JP2009047871A - Holographic recording composition, holographic recording medium, information recording method and novel compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for holographic recording which is less in volume shrinkage and high in sensitivity, and is suitable for digital volume holography, and to provide a holographic recording medium which uses the composition for holographic recording and attains an ultra-high density optical recording. <P>SOLUTION: The composition for holographic recording contains a compound expressed by general formula (1). The holographic recording medium has a recording layer, formed from this composition for holographic recording. A method for recording information in the recording medium is also disclosed. In the general formula (1), M represents a radical polymerizable group or a substituent containing a radical polymerizable group; and A represents a divalent connecting group; and L represents a substituent decomposable through irradiation of light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a holographic recording composition suitable for producing a holographic recording medium, particularly a volume holographic recording medium. Furthermore, the present invention relates to a holographic recording medium formed using the holographic recording composition and a method for recording information on the medium.

  Conventionally, development of a holographic optical recording medium using a holographic principle has been advanced. Information is recorded on a holographic optical recording medium by superimposing information light containing image information and reference light in a recording layer made of a photosensitive composition, and writing interference fringes formed at that time on the recording layer. Done. On the other hand, when information is reproduced, reference light is incident on the recording layer on which information is recorded at a predetermined angle, whereby light diffraction of the reference light due to the formed interference fringes occurs and information light is reproduced.

  In recent years, volume holography, particularly digital volume holography, has been developed in practical use for ultra-high density optical recording and has attracted attention. 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).

  For example, Patent Document 2 discloses the use of a urethane matrix and a phenyl acrylate derivative in a photopolymer holographic optical recording medium. However, in the normal photopolymer system, volume shrinkage is accompanied when the monomer is polymerized. Volume shrinkage causes a reduction in recording capacity. Further, due to the volume shrinkage, distortion of recording interference fringes occurs, an error occurs during data input / output, and recording / reproduction sensitivity is lowered (non-patent document). 1).

On the other hand, Patent Document 3 discloses that a cationically polymerizable monomer having a small volume shrinkage is used as a recording material, and Patent Document 4 discloses a method for improving volume shrinkage by adding a volume expansion agent. ing. However, even with the techniques described in Patent Documents 3 and 4, improvement in recording / reproduction sensitivity is not sufficient.
Japanese Patent Laid-Open No. 11-311936 JP-T-2005-502918 JP-T-2004-507513 Japanese Patent No. 3508484 Journal of Japan Printing Society, 2004, 41, 25 pages

  Accordingly, an object of the present invention is to provide a holographic recording composition suitable for digital volume holography with small volume shrinkage and high sensitivity, and holographic recording capable of ultrahigh density optical recording using the holographic recording composition. To provide a medium.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
In the methods described in Patent Documents 3 and 4, the recording reaction used is polymerization of a cationic polymerization monomer. However, unlike the radical polymerization reaction, the cationic polymerization reaction does not completely inactivate, so the dark reaction proceeds. This is considered to be a cause of a decrease in recording / reproduction sensitivity. Moreover, the swelling agent described in Patent Document 4 contains an acid labile moiety and decomposes using an initiator that generates acid as a trigger. However, in the method described in Patent Document 4, the recording reaction is also triggered by an acid. For this reason, if the above-mentioned swelling agent is used, the amount of acid that triggers the recording reaction is inevitably reduced, so that a reduction in sensitivity is inevitable.
Based on the above knowledge, the present inventors have further studied and adopted radical polymerization in which a dark reaction does not proceed as a recording reaction to improve recording sensitivity and function as a recording material to compensate for volume shrinkage. It was found that a holographic recording medium capable of high-sensitivity recording / reproduction can be obtained by introducing a substituent that can be decomposed by light irradiation into the radically polymerizable compound to be obtained. It was.

That is, the means for achieving the above object is as follows.
[1] A holographic recording composition containing a compound represented by the following general formula (1).
[In General Formula (1), M represents a radical polymerizable group or a substituent containing a radical polymerizable group, A represents a divalent linking group, and L represents a substituent decomposable by light irradiation. ]
[2] The holographic recording composition according to [1], further comprising a photo radical polymerization initiator.
[3] The holographic method according to [2], wherein the substituent represented by L in the general formula (1) can be decomposed by irradiation with light having a wavelength outside the sensitive wavelength range of the photoradical polymerization initiator. Recording composition.
[4] The holographic recording composition according to any one of [1] to [3], wherein L in the general formula (1) is a substituent that can be directly excited and decomposed by light irradiation.
[5] The holographic recording composition according to any one of [1] to [4], wherein the compound represented by the general formula (1) is represented by any one of the following general formulas (2) to (6): object.
[In the general formulas (2) to (6), R ²¹ , R ²² , R ³¹ , R ⁴¹ , R ⁵¹ , R ⁶¹ and R ⁶² are each independently an alkyl group, an aryl group, a heterocyclic group, or an alkoxy group. , Aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group, cyano group, halogen group, hydroxyl group, carboxylic acid group, sulfonic acid R ²³ , R ²⁴ , R ²⁵ , R ³³ , R ³⁴ , R ³⁵ , R ⁴³ , R ⁴⁴ , R ⁵³ and R ⁵⁴ are each independently a hydrogen atom, an alkyl group or an aryl group , Heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acyl Represents an amino group, a sulfonylamino group, an amino group or an acyl group, Z represents I ⁺ or S ⁺ (—R ⁶ ), R ⁶ represents an aryl group, n1, n2, n3, n4, n5, n6 and n6 ′ independently represents an integer in the range of 0 to 5, and M and A each have the same definition as in General Formula (1). ]
[6] The holographic recording composition according to any one of [1] to [5], wherein M represents an acryl group, a methacryl group, a styryl group, or a vinyl group.
[7] The holographic recording composition according to any one of [1] to [6], further comprising a thermosetting component.
[8] The holographic recording composition according to [7], wherein the thermosetting compound includes a polyfunctional isocyanate and a polyfunctional alcohol.
[9] A holographic recording medium having a recording layer formed from the holographic recording composition according to any one of [1] to [8].
[10] A method for recording information on a holographic recording medium according to [9],
The information recording method including the step of irradiating the holographic recording medium with light having a wavelength different from that of light used for information recording.
[11] The information recording method according to [10], wherein the different wavelength is shorter than a wavelength of light irradiated for information recording.
[12] A compound represented by the following general formula (7).
[In the general formula (7), X represents a hydrogen atom or a methyl group, and R ⁷¹ represents an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryl group. Represents an oxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, a cyano group, a halogen group, a hydroxyl group, a carboxylic acid group, a sulfonic acid group, or a nitro group, and R ⁷³ and R ⁷⁴ are each independently A hydrogen atom, alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group or Represents an acyl group, and n7 represents an integer in the range of 0 to 5. , A is defined as in general formula (1). ]
[13] The compound according to [12], wherein in general formula (7), X represents a hydrogen atom, and R ⁷³ represents a hydrogen atom or an alkyl group.

  According to the present invention, it is possible to provide a holographic recording medium in which volume shrinkage is compensated and capable of high-sensitivity recording / reproduction. The holographic recording medium of the present invention is suitable as a recording medium for digital volume holography, which can perform ultra-high density recording and can achieve volume holography, in particular, use of an inexpensive laser and shortening of writing time.

[Holographic recording composition]
The holographic recording composition of the present invention contains a compound represented by the following general formula (1).

In general formula (1), M represents a radical polymerizable group or a substituent containing a radical polymerizable group, A represents a divalent linking group, and L represents a substituent decomposable by light irradiation. The holographic recording composition of the present invention is suitable as a volume holographic recording composition. As described above, holographic recording is information recording in which information light containing information and reference light are superimposed in a recording layer and information is recorded by writing an interference image formed at that time in the recording layer. Volume holographic recording is an information recording method in which an interference image is three-dimensionally written on a recording layer in holographic recording. The compound represented by the general formula (1) can function as a recording material during holographic recording. When a polymerizable compound is used as a recording material in holographic recording, there are problems such as a reduction in recording capacity due to volume shrinkage during polymerization and generation of distortion of interference fringes. Therefore, in the present invention, a compound represented by the general formula (1) containing a substituent L decomposable by light irradiation is used as the polymerizable compound that can function as a recording material. When the substituent L is cleaved by light irradiation, at least one molecule is released from the compound represented by the general formula (1). Volume expansion due to molecular release can compensate for volume shrinkage during polymerization. At the time of holographic recording, the polymer is formed along the interference fringes of the recording light, so that the formation of the polymer in the recording layer occurs locally. Therefore, in order to compensate for volume shrinkage, it is effective that the expansion mechanism occurs around the polymer formed by polymerization. According to the compound represented by the general formula (1), molecules can be released (volume expansion) around the polymer locally formed in the recording layer, so that interference fringe distortion due to volume contraction is effective. Can be compensated for.
Hereinafter, the holographic recording composition of the present invention will be described in more detail.

Compound represented by general formula (1)

  In general formula (1), M represents a radically polymerizable group or a substituent containing a radically polymerizable group. Specific examples of the substituent represented by M include radical polymerization type functional groups having an unsaturated bond such as an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, a styryl group, and a vinyl group. . Preferably, M is an acryl group, a methacryl group or an acrylamide group.

A represents a divalent linking group, and specific examples include an alkylene group and an arylene group. The alkylene group may be linear or branched. Further, it may be unsubstituted or may have a substituent. 1-30 are preferable and, as for the carbon number, 1-20 are more preferable. Further, the alkylene chain may have divalent functional groups so as not to be adjacent to each other. Examples of such a divalent functional group include —O—, —S—, —OCO—, —COO—, —NR—, —CONR—, —NRCO—, —CO—, —SO—, —SO _2. -, - SONR -, - SO 2 NR- , and the like. The aforementioned R represents a hydrogen atom, an alkyl group, or a phenyl group. Specific examples thereof will be described later. Among them, -O- or -S- is preferable, and -O- is particularly preferable. The arylene group may have a substituent, preferably has 6 to 30 carbon atoms, and particularly preferably has 6 to 20 carbon atoms. The arylene chain may have divalent functional groups so as not to be adjacent to each other, and as such a divalent functional group, —O— or —S— is preferable, and —O— is particularly preferable. .

  The substituent that can be decomposed by light irradiation represented by L in the general formula (1) is decomposed by irradiation with light of a certain wavelength, and the compound represented by the general formula (1) is cleaved into two or more molecules. Any substituent may be used. Photolysis may occur at least at one position in the substituent L, and may occur at two or more positions, but it is preferable to cleave at one position in L.

  The photodecomposition of the substituent L may be triggered by energy transfer from a sensitizer or the like accompanying light irradiation, but may be decomposed by itself by direct excitation by light irradiation. From the viewpoint of recording sensitivity, the substituent L is preferably capable of being directly excited and decomposed by light irradiation.

  Specific examples of the substituent L include those similar to the structure of a photocleavable protective compound described in a review by VN Rajasekharan Pillai (Synthesis 1980, 132, 1) and a commonly used photopolymerizable initiator. it can. Specific structures of these combinations include nitrobenzyl derivatives, α-substituted nitrobenzyl derivatives, nitrobenzyloxycarbonyl derivatives, nitrophenylethylene glycol derivatives, benzoyloxycarbonyl derivatives, nitrophenyl derivatives, nitrophenyloxy derivatives, nitrophenyloxy Examples include carbonyl derivatives, phenacyl derivatives, methoxyphenacyl derivatives, dinitrobenzenesulfenyl derivatives and the like. Photopolymerization initiators include acetophenone derivatives, α-alkoxyacetophenone derivatives, α-aminoacetophenone derivatives, phenylglyoxylic acid derivatives, Acylphosphine oxide derivatives, diacylphosphine oxide derivatives, benzoyloxime derivatives, peroxide derivatives, iodonium salt derivatives Body, and the like sulfonium salts derivatives.

  In general formula (1), the groups represented by M, A, and L may each further have a substituent. The details of such a substituent are as described later for the substituent that may further have a substituent in the general formulas (2) to (6).

Preferred specific examples of the compound represented by the general formula (1) include compounds represented by the following general formulas (2) to (6). More preferred specific examples include the general formula (described later) The compound represented by 7) can be mentioned. Preferable specific examples of the substituent L in the general formula (1) include substituents linked to A in the following general formulas (2) to (6), and more preferable specific examples include those described later. In the formula (7), a substituent linked to A can be exemplified. In the following, in the general formulas (2) to (7), the partial structure corresponding to the substituent L in the general formula (1) may be referred to as “L part”.
The compounds represented by the general formulas (2) to (6) are described below.

In the general formulas (2) to (6), R ²¹ , R ³¹ , R ⁴¹ , R ⁵¹ , R ⁶¹ and R ⁶² (hereinafter collectively referred to as “Ra”) are each independently an alkyl group, Aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group, cyano group, halogen group Represents a hydroxyl group, a carboxylic acid group, a sulfonic acid group or a nitro group, and R ²³ , R ²⁴ , R ²⁵ , R ³³ , R ³⁴ , R ³⁵ , R ⁴³ , R ⁴⁴ , R ⁵³ and R ⁵⁴ (hereinafter referred to as these Are also each independently a hydrogen atom, alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group. Represents an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, or an acyl group, Z is represents I ⁺ or ^{S + (-R 6), R} 6 represents an aryl group , N1, n2, n3, n4, n5, n6 and n6 ′ (hereinafter collectively referred to as “n”) each independently represents an integer in the range of 0 to 5, and M and A are general It is synonymous with the definition in Formula (1).

  The alkyl groups represented by Ra and Rb may be linear or branched, and may be unsubstituted or have a substituent. The carbon number is preferably 1 to 10, more preferably 1 to 5, and most preferably 1. Specific examples of such alkyl groups include 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. Octyl group, tertiary octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group and the like.

  The aryl groups represented by Ra and Rb may be unsubstituted or have a substituent, and can be appropriately selected depending on the purpose. The number of carbon atoms is preferably 6-20, more preferably 6-10, and particularly preferably 6. Specifically, a phenyl group, a tolyl group, a naphthyl group, an anthranyl group, etc. are mentioned.

  There is no restriction | limiting in particular as a heterocyclic group represented by Ra and Rb, Although it can select suitably according to the objective, What is C4-C20 is preferable and C4-C10 is preferable. More preferred are those with 4 or 5. Specific examples include a pyridyl group and a pyrrole group.

  The alkoxy group represented by Ra and Rb may be linear or branched, and may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such alkoxy groups include methoxy, ethoxy, normal propyloxy, isopropyloxy, normal butyloxy, isobutyloxy, tertiary butyloxy, pentyloxy, cyclopentyloxy, hexyloxy. Group, cyclohexyloxy group, heptyloxy group, octyloxy group, tertiary octyloxy group, 2-ethylhexyloxy group, decyloxy group, dodecyloxy group, octadecyloxy group, 2,3-dibromopropyloxy group, adamantyloxy group, Examples include benzyloxy group and 4-bromobenzyloxy group.

  The aryloxy group represented by Ra and Rb may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. For example, a phenyloxy group, a naphthyloxy group, an anthranyloxy group, etc. are mentioned.

  The alkylthio groups represented by Ra and Rb may be linear or branched, and may be unsubstituted or may have a substituent. The carbon number is preferably 1-30, and more preferably 1-20. Examples of such an alkylthio group include a methylthio group, an ethylthio group, a normal propylthio group, an isopropylthio group, a normal butylthio group, an isobutylthio group, a tertiary butylthio group, a pentylthio group, a cyclopentylthio group, a hexylthio group, Cyclohexylthio group, heptylthio group, octylthio group, tertiary octylthio group, 2-ethylhexylthio group, decylthio group, dodecylthio group, octadecylthio group, 2,3-dibromopropylthio group, adamantylthio group, benzylthio group, 4- Examples include a bromobenzylthio group.

  The arylthio group represented by Ra and Rb may be unsubstituted or may have a substituent. The carbon number is preferably 6 to 30, and particularly preferably 6 to 20. For example, a phenylthio group, a naphthylthio group, an anthranylthio group, etc. are mentioned.

  Examples of the alkoxycarbonyl group represented by Ra and Rb include methyloxycarbonyl group, ethyloxycarbonyl group, normal propyloxycarbonyl group, isopropyloxycarbonyl group, normal butyloxycarbonyl group, isobutyloxycarbonyl group, and tertiary butyloxycarbonyl group. Group, pentyloxycarbonyl group, cyclopentyloxycarbonyl group, hexyloxycarbonyl group, cyclohexyloxycarbonyl group, heptyloxycarbonyl group, octyloxycarbonyl group, tertiary octyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, decyloxycarbonyl group And dodecyloxycarbonyl group.

  The aryloxycarbonyl group represented by Ra and Rb may be unsubstituted or may have a substituent. The carbon number is preferably 7-30, and particularly preferably 7-20. For example, a phenyloxycarbonyl group, a naphthyloxycarbonyl group, an anthranyloxycarbonyl group, etc. are mentioned.

  Examples of the acyloxy group represented by Ra and Rb include a methylcarbonyloxy group, an ethylcarbonyloxy group, a normal propylcarbonyloxy group, an isopropylcarbonyloxy group, a normal butylcarbonyloxy group, an isobutylcarbonyloxy group, and a tertiary butylcarbonyloxy group. Pentylcarbonyloxy group, cyclopentylcarbonyloxy group, hexylcarbonyloxy group, cyclohexylcarbonyloxy group, heptylcarbonyloxy group, octylcarbonyloxy group, tertiary octylcarbonyloxy group, 2-ethylhexylcarbonyloxy group, decylcarbonyloxy group, A dodecylcarbonyloxy group, a benzoyloxy group, etc. are mentioned.

  Examples of the acylamino group represented by Ra and Rb include a methylcarbonylamino group, an ethylcarbonylamino group, and a phenylcarbonylamino group.

  Examples of the sulfonylamino group represented by Ra and Rb include a methylsulfonylamino group, an ethylsulfonylamino group, and a phenylsulfonylamino group.

  The amino group represented by Ra and Rb may be a mono-substituted amino group or a di-substituted amino group, and a di-substituted amino group is preferable. For example, a dimethylamino group, a diphenylamino group, etc. are mentioned.

  Examples of the acyl group represented by Ra and Rb include an acetyl group and a benzoyl group.

  Examples of the halogen group represented by Ra include a chloro group, a bromo group, and an iodo group, and a bromo group is preferable.

  Moreover, the substituent represented by Ra and Rb may further have a substituent. Examples of the substituent include an alkyl group, a phenyl group, an amino group, a halogen atom, an alkoxy group, an aryloxy group, Examples thereof include an alkoxycarbonyl group, an acyloxy group, an acylamino group, a carbamoyl group, a cyano group, and a heterocyclic group. Among these, an alkyl group is more preferable.

  Of these, Ra is preferably an alkyl group, an alkoxy group, an aryloxy group or a halogen group, more preferably an alkyl group or an alkoxy group. Rb is preferably an alkyl group, an alkoxy group, or an aryloxy group, and more preferably an alkyl group or an alkoxy group.

In the general formula (6), Z represents I ⁺ or S ⁺ —R ⁶ , and R ⁶ represents an aryl group. Specific examples of the aryl group for R ⁶ are as described above. The anion forming the counter salt with the compound represented by the general formula (6) is not particularly limited as long as it can neutralize the charge.

  In general formula (2)-(6), n represents the integer of the range of 0-5. n is preferably an integer in the range of 0 to 3, particularly preferably 0 or 1.

  Especially, it is preferable that the compound represented by General formula (1) is represented by General formula (2). Furthermore, as a preferable aspect of the compound represented by General formula (2), the compound represented by following General formula (7) can be mentioned.

In the general formula (7), X represents a hydrogen atom or a methyl group, and R ⁷¹ represents an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryl group. Represents an oxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, a cyano group, a halogen group, a hydroxyl group, a carboxylic acid group, a sulfonic acid group, or a nitro group, and R ⁷³ and R ⁷⁴ are each independently A hydrogen atom, alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group or Represents an acyl group, and n7 represents an integer in the range of 0 to 5. And A has the same definition as in general formula (1).

In general formula (7), details of R ⁷¹ are as described for R ²¹ in general formula (2), and details of R ⁷³ are described for R ²³ in general formula (2). The details of R ⁷⁴ are as described above for R ²⁴ in general formula (2). In general formula (7), ^R71 preferably represents a hydrogen atom or an alkyl group. The details of A in the general formula (7) are as described above.

  In general formula (7), X represents a hydrogen atom or a methyl group, and is preferably a hydrogen atom.

  In general formula (7), n7 represents an integer in the range of 0 to 5, preferably represents an integer in the range of 0 to 3, more preferably represents an integer in the range of 0 to 2, and 0 or 1 It is particularly preferred.

  Specific examples of the compound represented by the general formula (1) are shown below. However, the present invention is not limited to the following specific examples.

  The compound represented by the general formula (1) described above can be synthesized by a known method. Below, an example of the synthetic scheme of the compound represented by General formula (7) is shown. Various compounds can be synthesized by obtaining nitrophenol derivatives as raw materials. Moreover, the Example mentioned later can also be referred about the synthesis method of the compound represented by General formula (1).

[In the above scheme, R ′ has the same meaning as (R ⁷¹ ) _n7 in general formula (7), and R has the same meaning as R ⁷⁴ in general formula (7)].

  The holographic recording composition of the present invention may contain only one type of compound represented by the general formula (1), or may contain two or more types. The content of the compound represented by the general formula (1) in the holographic recording composition of the present invention is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 to 50% by mass, 1-30 mass% is more preferable, and 3-10 mass% is still more preferable. If the content is 50% by mass or less, the stability of the interference image can be easily secured, and if it is 1% by mass or more, desirable performance can be obtained in terms of diffraction efficiency.

Photoradical polymerization initiator The holographic recording composition of the present invention usually contains a photoradical polymerization initiator together with the compound represented by the general formula (1). The compound represented by the general formula (1) causes a radical polymerization reaction by the action of a photo radical polymerization initiator that is excited in response to light irradiated for information recording, thereby recording interference fringes as refractive index modulation. can do. Since the radical polymerization reaction does not proceed with dark reaction, highly sensitive recording / reproduction is possible.

  The radical photopolymerization initiator is not particularly limited as long as it has sensitivity to recording light. For example, 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 hexafluorophosphate, 4,4′-di-t-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenylbenzenediazonium hexafluorophosphate, benzoin, 2-hydroxy -2-methyl-1-phenylpropan-2-one, benzo Enone, thioxanthone, 2,4,6-trimethylbenzoyldiphenylacylphosphine oxide, triphenylbutyl borate tetraethylammonium, diphenyl-4-phenylthiophenylsulfonium hexafluorophosphate, 2,2-dimethoxy-1,2-diphenylethane-1 -One, phenylglyoxylic acid methyl ester, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, bis (2,4,6-trimethylbenzoyl) -phenylphos Fin oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], bis (η5-2 , 4-Cyclopentadie 1-yl) bis [2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl titanium], such as 2,4,6-trimethylbenzoyl phenyl phosphinate ethyl ester. These may be used individually by 1 type and may use 2 or more types together. Moreover, you may use together the sensitizing dye mentioned later according to the wavelength of the light to irradiate.

  The content of the radical photopolymerization initiator in the holographic recording composition of the present invention is preferably 0.01 to 5% by mass, and more preferably 1 to 3% by mass.

  From the viewpoint of recording characteristics, it is preferable that all the light irradiated for information recording is used for the recording reaction. From this point, by irradiating light of a wavelength different from the light irradiated to excite the radical photopolymerization initiator for initiating radical polymerization of the compound represented by the general formula (1), the general formula ( It is preferable to photolyze the substituent L in 1). From this point, in determining the composition of the holographic recording composition of the present invention, after determining the photoradical polymerization initiator, it is decomposed by irradiating light with a wavelength outside the sensitive wavelength range of the photoradical polymerization initiator. It is preferable to select a compound represented by the general formula (1) having a substituent L to be obtained, or after the compound represented by the general formula (1) is determined, the substituent L in the compound can be decomposed It is preferable to select a photo radical polymerization initiator that is not sensitive to light.

In the compound represented by the general formula (2), the L portion is excited and decomposed by irradiation with light having a wavelength of usually 370 nm or less. In the compound represented by the general formula (3), the L portion is excited and decomposed by irradiation with light having a wavelength of usually 410 nm or less. In the compound represented by the general formula (4), the L part is excited and decomposed by irradiation with light having a wavelength of 440 nm or less. The compound represented by the general formula (5) is usually excited and decomposed by irradiation with light having a wavelength of 420 nm or less. The compound represented by the general formula (6) is usually excited and decomposed by irradiation with light having a wavelength of 360 nm or less. On the other hand, the sensitivity wavelength of a typical photo radical polymerization initiator is shown below.
2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,1′-biimidazole: 365 nm
・ Diphenyliodonium tetrafluoroborate: 380 nm
2-hydroxy-2-methyl-1-phenylpropan-2-one: 370 nm
・ Benzophenone: 380 nm
2,4,6-trimethylbenzoyldiphenylacylphosphine oxide: 410 nm
1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]: 410 nm
Bis (η5-2,4-cyclopentadien-1-yl) bis [2,6-difluoro-3- (1H-pyrrol-1-yl) phenyltitanium]: 532 nm
In the composition for holographic recording of the present invention, photoradical polymerization is performed so that the L part is not excited and decomposed when irradiated with recording light, and the L part can be excited and decomposed by irradiating light having a wavelength different from that of the recording light. It is preferable to select a combination of the initiator and the compound represented by the general formula (1).

Radical polymerizable monomer The holographic recording composition of the present invention may contain another radical polymerizable monomer together with the compound represented by the general formula (1). The radical polymerizable monomer that can be used in combination may be monofunctional or other functional, and may be used alone or in combination of two or more. Other monomers used in combination include, for example, acryloylmorpholine, phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, neopentyl 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 hexaacrylate , EO-modified glycerol triacrylate, trimethylol proppant Acrylate, EO-modified trimethylolpropane triacrylate, 2-naphth-1-oxyethyl acrylate, 2-carbazoyl-9-ylethyl acrylate, (trimethylsilyloxy) dimethylsilylpropyl acrylate, vinyl-1-naphthoate, 2,4,6 -Tribromophenyl acrylate, pentabromo acrylate, phenylthioethyl acrylate, tetrahydrofurfuryl acrylate, bisphenoxyethanol fluorene acrylate, styrene, p-chlorostyrene, N-vinyl carbazole, N-vinyl pyropydon and the like. Among these, phenoxyethyl acrylate, 2,4,6-tribromophenyl acrylate, pentabromoacrylate, and bisphenoxyethanol full orange acrylate are preferable, and 2,4,6-tribromophenyl acrylate and bisphenoxyethanol full orange acrylate are more preferable. What is necessary is just to set the addition amount of another monomer suitably. However, in terms of volume shrinkage compensation, it is preferable to use only the compound represented by the general formula (1) as the polymerizable compound for holographic recording.

The recording layer of the matrix optical recording medium contains a monomer generally called a matrix, which is related to recording and storage, and a polymer for holding a photopolymerization initiator. The matrix is used for the purpose of enhancing the effects of improving coating properties, film strength, and hologram recording characteristics. The holographic recording composition of the present invention can contain a curable compound as a matrix binder and / or a matrix-forming component (matrix precursor), particularly when used in optical recording applications. A method of forming a matrix by applying a composition containing a matrix precursor to, for example, a substrate surface and then performing a curing treatment is preferable because a recording layer can be formed without using a solvent or using a small amount of solvent. . As the curable compound, a photocurable compound that is cured by light irradiation using a thermosetting compound or a catalyst can be used, and a thermosetting compound is preferable in terms of recording characteristics.

The thermosetting matrix is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an epoxy compound or a melamine compound formed from a urethane resin or oxirane compound formed from an isocyanate compound and an alcohol compound. , A formalin compound, a polymer obtained by polymerizing an ester compound of an unsaturated acid such as (meth) acrylic acid or itaconic acid, or an amide compound. Among them, a polyurethane matrix formed from an isocyanate compound and an alcohol compound is preferable, and a three-dimensional polyurethane matrix formed from a polyfunctional isocyanate and a polyfunctional alcohol is most preferable in view of record retention. In the present invention, “polyfunctional” means bifunctional or higher.
Specific examples of polyfunctional isocyanates and polyfunctional alcohols that can form a polyurethane matrix are described below.

  Specific examples of the polyfunctional isocyanate include biscyclohexylmethane diisocyanate, hexamethylene diisocyanate, phenylene-1,3-diisocyanate, phenylene-1,4-diisocyanate, 1-methoxyphenylene-2,4-diisocyanate, 1- Methylphenylene-2,4-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, biphenylene-4,4′-diisocyanate, 3,3′-dimethoxybiphenylene-4,4′-diisocyanate, 3,3′-dimethylbiphenylene-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-dii Socyanate, 3,3′-dimethoxydiphenylmethane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, naphthylene-1,5-diisocyanate, cyclobutylene-1,3-diisocyanate, cyclo Pentylene-1,3-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, 1-methylcyclohexylene-2,4-diisocyanate, 1-methylcyclohexylene-2,6-diisocyanate 1-isocyanate-3,3,5-trimethyl-5-isocyanate methylcyclohexane, cyclohexane-1,3-bis (methyl isocyanate), cyclohexane-1,4-bis (methyl isocyanate), isophorone diiso Cyanate, dicyclohexylmethane-2,4′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, ethylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, dodecamethylene-1,12- Diisocyanate, phenyl-1,3,5-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, diphenylmethane-2,5,4'-triisocyanate, triphenylmethane-2,4 ', 4 "-triisocyanate Isocyanate, triphenylmethane-4,4 ', 4 "-triisocyanate, diphenylmethane-2,4,2', 4'-tetraisocyanate, diphenylmethane-2,5,2 ', 5'-tetraisocyanate, cyclohexane-1 , 3,5-torii Cyanate, cyclohexane-1,3,5-tris (methyl isocyanate), 3,5-dimethylcyclohexane-1,3,5-tris (methyl isocyanate), 1,3,5-trimethylcyclohexane-1,3,5- Stoichiometric excess of tris (methyl isocyanate), dicyclohexylmethane-2,4,2′-triisocyanate, dicyclohexylmethane-2,4,4′-triisocyanine lysine diisocyanate methyl ester, or these organic isocyanate compounds And a bifunctional isocyanate prepolymer obtained by reaction with a polyfunctional active hydrogen-containing compound. Among these, biscyclohexylmethane diisocyanate and hexamethylene diisocyanate are particularly preferable. These may be used individually by 1 type and may use 2 or more types together.

  The polyfunctional alcohol may be a polyfunctional alcohol alone or in a mixed state with other polyfunctional alcohols. Polyfunctional alcohols include glycols such as ethylene glycol, triethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and neopentyl glycol; diols such as butanediol, pentanediol, hexanediol, heptanediol, and tetramethylene glycol Such as bisphenols, compounds obtained by modifying these polyfunctional alcohols with polyethyleneoxy chain or polypropyleneoxy chain, triols such as glycerin, trimethylolpropane, butanetriol, pentanetriol, hexanetriol, decanetriol, etc. Examples include compounds obtained by modifying functional alcohols with polyethyleneoxy chains or polypropyleneoxy chains.

  10-95 mass% is preferable and, as for content of the said matrix formation component (or matrix) in the composition for holographic recording of this invention, 35-90 mass% is more preferable. When the polymerizable compound of the present invention is used as a holographic recording composition such as a holographic recording composition, a stable interference image can be easily obtained if the content is 10% by mass or less. If it is 95% by mass or less, desirable performance can be obtained in terms of diffraction efficiency.

Other Components A polymerization inhibitor and an antioxidant may be added to the holographic recording composition of the present invention as needed for the purpose of improving the storage stability of the composition.
Examples of the polymerization inhibitor or 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 polymerizable component. 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 can be added to the holographic recording composition of the present invention 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.
Furthermore, 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 holographic recording composition of the present invention may contain a photothermal conversion material for the purpose of improving the sensitivity of a recording layer formed from the composition, particularly when applied to optical recording applications.
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 can be determined by the absorbance of the wavelength having the highest absorbance in the infrared region in the recording layer formed from the holographic recording composition of the present invention. As this light absorbency, the range of 0.1-2.5 is preferable, and the range of 0.2-2.0 is more preferable.

The holographic recording composition of the present invention can be used for various holographic recording compositions that can record information by irradiation with light containing information, and among others, as volume holographic recording compositions. Is preferred.
If the 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.

[Holographic recording media]
The holographic recording medium of the present invention has a recording layer formed from the holographic recording composition of the present invention. For example, a recording layer comprising the holographic recording composition of the present invention can be formed by the method described above.

  The holographic recording medium of the present invention includes the recording layer (holographic recording layer), and preferably includes a lower substrate, a filter layer, a holographic recording layer, and an upper substrate. And other layers such as a reflective film, a filter layer, a first gap layer, and a second gap layer.

  The holographic recording medium of the present invention is capable of recording / reproducing information using the principle of hologram, and is a volume for recording 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 hologram, and may be either a transmission type or a reflection type. The holographic recording medium of the present invention is suitable as a volume holographic recording medium for which high recording density is required because high capacity information recording is possible.

  Further, the recording method of the hologram on the holographic recording medium of the present invention is not particularly limited, and for example, an amplitude hologram, a phase hologram, a blazed hologram, a complex amplitude hologram, or the like may be used. 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.

  Below, the detail of the board | substrate and each layer which may be contained in the holographic recording medium of this invention is demonstrated one by one.

-Board-
There is no restriction | limiting in particular about the shape, a structure, a magnitude | size, etc., a board | substrate can be suitably selected according to the objective. Examples of the shape include a disk shape and a card shape, and a material that can ensure the mechanical strength of the holographic recording medium should be selected. In addition, when light used for recording and reproduction enters through the substrate, it is preferable that the light is sufficiently transparent in the wavelength region of the light used.

  As the substrate material, glass, ceramics, resin, and the like are usually used, and 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, urethane resin, and the like. Among these, polycarbonate resin and acrylic resin are particularly preferable from the viewpoints of moldability, optical characteristics, and cost. As a board | substrate, what was synthesize | combined suitably may be used and a commercial item may be used.

  The substrate is usually provided with a plurality of address-servo areas as linearly extending positioning areas 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) or the like (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. In the case where the holographic recording medium has a card shape, the servo pit pattern may be omitted.

  There is no restriction | limiting in particular as thickness of a 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 0.1 mm or more, the distortion of the shape during storage of the disc can be suppressed, and if it is 5 mm or less, the mass of the entire disc increases and an excessive load is applied to the drive motor. It can be avoided.

-Recording layer-
The recording layer is formed from the holographic recording composition of the present invention, and information can be recorded using holography. There is no restriction | limiting in particular as thickness of a recording layer, According to the objective, it can select suitably. If the thickness of the recording layer is in the range of 1 to 1,000 μm, a sufficient S / N ratio can be obtained even if shift multiplexing of 10 to 300 is performed, and if it is in the range of 100 to 700 μm, this is remarkable. This is advantageous.

-Reflective film-
The reflective film can be formed on the servo pit pattern surface of the substrate.
As a material for the reflective film, a material having a high reflectance with respect to information light and reference light is preferably used. When the wavelength of light used as information light and reference light is 400 to 780 nm, for example, it is preferable to use Al, Al alloy, Ag, Ag alloy, or the like. When the wavelength of light used as information light and reference light is 650 nm or more, it is preferable to use Al, Al alloy, Ag, Ag alloy, Au, Cu alloy, TiN, or the like.
In addition, by using an optical recording medium that reflects light and can be added or erased as a reflective film, for example, a DVD (digital video disk), it is possible to rewrite to what area the hologram has been recorded. It is also possible to additionally write and rewrite directory information such as in which part an error exists and how the alternation process was performed without affecting the hologram.

The method for forming 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 achieved.

-Filter layer-
The filter layer can be provided on the servo pits of the substrate, on the reflective layer, or on the first gap layer described later.
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 rays, transmits the first light, and reflects the second light. In particular, even if the incident angle changes, the selective reflection wavelength does not shift, and the function of preventing irregular reflection from the reflection film of the recording medium by the information light and the reference light and the generation of noise are also provided. By laminating filter layers, optical recording with high resolution and excellent diffraction efficiency can be performed.
There is no restriction | limiting in particular as a filter layer, According to the objective, it can select suitably, For example, a dichroic mirror layer, a coloring material containing layer, a dielectric material vapor deposition layer, a single layer or two or more cholesteric layers, and as needed It is possible to form a laminate in which at least one of the other layers appropriately selected is laminated. Although the thickness is not specifically limited, For example, it is about 0.5-20 micrometers.
The filter layer may be directly laminated on the substrate together with the recording layer 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.

-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 area for the recording reference light and the information light to a certain extent, 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 a 1st gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

-Second gap layer-
The second gap layer is provided between the recording layer and the filter layer as necessary.
There is no restriction | limiting in particular as a material of a 2nd gap layer, According to the objective, it can select suitably, For example, a triacetyl cellulose (TAC), a polycarbonate (PC), a polyethylene terephthalate (PET), a polystyrene (PS) Transparent resin films such as polysulfone (PSF), polyvinyl alcohol (PVA), polymethyl methacrylate = polymethyl methacrylate (PMMA), etc., or JSR brand name ARTON film or Nippon Zeon brand name ZEONOR Examples thereof include norbornene 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 a 2nd gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.
Hereinafter, the holographic recording medium of the present invention will be described in more detail based on specific embodiments. However, the present invention is not limited to the following specific embodiments.

<First embodiment>
FIG. 1 is a schematic cross-sectional view showing the configuration of the holographic recording medium according to the first embodiment. In the holographic recording medium 21 according to the first embodiment, a servo pit pattern 3 is formed on a polycarbonate resin substrate or 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. However, the servo pit pattern 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, providing a gap between the recording layer 4 and the servo pit pattern 3 is effective for forming a recording reference light and information light interference region in the recording layer 4 to a certain size.

  A filter layer 6 is provided on the first gap layer 8, and a holographic recording medium 21 is configured by sandwiching the recording layer 4 between the filter layer 6 and the upper substrate 5 (polycarbonate resin substrate or 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 made of this multilayer deposited film may be directly formed on the first gap layer 8 by vacuum deposition, or a film in which the multilayer deposited film is formed on the substrate is punched into a holographic recording medium shape. May be.

  The holographic recording medium 21 in the present embodiment may have a disk shape or a card shape. In the case of a card shape, there is no need for the servo pit pattern. In the holographic 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, an optical system that can be used for recording and reproducing information on the holographic 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. The servo light is irradiated onto the holographic recording medium 21 by the objective lens 12 so as to focus 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 / exit surface A of the holographic 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 first gap layer 8, the filter layer 6, the recording layer 4, and the upper substrate 5 are transmitted through 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. If 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, Has no effect. Further, since the return light of the servo light reflected by the reflection 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 wavelength plate 15. It becomes circularly polarized light. Through the dichroic mirror 13, the objective lens 12 irradiates the holographic recording medium 21 with information light and recording reference light so as to generate an interference pattern in the recording layer 4. The information light and the recording reference light enter 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 to the bottom surface of the filter layer 6 to 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 holographic recording medium according to the second embodiment. In the holographic 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, etc. 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 holographic recording medium 22 according to the second embodiment. It is that. 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 holographic 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 0.6 mm, the upper substrate 5 is 0.4 mm thick, and the total thickness is about 2.2 mm.

  Next, when information is recorded or reproduced, red servo light and green information light and recording and reproduction reference light are applied to the holographic recording medium 22 of the second embodiment having the above-described structure. Is 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 is emitted from the incident / exit surface A. The emitted return light is used for focus servo, tracking servo, and the like. If 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, Has no effect. 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 exits 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 holographic 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 in the first embodiment, and a description thereof will be omitted.

  By subjecting the holographic recording medium of the present invention to light irradiation for forming interference fringes, radical polymerization reaction (recording reaction) and photodecomposition reaction of the substituent L of the compound represented by the general formula (1) (Expansion reaction) may occur simultaneously, and radical polymerization reaction and photodecomposition reaction may occur separately by irradiating light of different second wavelengths. Details of the light irradiation will be described later. In the present invention, a photodecomposition reaction may occur in the fixing step after the recording light irradiation.

[Information recording method]
Furthermore, the present invention relates to a method for recording information on the holographic recording medium of the present invention. The information recording method of the present invention includes a step of irradiating the holographic recording medium with light having a wavelength different from that of the light irradiated for information recording. Light irradiation for information recording is light irradiation performed for forming interference fringes, and an interference image is usually formed on the recording layer by irradiating the recording layer with information light and reference light. Next, the interference image can be fixed by exposing the recording layer on which the interference image is formed or irradiating the recording layer with fixing light. This exposure or fixing light irradiation may cause a decomposition reaction of the compound represented by the general formula (1). The light irradiation is performed as a separate process from the light irradiation for information recording and the fixing operation. May be caused. In order to perform rapid recording, it is preferable to cause the photodecomposition by a fixing operation.

There is no restriction | limiting in the wavelength of the light irradiated with respect to the holographic recording medium of this invention, For example, you may use the light of any wavelength within the wavelength range of 200-1000 nm. The light waveform may be pulsed light or continuous light. As described above, the light irradiation for information recording and the light irradiation for decomposition of the substituent L are preferably performed using light of different wavelengths. In addition, the light irradiated in a step different from the information recording step (interference fringe forming step) is preferably shorter wave light than the light irradiated for information recording in order not to adversely affect the recording step. For example, a radical polymerization reaction is performed with 523 nm light and a decomposition reaction is caused with 405 nm light, and a radical polymerization reaction is performed with 405 nm light and a decomposition reaction is caused with 365 nm light. It is particularly preferable to use pulsed light for recording and continuous light having a shorter wavelength than the former for light causing a photodegradation reaction. When irradiating the light of the second wavelength, the light of the second wavelength may be irradiated immediately after causing the radical polymerization reaction. For example, several minutes to several hours after the radical polymerization reaction The light of the second wavelength may be irradiated after the time elapses.
Hereinafter, the information recording method of the present invention will be described in more detail.

  As information light, coherent light can be used. An interference image generated by the interference between the information light and the reference light by irradiating the recording medium 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. Can be recorded on the recording layer. Specifically, the information light provided with a two-dimensional intensity distribution and the information light and a reference light having a substantially constant intensity are superposed inside the recording layer, and recording is performed using an interference pattern formed by them. Information can be recorded by creating a distribution of optical properties within the layer. The wavelengths of the information light and the reference light are preferably 400 nm or more, more preferably 400 to 2000 nm, and particularly preferably 400 to 700 nm.

  After performing information recording (interference image formation) by irradiation with information light and reference light, the interference image can be fixed by exposure or irradiation with fixing light. The wavelength of the fixing light is preferably less than 400 nm, more preferably 100 nm or more and less than 400 nm, and particularly preferably 200 nm or more and less than 400 nm.

  Information can be reproduced by irradiating the interference light formed by the above method with reference light. When reading (reproducing) the written information, the recording layer is irradiated with only the reference light in the same arrangement as during recording, and the reproduction light having an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer is obtained. The light is emitted from the recording layer.

Next, an optical recording / reproducing apparatus suitably used for recording and reproducing information on the holographic recording medium of the present invention will be described with reference to FIG.
The optical recording / reproducing apparatus 100 shown in FIG. 4 maintains a spindle 81 to which the holographic recording medium 20 is attached, a spindle motor 82 that rotates the spindle 81, and the rotational speed of the holographic recording medium 20 at a predetermined value. A spindle servo circuit 83 that controls the spindle motor 82 is provided.

  The optical recording / reproducing apparatus 100 records information by irradiating the holographic recording medium 20 with information light and recording reference light, and irradiates the holographic recording medium 20 with reproduction reference light. A pickup 31 for detecting reproduction light and reproducing information recorded on the holographic recording medium 20, and a drive device 84 that enables the pickup 31 to move in the radial direction of the holographic recording medium 20. I have.

  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 holographic recording medium 20 to perform focus servo, and the tracking error detected by the detection circuit 85. Based on the signal TE, an actuator in the pickup 31 is driven to move the objective lens in the radial direction of the holographic recording medium 20 to perform tracking servo, a tracking error signal TE and a controller to be described later. It controls the drive unit 84 based on a command from over La and a slide servo circuit 88 for performing a slide servo for moving the pickup 31 in the radial direction of the holographic recording medium 20.

  The optical recording / reproducing apparatus 100 further decodes the output data of the CMOS or CCD array in the pickup 31 to reproduce the data recorded in the data area of the holographic recording medium 20 or the reproduction signal from the detection circuit 85. A signal processing circuit 89 that reproduces a basic clock from RF and discriminates an address; 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. I have. 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 can be realized.

[Radically polymerizable compound]
Furthermore, this invention relates to the compound represented by General formula (7). The compound represented by the general formula (7) is suitable as a recording material for a holographic recording medium. By using the compound as a recording material, a holographic recording medium capable of recording and reproducing with high sensitivity can be obtained. Details of the compound represented by the general formula (7) are as described above. Preferable embodiments of the compound represented by the general formula (7) include compounds in which X in the general formula (7) represents a hydrogen atom and R ⁷³ represents a hydrogen atom or an alkyl group.

  Hereinafter, the present invention will be further described based on examples. However, this invention is not limited to the aspect shown in the Example.

<Synthesis of Exemplified Compounds M-1 and M-2>
3-hydroxy-5-nitrobenzaldehyde (manufactured by Tokyo Chemical Industry Co., Ltd.) was esterified with acrylic acid chloride and then methylated with a titanium complex. The exemplified compound M-1 was synthesized by esterifying the resulting alcohol moiety.
Exemplified compound M-2 was synthesized in the same manner except that the reagent used for esterification was changed. A synthesis scheme and identification results (NMR data) are shown below.

<M-1>
¹ H NMR (300 MHz, CDCl ₃ ) δ1.63 (d, 3H), 2.11 (s, 3H), 6.11 (d, 1H), 6.27-6.43 (m, 2H), 6.68 (d, 2H), 7.24 (dd, 1H), 7.44 (s, 1H), 8.07 (d, 1H)
<M-2>
¹ H NMR (300 MHz, CDCl ₃ ) δ0.89 (t, 3H), 1.28 (bs, 10H), 1.62 (t, 2H), 1.68 (d, 3H), 2.37 (t, 2H)), 6.13 ( d, 1H), 6.29-6.41 (m, 2H), 6.69 (d, 2H), 7.25 (dd, 1H), 7.44 (s, 1H), 8.08 (d, 1H)

Example 1
-Preparation of composition for holographic recording-
6.4 g of hexamethylene diisocyanate (Mitsui Chemical Polyurethane Co., Ltd., trade name: Takenate T-700), 5.21 g of polypropylene oxide triol (Mitsui Chemical Polyurethane Co., Ltd., trade name MN-300), polyethylene glycol (Tokyo) 4.64 g, manufactured by Kasei Kogyo Co., Ltd., 1.85 g of exemplary compound M-1, photo radical polymerization initiator (ethyl ester of 2,4,6-trimethylbenzoylphenylphosphinic acid, trade name Lucillin TPO-L, BASF Japan Ltd.) 0.16 g (manufactured) and 0.20 g of a cured amine catalyst (manufactured by San Apro Co., Ltd., trade name: U-CAT 410) were mixed under a nitrogen stream to prepare a composition for holographic recording.

(Example 2)
-Preparation of composition for holographic recording-
A holographic recording composition was prepared in the same manner as in Example 1 except that 3.1 g of the exemplified compound M-2 was used instead of 3.1 g of the exemplified compound M-1.

(Example 3)
-Preparation of composition for holographic recording-
A holographic recording composition was prepared in the same manner as in Example 1 except that 3.1 g of Example Compound M-22 was used instead of 3.1 g of Example Compound M-1.

Example 4
-Preparation of composition for holographic recording-
A holographic recording composition was prepared in the same manner as in Example 1 except that 3.1 g of the exemplified compound M-36 was used instead of 3.1 g of the exemplified compound M-1.

(Comparative Example 1)
-Preparation of composition for holographic recording-
6.4 g of hexamethylene diisocyanate (Mitsui Chemical Polyurethane Co., Ltd., trade name: Takenate T-700), 5.21 g of polypropylene oxide triol (Mitsui Chemical Polyurethane Co., Ltd., trade name MN-300), polyethylene glycol (Tokyo) (Made by Kasei Kogyo Co., Ltd.) 4.64 g, 9,9′-biphenylfluorene EO-modified acrylate (Osaka Gas Chemical Co., Ltd., trade name: Ogsol EA0200), photo radical polymerization initiator (2, 4, 6-trimethylbenzoylphenylphosphinic acid ethyl ester, 0.16 g of trade name Lucillin TPO-L, manufactured by BASF Japan Ltd.) and 0.20 g of cured amine catalyst (manufactured by San Apro Co., Ltd., trade name: U-CAT 410) are nitrogenated Mix under air flow to prepare a holographic 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 405 nm was 0.1%, and a first substrate was produced.
An aluminum vapor deposition process was performed on one surface of a 0.5 mm thick glass so that the reflectance by incident light perpendicular to the wavelength of 405 nm was 90%, thereby producing a second substrate.
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 the antireflection treatment.
Next, each of the holographic recording compositions of Examples 1 to 4 and Comparative Example 1 is placed on the first substrate, and the aluminum-deposited surface of the second substrate is not entrained on the holographic recording composition. The first substrate and the second substrate were bonded through a spacer. Then, it was left to stand at 45 degreeC for 24 hours, and each holographic recording medium of Examples 5-8 and the comparative example 2 was produced. The thickness of the formed recording layer was 200 μm.

<Recording on optical recording media and evaluation>
A hologram is written on each holographic recording medium produced using a hologram recording / reproducing tester with a recording spot diameter of 200 μm at the focal position of the recording hologram, and sensitivity (recording energy) and volume shrinkage of the medium are as follows. Was measured. The results are shown in Table 1.
-Measurement of sensitivity-
The irradiation light energy (mJ / cm ² ) at the time of recording was changed, and the change in the error probability (BER: Bit Error Rate) of the reproduction signal was measured. Usually, the luminance of the reproduction signal increases with the increase of irradiation light energy, and the BER of the reproduction signal tends to gradually decrease. Here, the lowest irradiation light energy at which a substantially good reproduced image (BER <10 ⁻³ ) can be obtained is defined as the recording sensitivity of the optical recording medium.
-Volumetric shrinkage of medium-
As a means for analyzing the shrinkage and expansion of a photopolymer, a method of calculating from changes in interference fringes due to plane wave two-beam interference is known. In the FPR (Fringe Plane Rotation) model, the shrinkage of the recording layer occurred between recording and playback due to the difference between the recording angle of the Bragg grating recorded obliquely on the recording medium and the optimum playback angle after recording (or after fixing). Can be evaluated. FIG. 5 shows a conceptual diagram of this model. It is assumed that the shrinkage change that occurs before and after recording is only in the thickness direction.
The change in the inclination of the interference fringes by the FPR model is expressed by the following equation.

Here, Φ and Φ ^* are inclinations of interference fringes during recording and reproduction, respectively, and α is a change rate of the recording layer.

  An interference fringe (6 mmφ) with a weak diffraction efficiency (˜1%) is recorded on a recording medium at a predetermined angle Φ by a 405 nm laser plane wave two-beam interferometer, and then exposure or fixing light irradiation of a recording medium (365 nm laser, spot diameter) 10 mmφ), the photoreactive component of the recording medium was completely consumed, the reproduction angle dependency of the diffraction efficiency was measured, and the angle of the interference fringes was measured again. The shrinkage rate α of the recording medium was estimated based on the formula (1) based on the change in the interference fringe inclination angle during recording and after exposure or fixing. The exemplified compounds used in the examples all have the property of causing no decomposition reaction at the wavelength of the recording laser beam (405 nm) and decomposing the L portion by the fixing operation to release molecules. In contrast, the 9,9'-biphenylfluorene EO-modified acrylate used as the recording material in Comparative Example 2 did not exhibit photodegradability in the above recording reaction and fixing operation.

  From the results of Table 1, the holographic recording media of Examples 5 to 8 using the holographic recording compositions of Examples 1 to 4 are the same as those of Comparative Example 2 using the holographic recording composition of Comparative Example 1. It is recognized that all have excellent recording sensitivity and small volume shrinkage compared to the optical recording medium.

  The holographic recording composition of the present invention is suitable for producing various volume hologram type optical recording media capable of high-density image recording because it can perform higher-density recording.

It is a schematic sectional drawing which shows an example of the holographic recording medium concerning 1st embodiment. It is a schematic sectional drawing which shows an example of the holographic recording medium concerning 2nd embodiment. It is explanatory drawing which shows an example of the optical system which can be used for recording and reproduction | regeneration of the information to a holographic recording medium. It is a block diagram showing an example of the whole structure of the recording / reproducing apparatus used suitably for the recording and reproduction | regeneration of the information to the holographic recording medium of this invention. The conceptual diagram of a FPR model is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower substrate 2 Reflective film 3 Servo pit 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 Holographic recording medium 21 Holographic recording medium 22 Holographic 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 unit 100 Optical recording / reproducing device A Input / output surface FE Focus error signal TE Tracking error signal RF reproduction signal

Claims (13)

The composition for holographic recording containing the compound represented by following General formula (1).
[In General Formula (1), M represents a radical polymerizable group or a substituent containing a radical polymerizable group, A represents a divalent linking group, and L represents a substituent decomposable by light irradiation. ] The holographic recording composition according to claim 1, further comprising a radical photopolymerization initiator. The composition for holographic recording according to claim 2, wherein the substituent represented by L in the general formula (1) can be decomposed by irradiation with light having a wavelength outside the sensitive wavelength range of the photoradical polymerization initiator. object. The composition for holographic recording according to any one of claims 1 to 3, wherein L in the general formula (1) is a substituent that can be directly excited and decomposed by light irradiation. The holographic recording composition according to any one of claims 1 to 4, wherein the compound represented by the general formula (1) is represented by any one of the following general formulas (2) to (6).
[In General Formulas (2) to (6), R ²¹ , R ³¹ , R ⁴¹ , R ⁵¹ , R ⁶¹ and R ⁶² are each independently an alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy Group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group, acyl group, cyano group, halogen group, hydroxyl group, carboxylic acid group, sulfonic acid group or nitro R ²³ , R ²⁴ , R ²⁵ , R ³³ , R ³⁴ , R ³⁵ , R ⁴³ , R ⁴⁴ , R ⁵³ and R ⁵⁴ are each independently a hydrogen atom, an alkyl group, an aryl group, a heterocyclic ring Group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino Represents a sulfonylamino group, an amino group or an acyl group, Z is represents I ⁺ or ^{S + (-R 6), R} 6 represents an aryl group, n1, n2, n3, n4 , n5, n6 and n6 ' Each independently represents an integer in the range of 0 to 5, and M and A have the same definitions as in general formula (1). ] The holographic recording composition according to claim 1, wherein M represents an acryl group, a methacryl group, a styryl group, or a vinyl group. The holographic recording composition according to any one of claims 1 to 6, further comprising a thermosetting component. The holographic recording composition according to claim 7, wherein the thermosetting compound contains a polyfunctional isocyanate and a polyfunctional alcohol. The holographic recording medium which has a recording layer formed from the composition for holographic recording of any one of Claims 1-8. A method for recording information on a holographic recording medium according to claim 9,
The information recording method including the step of irradiating the holographic recording medium with light having a wavelength different from that of light used for information recording. The information recording method according to claim 10, wherein the different wavelength is shorter than a wavelength of light irradiated for information recording. A compound represented by the following general formula (7).
[In the general formula (7), X represents a hydrogen atom or a methyl group, and R ⁷¹ represents an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryl group. Represents an oxycarbonyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an amino group, an acyl group, a cyano group, a halogen group, a hydroxyl group, a carboxylic acid group, a sulfonic acid group, or a nitro group, and R ⁷³ and R ⁷⁴ are each independently A hydrogen atom, alkyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, sulfonylamino group, amino group or Represents an acyl group, and n7 represents an integer in the range of 0 to 5. , A is defined as in general formula (1). ] In the general formula (7), X represents a hydrogen atom, and R ⁷³ represents a hydrogen atom or an alkyl group.