WO2011024297A1 - Method for producing hologram recording medium - Google Patents

Abstract

Disclosed is a method for producing a hologram recording medium (10), which is characterized by comprising: a step wherein a photosensitive material precursor (18) in the form of a liquid or a gel is brought into contact with the surfaces of thermosoftening layers (15, 17) by using substrates (11, 12) which comprise bases (14, 16) and the thermosoftening layers (15, 17) formed on the bases (14, 16) and having lower midpoint glass transition temperatures than the materials forming the bases (14, 16); a step wherein a recording layer (13) is formed by curing the photosensitive material precursor (18); and a step wherein the thermosoftening layers (15, 17) are heated at a temperature higher than the extrapolated glass transition initiation temperatures of the thermosoftening layers (15, 17) but lower than the midpoint glass transition temperatures of the bases (14, 16) during or after the formation of the recording layer (13).

Description

Method for manufacturing hologram recording medium

The present invention relates to a method for manufacturing a hologram recording medium.

Hologram recording media that record information in holograms are attracting attention as next-generation optical information recording media because they can record large volumes. The hologram recording medium is generally composed of information light that carries information by spatially modulating laser light by a spatial light modulator such as a liquid crystal element or a digital micromirror device, and information light having the same wavelength as the information light. Information is recorded by recording interference fringes formed by irradiating the same place with reference light generated from the same light source in a recording medium. Since the interference fringes have a three-dimensional spread, the recording layer for recording the interference fringes is not only the surface direction but also three-dimensional volume recording including the thickness direction.

The thickness of the recording layer greatly affects the recording density of the hologram recording medium. In general, in a range where the transmission intensity of information light and reference light necessary for hologram recording is not adversely affected, the peak width that meets the Bragg condition of interference fringes decreases as the thickness of the hologram recording medium increases. Therefore, the so-called multiple recording performance of recording a plurality of interference fringes in the same place is improved. This means that the recording density of the hologram recording medium is increased.

Recently, a material of the recording layer that has attracted particular attention is a material called a photopolymer mixed with a matrix material, a radical polymerizable monomer, a photo radical polymerization initiator, etc., and a liquid or gel photo polymer is cured by a chemical reaction. Thus, there is a technique for producing a recording layer. During this curing, it is known that a phenomenon called “curing shrinkage” occurs in which the recording layer shrinks at a constant rate. As the thickness of the recording layer increases, the volume that shrinks increases, so when producing a recording layer while maintaining a constant thickness with a spacer, etc., the recording layer will be distorted unless measures are taken against this curing shrinkage. There is a risk that normal recording and reproduction of information cannot be performed.

As a method for producing a hologram recording medium using a photopolymer, for example, two substrates are arranged so as to face each other, a liquid raw material to be a recording layer is injected therebetween, and then a liquid raw material is formed by a chemical reaction. A manufacturing method for obtaining a recording layer by curing is disclosed (for example, see Patent Document 1).

However, in such a manufacturing method, since curing shrinkage occurs as a result of a chemical reaction, even within the same recording layer, uniform curing shrinkage does not occur in the inside and the surface layer portion, and local shrinkage that occurs when the liquid raw material is cured. It is difficult to completely remove the difference in general contraction. If the difference in cure shrinkage in the recording layer is not removed, stress will remain between the substrate and the cured recording layer, causing a failure of peeling of the substrate and the recording layer when storing the recording medium for a long time. Therefore, there is a problem that normal recording and reproduction are difficult.

Further, as a method for producing a hologram recording medium, a method is disclosed in which a recording layer is formed by liquid injection molding, and then the recording layer and a substrate are bonded together with an adhesive or the like and laminated (for example, Patent Document 2).

However, in the case of such a manufacturing method, a release agent is used in order to improve the peeling between the recording layer and the mold during liquid injection molding. However, this release agent is mixed in the recording layer, and this release agent is used. May cause light scattering. Light scattering significantly degrades the SNR (Signal-Noise Rate) representing the quality of recording and reproduction, and may also cause a reduction in recording capacity, so it needs to be reduced.

JP 2005-17589 A JP 2008-65912 A

As described above, since the amount of cure shrinkage increases as the recording layer thickness increases, distortion due to cure shrinkage of the recording layer is necessary in the production of hologram recording media that require a thick information recording layer to achieve a high recording density. It is essential to reduce. It is also essential to reduce light scattering. However, the presently proposed method for manufacturing a hologram recording medium cannot be said to be sufficiently effective.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a method for producing a hologram recording medium having excellent optical characteristics by reducing distortion and light scattering.

According to one aspect of the present invention, using a substrate comprising a base material and a thermal softening layer formed on the base material and having a midpoint glass transition temperature lower than that of the base material, A step of bringing a liquid or gel photosensitive material precursor into contact with a surface; a step of curing the photosensitive material precursor to form a recording layer; and the thermal softening during or after the formation of the recording layer Heating the thermosoftening layer at a temperature higher than the extrapolation glass transition start temperature of the layer and lower than the midpoint glass transition temperature of the substrate, and a method for producing a hologram recording medium is provided. Is done.

According to the method for manufacturing a hologram recording medium according to one aspect of the present invention, distortion and light scattering can be reduced, so that a hologram recording medium having excellent optical characteristics can be provided.

It is a schematic longitudinal cross-sectional view of the hologram recording medium which concerns on 1st Embodiment. It is the schematic diagram which showed the manufacturing process of the hologram recording medium which concerns on 1st Embodiment. It is the schematic diagram which showed the manufacturing process of the hologram recording medium which concerns on 1st Embodiment. It is the schematic diagram which showed the manufacturing process of the hologram recording medium which concerns on 1st Embodiment. It is a figure showing how to obtain the midpoint glass transition temperature (T _mg ), the extrapolation glass transition start temperature (T _ig ), and the extrapolation glass transition end temperature (T _eg ). It is a schematic longitudinal cross-sectional view of the hologram recording medium which concerns on 1st Embodiment. It is the schematic diagram which showed the manufacturing process of the hologram recording medium which concerns on 2nd Embodiment. It is the schematic diagram which showed the manufacturing process of the hologram recording medium which concerns on 2nd Embodiment.

(First embodiment)
The first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of a hologram recording medium according to the present embodiment, and FIGS. 2A to 4B are schematic views showing manufacturing steps of the hologram medium according to the present embodiment. FIG. 5 is a diagram showing how to obtain the intermediate-point glass transition temperature (T _mg ), the extrapolation glass transition start temperature (T _ig ), and the extrapolation glass transition end temperature (T _eg ).

First, the structure of the hologram recording medium manufactured by the manufacturing method of the present embodiment will be described. A holographic recording medium 10 shown in FIG. 1 is a transmissive type, and includes a first substrate 11, a second substrate 12, and a recording layer 13. When viewed from the recording light incident side, the first substrate 11 and the like are arranged in the order of the first substrate 11, the recording layer 13, and the second substrate 12. That is, the recording layer 13 is sandwiched between the first substrate 11 and the second substrate 12. The first substrate 11 includes a transparent base material 14 and a heat softening layer 15, and the second substrate 12 includes a transparent base material 16 and a heat softening layer 17. The recording layer 13 is in contact with the heat softening layers 15 and 17.

The base materials 14 and 16 are part of members constituting the hologram recording medium 10 and play a role of physically and chemically protecting the recording layer 13 from the outside. The thermal softening layers 15 and 17 are for relaxing the stress caused by the curing shrinkage of the recording layer 13. The recording layer 13 is for recording information and has photosensitivity.

The light transmittance of the recording layer 13 and the thermal softening layers 15 and 17 is preferably 10% or more with respect to the recording light having a wavelength of 390 nm to 650 nm, more preferably 390 nm to 420 nm. If this light transmittance is 10% or more, necessary sensitivity and diffraction efficiency can be obtained.

Such a hologram recording medium 10 can be manufactured by the following method. First, the first substrate 11 and the second substrate 12 are prepared. Specifically, as shown in FIG. 2A, the thermal softening layer 15 is formed on the base material 14 to form the first substrate 11. Similarly, as shown in FIG. 2B, the heat softening layer 17 is formed on the base material 16 to form the second substrate 12.

As the substrates 14 and 16, plastics such as glass and polycarbonate can be used, and in some cases, a layer having an action such as an oxygen permeation preventing layer may be provided to have a multilayer structure.

Heat-softening layer 15, than the base material 14 and the intermediate glass transition temperature (T _mg) is composed of a material having low thermal softening layer 17, the intermediate glass transition temperature (T _mg) than base 16 Consists of low materials. This is based on the following reason. Since the deformation of the base materials 14 and 16 by heating leads to a significant change in the thickness of the hologram recording medium 10, the heating temperature for heating the thermosoftening layers 15 and 17 is at least the midpoint glass of the base materials 14 and 16. It must be lower than the transition temperature. For this reason, the heat softening layer 15 needs to be a material that softens at a temperature lower than the midpoint glass transition temperature of the base material 14. Since the same can be said for the heat softening layer 17, the heat softening layer 17 needs to be a material that softens at a temperature lower than the midpoint glass transition temperature of the substrate 16.

Here, since the glass transition temperature of polymers such as plastics generally extends to a certain temperature range, the JIS standard JISK7121 (method for measuring the transition temperature of plastics) uses “the midpoint glass transition temperature (T _mg ) as the glass transition temperature. ) ”,“ Extrapolated glass transition start temperature (T _ig ) ”, and“ extrapolated glass transition end temperature (T _eg ) ”.

As shown in FIG. 5, “midpoint glass transition temperature (T _mg )” is a curve drawn by differential thermal analysis (DTA) or differential scanning calorimetry (DSC). It means the temperature at the point where the straight line equidistant in the vertical axis direction from the straight line extended from each line and the curve of the step-like change part of the glass transition intersect. In FIG. 5, the height from the straight line obtained by extending the high temperature side baseline to the low temperature side baseline is represented by h.

As shown in FIG. 5, “extrapolated glass transition start temperature (T _ig )” is a curve drawn by differential thermal analysis (DTA) or differential scanning calorimetry (DSC). And the temperature at the intersection of the tangent drawn at the point where the gradient of the curve of the step-like change portion of the glass transition is maximized.

As shown in FIG. 5, “extrapolated glass transition onset temperature (T _eg )” is a curve drawn by differential thermal analysis (DTA) or differential scanning calorimetry (DSC). And the temperature at the intersection of the tangent drawn at the point where the gradient of the curve of the step-like change portion of the glass transition is maximized.

Further, when the thickness of the hologram recording medium 10 is not constant, the hologram recording medium 10 is tilted at the time of recording / reproducing of the hologram recording medium 10, so that the hologram recording medium is also used to reduce the tilt amount as much as possible. The thickness of 10 needs to be constant. Therefore, the heat softening layers 15 and 17 need to have a certain degree of hardness in the recording / reproducing temperature range (for example, 10 to 80 ° C.) defined by the standard of the hologram recording medium 10. Here, there are various indices such as hardness, penetration, Young's modulus, and rigidity, but the heat softening layers 15 and 17 have a hardness of 100 Pa · s or more in terms of Young's modulus. Is desirable. If another index is used, it is desirable that the rubber hardness of the heat softening layers 15 and 17 at the time of heating is 10 degrees or more lower than the rubber hardness of the heat softening layers 15 and 17 at the room temperature. “Room temperature” generally means 25 ° C.

The material of the heat softening layers 15 and 17 is not particularly limited as long as it has a lower midpoint glass transition temperature than the material of the base materials 14 and 16, but for example, a polymer resin can be used. Specifically, for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, Teflon, ABS resin, AS resin, acrylic resin, and derivatives and composites thereof can be used. Depending on the relationship between the base materials 14 and 16 and the glass transition temperature of the recording layer 13, engineering plastics (for example, polyamides, polyacetals, polycarbonates, modified polyphenylenes) in which the glass transition temperature is controlled by molecular weight distribution control or additives. Ether, polybutylene terephthalate, polyethylene terephthalate, cyclic polyolefin) and the like can also be used.

The formation method of the heat softening layers 15 and 17 is not particularly limited. For example, the heat softening layers 15 and 17 may be formed on the base materials 14 and 16, or a film-like material may be attached to the base materials 14 and 16 to form the heat softening layers 15 and 17. May be. When the heat softening layers 15 and 17 are formed by coating using a coating device such as a spin coater, bar coater, or film applicator, the film thickness uniformity and surface flatness of the heat softening layers 15 and 17 are determined. Can keep. After the application, curing is performed by a method suitable for the material of the heat softening layers 15 and 17 such as natural curing, heat curing, and curing by UV irradiation. Further, before forming the heat softening layers 15 and 17, the coated surfaces of the base materials 14 and 16 may be subjected to corona discharge treatment, plasma treatment, ozone treatment, alkali treatment or the like to improve the adhesion.

After the first substrate 11 and the second substrate 12 are prepared, a liquid or gel photosensitive material precursor is formed on the surface of the thermal softening layer 17 of the second substrate 12 as shown in FIG. 18 is applied to bring the photosensitive material precursor 18 into contact with the heat softening layer 17. Here, “liquid” means a state in which the photosensitive material precursor flows out at least when the photosensitive material precursor is applied to the thermal softening layer, and “gel” means at least the photosensitive material. When the precursor is applied to the heat softening layer, it means a state in which the flow of the photosensitive material precursor hardly occurs.

Examples of the method for applying the photosensitive material precursor 18 include casting and spin coating. The first substrate 11 and the second substrate 12 are arranged with a predetermined gap through a spacer so that the heat softening layers 15 and 17 are inside, and the photosensitive material precursor 18 is placed in the gap. May be injected.

The photosensitive material precursor 18 is mainly composed of a matrix material, a radical polymerizable monomer, a photo radical polymerization initiator, and the like.

Matrix material Examples of the matrix material include three-dimensional crosslinkable materials. The three-dimensional crosslinkable material is three-dimensionally crosslinked by a polymerization reaction and cured. Examples of the polymerization reaction of the three-dimensional crosslinkable material include cation polymerization of epoxy, cation polymerization of vinyl ether, epoxy-amine polymerization, epoxy-acid anhydride polymerization, and epoxy-mercaptan polymerization. The matrix material is exemplified below, but the present invention is not limited to this.

Epoxy compounds include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,8-octanediol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl Ether, neopentyl glycol diglycidyl ether, diepoxy octane, resorcinol diglycidyl ether, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxy Rate, and epoxypropoxypropyl-terminated polydimethylsiloxane. These may be used alone or in combination of two or more.

Examples of epoxy compound curing agents include amines, phenols, organic acid anhydrides, and amides. Specifically, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, mensendiamine, isophoronediamine, bis (4-amino-3-methyldicyclohexyl) methane, bis (amino Methyl) 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, p-phenylenediamine, diaminodi Phenylmethane, diaminodiphenylsulfone, 3,3′-diethyl-4,4′-diaminodiphenylmethane, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, Methyl hexahydrophthalic acid, methylcyclohexene tetracarboxylic anhydride, phthalic anhydride, trimellitic anhydride, benzophenone tetracarboxylic anhydride, dodecenyl succinic anhydride, ethylene glycol bis (anhydrotrimellitate), phenol novolac resin, Examples include cresol novolac resin, polyvinyl phenol, terpene phenol resin, and polyamide resin.

If necessary, a curing catalyst may be added to the epoxy compound and the curing agent. Examples of the curing catalyst include basic catalysts such as 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, benzyldimethyl Amine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) or a phenol salt thereof, Trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole 2-phenyl-4-methylimidazole, and 2-hepta imidazole. Latent catalysts such as boron trifluoride amine complex, dicyandiamide, organic acid hydrazide, diaminomaleonitrile and its derivatives, melamine and its derivatives, amine imide and the like may be used. Curing can be accelerated by adding a compound having active hydrogen, such as phenols or salicylic acid.

Radical polymerizable monomer A radical polymerizable monomer is a compound having at least one ethylenically unsaturated bond capable of radical polymerization, such as unsaturated carboxylic acid, unsaturated carboxylic acid ester, unsaturated carboxylic acid amide, and vinyl compound. Can be mentioned. 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, acryloyl morpholine, 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, triallyl trimellitate.

The blending amount of the radical polymerizable monomer is preferably 1 to 50% by weight of the photosensitive material precursor 18, and more preferably 3 to 30% by weight. If the monomer is 1% by weight or more, a sufficient refractive index change can be obtained. When the radical polymerizable monomer is 50% by weight or less, the volumetric shrinkage is small and good resolution can be obtained.

Photoradical polymerization initiator The photoradical polymerization initiator is selected according to the wavelength of the recording light. Examples of radical photopolymerization initiators 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 manufactured by Ciba Specialty Chemicals, 907, 1700, 1800, 1850 and the like, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxyphthalate, t-butyl Peroxybenzoate, acetyl peroxide, isobutyryl peroxide Decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, t- butyl hydroperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide, and cyclohexanone peroxide. When the recording light is blue laser light, the radical polymerization initiator is preferably a titanocene compound such as Irgacure 784 (manufactured by Ciba Specialty Chemicals).

The blending amount of the photo radical polymerization initiator is preferably 0.1 to 20% by weight of the photosensitive material precursor 18, and more preferably 0.2 to 10% by weight. If the radical photopolymerization initiator is 0.1% by weight or more, a sufficient refractive index change can be obtained. When the radical photopolymerization initiator is 20% by weight or less, light absorption is small and good sensitivity and diffraction efficiency can be obtained.

In addition, sensitizing dyes such as cyanine, merocyanine, xanthene, coumarin, and eosin, silane coupling agents, and plasticizers may be added to the photosensitive material precursor 18 as necessary.

After the photosensitive material precursor 18 is brought into contact with the surface of the thermal softening layer 17, the photosensitive material precursor is brought into contact with the photosensitive material precursor 18 as shown in FIG. First substrate 11 is stacked on 18.

Next, as shown in FIG. 3B, in this state, the photosensitive material precursor 18 is cured by three-dimensionally crosslinking the matrix material to form the recording layer 13.

The thickness of the recording layer 13 is preferably 20 μm to 2 mm, more preferably 50 μm to 1.5 mm. If the thickness of the recording layer 13 is 20 μm or more, a sufficient storage capacity can be obtained, and differentiation from conventional optical recording media such as CD and DVD can be achieved. Moreover, if the thickness of the recording layer 13 is 2 mm or less, there is no possibility that the resolution will be lowered.

After forming the recording layer 13, the heat softening layers 15, 17 are formed at a temperature higher than the extrapolation glass transition start temperature (T _ig ) of the heat softening layers 15, 17 and lower than the midpoint glass transition temperature of the base materials 14, 16. Heat. This heating is desirably performed from the outside of the first substrate 11 and the second substrate 12.

The heat softening layers 15 and 17 are heated to soften the heat softening layers 15 and 17 as shown in FIG. 3C, and the recording layer 13 is cured and contracted between the base materials 14 and 16 and the recording layer 13. The generated stress can be relaxed. In the present embodiment, the thermal softening layers 15 and 17 are heated after the recording layer 13 is formed. However, the thermal softening layers 15 and 17 are heated during the formation of the recording layer 13, that is, during curing. Also good.

Subsequently, a shortage inspection for measuring the thickness (film thickness) of the hologram recording medium 10 including the first substrate 11, the second substrate 12, and the recording layer 13 is performed. In this inspection, if the thickness of the hologram recording medium 10 does not satisfy the acceptance criteria and correction can be performed by heating the heat softening layers 15 and 17 again, the heat softening layers 15 and 17 are again used. And the thickness of the hologram recording medium 10 is adjusted. Specifically, when the thickness of the hologram recording medium 1 is thick, the heat softening layers 15 and 17 are heated again, and the thickness of the hologram recording medium 10 is reduced as shown in FIG. A pressure is applied to the hologram recording medium 10 to compress the hologram recording medium 10 in the thickness direction. When the hologram recording medium 10 is thin, the heat softening layers 15 and 17 are heated again, and the hologram recording medium 10 is thickened as shown in FIG. 4B. A pressure is applied to 10 and the hologram recording medium 10 is stretched in the thickness direction. In this embodiment, the thickness of the hologram recording medium 10 is adjusted after the stress of the recording layer 13 is relaxed. However, during the stress relaxation of the recording layer 13, that is, during the heating of the thermal softening layers 15 and 17. The thickness of the hologram recording medium 10 may be adjusted.

According to the present embodiment, since the heat softening layers 15 and 17 are provided between the base materials 14 and 16 and the recording layer 13, the heat softening layers 15 and 17 are heated after the recording layer 13 is formed. Thus, the stress generated when the heat softening layers 15 and 17 are softened and the recording layer 13 is cured and shrunk can be relaxed. Thereby, the distortion by hardening shrinkage can be reduced. Moreover, since no release agent is used, light scattering by the interface can be reduced without mixing light scattering sources. Therefore, the hologram recording medium 10 having excellent optical characteristics can be obtained.

Further, as described above, when the thickness of the hologram recording medium 10 does not satisfy the acceptance criteria, the heat softening layers 15 and 17 are heated again to adjust the thickness of the hologram recording medium 10, so that the conventional allowable range is reached. The out-of-stock items that have been outside can be made within the allowable range. As a result, the number of missing items of the hologram recording medium 10 can be reduced, and the yield can be improved.

Further, since the thickness of the hologram recording medium 10 is adjusted after the stress of the recording layer 13 is relaxed, the stress of the recording layer 13 can be further relaxed.

Furthermore, since the photosensitive material precursor 18 is brought into contact with the heat softening layers 15 and 17 from the state before curing, the adhesion between the recording layer 13 and the heat softening layers 15 and 17 can be improved.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example of a reflection hologram recording medium will be described. Note that the description overlapping with the first embodiment is omitted unless otherwise specified. FIG. 6 is a schematic longitudinal cross-sectional view of the hologram recording medium according to the present embodiment, and FIGS. 7A to 8C are schematic views showing the manufacturing steps of the hologram recording medium according to the present embodiment. FIG.

First, the structure of the hologram recording medium manufactured by the manufacturing method of the present embodiment will be described. A hologram recording medium 20 shown in FIG. 6 is of a reflective type, and includes a first substrate 21, a second substrate 22, and a recording layer 23. When viewed from the recording light incident side, the first substrate 21 and the like are arranged in the order of the first substrate 21, the recording layer 23, and the second substrate 22. That is, the recording layer 23 is sandwiched between the first substrate 21 and the second substrate 22. The first substrate 21 includes a transparent base material 24 and a thermal softening layer 25. The second substrate 22 includes a transparent base material 26, a reflective layer 27, a gap layer 28, and a thermal softening layer 29. In addition, the base material 26 does not necessarily need to be transparent. The recording layer 23 is in contact with the heat softening layers 25 and 29.

Such a hologram recording medium 20 can be manufactured by the following method. First, the first substrate 21 and the second substrate 22 are prepared. Specifically, as shown in FIG. 7A, the thermal softening layer 25 is formed on the base material 24 to form the first substrate 22. Similarly, as shown in FIG. 7B, a reflective layer 27, a gap layer 28, and a thermal softening layer 29 are formed in this order on the base material 26 to form the second substrate 22. To do. The materials and the like of the base materials 24 and 26 and the heat softening layers 25 and 29 are the same as those of the base materials 14 and 16 and the heat softening layers 15 and 17 in the first embodiment. That is, the heat softening layers 25 and 29 are made of a material having a lower midpoint glass transition temperature (T _mg ) than the base materials 24 and 26.

After the first substrate 21 and the second substrate 22 are prepared, a liquid or gel photosensitive material precursor is formed on the surface of the thermal softening layer 29 of the second substrate 22 as shown in FIG. 30 is applied to bring the photosensitive material precursor 30 into contact with the heat softening layer 29. In addition, since the component of the photosensitive material precursor 30 is the same as the component of the photosensitive material precursor 18, detailed description is abbreviate | omitted.

After bringing the photosensitive material precursor 30 into contact with the surface of the thermal softening layer 29, the first substrate 21 is brought into contact with the photosensitive material precursor 30 so that the thermal softening layer 25 comes into contact with the photosensitive material precursor 30 as shown in FIG. Repeat.

Next, as shown in FIG. 8B, in this state, the photosensitive material precursor 30 is cured by crosslinking the matrix material to form the recording layer 23.

After the recording layer 23 is formed, as shown in FIG. 8C, the glass transition temperature is higher than the extrapolated glass transition start temperature (T _ig ) of the heat softening layers 25 and 29 and the intermediate point glass transition temperature of the substrates 24 and 26. Heat softening layers 25 and 29 are heated at a lower temperature.

Finally, as in the first embodiment, a missing part inspection for measuring the thickness (film thickness) of the hologram recording medium 20 is performed, and the heat softening layers 25 and 29 are heated again according to the inspection result. Then, the thickness of the hologram recording medium 20 is adjusted.

Also in the present embodiment, since the heat softening layers 25 and 29 are provided between the base materials 24 and 26 and the recording layer 23, the same effect as in the first embodiment can be obtained.

Hereinafter, examples will be described. In this example, a hologram recording medium provided with a heat softening layer was produced, and the appearance of the hologram recording medium was observed. In addition, for comparison with the present example, a hologram recording medium without a heat softening layer was prepared, and appearance observation was performed in the same manner as the hologram recording medium of the example. In addition, this invention is not limited to each material specified below.

Sample (Example)
First, a solution of a photosensitive material precursor was prepared. This solution consists of 2.28 g of 1,6-hexanediol diglycidyl ether (Denacol Ex-212, manufactured by Nagase ChemteX Corporation) as an epoxy compound, 0.61 g of tetraethylenepentamine as a curing agent, and radical polymerization It was obtained by adding 0.15 g of 2-vinylnaphthalene as a monomer and 0.014 g of Irgacure 784 (manufactured by Ciba Specialty Chemicals) as a photo radical polymerization initiator and defoaming.

On the other hand, two unmodified glass substrates having a thickness of 1.0 mm or more as a substrate were prepared, and an optical adhesive film (PD-S1, manufactured by Panac Co., Ltd.) as a heat softening layer was formed on the surface of each substrate. ) Was affixed to prevent air bubbles from entering.

Then, the base material was placed so that the optical adhesive film faced, and a spacer of a polytetrafluoroethylene (PTFE) sheet was sandwiched, and a solution of the photosensitive material precursor was injected between the base materials.

Thereafter, the photosensitive material precursor solution injected between the substrates was shielded from light and allowed to stand at room temperature for 1 day, and the photosensitive material precursor solution was cured to form a recording layer. Thereafter, the outside of the base material was sandwiched with a heater heated to 80 ° C. for 10 seconds and subjected to a heat treatment to soften the optical adhesive film. Thereafter, a recording medium having a recording layer between the substrates was shielded from light and allowed to stand at room temperature for 3 days to produce a hologram recording medium having a recording layer having a thickness of 1000 μm.

(Comparative example)
In the same manner as in the above example, a solution of the photosensitive material precursor was injected between two unmodified glass substrates with a polytetrafluoroethylene (PTFE) sheet spacer interposed therebetween. In addition, in the comparative example, the optical adhesive film was not affixed on the base material. The photosensitive material precursor solution was the same as the photosensitive material precursor solution used in the examples.

Thereafter, in the same manner as in the Examples, the one in which the photosensitive material precursor solution was injected between the substrates was shielded from light and allowed to stand at room temperature for 1 day to cure the photosensitive material precursor solution. Formed. Thereafter, the outside of the substrate was sandwiched with a heater heated to 80 ° C. for 10 seconds, and heat treatment was performed. Thereafter, a recording medium having a recording layer between the substrates was shielded from light and allowed to stand at room temperature for 3 days to produce a hologram recording medium having a recording layer having a thickness of 1000 μm.

Appearance observation The appearances of the hologram recording media of Examples and Comparative Examples thus obtained were observed. In the comparative hologram recording medium, the recording layer was peeled from the vicinity of the spacer. On the other hand, peeling of the hologram recording medium of the example was not confirmed. From this result, it was confirmed that peeling of the recording layer can be suppressed when a hologram recording medium is produced by providing a heat softening layer.

DESCRIPTION OF SYMBOLS 10, 20 ... Hologram recording medium, 11, 21 ... 1st board | substrate, 12, 22 ... 2nd board | substrate, 13, 23 ... Recording layer, 14, 16, 24, 26 ... Base material, 15, 17, 25, 29 ... thermal softening layer, 18, 30 ... photosensitive material precursor.

Claims (5)

Using a substrate comprising a base material and a thermosoftening layer formed on the base material and having a midpoint glass transition temperature lower than that of the base material, a liquid or gel photosensitive material on the surface of the thermosoftening layer Contacting the precursor; and
Curing the photosensitive material precursor to form a recording layer;
Heating the thermosoftening layer at or after the formation of the recording layer at a temperature higher than the extrapolation glass transition start temperature of the thermosoftening layer and lower than the midpoint glass transition temperature of the substrate;
A method for manufacturing a hologram recording medium, comprising: The method for manufacturing a hologram recording medium according to claim 1, further comprising a step of adjusting a thickness of a hologram recording medium including the substrate and the recording layer after the step of heating the thermosoftening layer. The method for manufacturing a hologram recording medium according to claim 1, wherein the step of heating the thermosoftening layer is performed while adjusting a thickness of the hologram recording medium including the substrate and the recording layer. 2. The method of manufacturing a hologram recording medium according to claim 1, wherein rubber hardness of the heat softening layer when the heat softening layer is heated is 10 degrees or more lower than that of the heat softening layer at room temperature. 2. The method for producing a hologram recording medium according to claim 1, wherein the photosensitive material precursor includes a three-dimensional crosslinkable material.

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