JP2005181954A - Holographic recording medium, holographic recording method, and holographic information medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holographic recording medium having high sensitivity and excellent storage stability, a holographic recording method, and a holographically recorded holographic information medium. <P>SOLUTION: In the holographic recording medium wherein a holographic recording layer is held between a first base and a second base, the holographic recording layer contains at least a binder-forming compound, a compound having an ethylenically unsaturated bond, and a photopolymerization initiator which can initiate a polymerization reaction of the compound having an ethylenically unsaturated bond, as compositions, wherein the content of the compound having an ethylenically unsaturated bond is within the range of 1-50 mass% relative to the total amount of the composition and the photopolymerization initiator contains at least a compound represented by general formula (1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a holographic recording medium capable of increasing the capacity and transferring at a high speed, and further relates to a holographic recording method and a holographic information medium on which information is recorded.

  In recent years, the exchange of high-speed and large-capacity data due to the spread of the Internet and broadbandization has increased, and the capacity of data stored in each affiliated organization has expanded rapidly due to the expansion of e-government promoted by governments in each country. Yes. Furthermore, it is expected that high-capacity recording media will be required in the future due to the spread of high-definition television broadcasting and the spread of digital terrestrial broadcasting. Among them, next-generation optical recording such as Blu-ray discs and HD DVD discs The media is expected to spread in the future. However, for the next generation of recording media, various methods have been proposed, but they are still unattended.

  Among these next-generation recording media, page-type memory systems, especially holographic recording, have been proposed as an alternative to conventional memory devices, and are high-capacity and high-speed transfer systems that allow random access. That has attracted attention in recent years. Details of the holographic recording are described in several reviews (for example, see Non-Patent Document 1).

  As a recording method in this holographic recording, for example, a recording method using a holographic recording medium in which a transparent base material is disposed on both sides of the holographic recording layer (see, for example, Patent Document 1), or a holographic recording layer. A recording method using a holographic recording medium provided with a reflecting surface arranged on one side of the recording medium (for example, see Patent Document 2) has been proposed.

  Such a holographic recording medium records information by changing the refractive index in the holographic recording layer in the medium by holographic exposure, and reads the change in the refractive index in the recorded medium. This is based on the principle of reproducing information, and as this holographic recording layer, a material using an inorganic material (for example, see Patent Document 3), a material using a compound that undergoes structural isomerization with light (for example, , Patent Document 4), or materials utilizing diffusion polymerization of photopolymers (see, for example, Patent Document 5). Among these, in the material using the photopolymer described in Patent Document 5, a volatile solvent is used when producing the recording layer forming composition, and therefore the thickness of the recording layer is about 150 μm at the maximum. Limited. Furthermore, the 4-10% volume shrinkage caused by the polymerization had an adverse effect on the reliability in reproducing the recorded information.

  In order to improve the above-mentioned drawbacks, there have been proposed holographic recording layer forming compositions (for example, see Patent Document 6) that use cationic polymerization with no solvent and relatively little system shrinkage. However, since the recording layer forming composition is a liquid substance other than the monomer that causes photocationic polymerization, the island-shaped portion formed by photopolymerization of the monomer in the recording layer may move due to holographic exposure. And the volume of the liquid material expands due to the change of the environmental temperature in the apparatus.

  In order to improve such disadvantages, radical polymerization is used for recording in holographic exposure, and a composition is formed by forming a binder after media formation in order to retain the monomer capable of radical polymerization before the exposure (for example, patent documents) 7) and the like, and by using such a composition, the film thickness of the holographic recording layer can be increased and the volume shrinkage can be reduced, but it cannot be said that it is still sufficient. .

On the other hand, when holographic recording is performed on a holographic recording medium, exposure with low energy is essential for improving the recording speed. In order to improve the recording speed, in other words, the recording sensitivity, it is important to select and combine the monomers used for diffusion polymerization, the binder-forming compound, the sensitizing dye, and the radical initiator. On the other hand, photosensitive compositions for hologram recording using imidazole as an initiator (see, for example, Patent Documents 8 and 9) have been proposed, and such systems can improve sensitivity and various physical properties. However, since a polymer is used as a binder, a solvent is required when producing a photosensitive composition for hologram recording, and the recording layer thickness cannot be sufficiently obtained.
Hans J.H. Coufar et al., "Holographic Data Storage (Springer Series in Optical Sciences, Vol 76)" (Springer-Verlag GmbH & Co. KG, August 2000). US Pat. No. 5,719,691 JP 2002-123949 A British patent 9,929,953 JP 10-340479 A US Pat. No. 4,942,112 US Pat. No. 5,759,721 US Pat. No. 6,103,454 US Pat. No. 5,027,436 International Publication No. 03/081344 Pamphlet

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a holographic recording medium, a holographic recording method, and a holographic information medium on which holographic recording has been performed. There is in providing.

The above object of the present invention can be achieved by the following configuration.
(Claim 1)
In a holographic recording medium in which a holographic recording layer is sandwiched between a first substrate and a second substrate, the holographic recording layer has a binder-forming compound and an ethylenically unsaturated bond as a composition. At least a photopolymerization initiator capable of initiating a polymerization reaction of the compound and the compound having an ethylenically unsaturated bond, and the content of the compound having the ethylenically unsaturated bond is relative to the whole composition A holographic recording medium, wherein the content is in the range of 1 to 50% by mass, and the photopolymerization initiator contains at least a compound represented by the following general formula (1).

(In the formula, R ₁ , R ₂ and R ₃ each represents an unsubstituted or substituted aryl group, and each may be different or two or more may be the same.)
(Claim 2)
The holographic recording layer further contains a sensitizing dye capable of spectrally sensitizing a photopolymerization initiator capable of initiating a polymerization reaction of a compound having an ethylenically unsaturated bond. 1. The holographic recording medium according to 1.
(Claim 3)
The holographic recording medium according to claim 2, wherein the holographic recording layer further contains a chain transfer agent.
(Claim 4)
The binder-forming compound contained in the holographic recording layer has (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an isocyanate group and a compound having an amino group, and (3) a carbodiimide group. Compound and compound having carboxyl group, (4) Compound having unsaturated ester group and compound having amino group, (5) Compound having unsaturated ester group and compound having mercaptan group, (6) Compound having vinyl group And a compound having a silicon hydride group, (7) a compound having an oxirane group and a compound having a mercaptan group, and (8) oxirane, oxetane, tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, cyclic Selected from Carbonate Holographic recording medium of any one of claims 1 to 3, wherein the at least one selected combination of thermal polymerization initiator and a compound having at least one in the molecule from.
(Claim 5)
The binder-forming compound contained in the holographic recording layer is (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an oxirane group and a mercaptan group, and (3) an oxirane or oxetane. , Tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, and a combination of a compound having one or more groups in the molecule and a thermal acid generator, and a thermal acid generator. The holographic recording medium according to claim 4, wherein the holographic recording medium is provided.
(Claim 6)
The compound having an ethylenically unsaturated bond contained in the holographic recording layer contains at least a compound having a (meth) acryloyl group in the molecule. The holographic recording medium described.
(Claim 7)
The compound having an ethylenically unsaturated bond contained in the holographic recording layer contains 50 to 100% by mass of a compound having a refractive index of at least 1.55 with respect to the whole compound having an ethylenically unsaturated bond. The holographic recording medium according to any one of claims 1 to 6.
(Claim 8)
In the holographic recording medium, when the thickness of the first substrate is D1, the thickness of the second substrate is D2, and the thickness of the holographic recording layer is Dh, 0.15 ≦ Dh / (D1 + D2) ≦ 2. The holographic recording medium according to claim 1, wherein a relationship of 0.0 is satisfied.
(Claim 9)
The holographic recording medium according to claim 8, wherein the holographic recording layer has a thickness Dh of 200 μm or more and 2.0 mm or less.
(Claim 10)
10. The holographic recording medium according to claim 1, wherein in the holographic recording medium, a relationship between a thickness D <b> 1 of the first base material and a thickness D <b> 2 of the second base material satisfies D <b> 1 ≦ D <b> 2. Recording media.
(Claim 11)
11. The holographic recording medium according to claim 1, wherein the first substrate is transparent, and an antireflection treatment is performed on a surface opposite to the surface on which the holographic recording layer is laminated. The holographic recording medium according to claim 1.
(Claim 12)
The holographic recording medium according to claim 1, wherein the material of the first base material is glass.
(Claim 13)
13. The holographic recording medium, wherein a reflective layer having a reflectivity of 70% or more is laminated on the surface of the second substrate on which the holographic recording layer is laminated or on the opposite surface. The holographic recording medium according to any one of the above.
(Claim 14)
The holographic recording medium according to claim 1, wherein the holographic recording medium has a disk shape.
(Claim 15)
The holographic recording medium according to claim 1, wherein the holographic recording medium has a card shape.
(Claim 16)
The holographic recording method for recording on the holographic recording medium according to any one of claims 1 to 15, wherein the binder forming compound is reacted with each other before forming the binder before holographic exposure is performed on the holographic recording medium. Holographic recording is performed by holographic exposure based on the information to be recorded, activating the photopolymerization initiator, and diffusion-polymerizing a compound having an ethylenically unsaturated bond in the holographic recording layer by this active species. A holographic recording method comprising recording information on a medium.
(Claim 17)
17. The holographic recording method according to claim 16, wherein after the information recording on the holographic recording medium is completed, the entire holographic recording medium is further stabilized by heat and light irradiation.
(Claim 18)
The holographic recording method for recording on the holographic recording medium according to any one of claims 1 to 15, wherein holographic exposure based on information to be recorded on the recording medium is performed to activate a photopolymerization initiator. The compound having an ethylenically unsaturated bond is diffusion-polymerized by this active species to record information on the holographic recording medium, and after the information recording on the holographic recording medium is completed, the entire holographic recording medium is further heated. And a holographic recording method comprising stabilizing information recorded by light irradiation.
(Claim 19)
A holographic information recording layer is sandwiched between the first base material and the second base material, and the holographic information recording layer has a region having a low refractive index binder as a main component and a refractive index of 1.55. A holographic information medium comprising a region mainly composed of a radical polymer formed by radical polymerization containing at least a compound having an ethylenically unsaturated bond as a monomer unit.

  According to the present invention, a holographic recording medium, a holographic recording method, and a holographic information medium on which holographic recording has been performed have been obtained.

  Hereinafter, the holographic recording medium, the holographic recording method, and the holographic information medium of the present invention will be described in detail.

  The holographic recording medium of the present invention is a holographic recording medium in which a holographic recording layer is sandwiched between a first substrate and a second substrate, the holographic recording layer comprising a binder-forming compound, an ethylenic compound The composition contains at least a compound having an unsaturated bond and a photopolymerization initiator capable of initiating a polymerization reaction of the compound having an ethylenically unsaturated bond, and the content of the compound having the ethylenically unsaturated bond is a composition. It is the range of 1-50 mass% with respect to the whole, and this photoinitiator contains the compound represented by the said General formula (1) at least. The binder-forming compound mentioned here refers to a precursor that is not a polymer as a binder at the time of producing a recording composition, and by using such a binder-forming compound, holographic exposure described in detail later. It is possible to prevent the front and rear recording media from shrinking and to increase the thickness of the recording layer when producing the holographic recording media.

  The compound represented by the general formula (1) added as an essential component of the present invention may have 0 to 4 substituents, and examples of these substituents include a halogen atom, a cyano group, and an alkyl group. , Alkenyl group, alkoxy group, alkylsulfonamide group, aryloxy group, arylthio group, arylsulfonamide group, anilino group, acylamino group, alkylureido group, arylureido group, alkylcarbonyl group, alkoxycarbonyl group, alkoxycarbonylamino group , Carbamoyl group, sulfamoyl group, sulfo group, carboxy group, aryl group or heterocyclic group.

  Specific examples of such a general formula (1) include 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2 '-Bis (o-chlorophenyl) -4,4', 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5' Tetrakis (3,4,5-trimethoxyphenyl) biimidazole, 2,2'-bis (o-bromophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'- Bis (p-bromophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-carboxyphenyl) -4,4', 5,5'-tetraphenylbiimidazo -2,2,2'-bis (p-she Nophenyl) -4,4 ', 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-bis (2,4-dichlorophenyl) -4,4', 5,5'-tetraphenylbi Imidazole, 2,2'-bis (2,4-dimethoxyphenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-fluorophenyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (m-fluorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-fluorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-hexylphenyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (O-hexylf Nyl) -4,4 ', 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-bis (3,4-methylenedioxyphenyl-chlorophenyl) -4,4', 5,5 '-Tetraphenylbiimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetrakis [m- (betaphenoxy-ethoxyphenyl)] biimidazole, 2,2'-bis (2,6-dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-methoxyphenyl) -4,4', 5,5'-tetraphenylbiimidazole 2,2'-bis (p-methoxyphenyl) -4,4'-bis (o-methoxyphenyl) -5,5'-diphenylbiimidazole, 2,2'-bis (o-nitrophenyl) -4 , 4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-phenylsulfonylphenyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis ( p-sulfamoylphenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (2,4,6-trimethylphenyl) -4,4', 5,5'- Tetraphenylbiimidazole, 2,2'-bis (4-biphenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (1-naphthyl) -4,4', 5 , 5'-tetraphenylbiimidazole, 2,2'-bis (1-naphthyl) -4,4 ', 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-bis (9- Phenanthryl) -4,4 ' 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-diphenyl-4,4 ', 5,5'-tetrakis (4-biphenyl) biimidazole, 2,2'-diphenyl-4, 4 ', 5,5'-tetrakis (2,4-xylyl) biimidazole, 2,2'-bis (3-pyridyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2 ' -Bis (3-thienyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-tolyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-tolyl) -4,4'-bis (o-tolyl) -5,5'-tetraphenylbiimidazole, 2,2'-bis (2,4-xylyl)- 4,4 ', 5,5'-tetraphenylbiimidazole 2,2 ′, 4,4 ′, 5,5′-hexakis (p-benzylthiophenyl) biimidazole, 2,2 ′, 4,4 ′, 5,5′-hexa (1-naphthyl) biimidazole, 2,2 ', 4,4', 5,5'-hexaphenylbiimidazole, 2,2'-bis (2-nitro-5-methoxyphenyl) -4,4 ', 5,5'-tetraphenylbiimidazole Imidazole, 2,2'-bis (o-nitrophenyl) -4,4 ', 5,5'-tetrakis (m-methoxyphenyl) biimidazole, 2,2'-bis (2-chloro-5-sulfo) Phenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole and the like, and “Photoinitiators or Free-Radical-Initiated Photoimaging Sys”. ems ", Chem. Rev. , 93, p. 435-448 (1993), S.A. P. P. Of Papas, “Radiation Curing: Science and Technology, Plenum Press, New York, (1992)”. Compounds described in 407 to 412 and the like can also be selected and used as appropriate.

  The photopolymerization initiator for photopolymerizing the compound having an ethylenically unsaturated bond according to the present invention includes, in addition to the compound represented by the general formula (1) described in detail above, benzoin and its conventionally known compounds. Derivatives, carbonyl compounds such as benzophenone, azo compounds such as azobisisobutyronitrile, sulfur compounds such as dibenzothiazolyl sulfide, peroxides such as benzoyl peroxide, halides such as 2-tribromomethanesulfonyl-pyridine In addition, photoinitiators such as quaternary ammonium salts or onium compounds such as substituted or unsubstituted diphenyliodonium salts and triphenylsulfonium salts, and metal π complexes such as iron arene complexes and titanocene complexes may be used in combination. For the exposure light source wavelength used for holographic exposure described in If there is little or no absorption with respect to the wavelength of the laser light source used for holographic exposure of the photopolymerization initiator, the spectral wavelength of the photopolymerization initiator is wavelength-sensitized if there is very little. It is more preferable to use a sensitizing dye together.

  Examples of the sensitizing dye for sensitizing the spectral wavelength of the photopolymerization initiator used here include various dyes used in the art, such as carbonyl derivatives such as Michler's ketone, coumarin derivatives, and methine. Derivatives, polymethine derivatives, triarylmethane derivatives, indoline derivatives, azine derivatives, thiazine derivatives, xanthene derivatives, thioxanthene derivatives, oxazine derivatives, acridine derivatives, cyanine derivatives, carbocyanine derivatives, merocyanine derivatives, hemicyanine derivatives, rhodocyanine derivatives, azamethine Derivatives, styryl derivatives, pyrylium derivatives, thiopyrylium derivatives, porphyrazine derivatives, porphyrin derivatives, phthalocyanine derivatives, pyromethene derivatives and 2,5-thiofezyl (5-t-butyl-1) 3-benzoxazole) various dyes such as optical brightening agents, such as if individually or required may be used in combination of two or more.

  Specific examples of such photopolymerization initiators or sensitizing dyes include, for example, U.S. Pat. Nos. 5,027,436, 5,096,790, 5,147,758, and 5,204. No. 467, No. 5,256,520, No. 6,011,180, European Patent Nos. 255,486, 256,981, No. 277,915, No. 318,893, No. 401,165 Nos. 565,488, 1,349,006, JP-A-2-236553, 5-46061, 5-216227, 5-247110, 5-257279, 6- 175554, 6-175562, 6-175563, 6-175656, 6-186899, 6-195015, 6-202540, 6-202541, 6-2 2543, 6-202544, 6-202548, 6-324615, 6-329654, 7-13473, 7-28379, 7-84502, 7-84503 7-181876, 9-106069, 9-309907, JP-A-2002-60429, 2002-62786, 2002-244535, 2002-296664, and the like. Can be selected and used at the appropriate time.

  The photopolymerization initiator for photopolymerizing the above-mentioned compound having an ethylenically unsaturated bond is generally determined by the molecular weight of the photopolymerization initiator and the proportion of the ethylenically unsaturated bond in the compound having an ethylenically unsaturated bond. However, it is usually preferable to use in the range of 0.01 to 25 parts by mass with respect to the compound having an ethylenically unsaturated bond. A sensitizing dye capable of spectrally sensitizing a photopolymerization initiator cannot be generally defined by the molecular weight or molar extinction coefficient of the dye itself, but is usually 0.1 to 25 with respect to the photopolymerization initiator. It is preferable to use in the range of parts by mass.

  Furthermore, in the present invention, it is preferable to add a chain transfer agent in order to more efficiently use the radical generated from the compound represented by the general formula (1) for the polymerization of the compound having an ethylenically unsaturated bond, Examples of such chain transfer agents include N-arylglycines such as N-phenylglycine, julolidines such as Michler's ketone, leucocrystal violet and other aminotriarylmethane leuco dyes, 2,6-diisopropyl-N N, N-dialkylamino aromatics such as N, N-dimethylaniline (alkyl groups are independently C1-C6 alkyl), boron salts such as tetrabutylammonium triphenylbutyl boron salt, 4-acetamidothiophenol, mercaptosucci Acid, dodecanethiol, beta-mercapto Organic thiols such as tanol, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole and 2-mercaptobenzothiazole, 1,1-dimethyl-3,5-diketocyclohexane, and the like. As addition amount, it is preferable to use normally in the range of 10-200 mass parts with respect to a photoinitiator.

  As the compound having an ethylenically unsaturated bond in the molecule used in the present invention, a compound having an ethylenically unsaturated bond, for example, a styrene derivative, a compound having an allyl group, an unsaturated olefin, or the like does not impair the object of the present invention. Can be used without any particular limitation, but in consideration of adhesion to the substrate when used as a recording medium and compatibility with a binder-forming compound, a compound having an acyloxy group or acylamide group in the molecule is preferred. Further, a compound having a (meth) acryloyl group is more preferable from the viewpoint of steric hindrance during radical polymerization. In addition, the (meth) acryloyl group said by this invention represents an acryloyl group or a methacryloyl group.

  In the present invention, for the binder formed from the above-mentioned binder-forming compound, in order to more significantly have a refractive index difference from a polymer of a compound having an ethylenically unsaturated bond obtained by diffusion polymerization, It is preferable to use a higher or lower refractive index than the binder-forming compound as the compound having an ethylenically unsaturated bond. In particular, it is preferable to use a compound having a refractive index of 1.55 or more as the compound having an ethylenically unsaturated bond because a polymer of a compound having an ethylenically unsaturated bond having a high refractive index is obtained. As the compound, it is preferable to use a compound having a refractive index of around 1.50.

  As such a compound having a (meth) acryloyl group having a refractive index of 1.55 or more, generally a hetero atom such as nitrogen, oxygen, sulfur and phosphorus, a halogen atom such as chlorine, bromine and iodine in the molecule, or Examples of the compound having two or more aromatic rings include paracumylphenoxyethylene glycol acrylate, paracumylphenoxyethylene glycol methacrylate, hydroxyethylated o-phenylphenol acrylate, and hydroxyethyl. Β-naphthol acrylate, tribromomophenyl acrylate, tribromophenyl methacrylate, triiodophenyl methacrylate, polyethylene oxide modified tetrabromobisphenol A diacrylate, polyethylene oxa Modified tetrabromobisphenol A dimethacrylate, bis (4-methacryloylthiophenyl) sulfide, compounds having a fluorene skeleton described in JP-A-6-301322, JP-A-2000-344716, JP-A-2003-29604, etc. Can be mentioned.

  Further, when preparing a holographic recording layer composition within a range that does not hinder the purpose of providing a refractive index difference between a binder formed from a binder-forming compound and a diffusion polymer of a compound having an ethylenically unsaturated bond. In order to adjust the compatibility, viscosity, and control diffusion polymerization during holographic exposure, a compound having a (meth) acryloyl group having a refractive index of less than 1.55 may be added. Examples of the compound having a (meth) acryloyl group include, for example, a compound having one (meth) acryloyl group, substituted or unsubstituted phenol, (meth) acrylates of nonylphenol and 2-ethylhexanol, and alkylenes of these alcohols. Examples thereof include (meth) acrylates of oxide adducts. Examples of compounds having two (meth) acryloyl groups include di (meth) acrylates of substituted or unsubstituted bisphenol A, bisphenol F, fluorene and isocyanuric acid, and alkylene oxide adducts of these alcohols, Examples include di (meth) acrylates of polyalkylene glycols such as ethylene glycol and propylene glycol. Compounds having three (meth) acryloyl groups include tri (meth) acrylates of pentaerythritol, trimethylolpropane and isocyanuric acid, and tri (meth) acrylates of alkylene oxide adducts of these alcohols. ) Examples of the compound having 4 or more acryloyl groups include pentaerythritol, poly (meth) acrylate of dipentaerythritol, and the like. Also, conventionally known (meth) acryloyl group-containing monomers / oligomers such as urethane acrylate having a urethane bond as the main chain and polyester acrylate having an ester bond as the main chain can be selected and used in a timely manner. .

  In addition, the compound having an ethylenically unsaturated bond in the molecule described above may be used alone or in combination of two or more, and usually 1.0% by mass or more in the composition for holographic recording. 50 mass% or less, and more preferably 4.0 mass% or more and 40 mass% or less.

  The binder-forming compound of the present invention does not polymerize or crosslink between the binder-forming compounds when preparing a holographic recording composition, and is polymerized or cross-linked into a binder when preparing a holographic recording medium described below. It is characterized by that. Thus, examples of the binder-forming compound include (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an isocyanate group and a compound having an amino group, and (3) a compound having a carbodiimide group and a carboxyl group. (4) a compound having an unsaturated ester group and a compound having an amino group, (5) a compound having an unsaturated ester group and a compound having a mercaptan group, (6) a compound having a vinyl group and a silicon hydride group (8) a compound having an oxirane group and a mercaptan group, and (8) an oxirane, oxetane, tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, cyclic carbonate Group in the molecule A combination of at least one compound and a thermal acid generator, at least one selected from the above eight types can be selected and used as appropriate, and further, the binder is polymerized or cross-linked under mild conditions. (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an oxirane group and a compound having a mercaptan group, and (3) oxirane, oxetane, tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal More preferred is a combination of at least one selected from a compound having at least one group selected from lactone, cyclic orthoester and cyclic carbonate in the molecule and a thermal acid generator.

  The compound having an isocyanate group used in the case of crosslinking the compound having an isocyanate group and the compound having a hydroxyl group used in the present invention can be used without particular limitation, but is a photopolymerization component detailed above. In order to sufficiently retain the compound having a polymerizable unsaturated bond after the production of the holographic recording medium, a compound having two or more isocyanate groups in the molecule is more preferable. Examples include 1,8-diisocyanate-4-isocyanatomethyl-octane, 2-isocyanatoethyl-2,6-diisocyanate caproate, benzene-1,3,5-triisocyanate, 1-methylbenzene-2, 4,6-triisocyanate, 1,3,5-to Methylbenzene-2,4,6-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, triphenylmethane-4,4 ', 4 "-triisocyanate, bis (isocyanatotolyl) phenylmethane, dimethylene Diisocyanate, tetramethylene diisocyanate, hexanemethylene diisocyanate, 2,2′-dimethylpentane diisocyanate, 2,2 ′, 4-trimethylpentane diisocyanate, decane diisocyanate, ω, ω′-diisocyanate-1,3-dimethylbenzene, ω , Ω′-diisocyanate-1,2-dimethylcyclohexane diisocyanate, ω, ω-diisocyanate-1,4-diethylbenzene, isophorone diisocyanate, 1-methylcyclohexyl-2,4-diisocyanate Ω, ω′-diisocyanate-1,5-dimethylnaphthalene, ω, ω′-diisocyanate-n-propylbiphenyl, 1,3-phenylene diisocyanate, 1-methylbenzene-2,4-diisocyanate, 1,3- Dimethylbenzene-2,6-diisocyanate, naphthalene-1,4-diisocyanate, 1,1'-dinaphthyl-2,2'-diisocyanate, biphenyl-2,4'-diisocyanate, 3,3'-dimethylbiphenyl-4, 4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, 2,2'-dimethyldiphenylmethane-4,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4 '-Diisocyanate, 4,4' Examples include diethoxydiphenylmethane-4,4'-diisocyanate, tolylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, tetramethylene xylylene diisocyanate, and the like. Body adducts (for example, 2 moles of hexamethylene diisocyanate, 3 moles of hexamethylene diisocyanate, 2 moles of 2,4-tolylene diisocyanate, 3 moles of 2,4-tolylene diisocyanate, etc.) Adducts of two or more different isocyanates selected from the above isocyanates, and these isocyanates and dihydric or trihydric polyalcohols (for example, diethylene glycol, polyethylene) Adducts (eg, adducts of tolylene diisocyanate and trimethylol propane, adducts of hexamethylene diisocyanate and trimethylol propane, etc.) and the like. It is done. In addition, you may use these isocyanate compounds individually by 1 type or in combination of 2 or more types.

  In the above-described isocyanate compound, all information is recorded on a holographic recording medium in which a recording layer composed of a holographic recording composition described in detail later is laminated, and the holographic information used in a state where the recording is completed. As with CDs and DVs, the media may have a variety of ambient temperatures under fluorescent lamps, windows, or left. Accordingly, those which suppress the coloring of the recording layer under various conditions are preferable, and in order to suppress the coloring as described above, an aliphatic isocyanate compound is more preferable among the above-mentioned compounds.

  In the present invention, the binder may be formed by self-crosslinking of the compound having an isocyanate group, which is an essential component described above. However, in order to perform binder formation under mild conditions, It is preferable to form a binder by a crosslinking reaction with a compound having a functional group that reacts with an isocyanate group in the molecule. Examples of the compound capable of reacting with such an isocyanate compound include a compound having a hydroxyl group in the molecule, primary or secondary compound. Examples thereof include a compound having a secondary amino group and a compound having an enamine structure. However, in order to record all information on a holographic recording medium in which a recording layer composed of a holographic recording composition described in detail later is laminated, and to suppress coloring of the holographic information medium used in the state where the recording is completed. Among these compounds, a compound having a hydroxyl group is preferable as a compound capable of reacting with an isocyanate compound, and a compound having two or more aliphatic alcoholic hydroxyl groups in the molecule is more preferable.

  Examples of the compound having two or more alcoholic hydroxyl groups in the molecule include, for example, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 2,2-dimethyl-1,3-propane. Diol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-butanediol, 1,4-butanediol, polytetramethylene glycol, 1 , 5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 2,5- Dimethyl-2,5-hexanediol, 1,10-decandio , 1,4-cyclohexanediol, glycerin, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc., and two alcoholic hydroxyl groups in the molecule Examples thereof include alcohols modified with divalent alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, these compounds having two or more alcoholic hydroxyl groups in the molecule may be used alone or in combination of two or more.

  In addition, the molecular weight of a compound having two or more aliphatic alcoholic hydroxyl groups in the molecule is the compound itself having volatility, a compound having an ethylenically unsaturated bond, a compound having a cationically polymerizable functional group, or photopolymerization. In consideration of the compatibility and solubility with the initiator, it is usually preferable that the molecular weight is 100 or more and 2,000 or less, and the addition amount of the compound having two or more aliphatic alcoholic hydroxyl groups in the molecule is as follows. The number of moles of isocyanate groups in the composition for holographic recording possessed by the compound having an isocyanate group is N [mol], although it cannot be generally defined by the type and amount of the isocyanate compound that is the essential component described above. The number of moles of hydroxyl group in the composition for holographic recording of the alcoholic hydroxyl group is defined as M [mol]. In a usually 0.5 ≦ N / M ≦ 2.0, more preferably more preferable from the viewpoint of the control of the compatibility or cross-linking reaction to the range of 0.7 ≦ N / M ≦ 1.5.

  In addition, as a compound having an oxirane group or a compound having a mercaptan group used in the case of forming a binder by polymerizing a compound having an oxirane group and a compound having a mercaptan group, a known crosslinkable compound is particularly used. Although it can be used without limitation, when producing the holographic recording medium of the present invention, which will be described in detail later, two recording compositions that are liquid at room temperature or liquid at a temperature of 100 ° C. or lower are used. Since it is produced by sandwiching between materials at a predetermined thickness, a compound that is liquid at normal temperature or has a melting point of 100 ° C. is preferable, and a compound having two or more oxirane groups or mercaptan groups is more preferable.

  Specific compounds having the above oxirane group include aliphatic polyglycidyl ether, polyalkylene glycol diglycidyl ether, tertiary carboxylic acid monoglycidyl ether, polycondensate of bisphenol A and epichlorohydrin, hydrogenated bisphenol A and epichlorohydrin, A polycondensate of bisphenol A and epichlorohydrin, a polycondensate of bisphenol F and epichlorohydrin, etc., a terminal-modified resin with a glycidyl group, a glycidyl-modified phenol novolak resin, a glycidyl-modified o-cresol novolak And the like. Furthermore, compounds described in “11290 Chemical Products”, Chemical Industry Daily, pages 778 to 787 can also be suitably used. Such compounds having an oxirane group in the molecule It may be used in combination of two or more as necessary.

  Examples of the compound having a mercaptan group include thioglycolic acid, ammonium thioglycolate, monoethanolamine thioglycolate, sodium thioglycolate, methyl thioglycolate, octyl thioglycolate, methoxybutyl thioglycolate, and butane. Diol bisthioglycolate, ethylene glycol bisthioglycolate, trimethylolpropane tristhioglycolate, pentaerythritol tetrakisthioglycolate, 3-mercaptopropionic acid, methyl mercaptopropionate, octyl mercaptopropionate, methoxybutyl mercaptopropionate, Tridecyl mercaptopropionate, butanediol bisthiopropionate, ethylene glycol bisthiopropionate, trimethylo Le propane tris thiopropionate, pentaerythritol tetrakis thiopropionate, esters of polyhydric alcohols and mercaptopropionic acids such as dipentaerythritol and trimethylol propane. These thiol-containing compounds may be used alone or in combination of two or more.

  Further, when a binder is formed by polymerizing a compound having an oxirane group and a compound having a mercaptan group, it is preferable to contain a Bronsted base or a Lewis base in order to polymerize under a milder condition. Examples of the base include amine compounds such as pyridine, piperidine, dimethylaniline, 2,4,6-tris (dimethylaminomethyl) benzene, and 2,4,6-tris (dimethylaminomethyl) phenol.

  Further, when a compound having at least one group selected from oxirane, oxetane, tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, and cyclic carbonate is crosslinked with a thermal acid generator. The compound to be used can be used without particular limitation as long as it has the above-mentioned functional group, but when producing the holographic recording medium of the present invention described later in detail, it is liquid at room temperature or 100 ° C. or less. Since a liquid recording composition is sandwiched between two substrates at a predetermined thickness at a predetermined temperature, a compound having a liquid state or a melting point of 100 ° C. at room temperature is preferred, and under mild conditions. A compound having an oxirane or oxetane group in the molecule that can be polymerized or crosslinked into a binder. Preferably, the compound having an oxirane group, a compound used for forming a compound by polymerizing a binder with a compound having a mercaptan group having an oxirane group as described above may be used by appropriately selected.

  In addition, in the above-described compound having an oxirane or oxetane group in the molecule, it is preferable to include a compound having at least one oxetane group in the molecule when the binder formed after polymerization is to have a high molecular weight. Specific examples of the compound having an oxetane group in the molecule include, for example, JP-A Nos. 5-170763, 5-371224, 6-16804, 7-17958, 7-173279, 8-245783, 8-301859, 10-237056, 10-330485, 11-106380, 11-130766, 11-228558, 11-246510, 11- 246540, 11-246541, 11-322735, JP-A-2000- No. 482, No. 2000-26546, No. 2000-191652, No. 2000-302774, No. 2000-336133, No. 2001-31664, No. 2001-31665, No. 2001-31666, No. 2001-163882. 2001-226365, 2001-278874, 2001-278875, 2001-302651, 2001-342194, 2002-20376, 2002-80581, 2002-193965, 2002-241489, 2002-275171, 2002-275172, 2002-322268, 2003-2881, 2003-12626, 2003-81958, JP-A-11-50042, etc. Can be exemplified compounds described, these compounds may be used in combination either alone or two or more kinds.

  As the thermal polymerization initiator capable of crosslinking the above-mentioned compound having an oxirane or oxetane group in the molecule, any known sulfonium salt, ammonium can be used as long as it does not adversely affect other essential components of the present invention. Salts, onium salts such as phosphonium salts and silanol / aluminum complexes can be used without any particular limitation. Among these thermal polymerization initiators, there is no problem even if other essential components are heated to 150 ° C or higher. For example, benzylsulfonium salts described in JP-A-58-37003, JP-A-63-22002, etc., trialkylsulfonium salts described in JP-A-56-152833, etc. are appropriately selected and used. Can do.

  In addition, when the photopolymerization initiator loses its activity when heated at a high temperature or generates a radical when heated at a high temperature, the thermal polymerization initiator should be a compound that can start polymerization at a low temperature. Specific examples of such compounds are disclosed in JP-A-63-8365, JP-A-63-8366, JP-A-1-83060, JP-A-1-290658, JP-A-2-1470 and JP-A-2. -196812, 2-232253, 3-17101, 3-47164, 3-48654, 3-14559, 3-2000076, 3-237107, 4-1177 No. 4-210673, No. 8-188869, No. 8-188570, No. 11-29609, No. 11-255539, JP-A-2001-55374, etc. It can include compounds that have been mounting, such thermal polymerization initiators may be used in combination and use of two or more thereof, if alone or necessary.

  The thermal polymerization initiator described in detail above can use a carbonium cation generated by thermal cleavage of the initiator itself for initiating polymerization of a compound having an oxirane or oxetane group in the molecule. When a compound having a proton-donating functional group such as a hydroxyl group is present in the recording composition, a carbonium cation generated by cleavage reacts with a compound having a proton-donating functional group to generate protons generated. It can also be used as a polymerization initiator for a compound having an oxirane or oxetane group in the molecule.

  The amount of the thermal polymerization initiator described above is usually in the range of 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the compound having an oxirane or oxetane group capable of cationic polymerization described later in the molecule. Preferably, it is the range of 0.1 mass part or more and 5 mass parts or less.

  Next, the 1st base material and the 2nd base material which comprise a recording medium are demonstrated. The first base material here refers to a base material on the side on which information light and reference light are incident or a reproduction light for reproduction when performing holographic exposure for recording information on a recording medium. It is a substrate on the irradiation side, and the second substrate refers to a substrate opposite to the first substrate with the holographic recording layer interposed therebetween.

  The first base material and the second base material used in the recording medium of the present invention are transparent and do not cause expansion and contraction or bending at the use environment temperature, and are inactive to the recording composition described above. Any material can be used without particular limitation. Examples of such a substrate include quartz glass, soda glass, potash glass, lead crystal glass, borosilicate glass, aluminosilicate glass, titanium crystal glass, and crystallized glass. List various resins such as glass, polycarbonate, polyacetal, polyarylate, polyetheretherketone, polysulfone and polyethersulfone, polyimide such as polyimide-amide and polyetherimide, polyamide, and polyolefin such as cyclic olefin ring-opening polymer Can do.

  Among the above-mentioned base materials, information light and reference light are incident from the viewpoints of thickness variation with respect to environmental temperature and humidity during holographic exposure, gas permeability, and light transmittance of the light source wavelength used during holographic exposure. It is more preferable to use glass as the material of the first base material on the side to be used. The second substrate is preferably made of glass like the first substrate. However, if the device is provided with a focus correction mechanism when reading holographically recorded information with a CCD, the stretch rate and thickness It may be a base material made of resin instead of a base material such as glass with suppressed fluctuations.

Further, the transmittance of the incident light of the first base material on the side on which the information light and the reference light are incident is preferably 70% or more, and more than 80% has little loss of light reaching the holographic recording layer. To more preferable. In order to increase the transmittance as much as possible, it is preferable that the first base material surface opposite to the surface on which the holographic recording layer is laminated is subjected to an antireflection treatment. The refractive index is not particularly limited as long as the refractive index is lower than that of the first substrate. For example, inorganic metal fluorides such as AlF ₃ , MgF ₂ , AlF ₃ .MgF ₂ , CaF ₂ , vinylidene fluoride, Teflon (R), etc. Organic fluorides such as homopolymers, copolymers, graft polymers, block polymers containing fluorine atoms, modified polymers modified with functional groups containing fluorine atoms, etc. than those detailed above as substrates It is preferable because the refractive index is lowered.

  In addition, as a method of providing a layer made of a fluorine-based compound on a substrate, it cannot be determined in general depending on the type of the support or the fluorine-based compound, but a sol-gel method, a vacuum deposition method, a sputtering method, a CVD, A known method such as a coating method or a coating method, or a method described in JP-A-7-27902, JP-A-2001-123264, JP-A-2001-264509, or the like can be appropriately selected and used.

  Such an antireflection layer cannot be generally defined by the surface treatment or material of the substrate, but is usually in the range of 0.001 to 20 μm, preferably in the range of 0.005 to 10 μm.

  Further, for a recording medium used in a holographic recording / reproducing apparatus such as Japanese Patent Application Laid-Open No. 2002-123949 and International Publication No. 99/57719, a surface on which a second holographic recording layer is laminated. Alternatively, it is preferable that a reflective layer is provided on the opposite surface, and when the reflective layer is provided in this way, the reflectance is preferably 70% or more with respect to the wavelength of light to be reflected, and more preferably 80% or more. More preferably.

  Such a reflective layer is not particularly limited in material as long as a desired reflectance is obtained, but can be laminated by providing a thin film of metal or the like on the substrate surface. For example, in order to form such a reflective layer, it can be laminated as a metal thin film, a metal single crystal or a polycrystal by a known method such as a vacuum deposition method, an ion plating method, or a sputtering method. The metals used for laminating aluminum, zinc, antimony, indium, selenium, tin, tantalum, chromium, lead, gold, silver, platinum, nickel, niobium, germanium, silicon, molybdenum, manganese, tungsten, palladium These metals can be formed singly or in combination of two or more. The thickness of the metal thin film layer may be any thickness as long as the desired reflectance can be obtained, but is usually in the range of 1 to 3000 nm, and preferably in the range of 5 to 2000 nm.

  On the other hand, in a holographic recording medium, a recording medium having a high storage capacity can be produced by making the holographic recording layer as thick as possible. However, the use environment of the recording medium, reading error of recorded information, etc. In consideration of this, in the present invention, when the thickness of the first substrate is D1, the thickness of the second substrate is D2, and the thickness of the holographic recording layer is Dh, 0.15 ≦ Dh / (D1 + D2 ) ≦ 2.0 is preferably satisfied.

  Here, if 0.15> Dh / (D1 + D2), the film thickness of the holographic recording layer cannot be increased, or even if the film thickness of the recording layer is increased, the thickness of the base material is increased, and the entire recording medium is increased. turn into. This is not preferable because the mass of the recording medium alone is heavy and a load on the drive system of the apparatus may occur. Further, when Dh / (D1 + D2)> 2.0, it is possible to reduce the thickness of the recording medium while ensuring the thickness of the recording layer. Thickness increases, surface accuracy of the recording media, unevenness of the recording layer at the operating environment temperature, variation of the recording layer thickness when unexpected stress is applied, and further, the first base material and the second base material Is not preferable because it may shift.

  Further, in terms of energy loss during holographic exposure, the relationship between the thickness D1 of the first base material and the thickness D2 of the second base material is preferably D1 ≦ D2, and the flatness of the recording medium is ensured. Therefore, it is more preferable that the thickness ratio of D1 and D2 is in the range of 0.20 ≦ D1 / D2 ≦ 1.00.

  Further, the thickness Dh of the holographic recording layer is not generally determined by the diffraction efficiency, dynamic range, spatial resolution, etc. of the recording layer, but is usually preferably 200 μm or more and 2.0 mm or less. When a recording medium having a capacity cannot be obtained and is thicker than 2.0 mm, it is not preferable because unevenness in the thickness of the recording layer may occur at the surface accuracy of the recording medium and the use environment temperature.

  On the other hand, the shape of the recording medium is not particularly limited as long as it is suitable for the holographic recording / reproducing apparatus used for the recording medium. For example, US Pat. No. 5,719,691, JP-A-2002-123949 If it is used for the apparatus described in No. etc., the disk-shaped thing is preferable, and if the apparatus described in the international publication 99/57719 etc. is used, a card-like thing is preferable.

  As a method for producing the recording medium described in detail above, a holographic recording layer forming composition is prepared by mixing the holographic recording composition by heating at room temperature or as necessary under a safelight. , After deaeration to suppress polymerization inhibition during holographic exposure, a holographic recording layer forming composition heated to room temperature or as necessary is applied on the first substrate, and then the second substrate Can be manufactured by sealing the end portion after the pasting so that bubbles do not enter so as to have a predetermined recording layer thickness. In addition, the first base material and the second base material are fixed to a mold under a safelight so as to have a predetermined gap, and bubbles do not enter the holographic recording composition heated at room temperature or as necessary. Thus, it is possible to produce a recording medium by filling between the first base material and the second base material by injection molding or suctioning under reduced pressure so that bubbles do not enter, and finally sealing the end portion. . The term “under safe light” as used herein refers to an operation in a state in which the wavelength of light at which the photopolymerization initiator becomes active is cut.

  Further, when producing a recording medium by bonding, the holographic recording layer forming composition may be applied not on the first base material described above but on the second base material. You may attach to both of a 2nd base material. Furthermore, when sealing the edge part of a 1st base material, a holographic recording layer, and a 2nd base material, the liquid sealing material represented by the moisture hardening type adhesive which can be sealed May be cross-linked and sealed, or the holographic recording layer may be sealed in advance using an end sealing material on a ring for ensuring a predetermined film thickness.

  Next, a method for recording information on the holographic recording medium will be described in detail.

  In the first aspect of the holographic recording method of the present invention, a holographic recording layer is sandwiched between a first substrate and a second substrate, and the holographic recording layer is a binder-forming compound, an ethylenic compound. A compound having an unsaturated bond, at least a photopolymerization initiator capable of initiating a polymerization reaction of the compound having an ethylenically unsaturated bond, and the content of the compound having an ethylenically unsaturated bond being the entire composition And a photopolymerization initiator capable of initiating a polymerization reaction of the compound having an ethylenically unsaturated bond is at least a compound represented by the general formula (1). In a method for holographic recording on a holographic recording medium in which a recording layer is laminated, a binder formation compound is formed before holographic exposure. After reacting each other to form a binder, holographic exposure based on the information to be recorded is performed, the photopolymerization initiator is activated, and the compound having an ethylenically unsaturated bond is activated by this active species. It is characterized by recording information on a holographic recording medium by diffusion polymerization inside.

  In general, when a thick film layer is attached, a recording layer forming composition is prepared without a solvent for dilution. For a solid or high-viscosity composition, a uniform film thickness is obtained or air bubbles are involved during preparation of the composition. Removal becomes difficult. Therefore, fluidity is required at normal temperature or in a heated state when the recording layer forming composition is prepared. When this recording layer forming composition is liquid at room temperature and has a low viscosity, it is difficult to ensure flatness as a recording medium, or the ethylenically unsaturated bond after information is recorded by holographic exposure. It is not preferable because the polymer formed by the compound having the above may be displaced in the recording layer.

  Therefore, the holographic recording medium containing the above-mentioned essential components is made into a binder by crosslinking a binder-forming compound before holographic exposure, and an ethylenically unsaturated bond is formed at the time of ensuring flatness and holographic exposure. It is possible to prevent movement of the polymer formed by diffusion polymerization of the compound having the compound in the holographic recording layer.

  After the binder is formed as described above, holographic exposure based on the information to be recorded is performed to activate the photopolymerization initiator, and the compound having a compound having an ethylenically unsaturated bond by this active species Information can be recorded on a holographic recording medium by diffusion polymerization.

  The crosslinking reaction for forming the binder in this recording method may be performed by crosslinking all combinations of functional groups that can be reacted, or may be partially crosslinked within a range that does not cause any practical problems. Furthermore, after information is recorded on the holographic recording medium, the ethylenically unsaturated bond remaining in the recording layer by light and heat applied as necessary for the purpose of fixing the recorded holographic information. It is preferable to photopolymerize a compound having a photopolymerization initiator with a photopolymerization initiator and to thermally crosslink uncrosslinked functional groups of the remaining binder-forming compound. In this case, it is preferable that the light used for exposure is exposed all over the recording medium. When heating is performed, the exposure may be performed before the batch exposure, at the same time as the batch exposure, or after the batch exposure. You may combine.

  In the second aspect of the holographic recording method of the present invention, a holographic recording layer is sandwiched between a first substrate and a second substrate, and the holographic recording layer is a binder-forming compound, an ethylenic compound. A compound having an unsaturated bond, at least a photopolymerization initiator capable of initiating a polymerization reaction of the compound having an ethylenically unsaturated bond, and the content of the compound having an ethylenically unsaturated bond being the entire composition And a photopolymerization initiator capable of initiating a polymerization reaction of the compound having an ethylenically unsaturated bond is at least a compound represented by the general formula (1). Holographic exposure based on information to be recorded in a method for holographic recording on a holographic recording medium having a recording layer containing The information was recorded on the holographic recording medium by activating the photopolymerization initiator and diffusion polymerizing the compound having an ethylenically unsaturated bond with this active species, and the information recording on the holographic recording medium was completed. Later, the recorded information is further stabilized by applying heat and light to the entire holographic recording medium.

  Unlike the first embodiment described above, this embodiment is a composition that flows in a heated state but does not flow at room temperature when a recording layer forming composition is prepared, or a gel at room temperature unless shear stress is applied. Or a holographic recording medium in which a recording layer is formed by a recording layer forming composition having thixotropic properties.

  In such a recording medium, the level of the recording medium should be at a level that does not cause any practical problem with respect to ensuring the flatness of the recording medium and preventing migration of a polymer formed by diffusion polymerization of a compound having an ethylenically unsaturated bond. In order to further improve the storage stability of recorded information, a compound having an ethylenically unsaturated bond remaining in the recording layer by light and heat after recording information on the holographic recording medium can be obtained. It is preferable that the photopolymerization initiator and the uncrosslinked functional groups of the remaining binder-forming compound are thermally crosslinked. In this case, as in the first aspect described above, it is preferable that the light used for exposure is exposed all over the recording medium, and when the recording medium is heated, either before the batch exposure, simultaneously with the batch exposure or after the batch exposure. It may be present or some heat treatments may be combined.

  In addition, as an apparatus for recording / reproducing holographic recording media used in the recording methods of the first and second aspects of the present invention, any apparatus capable of recording / reproducing with respect to the recording medium of the present invention can be used. There are no limitations, and examples of such recording / reproducing apparatuses include US Pat. Nos. 5,719,691, 5,838,467, 6,163,391, 6,414,296, US Publication No. 2002-136143, JP-A-9-305978, JP-A-10-124872, JP-A-11-219540, JP-A-2000-98862, JP-A-2000-2988837, JP-A-2001-23169, JP-A-2002-83431. No., No. 2002-123949, No. 2002-123948, No. 2003-43904, International Publication No. 99/57719, No. 02/05270, it may be mentioned those described in the 02/75727 Patent like.

  As a light source as a laser used in the recording / reproducing apparatus described above, a laser light source capable of holographic recording by activating a photopolymerization initiator in a recording medium and reading a recorded hologram can be used. The light source can be used without limitation, such as blue-violet semiconductor laser, argon laser, He-Cd laser, double-frequency YAG laser, He-Ne laser, Kr laser, near-infrared semiconductor laser, etc. Can be mentioned.

  In addition, a holographic recording medium before recording and a holographic recording medium with a small amount of recorded information that may be additionally recorded are (λ + 100) nm or less when the wavelength of a light source usually used for holographic recording is λ nm. Preferably, it is stored and placed in a case or cassette that can at least block light with respect to (λ + 200) nm or less, and is taken out from the case or cassette only when the recording medium is exposed and recorded with a laser beam. Information is recorded by irradiating light.

  Furthermore, the recording medium on which information is recorded by the holographic recording method of the present invention can be taken out from the above-described case or cassette that can be shielded from light and used as a holographic information medium that can be handled in a bright room like a CD or DVD. Can be used. In this holographic information medium, a holographic information recording layer is sandwiched between a first base material and a second base material, and the holographic information recording layer includes a region mainly composed of a binder having a low refractive index. And a region mainly composed of a radical polymer formed by radical polymerization containing at least a monomer unit having an ethylenically unsaturated bond having a refractive index of 1.55 or more as a monomer unit. In a graphic information medium, since an information recording layer on which information is recorded under normal handling conditions hardly changes, there is almost no deterioration in reading with a reproducing apparatus over time.

  Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited to these examples.

  The binder-forming compounds (A-1 to 9), compounds having an ethylenically unsaturated bond (B-1 to 5), and a photopolymerization initiator (C-) used when preparing the holographic recording layer forming composition. 1-5) and sensitizing dyes (D-1 to 7) are shown below.

<Binder forming compound>
(A-1) 2-isocyanate ethyl-2,6-diisocyanate caproate (A-2) polyisocyanate of hexamethylene disiciocyanate (manufactured by Asahi Kasei Corporation, Duranate D-101)
(A-3) Polypropylene oxide adduct of glycerin (average molecular weight 1000: manufactured by NOF Corporation, Uniol TG-1000)
(A-4) Urethane curing catalyst (manufactured by Nitto Kasei Co., Ltd., Neostan U-100)
(A-5) Polypropylene glycol diglycidyl ether (Kyoeisha Chemical Co., Ltd., Epolite 200P)
(A-6) Pentaerythritol (tetrakismercaptopropionate)
(A-7) 2,4,6-tris (dimethylaminomethyl) phenol (A-8) 3-ethyl-3- (phenoxymethyl) oxetane (A-9) thermal polymerization initiator (Sanshin Chemical Industry Co., Ltd. ), Sun-Aid SI-45)
<Compound having an ethylenically unsaturated bond>
(B-1) EO-modified tribromophenyl acrylate (refractive index * 1 = 1.564: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., New Frontier BR-31)
(B-2) Hydroxyethylated β-naphthol acrylate (refractive index = 1.583: manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester А-NP-1E)
(B-3) 9,9-bis (4- (2-acryloyloxyethoxy) phenyl) fluorene (refractive index = 1.615: manufactured by Osaka Gas Co., Ltd., BPEFA)
(B-4) Phenoxyethyl acrylate (refractive index = 1.519)
(B-5) 4-Bromostyrene (refractive index = 1.594)
The refractive index * 1 was measured at 25 ° C. as a 50% styrene solution.

<Photopolymerization initiator, sensitizing dye>
Photopolymerization initiators (C-1 to 5) and sensitizing dyes (D-1 to 7) are shown below.

(C-1) Titanocene photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., Irgacure-784)
(C-2) 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole (C-3) 2,2'-bis (2,4-dichlorophenyl)- 4,4 ', 5,5'-tetraphenylbiimidazole (C-4) 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetrakis (3,4,5-trikis) Methoxyphenyl) biimidazole (C-5) 2,2'-bis (1-naphthyl) -4,4 ', 5,5'-tetrakis (m-methoxyphenyl) biimidazole

<< Preparation of holographic recording layer forming composition >>
(Holographic recording layer forming composition 1)
Under safelight, 48.92 g of the binder-forming compound (above A-5) and 8.74 g of the binder-forming compound (above A-7) were mixed to prepare Solution 1. Solution A containing 30.00 g of a separately formed binder-forming compound (supra A-6) and 11.67 g of a compound having an ethylenically unsaturated bond (supra B-5) was added to solution 1. Next, after adding and dissolving 0.670 g of the photopolymerization initiator (above C-1), the last produced composition was deaired with nitrogen, and then the gas component contained in the ultrasonic cleaner The comparative holographic recording layer forming composition 1 was produced.

(Holographic recording layer forming compositions 2 to 9)
In the holographic recording layer forming composition 1 described above, the compound having an ethylenically unsaturated bond and the photopolymerization initiator are changed to the compounds and addition amounts shown in Table 1, and the addition amounts shown in Table 1 are further added to the solution 1. Holographic recording layer forming compositions 2 to 9 were prepared in the same manner as the holographic recording layer forming composition 1 except that the sensitizing dye and 2-mercaptobenzthiazole (2MBT) were dissolved.

(Holographic recording layer forming composition 10)
Under safelight, 36.0 mg 2,6-di (t-butyl) -4-methylphenol and 67.1 mg urethane curing catalyst (above) were added to 57.82 g binder-forming compound (above A-3). A-4) was mixed and dissolved to prepare Solution 2. Separately 7.92 g of binder-forming compound (above A-1), 23.75 g of binder-forming compound (above A-2), 8.00 g of compound having an ethylenically unsaturated bond (above B-1) And a compound having an ethylenically unsaturated bond (supra B-4) were mixed and dissolved to prepare solution B, and then 0.500 g of photopolymerization initiator (supra C-1 ) Is added to the solution 2 described above, and the composition prepared last is deaerated with nitrogen, and then the gas components contained in the ultrasonic cleaner are removed, A holographic recording layer forming composition 10 was produced.

(Holographic recording layer forming compositions 11 to 22)
In the holographic recording layer forming composition 10 described above, the compound having an ethylenically unsaturated bond and the photopolymerization initiator were changed to the compounds and addition amounts described in Table 2, and the addition amounts described in Table 2 were further added to the solution 2. Holographic recording layer forming compositions 11 to 22 were prepared in the same manner as the holographic recording layer forming composition 10 except that the sensitizing dye and 2-mercaptobenzthiazole (2MBT) were dissolved.

(Holographic recording layer forming composition 23)
Under safelight, 89.32 g of binder-forming compound (above A-8), 9.00 g of compound having ethylenically unsaturated bond (above B-1), 1.00 g of ethylenically unsaturated bond Compound (above B-4), 0.923 g of photopolymerization initiator (above C-2), 12.3 mg of sensitizing dye (above D-3) and 0.930 g of 2-mercaptobenzthiazole (2MBT) was mixed and dissolved to prepare a solution C. In this solution C, 0.179 g of thermal polymerization initiator (above A-9) was added and dissolved, and after the composition produced at the end was deaerated with nitrogen, the gas contained in the ultrasonic cleaner The components were removed to prepare a holographic recording layer forming composition 23.

(Holographic recording layer forming compositions 24-28)
In the holographic recording layer forming composition 23 described above, the compounds having ethylenically unsaturated bonds, the photopolymerization initiator, the sensitizing dye, and 2-mercaptobenzthiazole (2MBT) were changed to the compounds and addition amounts shown in Table 3. Except for the above, holographic recording layer forming compositions 24 to 28 were prepared in the same manner as the holographic recording layer forming composition 19.

<Production of holographic recording media>
(Production Method 1)
As the first base material and the second base material, one side of glass having a thickness of 0.5 mm (d1, d2) is reflected so that the reflectance by incident light perpendicular to the wavelength of 532 nm is 0.1%. Prevented treatment. Holographic materials described in Tables 1 to 3 using a polyethylene terephthalate sheet as a spacer so that the recording layer thickness (Dh) described in Table 4 is provided on the surface of the first base material not subjected to antireflection treatment. The recording composition is applied to the first substrate, and then the surface of the second substrate that has not been subjected to antireflection treatment is bonded to the holographic recording composition so as not to entrain the air layer. The 1st base material and the 2nd base material were bonded through. Finally, the end was sealed with a moisture-curing adhesive, and heat-treated under the heat treatment conditions described in Table 4 to produce a holographic recording medium.

(Production method 2)
An antireflection treatment is performed on one surface of glass having a thickness of 0.5 mm (d1) so that the reflectance by incident light perpendicular to the wavelength of 532 nm is 0.1%, whereby the first substrate has a thickness of 0. A second substrate was prepared by performing aluminum deposition on one side of a glass of 5 mm (d2) so that the reflectance by incident light perpendicular to the wavelength of 532 nm was 90%. Next, a polyethylene terephthalate sheet was used as a spacer so as to have the thickness (Dh) of the recording layer described in Table 5 on the surface of the first base material not subjected to antireflection treatment. The holographic recording layer forming composition is applied to the first substrate, and then the aluminum-deposited surface of the second substrate is bonded to the holographic recording composition so as not to entrain the air layer. The 1st base material and the 2nd base material were bonded through. Finally, the end was sealed with a moisture-curing adhesive, and heat-treated under the heat treatment conditions described in Table 5 to produce a holographic recording medium.

<Recording and evaluation on holographic recording media>
(Recording on holographic recording media and evaluation 1)
Write a series of multiple holograms in accordance with the procedure described in US Pat. No. 5,719,691, with the holographic recording media produced as described above not stored for 1 week at 50 ° C. under light shielding. The sensitivity (recording energy) was measured and evaluated according to the following method, and the results obtained are shown in Table 6.

(Measurement of sensitivity)
A digital pattern is displayed on a holographic recording device equipped with an Nd: YAG laser (532 nm) on a holographic recording medium that has not been stored at 50 ° C. for one week under a safe light, and is 0.1 to 30 mJ / cm ² . Holograms were obtained by this digitally patterned holographic exposure with energy. Next, using a Nd: YAG laser (532 nm) as a reference light, the generated reproduction light was read by a CCD, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S11). Further, the holographic recording medium stored at 50 ° C. for 1 week was evaluated by the same method as described above, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S12).

  From the above table, it can be seen that the recording medium of the present invention is more sensitive before and after storage than the comparative example.

(Recording on holographic recording media and evaluation 2)
Write a series of multiple holograms in accordance with the procedure described in US Pat. No. 5,719,691, with the holographic recording media produced as described above not stored for 1 week at 50 ° C. under light shielding. The sensitivity (recording energy) was measured and evaluated according to the following method, and the results obtained are shown in Table 7.

(Measurement of sensitivity)
A digital pattern is displayed on a holographic recording device equipped with an Nd: YAG laser (532 nm) on a holographic recording medium that has not been stored at 50 ° C. for one week under a safe light, and is 0.1 to 30 mJ / cm ² . Holograms were obtained by this digitally patterned holographic exposure with energy. Next, the holographic recording medium was treated for 5 minutes under a 70,000 lux sunshine fade meter and then heated at 100 ° C. for 5 minutes. Using this processed recording medium under a safe light, an Nd: YAG laser (532 nm) is used as a reference light, the generated reproduction light is read by a CCD, and the minimum exposure amount at which a good digital pattern can be reproduced is sensitivity (S21). As measured. Further, the holographic recording medium stored at 50 ° C. for 1 week was evaluated by the same method as described above, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S22).

  From the above table, it can be seen that the recording medium of the present invention is more sensitive before and after storage than the comparative example.

(Recording on holographic recording media and evaluation 3)
A holographic recording medium produced as described above is not stored for one week at 50 ° C. under light shielding, according to the procedure described in JP-A No. 2002-123949, a series of multiple holograms is written, The sensitivity (recording energy) was measured and evaluated according to the method, and the results obtained are shown in Table 8.

(Measurement of sensitivity)
A digital pattern is displayed on a holographic recording device equipped with an Nd: YAG laser (532 nm) on a holographic recording medium that has not been stored at 50 ° C. for one week under a safe light, and is 0.1 to 30 mJ / cm ² . Holograms were obtained by this digitally patterned holographic exposure with energy. Next, the holographic recording medium was treated for 5 minutes under a 70,000 lux sunshine fade meter and then heated at 100 ° C. for 5 minutes. Using this processed recording medium under a safe light, an Nd: YAG laser (532 nm) is used as a reference light, the generated reproduction light is read by a CCD, and the minimum exposure amount at which a good digital pattern can be reproduced is sensitivity (S31). As measured. Further, the holographic recording medium stored at 50 ° C. for 1 week was evaluated by the same method as described above, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S32).

  From the above table, it can be seen that the recording medium of the present invention is more sensitive before and after storage than the comparative example.

(Recording on holographic recording media and evaluation 4)
Write a series of multiple holograms in accordance with the procedure described in US Pat. No. 5,719,691, with the holographic recording media produced as described above not stored for 1 week at 50 ° C. under light shielding. The sensitivity (recording energy) was measured and evaluated according to the following method, and the results obtained are shown in Table 9.

(Measurement of sensitivity)
A digital pattern is displayed on a holographic recording medium equipped with a semiconductor laser (405 nm) in a blue-violet region on a holographic recording medium that has not been stored at 50 ° C. for one week under a safe light, and 0.1-30 mJ / cm Holograms were obtained by this digitally patterned holographic exposure with an energy of ² . Next, the holographic recording medium was treated for 5 minutes under a 70,000 lux sunshine fade meter and then heated at 100 ° C. for 5 minutes. Using this processed recording medium under a safe light, a semiconductor laser (405 nm) in the blue-violet region is used as reference light, and the generated reproduction light is read by a CCD, and the minimum exposure amount at which a good digital pattern can be reproduced is determined with sensitivity ( Measured as S41). Further, the holographic recording medium stored at 50 ° C. for 1 week was evaluated by the same method as described above, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S42).

  From the above table, it can be seen that the recording medium of the present invention is more sensitive before and after storage than the comparative example.

(Recording on holographic recording media and evaluation 5)
A holographic recording medium produced as described above is not stored for one week at 50 ° C. under light shielding, according to the procedure described in JP-A No. 2002-123949, a series of multiple holograms is written, The sensitivity (recording energy) was measured and evaluated according to the method, and the results obtained are shown in Table 8.

(Measurement of sensitivity)
A digital pattern is displayed on a holographic recording medium equipped with a semiconductor laser (405 nm) in a blue-violet region on a holographic recording medium that has not been stored at 50 ° C. for one week under a safe light, and 0.1-30 mJ / cm Holograms were obtained by this digitally patterned holographic exposure with an energy of ² . Next, the holographic recording medium was treated for 5 minutes under a 70,000 lux sunshine fade meter and then heated at 100 ° C. for 5 minutes. Using this processed recording medium under a safe light, a semiconductor laser (405 nm) in the blue-violet region is used as reference light, and the generated reproduction light is read by a CCD, and the minimum exposure amount at which a good digital pattern can be reproduced is determined with sensitivity ( Measured as S51). Further, the holographic recording medium stored at 50 ° C. for 1 week was evaluated by the same method as described above, and the minimum exposure amount at which a good digital pattern could be reproduced was measured as sensitivity (S52).

  From the above table, it can be seen that the recording medium of the present invention is more sensitive before and after storage than the comparative example.

(Evaluation of holographic information media)
The recorded information is fixed in Table 7, Table 8, Table 9 and Table 10, and the holographic information media is stored under the following conditions, and the digital pattern is reproduced and evaluated by a method suitable for each information medium before and after storage. Then, the difference between before and after the storage of the minimum exposure amount at which a good digital pattern could be reproduced was evaluated by the following method, and the obtained results are shown in Table 11.

(Heat resistant storage stability)
The holographic information media was stored at 80 ° C. for 2 weeks, and the minimum exposure sensitivity difference (ΔSh) before and after storage was determined.

Minimum exposure sensitivity difference (ΔSh) = Minimum exposure sensitivity after storage (S2h) −Minimum exposure sensitivity before storage (S1h)
(Light-resistant storage stability)
The sample was stored for 1 week under a 70,000 lux sunshine fade meter at a temperature of 35 ° C., and the minimum exposure sensitivity difference (ΔSw) before and after storage was determined.

  Minimum exposure sensitivity difference (ΔSw) = Minimum exposure sensitivity after storage (S2w) −Minimum exposure sensitivity before storage (S1w)

  From the above table, it can be seen that the holographic information medium of the present invention shows a good result without a decrease in sensitivity for reproduction.

Claims (19)

In a holographic recording medium in which a holographic recording layer is sandwiched between a first substrate and a second substrate, the holographic recording layer has a binder-forming compound and an ethylenically unsaturated bond as a composition. At least a photopolymerization initiator capable of initiating a polymerization reaction of the compound and the compound having an ethylenically unsaturated bond, and the content of the compound having the ethylenically unsaturated bond is relative to the whole composition A holographic recording medium, wherein the content is in the range of 1 to 50% by mass, and the photopolymerization initiator contains at least a compound represented by the following general formula (1).

(In the formula, R ₁ , R ₂ and R ₃ each represents an unsubstituted or substituted aryl group, and each may be different or two or more may be the same.) The holographic recording layer further contains a sensitizing dye capable of spectrally sensitizing a photopolymerization initiator capable of initiating a polymerization reaction of a compound having an ethylenically unsaturated bond. 1. The holographic recording medium according to 1. The holographic recording medium according to claim 2, wherein the holographic recording layer further contains a chain transfer agent. The binder-forming compound contained in the holographic recording layer has (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an isocyanate group and a compound having an amino group, and (3) a carbodiimide group. Compound and compound having carboxyl group, (4) Compound having unsaturated ester group and compound having amino group, (5) Compound having unsaturated ester group and compound having mercaptan group, (6) Compound having vinyl group And a compound having a silicon hydride group, (7) a compound having an oxirane group and a compound having a mercaptan group, and (8) oxirane, oxetane, tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, cyclic Selected from Carbonate Holographic recording medium of any one of claims 1 to 3, wherein the at least one selected combination of thermal polymerization initiator and a compound having at least one in the molecule from. The binder forming compound contained in the holographic recording layer is (1) a compound having an isocyanate group and a compound having a hydroxyl group, (2) a compound having an oxirane group and a mercaptan group, and (3) an oxirane or oxetane. , Tetrahydrofuran, oxepane, monocyclic acetal, bicyclic acetal, lactone, cyclic orthoester, and a combination of a compound having one or more groups in the molecule with a cyclic carbonate and a thermal acid generator. The holographic recording medium according to claim 4, wherein the holographic recording medium is provided. The compound having an ethylenically unsaturated bond contained in the holographic recording layer contains at least a compound having a (meth) acryloyl group in the molecule. The holographic recording medium described. The compound having an ethylenically unsaturated bond contained in the holographic recording layer contains 50 to 100% by mass of a compound having a refractive index of at least 1.55 with respect to the whole compound having an ethylenically unsaturated bond. The holographic recording medium according to any one of claims 1 to 6. In the holographic recording medium, when the thickness of the first substrate is D1, the thickness of the second substrate is D2, and the thickness of the holographic recording layer is Dh, 0.15 ≦ Dh / (D1 + D2) ≦ 2. The holographic recording medium according to claim 1, wherein a relationship of 0.0 is satisfied. The holographic recording medium according to claim 8, wherein the holographic recording layer has a thickness Dh of 200 μm or more and 2.0 mm or less. 10. The holographic recording medium according to claim 1, wherein in the holographic recording medium, a relationship between a thickness D <b> 1 of the first base material and a thickness D <b> 2 of the second base material satisfies D <b> 1 ≦ D <b> 2. Recording media. 11. The holographic recording medium according to claim 1, wherein the first substrate is transparent, and an antireflection treatment is performed on a surface opposite to the surface on which the holographic recording layer is laminated. The holographic recording medium according to claim 1. The holographic recording medium according to claim 1, wherein the material of the first base material is glass. 13. The holographic recording medium, wherein a reflective layer having a reflectivity of 70% or more is laminated on the surface of the second substrate on which the holographic recording layer is laminated or on the opposite surface. The holographic recording medium according to any one of the above. The holographic recording medium according to claim 1, wherein the holographic recording medium has a disk shape. The holographic recording medium according to claim 1, wherein the holographic recording medium has a card shape. The holographic recording method for recording on the holographic recording medium according to any one of claims 1 to 15, wherein the binder forming compound is reacted with each other before forming the binder before holographic exposure is performed on the holographic recording medium. Holographic recording is performed by holographic exposure based on the information to be recorded, activating the photopolymerization initiator, and diffusion-polymerizing a compound having an ethylenically unsaturated bond in the holographic recording layer by this active species. A holographic recording method comprising recording information on a medium. 17. The holographic recording method according to claim 16, wherein after the information recording on the holographic recording medium is completed, the entire holographic recording medium is further stabilized by heat and light irradiation. The holographic recording method for recording on the holographic recording medium according to any one of claims 1 to 15, wherein holographic exposure based on information to be recorded on the recording medium is performed to activate a photopolymerization initiator. The compound having an ethylenically unsaturated bond is diffusion-polymerized by this active species to record information on the holographic recording medium, and after the information recording on the holographic recording medium is completed, the entire holographic recording medium is further heated. And a holographic recording method comprising stabilizing information recorded by light irradiation. A holographic information recording layer is sandwiched between the first base material and the second base material, and the holographic information recording layer has a region having a low refractive index binder as a main component and a refractive index of 1.55. A holographic information medium comprising a region mainly composed of a radical polymer formed by radical polymerization containing at least a compound having an ethylenically unsaturated bond as a monomer unit.