Composition for holographic image recording medium

Abstract

A composition for a holographic image recording medium, which is characterized by containing the following components (a) to (d), and in that the amount of allophanate bond units contained in component (a) is 6.5 * 10-4 mol / g or more with respect to the total weight of component (a) and component (b). Component (a): a compound having an isocyanate group, component (b): a compound having an isocyanate-reactive functional group, component (c): a polymerizable monomer, and component (d): a photopolymerization initiator.

Description

Technical Field

[0001] The present invention relates to a composition for a hologram recording medium, a cured product for a hologram recording medium obtained by curing the composition for a hologram recording medium, and a hologram recording medium using the composition for a hologram recording medium. Background Art

[0002] Holographic recording media, which have attracted much attention in recent years, are recording media that utilize the interference and diffraction phenomena of light. The so-called holographic image refers to a recording technique that records the interference pattern formed by the interference fringes of two kinds of light (referred to as recording light) called reference light and object reflected light (also referred to as information light or signal light) in three dimensions inside the recording medium. The recording layer of the holographic recording medium contains a photosensitive material, which undergoes chemical changes according to the interference pattern, causing the optical properties to change locally, thereby recording the interference pattern.

[0003] Regarding holographic image recording media, development for storage purposes has been carried out. As another use of holographic image recording media, the holographic image recording media are studied for use in light-emitting components such as light guide plates of AR (Augmented Reality) glasses. In the case of AR glass (AR glasses), the light-emitting components used in the light guide plate for holographic image recording are required to have a wider viewing angle, higher diffraction efficiency for light in the visible region, and higher transparency of the medium.

[0004] Holographic image recording media are divided into several categories depending on which optical properties are changed. Volumetric holographic image media, which record by creating a refractive index difference in a recording layer with a certain thickness or more, are considered to be useful for AR glasses light guides because they save space and can achieve high diffraction efficiency and wavelength selectivity.

[0005] Examples of volume holographic recording media include a write-once format that does not require wet processing or bleaching. The recording layer of the volume holographic recording medium is generally composed of a photoactive compound and a matrix resin. For example, it is known that a photopolymer is used as a recording layer that combines a matrix resin with a photopolymerization initiator as a photoactive compound and a polymerizable reactive compound capable of free radical polymerization or cationic polymerization (Patent Documents 1 to 4).

[0006] When recording a holographic image, if there is a recording layer containing a photopolymer in the part where the reference light and the reflected light of the object intersect to form an interference pattern, then in the part with higher light intensity in the interference pattern, the photopolymerization initiator undergoes a chemical reaction to become an active substance, which acts on the polymerizable compound to polymerize the polymerizable compound. At this time, if there is a refractive index difference between the matrix resin and the polymer generated by the polymerizable compound, the interference pattern becomes a refractive index difference and is fixed in the recording layer. In addition, when the polymerizable compound is polymerized, the polymerizable compound diffuses from all around, and a concentration distribution of the polymerizable compound or its polymer is formed inside the recording layer. According to this principle, the interference pattern is recorded in the holographic image recording medium in the form of a refractive index difference.

[0007] Hereinafter, the process of changing the optical characteristics of the recording layer by exposing the recording layer of the medium under the prescribed conditions as described above is referred to as "recording exposure". The method of repeatedly recording and exposing different interference patterns at the same position by changing the intersection angle of the reference light of the recording exposure and the reflected light of the object or by changing the incident angle of each light is referred to as "multiple recording exposure". The number of times the multiple recording exposure is performed is referred to as "total multiple number". [Prior art literature] [Patent Document]

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-12249 Patent Document 2: Japanese Patent Application Publication No. 2007-34334 Patent Document 3: Japanese Patent Laid-Open No. 8-160842 Patent Document 4: Japanese Patent Application Publication No. 2003-156992 Summary of the invention [Problems to be Solved by the Invention]

[0009] When recording exposure is performed, the interval (grating pitch) of the interference pattern formed in the medium is not constant, and generally, the grating pitch is formed from narrow to wide. At this time, regardless of whether the grating pitch is narrow or wide, it is preferred that the polymerization reaction is performed equally to form a holographic image. However, the inventors have found that, depending on the medium, the performance of the holographic image formed varies with the grating pitch.

[0010] An object of the present invention is to provide a hologram recording medium whose hologram recording performance does not depend on the grating pitch. [Technical solution to the problem]

[0011] The present inventors have found that by using a recording material containing a certain amount of allophanate bond units, a holographic image recording medium can be produced in which the recording performance of the holographic image is independent of the grating pitch and the recording performance is excellent in stability. Thus, the color unevenness of the holographic image can be reduced and the brightness can be improved. That is, the gist of the present invention is as follows.

[0012] [1] A composition for holographic recording media, characterized in that it contains the following components (a) to (d), and the amount of allophanate bond units contained in component (a) is 6.5×10-4 mol / g or more relative to the total weight of components (a) and (b). Component (a): Compound having an isocyanate group Component (b): Compound having an isocyanate-reactive functional group Component (c): polymerizable monomer Component (d): Photopolymerization initiator

[0013] [2] The composition for hologram recording media according to [1], wherein the polymerizable monomer as the component (c) is a (meth)acrylic monomer.

[0014] [3] The composition for hologram recording media according to [1] or [2], wherein the molecular weight of the polymerizable monomer as the component (c) is 300 or more.

[0015] [4] The composition for holographic recording media according to any one of [1] to [3], wherein the content of the component (c) in the composition is 0.1% by weight to 80% by weight, and the content of the component (d) is 0.1% by weight to 20% by weight relative to the component (c).

[0016] [5] The composition for hologram recording media according to any one of [1] to [4], further comprising the following component (e). Component (e): Compounds containing nitroxyl free radicals

[0017] [6] The composition for hologram recording media according to [5], wherein the component (e) is a compound having an isocyanate-reactive functional group and a nitroxyl radical.

[0018] [7] The composition for hologram recording media according to [6], wherein the component (e) is 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl.

[0019] [8] The composition for hologram recording media according to any one of [5] to [7], wherein the molar ratio of the component (e) to the component (d) (component (e) / component (d)) in the composition is 0.1 to 10.

[0020] [9] A composition for a holographic recording medium according to any one of [1] to [8], wherein the total content of the component (a) and the component (b) in the composition is from 0.1% by weight to 99.9% by weight, and the ratio of the number of isocyanate-reactive functional groups contained in the component (b) to the number of isocyanate groups contained in the component (a) is from 0.1 to 10.0.

[0021]

[10] The composition for hologram recording media according to any one of [1] to [9], further comprising the following component (f). Component (f): Curing catalyst

[0022]

[11] A cured product for a hologram recording medium, obtained by curing the composition for a hologram recording medium according to any one of [1] to

[10] .

[0023]

[12] A laminate for a hologram recording medium, comprising a recording layer formed of the cured product for a hologram recording medium according to

[11] , and a support.

[0024]

[13] A hologram recording medium obtained by exposing the cured product for a hologram recording medium according to

[11] or the laminate for a hologram recording medium according to

[12] to light.

[0025]

[14] The holographic image recording medium according to

[13] is a light guide plate for AR glasses. [Effects of the Invention]

[0026] According to the present invention, by using a recording material containing a certain amount of allophanate bond units, a hologram recording medium can be produced whose hologram recording performance does not depend on the grating pitch, thereby reducing color unevenness of the hologram and improving brightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] [ Figure 1 ] Figure 1 FIG. 1 is a diagram showing the outline of a device for transmissive holographic image recording in an embodiment. [ Figure 2 ] Figure 2 It is a diagram showing the outline of the structure of the device for recording a reflective hologram in the embodiment. [reference numerals] S full range of image recording media M1, M2, M3 reflectors CS exposure time controls the shutter BS beam shutter LED post-exposure light source LD recording laser light source PD1,PD2 Photodetector PBS polarizing beam splitter. DETAILED DESCRIPTION

[0028] The following will describe the embodiments of the present invention in detail. The objects and methods described below are examples (representative examples) of the embodiments of the present invention, and are not limited to these contents unless they deviate from the gist of the present invention.

[0029] [Composition for hologram recording medium] The composition for holographic recording medium of the present invention is characterized in that it contains the following components (a) to (d), and the amount of allophanate bond units contained in component (a) is 6.5×10-4 mol / g or more relative to the total weight of components (a) and (b). Component (a): Compound having an isocyanate group Component (b): Compound having an isocyanate-reactive functional group Component (c): polymerizable monomer Component (d): Photopolymerization initiator

[0030] <Ingredients (a)> The compound having an isocyanate group as component (a) is preferably a component that reacts with a compound having an isocyanate-reactive functional group (component (b)) in the presence of a curing catalyst (component (f)) described below to form a resin matrix.

[0031] The ratio of isocyanate groups in the molecule of the compound having isocyanate groups is preferably 50% by weight or less, more preferably 47% by weight or less, and further preferably 45% by weight or less. Its lower limit is usually 0.1% by weight or more, preferably 1% by weight or more. If the ratio of isocyanate groups is below the upper limit, turbidity is not easy to occur when the holographic image recording medium is obtained. Optical uniformity can be obtained. If the ratio of isocyanate groups is above the lower limit, the hardness or glass transition temperature of the resin matrix is ​​improved, which can prevent the disappearance of the record.

[0032] The ratio of isocyanate groups in the present invention refers to the ratio of isocyanate groups in the entire compound having isocyanate groups used, and the ratio of isocyanate groups in the compound having isocyanate groups is calculated according to the following formula. The molecular weight of the isocyanate group is 42. (42×number of isocyanate groups / molecular weight of compound having isocyanate groups)×100

[0033] The type of the compound with an isocyanate group is not particularly limited, for example, it may have an aromatic, aromatic aliphatic, aliphatic or alicyclic skeleton. In addition, the compound with an isocyanate group may have one isocyanate group in the molecule, or may have more than two isocyanate groups, preferably more than two isocyanate groups. The reason is that, according to the three-dimensional cross-linked matrix obtained by the compound (component (a)) having more than two isocyanate groups in the molecule and the compound (component (b)) having more than three isocyanate reactive functional groups in the molecule or the compound (component (a)) having more than three isocyanate groups in the molecule and the compound (component (b)) having more than two isocyanate reactive functional groups in the molecule, a recording layer with excellent record retention can be obtained.

[0034] Examples of the compound having an isocyanate group include isocyanic acid, butyl isocyanate, octyl isocyanate, butyl diisocyanate, hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,2,4-trimethylhexamethylene diisocyanate or 2,4,4-trimethylhexamethylene diisocyanate, isomers of bis(4,4′-isocyanatocyclohexyl)methane, and any of the above compounds. An isomer mixture having the desired isomer content, isocyanate methyl-1,8-octane diisocyanate, 1,4-cyclohexyl diisocyanate, isomeric cyclohexane dimethylene diisocyanate, 1,4-phenyl diisocyanate, 2,4-toluene diisocyanate or 2,6-toluene diisocyanate, 1,5-naphthyl diisocyanate, 2,4'-diphenylmethane diisocyanate or 4,4'-diphenylmethane diisocyanate, triphenylmethane 4,4',4"-triisocyanate, and the like.

[0035] Furthermore, isocyanate derivatives having a urethane, urea, carbodiimide, acrylate urea, isocyanurate, allophanate, biuret, oxadiazinedione, uretdione and / or iminooxadiazinedione structure can also be used.

[0036] In the composition for hologram recording media of the present invention, a compound having an isocyanate group and having an allophanate bond unit represented by the following formula (I) is used as the compound having an isocyanate group of the component (a).

[0037] [Chemical formula 1]

[0038] The allophanate bond unit is generated by reacting a carbamate bond with an isocyanate group. Therefore, the compound with an isocyanate group having the allophanate bond unit represented by the above-mentioned formula (I) can be obtained, for example, as follows, by reacting a polyfunctional isocyanate with an alcohol to obtain a carbamate compound of a polyfunctional isocyanate, and then reacting with a compound with an isocyanate group.

[0039] Examples of the polyfunctional isocyanate used in the reaction include hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,2,4-trimethylhexamethylene diisocyanate or 2,4,4-trimethylhexamethylene diisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane, and any isocyanate having a desired isomeric content. isocyanate, isocyanate methyl-1,8-octane diisocyanate, 1,4-cyclohexyl diisocyanate, isomeric cyclohexane dimethylene diisocyanate, 1,4-phenyl diisocyanate, 2,4-toluene diisocyanate or 2,6-toluene diisocyanate, 1,5-naphthyl diisocyanate, 2,4'-diphenylmethane diisocyanate or 4,4'-diphenylmethane diisocyanate, triphenylmethane 4,4',4"-triisocyanate, etc. These may be used alone or in any combination and in any ratio.

[0040] Examples of the alcohol include linear aliphatic monohydric alcohols and branched aliphatic monohydric alcohols. Examples of the linear aliphatic monohydric alcohol include linear aliphatic monohydric alcohols having 1 to 20 carbon atoms. Examples of the linear aliphatic monohydric alcohols having 1 to 20 carbon atoms include methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n-dodecyl alcohol (lauryl alcohol), n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, n-octadecanol (stearyl alcohol), n-nonadecanol, and eicosanol. Examples of the branched aliphatic monohydric alcohol include branched aliphatic monohydric alcohols having 3 to 20 carbon atoms. Examples of the branched aliphatic monohydric alcohols having 3 to 20 carbon atoms include isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isopentanol, isohexanol, isoheptanol, isooctyl alcohol, 2-ethylhexanol, isononanol, isodecanol, 5-ethyl-2-nonanol, trimethylnonanol, 2-hexyldecanol, 3,9-diethyl-6-tridecanol, 2-isoheptylisoundecanol, and 2-octyldodecanol. These may be used alone or in any combination and in any ratio.

[0041] In the present invention, as the component (a), the compound having an isocyanate group and containing an allophanate bond unit as described above is used in an amount as shown below. If the amount of the allophanate bond unit is within the following range, as the compound having an isocyanate group, only the compound having an isocyanate group containing an allophanate bond unit may be used, or a compound having an isocyanate group containing an allophanate bond unit and a compound having an isocyanate group not containing an allophanate bond unit may be used in combination.

[0042] In the composition for holographic recording medium of the present invention, the amount of the allophanate bond unit contained in the compound having an isocyanate group as component (a) is usually 6.5×10 -4 mol / g or more, preferably 7.0×10 -4 mol / g or more. By making the amount of the allophanate bond unit present be above the lower limit, the mobility of the polymerizable monomer (component (c)) described later in the matrix can be ensured, and the polymerizable monomer can be consumed efficiently during recording. That is, the allophanate bond unit has a weaker intermolecular force than the urethane bond, so the interaction with the polymerizable monomer is small, so that the diffusion coefficient of the polymerizable monomer in the composition can be maintained, thereby suppressing the dependence of the holographic image recording on the grating spacing, thereby reducing color unevenness and improving brightness. On the other hand, the amount of the allophanate bond unit contained in the isocyanate group-containing compound of component (a) is preferably 2.0×10 -3 mol / g or less, more preferably 1.8×10 -3 mol / g or less, more preferably 1.5×10 -3 When the amount of the allophanate bond units is below the upper limit, the affinity of the polymerizable monomer (component (c)) described later and the matrix is ​​improved, and turbidity is less likely to occur when the hologram recording medium is prepared.

[0043] The amount of allophanate bond unit can be calculated and obtained according to the total weight of the compound with isocyanate group used as component (a) and the compound with isocyanate reactive functional group used as component (b), and the molar amount of the allophanate bond unit in component (a). About its calculation method, it will be described in the project of embodiment described later.

[0044] <Ingredient (b)> The compound having an isocyanate-reactive functional group of component (b) means a compound having active hydrogen (isocyanate-reactive functional group) that participates in the chain extension reaction with the compound having an isocyanate group of component (a). Examples of isocyanate-reactive functional groups include hydroxyl, amine, and mercapto. The compound having an isocyanate-reactive functional group may have one isocyanate-reactive functional group in the molecule, or may have two or more isocyanate-reactive functional groups, preferably two or more isocyanate-reactive functional groups. It should be noted that, in the case of having two or more isocyanate-reactive functional groups, the isocyanate-reactive functional groups contained in one molecule may be one or more.

[0045] The number average molecular weight of the compound with isocyanate reactive functional groups is usually more than 50, preferably more than 100, more preferably more than 150. In addition, it is usually less than 50000, less than 10000, more preferably less than 5000. When the number average molecular weight of the compound with isocyanate reactive functional groups is more than the lower limit, the cross-linking density decreases, and the recording speed can be prevented from slowing down. When the number average molecular weight of the compound with isocyanate reactive functional groups is less than the upper limit, due to the improved compatibility with other components or the promotion of cross-linking density, the disappearance of the recorded content can be prevented.

[0046] The number average molecular weight of the component (b) is a value measured by gel permeation chromatography (GPC).

[0047] (Compounds having hydroxyl groups) The compound having a hydroxyl group as an isocyanate-reactive functional group only needs to have one or more hydroxyl groups in one molecule, and preferably has two or more hydroxyl groups. Examples thereof include glycols such as ethylene glycol, triethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol (PPG), and neopentyl glycol; diols such as butanediol, pentanediol, hexanediol, heptanediol, 1,4-butanediol (TMG), and poly 1,4-butanediol (PTMG); bisphenols; triols such as glycerol, trimethylolpropane, butanetriol, pentanetriol, hexanetriol, and decantriol; compounds obtained by modifying these polyfunctional alcohols with polyethylene oxide chains or polypropylene oxide chains; polyfunctional polyoxybutylene; polyfunctional polycaprolactone; polyfunctional polyester; polyfunctional polycarbonate; polyfunctional polypropylene glycol, etc. These may be used alone or in any combination and in any ratio.

[0048] The number average molecular weight of the compound with hydroxyl group is usually more than 50, preferably more than 100, more preferably more than 150. In addition, it is usually less than 50000, less than 10000, more preferably less than 5000. When the number average molecular weight of the compound with hydroxyl group is more than the lower limit, the cross-linking density decreases, which can prevent the recording speed from slowing down. When the number average molecular weight of the compound with hydroxyl group is less than the upper limit, due to the improved compatibility with other components or the improved cross-linking density, it is possible to prevent the disappearance of the recorded content.

[0049] (Compounds having an amine group) The compound having an amine group as an isocyanate-reactive functional group only needs to have one or more amine groups in one molecule, and preferably has two or more amine groups. Examples thereof include: aliphatic amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, and hexamethylenediamine; alicyclic amines such as isophoronediamine, menthanediamine, and 4,4'-diaminodicyclohexylmethane; aromatic amines such as meta-xylylenediamine, diaminodiphenylmethane, and meta-phenylenediamine. Any of these may be used alone, or two or more may be used in any combination and ratio.

[0050] The number average molecular weight of the compound with an amine group is usually more than 50, preferably more than 100, more preferably more than 150. In addition, it is usually less than 50000, less than 10000, more preferably less than 5000. When the number average molecular weight of the compound with an amine group is more than the lower limit, the cross-linking density decreases, which can prevent the recording speed from slowing down. When the number average molecular weight of the compound with an amine group is less than the upper limit, due to the improved compatibility with other components or the improved cross-linking density, the disappearance of the recorded content can be prevented.

[0051] (Compounds having a mercapto group) The compound having a mercapto group as an isocyanate-reactive functional group only needs to have one or more mercapto groups in one molecule, and preferably has two or more mercapto groups. As examples thereof, 1,3-butanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 1,10-decandithiol, 1,2-ethanedithiol, 1,6-hexanedithiol, 1,9-nonanedithiol, pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), pentaerythritol tetrakis (3-mercaptobutyrate), trimethylolpropane tris (3-mercaptopropionate), dipentaerythritol hexa (3-mercaptopropionate), 1,4-bis (3-mercaptobutyryloxy) butane, etc., can be cited. Any one of these can be used alone, or two or more can be used in any combination and ratio.

[0052] The number average molecular weight of the compound with sulfhydryl group is usually more than 50, preferably more than 100, more preferably more than 150. In addition, it is usually less than 50000, less than 10000, more preferably less than 5000. When the number average molecular weight of the compound with sulfhydryl group is more than the lower limit, the cross-linking density decreases, which can prevent the recording speed from slowing down. When the number average molecular weight of the compound with sulfhydryl group is less than the upper limit, due to the improved compatibility with other components or the improved cross-linking density, the disappearance of the recorded content can be prevented.

[0053] As the component (b), polycaprolactones are preferably used from the viewpoint of stability as a material and flexibility of the structure. Regarding the polycaprolactones used as component (b), for example, polyols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, methyl pentanediol, 2,4-diethyl pentanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, trimethylolpropane, di-trimethylolpropane, pentaerythritol, and dipentaerythritol; or polypropylene glycol, polybutylene glycol (PTMG) and other diols, such as polycaprolactone polyols (polycaprolactone diol, polycaprolactone triol, etc.) obtained by ring-opening polymerization of ε-caprolactone, etc., can be mentioned. Any one of these can be used alone, or two or more can be used in any combination and ratio.

[0054] <Ingredient (c)> The polymerizable monomer of the component (c) is a compound that can be polymerized by the photopolymerization initiator of the component (d) described later, and is a monomer compound that polymerizes during recording and / or post-exposure.

[0055] The type of polymerizable monomer used in the composition for holographic image recording medium of the present invention is not particularly limited and can be appropriately selected from known compounds. Examples of polymerizable monomers include cationic polymerizable monomers, anionic polymerizable monomers, free radical polymerizable monomers, etc. Any one of these can be used, and two or more can also be used in combination. Among them, it is preferred to use a free radical polymerizable monomer as component (c) because it is not easy to hinder the reaction of the compound having an isocyanate group and the compound having an isocyanate-reactive functional group to form a matrix.

[0056] (Cationic polymerizable monomer) Examples of cationic polymerizable monomers include epoxy compounds, oxetane compounds, oxolane compounds, cyclic acetal compounds, cyclic lactone compounds, thiirane compounds, thietane compounds, vinyl ether compounds, spiroester compounds, ethylenically unsaturated bond compounds, cyclic ether compounds, cyclic thioether compounds, vinyl compounds, etc. The cationic polymerizable monomers may be used alone or in any combination and ratio.

[0057] (Anionic polymerizable monomer) Examples of the anionic polymerizable monomer include hydrocarbon monomers and polar monomers. Examples of the hydrocarbon monomer include styrene, α-methylstyrene, butadiene, isoprene, vinylpyridine, vinylanthracene, and derivatives thereof. Examples of the polar monomer include methacrylates, acrylates, vinyl ketones, isopropenyl ketones, and other polar monomers. The anionic polymerizable monomers exemplified above may be used alone or in combination of two or more in any combination and ratio.

[0058] (Free radical polymerizable monomer) Examples of free radical polymerizable monomers include compounds having a (meth)acryloyl group, (meth)acrylamides, vinyl esters, vinyl compounds, styrenes, spiro ring-containing compounds, etc. The free radical polymerizable monomers exemplified above may be used alone or in any combination and ratio.

[0059] In this specification, methacrylic acid and acrylic acid are generally referred to as (meth)acrylic acid-based.

[0060] Among the above, from the viewpoint of steric hindrance during radical polymerization, a compound having a (meth)acryloyl group is more preferred.

[0061] (Molecular weight of polymerizable monomer) The molecular weight of the polymerizable monomer used in the composition for holographic recording medium of the present invention is usually 80 or more, preferably 150 or more, and more preferably 300 or more. In addition, it is usually 3000 or less, preferably 2500 or less, and more preferably 2000 or less. By making the molecular weight above the lower limit, the shrinkage rate of polymerization accompanying light irradiation during holographic image information recording can be reduced. By making the molecular weight below the upper limit, the mobility of the polymerizable monomer in the recording layer using the composition for holographic recording medium is high, diffusion occurs easily, and sufficient diffraction efficiency can be obtained.

[0062] (Refractive index of polymerizable monomer) The refractive index of the polymerizable monomer at the wavelength of the irradiated light (recording wavelength, etc.) to the holographic image recording medium is usually 1.50 or more, preferably 1.52 or more, more preferably 1.55 or more, and usually 1.80 or less, preferably 1.78 or less. If the refractive index is too small, the diffraction efficiency is insufficient and the multiplicity is sometimes insufficient. If the refractive index is too large, the refractive index difference with the resin matrix becomes too large, the scattering becomes larger, resulting in a decrease in transmittance, and more energy is required when recording or reproducing. Regarding the refractive index, when evaluated at a short wavelength, a larger value is shown, but a sample showing a relatively large refractive index at a short wavelength will also show a relatively large refractive index at a long wavelength, and the relationship is not reversed. Therefore, the refractive index can also be evaluated at a wavelength other than the recording wavelength, and the refractive index at the recording wavelength can be predicted.

[0063] When the sample is in liquid form, the refractive index of the polymerizable monomer can be measured using the minimum deflection angle method, the critical angle method, the V-block method, etc. When the sample is in solid form, the compound can be dissolved in a suitable solvent to prepare a solution, the refractive index of the solution can be measured, and the refractive index when the compound is 100% can be obtained by extrapolation.

[0064] As the polymerizable monomer having a relatively high refractive index, a compound having a halogen atom (iodine, chlorine, bromine, etc.) or a compound having a heteroatom (nitrogen, sulfur, oxygen, etc.) in the molecule is preferred, and a compound having a heterocyclic structure is more preferred.

[0065] (Molar absorption coefficient of polymerizable monomer) The molar absorption coefficient of the polymerizable monomer at the holographic image recording wavelength is preferably 100 L·mol-1·cm-1 or less. By setting the molar absorption coefficient to 100 L·mol-1·cm-1 or less, the transmittance of the medium can be prevented from being reduced, thereby obtaining sufficient diffraction efficiency relative to the thickness.

[0066] <Ingredient (d)> The photopolymerization initiator refers to cations, anions, and free radicals that are generated by light and cause a chemical reaction, and contribute to the polymerization of the polymerizable monomer. The type of the photopolymerization initiator is not particularly limited, and can be appropriately selected according to the type of the polymerizable monomer.

[0067] Any known cationic photopolymerization initiator can be used as the cationic photopolymerization initiator. As an example, an aromatic onium salt can be mentioned. As a specific example, SbF6 can be mentioned. - 、BF4 - 、AsF6 - PF6 - CF3SO3 - 、B(C6F5)4- The invention also includes compounds containing anion components such as iodine, sulfur, nitrogen, phosphorus, etc., and aromatic cationic components such as iodine, sulfur, nitrogen, phosphorus, etc. Among them, diaryliodonium salts, triarylsulfonium salts, etc. are preferred. The cationic photopolymerization initiators exemplified above may be used alone or in combination of two or more in any ratio.

[0068] Any known anionic photopolymerization initiator can be used as the anionic photopolymerization initiator. As examples, amines can be cited. Examples of amines include amino-containing compounds such as dimethylbenzylamine, dimethylaminomethylphenol, 1,8-diazabicyclo[5.4.0]undecene-7, and their derivatives; imidazole compounds such as imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, and their derivatives. The anionic photopolymerization initiators exemplified above may be used alone or in combination of two or more in any ratio.

[0069] Any known free radical photopolymerization initiator can be used as the free radical photopolymerization initiator. For example, phosphine oxide compounds, azo compounds, azide compounds, organic peroxides, organic borates, onium salts, bisimidazole derivatives, titanocene compounds, iodonium salts, organic thiol compounds, halogenated hydrocarbon derivatives, oxime ester compounds, etc. can be used. The above-exemplified photoradical polymerization initiators may be used alone or in combination of two or more in any ratio.

[0070] Other examples of the photopolymerization initiator include imidazole derivatives or oxadiazole derivatives, naphthalene, perylene, pyrene, anthracene, coumarin, 4-Bis(2-phenylvinyl)benzene and its derivatives, quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al(C9H6NO)3, rubrene, piperidone derivatives, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, phenylpyridine complexes, porphyrin complexes, polyphenylene vinylene materials, etc.

[0071] As the photopolymerization initiator, a photopolymerization initiator having a molar absorption coefficient of 1000 L·mol at the recording wavelength is particularly preferred. -1 cm -1 The following compounds. By making the molar absorption coefficient 1000 L·mol -1 cm -1 Thereby, it is possible to suppress a decrease in the transmittance of the hologram recording medium at a recording wavelength which occurs when mixing is performed in such an amount as to obtain a sufficient diffraction efficiency.

[0072] <Ingredient (e)> The composition for hologram recording media of the present invention preferably contains a compound having a nitroxyl radical as a component (e) as an optional component. As the compound having a nitroxyl radical as component (e), a compound having an isocyanate-reactive functional group and a nitroxyl radical is preferably used. When the composition for holographic recording medium of the present invention contains such a component (e), the isocyanate-reactive functional group of the component (e) reacts with the isocyanate group of the component (a) to be fixed in the resin matrix, and the nitroxyl radical contained in the component (e) can improve the recording sensitivity and achieve a higher Δn.

[0073] The isocyanate-reactive functional group contained in the component (e) may be the same as the isocyanate-reactive functional group contained in the component (b).

[0074] The type of component (e) is not particularly limited. Specific examples thereof include 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL), 4-mercapto-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-mercapto-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-carboxy-2,2,6,6-tetramethylpiperidin-1-oxyl, pyrrolidine-1-oxyl, 4-carbamoyl-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-(2,3-epoxypropoxy)-2,2,6,6-tetramethylpiperidin-1-oxyl, 3-hydroxy-2,2,5,5-tetramethylpyrrolidin-1-oxyl, 3-mercapto-2,2,5,5-tetramethylpyrrolidin-1-oxyl, 3-amino-2,2,5,5-tetramethylpyrrolidin-1-oxyl, 3-mercapto-2,2,5,5-tetramethylpyrrolidin-1-oxyl, 5,5-tetramethylpyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 3-(2,3-epoxypropoxy)-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 3-hydroxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 3-mercapto-2,2,5,5-tetramethylpyrrolidine-1-oxyl Stable nitroxyl free radical compounds such as 3-amino-2,2,5,5-tetramethylpyrroline-1-oxyl, 3-thiol-2,2,5,5-tetramethylpyrroline-1-oxyl, 3-carboxy-2,2,5,5-tetramethylpyrroline-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrroline-1-oxyl, and 3-(2,3-epoxypropoxy)-2,2,5,5-tetramethylpyrroline-1-oxyl. However, component (e) is not limited to any of these. These compounds may be used alone or in any combination and in any ratio. These nitroxyl radicals are preferably stable radicals.

[0075] Among them, from the viewpoint of the stability of the compound and the reactivity with isocyanate groups, TEMPOL, 4-mercapto-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl and 4-mercapto-2,2,6,6-tetramethylpiperidin-1-oxyl are preferably used, and TEMPOL is particularly preferred.

[0076] <Ingredients (f)> The composition for holographic recording medium of the present invention preferably further comprises a curing catalyst as component (f) that promotes the reaction between the compound having an isocyanate group of component (a) and the compound having an isocyanate-reactive functional group of component (b). As the curing catalyst of component (f), a bismuth-based catalyst that functions as a Lewis acid is preferably used.

[0077] Examples of bismuth-based catalysts include bismuth tris(2-ethylhexanoate), bismuth tribenzoyloxy, bismuth triacetate, bismuth tris(dimethyldithiocarbamate), bismuth hydroxide, triphenylbismuth(V)bis(trichloroacetate), tris(4-methylphenyl)bismuth(V)oxide, and triphenylbis(3-chlorobenzoyloxy)bismuth(V).

[0078] Among them, in consideration of catalyst activity, trivalent bismuth compounds are preferred, and bismuth carboxylates represented by the general formula Bi(OCOR)3 (R is a linear or branched alkyl, cycloalkyl, or substituted or unsubstituted aromatic group) are more preferred. The bismuth-based catalysts may be used alone or in any combination and ratio.

[0079] In addition, as a curing catalyst, in order to adjust the reaction rate, the bismuth-based catalyst and other curing catalysts can also be used together. As a catalyst that can be used together, as long as it does not violate the purpose of the present invention, there is no particular limitation. In order to obtain the synergistic effect of the catalyst, it is preferred to use a compound having an amino group in a part of the structure. As an example, it can be cited: triethylamine (TEA), N,N-dimethylcyclohexylamine (DMEDA), N,N,N',N'-tetramethylethylenediamine (TMEDA), N,N,N',N'-tetramethylpropane-1,3-diamine (TMPDA), N,N,N',N'-tetramethylhexane-1,6-diamine (TMHMDA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA), N,N,N',N",N"-pentamethyldipropylenetriamine (PMDPTA), triethylenediamine (TEDA), N,N'-dimethylpiperidin (DMP), N,-methyl, N'-(2-dimethylamino)-ethylpiperidin Amine compounds such as (TMNAEP), N-methylmorpholine (NMMO), N-(N',N'-dimethylaminoethyl)-morpholine (DMAEMO), bis(2-dimethylaminoethyl) ether (BDMEE), ethylene glycol bis(3-dimethyl)-aminopropyl ether (TMEGDA), and diisopropylethylamine (DIEA). These may be used alone or in any combination and in any ratio.

[0080] <Other ingredients> The composition for hologram recording media of the present invention may contain other components in addition to the above components (a) to (f) unless it deviates from the gist of the present invention.

[0081] Other components include: solvents, plasticizers, dispersants, leveling agents, defoamers, adhesion promoters, etc. for preparing the recording layer of the holographic image recording medium; or chain transfer agents, polymerization terminators, compatibilizers, reaction adjuvants, sensitizers, antioxidants, etc. for controlling the recording reaction. These components may be used alone or in any combination and ratio.

[0082] <Composition ratio of each component in the composition for hologram recording medium> The content of each component in the composition for hologram recording media of the present invention is arbitrary unless it violates the gist of the present invention, but the content of each component is preferably within the following range.

[0083] The total content of component (a) and component (b) of the composition for holographic recording medium of the present invention is usually 0.1% by weight or more, preferably 10% by weight or more, and more preferably 35% by weight or more. In addition, it is usually 99.9% by weight or less, preferably 99% by weight or less, and more preferably 98% by weight or less. By making this content above the lower limit, it is easy to form a recording layer. By making this content below the upper limit, the content of other essential components can be ensured.

[0084] In the composition for holographic recording medium of the present invention, on the basis of satisfying the amount of the allophanate bond unit present, the ratio of the number of isocyanate reactive functional groups of component (b) to the number of isocyanate groups of component (a) is preferably 0.1 or more, more preferably 0.5 or more. In addition, the ratio is usually 10.0 or less, preferably 2.0 or less. By making the ratio within the above range, the unreacted functional groups are less, and the storage stability is improved.

[0085] The content of component (c) of the composition for holographic recording medium of the present invention is usually 0.1% by weight or more, preferably 1% by weight or more, and more preferably 2% by weight or more. In addition, it is usually 80% by weight or less, preferably 50% by weight or less, and more preferably 30% by weight or less. By making the amount of component (c) above the lower limit, sufficient diffraction efficiency can be obtained. By making the amount of component (c) below the upper limit, the compatibility of the recording layer is ensured.

[0086] The content of component (d) of the composition for holographic recording medium of the present invention is generally 0.1% by weight or more, preferably 0.2% by weight or more, and more preferably 0.3% by weight or more relative to the content of component (c). In addition, it is generally 20% by weight or less, preferably 18% by weight or less, and more preferably 16% by weight or less. By making the ratio of component (d) above the lower limit, sufficient recording sensitivity can be obtained. If the ratio of component (d) is below the upper limit, the bimolecular termination reaction caused by the generation of too many free radicals can be suppressed, thereby causing a decrease in sensitivity.

[0087] When the hologram recording medium composition of the present invention contains component (e), the content of component (e) is preferably such that the molar ratio of component (e) to component (d) (component (e) / component (d)) is usually 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, and is usually 10 or less, preferably 8 or less, more preferably 6 or less. When the ratio of component (e) / component (d) is greater than or equal to the above lower limit, the effect of increasing Δn due to the inclusion of component (e) can be effectively obtained. When the ratio of component (e) / component (d) is less than or equal to the above upper limit, a free radical polymerization reaction can be carried out during exposure of the recording target, and the refractive index modulation required for forming the diffraction grating can be obtained, thereby obtaining sufficient recording sensitivity.

[0088] The content of component (f) in the hologram recording medium composition of the present invention is preferably determined in consideration of the reaction rates of components (a) and (b), and is usually 5 wt % or less, preferably 4 wt % or less, more preferably 1 wt % or less, and preferably 0.001 wt % or more.

[0089] The total amount of the components other than components (a) to (f) in the hologram recording medium composition of the present invention is usually 30% by weight or less, preferably 15% by weight or less, and more preferably 5% by weight.

[0090] <Method for producing composition for hologram recording medium and cured product for hologram recording medium> When producing the composition for hologram recording medium of the present invention, components (a) to (d), preferably components (a) to (e), and more preferably components (a) to (f) can be mixed in any combination and order, and other components may be mixed in combination. By curing the obtained composition for hologram recording media, the cured product for hologram recording media of the present invention can be obtained. At this time, heating may be performed at 30 to 100° C. for about 1 to 72 hours in order to promote the curing reaction.

[0091] The composition for hologram recording media and the cured product for hologram recording media of the present invention can also be produced according to the method for forming a recording layer in the method for producing a hologram recording medium of the present invention described later.

[0092] [Holographic image recording medium] The hologram recording medium of the present invention can be obtained by subjecting the cured product for the hologram recording medium of the present invention to interference exposure.

[0093] Hereinafter, preferred embodiments of the hologram recording medium of the present invention will be described.

[0094] The holographic image recording medium of the present invention comprises a recording layer and a support or other layers as required. Generally speaking, the holographic image recording medium has a support, and the recording layer and other layers are stacked on the support to constitute the holographic image recording medium. However, when the recording layer and other layers have the strength or durability required for the medium, the holographic image recording medium may not have a support. Examples of other layers include: a protective layer, a reflective layer, an anti-reflective layer (anti-reflective film), etc.

[0095] The recording layer of the hologram recording medium of the present invention is preferably formed from the composition for hologram recording medium of the present invention.

[0096] <Recording layer> The recording layer of the holographic recording medium of the present invention is a layer formed of the composition for holographic recording medium of the present invention, and is a layer for recording information. The information is usually recorded in the form of a holographic image. As described in detail in the recording method section described later, the polymerizable monomers contained in the recording layer undergo chemical changes such as polymerization due to the holographic image recording, etc. Therefore, in the holographic image recording medium after recording, a part of the polymerizable monomers is consumed and exists in the form of a reacted compound such as a polymer.

[0097] The thickness of the recording layer is not particularly limited, and can be appropriately determined in consideration of the recording method, etc. Generally speaking, it is usually 1 μm or more, preferably 10 μm or more, and usually 3000 μm or less, preferably 2000 μm or less. By making the thickness of the recording layer above the lower limit, when multiple recording is performed on the holographic image recording medium, the selectivity of each holographic image becomes higher, and the degree of multiple recording can be improved. By making the thickness of the recording layer below the upper limit, the entire recording layer can be uniformly formed, and the diffraction efficiency of each holographic image can be made uniform and multiple recording with a high S / N ratio can be performed.

[0098] The shrinkage rate of the recording layer due to exposure during recording and reproducing of information is preferably 0.5% or less.

[0099] <Support body> The support is not particularly limited in detail as long as it has the strength and durability required for the medium, and any support can be used. The shape of the support is not limited, but is usually formed into a flat plate or a film. The material constituting the support is also not limited and may be transparent or opaque.

[0100] As the material of the support, for example, transparent materials include organic materials such as acrylic acid, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, amorphous polyolefin, polystyrene, and cellulose acetate; and inorganic materials such as glass, silicon, and quartz. Among them, polycarbonate, acrylic acid, polyester, amorphous polyolefin, and glass are preferred, and polycarbonate, acrylic acid, amorphous polyolefin, and glass are more preferred.

[0101] Examples of the material of the support include, for example, opaque materials such as metals such as aluminum; and materials obtained by coating the transparent support with metals such as gold, silver, and aluminum, or dielectrics such as magnesium fluoride and zirconium oxide.

[0102] The thickness of the support is also not particularly limited, and is generally preferably in the range of 0.05 mm to 1 mm. If the thickness of the support is above the lower limit, the mechanical strength of the holographic image recording medium can be obtained, and the warping of the substrate can be prevented. If the thickness of the support is below the upper limit, the light transmission amount can be ensured, and the cost increase can be suppressed.

[0103] The surface of the support may also be subjected to a surface treatment. This surface treatment is generally used to improve the adhesion between the support and the recording layer. Examples of surface treatment include: subjecting the support to a corona discharge treatment, or pre-forming an undercoat layer on the support. Here, as the composition of the undercoat layer, examples include: halogenated benzene, or partially hydrolyzed vinyl chloride-vinyl acetate copolymer, polyurethane resin, etc.

[0104] Furthermore, surface treatment may be performed for purposes other than improving adhesion. Examples thereof include the following treatments: a reflective coating treatment for forming a reflective coating made of a metal such as gold, silver, or aluminum; and a dielectric coating treatment for forming a dielectric layer such as magnesium fluoride or zirconium oxide. These layers may be formed as a single layer or may be formed as two or more layers. These surface treatments may also be performed to control the gas or water permeability of the substrate. For example, by providing the support sandwiching the recording layer with the function of suppressing the gas or water permeability, the reliability of the medium can be further improved.

[0105] The support may be disposed only on either the upper side or the lower side of the recording layer of the holographic image recording medium of the present invention, or may be disposed on both sides. When the support is disposed on both the upper and lower sides of the recording layer, at least one of the supports is configured to be transparent so that active energy rays (excitation light, reference light, reproduction light, etc.) can pass through. When the hologram recording medium has a support on one or both sides of the recording layer, a transmissive hologram or a reflective hologram can be recorded. When a support having a reflective property is used on one side of the recording layer, a reflective hologram can be recorded.

[0106] Furthermore, the support may be provided with a pattern for data addressing. The patterning method in this case is not limited, for example, the support itself may be provided with a concave-convex pattern, a pattern may be provided on a reflective layer described later, or a combination of these methods may be used.

[0107] <Protective layer> The protective layer is a layer used to prevent the recording layer from being affected by oxygen or moisture, such as a decrease in sensitivity or degradation of storage stability. The specific composition of the protective layer is not limited, and any known composition can be applied arbitrarily. For example, a layer containing a water-soluble polymer, an organic / inorganic material, etc. can be formed as the protective layer. The position where the protective layer is formed is not particularly limited, and it can be formed, for example, on the surface of the recording layer, or between the recording layer and the support. The protective layer can also be formed on the outer surface side of the support. The protective layer can also be formed between the support and other layers.

[0108] <Reflective layer> The reflective layer is formed when the medium is configured as a reflective holographic image recording medium. In the case of a reflective holographic image recording medium, the reflective layer can be formed between the support and the recording layer, or can be formed on the outer side of the support. Generally speaking, the reflective layer is preferably located between the support and the recording layer. As the reflective layer, any known reflective layer can be used, and for example, a metal thin film can be used.

[0109] <Anti-reflective film> When the medium of the present invention is configured as either a transmission type holographic image recording medium or a reflection type holographic image recording medium, an anti-reflection film may be provided on the incident and emitting sides of the object reflected light and the read light, or between the recording layer and the support. The anti-reflection film has the effect of improving the light utilization efficiency and suppressing the generation of ghost images. As the antireflection film, any known antireflection film can be used.

[0110] <Method for producing holographic image recording medium> The method for producing the hologram recording medium of the present invention is not limited, and can be produced, for example, by coating the hologram recording medium composition of the present invention on a support in the absence of a solvent to form a recording layer. Any method may be used to apply the composition for holographic recording media, and specific examples include spraying, spin coating, wire bar coating, dipping, air knife coating, roll coating, blade coating, and blade roll coating. When forming a recording layer, especially a thick recording layer, the following method can be used: a method of placing the composition for holographic image recording medium of the present invention into a mold for molding, or a method of applying the composition for recording layer formation on a release film and punching out the mold. Alternatively, the holographic recording medium composition of the present invention may be mixed with a solvent or an additive to prepare a coating solution, and the coating solution may be applied to a support and dried to form a recording layer. In this case, any coating method may be used, for example, the same method as described above.

[0111] The solvent used in the coating solution is not limited. Generally speaking, it is preferred to use a solvent that has sufficient solubility for the used components, can impart good coating properties, and does not penetrate into the support such as the resin substrate. Examples of solvents include: ketone solvents such as acetone and methyl ethyl ketone; aromatic solvents such as toluene and xylene; alcohol solvents such as methanol and ethanol; ketone alcohol solvents such as diacetone alcohol; ether solvents such as tetrahydrofuran; halogen solvents such as dichloromethane and chloroform; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; propylene glycol solvents such as propylene glycol monomethyl ether and propylene glycol monoethyl ether; ester solvents such as ethyl acetate and methyl 3-methoxypropionate; perfluoroalkyl alcohol solvents such as tetrafluoropropanol; high polar solvents such as dimethylformamide and dimethyl sulfoxide; chain hydrocarbon solvents such as n-hexane; cyclic hydrocarbon solvents such as cyclohexane and cyclooctane; or mixed solvents thereof. It should be noted that the solvent can be used alone or in any combination and ratio. The amount of the solvent used is not limited, but from the viewpoint of coating efficiency and workability, it is preferred to prepare a coating liquid having a solid content concentration of about 1 to 1000% by weight.

[0112] Furthermore, when the resin matrix formed by components (a) and (b) of the holographic image recording medium composition of the present invention is thermoplastic, the holographic image recording medium composition of the present invention can be formed into a recording layer by, for example, injection molding, sheet forming, hot pressing, etc. In addition, when the resin matrix formed by components (a) and (b) is a photocurable or thermosetting resin matrix having a relatively low volatile component, the composition for holographic recording medium of the present invention can be formed into a recording layer by, for example, reaction injection molding or liquid injection molding. In this case, if the molded product has sufficient thickness, rigidity, strength, etc., the molded product can be used directly as a holographic recording medium.

[0113] In addition, as a method for producing a holographic image recording medium, for example, the following methods can be cited: a method in which a composition for a holographic image recording medium that is melted by heat is applied to a support, and the composition is cooled to solidify to form a recording layer; a method in which a liquid holographic image recording medium composition is applied to a support, and the composition is thermally polymerized to solidify to form a recording layer; a method in which a liquid holographic image recording medium composition is applied to a support, and the composition is photopolymerized to solidify to form a recording layer.

[0114] The holographic image recording medium thus prepared can be in the form of a self-standing flat plate or disc, and can be used in three-dimensional image display devices or diffraction light-emitting components, large-capacity storage devices, and other uses. In particular, the hologram recording medium of the present invention using the hologram recording medium composition of the present invention not only has a high Δn but also can reduce color unevenness and improve brightness, and can be effectively used as a light guide plate for AR glass.

[0115] <Application of large-capacity storage> The writing (recording) and reading (reproducing) of information on the hologram recording medium of the present invention are both performed by irradiation with light. First, when recording information, light that can chemically change a polymerizable monomer, that is, polymerize it and change its concentration, is used as object-reflected light.

[0116] For example, when recording information in the form of a volume hologram, the object reflected light and the reference light are simultaneously irradiated to the recording layer, so that the object reflected light and the reference light interfere with each other in the recording layer. Thus, the interference light causes the polymerizable monomer in the recording layer to polymerize and change its concentration, and as a result, interference fringes cause a refractive index difference in the recording layer, and the information is recorded in the recording layer in the form of a hologram based on the interference fringes recorded in the recording layer.

[0117] On the other hand, when reproducing the volume hologram recorded in the recording layer, a predetermined reproduction light (usually a reference light) is irradiated to the recording layer. The irradiated reproduction light is diffracted according to the interference fringes. Since the diffracted light contains the same information as the recording layer, the diffracted light is read by using a suitable detection method, thereby reproducing the information recorded in the recording layer.

[0118] The wavelength region of the object reflected light, reproduced light and reference light is an arbitrary region according to their respective uses, and can be a visible light region or an ultraviolet light region. Among them, as more suitable light, for example, lasers with excellent monochromaticity and directivity can be cited, such as: solid-state lasers such as ruby, glass, Nd-YAG, Nd-YVO4; diode lasers such as GaAs, InGaAs, GaN; gas lasers such as helium-neon, argon, krypton, excimer, CO2; pigment lasers with pigments, etc.

[0119] There is no limitation on the irradiation amount of the object reflected light, reproduced light and reference light, and any irradiation amount is sufficient as long as it is within the range capable of recording and reproducing. However, when the irradiation amount is extremely small, the chemical change of the polymerizable monomer is too insufficient, and the heat resistance and mechanical properties of the recording layer may not be fully manifested. On the contrary, when the irradiation amount is extremely large, the components of the recording layer (components of the composition for holographic image recording medium of the present invention) may deteriorate. Therefore, the object reflected light, reproduced light and reference light are usually 0.1 J / cm2 depending on the composition of the composition for holographic image recording medium of the present invention used to form the recording layer, or the type and compounding amount of the photopolymerization initiator. 2 Above 20J / cm 2 Irradiation was performed within the following range.

[0120] Holographic image recording methods include polarization collinear holography, reference light incident angle multiplexed holography, etc. When the holographic image recording medium of the present invention is used as a recording medium, any recording method can provide good recording quality.

[0121] <Application of light guide plates for AR glasses> The hologram recording medium of the present invention performs volume hologram recording in the same manner as in the above-mentioned large-capacity storage application.

[0122] For the volume holographic image recorded in the recording layer, a predetermined reproduction light is irradiated to the recording layer. The irradiated reproduction light is diffracted according to the interference fringes. At this time, even if the wavelength of the reproduction light is inconsistent with the wavelength of the recording light, diffraction will occur as long as the interference fringes and the Bragg condition are satisfied. Therefore, as long as the corresponding interference fringes are recorded according to the wavelength and incident angle of the reproduction light that is desired to be diffracted, the reproduction light in a wider wavelength range can also be diffracted, which can broaden the display color gamut of the AR glass.

[0123] If the corresponding interference fringes are recorded according to the wavelength and diffraction angle of the reproduced light, the reproduced light incident from the outside of the holographic image recording medium can be transmitted to the inside of the holographic image recording medium, or the reproduced light transmitted inside the holographic image recording medium can be reflected, split, amplified, or reduced, or the reproduced light transmitted inside the holographic image recording medium can be emitted to the outside of the holographic image recording medium, thereby widening the viewing angle of the AR glass.

[0124] The wavelength region of the object reflected light and the reproduced light may be any region according to their respective uses, and may be a visible light region or an ultraviolet light region. Among them, as a more suitable light, the above-mentioned laser etc. can be cited. As the reproduced light, it is not limited to the laser etc., and as a more suitable reproduced light, display devices such as a liquid crystal display (LCD) or an organic light-emitting diode (OLED) can also be cited.

[0125] There is no limitation on the irradiation amount of the object reflected light, reproduced light and reference light, and any irradiation amount is acceptable as long as it is within the range that allows recording and reproduction. However, when the irradiation amount is extremely small, the chemical change of the polymerizable monomer is too insufficient, and the heat resistance and mechanical properties of the recording layer may not be fully manifested. On the contrary, when the irradiation amount is extremely large, the components of the recording layer (components of the composition for holographic image recording medium of the present invention) may deteriorate. Therefore, the object reflected light, reproduced light and reference light are usually 0.1 J / cm2 depending on the composition of the composition for holographic image recording medium of the present invention used to form the recording layer, or the type and compounding amount of the photopolymerization initiator. 2 Above 20J / cm 2 Irradiation was performed within the following range. [Example]

[0126] Hereinafter, the present invention will be described in further detail based on examples. The present invention is not limited to the following examples unless it deviates from the gist thereof.

[0127] [Raw materials used] The composition raw materials used in Examples, Comparative Examples and Reference Examples are as follows.

[0128] Component (a): Compound having an isocyanate group DURANATE TM TSS-100: Hexamethylene diisocyanate polyisocyanate (NCO 17.8%) (manufactured by Asahi Kasei Corporation) DURANATE TM A201H: Hexamethylene diisocyanate polyisocyanate (NCO 17.1%) (manufactured by Asahi Kasei Corporation) DURANATE TM TUL-100: Hexamethylene diisocyanate polyisocyanate (NCO 2 3.2%) (manufactured by Asahi Kasei Corporation) · Tolonate XFLO100: Hexamethylene diisocyanate-based polyisocyanate (NCO 12.1%) (manufactured by Vencorex) Takenate 600: 1,3-bis(isocyanatemethyl)cyclohexane (NCO 43.3%) (Made by Mitsui Chemicals)

[0129] The components contained in these compounds having an isocyanate group are represented by the following formula: In the following formula, the structural part represented by the above formula (I) contained in the circled part is an allophanate bond unit.

[0130] [Chemical formula 2]

[0131] Component (b): Compound having an isocyanate-reactive functional group PCL-204HGT: Polycaprolactone diol (molecular weight 400) (manufactured by Daicel Corporation) PCL-205U: Polycaprolactone diol (molecular weight 530) (manufactured by Daicel Corporation) ·PCL-305: Polycaprolactone triol (molecular weight 550) (manufactured by Daicellul Corporation)

[0132] Component (c): polymerizable monomer HLM201: 2-[[2,2-bis(4-dibenzothienylthiomethyl)-3-(4-dibenzothienylthio)propoxy]carbonylamino]ethyl acrylate (molecular weight 872) HLM303: 2-[[2,2-bis[(2-dibenzothiophen-4-ylphenyl) methyl]-3-(1,3-benzothiazol-2-ylmethyl) propoxy] carbonylamino]ethyl acrylate (molecular weight 975)

[0133] Component (d): Photopolymerization initiator HLI02: 1-(9-ethyl-6-cyclohexanoyl-9H-carbazole-3-yl)-1-(O-acetoximo)glutaric acid methyl ester (molecular weight 505)

[0134] Component (e): a compound having an isocyanate-reactive functional group and a nitroxyl radical · 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL): manufactured by Tokyo Chemical Industry Co., Ltd.

[0135] Component (f): Curing catalyst Bismuth tris(2-ethylhexanoate)octanoate solution (active ingredient content 56% by weight)

[0136] [Example 1] 0.8541 g of polymerizable monomer HLM303, 0.0274 g of photopolymerization initiator HLI02, and 0.0103 g of TEMPOL were dissolved in DURANATE TM TSS-100: 0.8470g with DURANATE TM A201H: 1.9764 g, PCL-204HGT: 0.7618 g and PCL-305: 1.4148 g were mixed therein, and 0.0005 g of an octanoic acid solution of bismuth tri(2-ethylhexanoate) was dissolved therein, and the mixture was stirred and mixed.

[0137] The mixed solution was poured onto a glass slide with 0.5 mm thick spacers placed at two opposing edge portions, and a glass slide was placed on top of it. After the periphery was fixed by a clamp, it was heated at 80° C. for 24 hours to prepare a sample for evaluating the composition for holographic image recording medium. The sample for evaluation had a recording layer with a thickness of 0.5 mm formed between the glass slides as covers.

[0138] [Example 2] 0.6306 g of polymerizable monomer HLM201, 0.0227 g of photopolymerization initiator HLI02, and 0.0085 g of TEMPOL were dissolved in DURANATE TM TSS-100: 1.7661 g and Tolonate XFLO100: 1.1774 g were added, and PCL-205U: 0.2057 g and PCL-305: 1.8509 g were mixed therein with stirring. Using the mixed solution, a sample for evaluation was prepared in the same manner as in Example 1.

[0139] [Comparative Example 1] 0.8727 g of polymerizable monomer HLM303, 0.0274 g of photopolymerization initiator HLI02, and 0.0103 g of TEMPOL were dissolved in 2.5365 g of DURANATETM TSS-100, 1.6013 g of PCL-205U and 0.8622 g of PCL-305 were mixed therein, and 0.0002 g of bismuth tri(2-ethylhexanoate) octanoate solution was dissolved therein, and the mixture was stirred and mixed. Using the mixed solution, a sample for evaluation was prepared in the same manner as in Example 1.

[0140] [Comparative Example 2] 0.7697 g of polymerizable monomer HLM303, 0.0242 g of photopolymerization initiator HLI02, and 0.0091 g of TEMPOL were dissolved in DURANATE TM TSS-100: 2.1080 g and Takenate 600: 0.3720 g were added, PCL-204HGT: 2.2680 g and PCL-305: 0.2520 g were mixed therein, and 0.0002 g of bismuth tri(2-ethylhexanoate) octanoate solution was dissolved therein, and the mixture was stirred and mixed. Using the mixed solution, a sample for evaluation was prepared in the same manner as in Example 1.

[0141] [Comparative Example 3] 0.6306 g of polymerizable monomer HLM201, 0.0227 g of photopolymerization initiator HLI02, and 0.0085 g of TEMPOL were dissolved in 2.3419 g of DURANATETM TUL-100, 2.1264 g of PCL-204HGT and 0.5316 g of PCL-205U were dissolved therein, stirred and mixed, and 0.0001 g of bismuth tri(2-ethylhexanoate) octanoate solution was dissolved therein, stirred and mixed. Using the mixed solution, a sample for evaluation was prepared in the same manner as in Example 1.

[0142] [Calculation of the amount of allophanate bond units] The amount (mol / g) of the allophanate bond unit in the compound having an isocyanate group as the component (a) used in Examples and Comparative Examples was calculated according to the procedure described below. DURANATE TM A201H and Tolonate XFLO100 are difunctional isocyanate compounds having an allophanate bond unit, and the amount of allophanate bond unit present (mol / g) was determined from the NCO value using the following formula. NCO value / (42×number of isocyanate groups×100)

[0143] Due to DURANATE TM TSS-100 is a mixture of difunctional or trifunctional isocyanate compounds, so it cannot be determined by calculation based on the NCO value. Therefore, the allophanate bond unit amount (mol / g) was calculated according to the procedure described below. DURANATE TM Add benzylamine: 10 mg / 1 mL (acetonitrile) to TSS-100: 5 mg / 1 mL (acetonitrile) and react at room temperature for 30 minutes. Add DMF (Dimethylformamide) (3 mL) to dissolve the precipitated components to obtain a sample, which is analyzed by LC / MS (Liquid Chromatograph Mass Spectrometer). The conditions of LC / MS are shown in Table 1 below. From the obtained spectrum, the amount of allophanate bond units present (mol / g) is determined based on the ratio of the peak area of ​​all components to the peak area of ​​the structure containing the allophanate bond unit.

[0144] [Table 1]

[0145] DURANATE TM TUL-100 and Takenate 600 are isocyanate compounds that do not contain an allophanate bond unit.

[0146] Based on the amount of allophanate bond units (mol / g) of each isocyanate compound obtained by the above calculation, the amount of allophanate bond units (mol / g) was calculated relative to the total weight of component (a) and component (b) of the composition for holographic image recording medium prepared in each Example and Comparative Example. The results are shown in Table 1.

[0147] [Holographic image recording and evaluation method] Using the samples for evaluating the hologram recording medium compositions prepared in the Examples and Comparative Examples, hologram recording and the hologram recording performance of the hologram recording medium were evaluated according to the procedure described below. For holographic image recording, a semiconductor laser with a wavelength of 405nm is used, and the exposure power density of each beam is 10mW / cm 2 Under the conditions, use Figure 1 The exposure apparatus shown performs two-beam plane wave holographic image recording. The following is a detailed description.

[0148] (Holographic image recording device) Figure 1This is a diagram showing the outline of a device for transmissive holographic image recording. Figure 2 This is a diagram showing the outline of a device for recording a reflective hologram.

[0149] Figure 1 and Figure 2 In the figure, S is a sample of the holographic image recording medium. M1, M2 and M3 all represent reflectors. CS is an exposure time control shutter. BS is a beam shutter. PBS is a polarization beam splitter. LED is a light source for post-exposure (an LED with a central wavelength of 405 nm manufactured by THORLAB). LD represents a laser light source for recording light that emits light of a wavelength of 405 nm (a single-mode laser manufactured by TOPTICA Photonics that can obtain light of a wavelength near 405 nm). PD1 and PD2 represent photodetectors.

[0150] <Projection type holographic image recording exposure> In the projection type holographic image recording exposure, the light of wavelength 405nm emitted from the LD is split by the PBS, and these split lights are regarded as object reflected light (M1 side) and reference light (M2 side), and are irradiated crosswise on the recording surface in such a way that the angle formed by the two light beams becomes 59.3°. At this time, the bisector (hereinafter referred to as the optical axis) of the angle formed by the two light beams is made perpendicular to the recording surface of the recording layer of the holographic image recording medium S, and the vibration plane of the electric field vector of the two light beams obtained after the split is further made perpendicular to the plane including the two intersecting light beams. The sample rotation angle in the above case was set to 0°, and the sample rotation angle was changed in units of 0.2° within the range of -18° to +18°, while multiple recording exposure was performed 181 times on the same part. At this time, in order to make the amount of polymerizable monomer and photopolymerization initiator consumed in recording equal, in all examples and comparative examples, the total recording energy was 2 J / cm 2 The exposure is recorded in the same way.

[0151] <Reflective holographic image recording exposure> In the reflective holographic image recording exposure, the light of wavelength 405nm emitted from the LD is split by the PBS, and these split lights are regarded as object reflected light (M1-M3 side) and reference light (M2 side), and are cross-irradiated on the recording surface in such a way that the angle formed by the two light beams becomes 127°. The sample rotation angle 0° is the same as that of the transmission type holographic image recording exposure device. While changing the orientation angle of the holographic image recording medium S in the range of -24° to +29, 161 multiple recording exposures are performed on the same part. At this time, in order to make the amount of polymerizable monomer and photopolymerization initiator consumed by recording equal, in all embodiments and comparative examples, the total recording energy is 2J / cm 2The exposure is recorded in the same way.

[0152] <Post-exposure> After multiple recording exposures, the rotation angle was returned to 0°, and after waiting for 120 seconds for signal generation in the dark state, the exposure was performed at 4 J / cm 2 After irradiation, the record is fixed by using the light source LED for exposure.

[0153] <Holographic image recording and reproduction> closure Figure 1 and Figure 2 The light beam shutter BS on the object reflected light side illuminates the reference light on the reflector M2 side to reproduce the recorded holographic image. The light intensity detected by PD1 is taken as the diffracted light Idi, and the light intensity detected by PD2 is taken as the transmitted light I ti The diffraction efficiency ηi of each light diffracted from each interference pattern for multiple recording is calculated by the following formula (1). The transmission type cumulative Δn is calculated by the following formula (2) and formula (3). T and reflective accumulation Δn R .

[0154] [Number 1]

[0155] Based on these measured values, calculate "(Δn T -Δn R ) / Δn R ×100”, compare the difference between the transmission type Δn and the reflection type Δn relative to the reflection type Δn R , which is used as an indicator of the stability of recording performance that is independent of the grating pitch.

[0156] The hologram recording media produced in Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated by the above method. The results are shown in Table 2 below.

[0157] [Table 2]

[0158] According to Table 2, the following can be clearly seen. In Examples 1 and 2, the amount of allophanate bond units present is 6.5×10 -4 mol / g or more, it is known that the medium contains a sufficient amount of allophanate bond units. T -Δn R ) / Δn R The value of ×100 is 10% or less, indicating that the difference between the transmission type Δn and the reflection type Δn is sufficiently small, that is, the recording performance stability independent of the grating pitch is excellent. In Comparative Examples 1 to 3, the amount of allophanate bond units present is less than 6.5×10 -4 mol / g, or the allophanate bond unit does not exist, it can be known that the medium does not contain a sufficient amount of allophanate bond units. T -Δn R ) / Δn R The value of ×100 is 15% or more, indicating that the difference between the transmission type Δn and the reflection type Δn is large, that is, the stability of the recording performance is poor depending on the grating pitch.

[0159] Although the present invention has been described in detail using specific embodiments, it is apparent that various modifications can be made by one skilled in the art without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2022-106253 filed on June 30, 2022, and the entirety of the patent application is hereby cited and used.

Claims

1. A composition for a holographic image recording medium, characterized in that: The composition comprises the following components a to d, wherein the amount of allophanate bond units contained in component a is 6.5×10 -4 mol / g or above; Component a: Compound having an isocyanate group Component b: Compound having an isocyanate-reactive functional group Component c: polymerizable monomer Component d: photopolymerization initiator.

2. The composition for holographic image recording medium according to claim 1, wherein The polymerizable monomer of component c is a (meth)acrylic acid monomer.

3. The composition for holographic image recording medium according to claim 1, wherein The molecular weight of the polymerizable monomer of component c is 300 or more.

4. The composition for holographic image recording medium according to claim 1, wherein The content of the component c in the composition is 0.1% by weight to 80% by weight, and the content of the component d is 0.1% by weight to 20% by weight relative to the component c.

5. The composition for holographic image recording medium according to claim 1, wherein Further comprising the following component e; Component e: a compound having a nitroxyl free radical.

6. The composition for holographic image recording medium according to claim 5, wherein The component e is a compound having an isocyanate-reactive functional group and a nitroxyl free radical.

7. The composition for holographic image recording medium according to claim 6, wherein The component e is 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl.

8. The composition for holographic image recording medium according to claim 5, wherein The molar ratio of the component e to the component d in the composition, that is, component e / component d, is 0.1 or more and 10 or less.

9. The composition for holographic image recording medium according to claim 1, wherein The total content of the component a and the component b in the composition is 0.1% by weight or more and 99.9% by weight or less, and the ratio of the number of isocyanate-reactive functional groups contained in the component b to the number of isocyanate groups contained in the component a is 0.1 or more and 10.0 or less.

10. The composition for holographic image recording medium according to claim 1, wherein Further comprising the following component f; Component f: curing catalyst. 11 . A cured product for a hologram recording medium, which is obtained by curing the composition for a hologram recording medium according to claim 1 .

12. A laminate for a holographic image recording medium, wherein: A hologram recording medium having a recording layer formed of the cured product according to claim 11 and a support. 13 . A hologram recording medium, which is obtained by exposing the cured product for a hologram recording medium according to claim 11 or the laminate for a hologram recording medium according to claim 12 to light. The holographic image recording medium according to claim 13 , which is a light guide plate for AR glasses.

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