JP4745333B2 - Photosensitive resin composition for volume phase hologram recording and optical information recording medium using the same - Google Patents

Description

  The present invention is a thick film that is quickly cured by an active energy ray (visible laser, ultraviolet ray, electron beam, etc.), has excellent hologram properties such as diffraction efficiency and resolving power, and is excellent in transparency and heat resistance. The present invention relates to a photosensitive resin composition for volume phase hologram recording suitable as a formable volume phase hologram material and an optical information recording medium using the same.

  Conventionally, holograms have been used mainly in the field of stereoscopic image display and security. In the past, wet type materials that require development, such as silver salt photosensitive materials and dichromated gelatin, have been mainly used as the hologram material. Dry photopolymerization hologram recording materials having excellent properties and light resistance have become mainstream. The recording mechanism of the photopolymerization hologram recording material is generally considered as follows, unlike silver salt photosensitive materials and dichromated gelatin. In other words, when the recording material is irradiated with interference fringes consisting of light interference with excellent coherence (coherence), it is applied to the bright part (area where the light intensity is strong) and dark part (area where the light intensity is weak). A substance having different polymerization properties diffuses and moves, and a refractive index modulation structure is formed with the progress of photopolymerization, whereby a hologram is recorded. Polymerization forms of the photopolymerization type hologram recording material include 1) radical polymerization type, 2) cationic polymerization type, and 3) radical / cationic polymerization combined type. Photo radical polymerization type materials are generally used, but although they have high sensitivity, there is a drawback that shrinkage due to the polymerization form is as large as several percent. Currently, the only commercially available photosensitive resin composition among photopolymerizable hologram recording materials is Omnidex manufactured by DuPont.

  In recent years, in an effort to realize a ubiquitous information society, research to use photopolymerization hologram recording materials for holographic data storage has become active all over the world, and various photopolymerization hologram recordings have been made. Material has been proposed. This is because the national projects HDSS (Holographic Data Storage System: 1995-1999) and PRISM (Photorefractive Information Storage Materials: 1994-1998) started in the United States since the mid-1990s are being promoted. This has greatly contributed to the dramatic advancement of such technologies. Conventional recording on an optical disk such as a CD or DVD employs a system in which laser light is collected by a lens and data is recorded on a recording material surface bit by bit. The data storage capacity determined by the size of the focused spot has already reached its theoretical limit, and a new technology is desired to further increase the storage capacity. As one candidate, holography has been attracting attention in recent years.

  Holographic data storage can record volume rather than in-plane recording like CD and DVD, and uses page data for handling data, so it can record large amounts of data that is not comparable to conventional CD and DVD. . Currently, various research institutes are actively developing materials and recording technologies toward the practical use of WORM (Write Once Read Many) type hologram optical discs capable of recording 1 TB (terabyte). The basic design concept of the holographic data storage material is the same as the above-described photopolymerization hologram recording material for stereoscopic image recording and security applications. However, when used in holographic data storage applications, there are extremely strict requirements for materials for sensitivity to light sources and cure shrinkage. Typical examples of the photosensitive resin composition for holographic data storage include those of US-Aprilis Inc., which has flown through Polaroid Corporation, and those of Inphase Corporation, which has flowed through Lucent Technology Corporation. Can be mentioned.

  First, as described in Patent Documents 1 and 2, for example, US Aprilis Co., Ltd. uses a CROP (Cationic Ring-Opening Polymerization) monomer having an oxirane or oxetane ring to perform pre-light irradiation. Discloses a material with reduced polymerization shrinkage. However, although cationic polymerization has little oxygen inhibition like radical polymerization, there is a problem that sensitivity in a long wavelength region is slightly inferior. On the other hand, in US Inphase, for example, as described in Patent Document 3, 4 or 5, by using cyclohexene oxide and a swelling agent (diphenylfuran carboxylate) in combination, the polymerization shrinkage is 1% or less. Very small materials are disclosed. However, here too, a cationic ring-opening polymerizable monomer is used and the entire surface is exposed before or after recording to suppress cure shrinkage, but no proposal for improving sensitivity has been made. For the practical application of holographic data storage, further improvement in photosensitivity, reduction in curing shrinkage, and improvement in heat resistance are desired.

US Pat. No. 5,759,721 US Pat. No. 6,784,300 US Pat. No. 3,993,485 US Pat. No. 6,124,076 JP 2000-086914 A JP-A-5-94014 JP-A-9-106242 JP 2004-123873 A

  Patent Documents 6 and 7 describe a photosensitive resin composition for hologram in which a radical polymerizable ethylene monomer, a photopolymerization initiator and an epoxy resin are blended. In this composition, a radical-polymerizable ethylene monomer is preferentially polymerized from a bright part of an interference fringe during hologram exposure by a laser, and a hologram is formed by utilizing the phenomenon that the ethylene monomer moves to a bright part. . The epoxy resin is then cured. Patent Document 8 describes a soluble aromatic copolymer aromatic copolymer having a structural unit of a divinyl aromatic compound and a structural unit of a monovinyl aromatic compound, but there is no teaching about hologram use.

As a photosensitive resin composition capable of recording a volume phase hologram, a number of material systems have been studied and disclosed so far, but a photosensitive resin composition capable of satisfying both photosensitivity and cure shrinkage simultaneously. Never before. When a volume phase hologram recording resin composition is used for holographic data storage, a high level is particularly required for both photosensitivity and low cure shrinkage.
The present invention has been accomplished in view of the above circumstances, and has a diffraction phase, resolution, transparency, heat resistance and the like required for a volume phase hologram, and is particularly excellent in photosensitivity. An object of the present invention is to provide a recording resin composition and an optical information recording medium obtained from the composition. Of course, the hologram obtained by the present invention should be used for applications other than holographic data storage, such as applications where its usefulness is demonstrated by using holograms such as diffraction gratings, interference filters, lenses, and head-up displays. Can do.

  As a result of intensive studies on the above problems, the inventors of the present invention incorporated a soluble polyfunctional vinyl aromatic copolymer and a photo-radically polymerizable compound copolymerizable therewith into the composition to further improve the photosensitivity. At the same time, it was found that shrinkage after curing can be further suppressed, and the present invention has been completed.

（式中、Ｒ^１は炭素数６〜３０の芳香族炭化水素基を示す。）The present invention provides a soluble aromatic copolymer (A) having a structural unit of a divinyl aromatic compound and a structural unit of a monovinyl aromatic compound, and containing 10 mol% or more of a structural unit represented by the following formula (a1). A radically polymerizable compound (B) and a photopolymerization initiator (C) copolymerizable with the soluble aromatic copolymer (A), a polymer binder (D) and / or a plasticizer (E). A photosensitive resin composition for volume phase hologram recording, comprising 5 to 60% by weight of a soluble aromatic copolymer (A).

(In the formula, R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.)

  The present invention also provides a volume phase hologram recording optical information recording medium in which a recording layer comprising the above-described photosensitive resin composition is formed on one support or between two supports. Furthermore, the present invention is a volume phase hologram obtained by recording interference fringes formed from energy rays having excellent coherency on the optical information recording medium. Furthermore, the present invention is a method for producing a volume phase hologram, wherein the recording medium is exposed and recorded with interference fringes formed from energy rays having excellent coherency.

  The photosensitive resin composition of the present invention is a volume phase-type hologram recording resin composition used for recording interference fringes composed of light interference having excellent coherence as fringes having different refractive indexes, and is a soluble aromatic fragrance. Group copolymer (A), radical photopolymerizable compound (B) and photopolymerization initiator (C) as essential components, and further a polymer binder (D) or plasticizer (E) or both as essential components Including.

First, the soluble aromatic copolymer (A) will be described.
The soluble aromatic copolymer (A) is obtained by copolymerizing a divinyl aromatic compound and a monovinyl aromatic compound, and has a structural unit containing a reactive vinyl group in the side chain represented by the formula (a1). It has 10 mol% or more. The structural unit represented by the formula (a1) is derived from a divinyl aromatic compound as a monomer. Advantageously, the structural unit represented by the formula (a1) has an average of 3 or more per molecule. And a soluble aromatic copolymer (A) is a well-known compound as described in patent document 8, etc., and is suitably manufactured by the method as described there.

  Examples of the divinyl aromatic compound include m-divinylbenzene, p-divinylbenzene, 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene, 1,3- Divinylnaphthalene, 1,8-divinylnaphthalene, 1,4-divinylnaphthalene, 1,5-divinylnaphthalene, 2,3-divinylnaphthalene, 2,7-divinylnaphthalene, 2,6-divinylnaphthalene, 4,4′- Divinylbiphenyl, 4,3′-divinylbiphenyl, 4,2′-divinylbiphenyl, 3,2′-divinylbiphenyl, 3,3′-divinylbiphenyl, 2,2′-divinylbiphenyl, 2,4-divinylbiphenyl, 1,2-divinyl-3,4-dimethylbenzene, 1,3-divinyl-4,5,8-tri Chill naphthalene, 2,2' but divinyl-4-ethyl-4'-propyl biphenyl, or the like can be used, but is not limited thereto. These can be used alone or in combination of two or more.

  Preferred specific examples of the divinyl aromatic compound include divinylbenzene (both m- and p-isomers), divinylbiphenyl (including each isomer), and divinyl in terms of cost and heat resistance of the obtained polymer. There is naphthalene (including each isomer). More preferred are divinylbenzene (both m- and p-isomers) and divinylbiphenyl (including each isomer). In particular, divinylbenzene (both m- and p-isomers) is most preferably used.

  Examples of the monovinyl aromatic compound include styrene, vinyl naphthalene, vinyl biphenyl and the like and derivatives thereof. Examples of the derivatives include compounds in which an aromatic ring is substituted with a substituent such as an alkyl group, an alkoxy group, a halogen, or a phenyl group, and compounds in which the above substituent is substituted at the α-position or β-position of the vinyl group. In addition, aromatic olefins such as indene and acenaphthylene and derivatives thereof can also be used as monovinyl aromatic compounds. These can be used alone or in combination of two or more.

  Examples of styrene derivatives include methyl styrene, ethyl styrene, propyl styrene, butyl styrene, pentyl styrene, hexyl styrene, cyclohexyl styrene, ethoxy styrene, propoxy styrene, butoxy styrene, pentoxy styrene, hexoxy styrene, cyclohexoxy styrene, phenoxy styrene. Etc. can be used. These substituents can be substituted at the o-, m-, or p-position with respect to the vinyl group, and when they can have side chains, they can be linear or side chain alkyl groups or alkoxy groups.

  As indene or a derivative thereof, for example, indene, alkyl substituted indene having 1 to 6 carbon atoms, alkoxy substituted indene having 1 to 6 carbon atoms, or the like can be used. Examples of acenaphthylene or derivatives thereof include acenaphthylene, alkyl-substituted acenaphthylene having 1 to 6 carbon atoms, phenyl-substituted acenaphthylene, halogen-substituted acenaphthylene such as chlorine and bromine, and the like.

  The monovinyl aromatic compound is not limited to these. Among these monovinyl aromatic compounds, a nuclear alkyl-substituted aromatic vinyl compound and an α-alkyl-substituted aromatic vinyl compound are preferable in that the amount of indane structure generated in the skeleton of the copolymer during polymerization is large. Preferred examples include ethyl vinyl benzene (both m- and p-isomers), ethyl vinyl biphenyl (including each isomer), and ethyl vinyl naphthalene (each) in terms of cost and heat resistance of the resulting polymer. Including isomers).

  The soluble aromatic copolymer (A) is obtained by copolymerizing the divinyl aromatic compound and the monovinyl aromatic compound as described above, but other monomers may be used as necessary. Examples of such other monomers include trivinyl aromatic compounds, diene compounds such as butadiene and isoprene, alkyl vinyl ethers, isobutene, and diisobutylene. These other monomers are used in a range of less than 30 mol% of the total monomers. The divinyl aromatic compound is used so as to be 20 mol% or more, preferably 40 to 80 mol% of the total monomer, and the monovinyl aromatic compound is 10 mol% or more, preferably 20 to 60 mol% of the total monomer. Used to be.

  A preferable example of the polymerization method for producing the soluble aromatic copolymer (A) is the method described in Patent Document 8. For example, it is the following method.

（式中、Ｒ¹は水素原子又は炭素数１〜６の１価の炭化水素基を示し、Ｒ²はｐ価の芳香族炭化水素基又は脂肪族炭化水素基を示し、Ｚはハロゲン原子、炭素数１〜６のアルコキシル基又はアシルオキシル基を示し、ｐは１〜６の整数を示す。一分子中に、複数のＲ¹及びＺがある場合、それぞれは同一であって、異なってもよい）で表される開始剤により、ジビニル芳香族化合物（ａ）を２０〜１００モル％含有してなる単量体成分を２０〜１２０℃の温度でカチオン重合させる。In an organic solvent, Lewis acid catalyst and the following general formula (1)

(In the formula, R ¹ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, R ² represents a p-valent aromatic hydrocarbon group or aliphatic hydrocarbon group, Z represents a halogen atom, An alkoxyl group or an acyloxyl group having 1 to 6 carbon atoms, and p represents an integer of 1 to 6. When there are a plurality of R ¹ and Z in one molecule, they may be the same or different. The monomer component containing 20 to 100 mol% of the divinyl aromatic compound (a) is cationically polymerized at a temperature of 20 to 120 ° C.

  As the organic solvent, one or more organic solvents having a dielectric constant of 2 to 15 are preferable, and a quaternary ammonium salt, an ether compound having 3 or more carbon atoms, a thioether compound having 3 or more carbon atoms, or a compound having 2 or more carbon atoms. It is also preferable to have a donor component selected from the group consisting of sulfoxide compounds. Any organic solvent can be used without particular limitation as long as it is a compound that does not essentially inhibit cationic polymerization, and it can be used alone or in combination of two or more as a polymerization solvent so that the dielectric constant falls within the range of 2 to 15. It is good to use. As organic solvents, methyl chloride, dichloromethane, n-propyl chloride, n-butyl chloride, chloromethane, trichloromethane, tetrachloromethane, chloroethane, dichloroethane, trichloroethane, tetrachloroethane, chloroethylene, dichloroethylene, chlorobenzene, chlorobenzene, dichlorobenzene , Halogenated hydrocarbons such as trichlorobenzene; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, propylbenzene, butylbenzene; ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, etc. Linear aliphatic hydrocarbons; branched aliphatic carbonization such as 2-methylpropane, 2-methylbutane, 2,3,3-trimethylpentane, 2,2,5-trimethylhexane Motorui; and paraffin oils such as petroleum distillates and made water 添精; cyclohexane, methylcyclohexane, cycloaliphatic hydrocarbons such as ethylcyclohexane. Of these, dichloroethane, toluene, xylene, pentane, hexane, heptane, octane, 2-methylpropane, 2-methylbutane, methylcyclohexane and ethylcyclohexane are preferred. From the viewpoint of balance of polymerizability and solubility and availability, dichloroethane, toluene, xylene, n-hexane, cyclohexane, heptane, methylcyclohexane and ethylcyclohexane are more preferable. The amount of the organic solvent used is usually determined so that the concentration of the polymer is 1 to 50 wt%, preferably 5 to 35 wt%, in consideration of the viscosity of the polymer solution obtained and ease of heat removal. . A dielectric constant of less than 2 is not preferred because the polymerization activity is low, and a dielectric constant of more than 15 is not preferred because gelation tends to occur during polymerization. In addition, the polymerization is performed by using 0.001 to 100 moles, preferably 0.3 to 50 times moles of a Lewis acid catalyst and 0.1 parts of a donor component to an initiator represented by the general formula (1) with respect to 1 mole of the initiator. It is also preferred to use in the range of 001 to 10 mol and polymerize in an organic solvent in which the soluble aromatic copolymer is dissolved.

Specific examples of Lewis acid catalysts used as polymerization catalysts are boron bromide (III), boron chloride (III), aluminum bromide (III), aluminum fluoride (III), aluminum chloride (III), iodine Aluminum (III) iodide, gallium bromide (III), gallium chloride (III), indium bromide (III), indium chloride (III), indium fluoride (III), indium iodide (III), thallium bromide ( III), thallium fluoride (III), silicon bromide (IV), silicon chloride (IV), silicon fluoride (IV), silicon iodide (IV), germanium bromide (IV), germanium chloride (IV), Germanium (IV) iodide, tin (IV) bromide, tin (IV) chloride, tin (IV) fluoride, tin (IV) iodide, lead (IV) fluoride, antimony bromide (III), antimony chloride (III), antimony chloride (V), antifluoride Mon (III), antimony fluoride (V), antimony iodide (III), bismuth (III) bromide, bismuth chloride (III), bismuth fluoride (III), bismuth iodide (III), titanium chloride (IV ), Titanium bromide (IV), BF ₃ .OEt ₂ , tungsten chloride (VI), vanadium chloride (V), iron chloride (III), zinc bromide (II), etc .; Et ₂ AlCl, EtAlCl _And organometallic halides such as ₂ . Said catalyst is not specifically limited, It can use individually or in combination of 2 or more types. Among the above catalysts, boron (III) bromide, boron chloride (III), tin (IV) chloride, tin (IV) bromide, tin (IV) chloride, tin (IV) fluoride, tin iodide (IV) ) And antimony chloride (V) are preferable in terms of control of the branched structure and polymerization activity. More preferred are boron (III) chloride and tin (IV) chloride, and particularly preferred is tin (IV) chloride.

  As the initiator represented by the general formula (1), (1-chloro-1-methylethyl) benzene, 1,4-bis (1-chloro-1-methylethyl) benzene, 1,3-bis (1 -Chloro-1-methylethyl) benzene, 1,3,5-tris (1-chloro-1-methylethyl) benzene, 1,3-bis (1-chloro-1-methylethyl) -5- (tert- Butyl) benzene, 1-chloroethylbenzene, 1-bromoethylbenzene and the like. Preference is given to bis (1-chloro-1-methylethyl) benzene, 1-chloroethylbenzene and 1-bromoethylbenzene.

  The polymerization for producing the soluble aromatic copolymer (A) is carried out in a temperature range of 20 to 100 ° C. If the polymerization reaction is carried out at a temperature lower than 20 ° C., the heat resistance of the produced copolymer is lowered, which is not preferable. If the temperature exceeds 100 ° C., the reaction rate is too high, so that the reaction is difficult to control and an insoluble gel due to crosslinking. It is not preferable because the generation of is easy to occur. The method for recovering the copolymer after the termination of the polymerization reaction is not particularly limited. For example, a commonly used method such as a steam stripping method or precipitation with a poor solvent may be used.

（式中、Ｒ⁴は、炭素数６〜３０の芳香族炭化水素基を示す。）で表されるモノビニル芳香族化合物由来の構造単位を有することが好ましく、式（a1）で表される構造単位と式（a2）で表される構造単位の存在モル比（a1）／[（a1）＋（a2）]が０．１以上である。好ましくはが０．３以上であり、特に好ましくは０．５以上である。０．１未満であると記録したホログラムが時間とともに消失する。The soluble aromatic polymer (A) is represented by the following formula (a2)

(Wherein R ⁴ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms) and preferably has a structural unit derived from a monovinyl aromatic compound represented by formula (a1). The existence molar ratio (a1) / [(a1) + (a2)] of the unit and the structural unit represented by the formula (a2) is 0.1 or more. Preferably it is 0.3 or more, and particularly preferably 0.5 or more. If it is less than 0.1, the recorded hologram disappears with time.

（但し、Yは飽和若しくは不飽和の脂肪族炭化水素基又は芳香族炭化水素基又はベンゼン環に縮合した芳香族環若しくは置換芳香族環を示し、ｎは0〜4の整数である。）で表されるインダン構造単位を０〜２０モル％有することが好ましい。インダン構造は上記の製造方法により共重合体（A）を製造する際、特定の溶媒、触媒、温度等の製造条件下で製造を行うことにより、成長ポリマー鎖末端の活性点がジビニル芳香族化合物及びモノビニル芳香族化合物由来の構造単位の芳香族環を攻撃することにより生成するものである。インダン構造は全ての単量体の構造単位に対して０．０１モル％以上存在することが好ましく。より好ましくは０．１モル％以上であり、更に好ましくは１モル％以上である。特に好ましくは３モル％以上である。最も好ましくは５モル％以上である。本発明の多官能ビニル芳香族共重合体の主鎖骨格中に上記インダン構造が存在しないと、耐熱性と溶剤への可溶性が不足するので好ましくない。Furthermore, the soluble aromatic polymer (A) has the following general formula (2) in its main chain skeleton.

(Y represents a saturated or unsaturated aliphatic hydrocarbon group or aromatic hydrocarbon group or an aromatic ring or substituted aromatic ring condensed with a benzene ring, and n is an integer of 0 to 4). It is preferable to have 0-20 mol% of indane structural units represented. The indane structure is produced under the production conditions such as a specific solvent, catalyst, and temperature when the copolymer (A) is produced by the above production method, so that the active point of the growing polymer chain end is divinyl aromatic compound. And an aromatic ring of a structural unit derived from a monovinyl aromatic compound. The indane structure is preferably present in an amount of 0.01 mol% or more based on the structural units of all monomers. More preferably, it is 0.1 mol% or more, More preferably, it is 1 mol% or more. Especially preferably, it is 3 mol% or more. Most preferably, it is 5 mol% or more. If the indane structure is not present in the main chain skeleton of the polyfunctional vinyl aromatic copolymer of the present invention, heat resistance and solubility in a solvent are insufficient, which is not preferable.

The number average molecular weight (in terms of standard polystyrene obtained using gel permeation chromatography, hereinafter referred to as Mn) of the soluble aromatic copolymer (A) is preferably 400 to 30000. More preferably, it is 400-10000, More preferably, it is 500-5000. If the Mn is less than 400, the viscosity of the copolymer (A) is too low, and the workability is not good. Further, if Mn is 30000 or more, it is not preferable because rapid mass transfer during hologram recording is inhibited.
The value of the molecular weight distribution (Mw / Mn) of the soluble aromatic copolymer (A) is preferably 10 or less. If Mw / Mn exceeds 10, problems such as deterioration in processing characteristics of the soluble polyfunctional vinyl aromatic copolymer and generation of gel are not preferable.

  The soluble aromatic copolymer (A) has polymerizability because it has a structural unit represented by the formula (a1) having an unsaturated bond. And since it is soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform, when a specific part is polymerized as a composition, it can move so as to eliminate the concentration gradient.

Next, the photoradical polymerizable compound (B) will be described.
The radical photopolymerizable compound (B) used in the present invention is a radical polymerization initiator that is compatible with the soluble aromatic copolymer (A) and the polymer binder (D) or plasticizer (E) described later. Those which are polymerized by the active radical species generated from the catalyst are preferred. Advantageously, a monomer having at least one polymerizable functional group such as (meth) acryloyl group, vinyl group, allyl group or the like in the molecule can be preferably used. As the radical photopolymerizable compound (B), two or more radical photopolymerizable compounds having different polymerizability and refractive index may be used.

  When light is irradiated, the components that polymerize first (in the bright part of the interference light) are mainly the radical photopolymerizable compound (B) and the soluble aromatic copolymer (A). The cured product produced at this time is mainly composed of a polymer of the soluble aromatic copolymer (A) and a copolymer of the photoradical polymerizable compound (B) and the soluble aromatic copolymer (A). It is estimated that However, recording can be performed for a moment in a system in which no soluble aromatic copolymer (A) is present or a system in which an aromatic oligomer having no reactive vinyl group is used in place of the soluble aromatic copolymer (A). However, since the recording gradually disappears after standing for a while after that, the soluble aromatic copolymer (A) reacts with the radical photopolymerizable compound (B) to play a role in fixing the recording. . Therefore, the refractive index difference is considered to occur between the following components. 1) When polymer binder (D), plasticizer (E) or both are used, the cured product of soluble aromatic copolymer (A) and photoradically polymerizable compound (B) is concentrated in the bright part. In the dark portion (cured product concentrated phase), the polymer binder (D), the plasticizer (E) or both are concentrated (non-cured product concentrated phase) in the dark part, and a difference in refractive index occurs. 2) When using two or more types of photoradically polymerizable compounds (B) and using photoradically polymerizable compounds (B2) that are less reactive than those that react in bright parts, the dark parts are photoradical polymerized. The polymer of the functional compound (B2) and the polymer binder (D), the plasticizer (E) or both are concentrated (dark cured product and non-cured product concentrated phase), and a difference in refractive index occurs. Therefore, in the case of 1), the refractive index of the cured product concentrated phase and the non-cured product concentrated phase must be different from each other by a certain value or more. In the case of 2), the refractive index of the cured product concentrated phase needs to be different from the dark cured product and the non-cured product concentrated phase by a certain value or more. The refractive index is adjusted by selecting the type and amount of the radical photopolymerizable compound (B), the polymer binder (D), and the plasticizer (E).

  Examples of the photo-radical polymerizable compound (B) include methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, ethyl carbitol (meth) acrylate phenoxyethyl (meth) Monofunctional (meth) acrylates such as acrylate, nonylphenoxyethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, isobornyl (meth) acrylate, tribromobenzyl (meth) acrylate, acryloylmorpholine; (meth) acryloxypropyl Silicon-containing (meth) acrylates such as tris (methoxy) silane; di (meth) acrylates of bisphenol compound alkylene oxide adducts such as bisphenol F, bisphenol A, and hydrogenated bisphenol A Chryrates: polyfunctional (meth) acrylates such as trimethylolpropane tri (meth) acrylate, dipentaerythritol pentaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylol tetraacrylate, dipentaerythritol hexaacrylate; ethylene glycol di Glycidyl ether-epoxy (meth) acrylate, propylene glycol diglycidyl ether-epoxy di (meth) acrylate, phenol glycidyl ether-epoxy (meth) acrylate, resorcin diglycidyl ether-epoxy (meth) acrylate, bisphenol A diglycidyl ether-epoxy di ( (Meth) acrylate, bis (4-hydroxyphenyl) sulfide Glycidyl ether-epoxy (meth) acrylate, phenol novolac type epoxy resin- (meth) acrylate, cresol novolac type epoxy resin- (meth) acrylate, bisphenol (for example, bisphenol A, bisphenol F, etc.) type epoxy resin- (meth) acrylate , Biphenol (for example, 3,3 ′, 5,5′-tetramethylbiphenol, etc.) type epoxy resin- (meth) acrylate, tris (2,3-epoxypropyl) isocyanurate- (meth) acrylate, etc. Epoxy (meth) acrylates that are a reaction product of an epoxy compound and (meth) acrylic acid; acrylamides such as N, N-dimethylacrylamide, N, N-diethylacrylamide; vinylbenzene, divinylbenzene, vinylnaphtha , Vinyl biphenyl, acenaphthylene, styrene, p-chlorostyrene, N-vinylcarbazole, N-vinylpyrrolidone, N-vinylcaprolactam and other monofunctional vinyl compounds; diarylidene pentaerythritol, diallyl phthalate, diallyl isophthalate , Allyl group-containing compounds such as ethylene glycol diallyl carbonate, trimellitic acid triallyl ester, triallyl (iso) cyanurate; or urethane (meth) acrylates, polyurethane (meth) acrylates, thiourethane acrylates, polythiourethanes Acrylates, ester acrylates, polyester (meth) acrylates, polyether (meth) acrylates, sulfur-containing (meth) acrylates, sulfur-containing polyfunctional (meth) acrylates , Various known polymerizable monomers or oligomers thereof, such as, other various photopolymerizable oligomers and the like. Of the above, (meth) acrylate monomers having relatively good photocurability are preferred. In particular, the hologram recording property is good in a combination of (meth) acrylates containing at least bifunctional (meth) acrylates.

  The photoradically polymerizable compound (B) is blended in the composition and polymerized and cured when irradiated with light, but a part thereof is copolymerized and cured with the soluble aromatic copolymer (A).

Next, the photopolymerization initiator system (C) will be described.
Examples of the photopolymerization initiator system (C) include He—Ne laser (633 nm), Ar laser (515, 488 nm), YAG laser (532 nm), He—Cd laser (442 nm), and blue DPSS laser (405 nm). An initiator system that absorbs visible laser light to generate radicals, and the active radical species polymerizes the soluble aromatic copolymer (A) and the photoradically polymerizable compound (B), which are essential components of the present invention. I just need it. In addition, a dye sensitizer can be added for the purpose of further increasing sensitivity at each laser light wavelength.

  Examples of the photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-diethoxy-2-phenylacetophenone, benzophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1- ON, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,2-dimethoxy-1,2 -Diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4-hydroxyethoxy) -phenyl-2-hydroxy -2-Methyl-1-propan-1-one 2-Methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, bis ( 2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phos Fin oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium, 4,4-bisdimethylaminobenzophenone , Methyl benzoisoformate, benzyldimethyl ketal, benzoylbenzoic acid, 4-dimethyl Examples include ethyl aminobenzoate, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, camphorquinone, benzyl, 4,4'-diethylaminobenzophenone and the like. Examples of commercially available products of the photo radical polymerization initiator include Irgacure 184, 369, 500, 651, 819, 907, 784, 2959, Darocur 116, 1173 (manufactured by Ciba Specialty Chemicals Co., Ltd.).

  Moreover, you may use a thermal-polymerization initiator in the form used together with the said photoinitiator. Examples of the thermal polymerization initiator used in combination include 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, 2,2′-azobisisovaleronitrile, 2 , 2′-azobis (2,4-dimethylvaleronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, benzoyl peroxide, 2,4- Examples thereof include dichlorobenzoyl peroxide.

  The amount of these initiators to be added varies depending on the type of initiator, the type of compound to be blended, and the composition ratio, and thus cannot be determined unconditionally. . Especially preferably, it is the range of 0.1-8 weight%. If it is less than 0.05% by weight, curability is inferior, unreacted substances remain, and recording stability becomes poor. On the other hand, if it exceeds 30% by weight, the degree of polymerization becomes low, the cured product becomes too soft, and in some cases, the transparency is lowered. When the content is 0.1 to 8% by weight, a photosensitive resin composition having particularly good curability and good hologram characteristics can be provided.

  When using a dye sensitizer, any dye sensitizer that absorbs light in the visible region may be used. (Thio) xanthene dyes, cyanine dyes, merocyanine dyes, squarylium dyes, thiopyrylium Well-known compounds such as salt dyes, quinoline dyes, (base) styryl dyes, (keto) coumarin dyes, rhodocyanine dyes, porphyrin dyes, and oxazine dyes can be mentioned. These may be used alone or in combination of two or more.

  In the present invention, for example, the polymer binder (D) can be used for the purpose of improving the film formability and film strength which can cope with a thick film, or improving the environmental resistance after hologram recording. The polymer binder (D) used for this purpose is preferably one having high transparency and high compatibility with the soluble aromatic copolymer (A). For example, polystyrene and derivatives thereof, methyl methacrylate-styrene copolymer (MS resin), styrene-acrylonitrile copolymer (AS, SAN resin), poly (4-methylpentene-1) (TPX resin), polycycloolefin ( COP resin), polydiethylene glycol bisallyl carbonate (EGAC resin), polythiourethane (PTU resin), polymethyl vinyl ether (PMVE resin), polysulfone resin, polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, acetyl cellulose and the like. The polymer binder (D) may have a reactive group such as a cationic polymerizable group in its side chain or main chain. One or more of these can be blended.

  In the present invention, the plasticizer (E) may be used as a compound that improves the mass transfer of the soluble aromatic copolymer (A) and the radically polymerizable compound (B) or the compatibility of the photosensitive resin composition. it can. As the plasticizer (E), those that are highly compatible with the aromatic copolymer (A) and the photo-radical polymerizable compound (B), and liquid that facilitates mass transfer during recording are preferably selected. It is. For example, sebacic acid esters such as dimethyl sebacate, diethyl sebacate, dibutyl sebacate, bis (2-ethylhexyl) sebacate; adipic acid esters such as dimethyl adipate, diethyl adipate, dibutyl adipate, bis (2-ethylhexyl) adipate Phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, bis (2-ethylhexyl) phthalate, diisodecyl phthalate; trimethyl phosphate, triethyl phosphate, tributyl phosphate, (2-ethylhexyl) phosphate, triphenyl phosphate, cresyl diphenyl Known plasticizers (E) such as orthophosphates such as phosphate and tricresyl phosphate can be used. These can be used in one or more types.

  Furthermore, if necessary, thermal polymerization inhibitors, chain transfer agents, antioxidants, silane coupling agents, coating surface improvers, surface conditioners, plasticizers, antifoaming agents, surfactants, colorants, storage stability Agents, UV absorbers, thickeners and other known additives (F) can also be added.

  When the resin composition in the present invention is solid, or when it is difficult to apply due to high viscosity, a solvent (G) can be used to dissolve or disperse the resin composition. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; petroleum solvents such as toluene and xylene; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; ethanol, methanol And alcohols such as isopropanol and butanol; ethers such as tetrahydrofuran and dioxane; and halogenated hydrocarbons such as dichloromethane and chloroform. The solvent is preferably blended in an amount of 200 parts by weight or less per 100 parts by weight of the resin solid component, and more preferably 100 parts by weight or less. In order to increase the efficiency of the subsequent drying step, the boiling point is preferably 100 ° C. or lower. The solvent (G) is a component for dissolving or dispersing the resin composition, and is excluded from the calculation of the content of each component, not a constituent component of the resin composition in the present invention.

  The components used as essential components in the composition of the present invention are (A) to (C) and (D) or (E), but it is preferable to use both (D) and (E). . Moreover, in description of the said component, another component (F), etc., and a solvent (G), these are not limited to what was illustrated.

<Composition of hologram recording material>
In the photosensitive resin composition for volume phase hologram recording of the present invention, each component is preferably blended in the following proportions with respect to the total weight of the composition (excluding the solvent).
5 to 60% by weight of soluble aromatic copolymer (A), preferably 10 to 40% by weight
5 to 50% by weight, preferably 10 to 40% by weight of the radically polymerizable compound (B)
The photopolymerization initiator (C) is 0.05 to 30% by weight, preferably 1 to 10% by weight (when a dye sensitizer is added, the dye sensitizer is 0.01 to 10% by weight, The total amount with initiator does not exceed 30% by weight)
0-50% by weight of polymer binder (D), preferably 10-40% by weight
0 to 40% by weight of plasticizer (E), preferably 10 to 35% by weight
Total of polymer binder (D) and plasticizer (E): 20 to 80% by weight, preferably 30 to 70% by weight

<Production of hologram recording medium>
Production of a hologram recording medium from the photosensitive resin composition of the present invention is carried out by using a known photosensitive coating composition such as a spin coater, a roll coater, a bar coater, etc. A method of applying a hologram recording medium on a substrate such as a polymethylmethacrylate plate or a polyester film so as to have a dry film thickness of 1 to 1000 μm and producing a hologram recording medium through a drying step as necessary is suitable. At this time, a protective layer may be provided as an oxygen blocking film on the photosensitive resin assembly layer. As the protective layer, for example, a film equivalent to the above substrate, a film such as polyolefin, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, or polyethylene terephthalate, glass, or the like can be used. When applying the photosensitive solution, it may be diluted with an appropriate solvent as necessary. In that case, drying is required after coating on the substrate.

<Light source and recording method for hologram recording>
The recording layer produced as described above can be subjected to interference exposure by a conventionally known method to form a volume phase hologram. For example, interference fringes are recorded by two-beam interference fringe exposure by a normal holographic exposure apparatus using laser light or light having excellent coherence (coherence) (for example, light having a wavelength of 300 to 1200 nm). At this stage, diffracted light by the recorded interference fringes is obtained and can be made into a hologram.
As a light source suitable for the hologram recording material of the present invention, a He—Ne laser (633 nm), an Ar laser (515, 488 nm), a YAG laser (532 nm), a He—Cd laser (442 nm), or a blue DPSS laser (405 nm). Etc. are available. Further, after hologram recording by the above laser or the like, the entire surface is left unreacted by applying ultraviolet (UV) irradiation with a xenon lamp, mercury lamp, metal halide lamp or the like, or applying heat of about 60 ° C. to the optical recording composition film. Polymerization of the partially radically polymerizable compound and phase separation accompanying mass transfer are promoted, and a hologram having more excellent hologram characteristics can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The symbols used in the examples are as follows.
DVB: Divinylbenzene
DVB570: Mixed monomer with a component ratio of DVB and ethylvinylbenzene of 57:43 (manufactured by Nippon Steel Chemical Co., Ltd.)
S2EG: Bis (2-methacryloylthioethyl) sulfide (manufactured by Sumitomo Seika),
TCP: tricresyl phosphate (manufactured by Shin Nippon Chemical Co., Ltd.)
MS-200: methyl methacrylate-styrene (20:80) copolymer,
MS-600: methyl methacrylate-styrene (60:40) copolymer.

The evaluation of the hologram and the photosensitive resin composition in this example was performed by the following method.
<Evaluation of hologram>
* Evaluation of diffraction efficiency The diffraction efficiency of a transmission hologram was calculated by the following equation using the value obtained by reading the diffracted light from a linearly polarized He-Ne laser (632.8 nm) with an optical power meter.
Diffraction efficiency (%) = (diffracted light intensity / incident light intensity) × 100
* Evaluation of environment resistance Change in diffraction efficiency and transparency after 1 month of recording (stored at 60 ° C) (○: No change, △: Slight change, ×: Change)
* Volume shrinkage of photosensitive resin composition The cure shrinkage of the photosensitive resin composition can be calculated by the following equation by measuring the density of the resin composition before and after curing. A spot UV irradiation device was used as a light source, and a sample having a thickness of 50 μm was irradiated with 6 mW / cm ² of UV under air.
Curing shrinkage (%) = (1−liquid density / film density) × 100

Synthesis example 1
Divinylbenzene 1.75 mol (258.9 ml), ethylvinylbenzene 1.30 mol (186.3 ml), 1-chloroethylbenzene (289.1 mmol) in toluene solution (toluene 1806 ml, monomer concentration: 1.31 mol / ml, Dielectric constant: 2.38) 2282 ml was put into a 3000 ml flask and heated to 30 ° C. Further, 21.7 ml of a 12.64 mmol SnCl ₄ toluene solution (concentration: 0.584 mmol / ml) was added and reacted for 4 hours. After the polymerization reaction was stopped with a small amount of methanol bubbled with nitrogen, the reaction mixture was poured into a large amount of methanol at room temperature to precipitate a soluble aromatic copolymer. The obtained copolymer was washed with methanol, filtered, dried and weighed to obtain 171.62 g of a soluble aromatic copolymer (yield: 42.9 wt%). The polymerization activity was 3.39 (g polymer / mmol Sn · hr). Mw of the obtained copolymer was 6930, Mn was 1990, and Mw / Mn was 3.48.

Synthesis example 2
1.51 mol (223.4 ml) of divinylbenzene, 0.71 mol (123.2 ml) of ethylvinylbenzene, 5.5 ml of a dichloroethane solution (concentration: 0.73 mmol / ml) of 1-chloroethylbenzene (364.2 mmol) and 3500 ml of dichloroethane (dielectric constant: 10.3) was put into a 5000 ml flask, and 63.3 ml of 50.11 mmol of SnCl ₄ in dichloroethane (concentration: 0.074 mmol / ml) was added at 70 ° C. and reacted for 3 hours. I let you. After the polymerization reaction was stopped with a small amount of methanol bubbled with nitrogen, the reaction mixture was poured into a large amount of methanol at room temperature to precipitate a soluble aromatic polymer. The obtained copolymer was washed with methanol, filtered, dried, and weighed to obtain 178.91 g of a soluble aromatic copolymer (yield: 61.3 wt%). The polymerization activity was 8.54 (g polymer / mmol Sn · hr). Mw of the obtained copolymer was 49700, Mn was 9730, and Mw / Mn was 5.1.

Example 1
The following components were blended to prepare a photosensitive resin composition solution for volume phase hologram recording.
Dichloromethane: 50 g, copolymer obtained in Synthesis Example 1: 10 g, TCP: 15 g, MS-200: 20 g, S2EG: 15 g, 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals): 0.1 g, 3-ethyl-5-[(3-ethyl-2 (3H) -benzothiazolylidene) ethylidene] -2-thioxo-4-oxazolidinone (NK-1473, manufactured by Hayashibara Biochemical Laboratories) ): 0.01 g was dissolved to obtain a photosensitive solution.
This was applied to one side of a 50 mm × 50 mm glass substrate having a thickness of 0.5 mm using a bar coater to a dry film thickness of 50 μm and dried in an inert oven in a nitrogen atmosphere set at 50 ° C. for 1 hour. Thus, a photosensitive plate for volume phase hologram recording was prepared. As a protective film, a 38 μm PET film was laminated to obtain an optical information recording medium.

Using the two-beam interference exposure method with 514.5 nm light of the obtained recording medium argon ion laser, interference fringes with a spatial frequency of about 1000 lines / mm were formed and incident from the PET side to record a volume phase hologram. The exposure of the transmission hologram was performed at an exposure amount of 10 to 100 mJ / cm ² for 10 to 100 seconds with one light intensity on the photosensitive plate being 1 mW / cm ² . The obtained volume phase hologram had a diffraction efficiency of 82% at an exposure amount of 13 mJ / cm ² . Moreover, the cure shrinkage rate of the resin composition was 0.5%.

Examples 2-6 and Comparative Examples 1-3
A photosensitive resin composition solution was prepared in the same manner as in Example 1 except that the composition was as shown in Table 1. From this, an optical information recording medium was obtained, a hologram was recorded, and evaluation was performed. The composition and evaluation results are summarized in Table 1. In Table 1, DVB oligomer (Mn = 2000) represents the copolymer obtained in Synthesis Example 1, and DVB oligomer (Mn = 10000) represents the copolymer obtained in Synthesis Example 2.

Industrial applicability

  According to the present invention, by using a soluble polyfunctional vinyl aromatic copolymer in the photosensitive resin composition, not only the transparency, but also the volume phase hologram recording excellent in sensitivity, low curing shrinkage, and transparency. A material, a volume phase hologram recording medium, and a volume phase hologram can be provided.

Claims (5)

A soluble aromatic copolymer having a structural unit of a divinyl aromatic compound and a structural unit of a monovinyl aromatic compound and containing 10 mol% or more of a structural unit represented by the following formula (a1) derived from the divinyl aromatic compound (A), photo-radically polymerizable compound (B) and photopolymerization initiator (C) copolymerizable with soluble aromatic copolymer (A), polymer binder (D) and / or plasticizer (E A photosensitive resin composition for volume phase hologram recording, comprising 5 to 60% by weight of a soluble aromatic copolymer (A).

However, R < ¹ > shows a C6-C30 aromatic hydrocarbon group.   The photosensitive resin composition for volume phase hologram recording according to claim 1, wherein the soluble aromatic copolymer (A) has a number average molecular weight of 400 to 30,000.   An optical information recording medium for volume phase hologram recording, wherein the recording layer comprising the photosensitive resin composition according to claim 1 or 2 is formed on one support or between two supports.   A volume phase hologram obtained by recording interference fringes formed from energy beams having excellent coherency on the optical information recording medium according to claim 3.   4. A method for producing a volume phase hologram, wherein the recording medium according to claim 3 is subjected to exposure recording of interference fringes formed from energy beams having excellent coherency.