JP2003241625A - Volume hologram recording composition and volume hologram recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a volume hologram recording medium having the various functions possessed by inorganic particles, the workability possessed by high polymers and the ease of moldability in combination. <P>SOLUTION: The volume hologram recording composition which is a volume hologram recording composition for recording the interference fringes produced by interference of coherent light by differences in refractive indices and contains (a) a compound (functional compound) having ≥1 polymerizble functional group, (b) a photopolymerization initiator, (c) the inorganic particles, and (d) a chain- transfer agent and the volume hologram recording medium using the same. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volume hologram recording medium for recording interference fringes by a refractive index difference inside a recording layer, and a volume hologram recording composition used for the recording layer.

[0002]

2. Description of the Related Art A hologram records a pattern formed by two interference fringes on a photosensitive material and irradiates it with the same laser light in the same direction as the reference light. Is played back and appears. This hologram technology is expected in the fields of three-dimensional image display devices, images, large-capacity memory for bit information, and diffractive optical elements.

Holograms are classified into several types according to the recording pattern of interference fringes. In recent years, so-called volume holograms, which record interference fringes by the difference in refractive index inside the recording layer, are being applied to applications such as three-dimensional displays and optical elements due to their high diffraction efficiency and excellent wavelength selectivity. As a light-sensitive material for recording such a volume hologram, silver halide and dichromated gelatin have been conventionally used. However, since these require wet development and complicated developing and fixing processing, the hologram is industrially used. However, it has a problem that an image disappears due to moisture absorption after recording.

In order to remedy the above-mentioned problems of the prior art, it is possible to prepare a volume hologram by using a photopolymer only by a simple dry process. US Pat. No. 3,658,
526 and U.S. Pat. No. 3,993,485. Regarding the presumed formation mechanism of the hologram by the photopolymer, "Applied optics (APPL
IED OPTICS) "[B. L. Booth (BL
Booth, Vol. 14, No. 3, 593-601
Page (1975), and W.S. J. Tomlinson (WJ.
Tomlinson), E.I. A. Chandros (E.
A. Handros, et al., Volume 15, No. 2, pp. 534-541 (1976)] and the like. However, these technologies at the beginning were inferior to the conventional technologies in terms of refractive index modulation, which is a particularly important performance.

As an improved technique, for example, US Pat. No. 4,942,102 and US Pat.
However, since they use a non-reactive plasticizer in order to improve the refractive index modulation ability, they have a problem in the film strength of the formed hologram. Rate modulation was also not sufficient. Therefore, in JP-A-5-107999, a photopolymer-based composition as a photosensitizer for forming a recording layer, that is,
Of (a) a cationically polymerizable compound, (b) a radically polymerizable compound, (c) a photoradical polymerization initiator system for polymerizing (b), and (d) a cationic polymerization initiator system for polymerizing (a). A composition containing each component and having an average refractive index of (a) lower than the average refractive index of (b) is proposed, and the use of this composition provides diffraction efficiency, wavelength selectivity, It is said that a hologram excellent in refractive index modulation and film strength can be obtained.

However, the photopolymer-based composition is composed of only organic materials and is still insufficient in mechanical strength and environmental stability, and it is difficult to add new functions such as nonlinear optical characteristics. There was a problem that was.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to disperse inorganic fine particles in a functional compound to permanently form a hologram having high recording sensitivity and high diffraction efficiency. To provide.

[0008]

The gist of the present invention is a volume hologram recording composition for recording interference fringes caused by interference of coherent light by means of a difference in refractive index.
A volume hologram recording composition comprising a compound having one or more polymerizable functional groups (functional compound), (b) a photopolymerization initiator, (c) inorganic fine particles, and (d) a chain transfer agent. Exist in.

Another subject matter of the present invention resides in a volume hologram recording medium containing the composition.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The composition for volume hologram recording of the present invention comprises at least (a) a compound having one or more polymerizable functional groups, (hereinafter referred to as component (a) or a functional compound, a functional monomer and A), (b) a photopolymerization initiator for initiating the polymerization of the component (a) (hereinafter sometimes referred to as a component (b)), (c) an inorganic fine particle (hereinafter referred to as a component (c)). And (d) a chain transfer agent (hereinafter sometimes referred to as component (d)).

According to the present invention, it is possible to provide a volume hologram composition in which a hologram having a high diffraction efficiency is permanently formed by dispersing inorganic fine particles in a functional compound. In order to obtain a hologram having a high diffraction efficiency, it is necessary to increase the difference in the refractive index between the bright portion and the dark portion of the interference fringe.

As a volume hologram recording composition, a composition composed of a plurality of functional monomers having different refractive indexes, a composition composed of a liquid organic material and a functional monomer, and the like have been conventionally known. Usually 1.3 to 1.6
Since there is a limit to the extent, there is a limit in increasing the refractive index difference in the combination of organic substances. On the other hand, inorganic fine particles made of a dielectric material, a semiconductor, a metal, or the like have various refractive indexes, and many materials have a refractive index of 2 or more. Therefore, even in combination with an organic substance, a large difference in refractive index can be obtained, and thus a hologram having a high diffractive light rate can be obtained.

Further, conventional volume hologram recording compositions consisting only of organic substances generally have low mechanical strength and tend to be inferior in environmental stability and nonlinear optical characteristics. According to the present invention, by containing inorganic fine particles, the features such as high mechanical strength, high environmental stability, and excellent nonlinear optical properties of the inorganic fine particles are added to the photopolymer-based volume hologram composition. You can also do it.

In particular, when a metal oxide is used as the inorganic fine particles, it can have a high UV blocking function, and when semiconductor fine particles are used, it can have a non-linear optical characteristic. That is, according to the present invention, by dispersing the inorganic fine particles in the functional monomer, the volume hologram recording composition having various functions of the inorganic fine particles and the processability of the polymer and the ease of molding are provided. Also, a volume hologram recording medium can be provided.

Next, a hologram recording method for a recording medium using the volume hologram recording composition of the present invention will be described. The recording principle is not clear, but it is presumed as follows. First, when the medium is irradiated with two laser beams at the same time, an interference fringe is formed on the medium in which bright portions and dark portions are arranged in stripes. Then, the functional monomer (functional compound) of (a) starts to polymerize in the bright portion of the medium, and the concentration of the functional monomer in the bright portion decreases. Accordingly, a concentration gradient of the functional monomer is generated between the dark portion and the light portion, the functional monomer is diffused and supplied from the dark portion to the light portion, and the polymerization further proceeds. As the monomer diffuses and moves, the inorganic fine particles move from the dark part to the bright part, and uneven distribution occurs in the inorganic fine particles in the bright part and the dark part. (In exchange, the inorganic fine particles move from the light portion to the dark portion. And, the distribution of the inorganic fine particles is unevenly distributed between the light portion and the dark portion.) After a certain period of time, finally, even in the dark portion, the amount of the functional monomer is changed. Polymerization proceeds, and the entire recording layer of the medium becomes a polymer.

In this way, a stripe-shaped distribution of the inorganic fine particles can be formed in the polymer of the functional monomer corresponding to the light and dark portions. Since the refractive index of the inorganic fine particles is different from the refractive index of the functional monomer in the polymerized state, a refractive index distribution is formed in the recording layer and a hologram is recorded. At the time of reproduction, when the reproduction light is applied to the area where the interference fringes are formed, diffraction occurs and the hologram image is reproduced.

The constitution of the volume hologram recording composition of the present invention will be described in detail below. The component (a) contains, for example, an ethylenically unsaturated compound. The ethylenically unsaturated compound is a compound having at least one radically polymerizable ethylenically unsaturated bond in the molecule which undergoes addition polymerization by the action of the photopolymerization initiator of the component (b), and is crosslinked or cured in some cases. is there. In addition, the meaning of the sensitive compound in the present invention is a concept facing a so-called polymer substance, and therefore includes not only a narrowly defined monomer (monomer) but also a dimer, a trimer and an oligomer. It is a thing.

Examples of the functional monomer having an ethylenically unsaturated bond include unsaturated carboxylic acids, esters of aliphatic polyhydroxy compounds with unsaturated carboxylic acids; esters of aromatic polyhydroxy compounds with unsaturated carboxylic acids; Examples thereof include esters obtained by an esterification reaction of a saturated carboxylic acid with a polyvalent carboxylic acid and the above-mentioned aliphatic polyhydroxy compound, polyvalent hydroxy compound such as aromatic polyhydroxy compound, and the like.

The ester of the aliphatic polyhydroxy compound and the unsaturated carboxylic acid is not limited, but specific examples thereof include ethylene glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate. Acrylic esters such as pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, glycerol acrylate, etc. Methacrylic acid ester replaced, Itaconic acid ester similarly replaced with itaconate Crotonate is maleic acid ester, and was replaced with crotonic acid ester or maleate was replaced.

Examples of the ester of an aromatic polyhydroxy compound and an unsaturated carboxylic acid include hydroquinone diacrylate, hydroquinone dimethacrylate, resorcin diacrylate, resorcin dimethacrylate and pyrogallol triacrylate. The ester obtained by the esterification reaction of an unsaturated carboxylic acid with a polyvalent carboxylic acid or a polyvalent hydroxy compound is not necessarily a single substance, but representative specific examples include acrylic acid, phthalic acid and ethylene glycol. Examples thereof include condensates, condensates of acrylic acid, maleic acid and diethylene glycol, condensates of methacrylic acid, terephthalic acid and pentaerythritol, condensates of acrylic acid, adipic acid, butanediol and glycerin.

In addition to the above ester (meth) acrylates, there are so-called urethane (meth) acrylates and epoxy (meth) acrylates. The former can be prepared by an addition reaction between a polyvalent isocyanate and hydroxyacrylic esters, and the latter can be prepared by an addition reaction between a polyvalent epoxy compound and hydroxyacrylic esters.

Other examples of the ethylenically unsaturated compound used in the present invention include acrylamides such as ethylenebisacrylamide; allyl esters such as diallyl phthalate; and vinyl group-containing compounds such as divinylphthalate. In the present invention, of the ethylenically unsaturated compounds, acrylic acid ester or methacrylic acid ester monomers are particularly preferable.

Each of the functional monomers may be used alone, or may be mixed and used if necessary. The component (b) is a polymerization initiator that initiates the polymerization of the functional monomer of the component (a), and there are cationic polymerization initiators and the like, but it is particularly preferable that it is a photoradical polymerization initiator. The photoradical polymerization initiator generates active radicals by recording light for hologram production.

The radical polymerization initiator includes the component (a)
The substance is not particularly limited as long as it functions as a polymerization initiator, for example, azo compounds, azide compounds, organic peroxides, onium salts, bisimidazole derivatives, titanocene compounds, iodonium salts, organic thiol compounds,
A halogenated hydrocarbon derivative or the like is used. Of these, titanocene compounds are preferred.

The titanocene compound is not particularly limited, but specifically, di-cyclopentadienyl-Ti-
Di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, di-cyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, dicyclopentadi Enyl-Ti-bis-2,3
5,6-Tetrafluorophen-1-yl, Di-cyclopentadienyl-Ti-bis-2,4,6-trifluorophen-1-yl, Di-cyclopentadienyl-Ti
-Bis-2,6-di-fluorophen-1-yl, di-
Cyclopentadienyl-Ti-bis-2,4-di-fluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1- Il, di-methylcyclopentadienyl-
Ti-bis-2,3,5,6-tetrafluorophenyl
1-yl, di-methylcyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,6-difluoro-3
-(Pyr-1-yl) -phen-1-yl etc. can be mentioned.

The photoradical polymerization initiator of the present invention may be used alone, or may be used in combination with a sensitizer which is a component that absorbs light. Specific examples of preferable sensitizers include, for example, 2,6-diethyl-1,3,5,7,8-
Pentamethylpyrromethene-BF ₂ complex, 1, 3, 5,
Pyrromethene complexes such as 7,8-pentamethylpyrromethene-BF ₂ complex; xanthene dyes such as eosin, ethyleosin, erythrosine, fluorescein and rose bengal; 1- (1-methylnaphtho [1,2-d] thiazole -2 (1H) -ylidene-4- (2,3,6,7)
Tetrahydro-1H, 5H-benzo [ij] quinolidin-9-yl) -3-buten-2-one, 1- (3-methylbenzothiazole-2 (3H) -ylidene-4- (p
Ketothiazoline compounds such as -dimethylaminophenyl) -3-buten-2-one; 2- (p-dimethylaminostyryl) -naphtho [1,2-d] thiazole, 2-
A styryl or phenylbutadienyl heterocyclic compound such as [4- (p-dimethylaminophenyl) -1,3-butadienyl] -naphtho [1,2-d] thiazole; 2,
4-diphenyl-6- (p-dimethylaminostyryl)
-1,3,5-triazine, 2,4-diphenyl-6-
(([2,3,6,7] Tetrahydro-1H, 5H-benzo [ij] quinolidin-9-yl) -1-ethene-2
-Yl) -1,3,5-Nanthryl such as triazone-
(([2,3,6,7] Tetrahydro-1H, 5H-benzo [ij] quinolidin-9-yl) -1-ethene-2
-Yl) ketone, aminophenyl unsaturated ketone compounds such as 2,5-bis (p-dimethylaminocinnamylidene) cyclopentanone; 5,10,15,20 tetraphenylporphyrin, porphyrins such as hematoporphyrin Etc. can be mentioned. The preferred sensitizers have been exemplified above, but of these, the pyrromethene complex is particularly preferable.

As described above, a color compound such as a dye is often used as the sensitizer to absorb visible laser light, but when the final hologram is required to be colorless and transparent (for example, As a sensitizer for use as a head-up display for automobiles, etc., JP-A-58-58
It is preferable to use a cyanine dye as described in JP-A-29803, JP-A-1-287105 and JP-A-3-5569.

When a titanocene compound is used as the photoradical generator, a pyrromethene compound is preferably used as the sensitizer. The inorganic fine particles of component (c) preferably have a refractive index difference of 0.01 or more from the polymerization state of the functional monomer of component (a). This is because it is desirable that the difference in the refractive index between the inorganic fine particles and the functional monomer polymerization state is large in order to increase the final refractive index modulation when the functional monomer is polymerized by hologram exposure. It is more preferably 0.03 or more.

However, the difference in refractive index is preferably 1.3 or less. This is because, in consideration of light scattering, the larger the difference in refractive index, the smaller the particle size needs to be. It is more preferably 1.1 or less. In the present invention, the “polymerization state of the functional monomer” means a state in which the functional monomer is almost completely polymerized.

The particle size of the inorganic fine particles of component (c) is 400 n
m or less. This is because if it is too large, light scattering is likely to occur. It is more preferably 200 nm or less.
The smaller the particle size, the more preferable, but the smaller the particle size, the more difficult it is to manufacture, so the particle size is practically limited to 1 nm or more. Further, since the refractive index in the volume hologram composition is determined by the volume ratio of the constituent components, the achievable difference in refractive index becomes larger as the volume ratio of the inorganic fine particles to the volume of the resin component becomes larger.
Therefore, the proportion of the inorganic fine particles in the total volume of the inorganic fine particles and the resin component in the polymerized state is preferably 3% by volume or more, and more preferably 5% by volume or more.

However, the amount of the inorganic fine particles that can be dispersed in the composition is limited, and if it is too large, it becomes difficult to disperse it. Therefore, it is preferably 50% by volume or less, more preferably 40% by volume or less. Here, the resin component is, for example, the functional monomer of (a), but when the volume hologram composition includes a binder resin, it indicates the functional monomer of (a) and the binder resin.

The component (c) is not particularly limited as long as it is an inorganic fine particle that can achieve the object of the present invention.
For example, titanium oxide, silicon oxide, zinc oxide, aluminum oxide, antimony oxide, chromium oxide, cerium oxide, yttrium oxide, zirconium oxide, tin oxide,
Metal oxides such as copper oxide, iron oxide, magnesium oxide, manganese oxide, holmium oxide, bismuth oxide, cobalt oxide, erbium oxide, gadolinium oxide, indium oxide, nickel oxide, strontium oxide, ytterbium oxide; silicon nitride, titanium nitride , Nitrides such as zirconium nitride and niobium nitride; silicon carbide, titanium carbide,
Dielectric particles such as carbides such as molybdenum carbide and tungsten carbide, group IV semiconductors such as Si and Ge, CdS and Cd
Se, ZnSe, CdTe, ZnS, HgS, HgSe
II-VI group semiconductor fine particles such as GaAs, InP, I
III-V group semiconductor fine particles such as nSb, PbS, PbS
IV-VI group semiconductor fine particles such as e, gold, silver, copper, nickel,
There is no particular limitation as long as it is a fine metal particle such as aluminum, iron, cobalt, tungsten, molybdenum, or niobium, which can be uniformly dispersed in the functional monomer.

In order to uniformly disperse the particles, it is preferable to chemically modify the surface during the preparation of the fine particles, or to add a dispersant after the preparation of the fine particles. The above fine particles can be used alone, in a mixture or in a complex. In addition, in the case of titanium oxide, which has a photocatalytic reaction, in order to prevent the resin from being decomposed by the reaction, the surface may be coated with a silicon compound or the like, if necessary.

The chain transfer agent of the component (d) limits the size of the photopolymer produced by the polymerization of the component (a), thereby suppressing the viscosity at the initial stage of exposure and assisting the movement of the inorganic fine particles (c), It is considered that it works to improve recording sensitivity. In the present invention, the composition ratio of the component (d) is the component (a)
0.1 to 50 parts by weight of component (d) per 100 parts by weight,
Preferably, component (d) is added to 100 parts by weight of component (a).
It is in the range of 1 to 30 parts by weight. When the proportion of the component (d) is small, the effect of improving the recording sensitivity cannot be obtained, and conversely, when the proportion is too large, the mechanical strength of the photopolymer becomes low. Further, it is important to use the component (d) at the same time as the inorganic fine particles of the component (c), and in the absence of the component (c), a permanent hologram cannot be formed.

The component (d) is not particularly limited as long as it is a chain transfer agent which can achieve the object of the present invention.
For example, a mercapto compound having a thiol group, di-n
Examples include disulfide compounds such as -butyl disulfide and amino compounds such as N-phenylglycine derivatives. Particularly, a mercapto compound having one or more thiol groups is preferable. For example, 2-mercaptobenzothiazole, 2-mercaptonaphthalene, thiomalic acid, stearyl mercaptan, 2-mercaptopropionic acid,
Dimethylaminoethanethiol hydrochloride, β-mercaptoisobutyric acid, 2,2 ′-(ethylenedithio) diethanethiol, meso-2,3-dimercaptosuccinic acid, phenylthioethanethiol, methyl 6-mercaptohexylate, 2 -Mercaptoethyloctanoic acid ester, thiosalicylic acid, 4-mercaptopyridine, 4-mercaptophenol, pt-butylthiophenol, o-thiocresol, 2,4-dimethylthiophenol, p-methoxythiophenol, 3,5 -Dichlorothiophenol, p-xylenedithiol, m-xylenedithiol, 3-mercaptopropionic acid, methyl mercaptopropionate, methoxybutyl mercaptopropionate,
Octyl mercaptopropionate, tridecyl mercaptopropionate, ethylene glycol bisthiopropionate, diethylene glycol bisthiopropionate, triethylene glycol bisthiopropionate,
Butanediol bisthiopropionate, trimethylolpropane tristhiopropionate, pentaerythritol tetrakisthiopropionate, dipentaerythritol hexakisthiopropionate, thioglycolic acid, ammonium thioglycolate, thioglycolic acid monoethanolamine , Methyl thioglycolate, monoethanolamine thioglycolate, methyl thioglycolate, octyl thioglycolate, methoxybutyl thioglycolate, ethylene glycol bisthioglycolate, diethylene glycol bisthioglycolate,
Triethylene glycol bisthioglycolate, butanediol bisthioglycolate, hexanediol bisthioglycolate, trimethylolpropane tristhioglycolate, pentaerythritol tetrakisthioglycolate, dipentaerythritol hexakisthioglycolate, tris [2- (Β-Thiopropionyloxy) ethyl] triisocyanurate, Tris (2-thioglyconyloxyethyl) triisocyanurate, Tris [2- (β-thiopropionyloxyethoxy) ethyl] triisocyanurate, Tris (2-thio) Glyconyloxyethoxyethyl) triisocyanurate, tris [3- (β-thiopropionyloxy) propyl] triisocyanurate, tris (3-thioglyconyloxypropyl) trii Cyanurate, benzenedicarboxylic mercaptan, xylylene mercaptans, such as 4,4'-dimercapto sulfide and the like.

In the recording layer of the volume hologram recording medium of the present invention, in addition to the above components (a) to (d), if necessary, additives such as a sensitizer, a plasticizer and a coloring agent may be added. good. A binder resin may be added as a binder in order to make the film thickness uniform and to allow the interference film formed by polymerization by light irradiation to exist stably. The binder resin preferably has good compatibility with the functional monomer, and specific examples thereof include chlorinated polyethylene, polymethylmethacrylate, copolymers of methylmethacrylate and other (meth) acrylic acid alkyl esters, vinyl chloride and acrylonitrile. Examples thereof include copolymers, polyvinyl acetate, polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, ethyl cellulose, acetyl cellulose and the like.

To prepare a volume hologram recording medium using the volume hologram recording composition of the present invention, the components (a), (b), (c) and (d) are sensitized as necessary. Mixed with the agent and the binder resin, and coated on a transparent support as it is without solvent, or may be mixed by adding a solvent or an additive to these mixtures, which is coated on a support and dried. A recording layer is formed. Subsequently, a transparent support or a protective layer for blocking oxygen may be provided on the recording layer.

The solvent is not particularly limited as long as it has a sufficient solubility for the components used and gives a good coating property. For example, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve. Cellosolve solvent such as acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol such as dipropylene glycol dimethyl ether System solvent, butyl acetate, amyl acetate,
Ester solvents such as ethyl acetate, butyl acetate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate ethyl acetoacetate, methyl lactate, ethyl lactate, methyl 3-methoxypropionate, butanol, heptanol, hexanol, diester. Alcohol solvents such as acetone alcohol and furfuryl alcohol, ketone solvents such as methyl isobutyl ketone, cyclohexanone and methyl amyl ketone, highly polar solvents such as dimethylformamide and dimethylacetamide N-methylpyrrolidone, or mixed solvents thereof. , Those to which an aromatic hydrocarbon is added, and the like. The ratio of the solvent used is usually in the range of about 1 to 20 times by weight with respect to the total amount of the volume hologram composition of the present embodiment.

As the transparent support, a transparent glass plate, acrylic plate, polyethylene terephthalate film, polyethylene film or the like is used. As the coating method, conventionally known methods, for example, spin coating, wire bar coating, dip coating, air knife coating, roll coating,
Blade coating, curtain coating and the like can be used.

As the protective layer, known techniques for preventing adverse effects such as sensitivity deterioration and storage stability deterioration due to oxygen,
For example, application of a water-soluble polymer or the like can also be used. The volume hologram recording medium can be used for a three-dimensional image display, an image, a large capacity memory for bit information, a diffractive optical element, and the like.

[0041]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. (Example 1) Functional monomer (compound (I) below) 5 g Silica (SiO ₂ ) fine particles 5 g Photopolymerization initiator (titanocene compound (II) below) 0.1 g Chain transfer agent (pentaerythritol tetrakisthiopropionate, Compound (III) below 0.5 g Solvent (toluene) 45 g

[0042]

[Chemical 1]

[0043]

[Chemical 2]

[0044]

[Chemical 3]

The silica fine particles had a refractive index of 1.46, the functional monomer (I) had a refractive index in the polymerized state of 1.60, and the difference in refractive index between them was 0.14. Since the density of silica fine particles is 2.1 g / cm ³ , its volume is 5
/2.1=2.38 cm ³ . Since the density of the functional monomer (I) in the polymerized state is 1.25 g / cm ³ , its volume is 5 / 1.25 = 4 cm ³ .
Therefore, the ratio of the silica fine particles to the volume of the polymerized state of the silica fine particles and the functional monomer (I) is 2.38 /
(2.38 + 4) = 0.37, that is, 37.3% by volume.

The above mixture was stirred at room temperature and further sonicated to sufficiently disperse it. The particle size of the silica fine particles in the dispersion is Microtrac UPA measured by the Doppler scattering method.
When measured with a particle size distribution meter (manufactured by LEED & NORTHRUP), the median value was 97.1 nm. Next, a polyethylene terephthalate film having a thickness of 50 μm was attached as a spacer to both ends of the slide glass, the mixture was dropped in the center of the slide glass (area sandwiched between the spacers), and dried in a vacuum oven at 80 ° C. for 10 minutes under reduced pressure. A recording layer was formed. After that, a slide glass was covered to produce a volume hologram recording medium.

Two-beam interference exposure was performed on this recording medium by the apparatus shown in FIG. 1 to try to record a volume hologram. An exposure power density of 10 mW / cm ^{2 is applied} to the medium 1 by using an argon ion laser 2 having a wavelength of 514.5 nm.
Two-beam interference exposure was performed. The light emitted from the argon ion laser 2 passes through the beam expander 3 and is split into two by the half mirror 4, and is irradiated onto the medium 1 through the mirrors 5 and 6, respectively, and interference fringes of both lights are recorded to form a hologram. It

At the same time, the wavelength 632.
The hologram formation process was temporally monitored by irradiating the medium 1 with an 8 nm helium neon laser 7 and detecting the diffracted light with the photodetector 10, and the diffraction efficiency was evaluated by the ratio of the diffracted light intensity to the incident light intensity. . A graph showing the change in diffraction efficiency of this sample over time is shown in FIG. The diffraction efficiency increased rapidly, reaching 30% in about 15 seconds, and finally a high diffraction efficiency of 37% was maintained. That is, it was confirmed that a hologram having a diffraction efficiency of about 37% was permanently formed.

Comparative Example 1 A volume hologram recording medium was produced in the same manner as in Example 1 except that the chain transfer agent was not included. Two-beam interference exposure was performed on this medium by the apparatus shown in FIG. 1 in the same manner as in Example 1, and recording of a volume hologram was tried. A graph showing the change in diffraction efficiency of this sample over time is shown in FIG. Permanent hologram formation is observed, but the rise of diffraction efficiency is lower than that in Example 1, and the final diffraction efficiency is also about 22%, which is lower than that in Example 1.

(Comparative Example 2) A volume hologram recording medium was produced in the same manner as in Example 1 except that the chain transfer agent and the inorganic fine particles were not included. Two-beam interference exposure was performed on this medium by the apparatus shown in FIG. 1 in the same manner as in Example 1, and recording of a volume hologram was tried. A graph showing the change in diffraction efficiency of this sample over time is shown in FIG. Diffraction efficiency improves once, but declines over time and eventually disappears. Since this is a single component of the functional monomer, the refractive index modulation disappears when the whole is polymerized.

(Comparative Example 3) A volume hologram recording medium was produced in the same manner as in Example 1 except that the inorganic fine particles were not included. Two-beam interference exposure was performed on this medium by the apparatus shown in FIG. 1 in the same manner as in Example 1, and recording of a volume hologram was tried. A graph showing the change in diffraction efficiency of this sample over time is shown in FIG. The diffraction efficiency once improves as in Comparative Example 1, but decreases with the passage of time, and finally disappears almost. This is because the chain transfer agent is related to the limitation of the molecular weight of the polymer, does not have a function of maintaining the refractive index modulation, and the polymer is composed of a single functional monomer component. It corresponds to the disappearance of the refractive index modulation when the whole is polymerized.

[0052]

According to the present invention, by dispersing inorganic fine particles in a functional monomer and adding a chain transfer agent at the same time, various functions of the inorganic fine particles and processability and moldability of the polymer can be obtained. It is possible to provide a volume hologram recording composition and a volume hologram recording medium which have both high easiness and high recording sensitivity and high diffraction efficiency.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of two-beam interference exposure on a volume hologram recording medium.

FIG. 2 shows the diffraction efficiency (Diffraction Efficien) of the volume hologram recording media in Example 1 and Comparative Examples 1, 2, and 3.
cy) is a graph showing changes over time.

[Explanation of symbols]

1 Holographic Recording Medium 2 Ar ⁺ Laser 3 Beam Expander 4 Half Mirrors 5, 6, 8, 9 Mirror 7 He-Ne Laser 10 Photodetector

Claims (7)

[Claims] 1. A volume hologram recording composition for recording interference fringes generated by interference of coherent light by a difference in refractive index, wherein (a) a compound having one or more polymerizable functional groups (functionality). Compound), (b) photopolymerization initiator,
A volume hologram recording composition comprising (c) inorganic fine particles and (d) a chain transfer agent. 2. The difference between the refractive index of the inorganic fine particles and the refractive index of the functional compound in the polymerized state is 0.01 or more.
The volume hologram recording composition according to claim 1, which is 3 or less. 3. The inorganic fine particles have a particle size of 1 nm or more,
The volume hologram recording composition according to claim 1, which has a thickness of 400 nm or less. 4. The volume hologram according to claim 1, wherein the ratio of the inorganic fine particles to the total volume of the inorganic fine particles and the resin component in the polymerized state is 3% by volume or more and 50% by volume or less. Recording composition. 5. The volume hologram recording composition according to claim 1, wherein the chain transfer agent is a compound having at least one thiol group. 6. A volume hologram recording medium, characterized in that the recording layer contains the composition according to any one of claims 1 to 4. 7. The volume hologram recording medium according to claim 5, further comprising transparent substrates on both sides of the recording layer.