JP3465756B2 - Hologram forming method and hologram - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram forming method and a hologram, and more particularly to a volume phase hologram forming method and a hologram thereof.

[0002]

2. Description of the Related Art As a conventional method for forming a volume phase hologram, for example, as described in JP-A-5-188843, a binder polymer, a reactive monomer, a photopolymerization initiator and a sensitizing dye are used. There is a method of using the following photopolymer as a photosensitive material. As a binder polymer, for example, 1.0 g of poly-N-vinylcarbazole, as a reactive monomer, for example, 1.0 g of tribromophenoxyethyl acrylate, and as a photopolymerization initiator, for example, trichloro-s-triazine. 0.07g, 0.003 of squarylium dye
g, the above composition is dissolved in a solvent capable of dissolving, for example, 14.5 g of chlorobenzene, a film is formed on glass using an applicator, and dried to obtain a recording medium. A 5 wt% aqueous solution of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 500) was applied to the surface of the record carrier with a spin coater at (1st) 500 rpm for 5 seconds (2n).
d) Apply at 1000 rpm for 20 seconds and dry.

After that, the 64 krypton ion laser was used.
Exposure energy of 30 mJ / with light of 7.1 nm wavelength
The hologram is exposed to be cm ² . After exposure,
The polyvinyl alcohol film on the surface of the record carrier is removed, and the unpolymerized reactive monomer is eluted with a developing solution to perform a developing treatment.

[0004]

However, in the conventional hologram forming method using a photopolymer composed of such a binder polymer, a reactive monomer, a photopolymerization initiator and a sensitizing dye as a photosensitive material, a low refractive index portion is used. Micro voids are generated in the part where the reactive monomer of is eluted,
Since the diameter of the minute void is several hundreds nm, which is almost equal to the wavelength of light, there is a problem that scattering due to the void is large, and as a result, the haze value does not fall to 5% or less, resulting in cloudiness and turbidity. Japanese Patent Publication No. 4-77317).

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its object is to reduce the diffraction efficiency and the refractive index modulation of a hologram having a refractive index modulation depending on the presence or absence of a minute void. It is intended to provide a hologram forming method and a hologram which can reduce the cloudiness of the hologram without causing a shift in the diffraction wavelength.

[0006]

In order to solve the fog problem, the size of the air gap is made considerably smaller than the wavelength of light (not more than 1/10 of the wavelength of light) so that scattered components are not generated. ) Is required. If the size of the void in the traveling direction is made considerably smaller than the wavelength of light, the void does not serve as a scattering center and has only the effect of lowering the average refractive index. Therefore, the haze value, which is the object of the present invention, is 5%.
It can be made smaller as follows.

As a method for reducing the size of the minute voids, pressure is applied in a direction perpendicular to the hologram surface,
A method of flattening the shape of the voids by reducing the thickness of the hologram layer, or decompressing the entire hologram layer in the direction perpendicular to the hologram surface, then returning to normal pressure and contracting the hologram layer by atmospheric pressure. There is a method of flattening the shape of the voids, a combination of these methods, or a method of dipping the voids in a solution to shrink the hologram layer in the direction perpendicular to the hologram surface and simultaneously shrink the voids.

This state is shown in the schematic diagram of FIG. The figure (a) shows the cross section of the hologram layer before flattening the minute void, and the figure (b) shows the cross section of the hologram layer after flattening the minute void. High refractive index layers 1 and low refractive index layers 2 are alternately arranged in the hologram layer,
The minute voids 3 are dispersed in the low refractive index layer 2. Before the flattening of FIG. 3A, the micro voids 3 are statistically isotropic, but when pressure or the like is applied as described above,
The minute voids 3 are statistically flat in the direction along the hologram surface, as shown in FIG.

The hologram forming method of the present invention for reducing the haze value while maintaining high diffraction efficiency will be described below. As the record carrier used in the present invention, for example, a photopolymer including a binder polymer, a reactive monomer, a photopolymerization initiator, and a sensitizing dye is used.

As the binder polymer, polymethacrylic acid ester or its partial hydrolyzate, polyvinyl acetate or its hydrolyzate, polystyrene, polyvinyl butyral, polychloroprene, polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene, poly- N-vinylcarbazole or a derivative thereof, poly-N-vinylpyrrolidone or a derivative thereof, a copolymer of styrene and maleic anhydride or a half ester thereof, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylamide, acrylonitrile A copolymer or the like having a monomer selected from the group of copolymerizable monomers as a polymerization component is used.

Preferred are poly-N-vinylcarbazole and derivatives thereof, such as poly-N-vinylcarbazole, vinylcarbazole-styrene copolymer,
Vinylcarbazole-vinyl chloride copolymer, vinylcarbazole-methylmethacrylate copolymer, vinylcarbazole-vinylanthracene copolymer, vinylcarbazole-vinylpyridine copolymer, vinylcarbazole-acrylate copolymer, vinylcarbazole-ethylacrylate Copolymer, vinylcarbazole-acrylonitrile copolymer, vinylcarbazole-butyl acrylate copolymer, vinylcarbazole-nitrovinylcarbazole copolymer, nitrated poly-N-vinylcarbazole, polyvinylaminocarbazole, vinylcarbazole-N-methyl Aminovinylcarbazole copolymer, halogen-substituted poly-N-vinylcarbazole, vinylcarbazole-dibromovinylcarbazole copolymer, polyiodovinyl Carbazole, Po Revenge alkylidene vinylcarbazole, poly propenyl carbazole, and the like.

Next, the reactive monomer will be described.
Examples of the monomer to be used include a monomer having at least one ethylenically unsaturated double bond in one molecule, an oligomer, a prepolymer, and a mixture thereof. Specific examples thereof include unsaturated carboxylic acids and salts thereof, esters of unsaturated carboxylic acids with aliphatic polyhydric alcohol compounds, and amides of unsaturated carboxylic acids with aliphatic polyhydric amine compounds.

More specifically, examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and their halogen-substituted unsaturated carboxylic acids such as chlorinated unsaturated acids. Examples thereof include saturated carboxylic acid, brominated unsaturated carboxylic acid, and fluorinated unsaturated carboxylic acid.

Examples of the salts of unsaturated carboxylic acids include sodium salts and potassium salts of the above-mentioned acids. Further, as the ester of the aliphatic polyhydric alcohol compound and the unsaturated carboxylic acid, ethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, Neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycol acrylate, pentaerythritol Diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacreyl , Dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate,
Sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1 , 3-butanediol dimethacrylate, tetramethylene glycol dimethacrylate, propylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, hexanediol dimethacrylate, 1,4-cyclohexanediol dimethacrylate , Tetra Chi glycol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate,
Dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, sorbitol pentamethacrylate, sorbitol hexamethacrylate, bis- [p- (3-methacryloxy-2-hydroxypropoxy) phenyl]
Examples thereof include dimethyl methane, bis- [p- (acryloxyethoxyphenyl)] dimethyl methane and 2-hydroxypropyl methacrylate.

As the itaconic acid ester, ethylene glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol itaconate, 1,
4-butanediol diitaconate, tetramethylene glycol diitaconate, pentaerythritol diitaconate, sorbitol tetritaconate and the like can be mentioned.

As the crotonic acid ester, ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate,
Examples thereof include sorbitol tetracrotonate.

Examples of the isocrotonic acid ester include ethylene glycol diisocrotonate, pentaerythritol diisocrotonate and sorbitol tetraisocrotonate.

Examples of the maleic acid ester include ethylene glycol dimaleate, pentaerythritol dimaleate and sorbitol tetramaleate.

As the halogenated unsaturated carboxylic acid,
2,2,3,3-tetrafluoropropyl acrylate, 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1H, 1H, 2H, 2H-heptadeca Examples thereof include fluorodecyl methacrylate.

Examples of amides of unsaturated carboxylic acids and aliphatic polyvalent amine compounds include methylenebisacrylamide, methylenebismethacrylamide, 1,6-hexamethylenebisacrylamide, 1,6-hexamethylenemethacrylamide, and diethylenetriamine. Examples thereof include trisacrylamide, xylylenebisacrylamide, xylylenebismethacrylamide, acrylamidobutyraldehyde dimethyl acetal and the like.

Examples of the photopolymerization initiator include benzoin alkyl ethers, ketals, oxime esters, benzophenone, thioxanthone derivatives, quinones, aromatic ketones such as thioacridone, and 1,3-di (t-butyldioxycarbonyl). Alkyl or alkyl borate such as benzene, iodonium salts, dianine, rhodamine, safranine, malite green, methylene blue, iron-
An arene complex, bisimidazoles, N-arylglycine and the like can be used.

The visible light sensitizing dyes include aromatic amines such as Michler's ketone, xanthene dyes, thiopyrylium salts, merosinin / quinoline dyes, coumarin / ketocoumarin dyes, acridine orange, benzoflavin,
Dianine, phthalocyanine, porphine, rhodamine,
Safranin, malachite green, methylene glycol, squarylium dyes and the like are used.

In addition to the above composition, the record carrier also contains
Ingredients such as an oxygen scavenger, a thermal polymerization inhibitor, a plasticizer and an ultraviolet absorber may be added.

As the method for applying the photosensitive solution, there are spinner coating, blade coating, roll coating and the like, and the coating is performed after drying to a film thickness of 0.1 μm to 100 μm. The film thickness is adjusted by the concentration of the composition in the solvent, the film thickness at the time of coating, etc., but a predetermined thick film may be obtained by repeating coating and drying several times. In addition, the support itself of the binder polymer itself may be used to form a film itself.

Further, by coating the surface of the record carrier which is in contact with air with an aqueous solution of polyvinyl alcohol or the like and blocking the air, polymerization inhibition due to oxygen does not occur and sensitivity can be improved.

Next, the hologram forming method of the present invention will be described. In the hologram forming method of the present invention, the exposure step and the development step of the record carrier are performed, and thereafter, in order to reduce the diameter of the minute void in the direction perpendicular to the hologram surface, a physical force is applied to flatten the void. As a method, pressing is performed at a pressure of ² to 10 kg / cm ^{2 in} a direction perpendicular to the hologram surface. When the pressing pressure is 10 kg / cm ² or more, the voids in the low refractive index portion are completely broken, so that the haze value is lowered but the diffraction efficiency is lowered. Also, the pressure is 2 kg / c
When it is m ² or less, the haze value does not decrease because the voids do not become flat. In this way, by reducing the diameter of the minute void in the direction perpendicular to the hologram surface, the scattering of light entering the hologram layer in the minute void is suppressed and the haze value is reduced. However, since the film thickness will change and the diffraction wavelength will change as it is, the film thickness during coating and the incident angle of laser light during exposure should be taken into consideration in consideration of the contraction of the film thickness due to pressing and the change in the interference fringe pitch. Need to decide.

Further, in the method of reducing the diameter of the void with respect to the hologram surface by shrinking under reduced pressure, the pressure in the void in the low refractive index portion of the hologram is reduced by reducing pressure.
When the pressure is returned to atmospheric pressure, the voids shrink and the diameter becomes smaller. At this time, since the hologram layer contracts, it is necessary to determine the film thickness at the time of coating and the incident angle of the laser beam at the time of exposure in consideration of the contraction of the film thickness and the change in the interference fringe pitch.

As is clear from the above, the hologram forming method of the present invention is characterized by compressing in the direction perpendicular to the hologram surface after producing a hologram having a refractive index modulation depending on the presence or absence of a minute void.

Another method of forming a hologram according to the present invention is to prepare a hologram having a refractive index modulation depending on the presence or absence of a minute void, decompress it, then return it to normal pressure and contract it in a direction perpendicular to the hologram surface by atmospheric pressure. Is a method characterized by.

In still another hologram forming method of the present invention, after producing a hologram having a refractive index modulation depending on the presence or absence of minute voids, the pressure is reduced, then returned to normal pressure and contracted in the direction perpendicular to the hologram surface by atmospheric pressure. At the same time, it is characterized by compressing in a direction perpendicular to the hologram surface.

Further, another hologram forming method of the present invention is characterized in that after the hologram having a refractive index modulation depending on the presence or absence of minute voids is prepared, the hologram is contracted in a direction perpendicular to the hologram surface by immersing it in a solution. Is the way.

Further, the hologram of the present invention is characterized in that, in the hologram having a refractive index modulation depending on the presence or absence of the minute void, the minute void is flat in the direction along the hologram surface.

Another hologram of the present invention is a hologram having a refractive index modulation depending on the presence or absence of a minute void, wherein the minute void is flat in the direction along the hologram surface, and the ratio of the short axis to the long axis is 1: 2 or more. It is characterized by being.

Still another hologram of the present invention is a hologram having a refractive index modulation depending on the presence or absence of a minute void, wherein the minute void is flat in the direction along the hologram surface and the length of its minor axis is 30 nm or less. It is a feature.

Another hologram of the present invention is a hologram having a refractive index modulation depending on the presence or absence of a minute void, characterized in that the minute void is flat in the direction along the hologram surface and the haze value of the hologram is 1% or less. It is what

In these, a photopolymer can be used as the hologram recording medium.

[0037]

In the present invention, after the hologram having the refractive index modulation depending on the presence or absence of the minute void is produced, the minute void is flattened in the direction along the hologram surface by compression or the like. The size of the voids can be made quite small, and the minute voids do not serve as scattering centers and have only the effect of lowering the average refractive index. Therefore, the haze value of the hologram can be reduced.

[0038]

EXAMPLES Examples 1 to 3 of the hologram forming method and hologram of the present invention will be described below. [Example 1] Poly-N-vinylcarbazole (manufactured by Anan Fragrance Industry Co., Ltd., Tubicor 210, Mw = 500 to 800,000, refractive index 1.68) 1.0 g Tribromophenoxyethyl acrylate (Daiichi Kogyo) Pharmaceutical Co., Ltd., New Frontier BR-31 1.0 g Trichloro-s-triazine (TCT) (Midori Kagaku Co., Ltd. TAZ-101) 0.07 g Squarylium dye (SQD) ) Ltd., N-2990, a compound having a composition of λ _{MA X} = 650nm) 0.003g were dissolved in chlorobenzene 14.5 g, to obtain a photosensitive solution.

This photosensitive solution was formed into a film having a thickness of 0.1 mm (4 mils) on a glass plate having a thickness of 2.0 mm and dried at 70 ° C. for 10 minutes to obtain a record carrier having a thickness of 8 μm. On the surface of the record carrier, polyvinyl alcohol (Kuraray Co., Ltd.,
A 5 wt% aqueous solution having a saponification degree of 88% and a polymerization degree of 500) was applied by a spin coater and dried.

Next, using the optical system shown in FIG. 2, the hologram was exposed to light having a wavelength of 647.1 nm of a krypton ion laser so that the exposure energy was 10 mJ / cm ² . In FIG. 2, the light from the laser 4 is
The record carrier 9 is divided into two parts by a half mirror 5, direction-changed by mirrors 6 and 6, respectively, and passes through a spatial filter 7 and a beam expander 8 from opposite sides.
And then exposed.

After the exposure, the polyvinyl alcohol film on the surface of the record carrier was removed and then developed. There were two kinds of developing solutions, the first solution was methyl isobutyl ketone and the second solution was heptane. Each of the recording carriers was added to the developer of the above composition in an amount of 9
It was dipped for 0 seconds, 30 seconds, pulled up and dried.

Thereafter, the obtained hologram is sandwiched between rollers, and 6 kg / cm in a direction perpendicular to the hologram surface.
A pressure of ² is applied to flatten the minute voids in the hologram along the hologram surface (Fig. 1 (b)). As a result of taking a cross-sectional photograph of the hologram layer with an electron microscope and examining the length of the minor axis of the void, it was about 20 nm in the direction perpendicular to the hologram surface. Moreover, as a result of measuring the diffraction efficiency, 80%, a haze meter (NDH-1001D manufactured by Nippon Denshoku Industries Co., Ltd.)
In the haze value measurement using P), a result of 1% was obtained,
Diffraction efficiency is about 80% when pressure is not applied, haze value is 10%
Better results have been obtained.

Example 2 Composition A hologram was exposed in the same manner as in Example 1 except that the optical system of FIG. 1 was used for a record carrier having the same composition and structure as in Example 1. After the exposure, the polyvinyl alcohol film on the surface of the record carrier was removed, followed by development treatment with the same developer and drying.

Then, the obtained hologram is put in a decompression device, the pressure is lowered to 10 Pa and kept for 1 hour, and the hologram is contracted by exposing it to the atmosphere. As a result, the minute voids in the hologram are flattened along the hologram surface. Take a cross-sectional photo of the hologram layer with an electron microscope,
As a result of examining the length of the minor axis of the void, it was about 30 nm in the direction perpendicular to the hologram surface. Moreover, as a result of measuring the diffraction efficiency, 80% was obtained, and in the haze value measurement using a haze meter (NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd., 1.
A result of 5% was obtained, and the diffraction efficiency without shrinking under reduced pressure was about 80%, and the result was better than the haze value of 10%.

Example 3 A hologram was exposed in the same manner as in Example 1 by using the optical system of FIG. 1 on a record carrier having the same composition and constitution as in Example 1. After the exposure, the polyvinyl alcohol film on the surface of the record carrier was removed, followed by development treatment with the same developer and drying.

After that, the obtained hologram was put in a vacuum package for 1 hour to reduce the pressure, and the hologram was contracted by exposing it to the atmosphere to make 6 k in a direction perpendicular to the hologram surface.
A pressure of g / cm ² is applied to flatten the minute voids in the hologram along the hologram surface. As a result of taking a cross-sectional photograph of the hologram layer with an electron microscope and examining the length of the minor axis of the void, it was about 20 nm in the direction perpendicular to the hologram surface. Moreover, as a result of measuring the diffraction efficiency, 80%, a haze meter (NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.
A haze value of 1% was obtained in the measurement of the haze value, and the diffraction efficiency was about 80% when the shrinkage and the pressure reduction were not performed, and the haze value was better than 10%.

In the above-mentioned Examples 1 to 3, the case where the photopolymer which is subjected to the developing treatment is used is explained, but the hologram recording of the silver salt, dichromated gelatin, the photopolymer which is not subjected to the developing treatment and the like. The haze value can be similarly reduced by using a material.

[0048]

As is apparent from the above description, according to the present invention, after the hologram having the refractive index modulation depending on the presence or absence of the minute void is formed, the minute void is flattened in the direction along the hologram surface by compression or the like. The size of the void in the traveling direction can be made considerably smaller than the wavelength of light, and the minute void does not serve as a scattering center and has only the effect of lowering the average refractive index. Therefore, the haze value of the hologram can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a state before and after flattening a minute void in a hologram layer according to the present invention.

FIG. 2 is a schematic diagram of a Lippmann exposure optical system for exposing a mirror hologram that reflects visible light.

[Explanation of symbols]

1 ... High refractive index layer 2 ... Low refractive index layer 3 ... Micro void 4 ... Laser 5 ... Half mirror 6 ... Mirror 7. Spatial filter 8 ... Beam expander 9 ... Record carrier

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03H 1/02 G03H 1/04

Claims (8)

(57) [Claims] 1. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
A method for forming a hologram, characterized in that the reactive monomer of the combination is eluted , a hologram having a refractive index modulation depending on the presence or absence of minute voids is produced, and then compressed in a direction perpendicular to the hologram surface. 2. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
It is characterized by eluting the reactive monomer of the combination and producing a hologram having a refractive index modulation depending on the presence or absence of micro voids, decompressing, and then returning to normal pressure and contracting in the direction perpendicular to the hologram surface by atmospheric pressure. Hologram forming method. 3. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
The reactive monomer is dissolved out to create a hologram that has a refractive index modulation depending on the presence or absence of minute voids, and then the pressure is reduced and then returned to normal pressure to shrink in the direction perpendicular to the hologram surface due to atmospheric pressure. A hologram forming method characterized by compressing in a vertical direction. 4. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
A method for forming a hologram, characterized in that the reactive monomer of the combination is eluted and a hologram having a refractive index modulation depending on the presence or absence of micro voids is produced, and then immersed in a solution to shrink in a direction perpendicular to the hologram surface. 5. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
In the hologram recorded by elution of the reactive monomer of
A hologram characterized in that minute voids are flat in the direction along the hologram surface. 6. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
Used as program recording medium, non-heavy after hologram exposure light
In the hologram recorded by elution of the reactive monomer of
A hologram characterized in that minute voids are flat in the direction along the hologram surface, and the ratio of the short axis to the long axis is 1: 2 or more. 7. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
In the hologram recorded by elution of the reactive monomer of
A hologram in which minute voids are flat in the direction along the hologram surface and the length of the minor axis is 30 nm or less. 8. A binder polymer, a reactive monomer,
A photopolymer consisting of a photopolymerization initiator and a sensitizing dye is
It is used as a program recording medium and is not weighted after hologram exposure.
In the hologram recorded by elution of the reactive monomer of
A hologram in which minute voids are flat in the direction along the hologram surface, and the haze value of the hologram is 1% or less.