two-layer STN type liquid crystal display device using a liquid crystal cell for optical compensation can be considered, but there are problems such as an increase in the weight, thickness, and cost of the liquid crystal display device. . In a retardation film obtained by stretching a polymer material such as polycarbonate, the wavelength dispersion is small and the optical compensation effect cannot be sufficiently obtained. Examples of the retardation film having a large wavelength dispersion include retardation films obtained by stretching a polymer material such as polyarylate, polysulfone, polyethersulfone, and aromatic polyester. However, in the retardation film in which these polymers are oriented, the relaxation of the molecular orientation at high temperature is small, and the retardation of the liquid crystal cell and the retardation film adjusted to show the best display characteristics at room temperature is high. In such a case, the optical compensation effect is not sufficiently obtained due to deviation from the optimum condition. Furthermore, three-dimensional control of the refractive index of the retardation film is also important in improving the viewing angle characteristics of the liquid crystal display device, and tilting the optical axis is useful for expanding the viewing angle of the liquid crystal display device. In the stretched retardation film, since the molecules are oriented in the stretching direction, it is substantially impossible to tilt the optical axis, and the effect of expanding the viewing angle becomes insufficient.
As a method for developing a phase difference by polarized light exposure, JP-A-7-138308 describes a method of irradiating a photosensitive polymer such as polyvinyl cinnamate with polarized UV light. Since the optical axis cannot be tilted due to the occurrence of anisotropy in the direction perpendicular to the electric field vibration, it is difficult to enlarge the viewing angle. As a method for solving the above-mentioned problem, a method in which a liquid crystalline polymer or a liquid crystalline compound is fixed on a substrate on which an alignment treatment has been performed can be considered.
No .: UV irradiation with polarized light, rubbing treatment, or SiO
There is proposed a method of aligning and fixing a liquid crystalline monomer on an alignment film obtained by obliquely vapor-depositing, however, since an alignment treatment layer is provided, the process is complicated and a large area optical axis is inclined. The production cost of the retardation film increases.

[0003]

SUMMARY OF THE INVENTION The retardation of a retardation film produced by stretching orientation of a polymer film not only reduces the optical compensation effect at high temperature but also causes the optical axis to be oriented because molecules are oriented in the stretching direction. It is extremely difficult to tilt. On the other hand, in the method of arranging a liquid crystalline polymer or a liquid crystalline compound on an alignment-treated substrate, it is possible to produce a retardation film in which the optical axis is inclined, but the process is complicated and low cost. However, it is not possible to obtain a retardation film having a large-area optical axis inclined.

[0004]

According to the present invention, a simple process of exposing a film of a mixture of a photosensitive polymer and a low-molecular compound to provide a large wavelength dispersion, a temperature compensation effect, and an arbitrary optical axis direction. The developed retardation film is provided. Method for producing retardation film of the present invention (retardation film)
Then, a mixture of a photosensitive polymer and a low molecular compound is formed into a film, and by exposing the film, the molecules in the film can be oriented. In addition, large wavelength dispersion and temperature dependence of birefringence can be achieved. Can be granted. When this irradiation is performed in an oblique direction with respect to the film surface, the optical axis can be arbitrarily inclined for orientation, so that a large wavelength dispersion, a temperature compensation effect, and a phase difference in which the optical axis is set in a desired direction can be obtained. A film is made.

[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 group) 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. Since a material containing a mesogen component such as biphenyl has large wavelength dispersion of transmitted light, a film in which the material is oriented can be a retardation film effective for optical compensation. 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 (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 FIGS. In the coating film 20, side chains having a high photosensitivity arrangement having photosensitive groups 2a and 2b represented by oblong ellipses and having a direction corresponding to a vibration direction m of the irradiation polarized ultraviolet light L and a direction perpendicular to the irradiation light traveling direction. 2a
And the low-molecular compound 2c represented by a column and the side chain 2b having a poor photosensitivity coexist randomly. 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 with light having a wavelength at which the photosensitive group can react is required. Although this wavelength varies depending on the type of the photosensitive group, it is generally 20 nm.
It is 0-500 nm, and especially, the effectiveness of 250-400 nm is high in many cases.

FIG. 3 shows the film 30 after irradiating the film of FIG. 2 with light and allowing the reaction to proceed. Due to molecular motion after polarized light exposure,
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. That is, the polymer side chain 3b and the low molecular weight compound 3c, which did not cause photoreaction, were not oriented perpendicular to both the polarization electric field oscillation direction and the irradiation light traveling direction, and the photoreacted side chain 3a ( Reorient in the same direction as in 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 the electric field oscillation of the irradiated linearly polarized light and in the direction perpendicular to the direction of the irradiation light, birefringence is induced, and the wavelength dispersion is reduced. The resulting film has a large retardation.
The direction is 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 preferentially. Because of the molecular motion after exposure, the polymer was arranged in a direction parallel to the direction of irradiation light, 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, Ja
panese Journal Applied Ph
ysics, Vol. 19, 2013 (1980), a crystal rotation method for measuring the transmission intensity of polarized light while rotating a measurement sample was used. In this measuring method, the stereoscopic birefringence of the 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. After the exposure, the film is heated and the unreacted side chains and the low molecular weight compound are oriented or the film exposed and oriented under heating is cooled to the softening point temperature of the polymer or less, whereby the molecule is oriented. A film that has been re-exposed after further alignment by molecular motion and has further promoted crosslinking has reversible birefringence temperature dependence. This is because although the relaxation of the molecular orientation in the film is promoted by heat, the orientation occurs along the side chains or molecules fixed in the film by crosslinking during cooling. In a liquid crystal cell of an STN-type liquid crystal display device, when a film having the temperature dependence of birefringence is used, it is possible to follow the relaxation of the orientation of liquid crystal molecules caused by a rise in temperature and to suppress a decrease in display characteristics such as color shift. . Further, in the retardation film of the present invention, the temperature dependence of birefringence can be controlled by changing the type of polymer or low molecular weight compound and the thermal characteristics, and temperature compensation can be performed in various liquid crystal materials. When the low-molecular compound to be mixed in the present invention has heat and / or photoreactivity with each other or with the high-molecular compound, the orientation is firmly fixed and the heat resistance is improved. Can be expected.
In such a case, it is necessary to control the density of the photoreaction points by suppressing the exposure dose or adjusting the reactivity so as not to hinder the molecular motion during the alignment after the exposure.

The low molecular weight compound has an effect of suppressing the haze when it is in an appropriate amount, but increases the haze when added in excess,
This causes a decrease in orientation. From such a viewpoint, although depending 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, if the compatibility between the polymer and the low molecular weight compound is not sufficient, fine crystals large enough to phase separate or scatter visible light are generated by heating the substrate during film formation or after exposure. It causes an increase in cloudiness.

As a technique for increasing the film thickness and obtaining a larger phase difference, there is a method of laminating films. In this case, a material solution is applied and laminated on the film that has been formed and exposed,
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. By exposing a film of a mixture of a photosensitive polymer and a low-molecular compound from the front and back surfaces, birefringence can be more efficiently developed. In this case, a mixture of a photosensitive polymer and a low-molecular compound is formed into a film by coating on a support 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 a property of transmitting light having 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 mixture may be exposed from the front and back surfaces of the film.

A method for synthesizing the starting compound of the photosensitive side-chain type liquid crystalline polymer used in the examples of the present invention 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 Monomer 1 shown in Chemical Formula 1.

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(Polymer 1) Polymer 1 was obtained by dissolving this monomer 1 in tetrahydrofuran, adding AIBN (azobisisobutyronitrile) as a reaction initiator and polymerizing. This polymer 1 exhibited liquid crystallinity in a temperature range of 47 to 75 ° C.

(Polymer 2) This monomer 1 and stearyl methacrylate are dissolved in tetrahydrofuran at a molar ratio of 0.85: 0.15, and AIBN is used as a reaction initiator.
Was added and polymerized to obtain a polymer 2. This polymer 2 also exhibited liquid crystallinity.

(Low molecular weight compound 1) 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 1 represented by Chemical Formula 2.

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(Low molecular weight compound 2) 4,4'-biphenyldiol and 1,6-dibromohexane were reacted under alkaline conditions to synthesize 4,4'-bis (6-bromohexyloxy) biphenyl. Next, a low molecular compound 2 represented by Chemical Formula 3 was synthesized by reacting lithium methacrylate and purifying the product by a column.

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(Low molecular weight compound 3) 4,4'-biphenyldiol is reacted with 1,6-dibromodecane under alkaline conditions to give 4,4'-bis (6-bromodecanyl)
Biphenyl was synthesized. Next, a low molecular compound 3 represented by Chemical Formula 4 was synthesized by reacting lithium methacrylate and purifying the product with a column.

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[0015]

FIG. 1 shows an example of a production method (apparatus) when a retardation film of the present invention is produced by exposing a 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).
A film 14 of a mixture of a photosensitive polymer and a low molecular compound applied (coated) on a substrate 15 is irradiated.

(Example 1) 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 1 were dissolved in dichloroethane and applied on a quartz substrate to a thickness of about 3 μm. The substrate was tilted at 45 degrees with respect to the horizontal plane, the coated surface was arranged as an irradiation surface, and ultraviolet light converted into linearly polarized light using a Glan-Taylor prism was irradiated at room temperature from a direction perpendicular to the horizontal plane at 200 mJ / cm ^2. Subsequently, the substrate was turned upside down and the ultraviolet light converted to linearly polarized light was turned to 200 mJ / cm ^2.
Irradiated. Next, 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, and the phase difference in the substrate plane is 10 °.
The thickness was 4 nm, and there was almost no haze, which was sufficient for practical use. When the in-plane retardation at _{t ° C.} is R _{t ° C.} , R _{60 °} C./R _{30 ° C.} = 0.88, R _{80 °} C./R
_{30 ° C.} = 0.29, R _{100 °} C./R _{30 ° C.} = 0.08,
R _{120 °} C./R _{30 ° C.} = 0.06, and the temperature dependence of the phase difference was confirmed. FIG. 4 shows the birefringence temperature dependence of the first embodiment. Further, the ratio of the phase difference measured at a wavelength of _{400 nm} to the phase difference measured at a wavelength of 550 _nm (R _{400 nm}
/ R _{550 nm} ) is R _{400 nm} / R _{550 nm} =
1.23, indicating that the film had a large wavelength dispersion.

Example 2 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 2 were dissolved in dichloroethane and applied on a quartz substrate to a thickness of about 3 μm. The substrate was tilted at 45 degrees with respect to the horizontal plane, the coated surface was arranged as an irradiation surface, and ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was irradiated at 120 mJ / cm ² at room temperature from a direction perpendicular to the horizontal plane. Subsequently, the substrate was turned upside down and the ultraviolet light converted to linearly polarized light was turned to 120 mJ / cm ^2.
Irradiated. Next, 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, and the phase difference in the substrate plane is 23 °.
It was 8 nm. Also, R _{60 °} C./R _{30 ° C.} = 0.9
_{9, R 80 ℃ / R 30} ℃ = 0.91, R 100 ℃ / R
_{30 ° C.} = 0.74, R _{120 °} C./R _{30 ° C.} = 0.44, and the temperature dependence of the phase difference was confirmed. Further, R
_{400 nm} / R _{550 nm} = 1.25.

Example 3 3.75% by weight of polymer 1 and 1.25% by weight of low molecular weight compound 3 were dissolved in dichloroethane and applied on a quartz substrate to a thickness of about 3 μm. The substrate was tilted at 45 degrees with respect to the horizontal plane, the coated surface was arranged as an irradiation surface, and ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was irradiated at 120 mJ / cm ² at room temperature from a direction perpendicular to the horizontal plane. Subsequently, the substrate was turned upside down and the ultraviolet light converted to linearly polarized light was turned to 120 mJ / cm ^2.
Irradiated. Next, 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, and the phase difference in the substrate plane is 65 °.
nm. R _{60 °} C./R _{30 ° C.} = 0.95;
_{R80 ° C} / R30 _{° C} = 0.48, R100 _{° C} / R30 _{° C}
= 0.40, R120 _{° C} / R30 _{° C} = 0.30, and the temperature dependence of the phase difference was confirmed. Further, R _{400 nm} /
_R550nm = 1.24.

Example 4 3.75% by weight of polymer 2 and 1.25% by weight of low molecular weight compound 1 were dissolved in dichloroethane and applied on a quartz substrate to a thickness of about 3 μm. The substrate was tilted at 45 degrees with respect to the horizontal plane, the coated surface was arranged as an irradiation surface, and ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was irradiated at 120 mJ / cm ² at room temperature from a direction perpendicular to the horizontal plane. Subsequently, the substrate was turned upside down and the ultraviolet light converted to linearly polarized light was turned to 120 mJ / cm ^2.
Irradiated. Next, 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, and the phase difference in the substrate plane is 10 °.
The thickness was 4 nm, and there was almost no haze, which was sufficient for practical use. Also, R _{60 °} C./R _{30 ° C.} = 0.23, R
_{80 ° C} / R30 _{° C} = 0.02, R100 _{° C} / R30 _{° C} =
0.0, R _{120 °} C./R _{30 ° C.} = 0.0, confirming the temperature dependence of the phase difference. Further, R _{400 nm} / R
_{550 nm} = 1.24.

Example 5 3.75% by weight of polymer 1 and 1.25% by weight of liquid crystal material E7 (Merck Japan)
Was dissolved in dichloroethane and applied on a quartz substrate to a thickness of about 3 μm. The substrate was tilted at 45 degrees with respect to the horizontal plane, the coated surface was arranged as an irradiation surface, and ultraviolet light converted to linearly polarized light using a Glan-Taylor prism was irradiated at 120 mJ / cm ² at room temperature from a direction perpendicular to the horizontal plane. Subsequently, the substrate is turned upside down and the ultraviolet light converted to linearly
Irradiation was performed at 20 mJ / cm ² . Next, after heating to 100 ° C., it was cooled to room temperature. The optical axis of the substrate thus obtained was inclined by 67 ° from the normal direction of the substrate, and the phase difference in the substrate plane was 152 nm. In addition, R _{60 ° C} /
R _{30 ° C.} = 0.99, R _{80 °} C./R _{30 ° C.} = 0.94,
R _{100 °} C./R _{30 ° C.} = 0.92, R _{120 °} C./R
_{30 ° C.} = 0.82, and the temperature dependence of the phase difference was confirmed. Further, R _{400 nm} / R _{550 nm} = 1.24.

From these examples, it was proved that a phase difference exhibiting a large wavelength dispersion and a temperature compensation effect was obtained by exposure, and that a film having a controlled optical axis direction could be produced.

[0022]

According to the present invention, a photosensitive compound is formed into a film, and the molecules in the film can be oriented by a simple operation of exposure, and at the same time, a large wavelength dispersion and a temperature dependency of birefringence are imparted to transmitted light. can do. According to the present method, a retardation film can be obtained without using a conventional technique such as a stretching step, and the optical axis can be inclined by exposing the film from an oblique direction. Also, by changing the irradiation direction of the ultraviolet light, within the same substrate,
It is also possible to produce regions having different optical axes. A 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 retardation film having an inclined optical axis could not be produced at a low cost in a large area. However, according to the present invention, a simple operation of exposing the light has a large wavelength dispersion property for transmitted light. This has made it possible to produce a film having an optical axis direction controlled and a temperature compensation effect.

[0023]

[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 view of side chains arranged by molecular motion after polarized light exposure.

FIG. 4 shows the temperature dependence of the phase difference in the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ultraviolet lamp 12 ... Power supply 13 ... Optical element (Gran Taylor prism) 14 ... Film (film) 15 ... Substrate 16 ... Disordered light 17 ... Linear polarization UV light

Claims (5)

[Claims] 1. A mixture of a photosensitive polymer and a low molecular weight compound
When it is made in a process including the operation of irradiating the film with light
In both cases, the phase difference at 30 ° C with respect to the average wavelength region of visible light
And the ratio of the phase difference at 80 ° C (R_{80 ℃}/ R_{30 ° C})But
0.01 <R _{80 ℃}/ R_{30 ° C}<0.97, 400n
phase difference measured at a wavelength of m and a wavelength of 550 nm
Phase difference ratio (R_400nm/ R_{550 nm}) Is 1.1
5 <R _400nm/ R_{550 nm}It is Crystallo
The inclination (θ) of the optical axis measured by the partitioning method is 0 ° ≦
a retardation film characterized by θ <90 ° and
And its manufacturing method. 2. The retardation film according to claim 1, wherein the film is produced by a process including an operation of irradiating a film of a mixture of a photosensitive polymer and a low-molecular compound with light from both front and back sides. Production method. 3. A process comprising irradiating a film of a mixture of a photosensitive polymer and a low-molecular compound formed on a support with light from both directions of a front surface and a back surface via the support and the support. The retardation film according to claim 1 and a method for producing the same. 4. A retardation film according to claim 1, wherein the light applied is linearly polarized light or partially polarized light, and a method for producing the same. 5. The retardation film according to claim 1, 2, 3, or 4, and a method for producing the retardation film, comprising a step of heating and / or cooling. And its manufacturing method.