JP5108873B2 - Volume phase hologram recording material and optical information recording medium using the same - Google Patents

Description

  The present invention relates to a material suitable for volume phase hologram recording that records and reproduces information using coherent active energy rays, and an optical information recording medium using the material.

  Hologram information recording is a method for recording / reproducing information as two-dimensional page data, and it is possible to greatly improve recording density and transfer speed as compared with bit data methods such as DVD. Research and development is actively underway as one of the optical information recording methods.

  In particular, an optical information recording medium (hereinafter also simply referred to as a hologram recording medium) using a volume phase hologram recording material (hereinafter also simply referred to as a hologram recording material) has a theoretical maximum diffraction efficiency as high as 1, Moreover, since information can be overwritten (multiple recording), it is expected to be put to practical use as an information recording medium that can achieve high-density recording. As the hologram recording material, a photopolymer is often used in consideration of the simplicity of recording medium production and the variety of raw material selection.

  A recording layer of a hologram recording medium containing a photo radical polymerizable component and a photo radical polymerization initiator (hereinafter also simply referred to as a hologram recording layer) is irradiated with reference light and information light consisting of coherent active energy rays at the same time. When the interference pattern is generated, a polymerization reaction is induced in the bright part, and the polymerizable component diffuses and moves from the dark part to the bright part in the direction in which the concentration gradient caused by the polymerization reaction is relaxed / eliminated. On the other hand, the non-reactive component moves in a reverse diffusion direction from the bright part to the dark part of the interference pattern in the direction in which the diffusion movement of the polymerizable component is compensated. In this way, a concentration distribution of each component corresponding to the intensity of the interference pattern is generated in the hologram recording layer, and this is recorded as a refractive index modulation structure.

  The recording capacity of the hologram recording medium is in principle proportional to the thickness of the hologram recording layer. Accordingly, it is advantageous that the hologram recording layer is formed as thick as possible within a range in which the influence on the recording performance due to light absorption by the material and volume shrinkage accompanying the polymerization reaction can be substantially allowed. The thickness actually required for the hologram recording layer is about 200 μm to 2 mm, which is much thicker than the conventional optical information recording medium.

  Patent Document 1 discloses a substantially solid photopolymerizable composition that forms a refractive index image when exposed to actinic radiation as the only processing step, and is essentially (a) 25-75% solvent soluble. , Thermoplastic polymer binder, (b) 5-60% liquid ethylenically unsaturated monomer, (c) active polymerization of unsaturated monomer when exposed to 0.1-10% actinic radiation A composition comprising a photoinitiator system is disclosed. Here, a solvent is used in order to dissolve each component uniformly and to lower the viscosity of the composition to such an extent that it can be coated on a support. In order to form a hologram recording layer, a drying step of evaporating and removing the solvent after applying the composition on a support is required, and thus the thickness of the recording layer is substantially limited to 100 μm or less. .

  Several hologram recording materials capable of forming a relatively thick layer of about 200 μm or more, a hologram recording medium using the same, and a method for producing the same have been disclosed so far without forming a hologram recording layer. . For example, there are those including a three-dimensional cross-linked polymer matrix formed in the in-situ formation of the hologram recording layer (Patent Documents 2 to 7, Non-Patent Document 1, etc.).

  Here, the three-dimensional cross-linked polymer matrix not only plays a role of imparting physical strength to the hologram recording material to maintain the shape as a hologram recording layer, but also suppresses excessive movement of the polymerizable compound. It is thought to play a role in reducing volume shrinkage associated with polymerization of NPL (Non-Patent Document 1).

  Patent Document 2 discloses an optical product comprising a three-dimensional cross-linked polymer matrix and one or more photoactive monomers, and the polymers resulting from the polymerization of the matrix polymer and the active monomers are compatible. It is disclosed that a three-dimensional cross-linked polymer matrix is formed by a polymerization reaction independent of the reaction of the photoactive monomer in the presence of the photoactive monomer.

  The hologram recording medium having this configuration does not require a solvent when forming the hologram recording layer, and has an advantage that a thick layer of about several hundred μm to several mm can be formed relatively easily.

  The hologram recording medium is also required to have high transparency. Accordingly, the three-dimensional cross-linked polymer matrix needs to be compatible with the polymerizable monomer and the polymer formed by polymerizing the monomer.

  However, in the optical product disclosed in Patent Document 2, combinations of the matrix polymer and the monomer that satisfy the compatibility condition are limited. Further, even if the combination of the matrix polymer and the monomer satisfying the compatibility condition is satisfied, there is a problem that the difference in refractive index between the matrix polymer and the polymer formed by polymerizing the monomer and the monomer cannot be obtained.

  In hologram information recording, data recorded as an interference pattern is completely fixed by performing a fixing process such as post-exposure. When a large amount of data is recorded continuously, the time required from the start of data recording to the end of fixing becomes longer, so that data once recorded may deteriorate during that time. Therefore, the hologram recording medium is further required not to deteriorate the data recorded within at least the time required from the continuous recording to the immobilization process (hereinafter referred to as record retention).

  However, the optical product disclosed in Patent Document 2 has a problem that the record retention is not sufficient.

  Patent Document 3 is a polymer matrix having a three-dimensional cross-linked structure having a plurality of reactive groups, which is capable of recording interference fringes caused by coherent light interference by a difference in refractive index, A volume hologram recording material having no polymerizable monomer as a component for recording a hologram is disclosed.

  Patent Document 4 discloses (a) a compound containing one or more active methylene groups in one molecule or a compound containing two or more active methine groups in one molecule, and (b) a carbanion produced from an active methylene group or an active methine group. A photosensitive composition for volume hologram recording, comprising: a compound containing two or more groups to be nucleophilically added in one molecule; (c) a Michael reaction catalyst; (d) a photopolymerizable compound; and (e) a photopolymerization initiator system. Things are disclosed.

  Although the hologram recording materials disclosed in Patent Document 3 and Patent Document 4 are improved in record retention, the sensitivity is still not sufficient.

  As described above, some hologram recording materials including a three-dimensional cross-linked polymer matrix formed in the process of forming a hologram recording layer have been disclosed so far, but high sensitivity and high contrast are obtained. In addition, a material having high record retention has not been provided yet.

  Patent Document 5 and Non-Patent Document 2 disclose a method for producing a soluble aromatic copolymer by copolymerizing monomers mainly composed of an aromatic monovinyl compound and an aromatic divinyl compound by a special method. However, nothing teaches the use of such a soluble aromatic copolymer as a component of a hologram recording material.

JP-A-2-3081 JP 11-352303 A WO2005 / 078531 JP 2005-275389 A JP 2004-123873 A T.J.Trentler, J.E.Boyd and V.L.Colvin, Epoxy Resin-Photopolymer Composites for Volume Holography, Chemistry of Materials, Vol. 12, pp. 1431-1438 (2000). Macromolecules, 34, 396-401 (2001)

  An object of the present invention is to provide a volume phase hologram recording material that has high sensitivity, high contrast, and excellent record retention, and a volume phase hologram recording medium using the same.

（式中、Ｒ¹は炭素数６〜３０の芳香族炭化水素基を示す。）
The present invention relates to a volume phase hologram recording material mainly comprising (a) a three-dimensional crosslinked polymer matrix, (b) a photoradical polymerizable compound, and (c) a photoradical polymerization initiator, and (b) a photoradical. The polymerizable compound has 10 to 70 mol% of the structural unit of the divinyl aromatic compound represented by the following formula (b1), 10 to 70 mol% of the structural unit of the monovinyl aromatic compound, and the number average molecular weight (Mn) is 300 to 10000, the molecular weight distribution (Mw / Mn) is 10 or less, and 0.5 to 30 wt% of the soluble aromatic copolymer (B1) having a terminal group represented by the following formulas (b2) and (b3) % Volume phase hologram recording material. Here, the soluble aromatic copolymer (B1) satisfies the following mole fraction with respect to the terminal group.

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

（式中、Ｒ²は炭素数１〜３０の鎖状炭化水素基、芳香族炭化水素基又はこれらに(メタ)アクリロキシ基が置換した基を示す。Ｙは酸素又はイオウを示す。） The soluble aromatic copolymer (B1) has a terminal group having a structure represented by the following formulas (b2) and (b3), and the mole of the formula (b2) with respect to the sum of the formulas (b2) and (b3) fraction [(b2) / [(b2 ) + (b3)] is 0.5 or more.

(In the formula, R ² represents a chain hydrocarbon group having 1 to 30 carbon atoms, an aromatic hydrocarbon group or a group substituted with a (meth) acryloxy group. Y represents oxygen or sulfur.)

  Preferred examples of the monovinyl aromatic compound constituting the soluble aromatic copolymer (B1) include aromatic olefins selected from styrene, vinyl naphthalene, vinyl biphenyl, indene, acenaphthylene, benzothiophene, and substituted products thereof.

  Further, the present invention is an optical information recording medium for volume phase hologram recording, wherein the volume phase hologram recording material is formed on one support or between two supports.

  Further, the present invention is a volume phase hologram recording material precursor comprising (A) a three-dimensional crosslinked polymer matrix-forming compound, (b) a photoradical polymerizable compound, and (c) a photoradical polymerization initiator as main components. (A) The polymer matrix-forming compound is polymerized by a polymerization reaction other than the photoradical polymerization reaction to form a three-dimensional crosslinked polymer matrix, and the (b) photoradical polymerizable compound is represented by the formula (b1). The structural unit of the divinyl aromatic compound is 10 to 70 mol%, the structural unit of the monovinyl aromatic compound is 10 to 70 mol%, the number average molecular weight (Mn) is 300 to 10,000, and the molecular weight distribution (Mw / Mn). Is a volume phase hologram recording material precursor characterized by containing 0.5 to 30 wt% of a soluble aromatic copolymer (B1) of 10 or less.

  Furthermore, the present invention provides the above volume phase hologram recording material, wherein the volume phase hologram recording material precursor is formed into a three-dimensional crosslinked polymer matrix by a polymerization reaction other than a photoradical polymerization reaction. It is a forming method.

  The volume phase hologram recording material according to the present invention contains (a) a three-dimensional crosslinked polymer matrix, (b) a photoradical polymerizable compound, and (c) a photoradical polymerization initiator as main components. The volume phase hologram recording material precursor according to the present invention contains (A) a three-dimensional crosslinked polymer matrix-forming compound, (b) a photoradical polymerizable compound, and (c) a photoradical polymerization initiator as main components.

  Hereinafter, the three-dimensional crosslinked polymer matrix is also referred to as a polymer matrix or (a) component, and the compound (monomer) forming the three-dimensional crosslinked polymer matrix is also referred to as (A) polymer matrix-forming compound or (A) component, and (b) light. The soluble polyfunctional vinyl copolymer contained in the radical polymerizable compound is also referred to as component (B1), and (c) the photo radical polymerization initiator is also referred to as component (c).

  The volume phase hologram recording material of the present invention is obtained by subjecting the volume phase hologram recording material precursor of the present invention (hereinafter also referred to as a hologram recording material precursor) to photo radical polymerization reactivity by a polymerization reaction other than the photo radical polymerization reaction. It is advantageous to produce by forming the three-dimensional crosslinked polymer matrix having groups. The hologram recording material precursor contains (A) a polymer matrix forming compound, (b) a photoradical polymerizable compound, and (c) a photoradical polymerization initiator as main components.

  The volume phase hologram recording material or hologram recording material precursor of the present invention contains the above component (a) or component (A), component (b) and component (c) as the main components. Here, the three-dimensional crosslinked polymer matrix of the component (a) may have a radical photopolymerizable group, but only a part of the component (b) is a radical photopolymerizable group of the three-dimensional crosslinked polymer matrix. It is preferable that it reacts with.

  The case where the component (a) has a radical photopolymerizable group occurs when a part of the component (b) has a functional group capable of reacting with the component (A) in addition to the radical photopolymerizable group. . For example, when the soluble polyfunctional aromatic vinyl copolymer of the component (B1) which is a part of the component (b) is a copolymer containing a hydroxyl group or a thiol group as the terminal group (b3), This is because it may be introduced into the component matrix via, for example, a (thio) urethane bond or a thioether bond. In the case where the component (b) has a functional group capable of reacting with the component (A) in addition to the photoradical polymerization reactive group and forms a three-dimensional crosslinked polymer matrix by a polymerization reaction other than the photoradical polymerization reaction, (A) Calculate as a component.

  In the present invention, the three-dimensional crosslinked polymer matrix is preferably formed in the process of forming the hologram recording layer (in-situ). Advantageously, when forming a hologram recording layer using a hologram recording material precursor, it is preferable to form a three-dimensional crosslinked polymer matrix. In this case, in addition to the matrix-forming compound of component (A), a three-dimensional crosslinked polymer matrix is formed in the state where the radically polymerizable compound of component (b) and the photoradical polymerization initiator of component (c) coexist. At this time, if the radical polymerization reactive group of the component (b) reacts at the same time, the performance as a hologram recording material deteriorates. Therefore, even in the presence of the component (c), the radical photopolymerization of the component (b) It is preferable to form the reactive group without reducing it as much as possible. The polymerization referred to in this specification includes condensation, polyaddition and the like in addition to polymerization involving unsaturated groups. Moreover, radical photopolymerization includes the case of polymerizing in the presence of a photopolymerization initiator, and the same applies to radical photopolymerizable groups. And as a photopolymerizable functional group, the functional group which has an olefinic double bond is suitable. Further, radical photopolymerization (reactive group) may be abbreviated as radical polymerization (reactive group).

  Examples of reactions for forming a three-dimensional cross-linked polymer matrix without substantially reducing radical photopolymerizable groups include polycondensation reactions in which polymerization proceeds in a reaction form different from radical photopolymerization, isocyanate- Examples include hydroxyl polyaddition reaction (polyurethane formation), isocyanate-amine polyaddition reaction (polyurea formation), epoxy (episulfide) -amine polyaddition reaction, epoxy (episulfide) -hydroxyl (thiol) polyaddition reaction, and the like. Preference is given to an isocyanate-hydroxyl polyaddition reaction or an epoxy (episulfide) -thiol polyaddition reaction. However, it is not limited to this. In order to form a three-dimensional crosslinked polymer matrix without substantially reducing the radical photopolymerization reactive group, a reaction catalyst or the like is used so that polymerization in a reaction form different from radical photopolymerization occurs preferentially. It is good to mix | blend or to adjust reaction temperature.

  When the case where the polyurethane obtained by the isocyanate-hydroxyl polyaddition reaction is a three-dimensional crosslinked polymer matrix is described as an example, the isocyanate compound and the hydroxy compound are the matrix-forming compound of the component (A). In order to form a three-dimensional crosslinked polymer matrix, at least one of the isocyanate compound or the hydroxy compound has an average of more than 2 isocyanate groups and hydroxy groups. When there are two or more types of component (A), they are referred to as component (A1) and component (A2), respectively. In the above case, the isocyanate compound is referred to as component (A1) and the hydroxy compound is referred to as component (A2).

  As the isocyanate compound to be the component (A1), an isocyanate compound having two or more isocyanate groups in one molecule or a mixture thereof is used. For example, tolylene diisocyanate (TDI), diphenylmethane-4,4′-diisocyanate (MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), naphthylene-1,5-diisocyanate (NDI), triphenyl Methane-4,4 ′, 4 ″ -triisocyanate, dicyclohexylmethane-4,4′-diisocyanate (H12MDI), hydrogenated xylylene diisocyanate (H6XDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI) , Isophorone diisocyanate (IPDI), norbornane diisocyanate (NBDI), cyclohexane-1,3,5-triisocyanate and these isocyanates Trimer derived from compounds, biuret, adduct, such as pre-polymers. These polyisocyanate compounds may be used alone or in combination of two or more.

  As the hydroxy compound to be the component (A2), a hydroxy compound having two or more hydroxyl groups in one molecule or a mixture thereof is used. For example, polyether polyols, polyester polyols, polycarbonate diols and the like can be mentioned. When an isocyanate compound having two isocyanate groups per molecule (diisocyanate compound) is selected as the isocyanate compound used in the isocyanate-hydroxy polymerization for forming the matrix, in order to form a three-dimensional crosslinked polymer matrix, It is preferable to use a hydroxy compound having 3 or more hydroxyl groups in one molecule. These hydroxy compounds may be used alone or in combination of two or more.

  The above is a case where the matrix-forming compound is an isocyanate compound (A1) component and the hydroxy compound is a component (A2), but is not limited thereto. When the matrix-forming compound is an epoxy compound and a curing agent having a phenolic hydroxyl group or amino group, the epoxy compound becomes the component (A1), the phenol compound becomes the component (A2), and the amino compound becomes the component (A3). There are cases.

  The volume phase hologram recording material of the present invention is intended to record information using the refractive index contrast between an exposed portion and an unexposed portion. In a volume phase hologram recording medium made of this material, At least a part of the refractive index contrast between the exposed part and the unexposed part is formed by diffusing a part of the (b) photoradically polymerizable compound into the exposed area after exposure. If this refractive index contrast is high, the signal intensity at the time of reading out the hologram increases, so basically the refractive index difference between the photopolymerizable monomer that diffuses and the three-dimensional cross-linked matrix polymer so as to obtain a high refractive index contrast. A larger one is desirable. However, when this (b) radical photopolymerizable compound is composed of only a low molecular weight monomer, it gradually diffuses even after the exposure necessary for recording is stopped, and has an important record retention property and multiple recording property as a hologram. It will get worse. In the present invention, the refractive index of the three-dimensional crosslinked polymer matrix can be adjusted by using the soluble aromatic vinyl copolymer (B1) as a part of (b) the photoradical polymerizable compound. The refractive index difference between the cross-linked polymer matrix polymer and the photopolymerizable monomer can be controlled by adjusting the signal intensity at the time of reading too high, improving the multi-recording property, and preventing turbidity from occurring for a long time. It can be done.

  The reaction for forming the three-dimensional crosslinked polymer matrix without substantially reducing the radical polymerization reactive group can be promoted by using an appropriate catalyst. For example, as a catalyst for isocyanate-hydroxyl polyaddition reaction, tin compounds such as dimethyltin dilaurate and dibutyltin dilaurate, 1,4-diazabicyclo [2,2,2] octane (DABCO), imidazole derivatives, 2,4,6- Tertiary amine compounds such as tris (dimethylaminomethyl) phenol and N, N-dimethylbenzylamine can be used. These catalysts may be used alone or in combination of two or more.

  In addition to the component (a), the hologram recording material of the present invention is blended with a radical photopolymerizable compound (b) and a radical photopolymerization initiator (c). When the light is irradiated, the component (c) generates radicals to cause polymerization of the component (b). The polymer produced from the component (b) or the component (b) is desirably compatible with the polymer matrix and exhibits high transparency. The sensitivity of the hologram recording material and the contrast of recorded data can be further increased by using an appropriate component (b).

  Examples of the radically polymerizable compound (b) include those that undergo a radical polymerization reaction initiated by coherent active energy rays used for hologram recording and are compatible with the three-dimensional crosslinked polymer matrix, such as acryloyl group and methacryloyl group. And monomers having a vinyl group or an isopropenyl group, and a soluble aromatic vinyl copolymer (B1).

The soluble polyfunctional aromatic vinyl copolymer (B1) has a structural unit of divinyl aromatic compound and a structural unit of monovinyl aromatic compound, and the structural unit represented by the above formula (b1) is 10 to 70 mol%. The soluble aromatic copolymer contained and composed of this structural unit is also simply referred to as copolymer (B1). This structural unit is derived from a divinyl aromatic compound. Therefore, by describing the divinyl aromatic compound used, R ¹ in formula (b1) is understood. The divinyl aromatic compound is known to give a structural unit represented by the formula (b1) and to give some other structural unit such as a branched or cross-linked structural unit. Then, the solvent becomes insoluble and the solubility is not given, so that the reaction conditions are controlled so that the structural unit represented by the formula (b1) is mainly used. A method for producing such a soluble polyfunctional aromatic vinyl copolymer is described in Patent Document 5, Non-Patent Document 2, and the like.

  Advantageously, the copolymer (B1) has 10 to 70 mol% of structural units of the divinyl aromatic compound represented by the formula (b1) and 10 to 70 mol% of structural units of the monovinyl aromatic compound, The number average molecular weight (Mn) is 300 to 10,000, and the molecular weight distribution (Mw / Mn) is 10 or less.

Here, it is desirable that the soluble polyfunctional vinyl aromatic polymer satisfies one or more of the following requirements.
1) Among the end groups of the soluble polyfunctional vinyl aromatic polymer, the above formulas (b2) and (b3)
The molar fraction of the end group of the structure represented by the following formula:
(B2) / [(b2) + (b3)] ≧ 0.5
Is satisfied, preferably 0.5 to 0.9.
2) The introduction amount of the terminal group having the structure represented by the formula (b2) at the terminal of the soluble polyfunctional vinyl aromatic polymer is 1.5 / molecule or more.

In the above formulas (b2) and (b3), R ² represents a chain hydrocarbon group having 1 to 30 carbon atoms, an aromatic hydrocarbon group, or a (meth) acryloxy group (—OOC—CR═CH ₂ ). Represents a substituted group, and Y represents oxygen or sulfur. An example of a group in which a (meth) acryloxy group is substituted on a chain hydrocarbon group is a group represented by —OC _n H _2n —O—OOC—C (R) ═CH ₂ . Here, R represents represents H or CH _3, n is a number of 1 to 30.

  The copolymer (B1) is soluble in one or more of toluene, xylene-tetrahydrofuran, dichloroethane, or chloroform, preferably all solvents.

  The basic skeleton of the copolymer (B1) is obtained by polymerizing a polymerization raw material containing a divinyl aromatic compound and a monovinyl aromatic compound in the presence of a catalyst, preferably in the presence of a Lewis acid catalyst. The ratio of use is 20 to 90 mol%, preferably 40 to 80 mol%, and 10 to 80 mol%, preferably 20 to 60 mol%, of the monovinyl aromatic compound. If necessary, other olefin compounds of 30 mol% or less, preferably 10 mol% or less may be used. Here, the structural unit refers to a unit in a polymer generated from one monomer.

  Examples of the divinyl aromatic compound include m-, p-divinylbenzene, 1,2-diisopropenylbenzene, 1,3-divinylnaphthalene, 4,4′-divinylbiphenyl, 1,2-divinyl-3,4. -Dimethylbenzene or the like can be used, but is not limited thereto. These can be used alone or in combination of two or more.

  Examples of the monovinyl aromatic compound include styrene, vinyl naphthalene, vinyl biphenyl and the like and derivatives thereof. Derivatives include compounds in which an aromatic ring is substituted with a substituent such as an alkyl group, an alkoxy group, a halogen, a phenyl group, or a hydroxyl group, and a compound in which the above substituent is substituted at the α-position or β-position of the vinyl group. In addition, a monovinyl aromatic compound having a vinyl group in the ring-constituting carbon can be used, and examples of the monovinyl aromatic compound include aromatic olefins such as indene, acenaphthylene, and benzothiophene, and derivatives thereof.

  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 produced in the skeleton of the copolymer is large during polymerization. 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 copolymer (B1) is obtained by copolymerizing the divinyl aromatic compound and the monovinyl aromatic compound as described above, but other cationically polymerizable 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, diisobutylene, and vinyl compounds having a sulfur atom.

  A copolymer (B1) has a structural unit (b2) or (b3) at the terminal. (B3) is a hydroxyl group or a thioether group.

As a method of introducing a hydroxyl group or a thioether group into the terminal of the copolymer (B1), it is possible by coexisting an alcohol or a thiol compound as a chain transfer agent in cationic polymerization using a polymerization catalyst system comprising a Lewis acid. It is. The alcohol compound as the chain transfer agent is not particularly limited. For example, when 2-hydroxyethyl (meth) acrylate is used, a (meth) acrylate group having excellent photocurability can be introduced into one end of the copolymer (B1). As another method, the target hydroxyl group may be introduced by performing functional group conversion such as Friedel-Crafts reaction after obtaining a polymer by cationic polymerization. Advantageously, introducing YR ² may be used a chain transfer agent represented by HO-YR ^2, to introduce a YH is to use a chain transfer agent represented by HO-YH It is good.

  The polymerization method for producing the copolymer (B1) can be basically synthesized by a general cationic polymerization method using a Lewis acid catalyst. For example, the method described in Non-Patent Document 2 is preferable. Take as an example.

  The number average molecular weight Mn (in terms of standard polystyrene obtained using gel permeation chromatography) of the copolymer (B1) is preferably from 300 to 10,000. More preferably, it is 500-5000. If the Mn is less than 300, the viscosity of the copolymer (b) is too low, and the processability is not good, which is not preferable. Further, if Mn is 10,000 or more, it is not preferable because rapid mass transfer during hologram recording is inhibited. The molecular weight distribution (Mw / Mn) is preferably 10 or less. If it exceeds 10, there is a possibility that problems such as deterioration of processing characteristics of the copolymer (b) and generation of gel may occur.

  The copolymer (B1) contains a chain hydrocarbon group or an aromatic hydrocarbon group via an ether bond or a thioether bond, and these have a terminal group represented by the above formulas (b2) and (b3). It may be included as a copolymer molecule.

  And it is preferable that the molar fraction (b2) / [(b2) + (b3)] of the terminal group of the said structure is 0.5 or more, More preferably, it is 0.7 or more and 0.9 or less. When the molar fraction is less than 0.5, the heat discoloration of the copolymer (B1) is lowered, and the compatibility with the matrix of the copolymer (B1) is increased, so that the sensitivity is lowered. . On the other hand, if it exceeds 0.9, phase separation tends to occur, and the storage stability is lowered.

  As the radical photopolymerizable compound other than the component (B1) used as the component (b), a so-called radical polymerizable monomer is preferable, and a high refractive index radical polymerizable compound having an aromatic ring or a sulfur atom in one molecule. It is more preferable to use a monomer. Examples of such compounds include styrene, chlorostyrene, bromostyrene, α-methylstyrene, divinylbenzene, diisopropenylbenzene, vinylnaphthalene, divinylnaphthalene, vinylbiphenyl, divinylbiphenyl, indene, acenaphthylene, N-vinylcarbazole, N -Vinylpyrrolidone, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate, tribromophenyl (meth) acrylate, tribromophenoxyethyl (meth) acrylate, alkylene oxide modified Di (meth) acrylate of bisphenol A, di (meth) acrylate of 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4- Roxy-3-methylphenyl) fluorene di (meth) acrylate, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene di (meth) acrylate, bis (2-methacryloylthioethyl) sulfide, bis (4-methacryloylthiophenyl) sulfide and the like. These radically polymerizable monomers may be used alone or in combination of two or more.

  The blending amount of the radically polymerizable monomer of the component (b) is preferably 30 wt% or less, more preferably 10 wt% or less with respect to the component (a). However, it is preferably 1.0 wt% or more.

As the radical photopolymerization initiator of the component (c), various known radical photopolymerization initiators can be used, which are appropriately selected according to the wavelength of the coherent active energy ray used for hologram recording. Good. As a preferable radical photopolymerization initiator, for example, bis (η ⁵ -2,4-cyclopentadien-1-yl) bis (2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium, Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and the like can be mentioned.

  The amount of radical photopolymerization initiator added varies depending on the type of radical photopolymerization initiator used, the concentration of radical polymerizable reactive groups introduced into the three-dimensional cross-linked polymer matrix, and the amount of radical polymerizable monomer added. Although not determined, the range of 0.05 to 10% by weight is preferable with respect to the entire hologram recording material, and the range of 0.1 to 5% by weight is more preferable.

  In addition to the above components, the hologram recording material of the present invention or a precursor thereof can be mixed with a three-dimensional cross-linked polymer matrix and a compound that is non-reactive with the above components can be blended as the component (d). Here, the non-reactive compound means a compound that does not substantially participate in either the reaction for forming the three-dimensional crosslinked polymer matrix or the photoradical polymerization reaction at the time of hologram recording. It is chosen from those that melt. Examples of such non-reactive compounds include plasticizers, viscosity modifiers and antifoaming agents. Preferably, it is a plasticizer. As a role of the plasticizer, it can be considered that the radical polymerizable component is diffused in the hologram recording material and the time required for forming the refractive index modulation structure at the time of hologram recording is reduced.

  By selecting a plasticizer having an appropriate refractive index, the contrast of recorded data can be improved. For example, when using a high refractive index compound having an aromatic ring or a sulfur atom in one molecule as a radical polymerizable monomer, the plasticizer may be 0.05 or more with respect to the refractive index of the high refractive index radical polymerizable monomer. Those having a low refractive index are preferred.

  In addition, additives such as a sensitizer, a chain transfer agent, and a stabilizer may be further included as necessary.

  For example, in the case of an isocyanate-hydroxyl polyaddition reaction, the volume phase hologram recording medium of the present invention can be used as a urethane prepolymer by reacting in advance with the polymer matrix-forming compound as component (A). The urethane prepolymer can be prepared by a commonly used method. That is, it is obtained by mixing an isocyanate compound and a polyol compound at a ratio of (NCO / OH) of 2.5 to 4.0 and reacting at 100 to 110 ° C. for 3 to 5 hours. The polyol compound to be used may or may not have a radical polymerization reactive group.

  After the volume phase hologram recording medium of the present invention is irradiated with light to form a hologram, this is cured to fix the recording. The curing method is not particularly limited, and any of curing methods such as photocuring and thermosetting can be applied.

  The volume phase hologram recording medium of the present invention is used by forming a hologram recording material on a substrate. Specifically, it is used by forming on one support or between two supports.

  The volume phase hologram recording medium of the present invention can be prepared by using a liquid volume phase hologram recording material precursor composition, and when the support is a single sheet, for example, the composition can be spin coater, roll coater, bar coater, etc. Using known coating means, it is coated on a substrate such as a glass plate, a polycarbonate plate, a polymethylmethacrylate plate or a polyester film, polymerized, and three-dimensional without substantially reducing radical photopolymerizable groups. A method of forming a crosslinked polymer matrix 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. Next, when there are two supports, a method of injecting a volume phase hologram recording material precursor composition into a transparent support can be mentioned. Specifically, as a method of injecting into the transparent support, a pair of transparent supports is arranged so that the transparent support is provided on both sides of the completed recording layer, and the two transparent supports are arranged. A method for injecting the composition between the above, or a method in which an injection hole is provided in a box-shaped transparent support, and a surface of the box-shaped transparent support is opened. And a method in which the composition is poured or dropped and then covered with a transparent support on the opened surface.

  The volume phase hologram recording medium 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. In addition, the symbols, such as a monomer used in an Example, are as follows.

Actol MN-1000: Propylene glycol type triol with molecular weight of 1000 (Mitsui Chemical Polyurethane)
H ₁₂ MDI: dicyclohexylmethane-4,4′-diisocyanate (manufactured by Tokyo Chemical Industry)
HDI: Hexamethylene diisocyanate (manufactured by Tokyo Chemical Industry)
DBTL: Dibutyltin dilaurate (Asahi Denka)
HDGEBA: Hydrogenated bisphenol A type epoxy resin (manufactured by Toto Kasei)
HDEEBA: Hydrogenated bisphenol A type episulfide resin (made by Japan Epoxy Resin)
PETMP: Pentaerythritol tetra (3-mercaptopropionate) (manufactured by Tokyo Chemical Industry)
TDAMP: 2,4,6-tris (dimethylaminomethyl) phenol (manufactured by Tokyo Chemical Industry)
DVBP: 3,3′-divinylbiphenyl (manufactured by Nippon Steel Chemical Co., Ltd.)
DMI: 1,3-dimethyl-2-imidazolidinone (manufactured by Tokyo Chemical Industry)

(Evaluation of hologram)
Evaluation of the hologram and the photosensitive resin composition was performed by the following method.
* Evaluation of diffraction efficiency The diffraction efficiency of the transmission hologram was calculated by the following equation using the value obtained by reading the diffracted light from a linearly polarized He-Ne laser (633 nm) with an optical power meter.
Diffraction efficiency (%) = (diffracted light intensity / incident light intensity) × 100
* Multiple recording property M # and volume shrinkage rate The dynamic range (M #) and the volume shrinkage rate (shrinkage), which are indicators of the multiple recording property of the hologram recording material, can be calculated from the following equations.
Dynamic range: M / # = Σ√ (diffraction efficiency)
Shrinkage (%): Calculated from the difference between the angle during hologram recording and the angle during playback (detune angle).
* Evaluation of record storability (shelf life)
Difference in maximum diffraction efficiency and transparency immediately after preparation of evaluation sample and after 1 month (stored at 60 ° C.) (A: difference is within 5%, B: difference is 5 to 20%, C: difference is 20% or more)

Synthesis example 1
1.54 mol (227.8 ml) of divinylbenzene, 1.16 mol (166.2 ml) of ethylvinylbenzene, 136.1 ml of 2-phenyl-2-propanol (450.3 mmol) in dichloromethane (concentration: 3.31 M) and Dichloromethane (dielectric constant: 9.1) 2192 ml was put into a 5000 ml flask and cooled to 0 ° C. Further, 5.63 mol of pure water, and 125.8 ml of a solution of 225.1 mmol of boron trifluoride diethyl ether complex (BF ₃ · OEt ₂ ) in dichloromethane (concentration: 1.79 mmol / ml) were added for 1 hour. Reacted. The polymerization reaction was stopped with pure water that had been cooled in advance, and then separated with pure water using a separatory funnel to remove unreacted initiator and catalyst. Thereafter, the organic layer was poured into a large amount of methanol at room temperature to precipitate a soluble aromatic copolymer containing OH groups and methoxy groups at the ends. The obtained copolymer was washed with methanol, filtered, dried and weighed, and 271.8 g of a soluble aromatic copolymer (B1-1) having a hydroxyl group at the terminal (yield: 76.8 wt%). Got. Mw of the obtained copolymer (B1-1) was 4530, Mn was 3100, and Mw / Mn was 1.46. From the NMR analysis results, the structural unit (b1) was 63%, and the molar ratio of terminal groups [methoxy group] / ([OH group] + [methoxy group]) was 0.6.

Synthesis example 2
A flask containing 3000 ml of 1.83 mol (270.7 ml) of divinylbenzene, 1.38 mol (197.8 ml) of ethylvinylbenzene, 2011 ml of 2-hydroxyethyl methacrylate (1.07 mol) and toluene (dielectric constant: 2.4). It was put in and kept at 50 ° C. Further, 1.05 mol of ethyl acetate, and further 1.13 mol of boron trifluoride diethyl ether complex (BF ₃ · OEt ₂ ) 141.9 ml were added and reacted for 3 hours. After stopping the polymerization reaction with methanol, the reaction mixture was separated with a 0.1 M aqueous sodium hydroxide solution using a separatory funnel to remove unreacted initiator and catalyst. Thereafter, the organic layer was poured into a large amount of methanol at room temperature to precipitate a soluble aromatic copolymer having —O—C ₂ H 2 —OOC—C (CH ₃ ) ═CH ₂ group at the terminal. The obtained copolymer was washed with methanol, filtered, dried, and weighed to obtain 159.9 g (yield: 45.2 wt%) of a methacryloyl group-containing soluble aromatic copolymer (B1-2). . Mw of the obtained copolymer (B1-2) was 6200, Mn was 3700, and Mw / Mn was 1.67. From the NMR analysis results, the (b1) structural unit was 58%.

Synthesis example 3
Divinylbenzene 1.75 mol (258.9 ml), ethylvinylbenzene 1.30 mol (186.3 ml), 1-chloroethylbenzene (289.1 mmol) in toluene (concentration: 1.29 M) 224.1 ml and toluene ( Dielectric constant: 2.38) 2282 ml was put into a 3000 ml flask and heated to 35 ° C. Furthermore, 20.7 ml of a toluene solution (concentration: 0.584 mmol / ml) of 12.14 mmol of SnCl ₄ 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 Cl group-containing soluble aromatic copolymer. The obtained copolymer was washed with methanol, filtered, dried and weighed to obtain 226.43 g of Cl group-containing soluble aromatic copolymer (B1-3) (yield: 56.6 wt%). . The polymerization activity was 3.47 (g polymer / mmol Sn · hr). Mw of the obtained copolymer (B1-3) was 5915, Mn was 1890, and Mw / Mn was 3.13. From the NMR analysis results, the structural unit (b1) was 55.9%.

Example 1
The following components were blended to prepare a photosensitive resin composition solution for volume phase hologram recording.
First, 5 g of H ₁₂ MDI and DVBP were mixed, and 5 g of the copolymer (B1-1) obtained in Synthesis Example 1 was mixed with bis (eta (5) cyclopentadienyl) -bis- (2,6 0.5 g of -difluoro-3- (pyrrol-1-yl) phenyl) titanium (Irgacure784, manufactured by Ciba Specialty Chemicals) was dissolved. Subsequently, 71 g of MN-1000 (A component) and 0.5 g of DBTL (A component) were dissolved.
This composition solution was applied to one side of a glass substrate (with a double-sided antireflection film) having a size of 30 mm × 30 mm and a thickness of 1.2 mm using a dispenser. Subsequently, it is degassed until there are no air bubbles under vacuum, and this is covered with another glass and cured for 20 hours in an inert atmosphere in a nitrogen atmosphere set at 50 ° C., and a volume phase hologram recording having a polyurethane matrix A photosensitive plate was prepared. This was used as a volume phase hologram recording medium.

Example 2
A photosensitive resin composition solution was obtained in the same manner as in Example 1 except that the copolymer (B1-2) synthesized in Synthesis Example 2 was used as the soluble aromatic copolymer (B1 component). A phase hologram recording medium was obtained, and holograms were recorded and evaluated.

Example 3
The following components were blended to prepare a photosensitive resin composition solution for volume phase hologram recording.
First, 5 g of TDAMP, 5 g of DVBP, and 10 g of DMI were mixed, and 5 g of the copolymer (B1-1) obtained in Synthesis Example 1 and 0.5 g of Irgacure784 were dissolved therein. Subsequently, 44.5 g of HDGEBA and 30 g of PETMP were dissolved.
This composition solution was applied to one side of a glass substrate (with a double-sided antireflection film) having a size of 30 mm × 30 mm and a thickness of 1.2 mm using a dispenser. Subsequently, it is degassed until there are no air bubbles under vacuum, and this is covered with another glass and cured in an inert atmosphere in a nitrogen atmosphere set at 50 ° C. for 4 hours, and a volume phase hologram having an epoxy resin matrix A photosensitive plate for recording was prepared. This was used as a volume phase hologram recording medium.

For hologram recording, interference fringes with a spatial frequency of about 1000 lines / mm are generated using a two-beam interference exposure method using a green YAG laser (wavelength: 532 nm) light, which is incident from one glass side of the recording performance evaluation medium. A volume phase hologram was recorded. The exposure of the transmission hologram was performed at an exposure amount of 1000 mJ / cm ² with one light intensity on the photosensitive plate being 7 mW / cm ² . The volume phase hologram thus obtained had a maximum diffraction efficiency of 90%. Table 1 shows the dynamic range (M / #) and the cure shrinkage rate when angle multiplex recording (49 multiplex) is performed on the volume phase hologram recording medium.

Example 4 and Comparative Examples 1-3
A photosensitive resin composition solution was obtained in the same manner as in Example 1 or Example 3 except that the blending composition was as shown in Table 1. From this, a volume phase hologram recording medium was obtained, and a hologram was recorded. Evaluation was performed. The composition and evaluation results are summarized in Table 1. In Table 1, B1-1 represents the copolymer obtained in Synthesis Example 1, B1-2 represents the copolymer obtained in Synthesis Example 2, and B1-3 represents the copolymer obtained in Synthesis Example 3. .

Industrial applicability

  (B) By containing the soluble polyfunctional aromatic vinyl copolymer (B1) as a part of the radical photopolymerizable compound, the diffusion rate of the radical photopolymerizable compound can be controlled, and the hologram recording performance The most important multiple recording performance can be improved. In addition, the presence of the copolymer (B1) improves compatibility with other components, and can be transparent even when the difference in refractive index is large. According to the present invention, it is possible to obtain a volume phase hologram recording material having high sensitivity, high contrast, and excellent record retention, and a volume phase hologram recording medium using the same.

Claims (6)

(A) a three-dimensional cross-linked polymer matrix, (b) a photo-radical polymerizable compound, and (c) a volume phase hologram recording material mainly comprising a photo-radical polymerization initiator, wherein (b) the photo-radical polymerizable compound is The structural unit of the divinyl aromatic compound represented by the following formula (b1) is 10 to 70 mol%, the structural unit of the monovinyl aromatic compound is 10 to 70 mol%, and the number average molecular weight (Mn) is 300 to 10,000. The molecular weight distribution (Mw / Mn) is 10 or less and has a terminal group represented by the following formulas (b2) and (b3), and the mole of the formula (b2) with respect to the sum of the formulas (b2) and (b3) Volume phase hologram recording comprising 0.5-30% of soluble aromatic copolymer (B1) having a fraction [(b2) / [(b2) + (b3)] of 0.5 or more material.

Here, R < ¹ > shows a C6-C30 aromatic hydrocarbon group. R ² represents a chain hydrocarbon group having 1 to 30 carbon atoms, an aromatic hydrocarbon group, or a group in which a (meth) acryloxy group is substituted. Y represents oxygen or sulfur. The monovinyl aromatic compound constituting the soluble aromatic copolymer (B1) is an aromatic olefin selected from styrene, vinyl naphthalene, vinyl biphenyl, indene, acenaphthylene, benzothiophene, or a substituted product thereof . Volume phase hologram recording medium. The volume phase hologram recording material according to claim 1, further comprising (a) at least one (d) non-reactive compound that is compatible with the three-dimensional crosslinked polymer matrix . An optical information recording medium for volume phase hologram recording, wherein the volume phase hologram recording material according to any one of claims 1 to 3 is formed on one support or between two supports . (A) a three-dimensional crosslinked polymer matrix-forming compound, (b) a photoradical polymerizable compound, and (c) a volume phase hologram recording material precursor mainly comprising a photoradical polymerization initiator, wherein (A) a polymer matrix The forming compound is polymerized by a polymerization reaction other than the photoradical polymerization reaction to form a three-dimensional cross-linked polymer matrix, and the (b) photoradically polymerizable compound is represented by the following formula (b1) Having a structural unit of 10 to 70 mol%, a structural unit of monovinyl aromatic compound of 10 to 70 mol%, a number average molecular weight (Mn) of 300 to 10,000, and a molecular weight distribution (Mw / Mn) of 10 or less, And having a terminal group represented by the following formulas (b2) and (b3), the molar fraction of the formula (b2) with respect to the sum of the formulas (b2) and (b3) [(b2) / (B2) + (b3)] is a volume phase hologram recording material precursor comprising a soluble aromatic copolymer (B1) 0.5 to 30% is 0.5 or more.

Here, R < ¹ > shows a C6-C30 aromatic hydrocarbon group. R ² represents a chain hydrocarbon group having 1 to 30 carbon atoms, an aromatic hydrocarbon group, or a group in which a (meth) acryloxy group is substituted. Y represents oxygen or sulfur. The volume phase hologram recording material precursor according to claim 5 is formed into a three-dimensional crosslinked polymer matrix by a polymerization reaction other than a photoradical polymerization reaction (a) a three-dimensional crosslinked polymer matrix, (b) A method for forming a volume phase hologram recording material comprising, as main components, a) a radical photopolymerizable compound and (c) a radical photopolymerization initiator .