JPH11231133A - Optical film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film capable of easily setting plural optical characteristics in the same plane. and a manufacturing method. SOLUTION: The laser light from light source 2c is made parallel by a collimator lens 8 and made incident on a polarized light rotating element 9. The light passed through the polarized light rotating element 9 has angle of polarization varied according to the voltage supplied to the polarized light rotating element 9. The light having passed through the polarized light rotating element 9 is made incident on an objective 10. The objective 10 converges recording light to irradiate an optical film 1. The optical film 1 consists of a substrate 12 and a photorecording layer 13. This photorecording layer 13 is irradiated with the light varied in the angle of polarization by the polarized light rotating element 9 and then given optically induced birefringence, so that desired optical characteristics are recorded on the photorecording layer 13 of the optical film 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film used for an optical element and a method for producing the same.

[0002]

2. Description of the Related Art Optical films of this kind are, for example, liquid crystal display element compensators, viewing angle improving plates for liquid crystal display elements, optical retardation plates, optical rotators, .lambda. / 4 This is used for optical elements such as a plate and a λ / 2 plate. In general, a retardation plate refers to a birefringent plate (crystal plate) that gives a predetermined optical path difference (accordingly, a phase difference) between linearly polarized lights oscillating in directions perpendicular to each other when passing through the plate. The thickness of the birefringent plate is d, the refractive index of linearly polarized light vibrating in the direction of the electric principal axis perpendicular to each other is n1,
Assuming that n2, the optical path difference is given by | n1−n2 | d. Those whose values are λ / 4, λ / 2, and λ / 1 (where λ is the wavelength of the light used in vacuum) are called quarter-wave, half-wave, and single-wavelength plates, respectively, which are π / It corresponds to a retardation plate of 2, π, 2π. For example, a quarter-wave plate is a birefringent plate whose thickness is determined so as to generate a quarter-wavelength optical path difference between linearly polarized lights vibrating in directions perpendicular to each other. As the material, a thin plate obtained by cleaving muscovite to an appropriate thickness, a synthetic resin plate having one molecule oriented in one direction, or the like is used. When linearly polarized light having an azimuth of 45 ° with respect to the principal axis direction enters this plate, the transmitted light becomes circularly polarized.

The quarter-wave plate has various uses, and has recently been used for a polarization control element of a flat panel display such as a liquid crystal display. Liquid crystal displays occupy a significant position in the display field because of their features such as low voltage operation, light weight, and low cost. Above all, S
The TN liquid crystal display can display a large screen by a multiplex drive dot matrix system, and has advantages such as a higher contrast and a wider viewing angle than a conventional twisted nematic (TN) liquid crystal display. For this reason, STN liquid crystal displays are widely used in the field of liquid crystal displays requiring a large screen display, such as personal computers and word processors.

However, the STN method cannot display in black and white mode due to its principle, and changes from green to yellow-red mode when no electric field is applied, and changes to blue colorless mode when an electric field is applied. The display in this coloring mode is not only unfavorable to the user, but also has a serious disadvantage that it cannot cope with colorization well. In order to convert the coloring mode to the black-and-white mode, in principle, the light that has passed through the liquid crystal cell and has become elliptically polarized light may be returned to the original linearly polarized light using a retardation plate.

[0005] However, as the conventional retardation plate, a thin plate obtained by cleaving muscovite to an appropriate thickness, a synthetic resin plate in which molecules are oriented in one direction, and the like have been used. It is difficult to manufacture such a retardation plate having a large area, and there is a problem that it cannot be incorporated in a large flat panel.

As a method for solving this problem, a retardation plate produced by uniaxially stretching a thermoplastic resin such as polycarbonate is used. This retardation plate has a simple manufacturing method and is excellent in mass productivity. However, the rate of change of the refractive index change (Δn) due to heat is large, and it is impossible to correct the initial retardation when used for a long time. There is a problem that the contrast of the panel is reduced.

Instead of this, a method has been proposed in which a polymer liquid crystal is formed in a film shape and used as a large-area, thin-film retardation plate. Polymer liquid crystals have optical anisotropy and can take various molecular orientation forms as compared with general polymers. Therefore, the polymer film obtained by fixing these orientation forms,
It is known that it can be used for various optical elements.

A retardation plate using a polymer liquid crystal is disclosed in, for example, JP-A-3-87720 and JP-A-4-22917. The polymer films used for these retardation plates have the same optical performance over the entire surface of the optical element, but in the production of polymer liquid crystals having multiple optical characteristics in the same plane, protection is required. A complicated process of providing a layer and using a resist or the like and an advanced printing technique are required. In addition, it is difficult with this type of technology to control the optical characteristics satisfactorily for each fine region.

[0009]

A method for solving these problems has been proposed in, for example, Japanese Patent Application Laid-Open No. 8-292432. The method described in the publication uses a liquid crystalline polymer film whose alignment state changes by light irradiation as a retardation plate, and a plurality of optical performances can be obtained in the same plane by locally performing light irradiation on this film. Thus, an optical film is produced. However, since this alignment principle changes the chirality of the liquid crystalline polymer by light irradiation, it is very difficult to control the twist angle accurately, and when exposed to sunlight or the like, the alignment is individually controlled. There is also a problem that the orientation state of the phase difference plate is disturbed.

Accordingly, an object of the present invention is to provide an optical film capable of easily setting a plurality of optical characteristics in the same plane, and a method for manufacturing the same.

[0011]

The above object is achieved by an optical film including at least one optical recording layer, wherein the optical recording material having photoinduced birefringence functions as a quarter-wave plate. Is done. Here, the thickness d of the optical recording layer
Is Δn · d = (m + 1) where Δn is a refractive index change induced by light, λ is a wavelength of irradiation light, and m is an integer of 1 or more.
/ 4) · λ is formed. As the refractive index change Δn, it is preferable to use a saturated refractive index change value that saturates at a certain light irradiation amount or more.

An optical recording material used for an optical film includes:
A polymer compound or a polymer liquid crystal having a photoisomerizable group in the side chain. This polymer compound or polymer liquid crystal is
For example, at least one monomer polymer selected from the group of polyesters can be used. The optical recording material may be a polymer material in which molecules that undergo photoisomerization are dispersed. Here, the photoisomerizable group or molecule has an azobenzene skeleton.

In the production of the optical film according to the present invention, linearly polarized light is incident on a polarization rotation element, the polarization angle of the light is controlled to be rotated by the polarization rotation element, and the light whose polarization angle is controlled to be rotated is photoinduced. Irradiation is performed on an optical recording layer made of an optical recording material having a refractive property, and a 波長 wavelength plate having an orientation corresponding to the polarization angle of light is recorded on the optical recording layer. in this case,
In the second and subsequent recordings of the polarization angle of light, rewriting can be performed without erasing the previous recording state.

Further, the apparatus for producing an optical film according to the present invention comprises a light source that emits coherent light, a polarization rotation element that rotationally controls the polarization angle of the light from the light source, and a light whose polarization angle is rotationally controlled by the optical film. And an imaging optical system for irradiation. Here, the polarization rotator controls the rotation of the polarization angle of the light according to the voltage value supplied thereto. Note that the present apparatus is provided with a mechanism for moving the image forming position of light applied to the optical film.

As described above, in the present invention, the azimuth of the wave plate is rotated by rotating the azimuth (polarization angle) of the plane of polarization of the irradiation light. Therefore, by changing the polarization angle of the irradiation light, the twist angle of the polarization can be set freely. That is, it is possible to easily set a plurality of optical characteristics in the same plane. This makes it possible to produce an optical film that can compensate for variations in optical characteristics in the same plane and compensate for changes in optical characteristics due to aging.

The torsion angle and phase information recorded in the plane of the retardation plate can be rewritten any number of times. The characteristics can be updated at any time, and the optimum display state can always be maintained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an optical film and a method of manufacturing the same according to the present invention, the principle of a retardation plate will be described.

First, a method for rotating the polarization angle of linearly polarized light at an arbitrary angle will be described. Since light is a type of electromagnetic wave, it can be represented by Maxwell's equation. If the z axis (the traveling direction of light) is fixed, the electric field vector E of light can be expressed by the following (Equation 1).

[0019]

(Equation 1)

Here, φ _x and φ _y represent initial phases with respect to the x-axis and the y-axis, respectively. The tip of the electric field vector E depict various trajectories by the value of the phase difference between the x-axis and y-axis (φ _x -φ _y). FIG. 1 schematically illustrates this, and illustrates the polarization state of light when the phase difference φ _x −φ _y between the x-axis and the y-axis changes. As shown in FIG. 1, the circularly polarized light when the phase difference _{(φ x -φ y) = π} / 2 = 3π / 2. This is a so-called quarter-wave plate. In this element, the optical path difference Δ between the fast axis and the slow axis is set to the following (Equation 2).

[0021]

Δ = (m + ／) * λ (Expression 2)

Here, m is a positive number and λ is a wavelength. Therefore, when light passes through this element, the phase difference (φ _x −φ _y )
Causes a change of π / 2. When such a phase difference change occurs, incident light changes as follows. If the incident light is linearly polarized light as shown in FIG.
The transmitted light is circularly polarized light as shown in FIG. If the incident light is circularly polarized light as shown in FIG. 1C, the transmitted light is linearly polarized light as shown in FIG.

At this time, if the polarization angle is rotated while satisfying the condition of (Equation 2), the linearly polarized light in the above case rotates. That is, the twist angle of the polarized light can be changed. For example, when this is used as a compensator for STN liquid crystal, if the polarization angles are adjusted so as to compensate for variations in the optical rotation characteristics of each pixel of the liquid crystal display so that all the polarization axes of the transmitted light are aligned, a uniform display can be obtained. can get.

Next, an optical recording material exhibiting the above-described effect of the quarter wavelength plate will be described. As such a recording material, any material may be used as long as it exhibits light-induced birefringence and the birefringence is recorded and held. Here, the light-induced birefringence means that anisotropic medium is irradiated with light to cause anisotropy of refractive index (birefringence). As an example of a material exhibiting such photoinduced birefringence, there is a polymer compound or a polymer liquid crystal having a photoisomerizable group in a side chain, or a polymer material in which molecules to be photoisomerized are dispersed. This material is macroscopically isotropic, but irradiation with linearly polarized light induces photoisomerization, which results in anisotropy in the refractive index.

As the group or molecule to be photoisomerized, those exhibiting large birefringence by isomerization are desired.
Those containing an azobenzene skeleton are preferred. As a polymer compound or a polymer liquid crystal material having a photoisomerizable group or molecule, the induced anisotropy of the photoisomerizable group is transmitted to the polymer compound or the polymer liquid crystal, and as a result, the polymer compound or the polymer It is desired to produce a large birefringence in the entire molecular liquid crystal and record the birefringence. For example, a polymer compound or a polymer liquid crystal, which is at least one kind of monomer polymer selected from the polyester group, is used. Specifically, polymethyl methacrylate and polyvinyl alcohol are preferred. Hereinafter, azobenzene will be described as an example of the photoisomerizable group.

Azobenzene is transformed into trans-
3 shows photoisomerization of cis. Fig. 2
(A), and the molecular structure of the cis type is shown in FIG.
become that way.

Azobenzene alone shows anisotropy,
When randomly dispersed in the recording material as shown in FIG. 3A, the recording material as a whole exhibits isotropic properties. Also, in the recording material, there are many trans-types before the photoexcitation. On the other hand, the trans-form changes to the cis-form by photoexcitation, and many cis-forms are present in the material. In particular, when the material is irradiated with linearly polarized pump light having a certain polarization direction, only azobenzene, which is in the same direction as the polarization direction, absorbs light and changes to the cis-type as shown in FIG. In this case, the birefringence of azobenzene itself caused by isomerization of azobenzene and the birefringence of a polymer compound or polymer liquid crystal induced by isomerization of azobenzene are combined to change the polarization direction of pump light in the optical recording medium. Birefringence occurs as an axis. By utilizing the birefringence, the polymer film can function as the above-described wavelength plate.

For example, consider the case of using as a quarter wavelength plate. Let d be the thickness of the polymer film and Δ
If n, the optical path difference that occurs when light of wavelength λ passes through the polymer film is Δn · d. Therefore, if this becomes just λ / 4, the polymer film functions as a 波長 wavelength plate. That is, birefringence may be induced so as to satisfy the following condition (Equation 3).

[0029]

[Expression 3] Δn · d = λ / 4 (Expression 3)

Next, the optical characteristics of the material used in the present invention will be described. As a material of the retardation plate, a polyester having cyanoazobenzene in a side chain shown in FIG. 2C is used as a raw material, and this is dissolved in chloroform to prepare a solution. The solution is applied to a glass substrate and dried. Thickness 2
A μm film was obtained. The photo-induced refractive index change of the material in the retardation plate used this time was measured by the measurement system shown in FIG. FIG. 5 shows the measurement results.

As shown in FIG. 4, the light source 2b of the pump light 4 used to induce anisotropy in the optical recording material is a light source 2b which is sensitive to polyester having cyanoazobenzene in the side chain.
A 15 nm argon ion laser was used. The polarized light of the light emitted from the light source 2b is s-polarized light (perpendicular to the paper surface), and the laser light passes through the half-wave plate 6 and irradiates the optical film 1. The polarization angle of the pump light 4 was changed from the s-polarized light by 45 degrees by the half-wave plate 6. The birefringent direction induced by the pump light 4 is measured by the probe light 3 generated by a light source 2a different from the pump light. This light source 2a includes:
A 633 nm helium-neon laser having a wavelength that does not affect the anisotropy induced in the optical film 1 was used. This laser light was transmitted through the polarizer 5 to obtain s-polarized light (perpendicular to the paper). This light is applied to the optical film 1 and the transmitted light is guided to a polarizing beam splitter (PBS) 7. The polarization beam splitter 7 separates the transmitted s-polarized light component and p-polarized light component of the probe light 3.
By measuring each component with the optical power meters I1 and I2, the polarization direction of the probe light 3 transmitted through the optical film 1 can be checked. The refractive index change Δn is determined from the measured polarization angle.

In the measurement, the initialized optical film 1 is irradiated with pump light 4 to induce birefringence. The light intensity of the pump light 4 was 1 W / cm ² . At the same time, the probe light 3 was irradiated, and the polarization direction of the probe light 3 transmitted through the optical film 1 was measured at intervals of 15 seconds by the optical power meters I1 and I2.

FIG. 5 shows the result of the refractive index change Δn converted from the measured polarization direction of the probe light 3. Here, it was assumed that the light-induced dichroism Δα was negligible. The horizontal axis represents the pump light irradiation amount (product of intensity and time) E, and the vertical axis represents the magnitude of the refractive index change Δn obtained by measurement.
From this figure, it can be seen that the refractive index change Δn due to birefringence induced by the pump light 4 increases with time and saturates. The saturation refractive index change Δns obtained from this figure is about 0.033.

From the above results, polyester having cyanoazobenzene in the side chain can function as a retardation plate by inducing birefringence. It was also confirmed that the recorded light-induced birefringence was maintained for a long time at room temperature. Furthermore, by changing the polarization angle of the pump light 4 and recording the same in the same area, it is possible to overwrite and update the polarization information.

As described above, in order to use this optical recording material as a quarter-wave plate, it is necessary to satisfy (Equation 3). From the formula (3), it is understood that it is desirable that the thickness of the optical recording material and the refractive index change Δn are constant in order to produce a quarter-wave plate having stable characteristics. Therefore, in the optical recording medium of this embodiment, the refractive index change Δn is
Saturation refractive index change Δ that becomes a stable value above a certain light irradiation amount
ns. Thus, the thickness of the quarter-wave plate is determined from the value of the change Δns in the saturated refractive index and (Equation 3). If the retardation plate is manufactured with the thickness, a constant refractive index change Δns can be induced if the exposure amount is equal to or more than the light amount that gives the saturated refractive index change Δns. Phase difference compensation can be performed.

As the substrate used in the present invention,
Glass substrates such as plastic film substrates, alkali glass, borosilicate glass, printed glass, aluminum,
Examples include a metal foil substrate such as iron and copper, a glass substrate having an organic thin film such as a polyimide film and a polyvinyl alcohol film, a plastic film substrate, and a metal foil substrate. As the plastic film, for example, acrylic resin such as polymethyl methacrylate, polyvinyl alcohol, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyolefin, polyimide, polyamide imide, polyether imide, polyamide, polyether ketone, polyether ether ketone , Polyketone sulfide, polysulfone, polyphenylene oxide,
Examples thereof include polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyacetal, epoxy resin, and phenol resin.

As a method for forming a film of a polymer compound or a polymer liquid crystal, for example, solution coating, melt coating, or the like can be used. From the point of quality such as film thickness, a method of dissolving a polymer compound or a polymer liquid crystal in an appropriate solvent, applying the solution using a coating device, and drying to form a polymer compound or a polymer liquid crystal film is appropriate. is there.

When preparing the polymer compound or the polymer liquid crystal, the solvent which can be used depends on the kind of the polymer compound or the polymer liquid crystal to be used, but usually, chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, orthodiethylene is used. Halogenated hydrocarbons such as chlorobenzene, mixed solvents of halogenated hydrocarbons with phenols such as phenol and parachlorophenol, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone and the like are used.

As a coating method, a spin coating method, a screen printing method, an immersion pulling method, a roll coating method, a doctor blade method, a spray method, a wire bar method, or the like can be adopted. When performing the spin coating method,
Conditions such as the concentration of the solution and the number of spin rotations are appropriately set so that the thickness of the formed thin film causes a phase difference of λ / 4 in the visible light region.

Next, a method for imparting a desired polarization angle to the produced polymer compound or polymer liquid crystal film will be described. The light irradiated on the polymer compound or the polymer liquid crystal film is
For example, there is no particular limitation as long as light-induced birefringence can be generated, such as sunlight, ultraviolet light, laser light, light from a halogen lamp or a xenon lamp, but laser light is preferably used.

The light beam emitted from this light source enters the polarization rotation element. As the polarization rotating element, a λ / 2 plate, a liquid crystal valve, a Pockels element, a Faraday element, or the like can be used. The recording light passing through the polarization rotator irradiates a polymer compound or a polymer liquid crystal film. Thereby, as described above, the photoinduced birefringence can be recorded on the polymer compound or the polymer liquid crystal film. The method of partially irradiating light is not particularly limited, and a light beam narrowed down, such as laser light, may be used as it is, or may be condensed by an objective lens. Further, as a method of recording the polarization angles of a plurality of phase differences in the same plane,
There is no particular limitation as long as it has a drive system capable of precisely controlling the in-plane arrangement, and for example, a device such as a stepper can be used.

Next, a method of manufacturing the retardation plate of the present invention will be described. First, a polyester having cyanoazobenzene in a side chain as shown in FIG. 2 was used as a material causing photoisomerization. Also, barium borosilicate glass (Corning 7059) was used for the substrate. Here, assuming that a quarter-wave plate is manufactured according to the wavelength of 0.515 μm, the film thickness can be obtained from the following (Equation 4).

[0043]

D = λ / 4 / Δn (Equation 4)

Here, the change in the saturated refractive index Δns is used as Δn, and the thickness d is 3.9 since Δn = 0.033.
It was designed to be μm.

Polyester having cyanoazobenzene in the side chain was dissolved in chloroform to form a solution, which was applied on a glass substrate by spin coating. Then 7
The film was dried in an oven at 0 ° C. for 10 minutes to completely remove the chloroform and obtain a film. At this time, the conditions of the concentration of the solution and the number of revolutions of the spin coating are determined in advance so that the film thickness becomes the designed value. Further, when a desired film thickness cannot be obtained by one film forming process, a desired film thickness can be obtained by repeating the film forming process a plurality of times to form a multilayer.

The polymer film thus obtained is clouded as it is due to segregation of the polymer. Here, this polymer film is heated in an oven at a temperature higher than the phase transition temperature (about 100 ° C.) or higher for 10 minutes to make the polymer all in a random state. Thereafter, the polymer was immersed in ethanol at a temperature much lower than the phase transition temperature (0 ° C. or lower), and the polymer was rapidly cooled and solidified to obtain a glass-free transparent polymer film without segregation.

Next, a description will be given of a method of recording polarization information on the polymer film thus produced and producing an optical film functioning as a quarter-wave plate. FIG. 6A is a diagram illustrating an embodiment of an optical film manufacturing apparatus according to the present invention, and FIG. 6B is a diagram illustrating a structure of the optical film.
In the figure, a recording laser beam from a light source 2c is collimated by a collimator lens 8 and is incident on a polarization rotation element 9. Here, as the polarization rotating element 9, a λ / 2 plate,
A liquid crystal valve, a Pockels element, a Faraday element, and the like can be used. For example, when a liquid crystal valve is used as the polarization rotating element 9, the liquid crystal functions as a half-wave plate, and in a state where no voltage is applied, the polarization direction of the incident light and the axis of the half-wave plate are parallel. deep. Since the incident light is s-polarized, the transmitted light is s-polarized. On the other hand, when the maximum voltage is applied, the axis of the half-wave plate rotates 45 degrees,
The polarization of the incident light is rotated by 90 degrees. Further, at an intermediate voltage between the minimum voltage and the maximum voltage, the axis of the half-wave plate is increased up to 45 degrees according to the magnitude of the voltage. Thereby, the light passing through the polarization rotation element 9 can change the polarization angle from 0 degree to 90 degrees according to the voltage supplied to the polarization rotation element 9. Here, the polarization angle of the s-polarized light was set to 0 degree. The recording light having passed through the polarization rotator 9 enters the objective lens 10. The objective lens 10 condenses the recording light and irradiates the optical film 1 with it.

The optical film 1 comprises a substrate 12 and an optical recording layer 13 formed thereon, as shown in FIG. By irradiating the optical recording layer 13 with light, light-induced birefringence is imparted and the optical film 1 on which polarization information is recorded can be manufactured. At this time, by controlling the voltage applied to the polarization rotation element 9, the polarization angle θ of the recording light can be changed from 0 degree to 90 degrees.
As a result, as shown in FIG. 7, the azimuth of the minute quarter-wave plate produced by the birefringence induced by the recording light is set to θ (0 ≦ θ <9).
0) degrees. When this is used, for example, as a compensator for STN liquid crystal, different angles are set for each minute area, and the polarization angles are adjusted so as to compensate for variations in the optical rotation characteristics of each pixel of the liquid crystal display. If all axes are aligned, a uniform display can be obtained. Further, even if the refractive index change rate Δn may decrease over a long period of time due to the heat of the backlight of the liquid crystal display or the like, refresh can be performed any number of times by rewriting the same polarization information.

As described above, the twist angle of the polarized light can be freely set by changing the polarization angle of the irradiation light. This makes it possible to produce an optical film capable of correcting variations in optical characteristics in the same plane and compensating for changes in optical characteristics due to aging.

The torsion angle and the phase information recorded in the plane of the phase difference plate can be rewritten any number of times. Internal optical characteristics can be updated at any time,
An optimal display state can always be maintained.

Further, although the present embodiment has been described by taking a quarter retardation plate as an example, the wavelength of a liquid crystal display capable of displaying a wide viewing angle can be obtained by utilizing the polarization characteristics of a minute region in the same plane. In addition to being able to be used as a plate, it can also be applied to color display using optical rotation characteristics.

[0052]

According to the present invention, it is possible to obtain an optical film capable of easily setting a plurality of optical characteristics in the same plane and a method for manufacturing the same.

[Brief description of the drawings]

FIGS. 1A to 1I show a phase difference (φ _x −) between an x-axis and a y-axis.
FIG. 4 is a diagram schematically illustrating a polarization state of light when (φ _y ) changes.

2 (a) to 2 (c) are diagrams respectively showing the chemical structures of the trans structure and cis structure of azobenzene and the chemical structure of a polyester having cyanoazobenzene in a side chain.

FIG. 3 (a) is a diagram showing an isotropic state of azobenzene,
(B) is a diagram showing the appearance of light-induced anisotropy.

FIG. 4 is a diagram for explaining an optical system used for measuring a change in refractive index.

FIG. 5 is a diagram illustrating a saturation characteristic of a refractive index change.

FIG. 6A is a diagram illustrating an embodiment of an optical film manufacturing apparatus according to the present invention, and FIG. 6B is a diagram illustrating a structure of the optical film.

FIG. 7 is a diagram showing an optical film having a plurality of polarization angles in a minute region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical film 2a, 2b, 2c Light source 3 Probe light 4 Pump light 5 Polarizer 6 1/2 wavelength plate 7 Polarization beam splitter 8 Collimator lens 9 Polarization rotation element 10 Objective lens 11 Optical film production apparatus 12 Substrate 13 Optical recording layer

Claims (12)

[Claims] 1. An optical recording material having photo-induced birefringence is 1
At least one configured to function as a quarter wave plate
An optical film comprising an optical recording layer. 2. The thickness d of the optical recording layer is as follows: Δn · d = (m + 1) where Δn is a change in refractive index induced by light, λ is a wavelength of irradiation light, and m is an integer of 1 or more. The optical film according to claim 1, wherein the optical film is formed so as to satisfy (/ 4) · λ. 3. The optical film according to claim 2, wherein the refractive index change Δn is a saturated refractive index change value that saturates at a certain light irradiation amount or more. 4. The optical film according to claim 1, wherein the optical recording material is a polymer compound having a photoisomerizable group in a side chain or a polymer liquid crystal. 5. The polymer compound or the polymer liquid crystal,
The optical film according to claim 4, wherein the optical film is at least one monomer polymer selected from a polyester group. 6. The optical recording material according to claim 1, wherein the optical recording material is a polymer material in which molecules to be photoisomerized are dispersed.
4. The optical film according to any one of claims 1 to 3. 7. The photoisomerizable group or molecule contains an azobenzene skeleton.
Or the optical film of 6. 8. A linearly polarized light is made incident on a polarization rotating element, the rotation angle of the polarization angle of the light is controlled by a polarization rotation element, and the light whose rotation angle is controlled is an optical recording having photo-induced birefringence. A method for producing an optical film, comprising irradiating an optical recording layer made of a material and recording a quarter-wave plate having an orientation corresponding to the polarization angle of the light on the optical recording layer. 9. The method for producing an optical film according to claim 8, wherein when the polarization angle of light is recorded on the optical recording layer for the second time or later, rewriting is performed without erasing the previous recording state. . 10. A light source that emits coherent light, a polarization rotation element that rotationally controls the polarization angle of light emitted from the light source, and an imaging optical system that irradiates the optical film with the light whose polarization angle is rotationally controlled. An optical film manufacturing apparatus, comprising: 11. The apparatus for manufacturing an optical film according to claim 10, wherein the polarization rotation element controls rotation of the polarization angle of the light according to a voltage value supplied to the polarization rotation element. 12. The optical film manufacturing apparatus according to claim 10, further comprising a mechanism for moving an image forming position of light applied to the optical film.