JP2018141815A - Holographic optical element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means of improving durability of a holographic optical element with a volume hologram recording layer.SOLUTION: A holographic optical element comprises a volume hologram recording layer containing a photopolymer, and at least one adjacent layer adjacent to the volume hologram recording layer and containing resin and an aromatic ester compound having a molecular weight of 180 to 400.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a holographic optical element and a manufacturing method thereof.

  Holographic optical elements having a volume hologram recording layer function as an optical combiner and are applied to optical lenses, display elements, and the like, and the demand is increasing. In particular, a holographic optical element as a display element such as a head-mounted display or a head-up display can be used as a see-through display element because the volume hologram recording layer has high transparency (for example, Patent Document 1).

  With increasing demand and diversification of applications, the required performance for holographic optical elements has increased, and quality items have diversified. In order to obtain a high-quality image element, it is necessary to maintain the quality over a long period of time, in addition to improving the selectivity and diffraction efficiency of reflected light, which are basic characteristics of the hologram layer.

  Patent Document 2 discloses a photosensitive composition excellent in refractive index modulation and a method for producing a volume hologram recording layer using the same. That is, according to Patent Document 2, a photosensitive layer obtained by applying and drying a photosensitive composition containing a polymerizable monomer sandwiched between a pair of transparent supports is subjected to face-to-face exposure (interference exposure) with a coherent light source, A volume hologram recording layer is produced by causing a polymerization reaction in the photosensitive layer in response to an interference wave and forming a diffraction grating composed of regions of a high refractive index and a low refractive index.

JP 2014-215410 A JP-A-6-301322

  However, the holographic optical element described in Patent Document 2 has a problem that the transparent support and the volume hologram recording layer are peeled off during long-term use, the diffraction efficiency is lowered, and the durability as an optical element is lowered. was there.

  Therefore, an object of the present invention is to provide means for improving the durability of a holographic optical element having a volume hologram recording layer.

  The present inventors conducted extensive research. As a result, the present inventors have found that the above problem can be solved by providing at least one adjacent layer containing a resin and an aromatic ester compound having a molecular weight in a specific range so as to be in contact with the volume hologram recording layer, thereby completing the present invention. It came to do.

  That is, the present invention has a volume hologram recording layer containing a photopolymer, and at least one adjacent layer containing a resin and an aromatic ester compound having a molecular weight of 180 to 400 in contact with the volume hologram recording layer. It is a holographic optical element.

  According to the present invention, means for improving the durability of a holographic optical element having a volume hologram recording layer is provided.

It is a cross-sectional schematic diagram which shows the typical structure of a holographic optical element. It is a schematic diagram which shows an example of the exposure apparatus used for holographic exposure.

  Hereinafter, a holographic optical element according to an embodiment of the present invention will be described.

  In the following, a layer containing a polymerizable monomer before holographic exposure (interference exposure) is referred to as a photosensitive layer, and a layer on which a volume hologram is recorded by performing holographic exposure on the photosensitive layer is referred to as a volume hologram recording layer. In addition, a photo-resin composition obtained by irradiating light to a photosensitive composition containing a polymerizable monomer, a photopolymerization initiator, a matrix resin and a precursor thereof, and causing a polymerization reaction (that is, photocured) It is called a polymer.

  The holographic optical element of this embodiment includes a volume hologram recording layer containing a photopolymer, and at least one adjacent layer containing a resin and an aromatic ester compound having a molecular weight of 180 to 400 in contact with the volume hologram recording layer. And a holographic optical element. The holographic optical element of this embodiment having such a configuration has excellent durability that it is difficult to cause separation between the volume hologram recording layer and the adjacent layer over a long period of time, and a high diffraction efficiency can be maintained for a long period of time.

  Although the detailed reason why the above-described effect can be obtained by the holographic optical element of the present embodiment is unknown, the following mechanism is conceivable.

  The reason why the diffraction grating having the high refractive index region and the low refractive index region is formed in the volume hologram recording layer is considered to be due to the following phenomenon occurring in the photosensitive layer. When holographic exposure is performed and polymerization of the polymerizable monomer in the photosensitive layer is promoted in the exposed area, diffusion movement of the polymerizable monomer occurs to minimize the interface between the polymerizable monomer and other components, and further polymerization reaction occurs. Advances. Thereby, in the photosensitive layer, the region of the photopolymer formed by the polymerization reaction and the region of the other component are formed in the same pattern as the interference wave irradiated by the holographic exposure. Then, there is a difference in refractive index between the photopolymer region and the other component region, and a high refractive index region and a low refractive index region corresponding to the interference wave are formed, and a diffraction grating ( Hologram) is formed.

  The diffusion transfer phenomenon of the polymerizable monomer in the vicinity of the photosensitive layer-adjacent layer interface lowers the adhesion between the photosensitive layer and the adjacent layer, and the adhesion between the volume hologram recording layer and the adjacent layer of the resulting holographic optical element. Will be reduced. Further, along with this peeling, the diffraction grating near the above-mentioned interface is destroyed, and the durability of the holographic optical element is deteriorated.

  On the other hand, in the holographic optical element of the present embodiment, the aromatic ester compound having a molecular weight of 180 to 400 contained in the adjacent layer exhibits affinity with the polymerizable monomer in the photosensitive layer due to the aromatic site, and is adjacent to the aromatic layer. Increase adhesion between layer and photosensitive layer. Furthermore, since the aromatic ester compound has a low molecular weight, the aromatic ester compound moves in the adjacent layer so as to follow the diffusion transfer phenomenon of the polymerizable monomer and photopolymer in the photosensitive layer during holographic exposure, and polymerizes. It does not hinder the diffusion transfer phenomenon of the functional monomer or photopolymer and maintains the adhesion between the adjacent layer and the photosensitive layer. Therefore, the completed holographic optical element has a high diffraction efficiency and can maintain the high diffraction efficiency for a long time.

  In addition, the said mechanism is based on assumption and the holographic optical element of this embodiment is not restrict | limited at all by the said mechanism.

  Hereinafter, preferred embodiments will be described in more detail, but the present invention is not limited to the following embodiments.

  In this specification, “X to Y” indicating a range means “X or more and Y or less”. Unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50% RH.

[Overall configuration of holographic optical element]
First, the overall configuration of the holographic optical element of this embodiment will be described.

  FIG. 1 is a schematic cross-sectional view showing a typical configuration of the holographic optical element of the present embodiment. The holographic optical element 10 includes a volume hologram recording layer 11 and a pair of adjacent layers 12. The holographic optical element shown in FIG. 1 is provided with a pair of adjacent layers 12 so as to be in contact with both surfaces of the volume hologram recording layer 11, but the adjacent layer 12 is provided only on one surface of the volume hologram recording layer 11. Form may be sufficient.

[Adjacent layer]
The adjacent layer included in the holographic optical element of the present embodiment includes a resin and an aromatic ester compound having a molecular weight of 180 to 400.

  The adjacent layer having the above configuration may be provided so as to be in contact with both surfaces of the volume hologram recording layer, or may be provided so as to be in contact with only one surface. That is, the holographic optical element of the present embodiment only needs to have at least one adjacent layer containing a resin in contact with the volume hologram recording layer and an aromatic ester compound having a molecular weight of 180 to 400. When adjacent layers are provided on both surfaces of the volume hologram recording layer, the constituent material and thickness of each adjacent layer may be the same or different.

<Resin>
As the resin contained as a base material in the adjacent layer, a known resin having transparency can be used. Specific examples include acrylic resin, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthoate, polyethylene, polypropylene, amorphous polyolefin, cellulose acetate, hydrated cellulose, cellulose nitrate, cycloolefin polymer, polystyrene, polyepoxide, polysulfone, Examples include cellulose acylate, polyamide, polyimide, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl butyral, and polydicyclopentanediene. These resins may be used alone or in combination of two or more.

  Among these, polyethylene terephthalate, cycloolefin polymer, cellulose acylate, and polymethyl methacrylate are preferable, and cellulose acylate is more preferable from the viewpoints of optical characteristics, ease of movement of the aromatic ester compound, and the like.

  Glucose units having a β-1,4 bond constituting cellulose have free hydroxy groups at the 2nd, 3rd and 6th positions. The cellulose acylate is a polymer obtained by acylating part or all of these hydroxy groups with an acyl group. The substitution degree of the acyl group represents the total of the ratio of cellulose esterified at the 2nd, 3rd and 6th positions of the repeating unit. Specifically, the degree of substitution is 1 when the hydroxy groups at the 2-position, 3-position and 6-position of cellulose are each 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of cellulose are 100% esterified, the degree of substitution is 3 at the maximum. The degree of acyl group substitution can be measured according to ASTM-D817-96. The substitution degree of the acyl group is preferably 1.80 to 2.68, and more preferably 2.40 to 2.65, from the viewpoint of the density of the adjacent layer.

  Examples of acyl groups include, for example, acetyl, n-propionyl, isopropionyl, n-butanoyl, isobutanoyl, t-butanoyl, pentanoyl, hexanoyl, heptanoyl, octanoyl, decanoyl, dodecanoyl Group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group, or a fragrance represented by the following general formula (I) Group acyl group and the like.

  In the general formula (I), X represents a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, or octyl group. N represents an integer of 1 to 5, and when n is 2 or more, a plurality of Xs may be connected to each other to form a ring.

  Among these acyl groups, acetyl group, n-propionyl group, n-butanoyl group, t-butanoyl group, dodecanoyl group, octadecanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group, the above general formula ( An aromatic acyl group represented by I) is more preferable, and an acetyl group, an n-propionyl group, an n-butanoyl group, a t-butanoyl group, a benzoyl group, or an aromatic acyl group represented by the above general formula (I) Are more preferable, and an acetyl group is particularly preferable.

  The weight average molecular weight (Mw) of the cellulose acylate is preferably in the range of 75,000 to 280000, more preferably in the range of 100,000 to 240,000, from the viewpoints of ensuring uniformity of optical properties and ensuring productivity and processability. preferable.

  In addition, the weight average molecular weight (Mw) of a cellulose acylate can be measured on the following measurement conditions using a gel permeation chromatography (GPC).

Solvent: Methylene chloride Column: Shodex (registered trademark) K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences Inc.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 samples are used. Thirteen samples are used at approximately equal intervals.

  The content of the resin in the adjacent layer is preferably 70 to 99.5% by mass with respect to the total mass of the adjacent layer.

<Aromatic ester compound>
The adjacent layer of this embodiment contains an aromatic ester compound having a molecular weight of 180 to 400. When the molecular weight of the aromatic ester compound is less than 180, the mechanical strength of the adjacent layer is lowered and the durability is lowered. On the other hand, when it exceeds 400, it becomes difficult for the aromatic ester compound to move in the adjacent layer in conjunction with the diffusion transfer phenomenon of the polymerizable monomer or photopolymer, and the adhesion between the volume hologram recording layer and the adjacent layer decreases. . The molecular weight of the aromatic ester compound in the adjacent layer can be analyzed by mass spectrum after the aromatic ester compound is isolated by liquid chromatography (LC) or high performance liquid chromatography (HPLC).

  As the aromatic ester compound, any compound having an aromatic group and an ester group and having a molecular weight in the above range can be used without particular limitation. Examples of specific compounds include, for example, dimethyl phthalate, dimethyl isophthalate, diethyl phthalate, diethyl isophthalate, dibutyl phthalate, dibutyl isophthalate, dihexyl phthalate, dihexyl isophthalate, butyl benzyl phthalate, butyl benzyl isophthalate, dibenzyl Phthalate, dibenzylisophthalate, dioctylphthalate (bis (2-ethylhexyl) phthalate), dioctylisophthalate (bis (2-ethylhexyl) isophthalate), dimethoxyethyl phthalate, dimethoxyethyl isophthalate, amyl benzoate, hexyl benzoate, 2-ethylhexyl benzoate, butyl 4-hydroxybenzoate, hexyl 4-hydroxybenzoate, 2-ethyl benzoate 4-ethyl benzoate Carboxylic acid ester compounds such as hexyl; octyl diphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, ethylphenyl diphenyl phosphate, di (ethylphenyl) phenyl phosphate, propylphenyl Examples thereof include phosphoric acid ester compounds such as diphenyl phosphate and butyl phenyl diphenyl phosphate; sulfonic acid esters such as methyl p-toluenesulfonate, ethyl p-toluenesulfonate, and butyl p-toluenesulfonate. These aromatic ester compounds can be used singly or in combination of two or more.

  Among these, from the viewpoint of compatibility with the resin contained in the adjacent layer, it is preferably at least one of a carboxylic acid ester compound and a phosphoric acid ester compound, and has an affinity for a polymerizable monomer contained in the photosensitive layer described later. From the viewpoint of properties, octyl diphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, and tricresyl phosphate containing two or more phenyl groups are more preferable.

  The content of the aromatic ester compound in the adjacent layer is preferably 0.05 to 20% by mass, more preferably 0.08 to 15% by mass, based on the total mass of the adjacent layer. More preferably, it is 10 to 10% by mass.

  In addition to the above-mentioned components, the adjacent layer is composed of, for example, an ultraviolet ray inhibitor, an ultraviolet absorber, an antioxidant, a deterioration inhibitor, a light stabilizer, a heat stabilizer, a lubricant, an antistatic agent, a flame retardant, a filler, fine particles, Other components such as an optical property adjusting agent may be included. The addition amount of other components (the total when two or more are added) is preferably 0.1 to 29.5 mass% with respect to the total mass of the adjacent layers.

  The adjacent layer may be in the form of a film or plate, or may be in the form of a substrate that also serves as a prism. In the case of a layered shape, processing by cutting is possible, and there is a convenience that it can be applied to various optical elements.

  In the case where the adjacent layer is layered, the thickness is not particularly limited, but is preferably 10 to 1000 μm, and more preferably 50 to 200 μm.

(Formation method of adjacent layer)
The method for forming the adjacent layer into a layer shape such as a film is not particularly limited, and any conventionally known method such as a melt extrusion method, a solution casting method (solution casting method), a calendar method, or a compression molding method is used. be able to. Among these methods, the melt extrusion method and the solution cast method (solution casting method) are preferable.

  Examples of the melt extrusion method include a method in which a resin, an aromatic ester compound, and other components as necessary are melt-kneaded and then formed into a film by melt extrusion. The kneader used for kneading is not particularly limited. For example, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used. In addition, examples of the melt extrusion method for forming a film include a T-die method and an inflation method. The molding temperature at the time of melt extrusion varies depending on the type of resin and cannot be generally stated, but is preferably 200 to 350 ° C. When forming on a film by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and the film extruded into a film shape is wound to obtain a roll-shaped film. it can. Under the present circumstances, it is also possible to set it as a uniaxial stretching process by adjusting the temperature of a winding roll suitably, and adding extending | stretching to an extrusion direction. It is also possible to add steps such as sequential biaxial stretching and simultaneous biaxial stretching by adding a step of stretching the film in a direction perpendicular to the extrusion direction. Further, in order to stabilize the optical isotropy and mechanical properties of the film, heat treatment (annealing) or the like can be performed after the stretching treatment.

  Moreover, in the solution casting method (solution casting method), a method of casting (casting) after preparing a solution or dispersion (dope) containing a resin, an aromatic ester compound, and other components as necessary, etc. Is mentioned.

  The solvent used in the solution casting method (solution casting method) is not particularly limited. For example, a chlorinated solvent such as chloroform and methylene chloride; an aromatic solvent such as toluene, xylene, benzene, and a mixed solvent thereof. Methanol, ethanol, n-propanol, 2-propanol, n-butanol, sec-butanol, tert-butanol, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2- Alcohol solvents such as propanol and 2,2,3,3,3-pentafluoro-1-propanol; methyl cellosolve Examples include ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), methyl acetate, ethyl acetate, amyl acetate, diethyl ether, nitroethane and the like. It is done. These solvents may be used alone or in combination of two or more. Examples of the apparatus for performing the solution casting method (solution casting method) include a stainless steel band, a drum type casting machine, a band type casting machine, and a spin coater.

  In the solution casting method (solution casting method), preferably a step of casting the dope on the above-mentioned device, a step of drying the cast dope as a web, a step of peeling the web from the device after drying, stretching or width Film formation is performed by a method including a holding step, a drying step, and the like, and an adjacent layer is formed.

  An injection molding method can be used as a method of forming the adjacent layer in the form of a substrate. The substrate is produced by injection molding by melting and kneading the adjacent layer components, injection from the kneader to the mold, cooling in the mold, and taking out the substrate.

  For melt kneading of the resin and other components, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used. In that case, in order to ensure the uniformity of the kneaded product, it is preferable to perform melt kneading while heating at a temperature higher than the glass transition temperature (Tg) of the resin.

  From the standpoints of ensuring molding accuracy and ensuring the optical properties of the molded product, the injection amount of the kneaded product and the temperature control of the mold are important. The injection amount can be adjusted by the amount of pressurization from the kneader to the mold, the diameter of the inner layer serving as a path from the kneaded product to the mold, the temperature applied to the inner layer, and the like. The mold temperature during injection of the kneaded product is preferably set to be equal to or lower than the Tg of the resin. Thereby, dimensional accuracy is securable. Further, in order to ensure optical characteristics, the preferable cooling temperature is within the range of Tg-100 ° C. or lower, below Tg of the resin, more preferably within the range of Tg-50 ° C. below Tg, more preferably Tg− below Tg. The range is up to 20 ° C.

[Volume hologram recording layer]
The volume hologram recording layer is a coating film (photosensitive layer) obtained by applying a photosensitive composition containing a polymerizable monomer, a photopolymerization initiator, and a matrix resin or a precursor thereof to the aforementioned adjacent layer and drying it. On the other hand, it is produced by forming a diffraction grating composed of a high refractive index region and a low refractive index region in the photosensitive layer by performing at least holographic exposure.

  The photosensitive composition used for forming the volume hologram recording layer may contain a sensitizer, a solvent and the like in addition to a radical polymerizable monomer, a photopolymerization initiator, and a matrix forming material. Hereinafter, these components will be described.

<Radically polymerizable monomer>
As the radical polymerizable monomer, those exhibiting a relatively high refractive index are preferable. For example, acrylamide, methacrylamide, methylene bisacrylamide, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate. 2,3-dibromopropyl acrylate, dicyclopentanyl acrylate, dibromoneopentyl glycol diacrylate, 2-phenoxyethyl acrylate, 2-phenoxymethyl methacrylate, phenol ethoxylate monoacrylate, 2- (p-chlorophenoxy) Ethyl acrylate, p-chlorophenyl acrylate, phenyl acrylate, 2-phenylethyl acrylate, 2- ( -Naphthyloxy) ethyl acrylate, o-biphenyl methacrylate, o-biphenyl acrylate, styrene, methoxystyrene, benzyl acrylate, phenyl acrylate, 2-phenylethyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, phenol ethoxylate acrylate , Methylphenoxyethyl acrylate, nonylphenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, phenoxypolyethylene glycol acrylate, 1,4-benzenediol dimethacrylate, 1,4-diisopropenylbenzene, 1,3,5- Triisopropenylbenzene, benzoquinone monomethacrylate, 2- (1-naphthyloxy) ethyl acrylate 2,3-naphthalenedicarboxylic acid (acryloxyethyl) monoester, di (3-methacryloxy-2-hydroxypropyl) ether of diphenolic acid, β-acryloxyethyl hydrogen phthalate, 2,2-di (p- Hydroxyphenyl) propane diacrylate, 2,3-di (p-hydroxyphenyl) propane dimethacrylate, 2,2-di (p-hydroxyphenyl) propane dimethacrylate, polyoxyethyl-2,2-di (p-hydroxy) Phenyl) propane dimethacrylate, bisphenol-A di (2-methacryloxyethyl) ether, ethoxylated bisphenol-A diacrylate, bisphenol-A di (3-acryloxy-2-hydroxypropyl) ether, bisphenol-A di (2-Ak Loxyethyl) ether, 2,2-bis (4-acryloxyethoxyphenyl) propane, 2,2-bis (4-methacryloxyethoxyphenyl) propane, 2,2-bis (4-acryloxydiethoxyphenyl) propane, 2,2-bis (4-methacryloxydiethoxyphenyl) propane, bis (4-acryloxydiethoxyphenyl) methane, bis (4-methacryloxydiethoxyphenyl) methane, 2-chlorostyrene, 2-bromostyrene, 2- (p-chlorophenoxy) ethyl acrylate, tetrachloro-bisphenol-A di (3-acryloxy-2-hydroxypropyl) ether, tetrachloro-bisphenol-A di (2-methacryloxyethyl) ether, tetrabromo- Di (3-meta of bisphenol-A Riloxy-2-hydroxypropyl) ether, di (2-methacryloxyethyl) ether of tetrabromo-bisphenol-A, bis (4-acryloxyethoxy-3,5-dibromophenyl) methane, bis (4-methacryloxyethoxy-) 3,5-dibromophenyl) methane, 2,2-bis (4-acryloxyethoxy-3,5-dibromophenyl) propane, 2,2-bis (4-methacryloxyethoxy-3,5-dibromophenyl) propane Bis (4-acryloxyethoxyphenyl) sulfone, bis (4-methacryloxyethoxyphenyl) sulfone, bis (4-acryloxydiethoxyphenyl) sulfone, bis (4-methacryloxydiethoxyphenyl) sulfone, bis (4 -Acryloxypropoxypheny-dibromofe Nyl) sulfone, bis (4-methacryloxypropoxypheny-dibromophenyl) sulfone, diethylenedithioglycol diacrylate, diethylenedithioglycol dimethacrylate, triphenylmethylthioacrylate, 2- (tricyclo [5,2,10 ^{2 · 6} ] dibromo Decylthio) ethyl acrylate, S- (1-naphthylmethyl) thioacrylate, ethylenic unsaturation containing at least two S atoms in the molecule described in JP-A-2-247205 and JP-A-2-261808 Double bond-containing compound, N-vinylcarbazole, 2- (9-carbazolyl) ethyl acrylate, 2- [β- (N-carbazyl) propionyloxy] ethyl acrylate, 2-naphthyl acrylate, pentachlorophenyl acrylate, 2 , 4,6-tribromophenyl acrylate, 2- (2-naphthyloxy) ethyl acrylate, N-phenylmaleimide, p-biphenyl methacrylate, 2-vinylnaphthalene, 2-naphthyl methacrylate, 2,3-naphthalene dicarboxylic acid (2 -Acryloxyethyl) (3-acryloxypropyl-2-hydroxy) diester, N-phenylmethacrylamide, t-butylphenyl methacrylate, diphenic acid (2-methacryloxyethyl) monoester, diphenic acid (2-acryloxyethyl) ) (3-acryloxypropyl-2-hydroxy) diester, 4,5-phenanthrene dicarboxylic acid (2-acryloxyethyl) (3-acryloxypropyl-2-hydroxy) diester, 2-{{[3- (methyl Sulfanyl) Sulfonyl] such as carbamoyl} oxy} Echirupuropa -2 enoate the like.

  Moreover, what has a 9, 9- diaryl fluorene skeleton and has at least 1 ethylenically unsaturated double bond in a molecule | numerator is mentioned. Specifically, it is a compound having the following structure.

Here, R ₁ and R ₂ are each independently a radical polymerizable group containing an acryloyl group or a methacryloyl group at the terminal. A preferred form is a group having an acryloyl group or a methacryloyl group at the terminal and capable of binding to the benzene ring of the above compound via an oxyethylene chain, an oxypropylene chain, a urethane bond, an amide bond, or the like.

X _{1 to} X ₄ are each independently a hydrogen atom or a substituent. Specific examples of the substituent include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group, a dialkylamino group, a hydroxyl group, a carboxyl group, and a halogen atom.

  In addition, urethane acrylate composed of a condensation product of a phenyl isocyanate compound and a compound having a hydroxy group and an acryloyl group in one molecule can also be used. Specifically, it is a compound having the following structure.

  In the chemical formulas (I) to (III), each R is independently a group having an ethylenically unsaturated bond, and each X is independently a single bond, a straight chain, a branched chain, Or it is a cyclic | annular bivalent aliphatic hydrocarbon group.

  Moreover, the compound which has a structure represented by following Chemical formula (IV) can also be used.

In the chemical formula (IV), R ^{1 to} R ⁵ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a trifluoromethyl group, an alkylthio group having 1 to 6 carbon atoms, or a carbon number. An alkylseleno group having 1 to 6 carbon atoms, an alkyl tellurium group having 1 to 6 carbon atoms, or a nitro group, and R ⁶ and R ⁷ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. .

  A represents a linear or branched alkylene group having 1 to 6 carbon atoms, a linear or branched alkenylene group having 2 to 6 carbon atoms, or a polyalkylene having 2 to 6 ethylene oxide units or propylene oxide units. An alkylene oxide group;

  Among these radical polymerizable monomers, a monomer having a substituted or unsubstituted phenyl group, a monomer having a substituted or unsubstituted naphthyl group, a substituted or unsubstituted heterocyclic aromatic moiety having up to 3 rings A monomer having a chlorine atom, a monomer having a chlorine atom, and a monomer containing a bromine atom are preferable because of their relatively high refractive index.

  The radical polymerizable monomers can be used alone or in combination of two or more.

  The content of the radical polymerizable monomer in the photosensitive composition is preferably 1 to 25% by mass and more preferably 5 to 20% by mass with respect to the total mass of the photosensitive composition.

<Radical radical polymerization initiator>
The radical photopolymerization initiator is an agent that initiates photopolymerization of a radical polymerizable monomer by irradiation with laser light having a specific wavelength or light having excellent coherence in holographic exposure. Examples of photo radical polymerization initiators include, for example, US Pat. Nos. 4,766,055, 4,868,092, 4,965,171, JP-A Nos. 54-151024, 58-15503, 58-28803. No. 59-189340, No. 60-76735, No. 1-28715, No. 4-239505 and “Proceedings of Conference on Radiation Curing Asia ( Although known polymerization initiators described in “PROCEEDINGS OF CONFERENCE ON RADIATION CURING ASIA” (pp. 461-477, 1988) can be used, they are not limited thereto.

  Specific examples of the radical photopolymerization initiator include, for example, diaryliodonium salts, 2,4,6-substituted-1,3,5-triazines (triazine compounds), azo compounds, azide compounds, organic peroxides, organic Examples thereof include boronates, onium salts, halogenated hydrocarbon derivatives, titanocene compounds, monoacylphosphine oxides, bisacylphosphine oxides, and combinations of bisacylphosphine oxides and α-hydroxyketones. Moreover, the radical photopolymerization initiator system by combined use of hydrogen donors, such as a thiol compound, and a bisimidazole derivative can also be utilized. These radical photopolymerization initiators may be used alone or in combination of two or more.

  The amount of the photo radical polymerization initiator used is preferably 0.05 to 50 parts by mass, more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the radical polymerizable monomer.

<Sensitizer>
The photosensitive composition may contain a sensitizer having a sensitization function for the radical photopolymerization initiator. Such a sensitizer has an absorption maximum wavelength in the range of 400 to 800 nm, particularly 450 to 700 nm. These sensitizers absorb light in the above range, thereby causing a sensitizing action on the radical photopolymerization initiator.

  Examples of such a sensitizer include polymethine compounds such as cyanine dyes and styryl dyes, xanthene compounds such as rhodamine B, rhodamine 6G, and pyronin GY, phenazine compounds such as safranin O, cresyl violet, Phenoxazine compounds such as brilliant cresyl blue, phenothiazine compounds such as methylene blue and new methylene blue, diarylmethane compounds such as auramine, triarylmethane compounds such as crystal violet, brilliant green and lissamine green, (thio) pyrylium Examples thereof include salt compounds, squarylium compounds, coumarin dyes, thioxanthene dyes, acene dyes, merocyanine dyes, thiazolium dyes, and the like. These sensitizers can be used alone or in combination of two or more.

  When the sensitizer is used, the amount used is preferably 1 to 2000 parts by mass and more preferably 20 to 1500 parts by mass with respect to 100 parts by mass of the radical photopolymerization initiator.

<Matrix resin or precursor thereof>
The matrix resin functions to improve the uniformity of the film thickness of the volume hologram recording layer, heat resistance, mechanical properties, etc., and stabilize the hologram formed by holographic exposure. Further, when the volume hologram recording layer is formed, it may have a function of not inhibiting or efficiently expressing the diffusion transfer phenomenon of the polymerizable monomer or photopolymer.

  As the matrix resin, for example, any of thermoplastic resins, thermosetting resins, active energy ray curable resins, and the like can be used without limitation. In addition, those resins modified with a polysiloxane chain or a perfluoroalkylene chain can also be used. The matrix resins can be used alone or in combination of two or more.

  Examples of thermoplastic resins include, for example, polyvinyl acetate, polyvinyl butyrate, polyvinyl formal, polyvinyl carbazole, polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polymethacrylo Nitrile, polyethyl methacrylate, polybutyl methacrylate, polyacrylonitrile, poly-1,2-dichloroethylene, ethylene-vinyl acetate copolymer, syndiotactic polymethyl methacrylate, poly-α-vinyl naphthalate, polycarbonate, cellulose acetate, Cellulose triacetate, cellulose acetate butyrate, polystyrene, poly-α-methylstyrene, poly-o-methylstyrene, poly-p-me Styrene styrene, poly-p-phenylstyrene, poly-2,5-dichlorostyrene, poly-p-chlorostyrene, poly-2,5-dichlorostyrene, polyarylate, polysulfone, polyethersulfone, styrene-acrylonitrile copolymer, Styrene-divinylbenzene copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, ABS resin, polyethylene, polyvinyl chloride, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinylpyrrolidone, poly Vinylidene chloride, hydrogenated styrene-butadiene-styrene copolymer, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene, hexafluoroethylene and vinyl Copolymers with alcohol, vinyl ester, vinyl ether, vinyl acetal vinyl butyral, copolymer of (meth) acrylic acid cycloaliphatic ester and methyl (meth) acrylate, polyvinyl acetate, methyl methacrylate-ethyl acrylate-acrylic An acid copolymer etc. are mentioned.

  Examples of the thermosetting resin include unsaturated polyester, acrylic urethane resin, epoxy-modified acrylic resin, epoxy-modified unsaturated polyester, polyurethane, alkyd resin, and phenol resin.

  Examples of the active energy ray-curable resin include epoxy acrylate, urethane acrylate, and acrylic-modified polyester. These active energy ray-curable resins can contain other monofunctional or polyfunctional monomers, oligomers and the like as described below for the purpose of adjusting the cross-linked structure and viscosity. For example, mono (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, vinyl pyrrolidone, (meth) acryloyloxyethyl succinate, (meth) acryloyloxyethyl phthalate, etc. When classified by skeleton structure, polyol (meth) acrylate (epoxy-modified polyol (meth) acrylate, lactone-modified polyol (meth) acrylate, etc.), polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and other polybutadienes Poly (meth) acrylates with isocyanuric acid-based, hydantoin-based, melamine-based, phosphoric acid-based, imide-based, phosphazene-based skeletons, and are UV- and electron-beam curable Monomers, oligomers, polymers may be utilized such.

  When using the above thermoplastic resin, thermosetting resin, or active energy ray curable resin, metal soap such as cobalt naphthenate and zinc naphthenate, organic peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, benzophenone Thermal or active energy ray curing agents such as acetophenone, anthraquinone, naphthoquinone, azobisisobutyronitrile, diphenyl sulfide and the like can be contained in the photosensitive composition.

  In the case of using a thermosetting resin or an active energy ray curable resin, after forming a photosensitive layer containing an uncured resin on the adjacent layer, it can be cured by heating or irradiation with an active energy ray. Curing may be performed before or after holographic exposure.

  Alternatively, a matrix resin precursor may be used. Examples of the precursor include an isocyanate compound and a polyol compound that form a polyurethane by addition polymerization.

  As the isocyanate compound, those having two or more isocyanate groups in one molecule are preferable, but the type is not particularly limited. If the number of isocyanate groups in one molecule is small, the hardness required for the matrix resin may not be obtained. The upper limit of the number of isocyanate groups in one molecule is not particularly limited, but is usually 8 or less, preferably 4 or less. The type is not particularly limited as long as it has two or more isocyanate groups in one molecule. The upper limit of the number of isocyanate groups in one molecule is not particularly limited, but is usually about 20 or less.

  Examples of the isocyanate used in the present embodiment include aliphatic isocyanates such as hexamethylene diisocyanate, lysine methyl ester diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate). ), Etc .; aromatic diisocyanates such as tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene-1,5′-diisocyanate; and multimers thereof.

  In addition to these, there can be mentioned a reaction product of polyhydric alcohols such as water, trimethylolethane and trimethylolpropane and the above-mentioned isocyanates, a multimer of hexamethylene diisocyanate, or a derivative thereof.

  These isocyanate compounds may be used alone or in combination of two or more.

  Examples of the polyol compound include polypropylene polyol, polycaprolactone polyol, polyester polyol, polycarbonate polyol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1 , 6-hexanediol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, decamethylene glycol, trimethylolpropane, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

  These polyol compounds may be used alone or in combination of two or more.

  A catalyst for addition polymerization of an isocyanate compound and a polyol compound can be blended in the photosensitive composition. Although it can be cured at room temperature by using a catalyst, it may be cured by heating. The temperature during curing is preferably in the range of 40 to 90 ° C., and the curing time is preferably 1 to 24 hours.

  Examples of the catalyst include ordinary urethanization reaction catalysts, for example, tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate and dibutyltin dioctanoate, and tertiary amine compounds such as triethylamine and triethylenediamine. Among these, the tin compound has good solubility and performance as a medium, and dibutyltin dilaurate is particularly preferable.

  The amount of the catalyst used is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and preferably 10% by mass or less, based on the total amount of the isocyanate compound and the polyol compound, and 5% by mass or less. Is more preferable. In addition, when using these catalysts, it is preferable to add in a photosensitive composition within 10 minutes before apply | coating a photosensitive composition on an adjacent layer from a viewpoint of ensuring the uniformity of a photosensitive layer coating film.

  Moreover, you may use a cation polymerizable monomer as another precursor of matrix resin. A matrix resin made of a cationic polymerizable monomer makes it possible to produce a volume hologram recording layer having excellent film strength.

  Specific examples of such cationically polymerizable monomers include diglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, 1,4-bis (2,3-epoxypropoxyperfluoroisopropyl) cyclohexane, sorbitol polyglycidyl ether, trimethylolpropane poly Glycidyl ether, resorcin diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, phenyl glycidyl ether, paratertiary butylphenyl glycidyl ether, adipic acid diglycidyl ester, orthophthalic acid diglycidyl ester, dibromophenyl Glycidyl ether, dibromoneopentyl glycol diglycidyl ether, 1,2,7,8-die Xyloctane, 1,6-dimethylol perfluorohexane diglycidyl ether, 4,4′-bis (2,3-epoxypropoxyperfluoroisopropyl) diphenyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexane Carboxylate, 3,4-epoxycyclohexyloxirane, 1,2,5,6-diepoxy-4,7-methanoperhydroindene, 2- (3,4-epoxycyclohexyl) -3 ′, 4′-epoxy-1 , 3-Dioxane-5-spirocyclohexane, 1,2-ethylenedioxy-bis (3,4-epoxycyclohexylmethane), 4 ', 5'-epoxy-2'-methylcyclohexylmethyl-4,5-epoxy- 2-methylcyclohexanecarboxylate, ethylene glycol Cole-bis (3,4-epoxycyclohexanecarboxylate), bis- (3,4-epoxycyclohexylmethyl) adipate, di-2,3-epoxycyclopentyl ether, vinyl-2-chloroethyl ether, vinyl-n-butyl ether , Triethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, trimethylolethane trivinyl ether, vinyl glycidyl ether, and the like. These cationic polymerizable monomers can be used alone or in combination of two or more.

  When the above cationic polymerizable monomer is used, a photo cationic polymerization initiator or a thermal cationic polymerization initiator may be used.

  Specific examples of the photocationic polymerization initiator include iodonium salts and triarylsulfonium salts. Specific examples of the iodonium salts include iodonium tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, trifluoromethanesulfonate, 9,10-dimethoxyanthracene-2-sulfonate, and the like. Specific examples of triarylsulfonium salts include triarylsulfonium, triphenylsulfonium, 4-tertiarybutyltriphenylsulfonium, tris (4-methylphenyl) sulfonium, tris (4-methoxyphenyl) sulfonium, 4-thiophenyltri Examples include sulfonium tetrafluoroborate such as phenylsulfonium, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, trifluoromethanesulfonate, 9,10-dimethoxyanthracene-2-sulfonate, and the like. These photocationic polymerization initiators can be used singly or in combination of two or more.

  Specific examples of the thermal cationic polymerization initiator include cationic or protonic acid catalysts such as triflate, boron trifluoride etherate compound, boron trifluoride and the like. Preferred thermal cationic polymerization initiators are , Triflate. Specific examples include diethylammonium triflate, triethylammonium triflate, diisopropylammonium triflate, ethyl diisopropylammonium triflate available from 3M as “FC-520” (many of which are by RR Alm in 1980). There is Modern Coatings (published in October). Moreover, among aromatic onium salts used as active energy ray cationic polymerization initiators, there are those that generate cationic species by heat, and these can also be used as thermal cationic polymerization initiators. Examples include “Sun-Aid (registered trademark) SI-60L”, “Sun-Aid (registered trademark) SI-80L” and “Sun-Aid (registered trademark) SI-100L” (manufactured by Sanshin Chemical Industry Co., Ltd.). When a cationic polymerizable monomer is used as the matrix resin, the amount of the photo cationic polymerization initiator or the thermal cationic polymerization initiator used is preferably 0.05 to 50 parts by mass with respect to 100 parts by mass of the cationic polymerizable monomer. -30 mass parts is more preferable.

  The content of the matrix resin or the precursor thereof in the photosensitive composition is preferably 1 to 30% by mass, more preferably 1 to 25% by mass with respect to the total mass of the photosensitive composition, More preferably, it is 5-25 mass%.

<Solvent>
The photosensitive composition may use a solvent as needed when coating. However, when the photosensitive composition contains a component that is liquid at room temperature, a solvent may not be necessary.

  Examples of the solvent include aliphatic solvents such as n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, and methylcyclohexane; ketone solvents such as methyl ethyl ketone (2-butanone), acetone, and cyclohexanone; Ether solvents such as diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, anisole, phenetole; ethyl acetate, butyl acetate, ethylene glycol diacetate Ester solvents such as toluene, aromatic solvents such as xylene, methyl cellosolve, ethyl acetate Cellosolve solvents such as sorb and butylcellosolve; alcohol solvents such as methanol, ethanol, propanol and isopropyl alcohol; ether solvents such as tetrahydrofuran and dioxane; halogen solvents such as dichloromethane and chloroform; nitriles such as acetonitrile and propionitrile Solvent; polar solvents such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like. These solvents can be used alone or in combination of two or more.

<Additives>
As long as the above-described effects are not impaired, the photosensitive composition is optionally made of a plasticizer, a compatibilizer, a polymerization inhibitor, a surfactant, a silane coupling agent, an antifoaming agent, a release agent, a stabilizer, an oxidation agent. You may further contain additives, such as an inhibitor, a flame retardant, an optical brightener, and an ultraviolet absorber.

[Method for preparing photosensitive composition]
The photosensitive composition can be obtained by mixing the above-described components all at once or sequentially. Examples of the apparatus used for mixing include stirring or mixing apparatuses such as a magnetic stirrer, homodisper, quick homomixer, and planetary mixer. The obtained photosensitive composition may be used after filtration, if necessary.

[Method of manufacturing holographic optical element]
A method for producing a holographic optical element is not particularly limited, but a photosensitive layer containing a polymerizable monomer is formed on an adjacent layer containing a resin and an aromatic ester compound having a molecular weight of 180 to 400, and the photosensitive layer is formed on the photosensitive layer. For example, a production method including performing a holographic exposure to form a volume hologram recording layer may be mentioned.

  Since the manufacturing method of an adjacent layer is as above-mentioned, description is abbreviate | omitted here.

  The method for forming the photosensitive layer on the adjacent layer is not particularly limited. For example, the photosensitive composition is directly applied on the adjacent layer and dried, or the photosensitive composition is applied on a separately prepared substrate. Then, after drying, there is a method of laminating the adjacent layer using a laminator or the like and then peeling the substrate. Among these, from the viewpoint that the photosensitive composition more easily penetrates into the adjacent layer and the diffraction grating easily forms over the adjacent layer, the photosensitive layer is formed by directly applying the photosensitive composition on the adjacent layer and drying it. Is preferably formed.

  In addition, as the base material, acrylic resin, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthoate, polyethylene, polypropylene, amorphous polyolefin, cellulose acetate, hydrated cellulose, cellulose nitrate, cycloolefin polymer, polystyrene, polyepoxide, Examples of the resin base material include polysulfone, cellulose acylate, polyamide, polyimide, polymethyl methacrylate, polyvinyl chloride, polyvinyl butyral, polydicyclopentanediene, and the like.

  As a method for applying the photosensitive composition on the adjacent layer or the substrate, a conventionally known method can be used, and specific examples include a spray method, a spin coating method, a wire bar method, a dip coating method, Examples thereof include an air knife coating method, a roll coating method, a blade coating method, and a doctor roll coating method.

  For drying, various conventionally known methods using a hot plate, an oven, a belt furnace or the like can be employed. The drying temperature can be selected within a range that does not impair the photosensitivity of the above-described photosensitive composition.

  What is necessary is just to set the thickness of a photosensitive layer suitably so that it may become the range of the preferable thickness of the volume hologram recording layer mentioned later.

  By forming a photosensitive layer on the adjacent layer, bonding the adjacent layer and the photosensitive layer, and then performing holographic exposure, the polymerization reaction of the polymerizable monomer in the photosensitive layer proceeds, and the photocured photo produced by the polymerization reaction The polymer region and the other component region are formed in the same pattern as the interference wave irradiated by the holographic exposure.

  In the holographic optical element of the present embodiment, when the volume hologram recording layer has a structure sandwiched between two adjacent layers, after forming a photosensitive layer on one adjacent layer, another on the photosensitive layer. By laminating adjacent layers using a laminator or the like, a holographic optical element having the structure can be obtained.

〔Recording method〕
The method of performing holographic exposure on the photosensitive layer and recording (writing) a volume hologram to form a volume hologram recording layer and the method of reproducing (reading) the volume hologram are not particularly limited, and examples thereof include the following methods. .

  First, at the time of recording information, light capable of causing a chemical change of the polymerizable monomer, that is, polymerization and concentration change, is used as recording light (also called object light).

  For example, when recording information as a volume hologram, object light is irradiated onto the photosensitive layer together with reference light so that the object light and reference light interfere with each other in the photosensitive layer. As a result, the interference light causes polymerization and concentration change of the polymerizable monomer in the photosensitive layer. As a result, the interference fringes cause a refractive index difference in the photosensitive layer, and the interference fringes recorded in the photosensitive layer It is recorded as a volume hologram and becomes a volume hologram recording layer.

  As the recording light used for recording the volume hologram (the wavelength in the parentheses indicates a wavelength), it is preferable to use a visible light laser having excellent coherence. For example, an argon ion laser (458 nm, 488 nm, 514 nm), a krypton ion laser (647 0.1 nm), helium-neon laser (633 nm), YAG laser (532 nm), and the like.

The irradiation energy amount (exposure amount) at the time of hologram recording is not particularly limited, but is preferably in the range of 10 to 250 mJ / cm ² .

  Hologram recording methods include a polarization collinear hologram recording method, a reference light incident angle multiplexing hologram recording method, and the like, and any recording method can provide good recording quality.

  The exposure apparatus is not particularly limited. For example, an exposure apparatus having a schematic configuration as shown in FIG. 2 can be used. In the exposure apparatus shown in FIG. 2, the light beam (recording light) emitted from the laser light source 201 guides the light beam to a suitable position in the exposure system by the beam steerers 202a and 202b composed of two pairs of mirrors. A shutter 203 controls ON / OFF of a light beam (recording light). A beam expander 204 has a function of expanding the beam diameter and changing the aperture ratio (NA) according to the exposure area of the photosensitive layer.

  The light beam (recording light) that has passed through the beam expander 204 is divided into two light beams by the beam splitter 205. The divided light beams (recording light) are guided to the spatial filters 211 and 212 by the mirrors 206 and 207 and the mirrors 209 and 208, respectively. Spatial filters 211 and 212 are composed of a lens and a pinhole, and collect light rays (recording light) with the lenses, and guide the light rays (recording light) to the manufacturing optical system 213 through the pinholes.

  The production optical system 213 can set and fix a sample such as a glass prism provided with a photosensitive layer serving as a volume hologram recording layer at a suitable position so that the reflection angle of the light beam of the holographic optical element can be controlled.

  A photosensitive layer provided on a prism or the like fixed to the manufacturing optical system 213 is divided into two light beams, and is subjected to holographic exposure (interference exposure) by light beams (recording light) guided through the spatial filters 211 and 212, respectively. The

  Although only one light source is shown in FIG. 2, when holographic exposure is performed using a plurality of laser light sources having different wavelengths, a glitch mirror is inserted in the optical path before the shutter 203 to The emitted laser beam may be synthesized stepwise.

After the volume hologram is recorded, the volume hologram recording layer can be further subjected to appropriate treatments such as full exposure with ultraviolet rays and heating in order to promote refractive index modulation and complete (fix) the polymerization reaction. As a light source used for the entire surface exposure, for example, a light source emitting ultraviolet rays such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a carbon arc lamp, a xenon arc lamp, a metal halide lamp, or the like can be used. The amount of irradiation energy in the case of performing the entire surface exposure with ultraviolet rays is preferably 50 to 200 J / cm ² . Moreover, 50-150 degreeC is preferable for the temperature at the time of heat processing, and 30 minutes-3 hours are preferable for processing time.

  When performing both the whole surface exposure and the heat treatment, the order is not particularly limited, and the whole surface exposure may be performed first, or the heat treatment may be performed first.

  In the present embodiment, the thickness of the volume hologram recording layer is preferably 10 to 100 μm and more preferably 20 to 50 μm from the viewpoint of durability.

  When reproducing the volume hologram recorded on the volume hologram recording layer, predetermined reproduction light (usually reference light) is irradiated to the volume hologram recording layer. The irradiated reproduction light is diffracted according to the interference fringes. Since this diffracted light contains the same information as the volume hologram recording layer, the information recorded in the volume hologram recording layer can be reproduced by reading the diffracted light with an appropriate detection means. Note that the wavelength regions of the object light, the reproduction light, and the reference light are arbitrary depending on the application, and may be in the visible light region or the ultraviolet light region.

[Other layers]
In addition to the above, the holographic optical element of the present embodiment may have other layers such as a protective layer, a reflective layer, an antireflection film, and an ultraviolet absorption layer.

  The protective layer is a layer for preventing influences such as deterioration of storage stability of the recording layer. There is no restriction | limiting in the specific structure of a protective layer, It is possible to apply a well-known thing arbitrarily. For example, a layer made of a water-soluble polymer, an organic / inorganic material, or the like can be formed as a protective layer. There is no restriction | limiting in particular in the formation position of a protective layer, For example, you may form between the surface of a volume hologram recording layer, an adjacent layer, and a support body, and may form on the outer surface side of a support body.

  The reflective layer is formed when the holographic optical element is configured to be reflective. In the case of a reflective holographic optical element, the reflective layer is usually formed on the outer surface of the adjacent layer. As the reflective layer, conventionally known ones can be applied as appropriate, and for example, a metal thin film or the like can be used.

  Further, in both transmissive and reflective holographic optical elements, an antireflection film may be provided on the side on which object light and reproduction light are incident and emitted, or between the volume hologram recording layer and the adjacent layer. Good. The antireflection film functions to improve light utilization efficiency and suppress the generation of ghost images. As the antireflection film, conventionally known ones can be referred to as appropriate.

[Support]
The holographic optical element of this embodiment may be further sandwiched between transparent supports. The support may be employed to protect and hold the holographic optical element of this embodiment, or may be employed to function as an optical element such as a prism in combination with the holographic optical element.

  The support is not particularly limited as long as it has necessary strength and durability, and any support can be used. Moreover, although there is no restriction | limiting also in the shape of a support body, Usually, it forms in flat form or a film form. Moreover, there is no restriction | limiting in the material of a support body, Transparent or opaque may be sufficient.

  When a transparent material is used as the support material, inorganic materials such as glass, silicon, and quartz can be used. Among these, glass is preferable. Non-transparent materials for the support include metals such as aluminum; metals such as gold, silver and aluminum coated on the transparent support or dielectrics such as magnesium fluoride and zirconium oxide Is mentioned.

  The surface of the support may be subjected to a surface treatment. This surface treatment is usually performed to improve the adhesion between the support and the holographic optical element. Examples of the surface treatment include subjecting the support to corona discharge treatment or forming an undercoat layer on the support in advance. Here, examples of the composition of the undercoat layer include halogenated phenols, partially hydrolyzed vinyl chloride-vinyl acetate copolymers, polyurethane resins, and the like.

  Furthermore, the surface treatment may be performed for purposes other than the improvement of adhesiveness. Examples thereof include a reflective coating treatment for forming a reflective coating layer made of a metal such as gold, silver, and aluminum; a dielectric coating treatment for forming a dielectric layer such as magnesium fluoride and zirconium oxide, and the like. It is done. In addition, these layers may be formed of a single layer or two or more layers.

  These surface treatments may be provided for the purpose of controlling the gas and moisture permeability of the holographic optical element. Thereby, the reliability of the holographic optical element can be further improved.

  The support may be provided only on either the upper side or the lower side of the holographic optical element, or may be provided on both. However, when providing supports on both the upper and lower sides, at least one of the supports is configured to be transparent so as to transmit active energy rays (recording light, reference light, reproduction light, etc.). When bonding a support body and a holographic optical element, highly transparent adhesives, such as a silicone adhesive and an acrylic adhesive, can be used.

  When the support is provided on one side or both sides of the holographic optical element, a transmissive or reflective hologram can be recorded. When a support having reflection characteristics is used on one side of the holographic optical element, a reflection hologram can be recorded.

[Usage]
The holographic optical element of the present embodiment includes, for example, a head mounted display (HMD), a head-up display (HUD), an optical memory, an optical disk pickup lens, a liquid crystal color filter, a reflective liquid crystal reflector, a lens, a diffraction grating, and an interference. Suitable for filters, optical fiber couplers, optical polarizers for facsimiles, architectural window glass, covers for books, magazines, displays such as POPs, gifts, credit cards, banknotes, packaging, etc. for security purposes It is done.

  Hereinafter, specific examples and comparative examples will be described. However, the technical scope of the present invention is not limited only to the following examples. Moreover, in the following operation, unless otherwise specified, the measurement of the operation and physical properties is performed under the conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50% RH.

<Preparation of adjacent layer 1>
The following components were put into a sealed container, heated to 70 ° C., and then stirred for 4 hours to completely dissolve the cellulose acylate, whereby a dope composition 1 was obtained.

(Dope composition 1)
Cellulose acylate (acetyl group substitution degree 2.41) 96 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole
(Ultraviolet absorber) 1.0 mass part Octyl diphenyl phosphate 3.0 mass part Methylene chloride 475 mass parts Ethanol 50 mass parts.

  The obtained dope composition 1 was filtered, and then uniformly cast on a stainless band support at 30 ° C. at a dope temperature of 35 ° C. using a belt casting apparatus. Then, after drying until it became the amount of residual solvent which can be peeled, dope was peeled from the stainless steel band support body. The residual solvent amount of the dope at this time was 25% by mass. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support, dry it at 120 ° C while holding it in the width direction, release the holding in the width direction, and finish drying in the 120 ° C and 135 ° C drying zones while transporting with many rolls. It was. A knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film to prepare a cellulose acylate film (adjacent layer 1) having a thickness of 60 μm.

<Preparation of adjacent layers 2-17>
In place of octyl diphenyl phosphate, the additive types shown in Table 1 below (triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, diphenyl 2-biphenylyl phosphate, tributyl phosphate, dibutyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl Phthalate, dioctyl phthalate, benzyl propionate, dioctyl adipate) were used, and the addition amount was appropriately set in the range of 0.05 to 11.0 parts by mass to prepare adjacent layers 2 to 17. In addition, cellulose acylate (acetyl group substitution degree 2.60), 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole, The amount of cellulose acylate added was adjusted so that the total amount of additive added was 100 parts by mass. Except for this, the adjacent layers 2 to 17 were prepared in the same manner as the manufacture of the adjacent layer 1 described above.

<Preparation of adjacent layer 18>
97 parts by mass of polyethylene terephthalate (PET) pellets having a glass transition temperature of 80 ° C. and a melting point of 253 ° C. and 3.0 parts by mass of triphenyl phosphate are supplied to the extruder, melt-extruded at a temperature of 280 ° C., and then filtered through a 30 μm cut filter. And then introduced into the T die die.

  Next, from the inside of the T die die, it is extruded into a sheet shape to form a molten single layer sheet, and the molten single layer sheet is closely cooled and solidified by electrostatic application on a drum maintained at a surface temperature of 20 ° C. An unstretched) single layer film was obtained. Subsequently, after preheating the obtained unoriented single-layer film with a group of rolls heated to a temperature of 90 ° C., using a heating roll at a temperature of 95 ° C., 2.5 times between rolls in the longitudinal direction (longitudinal direction) The film was stretched and cooled with a roll group at a temperature of 25 ° C. to obtain a uniaxially oriented (uniaxially stretched) film.

  The obtained uniaxially oriented (uniaxially stretched) film is guided to a preheating zone at a temperature of 95 ° C. in the tenter while holding both ends of the film with clips, and continuously in a heating zone at a temperature of 105 ° C. The film was pulled and stretched 2.5 times in the width direction). Subsequently, heat treatment was performed at 230 ° C. for 20 seconds in the heat treatment zone in the tenter, and after further relaxation treatment in the 4% width direction at a temperature of 200 ° C., further in the 1% width direction at a temperature of 140 ° C. A relaxation treatment was performed. Next, the film was slowly cooled uniformly and then wound up to prepare a PET film (adjacent layer 18) having a film thickness of 60 μm.

<Preparation of adjacent layers 19 and 20>
Instead of triphenyl phosphate, adjacent layers 19 and 20 were prepared using dibutyl phthalate and dibutyl phosphate as additive species as shown in Table 2 below. Except for this, adjacent layers 19 and 20 were manufactured in the same manner as the manufacture of the adjacent layer 18 described above.

<Preparation of adjacent layer 21>
97 parts by mass of cycloolefin polymer pellets (E-48R, glass transition temperature 138 ° C., manufactured by Nippon Zeon Co., Ltd.) and 3.0 parts by mass of cresyl diphenyl phosphate are supplied to an extruder, and after melt extrusion at a temperature of 280 ° C. After filtration through a 30 μm cut filter, it was introduced into a T die die.

  Next, from the inside of the T die die, it is extruded into a sheet shape to form a molten single layer sheet, and the molten single layer sheet is closely cooled and solidified by electrostatic application on a drum maintained at a surface temperature of 20 ° C. An unstretched) single layer film was obtained. Subsequently, after preheating the unoriented single-layer film with a roll group heated to a temperature of 90 ° C., stretching between the rolls by 2.5 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 95 ° C. And cooled with a roll group having a temperature of 25 ° C. to obtain a uniaxially oriented (uniaxially stretched) film.

  The resulting uniaxially oriented (uniaxially stretched) film is guided to a preheating zone at a temperature of 125 ° C. in the tenter while gripping both ends with a clip, and then continuously in the heating zone at a temperature of 120 ° C. The film was stretched by 1.9 times in the width direction. Subsequently, heat treatment was performed at 250 ° C. for 20 seconds in the heat treatment zone in the tenter, and after relaxation treatment in the 4% width direction at a temperature of 230 ° C., further in the 1% width direction at a temperature of 140 ° C. A relaxation treatment was performed. Next, the film was slowly cooled uniformly and then wound up to prepare a cycloolefin resin pellet (adjacent layer 21) having a film thickness of 60 μm.

<Preparation of adjacent layers 22 and 23>
Instead of cresyl diphenyl phosphate, adjacent layers 22 and 23 were prepared using dioctyl phthalate and dibutyl phosphate as shown in Table 3 below. Except for this, adjacent layers 22 and 23 were prepared in the same manner as in the manufacture of adjacent layer 21 described above.

(Example 1: Production of holographic optical element 1)
The following components were put into a container in a dark room and stirred at room temperature for 30 minutes to obtain a solution. The obtained solution was filtered through a mesh to obtain a photosensitive composition 1 for producing a volume hologram recording layer.

<Photosensitive composition 1 for volume hologram recording layer preparation>
12.0 parts by mass of vinyl acetate-tetrafluoroethylene copolymer {vinyl acetate: tetrafluoroethylene copolymer = 78: 22 (mass ratio)}
Phenol ethoxylate monoacrylate 1.0 part by mass Ethoxylated bisphenol A diacrylate 2.0 part by mass Fluorine nonionic surfactant 0.10 part by mass (FC-430; Florad 430; manufactured by 3M Company)
2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-0.05 parts by mass tetraphenyl-1,1'-bisimidazole 4-methyl-4H-1,2,4-triazole -3-thiol 0.05 part by mass The squarylium compound having the following structure 0.10 part by mass

2-Butanone 30.0 parts by mass The photosensitive composition 1 for volume hologram recording layer preparation was applied on one side of the adjacent layer 1 obtained above using a blade coater, and the environment was 20 ° C. and 50% RH. And dried for 30 minutes to obtain a photosensitive layer having a thickness of 25 μm. Subsequently, the adjacent layer 1 separately prepared was further laminated using a laminator on the surface of the photosensitive layer where the adjacent layer 1 was not formed, thereby forming the photosensitive composition 1 for volume hologram recording layer preparation. A photosensitive film 1 in which a photosensitive layer was sandwiched between two adjacent layers 1 was obtained.

After the obtained photosensitive film 1 is sandwiched between a pair of glass prism bases coated with a silicone adhesive as a support, an exposure apparatus having the same basic structure as in FIG. 2 is used (light source: argon Using a laser, an exposure wavelength of 514 nm, holographic exposure was performed so that the irradiation energy amount on the photosensitive layer surface was 24 mJ / cm ² .

  After performing holographic exposure, the holographic optical element 1 having a volume hologram recording layer is obtained by placing it at a position of 15 cm from a high-pressure mercury lamp (illuminance of 100 W) for 60 minutes and then performing heat treatment at 100 ° C. for 3 hours. It was.

(Examples 2 to 16, Comparative Examples 1 to 7: Production of holographic optical elements 2 to 23)
Holographic optical elements 2 to 23 were obtained in the same manner as in Example 1 except that the adjacent layer 1 was changed to the adjacent layers 2 to 23 as shown in Tables 4 and 5 below.

(Example 17: Production of holographic optical element 24)
The following components were put into a container in a dark room and stirred at room temperature for 30 minutes to obtain a solution. The resulting solution was filtered through a mesh to obtain a mixture 2.

Hexamethylene diisocyanate 0.10 parts by mass Polypropylene glycol 10.0 parts by mass
(Molecular weight 4000, hydroxy value 25.3 mg KOH / g)
2-{{[3- (methylsulfanyl) phenyl] carbamoyl} oxy} ethylprop-2-enoate 3.0 parts by mass CGI 909 (organoborate polymerization initiator, manufactured by BASF Japan)
0.01 parts by mass New methylene blue (phenothiazine sensitizing dye, manufactured by BASF Japan Ltd.)
0.10 parts by mass N-ethylpyrrolidone 0.50 parts by mass Ethyl acetate 25.0 parts by mass To the obtained mixture 2, 0.01 parts by mass of dibutyltin dilaurate was added to obtain a photosensitive composition for producing a volume hologram recording layer. 5 minutes after obtaining the product 2, the photosensitive composition 2 for producing a volume hologram recording layer was applied on one side of the adjacent layer 4. Thereafter, the film was dried in an environment of 20 ° C. and 50% RH for 30 minutes, and further heat-treated at 60 ° C. for 2 hours to obtain a photosensitive layer having a thickness of 25 μm. The photosensitive layer formed from the photosensitive composition 2 for volume hologram recording layer preparation by laminating | stacking the adjacent layer 4 produced separately on the surface in which the adjacent layer 4 of a photosensitive layer is not formed using a laminator. A photosensitive film 24 was obtained by being sandwiched between adjacent layers 4.

The obtained photosensitive film 24 is sandwiched between a pair of glass prism bases coated with a silicone adhesive, and using an exposure apparatus having the same basic structure as in FIG. 2 (light source: argon laser, exposure wavelength 514 nm). ), Exposure was performed such that the amount of energy on the photosensitive layer surface was 24 mJ / cm ^2, and a holographic optical element 24 having a volume hologram recording layer was obtained.

(Examples 18 to 19, Comparative Example 8: Production of holographic optical elements 25 to 27)
As shown in Table 5, holographic optical elements 25 to 27 were obtained in the same manner as in Example 17 except that the adjacent layer 4 was changed to the adjacent layers 11, 18, and 21, respectively.

(Example 20: Production of holographic optical element 28)
The following components were put into a container in a dark room and stirred at room temperature for 30 minutes to obtain a solution. The obtained solution was filtered through a mesh to obtain a photosensitive composition 3 for producing a volume hologram recording layer.

<Photosensitive composition 3 for volume hologram recording layer preparation>
30 parts by mass of acrylic resin solution (Foret (registered trademark) GS-1000, solid content 30% by mass, manufactured by Soken Chemical Co., Ltd.)
Denacol EX-411 5.0 parts by mass (pentaerythritol polyglycidyl ether, manufactured by Nagase Chemical Industries, Ltd.)
9,9-bis (4-acryloxydiethoxyphenyl) fluorene 4.0 parts by mass radical polymerization initiator 0.01 parts by mass (diphenyliodonium / trifluoromethanesulfonate)
Cationic polymerization initiator 0.02 parts by mass (triarylsulfonium hexafluoroantimonate, manufactured by Ciba Geigy Corporation)
New methylene blue (phenothiazine sensitizing dye, manufactured by BASF Japan)
0.10 parts by mass Ethyl acetate 5.0 parts by mass The photosensitive composition 3 for producing a volume hologram recording layer is applied on one side of the adjacent layer 4 and dried for 30 minutes in an environment of 20 ° C. and 50% RH. To obtain a photosensitive layer. Thereafter, the adjacent layer 4 is further laminated on the surface of the photosensitive layer where the adjacent layer 4 is not formed, so that the photosensitive layer formed from the photosensitive composition 3 for producing a volume hologram recording layer has two adjacent layers. 4 was obtained.

The obtained photosensitive film 28 is sandwiched between a pair of glass prism bases coated with a silicone adhesive, and an exposure apparatus having the same basic structure as that shown in FIG. Holographic exposure was performed so that the amount was 24 mJ / cm ² .

  After performing the holographic exposure, the holographic optical element 28 having a volume hologram recording layer was obtained by further disposing it at a position 20 cm from the xenon arc lamp (illuminance 150 W) for 30 minutes.

(Examples 21 to 22, Comparative Example 9: Production of holographic optical elements 29 to 31)
As shown in Table 5, holographic optical elements 29 to 31 were obtained in the same manner as in Example 20 except that the adjacent layer 4 was changed to the adjacent layers 11, 18, and 21, respectively.

(Comparative Example 10: Production of holographic optical element 32)
A holographic optical element 32 was obtained in the same manner as in Example 1 except that octyl diphenyl phosphate was not added.

(Comparative Example 11: Production of holographic optical element 33)
A holographic optical element 33 was obtained in the same manner as in Example 13 except that triphenyl phosphate was not added.

(Comparative Example 12: Production of holographic optical element 34)
A holographic optical element 34 was obtained in the same manner as in Example 15 except that tricresyl phosphate was not added.

(Evaluation)
<Diffraction efficiency>
About the obtained holographic optical elements 1-34, the transmittance | permeability was measured on condition of the following using the spectrophotometer U-3900 (made by Hitachi, Ltd.).

Scan range 800nm ~ 400nm
Scan speed 600nm / min
A baseline was calculated from the transmittance of the obtained transmittance data at wavelengths of 600 nm to 460 nm, and the diffraction efficiency was calculated from the values of transmittance T and baseline transmittance B at a wavelength of 521 nm by the following equation.

Diffraction efficiency (%) = [(B−T) / T] × 100
Based on the calculated diffraction efficiency, ranking was performed according to the following criteria. ◎ to ○ are practical. When the diffraction efficiency is 75% or more, for example, when an LED light source is used as the light source of reproduction light, there is a possibility that the power consumption of the LED light source can be reduced. On the other hand, when the diffraction efficiency is low, such as less than 61%, it is necessary to increase the light emission intensity of the LED light source, so that problems such as increased power consumption tend to occur.

<< Evaluation criteria for diffraction efficiency >>
A: Diffraction efficiency is 75% or more B: Diffraction efficiency is 61% or more and less than 75% X: Diffraction efficiency is less than 61% <Durability>
The test for dropping the obtained holographic optical elements 1 to 34 from a height of 100 cm onto a surface plate was performed 10,000 times, and then the diffraction efficiency was measured in the same manner as described above. Moreover, the state observation was performed visually and the peeling state between the volume hologram recording layer and the adjacent layer was evaluated according to the following criteria. ◎ to ○ are practical.

≪Peeling condition evaluation criteria≫
A: No peeling is observed. O: Peeling is observed only at the end. Δ: Peeling is observed at the end and inside. X: Completely peeling.

  The configurations and evaluation results of the holographic optical elements 1 to 34 are shown in Table 4 and Table 5 below.

  Compared with the holographic optical elements 1 to 8 and 12 to 15 and the holographic optical elements 9 to 11, 16, and 17, the adjacent layer containing the resin and the aromatic ester compound having a molecular weight of 180 to 400 causes higher diffraction. It can be confirmed that it has durability capable of maintaining the efficiency for a long time. In particular, it can be seen that when the content of the aromatic ester compound is 0.1 to 10% by mass, the diffraction efficiency is better and the durability is better.

  Further, by comparing the holographic optical elements 1 to 8 and the holographic optical elements 12 to 15, the aromatic ester compound having 2 or 3 phenyl groups has higher durability for maintaining a higher diffraction efficiency for a long time. Can be confirmed. This is presumably because the affinity between the aromatic ester compound and the polymerizable monomer contained in the photosensitive layer was further increased.

  Compared with the holographic optical elements 1 to 8 and 12 to 15 and the holographic optical elements 18, 19 and 21 and 22, the resin contained in the adjacent layer is made of cellulose acylate so that the higher diffraction efficiency can be obtained for a long time. It can be confirmed that it has durability that can be maintained. This is presumably because the mobility of the aromatic ester compound was suitably ensured in the adjacent layer because the compatibility between the cellulose acylate resin and the aromatic ester compound was high.

  Furthermore, from the holographic optical elements 24, 26, 27, 28, 30, and 31, the holographic optical element having the adjacent layer of this embodiment has a high diffraction efficiency for a long time regardless of the composition of the photosensitive layer. It can be confirmed that it has durability that can be maintained at the same level.

10 holographic optical elements,
11 Volume hologram recording layer,
12 adjacent layers,
201 laser light source,
202 Beam steerer,
203 shutter,
204 Beam expander,
205 beam splitter,
206, 207, 208, 209 mirror,
211, 212 spatial filter,
213 Production optics.

Claims (7)

A volume hologram recording layer containing a photopolymer;
At least one adjacent layer that is in contact with the volume hologram recording layer and includes a resin and an aromatic ester compound having a molecular weight of 180 to 400;
Holographic optical element.   The holographic optical element according to claim 1, wherein the aromatic ester compound is at least one of a carboxylic acid ester compound and a phosphoric acid ester compound.   The holographic optical element according to claim 1 or 2, wherein a content of the aromatic-containing ester compound in the adjacent layer is 0.1 to 10% by mass with respect to a total mass of the adjacent layer.   The holographic optical element according to claim 1, wherein the adjacent layer includes cellulose acylate.   The photosensitive composition containing a polymerizable monomer is applied and dried on an adjacent layer containing a resin and an aromatic ester compound having a molecular weight of 180 to 400, and holographic exposure is performed to form a volume hologram recording layer. Method for manufacturing a holographic optical element.   The method for manufacturing a holographic optical element according to claim 5, wherein the adjacent layer is formed by melt extrusion after melt-kneading a material containing the resin and the aromatic ester compound.   The holographic optical element manufacturing method according to claim 5, wherein the adjacent layer is formed by casting a solution in which the resin and the aromatic ester compound are dissolved in a solvent or a dispersion in which the resin is dispersed in a liquid.