JP2007086234A - Optical recording composition and optical recording medium using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording composition and an optical recording medium that facilitates recording with lower sensitivity, allows use of an inexpensive laser and reduces the writing time. <P>SOLUTION: The optical recording composition contains at least a monomer having two or more ethyleneoxide repeating units in the molecule. A preferable embodiment of the monomer is represented by structural formula (1). In formula (1), X represents a carbonyl group or thiocarbonyl group; Y represents an alkyl group, aryl group, alkoxycarbonyl group, aryloxy carbonyl group, acyl group, alkylsulfonyl group, aryl sulfonyl group or carbamoyl group; Z represents a hydrogen atom or an alkyl group; Q represents -NR-, wherein R represents a hydrogen atom or alkyl group, an oxygen atom or a sulfur atom; and n represents an integer of 2 or larger. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is capable of recording and reproducing information using a laser beam, and in particular, an optical recording composition suitable for the production of a volume holographic optical recording medium having a thick recording layer, and the optical recording composition The present invention relates to an optical recording medium using.

  Conventionally, development of a holographic optical recording medium using a holographic principle has been advanced. When recording information, these holographic optical recording media superimpose light containing image information and reference light in a recording layer made of a photosensitive composition, and write interference fringes formed at that time in the recording layer. Is done by. On the other hand, when the recorded information is reproduced, the reference light is incident on the recording layer at a predetermined angle, whereby the reference light is diffracted by the formed interference fringes, and the information light is reproduced.

  In recent years, volume holography, in particular digital volume holography, has been developed in the practical field and has attracted attention in order to realize ultra-high density optical recording. Volume holography is a method of writing interference fringes in three dimensions by actively utilizing the thickness direction of the optical recording medium. Increasing the thickness increases the diffraction efficiency and increases the recording capacity by using multiple recording. There is a feature that can be achieved. Digital volume holography is a computer-oriented holographic recording method that uses a recording medium and a recording method similar to those of volume holography, but restricts image information to be recorded to a binarized digital pattern. In this digital volume holography, for example, image information such as an analog picture is once digitized, developed into two-dimensional digital pattern information, and recorded as image information. At the time of reproduction, the digital pattern information is read and decoded so that the original image information is restored and displayed. As a result, even if the S / N ratio (signal-to-noise ratio) is somewhat poor during reproduction, the original information can be reproduced with high fidelity by performing differential detection or performing error correction by encoding binary data. Can be reproduced (see Patent Document 1).

  In such a volume holographic optical recording medium, there is a fundamental problem in that an induction period exists and excessive light energy must be irradiated because polymerization is inhibited by oxygen during recording. Therefore, the amount of energy required for recording becomes very large and the sensitivity is lowered. Therefore, it has been disclosed to use a monomer having an ethylene group as a measure for making it difficult for oxygen polymerization inhibition to occur in a solution polymerization system (see Non-Patent Document 1). However, this monomer is unlikely to cause a termination reaction, and a high molecular weight polymer is likely to be produced, so that sufficiently satisfactory recording sensitivity is not obtained.

Japanese Patent Laid-Open No. 11-311936 T. T. et al. Y. Lee et al. Polymer 2004, 45, 6165.

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention can perform recording with lower sensitivity, can use an inexpensive laser, and can shorten the writing time, and the optical recording composition and the optical recording composition can be used. An object of the present invention is to provide an optical recording medium particularly suitable for digital volume holography.

Means for solving the above problems are as follows. That is,
<1> An optical recording composition comprising at least a monomer having two or more ethylene oxide repeating units in a molecule.
<2> The optical recording composition according to <1>, wherein the monomer having two or more ethylene oxide repeating units in the molecule is represented by the following structural formula (1).
However, in the structural formula (1), X represents either a carbonyl group or a thiocarbonyl group. Y represents any of an alkyl group, an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group, and a carbamoyl group. Z represents a hydrogen atom or an alkyl group. Q represents -NR- (wherein R represents either a hydrogen atom or an alkyl group), an oxygen atom, and a sulfur atom. n represents an integer of 2 or more.
<3> The optical recording composition according to <2>, wherein Z in the structural formula (1) is any one of a hydrogen atom and a methyl group.
<4> The optical recording composition according to any one of <2> to <3>, wherein X in the structural formula (1) is a carbonyl group.
<5> The optical recording composition according to any one of <2> to <4>, wherein Y in the structural formula (1) is an aryl group.
<6> The optical recording composition according to any one of <2> to <5>, wherein Q in the structural formula (1) is an oxygen atom.
<7> The optical recording according to any one of <1> to <6>, wherein the content of the monomer having two or more ethylene oxide repeating units in the molecule is 1 to 50% by mass. Composition.
<8> The optical recording composition according to any one of <1> to <7>, further containing a matrix and a photopolymerization initiator.
<9> An optical recording medium comprising a holographic recording layer comprising the optical recording composition according to any one of <1> to <8>.
<10> The optical recording medium according to <9>, including a lower substrate, a filter layer, a holographic recording layer, and an upper substrate.
<11> The optical recording medium according to <10>, wherein the substrate has a servo pit pattern.
<12> The optical recording medium according to <11>, wherein the servo pit pattern has a reflective film on the surface.
<13> The optical recording medium according to any one of <10> to <12>, wherein the filter layer transmits the first light and reflects the second light.
<14> The optical recording medium according to any one of <12> to <13>, further including a first gap layer for smoothing a lower substrate surface between the filter layer and the reflective film.
<15> The optical recording medium according to any one of <10> to <14>, wherein a second gap layer is provided between the holographic recording layer and the filter layer.
<16> Irradiating information light and reference light having coherence to the optical recording medium according to any one of <9> to <15>, and forming an interference image by the information light and the reference light, A method for recording an optical recording medium, wherein the interference image is recorded on a recording layer of the optical recording medium.
<17> The optical recording medium is irradiated with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial, and is generated by interference between the information light and the reference light. The method for recording an optical recording medium according to <16>, wherein the interference image is recorded on a recording layer of the optical recording medium.
<18> Optical recording, wherein information is reproduced by irradiating the interference pattern recorded on the recording layer with reference light by the recording method for an optical recording medium according to any one of <16> to <17> This is a medium reproduction method.
<19> Irradiating the optical recording medium according to any one of <9> to <15> with information light and reference light having coherence, and forming an interference image with the information light and the reference light, An optical recording / reproducing apparatus for recording the interference image on the optical recording medium.

Since the optical recording composition of the present invention contains at least a monomer having two or more ethylene oxide repeating units in the molecule as a monomer, it is possible to perform recording with lower sensitivity and use an inexpensive laser. It can be suitably used for an optical recording medium capable of reducing the writing time.
In addition, since the optical recording medium of the present invention has a holographic recording layer comprising the optical recording composition of the present invention, ultrahigh density optical recording is possible, and it is optimal as a recording medium for volume holography, particularly digital volume holography. It is.

  According to the present invention, various conventional problems can be solved, recording can be performed with lower sensitivity, an inexpensive laser can be used, and a writing time can be shortened. An optical recording medium suitable for digital volume holography using the optical recording composition can be provided.

(Optical recording composition)
The optical recording composition of the present invention contains at least a monomer having two or more ethylene oxide repeating units in the molecule, and contains a matrix, a photopolymerization initiator, and other components as necessary. .

<Monomer having two or more ethylene oxide repeating units in the molecule>
The monomer having two or more ethylene oxide repeating units in the molecule means a compound that participates in information recording and can perform radical polymerization with a photopolymerization initiator. The number of ethylene oxide repeating units in the monomer molecule is not particularly limited as long as it is 2 or more, and can be appropriately selected according to the purpose, but is preferably 2-20, more preferably 2-10. 2 to 5 are more preferable. The monomer may be monofunctional or polyfunctional, but monofunctional is particularly preferable from the viewpoint of accuracy of information light reproduction.

  As such a monomer having two or more ethylene oxide repeating units in the molecule, for example, those represented by the following structural formula (1) are suitable.

However, in the structural formula (1), X represents either a carbonyl group or a thiocarbonyl group. Y represents any of an alkyl group, an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group, and a carbamoyl group. Z represents a hydrogen atom or an alkyl group. Q represents -NR- (wherein R represents either a hydrogen atom or an alkyl group), an oxygen atom, and a sulfur atom. n represents an integer of 2 or more.

  In the structural formula (1), the alkyl group represented by Y preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and particularly preferably 1 to 5 carbon atoms. As such an alkyl group, for example, methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, isobutyl group, tertiary butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, Examples include octyl group, tertiary octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group, and 2,3-dibromopropyl group. These may further have a substituent. Examples of the substituent include a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, Examples thereof include a carboxylic acid group, a sulfonic acid group, and a heterocyclic group. Among these, a halogen atom, a phenyl group, and an aryloxy group are more preferable, and a halogen atom is particularly preferable. Examples of the halogen atom include a fluorine atom, a bromine atom, and a chlorine atom.

  In the structural formula (1), the aryl group represented by Y preferably has 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms, and particularly preferably 6 carbon atoms. Examples of such an aryl group include a phenyl group, a naphthyl group, and an anthranyl group. These may further have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, Examples include a cyano group, a carboxylic acid group, a sulfonic acid group, and a heterocyclic group. Among these, a halogen atom is more preferable. Specifically, 2,4-dibromophenyl group, 2,4-dichlorophenyl group, 2,4,6-tribromophenyl group, and 2,3,4,5,6-pentabromophenyl group are particularly preferable.

In the structural formula (1), the alkoxycarbonyl group represented by Y preferably has 2 to 20 carbon atoms, more preferably 2 to 15 carbon atoms, and particularly preferably 2 to 10 carbon atoms.
Examples of the alkoxycarbonyl group include a methyloxycarbonyl group, an ethyloxycarbonyl group, a normal propyloxycarbonyl group, an isopropyloxycarbonyl group, a normal butyloxycarbonyl group, an isobutyloxycarbonyl group, a tertiary butyloxycarbonyl group, and pentyloxy. Carbonyl group, cyclopentyloxycarbonyl group, hexyloxycarbonyl group, cyclohexyloxycarbonyl group, heptyloxycarbonyl group, octyloxycarbonyl group, tertiary octyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, decyloxycarbonyl group, dodecyloxycarbonyl group Group, octadecyloxycarbonyl group and the like. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, Examples include a cyano group, a carboxylic acid group, a sulfonic acid group, and a heterocyclic group, and a 4-bromophenyloxycarbonyl group is particularly preferable.

In the structural formula (1), the aryloxycarbonyl group represented by Y preferably has 7 to 15 carbon atoms, and more preferably 7 to 10 carbon atoms.
Examples of such aryloxycarbonyl groups include phenyloxycarbonyl group, naphthyloxycarbonyl group, anthranyloxycarbonyl group, and the like. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, Examples include a cyano group, a carboxylic acid group, a sulfonic acid group, and a heterocyclic group, and a 4-bromophenyloxycarbonyl group is particularly preferable.

  In the structural formula (1), the acyl group represented by Y preferably has 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and more preferably 2 to 5 carbon atoms. Examples of such acyl groups include methylcarbonyl group, ethylcarbonyl group, normal propylcarbonyl group, isopropylcarbonyl group, normal butylcarbonyl group, isobutylcarbonyl group, tertiary butylcarbonyl group, pentylcarbonyl group, cyclopentylcarbonyl group, Examples thereof include a hexylcarbonyl group, a cyclohexylcarbonyl group, a heptylcarbonyl group, an octylcarbonyl group, a tertiary octylcarbonyl group, a 2-ethylhexylcarbonyl group, a decylcarbonyl group, a dodecylcarbonyl group, an octadecylcarbonyl group, and a benzoyl group. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, A cyano group, a carboxylic acid group, a sulfonic acid group, a heterocyclic group and the like can be mentioned. Among these, a halogen atom is preferable, and specifically, a 2,4-dibromophenylcarbonyl group is particularly preferable.

  In the structural formula (1), the alkylsulfonyl group represented by Y preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and particularly preferably 1 to 10 carbon atoms. Examples of such an alkylsulfonyl group include a methylsulfonyl group, an ethylsulfonyl group, a normalpropylsulfonyl group, an isopropylsulfonyl group, a normalbutylsulfonyl group, an isobutylsulfonyl group, a tertiary butylsulfonyl group, a pentylsulfonyl group, and a cyclopentylsulfonyl group. Hexylsulfonyl group, cyclohexylsulfonyl group, heptylsulfonyl group, octylsulfonyl group, tertiary octylsulfonyl group, 2-ethylhexylsulfonyl group, decylsulfonyl group, dodecylsulfonyl group, octadecylsulfonyl group and the like. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, A cyano group, a carboxylic acid group, a sulfonic acid group, a heterocyclic group, and the like can be mentioned.

  In the structural formula (1), the arylsulfonyl group represented by Y preferably has 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms, and particularly preferably 6 carbon atoms. Examples of such an arylsulfonyl group include a phenylsulfonyl group, a naphthylsulfonyl group, and an anthranylsulfonyl group. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, A cyano group, a carboxylic acid group, a sulfonic acid group, a heterocyclic group and the like can be mentioned. Among these, a halogen atom is preferable, and specifically, a 2,4-dibromophenylsulfonyl group is particularly preferable.

  In the structural formula (1), the carbamoyl group represented by Y preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and particularly preferably 1 to 10 carbon atoms. Examples of such carbamoyl groups include methylaminocarbonyl group, ethylaminocarbonyl group, normal propylaminocarbonyl group, isopropylaminocarbonyl group, normal butylaminocarbonyl group, isobutylaminocarbonyl group, tertiary butylaminocarbonyl group, pentyl. Aminocarbonyl group, cyclopentylaminocarbonyl group, hexylaminocarbonyl group, cyclohexylaminocarbonyl group, heptylaminocarbonyl group, octylaminocarbonyl group, tertiary octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, decylaminocarbonyl group, dodecylamino Examples include a carbonyl group and an octadecylaminocarbonyl group. These may have a substituent. Examples of the substituent include an alkyl group, a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, A cyano group, a carboxylic acid group, a sulfonic acid group, a heterocyclic group and the like can be mentioned, and specifically, a phenylaminocarbonyl group is particularly preferable.

  In the structural formula (1), the alkyl group represented by Z preferably has 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms. Specific examples of such an alkyl group include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a tertiary butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, and a heptyl group. , An octyl group, a tertiary octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, and an octadecyl group. Among these, a methyl group is particularly preferable. These alkyl groups may further have a substituent. Examples of the substituent include a phenyl group, a halogen atom, an alkoxy group, an aryloxy group, a cyano group, a carboxylic acid group, a sulfonic acid group, and a heterocyclic ring. Among them, a halogen atom, a phenyl group, and an aryloxy group are preferable, and a halogen atom is particularly preferable.

  In the structural formula (1), Q represents —NR— (wherein R represents one of a hydrogen atom and an alkyl group), an oxygen atom, and a sulfur atom, and among these, oxygen Atoms are particularly preferred. In addition, as an alkyl group represented by R of -NR-, C1-C10 is preferable and C1-C5 is more preferable. As such an alkyl group, for example, methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, isobutyl group, tertiary butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, An octyl group, a tertiary octyl group, 2-ethylhexyl group, a decyl group, a dodecyl group, an octadecyl group, etc. are mentioned, Among these, a methyl group is particularly preferable.

  In the structural formula (1), n represents an integer of 2 or more, preferably 2 to 20, more preferably 2 to 10, and still more preferably 2 to 5.

Specific examples of the monomer having two or more ethylene oxide repeating units in the molecule are shown below, but are not limited thereto. These monomers may be used individually by 1 type, and may use 2 or more types together.

-Synthesis method of monomer having two or more ethylene oxide repeating units in the molecule-
Examples of the compound represented by M-1 as a monomer having two or more ethylene oxide repeating units in the molecule include 2,4,6-tribromophenol (manufactured by Aldrich Co., Ltd.) and 1-bromo-2- 3-Equivalent potassium carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added using hydroxyethyloxyethane (synthetic product) as a solvent and dimethylacetamide (manufactured by Tokyo Chemical Industry Co., Ltd.) as a solvent, and 2-hydroxyethyloxyethyl-2,4,6 -Tribromophenol was obtained. Dimethylacetamide (manufactured by Tokyo Chemical Industry Co., Ltd.) as a solvent and 1 equivalent of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) are added to the obtained compound and 1 equivalent of acrylic acid chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) is added at 0 ° C It can synthesize | combine by making it react for 4 hours.

The monomer having two or more ethylene oxide repeating units in the molecule may be used in combination with other monomers as necessary. The monomer used in combination may not be a monomer having two or more ethylene oxide repeating units, and examples thereof include a radical polymerization type monomer having an unsaturated bond such as an acrylic group or a methacryl group. These monomers may be monofunctional or polyfunctional.
Examples of the radical polymerization type monomer include acryloylmorpholine, phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, neo Pentyl glycol PO modified diacrylate, 1,9-nonanediol diacrylate, hydroxypivalate neopentyl glycol diacrylate, EO modified bisphenol A diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexa Acrylate, EO-modified glycerol triacrylate, trimethylol group Pantriacrylate, EO-modified trimethylolpropane triacrylate, 2-naphth-1-oxyethyl acrylate, 2-carbazoyl-9-ylethyl acrylate, (trimethylsilyloxy) dimethylsilylpropyl acrylate, vinyl-1-naphthoate, N-vinyl Examples thereof include carbazole, 2,4,6-tribromophenyl acrylate, pentabromo acrylate, phenylthioethyl acrylate, tetrahydrofurfuryl acrylate, and the like.

  There is no restriction | limiting in particular in content in the said composition for optical recording of the said monomer, Although it can select suitably according to the objective, 1-50 mass% is preferable, 1-30 mass% is more preferable, 3- 10 mass% is still more preferable. If the content exceeds 50% by mass, a stable interference image may not be obtained, and if it is less than 1% by mass, desirable performance may not be obtained in terms of diffraction efficiency.

-Analytical method of monomer having two or more ethylene oxide repeating units in the molecule-
A recording layer portion of an optical recording medium having a recording layer comprising the optical recording composition of the present invention (for example, Example 5 described later) is extracted using tetrahydrofuran (THF) or dioxane, and gas chromatography (GC ), The residual amount of the monomer having two or more ethylene oxide repeating units in the molecule was determined from the calibration curve, and it was found that about 95% or more of the monomer remained. This can also be seen from the fact that this optical recording medium can perform multiple recording.

<Matrix>
The matrix is used for the purpose of enhancing the effect of improving coating properties, film strength, and hologram recording characteristics, and is appropriately selected in consideration of compatibility with the hologram material.
The matrix is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably a thermosetting matrix, for example, a urethane resin or an oxirane compound formed from an isocyanate compound and an alcohol compound. And an epoxy compound, a melamine compound, a formalin compound, a polymer obtained by polymerizing an ester compound or an amide compound of an unsaturated acid such as (meth) acrylic acid or itaconic acid.
The matrix may be cured by heat or may be cured using a catalyst or the like.

  The content of the matrix in the optical recording composition is preferably 10 to 95% by mass, and more preferably 35 to 90% by mass. When the content is less than 10% by mass, a stable interference image may not be obtained, and when it exceeds 95% by mass, desirable performance may not be obtained in terms of diffraction efficiency.

<Photopolymerization initiator>
The photopolymerization initiator is not particularly limited as long as it has sensitivity to recording light, and includes a material that causes radical polymerization by light irradiation.
Examples of the photoinitiator include 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,1′-biimidazole, 2,4,6-tris ( Trichloromethyl) -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- (p-methoxyphenylvinyl) -1,3,5-triazine, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoro Phosphate, 4,4'-di-t-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenylbenzenediazonium hexafluorophosphate, benzoin, 2-hydroxy-2-methyl-1-phenylpropan-2-one, benzophenone, thioxanthone 2,4,6-trimethylbenzoyldipheny Acylphosphine oxide, triphenylbutylborate tetraethylammonium, bis (η-5-2,4-cyclopentadien-1-yl), bis [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyltitanium ], Diphenyl-4-phenylthiophenylsulfonium hexafluorophosphate, and the like. These may be used alone or in combination of two or more. Moreover, you may use together the sensitizing dye mentioned later according to the wavelength of the light to irradiate.
The content of the photopolymerization initiator in the optical recording composition is preferably 0.01 to 5% by mass, and more preferably 1 to 3% by mass.

<Other ingredients>
As the other component, a polymerization inhibitor or an antioxidant may be added for the purpose of improving the storage stability of the optical recording composition.
Examples of the polymerization inhibitor or the antioxidant include hydroquinone, p-benzoquinone, hydroquinone monomethyl ether, 2,6-ditertiary butyl-p-cresol, 2,2′-methylenebis (4-methyl-6-tertiary- Butylphenol), trifel phosphite, trisnonylphenyl phosphite, phenothiazine, N-isopropyl-N'-phenyl-p-phenylenediamine and the like.
The addition amount of the polymerization inhibitor or antioxidant is preferably 3% by mass or less based on the total amount of the monomers. When the addition amount exceeds 3% by mass, the polymerization may be slowed or may not be polymerized when it is remarkable.

A sensitizing dye may be added to the optical recording composition as necessary. Examples of the sensitizing dye include “Research Disclosure, Vol. 200, December 1980, Item 20036” and “sensitizer” (p.160 to p.163, Kodansha; Katsumi Tokumaru and Nobu Okawara, edited by 1987. ) And the like can be used.
Specific examples of the sensitizing dye include a 3-ketocoumarin compound described in JP-A-58-15603, a thiopyrylium salt described in JP-A-58-40302, and JP-B-59-28328. The naphthothiazole merocyanine compound described in JP-A-60-53300, the merocyanine compound described in JP-B-61-9621, JP-A-62-2842, JP-A-59-89303, and JP-A-60-60104 Can be mentioned.
Further, the dyes described in “Functional dye chemistry” (1981, CMC Publishing Co., p.393 to p.416), “Coloring materials” (60 [4] 212-224 (1987)), and the like are also included. be able to. Specific examples include a cationic methine dye, a cationic carbonium dye, a cationic quinoneimine dye, a cationic indoline dye, and a cationic styryl dye.
In addition, coumarin (including ketocoumarin or sulfonocoumarin) dyes, melostyryl dyes, oxonol dyes, hemioxonol dyes, and other keto dyes; non-ketopolymethine dyes, triarylmethane dyes, xanthene dyes, anthracene dyes, rhodamine dyes, acridine dyes Non-keto dyes such as aniline dyes and azo dyes; Non-ketopolymethine dyes such as azomethine dyes, cyanine dyes, carbocyanine dyes, dicarbocyanine dyes, tricarbocyanine dyes, hemicyanine dyes, styryl dyes; azine dyes, oxazine dyes, thiazines Dyestuffs, quinoline dyes, quinoneimine dyes such as thiazole dyes, and the like are also included in the spectral sensitizing dyes.
The said sensitizing dye may be used individually by 1 type, and may be used in combination of 2 or more type.

The optical recording composition may contain a photothermal conversion material for the purpose of improving the sensitivity of the recording layer made of the optical recording composition.
The photothermal conversion material is not particularly limited and can be appropriately selected depending on the intended function and performance. For example, it can be easily added to the recording layer together with a photopolymer, or can cause scattering of incident light. Organic dyes are preferred from the standpoint of the absence of properties, and infrared absorbing dyes are preferred in that they do not absorb or scatter light from the light source used for recording.

The infrared absorbing dye is not particularly limited and may be appropriately selected depending on the intended purpose. Cationic dyes, complex salt-forming dyes, quinone neutral dyes, and the like are preferable. The maximum absorption wavelength of the infrared absorbing dye is preferably in the range of 600 to 1,000 nm, and more preferably in the range of 700 to 900 nm.
The content of the infrared absorbing dye is determined by the absorbance of the wavelength having the highest absorbance in the infrared region in the produced recording material. As this light absorbency, the range of 0.1-2.5 is preferable, and the range of 0.2-2.0 is more preferable.

  If necessary, the optical recording composition may further contain a component that diffuses in the opposite direction to the polymerization component in order to relieve the volume change during polymerization, or an acid cleavage structure. You may add separately the compound which has it in addition to a polymer.

The optical recording composition of the present invention can be used for various optical recording compositions capable of recording information by irradiation with light containing information, and a volume holographic recording composition is particularly preferable.
If the optical recording composition has a sufficiently low viscosity, the recording layer can be formed by casting. On the other hand, if the viscosity is too high to be cast, a recording layer is placed on the lower substrate using a dispenser, and the upper substrate is pressed onto the recording layer so as to cover it, and the recording layer is spread over the entire surface to form a recording medium. be able to.

(Optical recording medium)
The optical recording medium of the present invention has a holographic recording layer comprising the optical recording composition of the present invention, and preferably has a lower substrate, a filter layer, a holographic recording layer, and an upper substrate. A reflection film, a first gap layer, a second gap layer, and other layers as necessary.

  The optical recording medium is not particularly limited as long as it can be recorded and reproduced using the principle of hologram, and records a large amount of information such as a relatively thin planar hologram or a three-dimensional image for recording information such as two dimensions. It may be a volume hologram, and may be either a transmission type or a reflection type. The hologram recording method may be any, for example, an amplitude hologram, a phase hologram, a blazed hologram, a complex amplitude hologram, or the like. Among these, information recording in the volume holographic recording area is performed by irradiating the volume holographic recording area with information light and reference light as a coaxial light beam, and recording information by an interference pattern due to interference between the information light and the reference light. The so-called collinear method is particularly preferable.

-Board-
The shape, structure, size and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. Examples of the shape include a disk shape and a card shape. It is necessary to select a material that can ensure the mechanical strength of the medium. In addition, when light used for recording and reproduction enters through the substrate, it is necessary to be sufficiently transparent in the wavelength region of the light used.
As the substrate material, glass, ceramics, resin, and the like are usually used, but resin is particularly preferable from the viewpoint of moldability and cost.
Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Among these, polycarbonate resin and acrylic resin are particularly preferable from the viewpoints of moldability, optical characteristics, and cost.
The substrate may be appropriately synthesized or a commercially available product may be used.

  The substrate is provided with a plurality of address-servo areas serving as positioning areas extending linearly in the radial direction at predetermined angular intervals, and a sector-shaped section between adjacent address-servo areas is a data area. In the address-servo area, information for performing focus servo and tracking servo by the sampled servo method and address information are recorded in advance by embossed pits (servo pits) (preformat). Note that the focus servo can be performed using the reflective surface of the reflective film. As information for performing the tracking servo, for example, a wobble pit can be used. If the optical recording medium has a card shape, the servo pit pattern may be omitted.

  There is no restriction | limiting in particular as thickness of the said board | substrate, According to the objective, it can select suitably, 0.1-5 mm is preferable and 0.3-2 mm is more preferable. If the thickness of the substrate is less than 0.1 mm, the distortion of the shape during storage of the disc may not be suppressed. If the thickness exceeds 5 mm, the mass of the entire disc increases and an excessive load is applied to the drive motor. Sometimes.

-Recording layer-
The recording layer can record information using holography, and is composed of the optical recording composition of the present invention.

There is no restriction | limiting in particular as thickness of the said recording layer, According to the objective, it can select suitably, 1-1000 micrometers is preferable and 100-700 micrometers is more preferable.
When the thickness of the recording layer is within the preferable numerical range, a sufficient S / N ratio can be obtained even when 10 to 300 multiple shift multiplexing is performed, and when the thickness is within the more preferable numerical range, this is remarkable. It is advantageous in some respects.

-Reflective film-
The reflective film is formed on the surface of the servo pit pattern of the substrate.
As the material of the reflective film, a material having a high reflectance with respect to recording light or reference light is preferably used. When the wavelength of light to be used is 400 to 780 nm, for example, Al, Al alloy, Ag, Ag alloy, etc. are preferably used. When the wavelength of light to be used is 650 nm or more, it is preferable to use Al, Al alloy, Ag, Ag alloy, Au, Cu alloy, TiN, or the like.
As the reflective film, an optical recording medium that reflects light and can be written or erased, such as a DVD (digital video disk), is used. It is also possible to add and rewrite directory information such as information on which part has an error and how replacement processing is performed without affecting the hologram.

The formation of the reflective film is not particularly limited and can be appropriately selected according to the purpose. Various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating An electron beam evaporation method or the like is used. Among these, the sputtering method is excellent in terms of mass productivity and film quality.
The thickness of the reflective film is preferably 50 nm or more, and more preferably 100 nm or more so that sufficient reflectance can be realized.

-First gap layer-
The first gap layer is provided between the filter layer and the reflective film as necessary, and is formed for the purpose of smoothing the lower substrate surface. It is also effective for adjusting the size of the hologram generated in the recording layer. That is, since it is necessary for the recording layer to form an interference region for recording reference light and information light to a certain size, it is effective to provide a gap between the recording layer and the servo pit pattern.
The first gap layer can be formed, for example, by applying a material such as an ultraviolet curable resin on the servo pit pattern by spin coating or the like and curing it. Moreover, when using what apply | coated and formed on the transparent base material as a filter layer, this transparent base material will work | function also as a 1st gap layer.
There is no restriction | limiting in particular as thickness of the said 1st gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

-Filter layer-
The filter layer is provided on the servo pits of the substrate, the reflective layer, or the first gap layer.
The filter layer has a wavelength selective reflection function that reflects only light of a specific wavelength from among a plurality of types of light, transmits the first light, and reflects the second light. In particular, the selective reflection wavelength does not shift even when the incident angle changes, and the function of preventing irregular reflection from the reflection film of the optical recording medium by the information light and the reference light, and also preventing the occurrence of noise. By laminating the filter layer on the recording medium, optical recording with high resolution and excellent diffraction efficiency can be obtained.
The filter layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a dichroic mirror layer, a color material-containing layer, a dielectric vapor deposition layer, a single layer or two or more cholesteric layers and necessary It is formed by a laminate in which at least one of other layers appropriately selected according to the above is laminated.
The filter layer may be laminated together with the direct recording layer on the substrate by coating or the like, or may be laminated on a substrate such as a film to produce a filter layer, which may be laminated on the substrate. .

-Second gap layer-
The second gap layer is provided between the recording layer and the filter layer as necessary.
The material of the second gap layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, triacetyl cellulose (TAC), polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS) ), Transparent resin films such as polysulfone (PSF), polyvinyl alcohol (PVA), polymethyl methacrylate = polymethyl methacrylate (PMMA), etc. And norbornene-based resin films. Among these, those having high isotropic properties are preferred, and TAC, PC, trade name ARTON, and trade name ZEONOR are particularly preferred.
There is no restriction | limiting in particular as thickness of the said 2nd gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

Here, the optical recording medium of the present invention will be described in more detail with reference to the drawings.
<First embodiment>
FIG. 1 is a schematic cross-sectional view showing the configuration of the optical recording medium in the first embodiment of the present invention. In the optical recording medium 21 according to the first embodiment, a servo pit pattern 3 is formed on a polycarbonate resin substrate or a glass substrate 1, and the servo pit pattern 3 is coated with aluminum, gold, platinum or the like to be a reflective film 2 is provided. In FIG. 1, the servo pit pattern 3 is formed on the entire surface of the lower substrate 1, but it may be formed periodically. The height of the servo pit pattern 3 is usually 1750 mm (175 nm), which is sufficiently smaller than the thicknesses of the substrate and other layers.

The first gap layer 8 is formed by applying a material such as an ultraviolet curable resin on the reflective film 2 of the lower substrate 1 by spin coating or the like. The first gap layer 8 is effective for protecting the reflective film 2 and adjusting the size of the hologram generated in the recording layer 4. That is, since it is necessary to form an interference area between the recording reference light and the information light in a certain size in the recording layer 4, it is effective to provide a gap between the recording layer 4 and the servo pit pattern 3.
A filter layer 6 is provided on the first gap layer 8, and an optical recording medium 21 is configured by sandwiching the recording layer 4 between the filter layer 6 and the upper substrate 5 (a polycarbonate resin substrate or a glass substrate).

In FIG. 1, the filter layer 6 transmits only red light and does not transmit light of other colors. Therefore, since the information light, the recording and reproduction reference light are green or blue light, the light does not pass through the filter layer 6 and does not reach the reflection film 2 but becomes return light and is emitted from the incident / exit surface A. Become.
The filter layer 6 is a multilayer deposited film in which high refractive index layers and low refractive index layers are alternately stacked.
The filter layer 6 composed of the multilayer deposited film may be directly formed on the first gap layer 8 by vacuum deposition, or a film having the multilayer deposited film formed on the substrate is punched into an optical recording medium shape and arranged. May be.

  The optical recording medium 21 in the present embodiment may be disk-shaped or card-shaped. In the case of a card shape, there is no need for the servo pit pattern. In this optical recording medium 21, the lower substrate 1 is 0.6 mm, the first gap layer 8 is 100 μm, the filter layer 6 is 2 to 3 μm, the recording layer 4 is 0.6 mm, and the upper substrate 5 is 0.6 mm. The total thickness is about 1.9 mm.

  Next, the optical operation around the optical recording medium 21 will be described with reference to FIG. First, light (red light) emitted from the servo laser is reflected almost 100% by the dichroic mirror 13 and passes through the objective lens 12. Servo light is irradiated onto the optical recording medium 21 by the objective lens 12 so as to be focused on the reflective film 2. That is, the dichroic mirror 13 transmits light having a wavelength of green or blue, and reflects light having a wavelength of red almost 100%. The servo light incident from the light incident / exiting surface A of the optical recording medium 21 passes through the upper substrate 5, the recording layer 4, the filter layer 6, and the first gap layer 8, is reflected by the reflective film 2, and again, The light passes through the first gap layer 8, the filter layer 6, the recording layer 4, and the upper substrate 5 and is emitted from the incident / exit surface A. The returned return light passes through the objective lens 12, is reflected almost 100% by the dichroic mirror 13, and servo information is detected by a servo information detector (not shown). The detected servo information is used for focus servo, tracking servo, slide servo, and the like. Since the hologram material constituting the recording layer 4 is not sensitive to red light, even if the servo light passes through the recording layer 4 or the servo light is irregularly reflected by the reflective film 2, the recording layer 4 is not affected. In addition, since the return light of the servo light reflected by the reflective film 2 is reflected almost 100% by the dichroic mirror 13, the servo light is detected by the CMOS sensor or the CCD 14 for detecting the reproduced image. In addition, there is no noise with respect to the reproduction light.

  The information light and the recording reference light generated from the recording / reproducing laser pass through the polarizing plate 16 to become linearly polarized light, pass through the half mirror 17 and pass through the quarter-wave plate 15 at a time. Become polarized. The optical recording medium 21 is irradiated with information light and recording reference light through the dichroic mirror 13 so as to generate an interference pattern in the recording layer 4 by the objective lens 12. The information light and the recording reference light are incident from the incident / exit surface A and interfere with each other in the recording layer 4 to generate an interference pattern there. Thereafter, the information light and the recording reference light pass through the recording layer 4 and enter the filter layer 6, but are reflected between the bottom of the filter layer 6 and become return light. That is, the information light and the recording reference light do not reach the reflective film 2. This is because the filter layer 6 is a multilayer deposited layer in which a plurality of high refractive index layers and low refractive index layers are alternately stacked, and has a property of transmitting only red light.

<Second Embodiment>
FIG. 2 is a schematic cross-sectional view showing the configuration of the optical recording medium in the second embodiment of the present invention. In the optical recording medium 22 according to the second embodiment, a servo pit pattern 3 is formed on a polycarbonate resin or glass substrate 1, and the surface of the servo pit pattern 3 is coated with aluminum, gold, platinum or the like to form a reflective film 2. Is provided. The height of the servo pit pattern 3 is the same as that of the first embodiment in that it is normally 1750 mm (175 nm).

  The difference in structure between the second embodiment and the first embodiment is that the second gap layer 7 is provided between the filter layer 6 and the recording layer 4 in the optical recording medium 22 according to the second embodiment. It is that you are. The second gap layer 7 has a point where information light and reproduction light are focused. If this area is filled with a photopolymer, excessive consumption of monomers due to overexposure occurs, resulting in a decrease in multiple recording capability. Therefore, it is effective to provide a non-reactive and transparent second gap layer.

  A filter layer 6, which is a multilayer deposited film in which a plurality of high refractive index layers and low refractive index layers are alternately stacked, is formed on the first gap layer 8 after the first gap layer 8 is formed. The thing similar to embodiment can be used.

  In the optical recording medium 22 of the second embodiment, the lower substrate 1 is 1.0 mm, the first gap layer 8 is 100 μm, the filter layer 6 is 3 to 5 μm, the second gap layer 7 is 70 μm, and the recording layer 4 is The thickness of the upper substrate 5 is 0.6 mm, and the total thickness is about 2.2 mm.

  Next, when recording or reproducing information, red servo light, green information light, and recording and reproduction reference light are applied to the optical recording medium 22 of the second embodiment having the above-described structure. Irradiated. The servo light enters from the incident / exit surface A, passes through the recording layer 4, the second gap layer 7, the filter layer 6, and the first gap layer 8 and is reflected by the reflective film 2 to become return light. The return light again passes through the first gap layer 8, the filter layer 6, the second gap layer 7, the recording layer 4, and the upper substrate 5 in this order, and exits from the incident / exit surface A. The emitted return light is used for focus servo, tracking servo, and the like. Since the hologram material constituting the recording layer 4 is not sensitive to red light, even if the servo light passes through the recording layer 4 or the servo light is irregularly reflected by the reflective film 2, the recording layer 4 is not affected. Green information light or the like enters from the incident / exit surface A, passes through the recording layer 4 and the second gap layer 7, is reflected by the filter layer 6, and becomes return light. The return light again passes through the second gap layer 7, the recording layer 4, and the upper substrate 5 in this order, and is emitted from the incident / exit surface A. Also during reproduction, not only the reproduction reference light but also the reproduction light generated by irradiating the reproduction reference light onto the recording layer 4 is emitted from the incident / exit surface A without reaching the reflection film 2. The optical operation in the vicinity of the optical recording medium 22 (the objective lens 12, the filter layer 6, the CMOS sensor or the CCD 14 as a detector in FIG. 3) is the same as that in the first embodiment, and a description thereof will be omitted.

(Recording method of optical recording medium and reproducing method of optical recording medium)
The optical recording medium recording method of the present invention irradiates the optical recording medium of the present invention with coherent information light and reference light, forms an interference image with the information light and the reference light, An image is recorded on the recording layer of the optical recording medium.
In this case, the information light and the reference light are irradiated to the optical recording medium so that the optical axis of the information light and the optical axis of the reference light are coaxial, and the information light is generated by interference between the information light and the reference light. The reproducing method of the optical recording medium of the present invention is configured to irradiate the interference pattern recorded on the recording layer by the recording method of the optical recording medium of the present invention with reference light. To play back information.

In the optical recording medium recording method and optical recording medium reproducing method of the present invention, as described above, the information light provided with a two-dimensional intensity distribution and the reference light having a substantially constant intensity are used. Information is recorded by superimposing within the photosensitive recording layer and generating a distribution of optical characteristics within the recording layer using an interference pattern formed by them. On the other hand, when reading (reproducing) written information, the recording layer is irradiated with only the reference light in the same arrangement as during recording, and the reproduction has an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer. Light is emitted from the recording layer as light.
Here, the recording method and the reproducing method of the optical recording medium of the present invention are preferably performed using the optical recording / reproducing apparatus of the present invention described below.

An optical recording / reproducing apparatus used in the recording method and reproducing method of the optical recording medium of the present invention will be described with reference to FIG.
The optical recording / reproducing apparatus 100 controls a spindle 81 to which the optical recording medium 20 is attached, a spindle motor 82 for rotating the spindle 81, and the spindle motor 82 so as to keep the rotational speed of the optical recording medium 20 at a predetermined value. A spindle servo circuit 83.
Further, the optical recording / reproducing apparatus 100 records information by irradiating the optical recording medium 20 with information light and recording reference light, and irradiates the optical recording medium 20 with reproduction reference light for reproduction. A pickup 31 for detecting light and reproducing information recorded on the optical recording medium 20 and a drive device 84 that can move the pickup 31 in the radial direction of the optical recording medium 20 are provided.

  The optical recording / reproducing apparatus 100 uses a detection circuit 85 for detecting a focus error signal FE, a tracking error signal TE, and a reproduction signal RF from an output signal of the pickup 31, and a focus error signal FE detected by the detection circuit 85. Based on this, the actuator in the pickup 31 is driven to move the objective lens (not shown) in the thickness direction of the optical recording medium 20 to perform focus servo, and the tracking error signal detected by the detection circuit 85. Based on TE, a tracking servo circuit 87 that drives an actuator in the pickup 31 to move the objective lens in the radial direction of the optical recording medium 20 to perform tracking servo, a tracking error signal TE, and a command from a controller to be described later. Drive 84 controlled by a and a slide servo circuit 88 for performing a slide servo for moving the pickup 31 in the radial direction of the optical recording medium 20.

  The optical recording / reproducing apparatus 100 further decodes output data of a later-described CMOS or CCD array in the pickup 31 to reproduce data recorded in the data area of the optical recording medium 20 or reproduce from the detection circuit 85. A signal processing circuit 89 that reproduces a basic clock and discriminates an address from the signal RF, a controller 90 that controls the entire optical recording / reproducing apparatus 100, and an operation unit 91 that gives various instructions to the controller 90; It has. The controller 90 inputs the basic clock and address information output from the signal processing circuit 89, and controls the pickup 31, spindle servo circuit 83, slide servo circuit 88, and the like. The spindle servo circuit 83 receives the basic clock output from the signal processing circuit 89. The controller 90 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the CPU executes a program stored in the ROM using the RAM as a work area. The function of the controller 90 is realized.

  Since the optical recording / reproducing apparatus used in the recording method and reproducing method of the optical recording medium of the present invention uses the optical recording medium of the present invention, the recording sensitivity is high and high-density recording can be realized.

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

Example 1
-Preparation of optical recording composition-
31.5 g of biscyclohexylmethane diisocyanate, 61.2 g of polypropylene oxide triol (molecular weight 1,000), 2.5 g of tetramethylene glycol, a monomer having two or more ethylene oxide repeating units in the molecule represented by the following structural formula (M -1) 3.1 g, a photopolymerization initiator (manufactured by Ciba Special Chemical Co., Ltd., Irgacure 784) 0.69 g, and 1.01 g of dibutyl dilaurate tin were mixed in a nitrogen stream to prepare an optical recording composition.

(Example 2)
-Preparation of optical recording composition-
Example 1 is the same as Example 1 except that the monomer (M-2) having two or more ethylene oxide repeating units in the molecule represented by the following structural formula is used instead of the monomer (M-1). Thus, an optical recording composition was prepared.

(Example 3)
-Preparation of optical recording composition-
Example 1 is the same as Example 1 except that a monomer (M-3) having two or more ethylene oxide repeating units in the molecule represented by the following structural formula is used instead of the monomer (M-1). Thus, an optical recording composition was prepared.

Example 4
-Preparation of optical recording composition-
Example 1 is the same as Example 1 except that a monomer (M-9) having two or more ethylene oxide repeating units in the molecule represented by the following structural formula was used instead of the monomer (M-1). Thus, an optical recording composition was prepared.

(Comparative Example 1)
31.5 g of biscyclohexylmethane diisocyanate, 61.2 g of polypropylene oxide triol (molecular weight 1,000), 2.5 g of tetramethylene glycol, 3.1 g of 2,4,6-tribromophenyl acrylate as a monomer, photopolymerization initiator [ Ciba Special Chemical Co., Ltd., Irgacure 784] 0.69 g and dibutyl dilaurate tin 1.01 g were mixed in a nitrogen stream to prepare an optical recording composition.

(Examples 5 to 8 and Comparative Example 2)
-Production of optical recording media-
An antireflection treatment was performed on one surface of 0.5 mm thick glass so that the reflectance by incident light perpendicular to the wavelength of 532 nm was 0.1%, and a first substrate was produced.
Aluminum vapor deposition was performed on one surface of 0.5 mm thick glass so that the reflectance by incident light perpendicular to the wavelength of 532 nm was 90%, and a second substrate was produced.
Next, a transparent polyethylene terephthalate sheet having a thickness of 500 μm was provided as a spacer on the surface of the first substrate not subjected to antireflection treatment.
Next, each of the optical recording compositions of Examples 1 to 4 and Comparative Example 1 is respectively placed on the first substrate, and the surface of the second substrate on which the aluminum is vapor deposited is not entrained on the optical recording composition. The first substrate and the second substrate were bonded through a spacer. Then, each optical recording medium was produced by leaving it at 45 ° C. for 24 hours.

<Recording and evaluation>
About each produced optical recording medium, using a collinear hologram recording / reproducing tester (manufactured by Pulstec Industrial Co., Ltd., SHOT-1000), a series of holograms with a recording spot size (diameter 200 μm) at the focal position of the recording hologram Writing was performed, and the sensitivity (recording energy) was measured and evaluated as follows. The results are shown in Table 1.

-Measurement of sensitivity-
About each produced optical recording medium, the irradiation light power (mJ / cm < ² >) at the time of recording was changed, and the change of the error probability (BER) of a reproduction signal was measured. Normally, as the luminance (μ0n) of the reproduction signal increases as the recording light power increases, the BER of the reproduction signal tends to gradually decrease. Here, the lowest recording light power at which a substantially good reproduced image (BER <10 ⁻³ ) can be obtained is defined as the recording sensitivity of the optical recording medium.

From the results of Table 1, the optical recording media of Examples 5 to 8 using the optical recording compositions of Examples 1 to 4 are the optical recording media of Comparative Example 2 using the optical recording composition of Comparative Example 1. It can be seen that recording can be performed at a lower recording sensitivity compared to the above.

  The optical recording composition of the present invention can perform recording with lower sensitivity, can use an inexpensive laser, and can shorten the writing time. Used in various hologram type optical recording media.

FIG. 1 is a schematic sectional view showing an example of an optical recording medium according to the first embodiment of the present invention. FIG. 2 is a schematic sectional view showing an example of an optical recording medium according to the second embodiment of the present invention. FIG. 3 is an explanatory diagram showing an example of an optical system around the optical recording medium according to the present invention. FIG. 4 is a block diagram showing an example of the overall configuration of an optical recording / reproducing apparatus equipped with the optical recording medium of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower substrate 2 Reflective film 3 Servo bit pattern 4 Recording layer 5 Upper substrate 6 Filter layer 7 Second gap layer 8 First gap layer 12 Objective lens 13 Dichroic mirror 14 Detector 15 1/4 wavelength plate 16 Polarizing plate 17 Half Mirror 20 Optical recording medium 21 Optical recording medium 22 Optical recording medium 31 Pickup 81 Spindle 82 Spindle motor 83 Spindle servo circuit 84 Drive device 85 Detection circuit 86 Focus servo circuit 87 Tracking servo circuit 88 Slide servo circuit 89 Signal processing circuit 90 Controller 91 Scanning Part 100 Optical recording / reproducing device A Input / output surface FE Focus error signal TE Tracking error signal RF reproduction signal

Claims (10)

  An optical recording composition comprising at least a monomer having two or more ethylene oxide repeating units in a molecule. The optical recording composition according to claim 1, wherein the monomer having two or more ethylene oxide repeating units in the molecule is represented by the following structural formula (1).
However, in the structural formula (1), X represents either a carbonyl group or a thiocarbonyl group. Y represents any of an alkyl group, an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, an alkylsulfonyl group, an arylsulfonyl group, and a carbamoyl group. Z represents a hydrogen atom or an alkyl group. Q represents -NR- (wherein R represents either a hydrogen atom or an alkyl group), an oxygen atom, and a sulfur atom. n represents an integer of 2 or more.   The optical recording composition according to claim 2, wherein Z in the structural formula (1) is any one of a hydrogen atom and a methyl group.   4. The optical recording composition according to claim 2, wherein X in the structural formula (1) is a carbonyl group.   The optical recording composition according to claim 2, wherein Y in the structural formula (1) is an aryl group.   6. The optical recording composition according to claim 2, wherein Q in the structural formula (1) is an oxygen atom.   The optical recording composition according to any one of claims 1 to 6, wherein the content of the monomer having two or more ethylene oxide repeating units in the molecule is 1 to 50% by mass.   Furthermore, the composition for optical recording in any one of Claim 1 to 7 containing a matrix and a photoinitiator.   An optical recording medium comprising a holographic recording layer comprising the optical recording composition according to claim 1. The optical recording medium according to claim 9, comprising a lower substrate, a filter layer, a holographic recording layer, and an upper substrate.