JP2010066326A - Hologram recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording medium that is additionally recordable without a special pre-exposure schedule. <P>SOLUTION: The hologram recording medium has a recording layer containing a radical polymerizable monomer having an ethylenic unsaturated bond, a photo-radical polymerization initiator, a polymer matrix and a polymerization inhibitor. The polymerization inhibitor is selected out of a group consisting of a phenol derivative, hindered amine and nitroxide compound, and bonded to the polymer matrix by covalent-binding. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hologram recording medium.

  Holographic memories that record information as holograms are capable of high-capacity recording and are attracting attention as next-generation recording media. As a photosensitive composition for hologram recording, for example, a radical polymerizable photopolymer mainly composed of a radical polymerizable monomer, a thermoplastic binder resin, a photo radical polymerization initiator, and a sensitizing dye is known.

  Currently, higher sensitivity is demanded of photosensitive compositions for hologram recording. However, the more sensitive the medium is, the less sensitive the light is. For example, it is assumed that an undesirable reaction starts and proceeds in the medium by irradiation with natural light or the like. It is also assumed that similar undesirable reactions are caused by thermal external stimuli during storage. In order to prevent polymerization (dark reaction) during storage, a small amount of a polymerization inhibitor is generally dispersed in the recording layer (see, for example, Patent Document 1).

  In such a hologram recording medium, it is necessary to perform pre-recording exposure to deactivate the polymerization inhibitor immediately before recording. For example, the pre-recording exposure is sequentially performed limited to only the required recording area. Since the polymerization inhibitor is freely diffusing into the recording layer, the concentration of the polymerization inhibitor in the recording area decreases as the latter half of the pre-exposure processing. The concentration of the polymerization inhibitor in the recording area is complicated by various factors, such as the ratio of the entire pre-exposed area, the elapsed time after the pre-exposure process, and the diffusibility of the polymer matrix that forms the recording layer. It is calculated by being entangled with each other, and it is not easy to calculate the concentration.

In order to calculate the density and calculate the pre-exposure processing schedule, and to perform the pre-exposure processing according to the schedule, a complicated system is required. Therefore, a hologram recording medium capable of simpler recording is required. .
JP-A-7-5796

  An object of the present invention is to provide a hologram recording medium which can be additionally recorded without a special pre-exposure schedule.

A hologram recording medium according to an aspect of the present invention includes a recording layer containing a radical polymerizable monomer having an ethylenically unsaturated bond, a photo radical polymerization initiator, a polymer matrix, and a polymerization inhibitor.
The polymerization inhibitor is selected from the group consisting of phenol derivatives, hindered amines, and nitroxide compounds, and is bonded to the polymer matrix through a covalent bond.

  According to the present invention, there is provided a hologram recording medium that can be additionally recorded without a special pre-exposure schedule.

  Embodiments of the present invention will be described below.

  The recording layer in the hologram recording medium according to the embodiment of the present invention contains a polymer matrix having a radical polymerizable monomer having an ethylenically unsaturated bond, a photo radical polymerization initiator, and a covalently bonded polymerization inhibitor.

  Examples of the radical polymerizable monomer having an ethylenically unsaturated bond include unsaturated carboxylic acid, unsaturated carboxylic acid ester, unsaturated carboxylic acid amide, and vinyl compound.

  Specifically, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, bicyclopentenyl acrylate , Phenyl acrylate, 2,4,6-tribromophenyl acrylate, isobornyl acrylate, adamantyl acrylate, methacrylic acid, methyl methacrylate, propyl methacrylate, butyl methacrylate, phenyl methacrylate, phenoxyethyl acrylate, chlorophenyl acrylate , Adamantyl methacrylate, isobornyl methacrylate, N-methylacrylamide, N, N-dimethylacrylamide, N, N- Tylene bisacrylamide, acryloylmorpholine, vinyl pyridine, styrene, bromostyrene, chlorostyrene, tribromophenyl acrylate, trichlorophenyl acrylate, tribromophenyl methacrylate, trichlorophenyl methacrylate, vinyl benzoate, 3,5-dichlorovinyl benzoate, vinyl naphthalene, Vinyl naphthoate, naphthyl methacrylate, naphthyl acrylate, N-phenyl methacrylamide, N-phenyl acrylamide, N-vinyl pyrrolidinone, N-vinyl carbazole, 1-vinyl imidazole, bicyclopentenyl acrylate, 1,6-hexanediol diacrylate, penta Erythritol triacrylate, pentaerythritol tetraacrylate, dipipe Data hexaacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, tripropylene glycol diacrylate, propylene glycol trimethacrylate, diallyl phthalate, and triallyl trimellitate and the like.

  Due to the high reactivity and refractive index, the radical polymerizable monomers include N-vinylcarbazole, vinylnaphthalene, bromostyrene, chlorostyrene, tribromophenyl acrylate, trichlorophenyl acrylate, tribromophenyl methacrylate, and trichlorophenyl methacrylate. Particularly preferred.

  The radical polymerizable monomer is preferably mixed so as to be contained in an amount of 1 to 50% by weight in the recording layer. If it is less than 1% by weight, a sufficient change in refractive index may not be obtained, and if it exceeds 50% by weight, volume shrinkage may increase and resolution may be lowered. The content of the radical polymerizable monomer is more preferably 3 to 30% by weight.

  The radical photopolymerization initiator can be selected according to the wavelength of the recording light. Examples include benzoin ether, benzyl ketal, benzyl, acetophenone derivatives, aminoacetophenones, benzophenone derivatives, acylphosphine oxides, triazines, imidazole derivatives, organic azide compounds, titanocenes, organic peroxides, and thioxanthone derivatives. .

  Specifically, benzyl, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, benzyl methyl ketal, benzyl ethyl ketal, benzyl methoxy ethyl ether, 2,2′-diethyl Acetophenone, 2,2′-dipropylacetophenone, 2-hydroxy-2-methylpropiophenone, p-tert-butyltrichloroacetophenone, thioxanthone, 1-chlorothioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2-isopropyl Thioxanthone, 3,3′4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-tris (trichloromethyl) ) 1,3,5-triazine, 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) 1,3,5-triazine, 2-[(p-methoxyphenyl) ethylene] -4,6 -Bis (trichloromethyl) 1,3,5-triazine, diphenyl- (2,4,6-trimethylbenzoyl) phosphine oxide, Irgacure 149, 184, 369, 651, 784, 819, 907 manufactured by Ciba Specialty Chemicals, Numbers such as 1700, 1800, 1850, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxyphthalate, t-butyl peroxy Benzoate, acetyl peroxide, isobutyryl peroxide, Kano Lee looper oxide, lauroyl peroxide, benzoyl peroxide, t- butyl hydroperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide, and cyclohexanone peroxide.

  When a blue semiconductor laser is used as the recording light, a titanocene compound such as Irgacure 784 (Ciba Specialty Chemicals) is suitable as the photo radical polymerization initiator.

  The radical photopolymerization initiator is preferably blended in such an amount that the light transmittance with respect to the recording light of the optical recording medium is 10% to 95%. If it is less than 10%, the sensitivity and diffraction efficiency may be reduced, and if it exceeds 95%, most of the recording light is transmitted, and there is a possibility that information to be recorded cannot be recorded sufficiently. More preferably, the amount is such that the light transmittance of the optical recording medium with respect to the recording light is 20% to 90%.

  Further, the amount of the radical photopolymerization initiator is preferably 0.1 to 20% by weight based on the recording layer. If it is less than 0.1% by weight, there is a possibility that a sufficient change in refractive index cannot be obtained. On the other hand, if it exceeds 20% by weight, the light absorption becomes too large and the sensitivity and diffraction efficiency may be lowered. More preferably, the amount of the radical photopolymerization initiator is 0.2 to 10% by weight with respect to the recording layer.

  As the polymer matrix, one formed by the following polymerization reaction can be used. For example, epoxy-amine polymerization, epoxy-acid anhydride polymerization, epoxy-mercaptan polymerization, polymerization of unsaturated esters and amines by Michael addition, urethane formation by isocyanate and hydroxyl, urea formation by isocyanate and hydroxyl, and For example, a bond between ethynyl and azide. As the polymerization reaction, epoxy-amine polymerization and epoxy-acid anhydride polymerization are particularly preferable because the reaction proceeds gently.

  Specific examples of the compound that reacts with epoxy include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, mensendiamine, isophoronediamine, bis (4-amino-3- Methyldicyclohexyl) methane, bis (aminomethyl) cyclohexane, N-aminoethylpiperazine, m-xylylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, trimethylhexamethylenediamine, iminobispropylamine, bis ( Hexamethylene) triamine, 1,3,6-trisaminomethylhexane, dimethylaminopropylamine, aminoethylethanolamine, tri (methylamino) hexane, m-phenylenediamine, -Phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, 3,3'-diethyl-4,4'-diaminodiphenylmethane, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyl nadic anhydride, Hexahydrophthalic anhydride, methylhexahydrophthalic acid, methylcyclohexene tetracarboxylic anhydride, phthalic anhydride, trimellitic anhydride, benzophenone tetracarboxylic anhydride, dodecenyl succinic anhydride, ethylene glycol bis (anhydro trimellitate) Phenol novolak resin, cresol novolak resin, polyvinylphenol, terpene phenol resin, and polyamide resin.

  In forming the polymer matrix, a curing catalyst may be added as necessary. As the curing catalyst, a basic catalyst can be used, and examples thereof include tertiary amines, organic phosphine compounds, imidazole compounds and derivatives thereof. Specifically, triethanolamine, piperidine, N, N′-dimethylpiperazine, 1,4-diazadicyclo (2,2,2) octane (triethylenediamine), pyridine, picoline, dimethylcyclohexylamine, dimethylhexylamine, benzyl Dimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, DBU (1,8-diazabicyclo [5,4,0] undec-7-ene), or its phenol Salt, trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazo Le, 2-phenyl-4-methylimidazole, and 2-hepta-imidazole and the like, it can be used as a curing catalyst.

  A latent catalyst can also be used, and examples thereof include boron trifluoride amine complex, dicyandiamide, organic acid hydrazide, diaminomaleonitrile and derivatives thereof, melamine and derivatives thereof, and amine imide. Furthermore, it is also possible to add a compound having active hydrogen, such as phenols or salicylic acid, to accelerate the curing of the three-dimensional crosslinked polymer matrix.

  Polymeric inhibitors selected from phenol derivatives, hindered amines, and nitroxide compounds are bound to such polymer matrices via covalent bonds. Among the polymerization inhibitors, nitroxides, which are difficult to be affected by the polymer matrix formation reaction in the polymerization matrix formation described above, are particularly suitable.

  Nitroxide usually exhibits yellow to red color, and the recording layer is colored by adding it to the recording layer. However, when nitroxide recombines with a radical to become alkoxyamine, it is presumed to decolorize. That is, when a radical generated during storage is trapped, the nitroxide changes to alkoxylamine and decolorizes. Also, when the radicals generated by the pre-exposure treatment are trapped, the nitroxide is transformed into alkoxylamine and decolorized. That is, even if it is colored at the time of forming the recording layer, it becomes transparent through a dark reaction at the time of storage and a pre-exposure process, so that there is no adverse effect at the time of recording.

  If the polymerization inhibitor is contained in an amount of 0.0001 part or more by weight of the radical photopolymerization initiator, the effect can be obtained. However, when it is contained at a concentration higher than that of the photo radical polymerization initiator, there is a possibility that all radicals generated from the photo radical polymerization initiator are trapped and recording becomes impossible. Therefore, it is desirable that the concentration of the polymerization inhibitor is limited to 1 part of the weight of the radical photopolymerization initiator. The concentration of the polymerization inhibitor is more preferably from 0.0001 part to 0.5 part of the radical photopolymerization initiator.

  The polymerization inhibitor can be selected according to the constituent components of the polymer matrix. For example, a polymerization inhibitor having an acrylic group, a methacryl group, an epoxy group, or an acyl halide group at one end can be used for a polymer matrix containing active hydrogen such as a secondary amine or a primary amine. These end groups react with the active hydrogen of the polymer matrix. In addition, a polymerization inhibitor having a hydroxyl group, an amino group, a mercapto group, or an epoxy group at one end can be used for a polymer matrix containing an epoxy group as a constituent component. These end groups react with the epoxy groups of the polymer matrix. In either case, the polymerization inhibitor breaks the covalent bond and binds to the polymer matrix.

  Specifically, the following compounds are more preferable as the polymerization inhibitor. That is, 4-methacryloyl-2,2,6,6-tetramethylpiperidine-N-oxide, 4-acryloyl-2,2,6,6-tetramethylpiperidine-N-oxide, 4-methacamide-2,2, 6,6-tetramethylpiperidine-N-oxide, 4-acrylamido-2,2,6,6-tetramethylpiperidine-N-oxide, 4-amino-2,2,6,6-tetramethylpiperidine-N- Oxide, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxide, 4-mercapto-2,2,6,6-tetramethylpiperidine-N-oxide, and 4-glycidyl ether-2, 2,6,6-tetramethylpiperidine-N-oxide and the like.

  When the polymerization inhibitor as described above is incorporated into the polymer matrix, it is desirable not to inhibit the formation of the polymer matrix. However, since the concentration of the polymerization inhibitor in the recording layer is originally very small, even if it is incorporated into the polymer matrix through a reaction that inhibits the formation of the polymer matrix, the formation of the polymer matrix is not significantly affected. Absent.

  In producing a hologram recording medium according to an embodiment of the present invention, first, a radical polymerizable monomer as described above, a radical polymerization initiator, a polymerization inhibitor having a bonding group bonded to a polymer matrix through a covalent bond, A polymer matrix constituent component is mixed to prepare a recording layer raw material solution. In the recording layer raw material solution, a crosslinking agent, a sensitizer, and a plasticizer may be blended as necessary. A recording layer is formed by forming a resin layer on a predetermined substrate using the obtained recording layer raw material solution and forming a polymer matrix.

  For example, a recording layer raw material solution is applied on a transparent substrate to form a recording layer. As the transparent substrate, for example, a glass substrate and a plastic substrate can be used, and before the recording layer raw material solution is applied, the surface of the substrate is easily selected from corona discharge treatment, plasma treatment, ozone treatment, alkali treatment, and the like. An adhesion treatment may be performed. In applying the solution, casting or spin coating can be employed. Alternatively, the recording layer may be formed by disposing two transparent substrates via resin spacers and pouring the recording layer raw material solution into the gap therebetween.

  The polymer matrix proceeds even at room temperature when an aliphatic primary amine is used as the curing agent. You may heat to the temperature of 30 to 150 degreeC according to the reactivity of a hardening | curing agent. The thickness of the recording layer to be formed is preferably 20 μm or more and 2 mm or less, and more preferably 50 μm or more and 1 mm or less. When the thickness of the recording layer is less than 20 μm, it is difficult to obtain a sufficient storage capacity. On the other hand, if the thickness of the recording layer exceeds 2 mm, the sensitivity and diffraction efficiency may be reduced.

  FIG. 1 is a schematic cross-sectional view of a hologram recording medium according to an embodiment of the present invention. In the illustrated hologram recording medium 10, a recording layer 13 is disposed between a pair of transparent substrates 11 and 15. The recording layer 13 contains a polymer matrix having a radical polymerizable monomer, a photo radical polymerization initiator, and a covalently bonded polymerization inhibitor as described above.

  FIG. 2 is a schematic view of a cross section of a hologram recording medium according to another embodiment. In the illustrated hologram recording medium 40, the recording layer 43 is sequentially provided on the transparent substrate 47 provided with the reflective layer 46 via the gap layer 45. That is, it is a hologram recording medium with a reflective layer. The reflective layer 46 can be formed of, for example, aluminum, and the gap layer 45 can be formed of, for example, a transparent resin or glass.

  A transparent substrate 41 is disposed on the recording layer 43. As in the case of the transmissive hologram recording medium 10 shown in FIG. 1, the recording layer 43 in the hologram recording medium 40 with a reflective layer shown in FIG. 2 also has a radical polymerizable monomer, a photo radical polymerization initiator as described above, And a polymer matrix having a covalently bonded polymerization inhibitor.

  Hologram recording is performed on the hologram recording medium according to the embodiment of the present invention by causing information light and reference light to interfere with each other inside the recording layer. The hologram to be recorded (holography) may be either a transmission hologram (transmission holography) or a reflection hologram (reflection holography). The interference between the information beam and the reference beam can be performed by either the two-beam interference method or the coaxial interference method.

  FIG. 3 shows a schematic diagram of an example of a transmission hologram recording / reproducing apparatus according to an embodiment of the present invention. The illustrated hologram recording / reproducing apparatus is a hologram type optical information recording / reproducing apparatus using a transmission type two-beam interference method.

  The light beam emitted from the light source device 21 passes through the beam expander 22 and the optical rotation optical element 23 and is introduced into the deflection beam splitter 24. As the light source device 21, a light source that emits arbitrary light that can interfere in the recording layer 13 of the transmission hologram recording medium 10 can be used. From the viewpoint of coherence, a linearly polarized laser is desirable. Examples of the laser include a semiconductor laser, a He—Ne laser, an argon laser, and a YAG laser.

  The beam expander 22 expands the light emitted from the light source device 21 to a beam diameter suitable for hologram recording. The optical rotatory optical element 23 rotates the light whose beam diameter is expanded by the beam expander 22 to generate light including an S-polarized component and a P-polarized component. For example, a half-wave plate and a quarter-wave plate can be used as the optical rotatory optical element 23.

  Of the light transmitted through the optical rotatory optical element 23, the S-polarized component is reflected by the polarization beam splitter 24 and used as information light I. On the other hand, the P-polarized component is transmitted through the polarization beam splitter 24 and used as the reference light Rf. The optical rotation direction incident on the polarization beam splitter 24 is adjusted by the optical rotation optical element 23 so that the intensity of the information light I and the intensity of the reference light Rf are equal at the position of the recording layer 13 of the transmission hologram recording medium 10. Is done.

  The information light I reflected by the polarization beam splitter 24 is reflected by the mirror 26, passes through the electromagnetic shutter 28, and is irradiated onto the recording layer 13 of the transmission hologram recording medium 10 placed on the rotary stage 20. Is done.

  On the other hand, the reference light Rf transmitted through the polarization beam splitter 24 is rotated by 90 degrees in the polarization direction by the optical rotatory optical element 25 to become S-polarized light and reflected by the mirror 27. Thereafter, the recording layer 13 of the transmission hologram recording medium 10 placed on the rotary stage 20 is irradiated through the electromagnetic shutter 29. In the recording layer 13, interference fringes are generated by intersecting with the information light I, and thus a transmission hologram is formed in the refractive index modulation region (not shown).

  To reproduce the recorded information, the information light I is blocked by closing the electromagnetic shutter 28, and a transmission hologram (not shown) formed in the recording layer 13 of the transmission hologram recording medium 10 is used. Only the reference light Rf is irradiated. A part of the reference light Rf is diffracted by the transmission hologram when passing through the transmission hologram recording medium 10. The diffracted light at this time is detected by the photodetector 30. In addition, a photodetector 31 is provided to detect light transmitted through the medium.

  In order to perform projection exposure on the recording medium after hologram recording, an ultraviolet light source device 32 and an ultraviolet light irradiation optical system can be provided as shown in the figure. By these, when an unreacted radical polymerizable monomer is polymerized, the stability of the recorded hologram can be improved. As the ultraviolet light source device 32, any light source that irradiates light capable of polymerizing an unreacted radical polymerizable monomer can be used. Considering the ultraviolet emission efficiency, for example, a xenon lamp, a mercury lamp, a high-pressure mercury lamp, a mercury xenon lamp, a gallium nitride based light emitting diode, a gallium nitride based semiconductor laser, an excimer laser, a third harmonic (355 nm) of an Nd: YAG laser, And the fourth harmonic (266 nm) of an Nd: YAG laser is preferable.

  FIG. 4 shows a schematic diagram of an example of a reflection type hologram recording / reproducing apparatus according to an embodiment of the present invention. As the light source device 51, it is desirable to use a laser that outputs coherent linearly polarized light as in the case of the transmission hologram recording / reproducing device. As the laser, for example, a semiconductor laser, a He—Ne laser, an argon laser, a YAG laser, or the like can be used.

  The light beam emitted from the light source device 51 is expanded in beam diameter by the beam expander 52 and enters the optical rotation optical element 53 as a parallel light beam. As the optical rotatory optical element 53, for example, a ½ wavelength plate, a ¼ wavelength plate, or the like can be used. The optical rotatory optical element 53 rotates the polarization plane of the light beam to generate a polarization component whose polarization plane is parallel to the paper surface (P polarization component) and a polarization component whose polarization plane is perpendicular to the paper surface (S polarization component). Generate light that contains. The light including the P-polarized component and the S-polarized component can also be generated by making the light beam circularly polarized or elliptically polarized.

  The S-polarized component of the light beam that has passed through the optical rotatory optical element 53 is reflected by the polarization beam splitter 54 and enters the transmissive spatial light modulator 55. On the other hand, the P-polarized component of the light beam emitted from the optical rotatory optical element 53 is transmitted through the polarization beam splitter 54 and used as reference light as will be described later.

  The transmissive spatial light modulator 55 has a large number of pixels arranged in a matrix like a transmissive liquid crystal display device, for example, and switches the light emitted from each pixel to a P-polarized component or an S-polarized component. Can do. In this way, the transmissive spatial light modulator 55 emits information light having a two-dimensional polarization plane distribution corresponding to the recorded information.

  Information light emitted from the transmissive spatial light modulator 55 enters the polarization beam splitter 56. The polarization beam splitter 56 reflects only the S-polarized component of the information light and transmits the P-polarized component. The S-polarized component reflected by the polarization beam splitter 56 passes through the electromagnetic shutter 57 as information light having a two-dimensional intensity distribution and enters the polarization beam splitter 58. This information light is reflected by the polarizing beam splitter 58 and enters the optical element 59 for two-part optical rotation.

  The optical element 59 for two-part optical rotation has different optical characteristics between the right side portion and the left side portion in the figure. Specifically, for example, the light component incident on the right side portion of the optical element 59 for two-part optical rotation rotates by rotating the polarization plane by + 45 °, and the light component incident on the left portion rotates the polarization plane by −45 °. Exit. Hereinafter, the polarization plane of the S polarization component rotated by + 45 ° (or the polarization plane of the P polarization component rotated by −45 °) is referred to as an A polarization component, and the polarization plane of the S polarization component is rotated by −45 °. The one (or the polarization plane of the P-polarized component rotated by + 45 °) is referred to as the B-polarized component. For example, a half-wave plate can be used for each part of the optical element 59 for two-part optical rotation.

  The A-polarized component and the B-polarized component emitted from the two-part optical rotatory optical element 59 are incident on the hologram recording medium with a reflective layer 40 through the objective lens 60 and pass through the transparent substrate 41, the recording layer 43, and the gap layer 45. The light is condensed on the reflective layer 46 on the transparent substrate 47.

  On the other hand, a part of the P-polarized component (reference light) transmitted through the polarizing beam splitter 54 is reflected by the beam splitter 61 and passes through the polarizing beam splitter 58. The reference light that has passed through the polarizing beam splitter 58 enters the optical element 59 for split optical rotation, and the light component incident on the right side portion thereof is emitted as a B polarization component by rotating the plane of polarization by + 45 ° and incident on the left side portion. The light component is output as an A-polarized component by rotating the plane of polarization by −45 °. These A-polarized component and B-polarized component enter the hologram recording medium 40 with a reflective layer through the objective lens 60, pass through the transparent substrate 41, the recording layer 43, and the gap layer 45, and are reflected on the transparent substrate 47. 46 is collected.

  As described above, the information light as the A-polarized component and the reference light as the B-polarized component are emitted from the right portion of the optical element 59 for two-part optical rotation. On the other hand, from the left part of the optical element 59 for two-part optical rotation, information light as a B-polarized component and reference light as an A-polarized component are emitted. These information light and reference light are collected on the reflective layer 46 of the hologram recording medium 40 with a reflective layer.

  Interference occurs between the information light incident on the recording layer 43 as direct light through the transparent substrate 41 and the reference light incident on the recording layer 43 as reflected light after being reflected by the reflective layer 46. Even between the reference light as the direct light and the information light as the reflected light, interference between the information light and the reference light occurs. Thus, a distribution of optical characteristics corresponding to the information light can be generated inside the recording layer 43. On the other hand, interference between information light as direct light and information light as reflected light, and interference between reference light as direct light and reference light as reflected light do not occur.

  Also in the reflection hologram recording / reproducing apparatus shown in FIG. 4, an ultraviolet light source device and an ultraviolet light irradiation optical system may be provided in order to improve the stability of the recorded hologram.

  Information recorded on the hologram recording medium with a reflective layer 40 can be read as follows.

  When the electromagnetic shutter 57 is closed, only the reference light that is a P-polarized component enters the optical element 59 for two-part optical rotation. The reference light is emitted by the two-part optical rotation optical element 59, and the light component incident on the right side of the reference light is output by rotating the polarization plane by + 45 ° as a B polarization component, and the light component incident on the left side is polarized on the plane of polarization. It is rotated 45 ° and emitted as an A-polarized component. Thereafter, the A-polarized component and the B-polarized component enter the hologram recording medium 40 with a reflective layer through the objective lens 60, pass through the transparent substrate 41, the recording layer 43, and the gap layer 45, and are provided on the transparent substrate 47. The light is condensed on the reflection layer 46 formed.

  In the recording layer 43 of the hologram recording medium 40 with a reflective layer, an optical characteristic distribution corresponding to information is formed. Therefore, part of the A-polarized component and the B-polarized component incident on the hologram recording medium 40 with the reflective layer is diffracted by an optical characteristic distribution refractive index modulation region (not shown) formed in the recording layer 43, and information light The hologram recording medium 40 with a reflective layer is emitted as reproduction light that reproduces the above.

  The reproduction light emitted from the hologram recording medium with a reflective layer 40 is converted into a parallel light beam by the objective lens 60 and then enters the optical element 59 for two-part optical rotation. The B-polarized component incident on the right portion of the two-part optical rotatory optical element 59 is emitted as a P-polarized component, and the A-polarized component incident on the left-hand portion of the two-part optical rotatory optical element 59 is emitted as a P-polarized component. In this way, reproduction light as a P-polarized component is obtained.

  Thereafter, the reproduction light passes through the polarization beam splitter 58. Part of the reproduction light transmitted through the polarization beam splitter 58 passes through the beam splitter 61 and forms an image on the two-dimensional photodetector 63 through the imaging lens 62 so as to reproduce the image of the transmissive spatial light modulator 55. Is done. The information recorded on the hologram recording medium 40 with a reflective layer can be read by the above method.

  On the other hand, the remainder of the A-polarized component and the B-polarized component that have been transmitted through the two-part optical rotatory optical element 59 and entered the hologram recording medium 40 with a reflective layer are reflected by the reflective layer 46 and emitted from the hologram recording medium 40 with a reflective layer. To do. The A-polarized component and the B-polarized component as the reflected light are converted into parallel light beams by the objective lens 60, and then the A-polarized component is incident on the right side portion of the optical element 59 for two-part optical rotation, and is emitted as the S-polarized component. The B-polarized component is incident on the left side of the two-part optical rotation optical element 59 and is emitted as an S-polarized component.

  The S-polarized component emitted from the two-part optical rotatory optical element 59 is reflected by the polarization beam splitter 61 and therefore does not reach the two-dimensional photodetector 63. Therefore, according to this recording / reproducing apparatus, an excellent reproduction SN ratio can be realized.

  If necessary, after all the recording is completed, the remaining monomer may be polymerized by irradiation with uniform light. Further, if necessary, after all the recording is completed, oxygen may penetrate into the recording layer of the hologram recording medium in an oxygen atmosphere to inactivate radical species in the hologram recording medium.

  FIG. 5 shows a schematic diagram of an optical recording / reproducing apparatus using the coaxial interference method. In the illustrated recording / reproducing apparatus, a coaxial interference technique is used in which information light and modulated reference light are generated using a single spatial light modulator, and a hologram is recorded.

  As the light source device 65, a linearly polarized laser is desirable from the viewpoint of coherence, as in the case of the transmission hologram recording / reproducing device and the reflection hologram recording / reproducing device described above. Specific examples include a semiconductor laser, a He—Ne laser, an argon laser, and a YAG laser. The light source device 65 has a function of adjusting the emission wavelength.

  The beam expander 66 can expand the outgoing light emitted from the light source device 65 and shape it into a parallel light flux. The shaped light is applied to the reflective spatial light modulator 68 via the mirror 67. The reflective spatial light modulator 68 has a plurality of pixels arranged two-dimensionally in a lattice shape, and the direction of the reflected light can be changed for each pixel. Alternatively, by changing the polarization direction of reflected light for each pixel, information light provided with information as a two-dimensional pattern and spatially modulated reference light are generated simultaneously. As the reflective spatial light modulator 68, for example, a digital mirror device, a reflective liquid crystal element, a reflective modulator using a magneto-optical effect, or the like can be used.

  In the illustrated example, a digital mirror device is used as the reflective spatial light modulator 68. The recording light reflected by the reflective spatial light modulator 68 is incident on the polarization beam splitter 71 via the imaging lenses 69 and 70. Here, the polarization direction is adjusted at the time of emission from the light source device 65 so that the recording light passes through the polarization beam splitter 71.

  The recording light that has passed through the polarization beam splitter 71 passes through the optical element 72 for optical rotation and is irradiated onto the hologram recording medium 40 with a reflective layer by the objective lens 73. The recording light is condensed on the surface of the reflection layer 46 of the hologram recording medium 40 with a reflection layer so that the beam diameter is minimized. As the optical rotatory optical element 72, for example, a quarter wavelength plate, a half wavelength plate, or the like can be used.

  When reproducing recorded information, when a part of the reference light spatially modulated by the reflective spatial light modulator 68 passes through the hologram recording medium 40 with a reflective layer, a refractive index modulation region (not shown) is shown. ) To be reproduced light. The reproduction light is reflected by the reflection layer 46 and then passes through the objective lens 73 and the optical element 72 for optical rotation. When passing through the optical rotatory optical element 72, this light includes a polarization component different from that of the reference light and is reflected by the polarization beam splitter 71.

  It is desirable that the rotation angle of the optical rotation optical element 72 is adjusted so that the reflectance of the reproduction light at the polarization beam splitter 71 is the highest. The reproduction light reflected by the polarization beam splitter 71 is imaged as a reproduction image on the two-dimensional photodetector 75 by the imaging lens 74. Note that an iris 76 may be disposed in front of the photodetector 75 in order to increase the S / N ratio of the reproduction signal.

  In the hologram recording medium according to the embodiment of the present invention, since the polymerization inhibitor is bonded to the polymer matrix in the recording layer through a covalent bond, the recording layer does not freely diffuse. Accordingly, the polymerization inhibitor concentration in the unrecorded area remains unchanged. The exposure schedule of the pre-exposure process at the time of additional writing may always be the same, and it has become a simple apparatus as a hologram recording medium recording apparatus using the hologram recording medium.

  Specific examples of the present invention are shown below.

Example 1
6.04 g of 1,6-hexanediol diglycidyl ether (Denacol Ex-212, Nagase ChemteX) as an epoxy compound, 1.62 g of tetraethylenepentamine as a curing agent, and 1.35 g of N as a radical polymerizable monomer -Vinylcarbazole was mixed and stirred to obtain a uniform solution.

  To this solution, 0.033 g of Irgacure 784 (Ciba Specialty Chemicals) was added as a radical photopolymerization initiator, and 0.09 g of 4-methacryloyl-2,2,6,6-tetramethylpiperidine-N-oxide was added as a polymerization inhibitor. And defoaming to obtain a recording layer precursor solution.

  Two glass plates were arranged via a spacer made of a sheet made of polytetrafluoroethylene (PTFE) to form a void. The above-mentioned recording layer raw material solution was poured into this gap. This was shielded from light and cured at room temperature for 24 hours, thereby producing a plurality of hologram recording medium test pieces having a recording layer having a thickness of 200 μm. Through the above steps, a transmission type hologram recording medium having the configuration as shown in FIG. 1 was obtained.

  In a dark room, the glass substrate was peeled from the obtained transmission hologram recording medium, and the recording layer was taken out and immersed in tetrahydrofuran to extract components dispersed in the recording layer. When the extract was observed by electron spin resonance, no radical spectrum was observed, and 4-methacryloyl 2,2,6,6-tetramethylpiperidine-N-oxide did not flow out into the tetrahydrofuran. confirmed. Further, it was confirmed by infrared spectroscopy that the absorption peak derived from methacryloyl disappeared. 4-Methacryloyl-2,2,6,6-tetramethylpiperidine-N-oxide is covalently bonded to the polymer matrix.

The obtained test piece was placed on the rotary stage 20 of the hologram recording apparatus shown in FIG. 3 to record a hologram. As the light source device 21, a semiconductor laser having a wavelength of 405 nm was used. Angle multiplex recording was performed at a plurality of positions on the test piece, and the hologram recording performance was evaluated by M / # (M number) representing the recording dynamic range. At that time, pre-exposure processing was performed immediately before each recording step with a uniform exposure amount. M / # is defined by the following equation using η _i . η _i is the diffraction efficiency from the i-th hologram when n-page holograms are angularly multiplexed and recorded until recording in the same area in the recording layer of the hologram recording medium becomes impossible. The angle multiplex recording / reproduction is performed by irradiating the transmission hologram recording medium 10 with predetermined light while driving the rotary stage 20.

As the diffraction efficiency eta, when irradiating only the reference beam Rf transmission type holographic optical recording medium 10, the light intensity detected light intensity detected by the photodetector 31 in I _t and the light detector 30 _Was defined using I _d . That is, the internal diffraction efficiency represented by η = I _d / (I _t + I _d ) was used.

In this way, a plurality of holograms were recorded on the test piece, and recording was performed until the recording area occupied 75% of the area on the test piece. The record here is a record before the acceleration test. Recorded No. Table 1 below summarizes the M / # for each of the holograms 1-35.

  As shown in Table 1 above, before the acceleration test, the average value of M / # is 7.1, and the difference (variation) between the maximum value and the minimum value of M / # is 0.7.

  If the variation is about 10% or less of the average value, the M / # variation can be ignored and can be regarded as substantially constant. In the recording process before the acceleration test, the M / # of the angle-multiplexed hologram has almost no variation. Moreover, it can be said that there is no difference between the initial stage (No. 1) and the late stage (No. 35) of the recording process. In the test piece of the example, it is presumed that the polymerization inhibitor did not diffuse in the recording layer from the initial stage to the late stage of the recording process even when a plurality of holograms were angularly multiplexed.

The test piece for which recording was completed was stored in an oven at 60 ° C. for one week under light shielding for an accelerated test. The test piece after the acceleration test was subjected to angle multiplex recording at a plurality of positions in the unrecorded area by the same method as described above. As before, a pre-exposure process was performed with a uniform exposure immediately before each recording step. After recording, while rotating the rotary stage 20, the hologram recorded on the test piece was irradiated with reference light to determine the light intensity. The dynamic range of recording was evaluated using M / # in the same manner as described above. In addition, the exposure amount of the pre-exposure process is the same before and after the acceleration test for one week. Recorded No. Table 2 below summarizes the M / # for each of the 1 ′ to 10 ′ holograms.

  As shown in Table 2 above, the average value of M / # after the acceleration test is 6.9, and the difference between the maximum value and the minimum value of M / # is 0.5. Compared to before the acceleration test, the average value of M / # is reduced by about 3% after the acceleration test. If the change is within 5%, it can be determined that M / # does not substantially change. That is, it is shown that there is almost no change even after a one-week accelerated test. From this, it is presumed that the concentration of the polymerization inhibitor was unchanged in each recording region in the test piece of this example even before and after the 60 ° C. acceleration test.

(Comparative Example 1)
6.04 g of 1,6-hexanediol diglycidyl ether (Denacol Ex-212, Nagase ChemteX) as an epoxy compound, 1.62 g of tetraethylenepentamine as a curing agent, and 1.35 g of N as a radical polymerizable monomer -Vinylcarbazole was mixed and stirred to obtain a uniform solution.

  To this solution, 0.033 g of Irgacure 784 (Ciba Specialty Chemicals) as a photo radical polymerization initiator and 0.09 g of 2,2,6,6-tetramethylpiperidine-N-oxide as a polymerization inhibitor were added and defoamed. Thus, a recording layer precursor solution was obtained.

  Two glass plates were arranged via a spacer made of a sheet made of polytetrafluoroethylene (PTFE) to form a void. The above-mentioned recording layer raw material solution was poured into this gap. This was shielded from light and cured at room temperature for 24 hours, thereby producing a plurality of hologram recording medium test pieces having a recording layer having a thickness of 200 μm. Through the above steps, a transmission type hologram recording medium having the configuration as shown in FIG. 1 was obtained.

  In a dark room, the glass substrate was peeled from the obtained transmission hologram recording medium, and the recording layer was taken out and immersed in tetrahydrofuran to extract components dispersed in the recording layer. When the extract was observed by electron spin resonance, a spectrum derived from 2,2,6,6-tetramethylpiperidine-N-oxide was observed. Further, it was confirmed that 2,2,6,6-tetramethylpiperidine-N-oxide as a polymerization inhibitor was dispersed in the polymer matrix without bonding.

  The obtained test piece was placed on the rotary stage 20 of the hologram recording apparatus shown in FIG. 3, and a plurality of holograms were angle-multiplexed recorded in the same manner as in (Example 1). As the light source device 21, a semiconductor laser having a wavelength of 405 nm was used. Angle multiplex recording was performed at a plurality of positions on the test piece to evaluate the recording performance of the M / # hologram. At that time, a pre-exposure process was performed immediately before each recording step with a uniform exposure amount. Angle multiplex recording / reproduction is performed by irradiating the hologram recorded on the test piece while driving the rotary stage 20.

In this way, a plurality of holograms were recorded on the test piece, and recording was performed until the recording area occupied 75% of the area on the test piece. The record here is a record before the acceleration test. Recorded No. Table 3 below summarizes the M / # for each of the holograms 1-35.

  As shown in Table 3 above, before the acceleration test, the average value of M / # is 6.6, and the difference (variation) between the maximum value and the minimum value of M / # is 1.6.

  If the M / # variation exceeds 10% of the average value, it can be said that the performance of the medium is position-dependent, and it is difficult to perform stable recording on such a medium. Further, a significant difference is observed between the initial stage (No. 1) and the late stage (No. 35) of the recording process. In the test piece of the comparative example, it is presumed that the polymerization inhibitor diffused in the recording layer from the initial stage to the late stage of the recording process when a plurality of holograms were angle-multiplexed recorded.

  Since the concentration of the polymerization inhibitor in the recording area has decreased, when the uniform pre-exposure processing is performed, the concentration of the polymerization inhibitor in the unrecorded area is lower than the initial concentration, and the uniform pre-exposure processing is performed on this area. As a result, more radicals were generated than the polymerization inhibitor in the region. It is presumed that radicals generated by the polymerization inhibitor could not be trapped, and the remaining radicals were successively polymerized with surrounding monomers. By this reaction, it is considered that the monomer was consumed and M / # was lowered.

The test piece for which recording was completed was stored in an oven at 60 ° C. for one week under light shielding for an accelerated test. The test piece after the acceleration test was subjected to angle multiplex recording at a plurality of positions in the unrecorded area by the same method as described above. As before, a pre-exposure process was performed with a uniform exposure immediately before each recording step. After recording, while rotating the rotary stage 20, the hologram recorded on the test piece was irradiated with reference light to determine the light intensity. The dynamic range of recording was evaluated using M / # in the same manner as described above. Note that the exposure amount in the pre-exposure process is the same before and after the one week accelerated test. Recorded No. Table 4 below summarizes the M / # for each of the 1 ′ to 10 ′ holograms.

  As shown in Table 4 above, the average value of M / # after the acceleration test is 4.0, and the difference between the maximum value and the minimum value of M / # is .1.6. Compared to before the acceleration test, the M / # decreases by about 40% after the acceleration test. The decrease in M / # means that the potential for multiplex recording in that area has decreased.

  This is because the polymerization inhibitor diffused from the unrecorded area to the recorded area during the 60 ° C. accelerated test. In the unrecorded area, the concentration of the polymerization inhibitor is lower than the initial concentration. Since a uniform pre-exposure treatment was performed on such a region, more radicals were generated than the polymerization inhibitor in that region.

  The generated radicals cannot be completely trapped by the polymerization inhibitor, and the remaining radicals are presumed to have successively polymerized with the surrounding monomers. As a result, it is considered that the monomer was consumed and M / # was lowered.

1 is a schematic sectional view of a hologram recording medium according to an embodiment of the present invention. The schematic sectional drawing of the hologram recording medium concerning other embodiment of this invention. 1 is a schematic diagram of a hologram information recording / reproducing apparatus according to an embodiment of the present invention. Schematic of the hologram information recording / reproducing apparatus concerning other embodiment of this invention. Schematic of the hologram information recording / reproducing apparatus concerning other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Hologram recording medium; 11 ... Transparent substrate; 13 ... Recording layer 15 ... Transparent substrate; 40 ... Hologram recording medium with a reflective layer; 41 ... Transparent substrate 43 ... Recording layer; 45 ... Gap layer; Transparent substrate 21 ... Light source device; 22 ... Beam expander; 23 ... Optical element for optical rotation 24 ... Polarizing beam splitter; 25 ... Optical element for optical rotation; 26 ... Mirror 27 ... Mirror; 28 ... Electromagnetic shutter; 31 ... Photodetector; 32 ... Ultraviolet light source device; 51 ... Light source device 52 ... Beam expander; 53 ... Optical element for optical rotation 54 ... Polarizing beam splitter; 55 ... Transmission type spatial light modulator 56 ... Polarizing beam splitter; 57 ... Electromagnetic shutter 58 ... Polarizing beam splitter; 59 ... Optical element for two-part optical rotation; 60 ... Pair Object lens 61 ... Beam splitter; 62 ... Imaging lens; 63 ... Two-dimensional photodetector 65 ... Light source device; 66 ... Beam expander; 67 ... Mirror 68 ... Reflective spatial light modulator; 69 ... Imaging lens; Imaging lens 71 ... Polarizing beam splitter; 72 ... Optical element for optical rotation; 73 ... Objective lens 74 ... Imaging lens; 75 ... Two-dimensional photodetector; 76 ... Iris.

Claims (2)

Comprising a recording layer containing a radical polymerizable monomer having an ethylenically unsaturated bond, a photo radical polymerization initiator, a polymer matrix, and a polymerization inhibitor;
The hologram recording medium, wherein the polymerization inhibitor is selected from the group consisting of a phenol derivative, a hindered amine, and a nitroxide compound, and is bonded to the polymer matrix through a covalent bond.   The hologram recording medium according to claim 1, wherein the polymerization inhibitor is contained in an amount of 0.0001 part to 1 part with respect to the radical photopolymerization initiator.

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