Method for manufacturing optical element

Abstract

Provided is a method for manufacturing an optical element, in which a holographic image recording medium having a recording layer containing a polymerizable compound and a photopolymerization initiator is subjected to multiple recording exposure of a holographic image on the basis of formula (1) under the condition that the average exposure intensity is 6 mW / cm2 or more. # imgabs0 # (In formula (1), ETi is a single exposure time and represents an exposure time (second) for each multiple recording exposure. EPWi is the exposure light intensity and represents the total light intensity (mW / cm2) of the reference light and the object light. EITi-1 is an exposure interval time and represents the time (second) between one recording exposure and one recording exposure in multiple recording exposures. M is a natural number and represents a total multiple number; wherein, when i = 1, EITi-1 is regarded as zero).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical element by performing multiple recording exposure of a holographic image on a holographic image 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 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 other uses of holographic image recording media, research is being conducted on the application of holographic image recording media to optical elements such as AR (Augmented Reality) glass light guide plates. In the case of AR glass (AR glasses), the optical element used for holographic image recording on the light guide plate is 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 classified into several types according to which optical properties are changed. Volumetric holographic image recording media, which record by creating a refractive index difference in a recording layer having a certain thickness or more, are considered to be useful for AR glass light guide plate applications 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 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 is used as the recording layer (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 object light 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 sides, forming a concentration distribution of the polymerizable compound or its polymer 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 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 and the object light of the recording exposure 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 the "total multiple number". Therefore, the multiple recording exposure in this case does not include offset multiple recording exposure such as recording exposure at a position that is not the same position but is recorded at a slightly offset position.

[0008] On the other hand, only the reproduced light is used for data reproduction, and the irradiated reproduced light diffracts according to the interference pattern. At this time, even if the wavelength of the reproduced light is inconsistent with the wavelength of the recorded light, diffraction will occur as long as the interference pattern and the Bragg condition are satisfied. Therefore, as long as the corresponding interference pattern is recorded according to the wavelength and incident angle of the reproduced light that is desired to be diffracted, diffraction can also be caused for the reproduced light in a wider wavelength region. For example, the display color gamut can be widened in AR glass. Here, the value obtained by dividing the intensity of the diffracted light by the intensity of the reproduced light is called the "diffraction efficiency". In AR glass, the diffraction efficiency is related to the brightness of the displayed AR layer.

[0009] However, if multiple recording exposure is performed to change the incident angle of the recording light relative to the holographic image recording medium for recording under the condition of high diffraction efficiency and a large total multiple number, an unnecessary diffraction phenomenon called "holographic image scattering" may sometimes occur. It is known that in this case, due to inappropriate multiple recording exposure, extremely strong holographic image scattering occurs (Patent Document 5). If the holographic image scattering is strong, the reproduced light and the diffracted light will be scattered, causing a significant decrease in diffraction efficiency. Not only that, noise light will be superimposed on the AR image. According to the research of the inventors, it is known that when Δn is greater than 0.02, the holographic image scattering becomes particularly strong. [Prior art literature] [Patent Document]

[0010] 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 Patent Document 5: Japanese Patent Application Publication No. 2019-053127 Summary of the invention [Problems to be Solved by the Invention]

[0011] An object of the present invention is to provide an optical element in which scattering of a holographic image is sufficiently small when multiple recording exposure is performed. [Technical means to solve the problem]

[0012] The present inventors have found that it is possible to produce an optical element in which hologram scattering is sufficiently small by performing multiple recording exposures so as to have a specific average exposure intensity or more.

[0013] That is, the gist of the present invention is as follows.

[0014] [1] A method for producing an optical element, characterized in that an average exposure intensity of 6 mW / cm2 based on the following formula (1) is applied to a holographic image recording medium having a recording layer containing a polymerizable compound and a photopolymerization initiator. 2 Multiple recording exposures of hologram images under the above conditions.

[0015] [Number 1]

[0016] (In formula (1), ET i EPW is the single exposure time, which indicates the exposure time (in seconds) of each multiple recording exposure. i is the exposure light intensity, which represents the total light intensity of the reference light and the object light (mW / cm 2 ). EIT i-1 is the exposure interval time, which indicates the time (in seconds) between one recording exposure and another recording exposure in multiple recording exposure. m is a natural number, which indicates the total multiple number. When i=1, EIT i-1 treated as zero).

[0017] [2] The method for manufacturing an optical element according to [1], wherein Δn of the hologram recording medium subjected to multiple recording exposure is 0.02 or more.

[0018] [3] The method for producing an optical element according to [1] or [2], wherein the recording layer has a thickness of 0.1 mm or more.

[0019] [4] The method for producing an optical element according to any one of [1] to [3], wherein the EPW of the formula (1) i 10mW / cm 2 above.

[0020] [5] The method for producing an optical element according to any one of [1] to [4], wherein m in the formula (1) is 100 or more.

[0021] [6] The method for producing an optical element according to any one of [1] to [5], wherein the EIT of the formula (1) i-1 More than 0.2 seconds. [Effects of the Invention]

[0022] According to the present invention, it is possible to manufacture an optical element in which scattering of a holographic image is sufficiently small when multiple recording exposure is performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] [ Figure 1 ] is a schematic diagram showing an example of a holographic image recording device. [ Figure 2 ] is a schematic diagram showing an example of a device for measuring the scattering intensity of a holographic image.

Explanation of symbols

[0024] Hereinafter, an embodiment of the method for producing an optical element of the present invention will be described in detail. The following description is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents unless it deviates from the gist of the present invention.

[0025] (Method for manufacturing optical element of the present invention) The present invention relates to a method for manufacturing an optical element, which manufactures the optical element by performing multiple recording exposure of interference patterns generated by reference light and object light on a recording layer of a holographic image recording medium.

[0026] The multiple recording exposure can be performed as follows, namely, a holographic image recording medium (hereinafter sometimes referred to as "the medium") having a recording layer containing a polymerizable compound and a photopolymerization initiator is rotated based on predetermined conditions, for example, by changing the incident angles of reference light and object light, and the interference patterns based on each incident angle are repeatedly recorded and exposed at the same position. In the present invention, the average exposure intensity based on the following formula (1) is 6 mW / cm 2 Perform multiple recording exposures under the above conditions.

[0027] [Number 2]

[0028] (In formula (1), ET i EPW is the single exposure time, which indicates the exposure time (in seconds) of each multiple recording exposure. i is the exposure light intensity, which represents the total light intensity of the reference light and the object light (mW / cm 2 ). EIT i-1 is the exposure interval time, which indicates the time (in seconds) between one recording exposure and another recording exposure in the multiple recording exposure. m is a natural number, which indicates the total multiple number. When i=1, EIT i-1 treated as zero).

[0029] In the present invention, “recording exposure” refers to the exposure with a total of 5 mW / cm2 of reference light and object light. 2 The recording medium is exposed at the above exposure intensity.

[0030] In the present invention, "pretreatment exposure" is used to deactivate the polymerization inhibitor or oxygen contained in the recording layer of the medium, and therefore refers to exposure performed in such a way that the reaction waiting time between the end of pretreatment exposure and the start of multiple recording exposure is 4 seconds or more.

[0031] In the present invention, "post-exposure" means exposure performed at an interval of 4 seconds or more after the end of the multiple recording exposure in order to sufficiently wait for the reaction of the last recording of the multiple recording exposure.

[0032] In the present invention, reference light refers to light used as a reference when recording an interference pattern on a medium, and is light that is irradiated onto the recording layer while overlapping with object light when exposing the recording layer of the medium. In the present invention, object light refers to light that irradiates the recording layer of a medium according to the wavelength and diffraction of reproduction light required as an optical element used in AR glass, etc., so as to record a corresponding interference pattern hologram in the medium through interference with reference light.

[0033] As the light source that can be used for recording exposure in the present invention, it can be arbitrarily selected within the absorption wavelength region of the photopolymerization initiator in the recording layer of the medium. As particularly preferred light sources, 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.

[0034] The wavelength of the recording exposure light in the present invention can be arbitrarily selected from the wavelength range from the ultraviolet region to the visible region as long as it is within the absorption wavelength region of the photopolymerization initiator in the recording layer. The wavelength of the recording exposure light is preferably 300 nm or more, more preferably 350 nm or more, and preferably 600 nm or less, more preferably 450 nm or less.

[0035] In the present invention, the average exposure intensity refers to the average exposure intensity under the total number of multiple exposures of the holographic image multiple recording obtained by the above formula (1). The smaller the average exposure intensity, the greater the scattering intensity of the holographic image. Therefore, the average exposure intensity is set to 6mW / cm 2 Above, preferably 7mW / cm 2 More preferably 8mW / cm 2 On the other hand, if the average exposure intensity is too high, it is difficult to control the device operation. Therefore, it is not suitable for stable manufacturing. Therefore, the average exposure intensity is preferably 90mW / cm 2 Below, more preferably 70mW / cm 2 Below, more preferably 50 mW / cm 2 the following.

[0036] In formula (1), the single exposure time ET is i The exposure time (in seconds) of each exposure in multiple recordings. Single exposure time ET i It can be selected appropriately. Single exposure time ET i The single exposure time ET does not need to be the same in all the multiple records, and may be different. For example, the single exposure time ET may be set to ET based on the prediction of the residual amount of the polymerizable compound consumed by the photopolymerization reaction and the photopolymerization initiator. i Increases in an exponential form. Single exposure time ET i Although not particularly limited, the single exposure time ET is set to be 1 / 2 of the exposure time ET in order to allow for more accurate recording exposure.i Preferably 3×10 -3 seconds or more, more preferably 2×10 -2 On the other hand, if the exposure time ET is recorded i If the exposure time is too long, the air turbulence during exposure will cause the interference of light to deteriorate, which tends to inhibit the recording of holographic images. i It is preferably 100 seconds or less, and more preferably 50 seconds or less.

[0037] In formula (1), the exposure light intensity EPW i It is the total value of the object light and the reference light used to record the exposure. If the exposure light intensity EPWi is low, the single exposure time ETi for irradiating sufficient exposure energy becomes longer. Therefore, considering the manufacturing yield of optical elements, the exposure light intensity EPW i Preferably 10 mW / cm 2 More preferably, 20 mW / cm 2 More preferably, 30 mW / cm 2 On the other hand, if the exposure light intensity EPW i If it is too large, the control problem caused by the fluctuation of light source intensity will make it difficult to perform stable manufacturing. i Preferably 1W / cm 2 Below, more preferably 500mW / cm 2 In consideration of forming interference fringes suitable for recording, the ratio of the light intensities of the object light and the reference light is usually 1:1, but is not particularly limited and may be appropriately changed in the multiple recording exposure.

[0038] In formula (1), the exposure interval time EIT is i-1 It refers to the time between one recording exposure and another recording exposure (when i=1, EIT i-1 Exposure interval time EIT i-1 It can be appropriately changed in multiple recording exposure, but if it is too short, the vibration of the device performing multiple recording exposure will not have enough static time, the interference fringes cannot be properly irradiated on the medium, and the diffraction efficiency cannot be recorded. Therefore, the exposure interval time EIT i-1 It is preferably 0.2 seconds or longer, and more preferably 0.3 seconds or longer. i-1 If the exposure interval EIT is longer, the average exposure intensity will be smaller and the scattering intensity of the holographic image will be worse. i-1 It is preferably 2 seconds or less, more preferably 1.5 seconds or less, and even more preferably 1 second or less.

[0039] When the total multiplex number m of the multiple recording exposure is small, it is difficult to obtain an AR image with a wide display color gamut from the obtained optical element, which is not suitable for practical use. Therefore, the total multiplex number m is preferably 100 or more, and more preferably 150 or more. On the other hand, the larger the total multiplex number m, the wider the display color gamut as described above, and the higher the color reproduction of the AR image, but the time spent on the multiple recording exposure becomes longer, so there is a tendency for the manufacturing efficiency of the optical element to decrease. Therefore, the total multiplex number m is preferably 600 or less, and more preferably 400 or less.

[0040] In the present invention, when controlling the exposure time, the recording exposure time can be controlled by using a shutter that physically blocks light or a liquid crystal shutter that utilizes light-dark switching of liquid crystal.

[0041] When manufacturing an optical element according to the present invention, in order to prevent exposure blocking, the medium before multiple recording exposure may be subjected to pre-treatment exposure to inactivate a polymerization inhibitor or oxygen contained in the recording layer of the medium.

[0042] When an optical element is manufactured according to the present invention, in order to fix the interference pattern to the optical element, the medium after multiple recording exposure may be post-exposed to stabilize the unreacted polymerizable compound or photopolymerization initiator in the recording layer.

[0043] The light source used for the pre-exposure or post-exposure includes LED (Light-Emitting Diode), UV (Ultraviolet) lamp, xenon lamp, mercury lamp, etc. The light source can be arbitrarily selected as long as it can irradiate light in the absorption wavelength region of the photopolymerization initiator in the recording layer, and the same laser as that used for the recording exposure can also be used.

[0044] The diffraction efficiency of the optical element produced by the present invention (hereinafter, sometimes referred to as "optical element of the present invention") can be obtained by irradiating the optical element with reference light as reproduced light.

[0045] The diffraction efficiency η of the holographic image from the i-th recorded exposure is i The diffracted light intensity I can be obtained from the recorded interference pattern di The transmitted light intensity I of the reproduced light ti The diffraction efficiency η is obtained by the relationship between i It is defined by the following formula (2).

[0046] [Number 3]

[0047] For example, when the optical element of the present invention is applied to an AR glass light guide plate, in consideration of the tendency to obtain a bright AR image, the average diffraction efficiency of each holographic image pattern after multiple recording exposure is preferably 0.2 or more, more preferably 0.3 or more, and further preferably 0.4 or more. On the other hand, if the diffraction efficiency of the holographic image pattern is too high, the polymerizable compound consumed in each recording exposure becomes more, and it is more difficult to record with a larger total multiple number. Therefore, the average diffraction efficiency is preferably 0.9 or less, and more preferably 0.8 or less.

[0048] In the present invention, Δn represented by the following formula (3) is used as an evaluation indicator of an optical element that has been subjected to multiple recording exposures. The larger the Δn, the more holographic images can be multiple-recorded with a higher diffraction efficiency. In the case of an AR glass light guide plate, as a value capable of obtaining sufficiently bright and wide-area color display performance, Δn is preferably greater than 0.02, more preferably greater than 0.025, and further preferably greater than 0.03. Regarding Δn, based on the principle of photopolymer materials, a Δn that is too large will instead cause stronger scattering of the medium. Therefore, Δn is preferably less than 0.1, and more preferably less than 0.8.

[0049] [Number 4]

[0050] (where m represents the total multiplicity. i represents the diffraction efficiency of the holographic image image for the i-th multiple recording exposure. λ represents the wavelength of the light source used for multiple recording. θ represents the angle between the object light and the reference light. T represents the thickness of the holographic image recording material).

[0051] (Components of the Medium in the Present Invention) The holographic image recording medium used in the present invention has a recording layer containing at least a polymerizable compound and a photopolymerization initiator. As a composition for forming such a recording layer (hereinafter, also referred to as a "recording layer forming composition"), for example, a photopolymer composed of a combination of an appropriate matrix resin and a polymerizable compound capable of free radical polymerization or cationic polymerization as a polymerizable compound, a photopolymerization initiator that promotes the polymerization of the polymerizable compound, and a polymerization inhibitor as a substance that inhibits the polymerization of the polymerizable compound is appropriately used. The recording layer forming composition may further contain a free radical scavenger.

[0052] The medium in the present invention has a recording layer, and further a support or other layers as required. Generally speaking, the medium has a support, and the recording layer or other layers are stacked on the support to form the medium. However, when the recording layer or other layers have the strength or durability required by the medium, the 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.

[0053] <Regarding the recording layer forming composition> The recording layer of the medium of the present invention is formed by the composition for forming the recording layer described in detail below. Here, regarding the matrix resin, since the composition for forming the recording layer is usually filled between the planar substrates and then polymerized or cross-linked, it exists in the recording layer in the form of a cross-linked network structure. Therefore, it is contained in the composition for forming the recording layer in the form of a matrix resin composition for forming the matrix resin by polymerization or cross-linking. That is, the recording layer forming composition of the present invention may contain a polymerizable compound, a matrix resin forming composition, a photopolymerization initiator and a polymerization inhibitor, and, if necessary, a radical scavenger. Hereinafter, the constituent components of the hologram recording layer forming composition will be described in detail.

[0054] <<About polymerizable compounds>> The polymerizable compound of the present invention refers to a compound that can be polymerized by a photopolymerization initiator described below. The type of polymerizable compound is not particularly limited and can be appropriately selected from known compounds. Examples of polymerizable compounds include cationic polymerizable monomers, anionic polymerizable monomers, free radical polymerizable monomers, etc. These may be used either alone or in combination of two or more.

[0055] Examples of the cationic polymerizable monomer include epoxy compounds, oxetane compounds, oxolane compounds, cyclic acetal compounds, cyclic lactone compounds, thiirane compounds, thietane compounds, vinyl ether compounds, spiroorthoester compounds, ethylenically unsaturated bond compounds, cyclic ether compounds, cyclic thioether compounds, vinyl compounds, and the like. The cationically polymerizable monomers may be used alone or in any combination and ratio.

[0056] 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 may be used alone or in any combination and ratio.

[0057] Examples of the radical polymerizable monomer include compounds having a (meth)acryloyl group, (meth)acrylamides, vinyl esters, vinyl compounds, styrenes, and spiro ring-containing compounds. Any one of the radical polymerizable monomers may be used alone, or two or more of them may be used in any combination and ratio.

[0058] In this specification, a methacrylic group and an acrylic group are generally referred to as a (meth)acrylic group, and a methacryloyl group and an acryloyl group are generally referred to as a (meth)acryloyl group.

[0059] Among the above, from the viewpoint of steric hindrance during radical polymerization, a compound having a (meth)acryloyl group is more preferred.

[0060] Among the polymerizable compounds, compounds having halogen atoms (iodine, chlorine, bromine, etc.) or heteroatoms (nitrogen, sulfur, oxygen, etc.) in the molecule are preferred because they have a higher refractive index. Among the above, compounds having a heterocyclic structure are preferred because they can obtain a higher refractive index.

[0061] <<About matrix resin and matrix resin forming composition>> The matrix resin of the present invention refers to a cured product having a cross-linked network structure formed by bonding through polymerization or cross-linking reaction. The matrix resin forming composition refers to a matrix resin precursor before bonding is formed through polymerization and cross-linking reaction.

[0062] Since the matrix resin has a cross-linked network structure, it moderately suppresses the mobility of the polymerizable compound or photopolymerization initiator, thereby having the function of stably maintaining the polymerizable compound or photopolymerization initiator in the recording layer in a uniformly dispersed state in space. In addition, the matrix resin suppresses the diffusion of the polymer by entanglement with the polymer generated in the recording layer, thereby preventing the recorded information from being erased. Furthermore, since the matrix resin has an elastic modulus higher than that in the liquid state, it has the function of maintaining the physical shape of the recording layer.

[0063] There is no particular limitation on the composition for forming the matrix resin, as long as it can maintain sufficient compatibility with the polymerizable compound or its polymer, and the photopolymerization initiator after forming a bond through a polymerization reaction or a crosslinking reaction. As the composition for forming the matrix resin, preferably, there can be cited a compound having at least two or more functional groups selected from the group consisting of an isocyanate group, a hydroxyl group, a mercapto group, an epoxy group, an amine group, and a carboxyl group in the molecule. These can be used alone or in combination.

[0064] Examples of the embodiment in which these compounds are used alone or in combination to form a chemical bond as a cross-linked network structure include the following (1) to (8). (1) Formation of isocyanurate bonds by reaction of compounds having isocyanate groups (2) Combining a compound having an isocyanate group with a compound having active hydrogen in the molecule, such as a compound containing a hydroxyl group, a mercapto group, an amino group, or a carboxyl group, to form a urethane bond, a thiourethane bond, a urea bond, an amide bond, or the like (3) Combining a compound having a hydroxyl group with a compound having a carboxyl group to form an ester bond (4) Combining a compound having an amine group with a compound having a carboxyl group to form an amide bond (5) Formation of ether bonds by reaction of compounds having epoxy groups (6) Forming an ether bond by combining an epoxy group with a hydroxyl group (7) Forming an amine bond by combining a compound having an epoxy group with a compound having an amine group (8) Combining (1) to (7) to form multiple bonds

[0065] Among them, a combination of a compound having an isocyanate group and a compound having two or more hydroxyl groups as isocyanate-reactive functional groups in the molecule is preferred from the viewpoint of high freedom of choice of matrix resin structure and lack of odor.

[0066] In this case, examples of the compound having an isocyanate group include isocyanic acid, butyl isocyanate, octyl isocyanate, butyl diisocyanate, hexyl diisocyanate (HMDI), isophorone diisocyanate (IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,2,4-trimethylhexamethylene diisocyanate and / or 2,4,4-trimethylhexamethylene diisocyanate, isomers of bis(4,4'-isocyanatocyclohexyl)methane, and any Its mixture with 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, etc.

[0067] Furthermore, isocyanate derivatives having a urethane, urea, carbodiimide, acrylate urea, isocyanurate, allophanate, biuret, oxadiazinedione, uretdione and / or iminooxadiazinedione structure can also be used. These may be used alone or in any combination and in any ratio.

[0068] Examples of compounds having two or more hydroxyl groups as isocyanate-reactive functional groups in the molecule include: glycols such as ethylene glycol, triethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and neopentyl glycol; diols such as butanediol, pentanediol, hexanediol, heptanediol, and 1,4-butanediol; bisphenols; triols such as glycerol, trimethylolpropane, butanetriol, pentanetriol, hexanetriol, and decantriol; compounds obtained by modifying these polyfunctional alcohols with polyethyloxy chains or polypropyloxy 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.

[0069] When forming a matrix resin, for example, a combination of a compound having an epoxy group and a compound having an amine group, since the bond-forming reaction rate of the matrix resin-forming composition is relatively fast, the matrix resin may be formed by allowing the bond-forming reaction to proceed in a short time by leaving it at room temperature. On the other hand, for example, the combination of the matrix resin forming composition with a high degree of freedom of choice of the matrix resin structure, such as the combination of a compound having an isocyanate group and a compound having a hydroxyl group, etc., has a slow reaction rate for forming bonds, and sometimes the formation of bonds is not completed even after being placed at room temperature for several days, and the matrix resin cannot be formed. When using a matrix resin forming composition with a slow reaction rate for forming bonds, the reaction of forming bonds of the matrix resin forming composition can be promoted by heating, as in a common chemical reaction. Therefore, according to the matrix resin forming composition, it is preferred that the recording layer forming composition is filled between the two substrates and then appropriately heated to form the matrix resin.

[0070] <<About free radical scavengers>> In order to accurately fix the interference light intensity pattern in the form of polymer distribution in the holographic image recording medium, the recording layer forming composition may also contain a free radical scavenger. The free radical scavenger preferably has both a functional group for catching free radicals and a reactive group fixed to the matrix resin by a covalent bond. As the functional group for catching free radicals, a stable nitroxyl radical can be cited.

[0071] Examples of the reactive group that is fixed to the matrix resin by a covalent bond include a hydroxyl group, an amine group, an isocyanate group, and a thiol group. Examples of such a radical scavenger include 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPOL), or 3-hydroxy-9-azabicyclo[3.3.1]nonane N-oxyl, 3-hydroxy-8-azabicyclo[3.2.1]octane N-oxyl, 5-hydroxy-2-azatricyclo[3.3.1.1 3,7 ]Decane N-oxyl (5-HO-AZADO).

[0072] The various radical scavengers may be used alone or in combination of two or more in any ratio.

[0073] <<About Curing Catalyst>> By using an appropriate curing catalyst, the bond-forming reaction of the matrix resin-forming composition can be accelerated.

[0074] Examples of such curing catalysts include onium salts such as bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate and bis(4-tert-butylphenyl)iodonium p-toluenesulfonate; catalysts containing Lewis acids as main components such as zinc chloride, tin chloride, ferric chloride, aluminum chloride, and BF3; protonic acids such as hydrochloric acid and phosphoric acid; amines such as trimethylamine, triethylamine, triethylenediamine, dimethylbenzylamine, and diazabicycloundecene; imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-undecylimidazolinium trimellitate; bases such as sodium hydroxide, potassium hydroxide, and potassium carbonate; tin catalysts such as dibutyltin laurate, dioctyltin laurate, and dibutyltin octoate; and bismuth catalysts such as tri(2-ethylhexanoate)bismuth, tribenzoyloxybismuth, bismuth triacetate, tri(dimethyldithiocarbamate)bismuth, and bismuth hydroxide.

[0075] These curing catalysts may be used alone or in any combination and ratio.

[0076] <<About Photopolymerization Initiator>> The photopolymerization initiator of the present invention is a substance that generates cations, anions, and radicals by irradiation with light, and contributes to the polymerization of the polymerizable compound. The type of the photopolymerization initiator is not particularly limited, and can be appropriately selected according to the type of the polymerizable compound.

[0077] 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.

[0078] The cationic photopolymerization initiators exemplified above may be used alone or in combination of two or more in any ratio.

[0079] Any known anionic photopolymerization initiator can be used as the anionic photopolymerization initiator. Examples thereof include amines. Examples of amines include amino group-containing compounds such as dimethylbenzylamine, dimethylaminomethylphenol, and 1,8-diazabicyclo[5.4.0]undecene-7, and their derivatives; imidazole compounds such as imidazole, 2-methylimidazole, and 2-ethyl-4-methylimidazole, and their derivatives.

[0080] The anionic photopolymerization initiators exemplified above may be used alone or in combination of two or more in any ratio.

[0081] 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.

[0082] The above-exemplified photoradical polymerization initiators may be used alone or in combination of two or more in any ratio.

[0083] 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.

[0084] <<About polymerization inhibitor>> The polymerization inhibitor of the present invention refers to a substance that inhibits the polymerization reaction of the above-mentioned polymerizable compound, and can be used as needed. The polymerization inhibitor has the following effects, for example, in the recording layer before holographic image recording, it inhibits the occurrence of unexpected polymerization reactions such as the generation of free radicals by the polymerization initiator or the polymerizable compound due to slight light or heat in the storage environment, thereby improving the storage stability of the medium before holographic image recording.

[0085] The type of polymerization inhibitor is not particularly limited, as long as it can inhibit the polymerization reaction of the polymerizable compound. Specifically, examples include: phosphinates such as sodium phosphate and sodium hypophosphite; thiols such as thioglycolic acid, mercaptopropionic acid, 2-propanethiol, 2-mercaptoethanol, and thiophenol; aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; halogenated hydrocarbons such as trichloroethylene and perchloroethylene; terpenes such as terpinolene, α-terpinene, β-terpinene, and γ-terpinene; 1,4-cyclohexadiene, 1,4-cycloheptadiene, 1,4 - Non-conjugated dienes such as cyclooctadiene, 1,4-heptadiene, 1,4-hexadiene, 2-methyl-1,4-pentadiene, 3,6-nonadiene-1-ol, 9,12-octadecadiene-1-ol; linolenic acid such as linolenic acid, γ-linolenic acid, methyl linolenate, ethyl linolenate, isopropyl linolenate, linolenic anhydride; linoleic acid such as linoleic acid, methyl linoleate, ethyl linoleate, isopropyl linoleate, linoleic anhydride; Eicosapentaenoic acid, eicosapentaenoic acid ethyl ester and other eicosapentaenoic acid derivatives; docosahexaenoic acid, eicosapentaenoic acid ethyl ester and other docosahexaenoic acid derivatives; 2,6-di-tert-butyl-p-cresol, p-methoxyphenol, diphenyl-p-benzoquinone, benzoquinone, hydroquinone, pyrogallol, resorcinol, phenanthrenequinone, 2,5-methylbenzoquinone, benzylaminophenol, p-dihydroxybenzene, 2,4,6-trimethylphenol, butylated hydroxytoluene and other phenol derivatives nitrobenzene derivatives such as o-dinitrobenzene, p-dinitrobenzene, and m-dinitrobenzene; N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, cuproferric reagent, phenothiazine, tannic acid, p-nitrosamine, tetrachlorobenzoquinone, aniline, hindered aniline, iron (III) chloride, copper (II) chloride, triethylamine, hindered amines, nitroxy radicals including 2,2,6,6-tetramethylpiperidinyl 1-oxyl, triphenylmethyl radicals, and oxygen, etc.

[0086] These polymerization inhibitors may be used alone or in any combination and ratio.

[0087] <<About other ingredients>> Other components contained in the recording layer forming composition include solvents, plasticizers, dispersants, leveling agents, defoamers, adhesion promoters, compatibilizers, sensitizers, etc. These components may be used alone or in any combination and ratio.

[0088] <<About the content of each ingredient>> The content of each component in the recording layer forming composition of the present embodiment may be any as long as it does not violate the gist of the present invention. The content of each component is preferably in the following range based on the total mass (100 mass %) of the composition.

[0089] The total content of the matrix resin is usually 0.1% by mass or more, preferably 10% by mass or more, more preferably 35% by mass or more, and usually 99.9% by mass or less, preferably 99% by mass or less, more preferably 98% by mass or less. By making the content of the matrix resin above the lower limit, it is easy to form a recording layer.

[0090] The content of the curing catalyst for promoting the formation of the matrix resin is preferably determined by considering the speed of forming bonds of the matrix-forming component. The content of the curing catalyst is usually 5% by mass or less, preferably 4% by mass or less, more preferably 1% by mass or less, and preferably 0.005% by mass or more.

[0091] The content of the polymerizable compound is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, and usually 80% by mass or less, preferably 50% by mass or less, and more preferably 30% by mass or less. By making the content of the polymerizable compound above the lower limit, sufficient diffraction efficiency can be obtained. By being below the upper limit, the compatibility of the recording layer is ensured.

[0092] The content of the radical scavenger is preferably 0.5 μmol / g or more, more preferably 1 μmol / g or more, and is preferably 100 μmol / g or less, more preferably 50 μmol / g or less, in terms of molar amount per unit mass of the recording layer forming composition. If the content of the free radical scavenger is too little, the efficiency of capturing free radicals becomes low, and there is a tendency that the polymer with a low degree of polymerization diffuses, which is not conducive to the tendency of the signal component becoming more. On the other hand, if the content of the free radical scavenger is too much, the polymerization efficiency of the polymer decreases, and there is a tendency that the signal recording cannot be performed. When two or more free radical scavengers are used in combination, it is preferred that the total amount of the free radical scavengers satisfies the range.

[0093] The content of the photopolymerization initiator is usually 0.1% by mass or more, preferably 0.3% by mass or more, and usually 20% by mass or less, preferably 18% by mass or less, and more preferably 16% by mass or less. By making the content of the photopolymerization initiator above the lower limit, sufficient recording sensitivity can be obtained. In addition, by being below the upper limit, the sensitivity drop caused by the generation of too many free radicals can be suppressed.

[0094] The content of the polymerization inhibitor is usually 0.001% by mass or more, preferably 0.005% by mass or more, and usually 30% by weight or less, preferably 10% by weight or less. By making the content of the polymerization inhibitor within the above range, it is possible to suppress the initiation of an unexpected polymerization reaction by free radicals generated by a little light or heat.

[0095] The content of other components is generally 30% by mass or less, preferably 15% by mass or less, and more preferably 5% by mass or less in total.

[0096] <Regarding the film thickness of the recording layer> The thickness of the recording layer in the present invention is preferably 0.1 mm to 3.0 mm, and more preferably 0.3 mm to 2 mm. If the thickness of the recording layer is within this range, when the holographic image recording medium is multiplexed, there is a tendency that the selectivity of each holographic image becomes higher, and the degree of multiplexed recording can be improved. In addition, there is a tendency that the light transmittance of the recording layer at the wavelength of the recording light can be maintained high, and the entire recording layer can be recorded uniformly in the entire thickness direction, and multiplexed recording with a high S / N ratio can be achieved.

[0097] <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.

[0098] 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.

[0099] As the material of the support, for example, an opaque material may be a metal such as aluminum; a material obtained by coating the transparent support with a metal such as gold, silver, aluminum, or a dielectric such as magnesium fluoride or zirconium oxide.

[0100] The thickness of the support is also not particularly limited, and is usually 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 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 transmission amount of light can be ensured, and the cost increase can be suppressed.

[0101] The surface of the support may also be subjected to a surface treatment. This surface treatment is usually 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.

[0102] Furthermore, surface treatment may be performed for purposes other than improving adhesion. Examples thereof include reflective coating treatment for forming a reflective coating made of a metal such as gold, silver, or aluminum; and 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.

[0103] The support may be disposed only on either the upper side or the lower side of the recording layer of the 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 therethrough. When a medium with a support is provided on one or both sides of the recording layer, a transmissive hologram or a reflective hologram can be recorded. When a support with a reflective property is provided on one side of the recording layer, a reflective hologram can be recorded.

[0104] <Protective layer> The protective layer is 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. 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.

[0105] <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.

[0106] <Anti-reflective film> When the medium of the present invention is constituted in the form of 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 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.

[0107] <Method for producing recording layer forming composition> The method for producing the recording layer forming composition containing the polymerizable compound, the matrix resin and the photopolymerization initiator is not particularly limited, and the mixing order can be appropriately adjusted. In addition, when the recording layer forming composition contains components other than those described above, the components can be mixed in any combination and order.

[0108] When isocyanate (a compound having an isocyanate group) and polyol (a compound having two or more hydroxyl groups in a molecule) are used as the matrix resin, the recording layer forming composition can be obtained, for example, by the following method. However, the present invention is not limited thereto. A polymerizable polymer and a photopolymerization initiator are mixed with all components except isocyanate and a polyurethane curing catalyst to prepare a photoreactive composition (liquid A). On the other hand, an isocyanate and a polyurethane curing catalyst are mixed to prepare a liquid B. Alternatively, all components except isocyanate may be mixed with the polymerizable polymer and the photopolymerization initiator to obtain a photoreactive composition (liquid A).

[0109] It is preferred to dehydrate and deaerate each liquid. If the dehydration and deaeration are insufficient, bubbles will be generated when the holographic image recording medium is produced, and sometimes a uniform recording layer cannot be obtained. When the dehydration and deaeration are performed, heating and decompression can also be performed as long as the components are not damaged.

[0110] The production of the recording layer forming composition by mixing liquid A and liquid B is preferably carried out immediately before forming the hologram recording medium. In this case, a mixing technique according to the previous method can also be used. When liquid A and liquid B are mixed, degassing may be performed as necessary to remove residual gas. Liquid A and liquid B are preferably filtered separately to remove foreign matter and impurities, or mixed and then filtered to remove foreign matter and impurities. More preferably, each liquid is filtered separately.

[0111] An isocyanate functional prepolymer obtained by reacting an excess of an isocyanate having an isocyanate group with a polyol as an isocyanate can be used as a matrix resin. Furthermore, an isocyanate reactive prepolymer obtained by reacting an excess of a polyol having an isocyanate reactive functional group with an isocyanate as a polyol can be used as a matrix resin.

[0112] <Method for producing medium> The method for producing the medium of the present invention is not limited, and can be produced, for example, by coating the recording layer-forming composition on a support in the absence of a solvent to form a recording layer.

[0113] Any method may be used as a coating method for the recording layer forming composition, and specific examples thereof include spray coating, spin coating, bar coating, dipping, air knife coating, roll coating, blade coating, and blade roll coating.

[0114] When forming a recording layer, especially a thick recording layer, the recording layer forming composition may be placed in a mold for molding or the recording layer forming composition may be applied to a release film and then punched out by a mold.

[0115] The recording layer can also be produced by mixing the recording layer forming composition with a solvent or an additive to prepare a coating solution, applying the coating solution to a support and drying to form a recording layer. In this case, any method can be used as a coating method, for example, the same method as described above can be used.

[0116] The solvent used in the coating liquid is not limited. Generally, it is preferred to use a solvent that has sufficient solubility for the components used, can impart good coating properties, and does not penetrate into a support such as a resin substrate. Examples of the solvent 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; highly 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. The solvent may 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.

[0117] When the resin matrix of the recording layer forming composition is thermoplastic, the recording layer can be formed by molding the recording layer forming composition, for example, by injection molding, sheet molding, hot pressing or the like.

[0118] When the resin matrix is ​​a photocurable or thermosetting resin having a relatively low volatile component, the recording layer can be formed by molding the recording layer forming composition using, for example, a reaction injection molding method or a liquid injection molding method. In this case, if the molded body has sufficient thickness, rigidity, strength, etc., the molded body can be used directly as a medium.

[0119] The medium can also be manufactured by the following methods: a method in which a recording layer forming composition that is melted by heat is applied to a support, cooled to solidify it, and a recording layer is formed to manufacture the medium; a method in which a liquid recording layer forming composition is applied to a support, thermally polymerized to solidify it, and a recording layer is formed to manufacture the medium; a method in which a liquid recording layer forming composition is applied to a support, photopolymerized to solidify it, and a recording layer is formed to manufacture the medium.

[0120] The medium thus produced can be in the form of a self-supporting flat plate or disc, which can be used in three-dimensional image display devices or diffractive optical elements and mass storage, among other uses. [Example]

[0121] Hereinafter, the present invention will be described in further detail by way of examples, but the present invention is not limited to the following examples unless it deviates from the gist of the present invention.

[0122] [Raw materials used] The composition raw materials used in Examples and Comparative Examples are as follows.

[0123] (Compound having an isocyanate group) DURANATETM TSS-100: Hexamethylene diisocyanate-based polyisocyanate (NCO 17.6%) (manufactured by Asahi Kasei Corporation) Takenate 600: Aliphatic diisocyanate (manufactured by Mitsui Chemicals, Inc.)

[0124] (Compound having an isocyanate-reactive functional group) PLACCEL PCL-205U: Polycaprolactone diol (molecular weight 530, manufactured by Daicel Corporation) PLACCEL PCL-305: Polycaprolactone triol (molecular weight 550, manufactured by Daicel Corporation) PLACCEL PCL-204HGT: Polycaprolactone diol (molecular weight 400, manufactured by Daicel Corporation)

[0125] (Polymerizable compound) HLM201: 2-[[2,2-bis(4-dibenzothienylthiomethyl)-3-(4-dibenzothienylthio)propoxy]carbonylamino]ethyl acrylate HLM303: 2-[[2,2-bis[(2-dibenzothiophen-4-ylphenyl) methyl]-3-(1,3-benzothiazol-2-ylmethyl) propoxy] carbonylamino]ethyl acrylate

[0126] (Photopolymerization Initiator) HLI02: 1-(9-ethyl-6-cyclohexanoyl-9H-carbazole-3-yl)-1-(O-acetoximo)glutaric acid methyl ester

[0127] (Curing Catalyst) Bismuth tris(2-ethylhexanoate)octanoate solution (active ingredient content 56% by weight)

[0128] (Free Radical Scavenger) TEMPOL: 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0129] [Preparation of TEMPOL masterbatch] DURANATE TM 2.97 g of TSS-100 was dissolved in 0.03 g of TEMPOL, and 0.0003 g of an octanoic acid solution of bismuth tri(2-ethylhexanoate) was dissolved therein, followed by stirring at 45° C. under reduced pressure and reacting for 2 hours.

[0130] [Preparation of recording layer forming composition and production of holographic image recording medium] <Medium 1> 0.7599 g of polymerizable compound HLM101, 0.0304 g of photopolymerization initiator HLI02, and 1.0411 g of TEMPOL masterbatch were dissolved in DURANATE TM TSS-100: 2.8794 g to prepare solution A. Separately, 1.795 g of PLACCEL PCL-205U and 1.795 g of PLACCEL PCL-305 (PLACCEL PCL-205U:PLACCEL PCL-305=50:50 (mass ratio)) were mixed and dissolved in 0.00023 g of bismuth tri(2-ethylhexanoate) octanoate solution to prepare liquid B.

[0131] After deaerating solution A under reduced pressure for 2 hours and deaerating solution B under reduced pressure at 45° C. for 2 hours, 2.5537 g of solution A and 1.9463 g of solution B were stirred and mixed. Next, the mixed solution was poured onto a glass slide with spacers of 0.6 mm thickness placed on the two opposing edge portions, and a glass slide was placed on top of it, and the periphery was fixed with a clamp, and then heated at 80° C. for 24 hours to obtain a medium 1 for evaluation. The evaluation sample had a recording layer of 0.6 mm thickness formed between the glass slides as covers.

[0132] <Medium 2> Takenate 600: 0.5952 g, polymerizable compound HLM303: 1.2315 g, photopolymerization initiator HLI02: 0.0387 g, and TEMPOL masterbatch: 1.4531 g were dissolved in DURANATE TM TSS-100: 1.9341 g to prepare solution A. Separately, 3.6289 g of PLACCEL PCL-204HGT and 0.4032 g of PLACCEL PCL-305 (PLACCEL PCL-204HGT:PLACCEL PCL-305=90:10 (mass ratio)) were mixed and dissolved in 0.00024 g of bismuth tri(2-ethylhexanoate) octanoate solution to prepare liquid B.

[0133] After deaerating solution A under reduced pressure for 2 hours and deaerating solution B under reduced pressure at 45° C. for 2 hours, 3.2829 g of solution A and 2.5202 g of solution B were stirred and mixed. Next, the mixed solution was poured onto two slide glasses with spacers of 0.6 mm thickness placed at the opposite ends, and a slide glass was placed on top of the spacers, and the periphery was fixed with a clamp, and then heated at 80° C. for 24 hours to obtain a medium 2 for evaluation. The evaluation sample had a recording layer of 0.6 mm thickness formed between the slide glasses as a cover.

[0134] [Manufacturing of optical components] <Holographic image recording device> Figure 1 This is a diagram showing the outline of a device for recording a holographic image on a medium. Figure 1 In the figure, S is a sample of the holographic image recording medium (medium 1 or medium 2). M1 and M2 both 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.

[0135] <Holographic image recording exposure> Light of wavelength 405 nm emitted from the recording light laser light source LD is dispersed by a polarization beam splitter PBS, and these split beams are regarded as object light (M1 side) and reference light (M2 side), and are irradiated crosswise on the recording surface in such a manner that the angle formed by the two beams becomes 59.3°. At this time, the bisector (hereinafter referred to as the optical axis) of the angle formed by the two beams is made perpendicular to the recording surface of the recording layer of the holographic image recording medium S, and further, the vibration plane of the electric field vector of the two beams obtained after the division is made perpendicular to the plane containing the two intersecting beams. The above situation was set to 0°, the beam shutter BS was opened, and the direction of the holographic image recording medium S was changed to an angle of 24° while the incident directions of the two beams were fixed. As pre-treatment exposure, the exposure time control shutter CS was opened for 350 milliseconds, and after irradiating the object light and the reference light, the oxygen acting as a free radical quencher was waited for deactivation in a dark state for 10 seconds. Thereafter, multiple recording exposures were performed under the conditions of the average exposure intensity in Table 1 while changing the angle of the recording surface relative to the optical axis in units of 0.2°. At this time, in order to make the amount of the polymerizable compound and the photopolymerization initiator consumed by recording equal, the total exposure energy was set to 2 J / cm in all the examples and comparative examples. 2 .

[0136] <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.

[0137] <Holographic image recording and reproduction> closure Figure 1 The light beam shutter BS is used to reproduce the recorded holographic image using the light on the side of the reflector M2 as the reference light. The light intensity detected by the photodetector PD1 is used as the diffracted light I di , the light intensity detected by the photodetector PD2 is taken as the transmitted light I ti , measure the diffraction efficiency η of the light diffracted from each interference pattern i The value of is calculated from the above equations (2) and (3). At this time, the diffraction caused by the interference pattern during the pre-exposure is also reproduced in the same manner, but is not included in the multiplicity.

[0138] <Measurement of holographic image scattering intensity> Figure 2 Schematic diagram of a device for measuring the scattering intensity of a holographic image. Figure 2S in the above is the holographic image recording medium after the holographic image is recorded and reproduced. G-LD (532nm) is a laser light source for holographic image scattering measurement that can obtain a wavelength of 532nm (JUNO532 single-mode laser manufactured by Showa Optronics). PD1 and PD2 represent photodetectors. The measuring light is incident obliquely at an incident angle of about 5° with respect to the sample S. The incident angle is appropriately adjusted within a range of 5°±1° so that the hologram scattered light enters the photodetector PD2 most strongly. The holographic image scattering intensity is calculated as the ratio of the intensity of the photodetector PD1 to the transmitted light intensity of the photodetector PD2 using the following equation (4): H (%) was used for evaluation. I H =(intensity of PD1 / transmitted light intensity of PD2)×100 (4)

[0139] <Judgment Criteria> Based on the holographic image scattering intensity ratio I H , set the following evaluation criteria. ◎:I H ≤0.15% ○: 0.15%<I H ≤0.25% ×: 0.25%<I H

[0140] <Evaluation Results> In Medium 1 and Medium 2, each parameter corresponding to Formula (1) was set so as to obtain the average exposure time shown in Table 1, and the evaluation results of the hologram scattering intensity and Δn of the optical element obtained by performing multiple recording exposure are shown in Table 1.

[0141] [Table 1]

[0142] According to Examples 1 to 6 and Comparative Example 1, it was confirmed that in the medium 1, the average exposure intensity based on the formula (1) was 6 mW / cm 2 When multiple recording exposures are performed in the above manner, the scattering intensity of the holographic image can be significantly reduced while maintaining a high Δn. When the average exposure time is 8 mW / cm 2 When the value is above 0.1, it is confirmed that the hologram image scattering intensity is further reduced. According to Examples 7 to 9 and Comparative Example 2, it was confirmed that in Medium 2, when the average exposure time was 6 mW / cm 2 When the average exposure time is 8 mW / cm2 When the value is above 0.1, it is confirmed that the hologram image scattering intensity is further reduced. These results show that the method for manufacturing an optical element according to the present invention can record a hologram with a sufficiently low hologram scattering intensity.

[0143] Although the present invention has been described in detail using specific aspects, it is apparent that various modifications can be made by those skilled in the art without departing from the intent and scope of the present invention. This application is based on Japanese Patent Application No. 2022-106251 filed on June 30, 2022, the entirety of which is incorporated herein by reference. [Industrial Applicability]

[0144] The manufacturing method of the optical element of the present invention can be effectively used as a method for widening the display color gamut, maintaining Δn for obtaining bright AR images, and recording holographic images with sufficiently low holographic image scattering intensity, especially in optical elements used in AR glass light guide plates.

Claims

1. A method for manufacturing an optical element, characterized in that: The holographic image recording medium having a recording layer containing a polymerizable compound and a photopolymerization initiator was subjected to an average exposure intensity of 6 mW / cm 2 Multiple recording exposures of holographic images under the above conditions; In formula (1), Et i EPW is the single exposure time, which means the exposure time of each multiple exposure, in seconds; i Exposure light intensity, which represents the total light intensity of reference light and object light, in mW / cm 2 ; EIT i-1 is the exposure interval time, which means the time between one recording exposure and another recording exposure in multiple recording exposures, in seconds; m is a natural number, which means the total multiple number; when i=1, EIT i-1 Treated as zero.

2. The method for manufacturing an optical element according to claim 1, wherein: The Δn of the hologram recording medium subjected to multiple recording exposure is 0.02 or more. 3 . The method for producing an optical element according to claim 1 , wherein the recording layer has a thickness of 0.1 mm or more.

4. The method for manufacturing an optical element according to claim 1 or 2, wherein the EPW of the formula (1) i 10mW / cm 2 above.

5. The method for producing an optical element according to claim 1 or 2, wherein m in the formula (1) is 100 or more.

6. The method for manufacturing an optical element according to claim 1 or 2, wherein the EIT of the formula (1) i-1 More than 0.2 seconds.

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