JP2005077940A - Hologram recording material and medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording material which ensures sufficiently high diffraction efficiency, and provide a hologram recording medium using the same. <P>SOLUTION: A hologram recording medium 100 has a structure in which a recording layer 40 is held between a substrate 20 and a protective layer 60, wherein the recording layer 40 consists of the hologram recording material containing a thiol compound having two or more mercapto groups, an unsaturated compound which has a functional group containing an unsaturated bond and polymerizes with the thiol compound, a photoinitiator which initiates the polymerization of the thiol compound and the unsaturated compound upon photoirradiation, and an inorganic compound having a refractive index different from that of a copolymer obtained by polymerization of the thiol compound and the unsaturated compound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hologram recording material and a hologram recording medium.

  In recent years, a method using a holography technique for recording interference fringes caused by light interference has attracted attention as a recording means capable of achieving a larger capacity than a conventional optical recording medium. In this method, for example, a recording material that causes a change in refractive index in accordance with the intensity of irradiated light is used, and interference fringes are recorded as a refractive index distribution that corresponds to the intensity distribution of the light. To record. The interference fringes thus recorded are generally called holograms.

As a recording material that causes such a change in refractive index, a recording material containing a polymer having no aromatic ring or heterocyclic ring, a monomer having a sulfur atom and a condensed ring, a sensitizing dye, and a photopolymerization initiator (for example, Patent Document 1), a recording material containing a vinyl polymer having a fluorine atom, a monomer having an aliphatic polycyclic group and a polymerizable unsaturated group, and a photopolymerization initiator (for example, see Patent Document 2). It has been known.
JP-A-7-181876 JP-A-8-241026

  By the way, the hologram recording material for recording using the above-described change in refractive index is required to have a high diffraction efficiency. The diffraction efficiency indicates the proportion of light that is effectively used to reproduce a reproduced image in the irradiated reproduction light. That is, the higher the diffraction efficiency, the brighter the reproduced image is obtained and recorded. Information can be read with high reproducibility. The diffraction efficiency tends to be higher as the recording material has a larger change in the refractive index corresponding to the intensity of the irradiated light.

  In the above-mentioned conventional photosensitive composition for hologram, first, the polymerization reaction of the monomer component proceeds at the site irradiated with light. When the polymerization reaction occurs in the composition in this way, the monomer component moves from the surroundings to the reaction site in order to compensate for the consumption of the monomer component. At the same time, the other components at the reaction site (components other than the monomer component and its copolymer; in the above-mentioned prior art, this corresponds to a polymer or vinyl polymer) are extruded therefrom. Thus, the photosensitive composition has a region where the concentration of the polymer obtained by polymerizing the monomer component is high and a region where the concentration of the other components is high, and a difference in composition occurs between the respective regions. In this case, since the polymer of the monomer component and the other components have different refractive indexes, a refractive index difference based on the difference in composition occurs in the photosensitive composition, and interference fringes are recorded by this refractive index difference. The

  However, recording materials that record interference fringes due to these refractive index differences have not yet achieved sufficient diffraction efficiency, and further studies are needed to put it into practical use as a hologram recording material that can be recorded with high accuracy. Was necessary.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a hologram recording material and a hologram recording medium capable of obtaining sufficiently high diffraction efficiency.

  As a result of intensive studies by the present inventors, the above-mentioned conventional hologram photosensitive composition has insufficient diffraction efficiency because the polymerization rate due to irradiation of the monomer component in this composition is low, For this reason, it turned out that it originates in the difference of the composition as mentioned above having not fully produced in the composition. The inventors of the present invention have found that sufficiently high diffraction efficiency can be obtained by using a recording material capable of causing a polymerization reaction with high efficiency by light irradiation, and have completed the present invention.

  That is, the hologram recording material of the present invention includes a thiol compound having two or more mercapto groups, an unsaturated compound having a functional group containing an unsaturated bond and polymerized with the thiol compound, and a thiol compound when irradiated with light. And an inorganic compound having a refractive index different from that of a copolymer obtained by polymerizing a thiol compound and an unsaturated compound.

  The above thiol compound and unsaturated compound can be easily copolymerized by irradiation with light to give a copolymer having a high degree of polymerization. For this reason, a polymerization reaction actively occurs in a portion where the intensity of light is high, and the amount of movement of the thiol compound and the unsaturated compound increases accordingly. Therefore, in the hologram recording material of the present invention containing these, the difference in composition between the region where the copolymer concentration is high and the region where the inorganic compound concentration is high becomes extremely large. As a result, a larger refractive index difference is produced as compared to the conventional hologram photosensitive composition.

  Moreover, since the thiol compound has two or more mercapto groups in the molecule, the copolymer of the thiol compound and the unsaturated compound has a sulfur atom in the molecule with a high content. Such a copolymer having a large number of sulfur atoms in the molecule can exhibit an extremely high refractive index as compared with an organic material conventionally used as a hologram recording material. Therefore, when an inorganic compound having a refractive index smaller than that of the copolymer is used as the inorganic compound used in combination with this copolymer, the refractive index difference based on the difference in composition generated in the recording material becomes larger, which causes diffraction. Efficiency is further increased.

  In the hologram recording material of the present invention, the unsaturated compound is preferably a compound having two or more functional groups containing an unsaturated bond. Such an unsaturated compound causes a polymerization reaction with a thiol compound very efficiently, and can give a copolymer having a higher degree of polymerization.

  Moreover, the functional group containing an unsaturated bond in the unsaturated compound is more preferably a functional group containing an ethylenically unsaturated bond, and more specifically, an acrylic group or a methacryl group can be mentioned as such a functional group. .

  Further, the unsaturated compound is more preferably one having a sulfur atom in the molecule. In this way, the refractive index of the copolymer copolymerized with the thiol compound is further increased, and when combined with an inorganic compound having a lower refractive index, a remarkably large refractive index difference can be generated. .

  In the hologram recording material of the present invention, it is more preferable that the thiol compound is contained in a molar amount of 0.2 to 0.7 times the total molar amount of the thiol compound and the unsaturated compound. When these polymerization reactions are caused at such a mixing ratio, the polymerization reaction between the thiol compound and the unsaturated compound proceeds very efficiently.

  Further, the inorganic compound having a refractive index different from that of the copolymer of the thiol compound and the unsaturated compound is more preferably an inorganic compound having a refractive index lower than that of the copolymer. As described above, a copolymer of a thiol compound and an unsaturated compound can exhibit a very high refractive index as compared with an organic material conventionally used as a hologram recording material. For this reason, a large difference in refractive index occurs when combined with an inorganic compound having a lower refractive index than this.

  More specifically, it is preferable that the inorganic compound has a fine particle shape. In this way, movement and diffusion of the monomer component and the inorganic compound during the polymerization reaction occur efficiently, and the difference in composition after recording is further increased.

  The hologram recording medium of the present invention is preferably provided with the hologram recording material of the present invention, and has a substrate, a thiol compound having two or more mercapto groups, and a functional group containing an unsaturated bond. And an unsaturated compound that polymerizes with the thiol compound, a photopolymerization initiator that initiates polymerization of the thiol compound and the unsaturated compound when irradiated with light, and a thiol compound and the unsaturated compound that are polymerized. A hologram recording material including a copolymer and an inorganic compound having a different refractive index, and a recording layer provided on a substrate.

  Furthermore, the present invention also provides a recorded hologram recording medium in which interference fringes are recorded by irradiating the above-described hologram recording medium with recording light. Such a hologram recording medium includes a substrate and a hologram recording layer formed on the substrate and having interference fringes recorded thereon. The hologram recording layer includes a thiol compound having two or more mercapto groups and an unsaturated group. It is a layer comprising a copolymer of an unsaturated compound that has a functional group containing a bond and is polymerized with a thiol compound, and an inorganic compound having a refractive index different from that of the copolymer. It is characterized by that.

  According to the hologram recording material of the present invention, extremely high diffraction efficiency can be obtained. As a result, a hologram recording medium using such a recording material can record information with high accuracy, and there is very little deterioration in information when information recorded from the hologram recording medium after recording is reproduced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a hologram recording medium of the present invention. The hologram recording medium 100 includes a recording layer 40 made of a hologram recording material on a base 20, and a protective layer 60 for protecting the layer is formed on the recording layer 40.

  The substrate 20 or the protective layer 60 used for this hologram recording medium is not particularly limited as long as it is formed from a material having transparency to light used for hologram recording. Examples of such a transparent substrate include a plate substrate such as a glass substrate, an acrylic plate, and a polycarbonate plate, and a film substrate such as a polyethylene film, a polynaphthalene film, and a polyethylene terephthalate film.

  The recording layer 40 has a thiol compound having two or more mercapto groups, an unsaturated compound having an unsaturated bond and polymerized with the thiol compound, and starts polymerization of the thiol compound and the unsaturated compound when irradiated with light. And a hologram recording material mainly containing four components of an inorganic compound having a refractive index different from that of a copolymer obtained by polymerizing a thiol compound and an unsaturated compound. Hereafter, each component which comprises this hologram recording material is explained in full detail.

  First, a thiol compound having two or more mercapto groups will be described. As the thiol compound, a compound having two or more mercapto groups in the molecule and capable of causing a polymerization reaction with an unsaturated compound described later in the mercapto group by irradiation with light can be used. As such a thiol compound, a compound further having a sulfur atom other than a mercapto group in the molecule is more preferable. By doing so, the content of sulfur atoms in the light irradiation part is further increased, and the refractive index of the part is further improved.

Examples of such thiol compounds include compounds represented by the following formulas (1a) to (1h). In the formula (1g), a represents an integer of 2 to 5.

  Next, the unsaturated compound will be described. An unsaturated compound is a compound having a functional group containing an unsaturated bond in the molecule and capable of causing a polymerization reaction with the above-described thiol compound. As such an unsaturated compound, those having two or more functional groups containing an unsaturated bond in the molecule are preferable. The polymerization reaction by irradiation of light in the hologram recording material proceeds by the reaction between the mercapto group of the thiol compound and the unsaturated group of the unsaturated compound.

  Examples of the functional group containing an unsaturated bond in the unsaturated compound include a functional group containing an ethylenically unsaturated bond, an isocyanato group, and an isothiocyanato group. More specifically, the functional group containing an ethylenically unsaturated bond is preferably an acryl group or a methacryl group. When an unsaturated compound having these functional groups is used, a polymerization reaction due to light irradiation is more likely to occur. .

  Furthermore, it is more preferable that the unsaturated compound has one or more sulfur atoms in the molecule. By carrying out like this, the copolymer with the above-mentioned thiol compound obtained by light irradiation comes to have a still higher refractive index.

  Examples of such unsaturated compounds include compounds having a (meth) acryl group as a functional group containing an unsaturated bond. Here, the (meth) acryl group means an acrylic group or a methacryl group, and (meth) acrylate means an acrylate or a methacrylate in the same manner hereinafter.

Examples of such a compound having an acrylic group include thio (meth) acrylate compounds represented by the following formulas (2a) to (2c).

In the formula, R ²¹ and R ²² each independently represent a hydrogen atom or a methyl group, R ²³ represents a hydrogen atom, a methyl group or an ethyl group, X represents an oxygen atom or a sulfur atom, i represents 1 or 2, j, k, n, m and r each independently represents 0 or 1. As the thio (meth) acrylate compounds represented by these formulas, first, as the compound represented by the above formula (2a), 1,2-bis (meth) acryloylthioethane, bis-2- (meth) acryloyl Examples thereof include thioethyl ether, bis-2- (meth) acryloylthioethyl sulfide, and bis-2- (meth) acryloylthioethylthiomethane.

Examples of the compound represented by the above formula (2b) include 1,2-bis (meth) acryloylthiobenzene, 1,3-bis (meth) acryloylthiobenzene, 1,4-bis (meth) acryloylthiobenzene. 1,2-bis (meth) acryloylthiomethylbenzene, 1,3-bis (meth) acryloylthiomethylbenzene, 1,4-bis (meth) acryloylthiomethylbenzene, 1,2-bis [2- (meta ) Acryloylthioethylthio] methylbenzene, 1,3-bis [2- (meth) acryloylthioethylthio] methylbenzene, 1,4-bis [2- (meth) acryloylthioethylthio] methylbenzene (the following formula ( 3a), 1,4-bis [2-methacryloyloxyethylthio] methylbenzene (in the following formula (3b) It includes compounds) such as to be. In the following formula (3a), R ³¹ represents a hydrogen atom or a methyl group.

Furthermore, examples of the compound represented by the formula (2c) include 1,2-bis [2- (meth) acryloylthioethylthio] -3- (meth) acryloylthiopropane, 1,2,3-tris [2 -(Meth) acryloylthioethylthio] propane (compound represented by the following formula (4)) can be exemplified. In the following formula (4), R ⁴¹ represents a hydrogen atom or a methyl group.

  Among these thio (meth) acrylate compounds, bis-2- (meth) acryloylthioethyl sulfide, which is a compound represented by the above formula (2a), 1, which is a compound represented by the above formula (2b), 2-bis (meth) acryloylthiomethylbenzene, 1,3-bis (meth) acryloylthiomethylbenzene or 1,4-bis (meth) acryloylthiomethylbenzene, a compound represented by the above formula (2c) 1 , 2-bis [2- (meth) acryloylthioethylthio] -3- (meth) acryloylthiopropane is preferred.

Moreover, as a compound which has a (meth) acryl group, the bis (meth) acrylate compound which does not have a sulfur atom in a molecule | numerator can also be used preferably. Examples of such bis (meth) acrylate compounds include bis (meth) acrylate having an aromatic ring in the molecule and bis (meth) acrylate having no aromatic ring in the molecule. For example, examples of the bis (meth) acrylate having an aromatic ring in the former molecule include those represented by the following formula (5).

In the formula, R ⁵¹ is a hydrogen atom or a methyl group, R ⁵² is an alkylene group having 1 to 6 carbon atoms which may have a substituent in the side chain, Ar is an arylene group having 6 to 30 carbon atoms, or an arylalkylene group , L represents an oxy group or a sulfide group. In addition, examples of the substituent on the side chain of R ⁵² include an alkyl group and a hydroxyl group, and the aromatic ring in the group represented by Ar may be substituted with a halogen atom other than fluorine. Further, Q in the formula represents a sulfide group, a sulfonyl group or a linear or branched alkylene group having 1 to 12 carbon atoms when L is an oxy group, and a sulfide group, a sulfonyl group when L is a sulfide group. A group, a carbonyl group, or a linear or branched alkylene group having 1 to 12 carbon atoms, an arylalkylene group, an alkyleneoxy group, an arylalkyleneoxy group, an alkylenethioether group, or an arylalkylenethioether group. Furthermore, p and t in a formula show the integer of 1-5, q shows the integer of 0-10. A plurality of groups may be the same or different.

Examples of the compound represented by the above formula (5) include p-bis (β-acryloyloxyethylthio) xylylene, p-bis (β-methacryloyloxyethylthio) xylylene, m-bis (β-acryloyloxyethylthio). Xylylene, m-bis (β-methacryloyloxyethylthio) xylylene, α, α'-bis (β-acryloyloxyethylthio) -2,3,5,6-tetrachloro-p-xylylene, α, α'- Bis (β-methacryloyloxyethylthio) -2,3,5,6-tetrachloro-p-xylylene, 4,4′-bis (β-acryloyloxyethoxy) diphenyl sulfide, 4,4′-bis (β- Methacryloyloxyethoxy) diphenyl sulfide, 4,4′-bis (β-acryloyloxyethoxyethoxy) diphenylsulfone, 4,4′-bis (β-methacryloyloxyethoxyethoxy) diphenylsulfone, 4,4′-bis (β-acryloyloxyethylthio) diphenyl sulfide, 4,4′-bis (β-methacryloyloxyethylthio) diphenyl sulfide 4,4′-bis (β-acryloyloxyethylthio) diphenylsulfone, 4,4′-bis (β-methacryloyloxydiethylthio) diphenylsulfone, 4,4′-bis (β-methacryloyloxyethylthio) diphenyl Ketone, β, β′-bis (p-acryloyloxyphenylthio) diethyl ether, β, β′-bis (p-methacryloyloxyphenylthio) diethyl ether, β, β′-bis (p-methacryloyloxyphenylthio) Diethyl ether, β, β′-bis (p-methacryloylio Shifeniruchio) diethyl thioether, 4,4'-bis (.gamma. (meth) compound represented by acryloyloxy -β- hydroxypropyloxy) diphenyl propane (formula (6)) and the like. In the following formula (6), R ⁶¹ represents a hydrogen atom or a methyl group.

  Among the compounds that can be represented by the above formula (5), compounds having a sulfur atom in the molecule are more preferable. Such compounds include p-bis [β- (meth) acryloyloxyisopropylthio] xylylene, m-bis [β- (meth) acryloyloxyethylthio] ethylphenylene, p-bis [β- (meth) acryloyl. Oxybutylthio] tetrachloroxylylene, p-bis [β- (meth) acryloyloxyethylthio] xylylene, m-bis [β- (meth) acryloyloxyethylthio] xylylene are polymers of thiol compounds. This is preferable because the refractive index tends to be higher.

Moreover, as bis (meth) acrylate which does not have an aromatic ring in a molecule | numerator, the compound represented by following formula (7a)-(7d) can be illustrated. Among them, a compound represented by the following formula (7d), which is a bis (meth) acrylate having a ring structure containing a sulfur atom in the molecule, is preferable because the refractive index of the polymer with the thiol compound can be increased. . In the following formulae, R ⁷¹ represents a hydrogen atom or a methyl group, b represents an integer of 4 to 22, and c represents an integer of 5 to 16.

Furthermore, a compound having a vinyl group as an unsaturated bond can also be used as the unsaturated compound. Examples of such a compound include compounds represented by the following formula (8a) or (8b).

Moreover, as a functional group containing an unsaturated bond that the unsaturated compound can have, as a functional group having an unsaturated bond other than the carbon-carbon double bond as described above, an isocyanato group or an isothiocyanato group can be mentioned, Examples of the unsaturated compound having these functional groups include compounds represented by the following formula (9a) or (9b).

  Next, the photopolymerization initiator will be described. The photopolymerization initiator is not particularly limited as long as it initiates polymerization of a thiol compound and an unsaturated compound by light irradiation, but a photopolymerization initiator generally known as a radical photopolymerization initiator is suitable. .

  Examples of such radical photopolymerization initiators include azo compounds, azide compounds, organic peroxides, onium salts, bisimidazole derivatives, titanocene compounds, iodonium salts, organic thiol compounds, halogenated hydrocarbon derivatives, and the like. Of these, titanocene compounds are preferred.

  The titanocene compound is not particularly limited, and specifically, di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, di-cyclopentadienyl-Ti-bis. -2,3,4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopenta Dienyl-Ti-bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,6-di-fluorophen-1-yl, di-cyclopentadienyl -Ti-bis-2,4-di-fluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di- Methylsiku Pentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl, di-methylcyclopenta And dienyl-Ti-bis-2,6-difluoro-3- (pyr-1-yl) -phen-1-yl.

In addition, the radical photopolymerization initiator can sufficiently initiate the polymerization reaction even when used alone, but when combined with a sensitizer that absorbs light, the polymerization reaction proceeds. Tend to be more promoted. Specific examples of such a preferred sensitizer include, for example, 2,6-diethyl-1,3,5,7,8-pentamethylpyromethene-BF ₂ complex, 1,3,5,7,8- Pyromethene complexes such as pentamethylpyromethene-BF ₂ complex; xanthene dyes such as eosin, ethyleosin, erythrosine, fluorescein, rose bengal; 1- (1-methylnaphtho [1,2-d] thiazole-2 (1H ) -Iridene-4- (2,3,6,7) tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) -3-buten-2-one, 1- (3-methylbenzothiazole-2 Ketothiazoline compounds such as (3H) -ylidene-4- (p-dimethylaminophenyl) -3-buten-2-one; 2- (p-dimethylaminostyryl) -naphtho [ , 2-d] thiazole, styryl or phenylbutadienyl heterocyclic compounds such as 2- [4- (p-dimethylaminophenyl) -1,3-butadienyl] -naphtho [1,2-d] thiazole; 2 , 4-Diphenyl-6- (p-dimethylaminostyryl) -1,3,5-triazine, 2,4-diphenyl-6-(([2,3,6,7] tetrahydro-1H, 5H-benzo [ ij] Triazine compounds such as quinolizin-9-yl) -1-ethen-2-yl) -1,3,5-triazone; 9-phenanthryl-(([2,3,6,7] tetrahydro-1H, Aminophenyl unsaturated keto such as 5H-benzo [ij] quinolizin-9-yl) -1-ethen-2-yl) ketone, 2,5-bis (p-dimethylaminocinnamylidene) cyclopentanone 5, 10, 15, 20 tetraphenylporphyrin, polyphyrins such as hematoporphyrin, etc. Among these, pyromethene complex is particularly preferable.

  Next, an inorganic compound having a refractive index different from that of a copolymer obtained by polymerizing a thiol compound and an unsaturated compound will be described. Such an inorganic compound can be used without particular limitation as long as it has a refractive index different from that of the copolymer and has properties such as transparency required as a hologram recording material. From the viewpoint of improving the diffraction efficiency of the hologram recording material, it is more preferable that such an inorganic compound has a refractive index difference of 0.1 to 0.5 with respect to the copolymer.

  Here, a copolymer of a thiol compound and an unsaturated compound produced by polymerization upon irradiation with light has an extremely high refractive index compared to a photopolymerizable monomer or the like conventionally used for hologram recording materials. . Therefore, from the viewpoint of effectively utilizing this high refractive index characteristic, it is preferable to use a low refractive index material having a refractive index smaller than that of the copolymer as the inorganic compound. By using a copolymer and a low refractive index material in combination, the refractive index difference caused by light irradiation can be further increased, and the diffraction efficiency of the hologram recording material is improved.

  Specific examples of such inorganic compounds include metal oxides such as silicon oxide, aluminum oxide, cerium oxide, magnesium oxide, beryllium oxide, boron oxide, and germanium oxide; silicon nitride, titanium nitride, zirconium nitride, and niobium nitride. Nitrides such as silicon carbide, titanium carbide, molybdenum carbide, tungsten carbide, etc., group IV semiconductor fine particles such as Si, Ge; CdS, CdSe, ZnSe, CdTe, ZnS, HgS, HgS, HgSe II-IV group semiconductor fine particles such as GaAs, InP, InSb, etc .; III-VI group semiconductor fine particles such as GaAs, InP, InSb; metal fine particles such as gold, silver, copper, nickel, aluminum, iron, cobalt, tungsten, molybdenum, niobium, polysilsesqui Examples include oxane and the like. Among these, a compound having a silicon atom is preferable because a smaller refractive index can be obtained.

  These inorganic compounds are more preferable if they are excellent in affinity with thiol compounds, unsaturated compounds, and copolymers thereof. If the inorganic compound has the property of having high affinity with the above components, these components are uniformly dispersed in the hologram recording material. In this case, the composition variation in the recording material is less likely to occur, and the recording error caused by the variation becomes small, so that more accurate recording can be performed. However, if this affinity is too high, the above-described thiol compound, unsaturated compound and inorganic compound may not easily move. For this reason, it is desirable that the affinity of the inorganic compound for the thiol compound, the unsaturated compound, and the polymer thereof is as high as possible within a range in which the movement of these components can sufficiently occur.

  Further, as described above, it is preferable that the thiol compound, unsaturated compound, and inorganic compound are mixed uniformly. For that purpose, the particle size of the inorganic compound is desired to be as small as possible. Practically, the particle size is preferably 100 nm or less, more preferably 50 nm or less. In this case, each component is uniformly diffused in the recording material, and the thiol compound and the unsaturated compound are easily diffused and moved during the polymerization of the copolymer, and the amount of these movements accompanying the polymerization also increases. Furthermore, since each component is uniformly mixed, the variation in characteristics of each medium can be greatly reduced, thereby improving the reliability of the recording medium.

Low refractive index compounds satisfying these characteristics include silicon oxide, which is a compound having a silicon atom, and polysilsesquioxane represented by (RSiO _1.5 ) _Z (where R is a hydrogen atom or an alkyl group, aryl A monovalent organic group such as a group, and z is an integer of 8 to 200).

  The hologram recording material constituting the recording layer 40 of the hologram recording medium 100 includes (A) a thiol compound, (B) an unsaturated compound, (C) an inorganic compound having a refractive index different from these polymers, and (D). It has a photopolymerization initiator as an essential component. In this recording material, these essential components (A) to (D) are preferably blended in the proportions shown below. That is, first, the (A) component and the (B) component have a ratio (A) / ((A) + (B)) of preferably 0.2 to 0.7, more preferably 0.3 to It mix | blends so that the relationship used as 0.5 may be satisfy | filled. In this way, the reaction between the component (A) and the component (B) occurs more efficiently.

  In addition to this, the component (C) is preferably contained in an amount of about 10 to 80 parts by mass with respect to a total of 100 parts by mass of the components (A), (B) and (C), and the component (D) , (A), (B) and (C) It is preferable to contain about 0.05 to 20 parts by mass with respect to 100 parts by mass in total. When each of the components (A) to (D) satisfies such a blending amount, a difference in refractive index between a portion having a high light intensity and a portion having a small light intensity during recording can be increased, and high diffraction efficiency can be obtained. It becomes like this. In the present invention, “part by mass” is substantially equivalent to a weight reference value (“part by weight”) (hereinafter the same).

  In addition to the essential components described above, the hologram recording material may contain other components to the extent that the hologram recording is not affected. As other components, for example, when a film made of a hologram recording material is formed, a binder such as an acrylic resin capable of improving the strength of the film can be exemplified.

  Next, an example of a method for manufacturing the hologram recording medium 100 according to the present embodiment will be described. The hologram recording medium 100 can be manufactured by a method in which the protective layer 60 is deposited on the recording layer 40 after the recording layer 40 is formed on the substrate 20. As a method for forming the recording layer 40 made of the hologram recording material of the present invention on the substrate 20, a solution prepared by mixing each component in a predetermined blending amount and dissolving or dispersing in a predetermined solvent is dropped onto the substrate 20. Alternatively, a method of removing the solvent by heating or the like after coating on the substrate 20 by a known means such as a spin coater, roll coater, bar coater or the like can be exemplified. In addition, a method in which a recording layer 40 is formed between the base 20 and the protective layer 60 by filling a solution containing the hologram recording material into a mold using the base 20 and the protective layer 60 as parallel flat plates and then performing pressure bonding. In addition, the hologram recording medium 100 can be manufactured.

  The hologram recording medium 100 configured as described above can record a hologram as follows. That is, first, light having the information to be recorded (object light) and light having no information (reference light) are irradiated to the same position of the recording layer 40 from different angles. When the object light and the reference light are irradiated, the hologram recording material constituting the recording layer 40 generates a copolymer by causing a polymerization reaction between the thiol compound and the unsaturated compound at the irradiated portion. In this case, since the thiol compound and the unsaturated compound consumed by the polymerization reaction are compensated, each component diffuses and moves from a peripheral site where the light intensity is weak to a site where the polymerization reaction occurs. As the monomer component moves, the inorganic compound having a refractive index different from that of the copolymer is pushed out from the site where the polymerization reaction occurs and diffuses / moves to the site where the light intensity is weak.

  By such diffusion and movement, a region where the copolymer exists at a high concentration and a region where the inorganic compound exists at a high concentration are formed in the recording material corresponding to the intensity of the irradiated light. Here, in the part irradiated with the object light and the reference light, interference fringes are formed by the interference of the two lights. Therefore, the difference in composition between the regions corresponds to the intensity of light due to the interference fringes. In this case, since the copolymer of the thiol compound and the unsaturated compound and the inorganic compound have different refractive indexes, the hologram recording material has light intensity caused by interference fringes based on the difference in the composition. Corresponding refractive index differences are generated. Thus, the interference fringes are recorded as a difference in refractive index generated in the recording material.

  In the hologram recording medium 100, interference fringes are recorded in this way, and a hologram recording medium on which predetermined information is recorded is obtained. The hologram recording medium after recording is composed of a substrate and a hologram recording layer formed on the substrate. Further, the hologram recording layer includes a thiol compound having two or more mercapto groups, a copolymer of an unsaturated compound having a functional group containing an unsaturated bond and polymerized with the thiol compound, and the copolymer And an inorganic compound having a different refractive index. In the recording layer, a predetermined distribution is generated in the composition ratio of the copolymer and the inorganic compound, and interference fringes are recorded by the predetermined distribution.

  The information recorded on the hologram recording medium in this way is irradiated with the same light as the reference light used at the time of recording, and the irradiated light is diffracted by the hologram, thereby having the original information. It can be read out by regenerating light.

  The hologram recording medium 100 on which hologram recording is performed as described above has a recording layer 40 composed of a hologram recording material containing a highly polymerizable thiol compound and unsaturated compound. Since such a recording material has such a high polymerizability, the degree of polymerization varies greatly according to the intensity of light. For this reason, the movement of the thiol compound and the unsaturated compound that accompanies this polymerization reaction also occurs greatly, and as a result, a large refractive index change occurs in the recording material corresponding to the intensity of light. Thereby, high diffraction efficiency is achieved.

  In addition, a copolymer of a thiol compound and an unsaturated compound formed by light irradiation has a very high refractive index, so when used in combination with an inorganic compound having a low refractive index, The difference in refractive index between the strong part and the weak part becomes larger, and higher diffraction efficiency can be obtained.

  In addition, the inorganic compound, which is a low refractive index material contained in the recording layer, is unlikely to undergo a volume change due to heat or the like, so the effect of the volume change of each monomer component that occurs during recording (during polymerization) Can be relaxed to an almost negligible level. As a result, it becomes possible to record interference fringes more accurately than recording materials that have been used to record holograms using the polymerization reaction of conventional monomers, resulting in data degradation during reproduction, etc. Is also greatly reduced.

[Creation of hologram recording medium]
(Examples 1-12)
1 to 73 parts by weight of a compound represented by the following formula (10) which is a thiol compound, 99 to 27 parts by weight of a compound represented by the following formula (11) which is an unsaturated compound, and an organosilica sol (30 wt. % Isopropanol solution, OSCAL1432, Catalytic Chemical Co., Ltd.) 300 parts by weight, titanocene derivative (IRG-784, Ciba Geigy) 5 parts by weight as a photopolymerization initiator, and 3,3′-carbamylbis as a sensitizing dye 1 part by weight of -7-diethylaminocoumarin (compound represented by the following formula (12)) was prepared and dissolved in 100 parts by weight of tetrahydrofuran to obtain a solution of a hologram recording material. In addition, the compounding quantity of a thiol compound and an unsaturated compound was adjusted so that both total might be 100 weight part.

  Next, the obtained solution was dropped on the central part of the slide glass with a 50 μm thick polyethylene terephthalate film stretched at both ends, and then dried under reduced pressure for 24 hours. A recording layer made of the composition from which the solvent was removed was formed. Thereafter, a slide glass as a protective layer was placed on the recording layer to produce a hologram recording medium having a structure in which the recording layer was sandwiched between a pair of slide glasses. The content of the thiol compound is 1, 2, 5, 10, 20, 30, 37, 40, 50, 60, and 73 parts by weight with respect to 100 parts by weight of the total of the thiol compound and the unsaturated compound. The obtained hologram recording media were changed to Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11, respectively.

(Comparative Example 1)
Example except that 100 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate was used alone in place of the thiol compound represented by the above formula (10) and the unsaturated compound represented by the above formula (11). In the same manner as in Example 1, a hologram recording medium was obtained.

[Recording hologram]
Two-beam interference exposure was performed on the hologram recording media obtained in Examples 1 to 11 and Comparative Example 1, and holograms were recorded on the recording material in the recording media. FIG. 2 is a schematic view showing an exposure apparatus used for hologram recording and reproduction. In this two-beam interference exposure, a doubled-YAG laser (λ = 532 nm) is used as the light source 2 of the exposure apparatus 1, and laser light emitted at an exposure power of 5 mW / cm ² is passed through the beam expander 4. The laser beam is divided into two by the half mirror 6, and further, the respective laser beams are reflected by the mirrors 8 and 10 to irradiate the same portion of the hologram recording medium 12, and the interference fringes generated by the two laser beams are recorded on the recording material. Recorded. At this time, the exposure was performed with the neutral density filter 16 and the shutter 18 of the exposure apparatus 1 being open (the neutral density filter 16 is located at the position 16b).

[Diffraction efficiency measurement]
The exposure apparatus 1 used at the time of recording was used for the hologram recording media of Examples 1 to 11 and Comparative Example 1 in which the hologram was recorded by the above-described method, and the neutral density filter 16 and the shutter 18 were closed (the neutral density filter 16 Is placed at the position 16a), the recording medium is irradiated with laser light to reproduce the hologram, and the diffracted light at this time is detected by the photodetector 14, and the diffraction efficiency of each hologram recording medium is measured. did.

  FIG. 3 is a graph showing diffraction efficiency with respect to the content of the thiol compound obtained by measurement of each hologram recording medium of Examples 1 to 11. From FIG. 3, it was found that the hologram recording medium of the present invention exhibits good diffraction efficiency when the thiol compound content is 30 to 50 parts by weight.

  4 is a bar graph showing diffraction efficiencies obtained with the hologram recording medium of Example 7 (thiol compound content: 37 parts by weight) and Comparative Example 1. FIG. From FIG. 4, it was found that according to the hologram recording medium of Example 7 containing a thiol compound and an unsaturated compound, a higher diffraction efficiency was obtained compared to the recording medium of Comparative Example 1 that did not contain both. .

It is sectional drawing which shows typically the hologram recording medium of this invention. It is the schematic which shows the exposure apparatus used for recording and reproduction | regeneration of a hologram. It is a graph which shows the diffraction efficiency with respect to content of the thiol compound obtained by the measurement of each hologram recording medium of Examples 1-11. 6 is a bar graph showing diffraction efficiency obtained with the hologram recording media of Example 7 and Comparative Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Base | substrate, 40 ... Recording layer, 60 ... Protective layer, 100 ... Hologram recording medium.

Claims (10)

  A thiol compound having two or more mercapto groups, an unsaturated compound having a functional group containing an unsaturated bond and polymerized with the thiol compound, and the thiol compound and the unsaturated compound when irradiated with light, A hologram recording material comprising: a photopolymerization initiator for initiating polymerization; and an inorganic compound having a different refractive index from a copolymer obtained by polymerizing the thiol compound and the unsaturated compound.   The hologram recording material according to claim 1, wherein the unsaturated compound is a compound having two or more functional groups containing the unsaturated bond.   The hologram recording material according to claim 1, wherein the unsaturated compound has a functional group containing an ethylenically unsaturated bond as a functional group containing the unsaturated bond.   The hologram recording material according to claim 1, wherein the unsaturated compound has an acryl group or a methacryl group as a functional group containing the unsaturated bond.   The hologram recording material according to claim 1, wherein the unsaturated compound is a compound containing a sulfur atom in the molecule.   The hologram recording material according to claim 1, wherein the thiol compound is contained in a molar amount of 0.2 to 0.7 times the total molar amount of the thiol compound and the unsaturated compound. .   The inorganic compound having a refractive index different from that of a copolymer obtained by polymerizing the thiol compound and the unsaturated compound is an inorganic compound having a refractive index smaller than that of the copolymer. The hologram recording material according to any one of 1 to 6.   The hologram recording material according to claim 1, wherein the inorganic compound is an inorganic compound having a fine particle shape. A substrate;
A thiol compound having two or more mercapto groups, an unsaturated compound having a functional group containing an unsaturated bond and polymerized with the thiol compound, and the thiol compound and the unsaturated compound when irradiated with light, A hologram recording material comprising: a photopolymerization initiator for initiating polymerization; and an inorganic compound having a different refractive index from a copolymer obtained by polymerizing the thiol compound and the unsaturated compound, A recording layer provided on a substrate;
A hologram recording medium comprising: A hologram recording medium comprising a substrate and a hologram recording layer formed on the substrate and recorded with interference fringes,
The hologram recording layer includes a copolymer of a thiol compound having two or more mercapto groups, an unsaturated compound having a functional group containing an unsaturated bond and polymerized with the thiol compound, and the copolymer A layer containing an inorganic compound having a refractive index different from that of the coalescence,
Hologram recording medium.

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