JP2003139951A - Optically anisotropic thin film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optically anisotropic thin film which is light in weight and flexible by using fine particles of which the shape and size are controlled with a simple operation. SOLUTION: Rod shaped silver halide fine particles with an aspect ratio of >=2 or rod shaped metal fine particles with an aspect ratio of >=2 are oriented in a polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically anisotropic thin film that can be used in a light scattering type polarization selection element and an optical isolator, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A light scattering type polarization selection element is used for the purpose of improving the light utilization efficiency of a backlight of a liquid crystal display. The polarizing plate used in the conventional liquid crystal display transmits half polarized light and absorbs half polarized light. Therefore, the brightness of the light passing through the polarizing plate is less than half. In the transmissive liquid crystal display, since two polarizing plates are used on the front and back of the liquid crystal cell, the brightness is reduced to 30 to 40% of the light source. In a liquid crystal display, various attempts have been made to improve the light utilization efficiency.
For example, (a) Polarized beam splitter method (ASIA
DISPLAY'95, page 731), (b) cholesteric polarization conversion method (ASIA DISPLAY'95, page 735), and (c) liquid crystal / polymer composite (JP-A-6-
No. 208319).

(A) The method using a prism such as a polarized beam splitter has problems of angle dependence and wavelength dependence. Further, the prism also has a problem of impairing the features of the liquid crystal display, which are lightweight and compact. (B) In cholesteric polarization conversion, a cholesteric film in which the spiral pitch of cholesteric is uniformly distributed in the film thickness direction is used. The production of cholesteric film is very complicated and difficult. (C) In the composite of liquid crystal and polymer, the refractive index of the composite is limited by the liquid crystal material. Therefore, it is difficult to obtain large anisotropic scattering, and the polarization conversion efficiency has a small value.

In place of the above methods (a) to (c), a method of disposing an anisotropic scattering element having an aspect ratio of 1 or more in a dispersed arrangement has been proposed (described in JP-A-9-297204). Since this method uses an inorganic substance (titanium oxide, zirconium oxide, zinc oxide, silicon carbide, silicon nitride, silicon carbide, aluminum borate, glass) for the anisotropic scattering element, a large anisotropic scattering can be obtained. You can Furthermore, there is an advantage that there is little loss due to the angle dependence and the manufacturing can be easily performed without going through a complicated manufacturing process. In the method using the anisotropic scattering element, the shape of the anisotropic scattering particles is important. It is important that the anisotropic scattering particles scatter light in the major axis direction of the molecule and do not scatter light in the minor axis direction. That is, the smaller the width (minor axis) in the minor axis direction, the better. However, it is difficult to produce anisotropic scattering particles having a short axis width (short axis). JP-A-9-2972
The anisotropic scattering particles described in JP-A No. 04 have a width (minor axis) in the minor axis direction of 100 nm or more.

The infrared polarizing plate used in the ultra-small isolator used in optical communication using a semiconductor laser and an optical fiber has a problem in durability in the case of a conventionally known polymer obtained by stretching a dichroic dye. Had. To solve the problem of durability, Japanese Patent Publication No. 2-4061
No. 9 publication proposes a polarizing glass in which silver particles are dispersed. However, in the glass polarizing plate in the infrared region, since the acicular silver is oriented in the glass, there are problems of light weight and flexibility. As an anisotropic optical element other than the above, a structure derived from a fine alignment structure reported by Kikuta et al. (Proceedings of the Applied Physics, Autumn Meeting, Proceedings of the Lecture 26a-SP-22, p. 807 (1995)). There is a wide band 1/4 that makes use of the fact that strong dispersion appears in the effective refractive index of birefringence. This anisotropic optical element is achieved by orienting nanoscale-order anisotropic particles. In manufacturing an optically anisotropic element, it is very important to orient the anisotropic particles of nanoscale order. van der
Zande et al. Developed a monodisperse gold rod of uniform size by growing gold in a 12 nm diameter porous alumina film obtained by anodic oxidation by electrodeposition from a solution and peeling off the alumina substrate. Is being synthesized (J. Phy
S. Chem. B 101, 852 (1997)). However, in this method, the means for orienting the produced anisotropic scattering particles is unknown.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optically anisotropic thin film using fine particles whose shape and size can be controlled by a simple operation. Another object of the present invention is to provide an optically anisotropic thin film which is lightweight and flexible.

[0007]

Means for Solving the Problems The present invention includes the following (1)-
(6), (11) to (16) of the optically anisotropic thin film and the following (7) to (10), (17) and (18) are provided. (1) An optically anisotropic thin film in which rod-shaped silver halide grains having an aspect ratio of 2 or more or rod-shaped silver grains having an aspect ratio of 2 or more are oriented in a polymer.

(2) The optically anisotropic thin film as described in (1), wherein the silver halide grains or silver grains have a minor axis of 1 to 99 nm. (3) The short diameter of silver halide grains or silver grains is 1 to 5
The optically anisotropic thin film according to (2), which has a thickness of 0 nm. (4) The major axis of silver halide grains or silver grains is 4 to 9
The optically anisotropic thin film according to (1), which has a thickness of 00 nm. (5) The optically anisotropic thin film according to (1), wherein the silver halide grains or the silver grains have an aspect ratio of 3 to 1,000. (6) The optically anisotropic thin film according to (1), wherein the polymer is polyvinyl alcohol or modified polyvinyl alcohol.

(7) A step of applying a rod-shaped silver halide particle having an aspect ratio of 2 or more or a rod-shaped silver particle having an aspect ratio of 2 or more dispersed in an aqueous solution of a polymer on a support, a dispersion liquid Drying to form a thin film,
A method for producing an optically anisotropic thin film, which comprises a step of peeling a thin film from a support and a step of orienting silver halide grains or silver particles by stretching the thin film. (8) The production method according to (7), wherein the thin film is uniaxially stretched 1.5 to 20 times. (9) A step of applying a dispersion liquid in which rod-shaped silver halide grains having an aspect ratio of 2 or more are dispersed in an aqueous solution of a polymer on a support, a step of drying the dispersion liquid to form a thin film,
An optical method comprising the steps of peeling the thin film from the support, stretching the thin film to orient the silver halide grains, and reducing the silver halide grains to form rod-shaped silver grains having an aspect ratio of 2 or more. Method for producing anisotropic thin film. (10) A step of precipitating silver halide grains from a silver halide emulsion containing rod-shaped silver halide grains having an aspect ratio of 2 or more by centrifugation, a step of redispersing silver halide grains in water, a polyvinyl chloride in a redispersion liquid. Step of adding alcohol or denatured polyvinyl alcohol, step of removing remaining gelatin by enzyme, step of applying redispersion on support, step of drying redispersion to form thin film, peeling of thin film from support And the step of orienting the silver halide grains by stretching the thin film.

(11) An optically anisotropic thin film in which rod-shaped metal particles having an aspect ratio of 2 or more are oriented in a polymer. (12) The short diameter of the metal particles is 1 to 99 nm (1
The optically anisotropic thin film described in 1). (13) The short diameter of the metal particles is 1 to 50 nm (1
The optically anisotropic thin film described in 2). (14) The major axis of the metal particles is 4 to 900 nm (1
The optically anisotropic thin film described in 1). (15) The optically anisotropic thin film as described in (11), wherein the metal particles have an aspect ratio of 3 to 1,000. (16) The optically anisotropic thin film as described in (11), wherein the polymer is polyvinyl alcohol or modified polyvinyl alcohol.

(17) A step of applying a dispersion liquid in which rod-shaped metal particles having an aspect ratio of 2 or more are dispersed in an aqueous solution of a polymer on a support, a step of drying the dispersion liquid to form a thin film, A method for producing an optically anisotropic thin film, which comprises a step of peeling from a support and a step of orienting metal particles by stretching the thin film. (18) Uniaxially stretching the thin film 1.5 to 20 times (1
The production method according to 7). Aspect ratio of 2 in polymer
An optically anisotropic thin film in which the rod-shaped silver halide grains or the rod-shaped silver grains having an aspect ratio of 2 or more are oriented. In the present specification, the rod-shaped particles mean particles having an aspect ratio of 2 or more (ignoring the thickness) in the particle image of the electron microscope when the particles are observed with an electron microscope. In addition, the aspect ratio is the particle image obtained by observing with an electron microscope,
The rectangle with the smallest area is circumscribed, and the length of the long side of the rectangle (major axis of the particle) is the length of the short side (minor axis of the particle).
Divide by. In the present specification, the orientation of rod-shaped particles means that the direction of 70% (number) or more of rod-shaped particles (direction of major axis) is ± 20 degrees in the average direction of the entire rod-shaped particles (average direction of major axis). Means within. The orientation state of the fine particles can be confirmed by an electron micrograph of the thin film.
The measurement of the average direction is performed on 30 or more randomly selected fine particles.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION [Rod-shaped particles having an aspect ratio of 2 or more] The aspect ratio (ratio of major axis of particles / minor axis of particles) of rod-shaped particles is 2 or more, and preferably 3 or more. The upper limit of the aspect ratio is about 1000. The aspect ratio is more preferably 3 to 300, most preferably 4 to 80. The short diameter of the rod-shaped particles is preferably 1 nm to 99 μm, and 1
To 9900 nm, more preferably 1 to 9
90 nm is more preferable, and 1 to 99 nm is more preferable.
Is more preferable, and 1 to 50 nm is most preferable. The major axis of the rod-shaped particles is preferably 2 nm to 99 μm, more preferably 3 nm to 10 μm, even more preferably 4 nm to 2 μm, and 4 to 900 nm (less than micron order = nanometer order). Is more preferable and 4 to 600 nm (shorter than the wavelength of visible light) is most preferable.

[Rod-Shaped Silver Halide Grains] In the preparation of a silver halide emulsion, the rod-shaped silver halide grains coexist with a crystal form control agent for silver halide (eg, adenine, guanine, azaadenine, azaguanine, adenosine, guanosine). It can be formed by For crystal form control agent,
It is described in JP-A-63-271335. Typical silver halide compositions are silver bromide, silver iodobromide, and silver iodochlorobromide. Regarding the halogen distribution in the silver halide grain, it may have a uniform composition, or may have different halogen compositions inside and outside, and may have a layered structure (core / shell structure).

[Rod-Shaped Silver Particles] Rod-shaped silver particles can be formed by reducing the above-mentioned rod-shaped silver halide particles. The reduction of the rod-shaped silver halide grains, as described later, after producing an optically anisotropic thin film containing rod-shaped silver halide grains,
It is preferably carried out.

[Rod-shaped metal particles] Rod-shaped metal (including silver) particles can be formed by using the pores of the porous medium as a template. Specifically, the rod-shaped metal particles are obtained by depositing or filling a metal in the pores of the porous medium and then removing the medium. Regarding the method of using the pores of the porous medium as a template, the literature edited by JHFendler (Nanoparticles and Nanostructured Films Chapter.
10 “Template Synthesis of Nanoparticles in Nanopor
ous Membranes ”published by WILEY-VCH (1998)). As the porous medium, carbon nanotubes, zeolites, mesopore crystals, and anodized films of aluminum can be used.

The carbon nanotubes already satisfy the conditions close to those of a one-dimensional material in view of their size, and are expected to have electronic properties different from those of bulk graphite. Depending on the helical pitch of the cylinder, carbon nanotubes have both physical properties and semiconductor properties. It was predicted to have something. Carbon nanotubes are multi-walled carbon nanotubes (with a diameter of several tens nm in which a sheet of a cylindrical graphite structure with several tens of layers is nested).
And single-walled carbon nanotubes (a single layer of a cylindrical graphite structure having a diameter of about 1 nm).
The synthesis method includes an arc discharge method, a hydrocarbon catalytic decomposition method and a laser evaporation method. Recently, a hydrocarbon catalytic decomposition method has been developed that realizes mass production and direct growth of carbon nanotubes on a substrate. Ajayan et al. Have shown that it is possible to introduce molten oxides of PbO, Bi ₂ O ₃ , and V ₂ O ₅ into carbon nanotubes (Nature 375, p. 564 (1).
995)). Furthermore, Green et al., By introducing a molten molybdenum compound into carbon nanotubes,
Single crystal MoO ₃ nanowires were synthesized. further,
By reducing this with hydrogen, MoO ₂ nanowires, which are interested in electrical properties, are obtained. Rod-shaped metal particles can be produced in the same manner.

Regarding the zeolite and the mesopore crystal, Ichikawa et al. Have reported that the inner wall of the pores of the zeolite and the mesopore crystal (FMS-16) is a one-dimensional mesopore composed of a hydroxyl group, bridging oxygen, Al, Si, Na ions and the like. It was shown that it is possible to synthesize several nano-sized metal and alloy clusters by utilizing the property of having pores (2 to 10 nm) (J.Amer.Chem.So.
c., 118, 5810 (1996)).

Anodized aluminum coatings have long been known in the surface treatment field as "alumite" coatings. The anodic oxide film is a porous oxide film formed on the surface by anodizing aluminum in an acidic electrolytic solution. The anodic oxide film has a honeycomb structure in which orthogonal pores are formed in parallel at substantially equal intervals. In addition to this, the pore diameter, the pore interval, and the pore depth can be controlled relatively freely. Various metals can be deposited and filled in the pores of the anodized film by an electrochemical method. Then, the alumina layer is selectively dissolved and removed to produce the rod-shaped metal particles according to the present invention.

[Polymer] The polymer is preferably a ductile material. Further, the polymer is preferably hydrophilic, and more preferably water-soluble. The hydrophilic polymer has a hydrophilic group or a hydrophilic bond in its molecular structure (main chain or side chain). Examples of hydrophilic groups include carboxyl, hydroxyl, sulfo, amino, sulfonamide, sulfonimide, amide and alkylamino groups. Examples of hydrophilic bonds include urethane bonds, ether bonds, amide bonds and sulfonamide bonds. Hydrophilic groups are preferred, hydroxyl is more preferred, and alcoholic hydroxyl is most preferred. Any of natural hydrophilic polymers (eg, cellulose, starch), synthetic hydrophilic polymers (eg, polyvinyl alcohol, polyvinylpyrrolidone) and semi-synthetic hydrophilic polymers (eg, cellulose ester) can be used. In addition, the film formed of polymer (corresponding to the optically anisotropic thin film)
It is also preferable to use a polymer that can be stretched about 1.5 to 20 times (extends well).

In view of the above, polyvinyl alcohol and modified polyvinyl alcohol are the most preferred polymers. The saponification degree of polyvinyl alcohol is 100.
It does not have to be%. In other words, the polyvinyl alcohol can include unsaponified vinyl acetate repeat units in addition to the vinyl alcohol repeat units. However, considering the thermal stability of polyvinyl alcohol,
The saponification degree is preferably 70% or more, more preferably 80% or more. Further, the average degree of polymerization of polyvinyl alcohol is preferably 200 to 10000 on a mass average and 400 to 50 in consideration of the stretching treatment.
00 is more preferable.

Modified polyvinyl alcohol (copolymerized modified polyvinyl alcohol or post-modified polyvinyl alcohol) can also be used. The copolymer-modified polyvinyl alcohol is a polymer produced by saponifying a copolymer of vinyl acetate and another monomer (for example, ethylene, higher vinyl carboxylate, higher alkyl vinyl ether, methyl methacrylate, acrylamide). The post-modified polyvinyl alcohol is a compound having reactivity with a hydroxyl group of polyvinyl alcohol or a substituent thereof (eg, mercapto group of polyvinyl alcohol modified with mercapto group) (eg, acid chloride, aldehyde, acrylic acid derivative). It is a polymer produced by polymer reaction after the synthesis of polyvinyl alcohol. Further, mercapto- or sulfide-modified polyvinyl alcohol, which uses a chain transfer agent of a thiol derivative at the time of vinyl acetate polymerization, can also be used. The saponification degree and average degree of polymerization of the modified polyvinyl alcohol are the same as those of the polyvinyl alcohol. Other polymers may be used in combination with polyvinyl alcohol or modified polyvinyl alcohol. When used in combination, the content of polyvinyl alcohol or modified polyvinyl alcohol is preferably 50% by mass or more, more preferably 70% by mass or more, and most preferably 90% by mass or more based on the whole polymer.

[Production of Optically Anisotropic Thin Film] For the optically anisotropic thin film, rod-shaped particles are dispersed in a polymer solution (for example, an aqueous solution of polyvinyl alcohol or modified polyvinyl alcohol) to prepare a dispersion liquid. Coating on a support,
It can be produced by drying. The rod-shaped fine particles can be oriented by the shearing force of coating during coating.
However, the orientation of the rod-shaped fine particles can be increased by stretching the formed thin film. The stretching ratio of the thin film (1 before stretching) is preferably 1.5 to 20 times, and 2
It is more preferably 10 times.

The rod-shaped silver halide grains are generally prepared as a silver halide emulsion containing gelatin as a protective colloid. As described above, as the polymer of the optically anisotropic thin film, polyvinyl alcohol or modified polyvinyl alcohol is preferable to gelatin. Therefore, it is preferable to carry out a treatment of replacing gelatin with polyvinyl alcohol or modified polyvinyl alcohol as the polymer. Gelatin can be easily removed by a method of hydrolyzing gelatin using a protease. It is also preferable to precipitate the rod-shaped silver halide grains dispersed in the silver halide emulsion (aqueous gelatin solution) by centrifugation and, as a result, remove most of the gelatin. It is particularly preferable to use the centrifugation and the enzyme together.

Specifically, a step of precipitating rod-shaped silver halide grains dispersed in the silver halide emulsion by centrifugation, a step of redispersing the rod-shaped silver halide grains in water, a polyvinyl alcohol in the redispersion liquid Alternatively, a dispersion in which rod-shaped silver halide grains are dispersed in polyvinyl alcohol or a modified polyvinyl alcohol aqueous solution can be prepared by the steps of adding modified polyvinyl alcohol and dissolving it, and removing the remaining gelatin with an enzyme. If the amount of polyvinyl alcohol or modified polyvinyl alcohol added to the redispersion liquid is too large, rod-shaped silver halide grains tend to aggregate. Therefore, the addition amount of polyvinyl alcohol or modified polyvinyl alcohol is preferably 0.1% by mass to 10% by mass with respect to the redispersion liquid. Further, if the polyvinyl alcohol or modified polyvinyl alcohol to be added has a high average degree of polymerization, it tends to aggregate, so the average degree of polymerization is preferably 100 to 1000 on a mass average basis. When it is desired to increase the content of polyvinyl alcohol or modified polyvinyl alcohol or to use polyvinyl alcohol or modified polyvinyl alcohol having a high average degree of polymerization, after decomposing gelatin with an enzyme, increase the content or increase the average degree of polymerization. High polyvinyl alcohol or modified polyvinyl alcohol may be additionally added.

The produced optically anisotropic thin film is particularly useful as a light scattering type polarization selection element.

[0026]

[Example 1] (Preparation of gelatin dispersion of rod-shaped silver halide grains) 30 g of lime-processed gelatin was added to 1000 ml of distilled water, and 4
After dissolution at 0 ° C., 6.5 g of sodium chloride, 0.65 g of sodium hydroxide, 0.02 g of N, N-dimethylethylenethiourea and 0.27 g of adenine were added to bring the temperature to 65.
Raised to 0 ° C. 62.5 g of silver nitrate and 750 ml of distilled water
And a solution of 21.9 g of potassium bromide and 10.8 g of sodium chloride dissolved in 500 ml of distilled water were added to and mixed with the above solution over 40 minutes while maintaining the temperature at 65 ° C.
A silver halide emulsion (gelatin dispersion of rod-shaped silver halide grains) was obtained. When gelatin was removed from the silver halide emulsion by centrifugation and the silver halide grains were observed with an electron microscope, the aspect ratio was 10 to 33, the major axis was 0.3 to 1 μm, and the minor axis was approximately 30 nm. It was found to be rod-shaped silver halide.

(Preparation of polyvinyl alcohol aqueous solution in which rod-shaped silver halide grains are dispersed) To 5.0 g of the prepared silver halide emulsion, 50 ml of distilled water was added, and heated to 50 ° C. to dissolve gelatin. Next, centrifugation treatment was performed to precipitate rod-shaped silver halide grains and remove the supernatant. 20 ml of distilled water was added to the sediment and redispersed by ultrasonic waves. Polyvinyl alcohol having a saponification degree of 88% and a mass average polymerization degree of 300 (PVA-203, manufactured by Kuraray Co., Ltd.)
0.5 g was added and dissolved by stirring at room temperature for 1 hour. After that, 25 mg of proteolytic enzyme (Actinase E)
Was added and gelatin was decomposed by stirring for 6 hours to obtain a dispersion of rod-shaped silver halide grains. To this dispersion, 100 g of a 15 mass% aqueous solution of polyvinyl alcohol (PVA-224, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a mass average polymerization degree of 2400 was added, and stirred until it became uniform, thereby obtaining a rod shape An aqueous polyvinyl alcohol solution in which silver halide grains were stably dispersed was obtained.

(Preparation of Optically Anisotropic Thin Film Containing Rod-Shaped Silver Halide Grains) Coating Applicator (Coating Thickness: 500 μm)
m) on a polyethylene terephthalate support,
An aqueous polyvinyl alcohol solution in which rod-shaped silver halide grains were dispersed was applied and dried at 40 ° C. for 30 minutes. After peeling the polyvinyl alcohol thin film from the support, the temperature is 40 ° C,
The thin film was stretched up to 3 times in an atmosphere with a humidity of 60%. Then, the mixture was heated at 120 ° C. for 3 minutes to prepare an optically anisotropic thin film as a polyvinyl alcohol thin film in which rod-shaped silver halide grains were dispersed. When the optically anisotropic thin film was observed by an electron microscope, 80% or more of the rod-shaped particles were oriented within ± 10 of the average direction of the rod-shaped particles (corresponding to the stretching direction of the thin film).
It was within the range of °.

Example 2 (Preparation of an aqueous polyvinyl alcohol solution in which rod-shaped silver halide grains are dispersed) To 5.0 g of the silver halide emulsion prepared in Example 1, 50 ml of distilled water was added, and the mixture was heated to 50 ° C. and gelatinized. Was dissolved. Next, centrifugation treatment was performed to precipitate rod-shaped silver halide grains and remove the supernatant. 20 ml of distilled water was added to the sediment and redispersed by ultrasonic waves. Polyvinyl alcohol having a saponification degree of 88% and a mass average polymerization degree of 300 (PVA-203, manufactured by Kuraray Co., Ltd.)
0.5 g was added and dissolved by stirring at room temperature for 1 hour. After that, 25 mg of proteolytic enzyme (Actinase E)
Was added and gelatin was decomposed by stirring for 6 hours to obtain a dispersion of rod-shaped silver halide grains. 2% of polyvinyl alcohol (PVA-205, manufactured by Kuraray Co., Ltd.) having a saponification degree of 88% and a mass average polymerization degree of 500 was added to the dispersion.
By adding 120 g of 0 mass% aqueous solution and stirring until uniform, a polyvinyl alcohol aqueous solution in which rod-shaped silver halide grains were stably dispersed was obtained.

(Preparation of Optically Anisotropic Thin Film Containing Rod-Shaped Silver Halide Grains) Coating Applicator (Coating Thickness: 400 μm)
m) on a polyethylene terephthalate support,
An aqueous polyvinyl alcohol solution in which rod-shaped silver halide grains were dispersed was applied and dried at 40 ° C. for 30 minutes. After peeling the polyvinyl alcohol thin film from the support, the temperature is 40 ° C,
The thin film was stretched up to 3 times in an atmosphere with a humidity of 60%. Then, the mixture was heated at 120 ° C. for 3 minutes to prepare an optically anisotropic thin film as a polyvinyl alcohol thin film in which rod-shaped silver halide grains were dispersed. When the optically anisotropic thin film was observed by an electron microscope, 80% or more of the rod-shaped particles were oriented within ± 10 of the average direction of the rod-shaped particles (corresponding to the stretching direction of the thin film).
It was within the range of °.

(Evaluation as a polarization-selective optically anisotropic thin film) 1. Evaluation of light transmittance and light scattering (haze) The light transmittance and light scattering (haze) of the optically anisotropic thin films prepared in Examples 1 and 2 were measured by a haze meter (MODEL).
It was measured using 1001DP, manufactured by Nippon Denshoku Industries Co., Ltd. The measurement is performed by inserting a polarizer between the light source and the film, and the transmittances of all light rays are defined as those in which the transmission axis of the polarizer and the transmission axis of the polarization selection layer are the same, and those orthogonal are orthogonal. The transmittance was evaluated using the haze as an index for the light scattering property. When there is polarization selectivity, parallelism has higher transmittance than orthogonality,
Low haze.

2. Evaluation of planar shape The planar shape of the optically anisotropic thin films produced in Examples 1 and 2 is
The sample was sandwiched between two polarizing plates having transmittances orthogonal to each other, and observation was performed while rotating the direction of the sample between the polarizing plates.

The evaluation results are shown in Table 1. The transmittance of the optically anisotropic thin film produced in Example 1 (and 2 is 80 in parallel).
% And 30% or less in the orthogonal direction, showing high polarization selectivity. Therefore, the use of this optically anisotropic thin film in a liquid crystal display device can be expected to improve the utilization efficiency of large light.

[0034]

[Table 1] Table 1 ──────────────────────────────────── Optical anisotropic total light transmittance Haze thin film Parallel / Orthogonal Parallel / Orthogonal Planar evaluation ──────────────────────────────────── Example 1 82.8 28.5 9.3 38.1 Uniform, slightly bluish Example 2 80.5 28.0 9.5 38.0 Uniform, only slightly bluish ──────────── ─────────────────────────

[Example 3] (Preparation of optically anisotropic thin film containing rod-shaped silver particles) The optically anisotropic thin film containing rod-shaped silver halide grains prepared in Example 1 was immersed in boric acid water and then washed with water. . Next, apply a thin film to the film developer (Micro Fine (Fuji Photo Film Co., Ltd.)
(Manufactured by K.K.) for 1 hour. Then, by washing with water and drying, an optically anisotropic thin film was prepared as a polyvinyl alcohol thin film in which rod-shaped silver particles were oriented. When the optically anisotropic thin film was observed with an electron microscope, 80% or more of the rod-shaped particles were in the range of ± 10 ° with respect to the average direction of all the rod-shaped particles (coincident with the stretching direction of the thin film).

(Evaluation as Infrared Polarizing Plate) The transmittance of the produced optically anisotropic thin film was measured with a measuring machine (MODEL MPC-3100, manufactured by Shimadzu Corporation). The measurement was performed by inserting a polarizer between the light source and the film, and the polarization plane and the rod-shaped silver particles having the same major axis were made parallel, and those orthogonal were made orthogonal. The results are shown in Table 2. As shown in Table 2, 750 nm-1
High polarization is obtained at a wavelength of 500 nm,
It can be seen that it is useful as an infrared polarizing plate.

[0037]

[Table 2]                                 Table 2 ──────────────────────────────────── Wavelength (nm) 500 750 1000 1250 1500 1500 1750 ──────────────────────────────────── Transmittance (parallel) 3% Less than 1% Less than 1% Less than 1% Less than 1% 17% Transmittance (orthogonal) 5% 80% 85% 87% 87% 88% ────────────────────────────────────

Example 4 (Filling of Gold into Nanopores of Anodized Film) An aluminum plate was anodized to form a porous anodized film.
Porous anodic oxide film is the thickness of 1.5 [mu] m, the pores are present 10 ¹⁴ Average 8 × per 1 m ^2, an inner diameter 12
was nm. The inner diameter could be adjusted by dissolving the aluminum oxide. A small amount of copper was previously deposited in order to accelerate the deposition of gold. Copper can be selectively dissolved, facilitating the process of stripping gold from the support. The length of the gold rod can be changed depending on the deposition time. By the above processing, the minor axis is 12 nm and the major axis is 2
Rod-shaped gold particles having a thickness of 40 nm and an aspect ratio of 20 were formed in the nanopores of the anodized film.

(Peeling of Rod-shaped Gold Particles)
The aluminum oxide film was dissolved by immersing it in a 1.25 M sodium hydroxide aqueous solution. The obtained particles were immersed in an etching solution prepared by diluting the following stock solution with water by 100 times for 30 minutes to dissolve the copper coating the surface of the rod-shaped gold particles to separate the rod-shaped gold particles.

[0040] ────────────────────────────────────   Etching stock solution composition ────────────────────────────────────   98 mass% sulfuric acid 25 ml   30 mass% hydrogen peroxide water 175 ml   A few drops of 85 mass% phosphoric acid aqueous solution   1 liter with distilled water ────────────────────────────────────

(Preparation of polyvinyl alcohol aqueous solution in which rod-shaped gold particles are dispersed) The rod-shaped gold particles were treated with polyvinyl alcohol (PVA-) having a saponification degree of 88% and a mass average polymerization degree of 500.
No. 205, manufactured by Kuraray Co., Ltd.) was added to a 20% by mass aqueous solution, and the mixture was stirred until it became uniform to obtain a polyvinyl alcohol aqueous solution in which rod-shaped gold particles were stably dispersed.

(Preparation of Optically Anisotropic Thin Film Containing Rod-Shaped Gold Particles) Using a coating applicator (coating thickness: 400 μm), an aqueous polyvinyl alcohol solution in which rod-shaped gold particles are dispersed is coated on a polyethylene terephthalate support. ,
It was dried at 40 ° C. for 30 minutes. After peeling the polyvinyl alcohol thin film from the support, the thin film was stretched up to 3 times in an atmosphere of a temperature of 40 ° C. and a humidity of 60%. Then 120 ° C
And was heated for 3 minutes to prepare an optically anisotropic thin film as a polyvinyl alcohol thin film in which rod-shaped gold particles were dispersed. When the optically anisotropic thin film was observed with an electron microscope, 80% or more of the rod-shaped particles were in the range of ± 10 ° with respect to the average direction of all the rod-shaped particles (coincident with the stretching direction of the thin film).

(Evaluation as Polarizing Plate) The transmittance of the produced optically anisotropic thin film was measured in the same manner as in Example 3. The results are shown in Table 3. As a result, it was confirmed that it has a large polarization characteristic in the wavelength range in which it was measured. In particular, in the region of 1150 nm to 1550 nm, a large polarization characteristic such that the transmittance in the parallel direction is less than 1% and the transmittance in the orthogonal direction is 50% or more is realized.

[0044]

[Table 3]                                 Table 3 ──────────────────────────────────── Wavelength (nm) 610 820 1150 1300 1550 ──────────────────────────────────── Transmittance (parallel) <1% <1% <1% <1% <1% Transmittance (orthogonal) 21% 32% 50% 63% 80% ────────────────────────────────────

[0045]

According to the present invention, an optically anisotropic thin film in which fine rod-shaped particles are stably oriented can be obtained. This optically anisotropic thin film is easy to produce, has excellent optical properties, and has an extremely high industrial utility value.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 C08L 29:04 C08L 29:04 A (72) Inventor Masahiro Asami Minami Ashigara, Kanagawa Prefecture community-acquired swamp 210 address Fuji photo film Co., Ltd. in the F-term (reference) 2H049 BA06 BA46 BB43 BC03 BC09 BC22 BC25 2H091 FA07X FA31X FB02 FB13 FC07 GA01 LA30 4F071 AA29 AA78 AB07 AB13 AD06 AF35 AH12 AH19 BA03 BB02 BC01 4F205 AA19 AC01 AD03 AH73 GA06 GB01 GC06 GF02 GF21 GF24 GN29 GW50

Claims (18)

[Claims] 1. An optically anisotropic thin film in which rod-shaped silver halide grains having an aspect ratio of 2 or more or rod-shaped silver particles having an aspect ratio of 2 or more are oriented in a polymer. 2. The optically anisotropic thin film according to claim 1, wherein the silver halide grains or silver grains have a minor axis of 1 to 99 nm. 3. The optically anisotropic thin film according to claim 2, wherein the silver halide grains or silver grains have a minor axis of 1 to 50 nm. 4. The optically anisotropic thin film according to claim 1, wherein the silver halide grains or silver grains have a major axis of 4 to 900 nm. 5. The optically anisotropic thin film according to claim 1, wherein the silver halide grains or the silver grains have an aspect ratio of 3 to 1,000. 6. The optically anisotropic thin film according to claim 1, wherein the polymer is polyvinyl alcohol or modified polyvinyl alcohol. 7. A polymer having an aspect ratio of 2 in an aqueous solution.
The step of applying the dispersion liquid in which the above rod-shaped silver halide particles or the rod-shaped silver particles having an aspect ratio of 2 or more are dispersed on a support, the step of drying the dispersion liquid to form a thin film, the thin film from the support A method for producing an optically anisotropic thin film, which comprises a step of peeling and a step of orienting silver halide grains or silver particles by stretching the thin film. 8. The manufacturing method according to claim 7, wherein the thin film is uniaxially stretched 1.5 to 20 times. 9. A polymer having an aspect ratio of 2 in an aqueous solution.
The step of applying the dispersion liquid in which the rod-shaped silver halide grains are dispersed onto a support, the step of drying the dispersion liquid to form a thin film, the step of peeling the thin film from the support, and the step of stretching the thin film to perform halogen A method for producing an optically anisotropic thin film, which comprises a step of orienting silver halide grains and a step of reducing silver halide grains to form rod-shaped silver grains having an aspect ratio of 2 or more. 10. A step of precipitating silver halide grains from a silver halide emulsion containing rod-shaped silver halide grains having an aspect ratio of 2 or more by centrifugation, a step of redispersing silver halide grains in water, and a redispersion liquid. Of polyvinyl alcohol or denatured polyvinyl alcohol to the solution, the step of removing the remaining gelatin with an enzyme, the step of applying the redispersion liquid on a support, the step of drying the redispersion liquid to form a thin film, the thin film support A method for producing an optically anisotropic thin film, which comprises a step of peeling from the film and a step of orienting the silver halide grains by stretching the thin film. 11. An optically anisotropic thin film in which rod-shaped metal particles having an aspect ratio of 2 or more are oriented in a polymer. 12. The optically anisotropic thin film according to claim 11, wherein the minor axis of the metal particles is 1 to 99 nm. 13. The optically anisotropic thin film according to claim 12, wherein the minor axis of the metal particles is 1 to 50 nm. 14. The optically anisotropic thin film according to claim 11, wherein the major axis of the metal particles is 4 to 900 nm. 15. The metal particles having an aspect ratio of 3 to 10
The optically anisotropic thin film according to claim 11, which is 00. 16. The optically anisotropic thin film according to claim 11, wherein the polymer is polyvinyl alcohol or modified polyvinyl alcohol. 17. A step of applying a dispersion liquid, in which rod-shaped metal particles having an aspect ratio of 2 or more are dispersed in an aqueous solution of a polymer, on a support, a step of drying the dispersion liquid to form a thin film, and supporting the thin film. A method for producing an optically anisotropic thin film, comprising a step of peeling from a body and a step of orienting metal particles by stretching the thin film. 18. The method according to claim 17, wherein the thin film is uniaxially stretched 1.5 to 20 times.