Holographic recording medium, its manufacturing method and optical element including the same

Abstract

This application relates to a holographic recording medium, a manufacturing method thereof, and an optical element including the same. The holographic recording medium has excellent diffraction efficiency and colorless and transparent optical properties, so that even when a holographic image is reproduced in space through the holographic recording medium, the holographic recording medium is invisible. Instead, the holographic image can be reproduced vividly and realistically in the void, demonstrating excellent visibility.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0022507, filed February 16, 2024, and Korean Patent Application No. 10-2024-0022508, filed February 16, 2024, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present application relates to a holographic recording medium, a method for manufacturing the same, and an optical element including the same. [Background technology]

[0003] A hologram recording medium records information by changing the refractive index in a holographic recording layer through an exposure process, and reproduces the information by reading the difference in the refractive index recorded in this way.

[0004] In this regard, photopolymer compositions can be used to produce holograms. Photopolymers can easily store optical interference patterns as holograms through photopolymerization of photoreactive monomers. Therefore, photopolymers can be used in a variety of fields, such as smart devices such as mobile devices, components of wearable displays, vehicle accessories (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffractive elements, light guides, waveguides, holographic optical elements having the functions of projection screens and / or masks, optical memory system media and optical diffusion plates, optical wavelength splitters, and reflective and transmissive color filters.

[0005] Specifically, the photopolymer composition for hologram production includes a polymer matrix, a photoreactive monomer, and a photoinitiator system, and a photopolymer layer made from such a composition is irradiated with coherent laser light to induce local photopolymerization of the monomer.

[0006] This localized photopolymerization process results in a refractive index modulation, which in turn generates a diffraction grating. The refractive index modulation value (Δn) is affected by the thickness and diffraction efficiency (DE) of the photopolymer layer, and the angular selectivity becomes wider as the thickness decreases.

[0007] Recently, there has been an increasing demand for the development of materials that can achieve high diffraction efficiency and stable hologram maintenance, and various attempts are being made to manufacture holographic recording media that have high diffraction efficiency and refractive index modulation values ​​despite their thin thickness. Summary of the Invention [Problem to be solved by the invention]

[0008] According to one embodiment of the present invention, a holographic recording medium is provided.

[0009] According to another embodiment of the present invention, there is provided a method for manufacturing the holographic recording medium.

[0010] According to yet another embodiment of the present invention, there is provided an optical element including the holographic recording medium. [Means for solving the problem]

[0011] Hereinafter, a holographic recording medium according to a specific embodiment of the present invention, a method for manufacturing the same, and an optical element including the same will be described.

[0012] Unless otherwise specified, the term "hologram recording medium" used herein refers to a medium capable of recording optical information across the entire visible and ultraviolet ranges (e.g., 300-1,200 nm) through an exposure process. Therefore, the term "hologram recording medium" used herein can refer to a medium on which optical information is recorded, or to a medium before recording in a state in which optical information can be recorded. The term "hologram" used herein may include visual holograms such as in-line (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white-light transmission holograms ("rainbow holograms"), Denisyuk holograms, off-axis reflection holograms, edge-literature holograms, and holographic stereograms.

[0013] As used herein, in relation to the environmental conditions in which a holographic recording medium or an element including the same is placed, the term "high temperature" can refer to a temperature of 60° C. or higher. For example, the high temperature can refer to a temperature of 65° C. or higher, 70° C. or higher, 75° C. or higher, 80° C. or higher, 85° C. or higher, 90° C. or higher, 95° C. or higher, 100° C. or higher, 105° C. or higher, 110° C. or higher, 115° C. or higher, or 120° C. or higher. The upper limit is not particularly limited, and may be, for example, 200° C. or lower, 150° C. or lower, 140° C. or lower, or 130° C. or lower.

[0014] In this specification, when temperature affects the characteristics of a substance, article, or each component, unless temperature is specifically mentioned, the temperature conditions under which the characteristics are measured or described may refer to room temperature (e.g., a temperature in the range of about 15 to 30°C without any particular heating or cooling).

[0015] In this specification, unless otherwise specified, the measured values ​​can be understood as the measured values ​​of the photopolymer layer contained in the holographic recording medium.

[0016] According to one embodiment of the invention, there is provided a holographic recording medium comprising: a polymer matrix or its precursor; and a photopolymer layer comprising a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom, wherein the photoinitiator system comprises a photosensitive dye and a coinitiator, and the photosensitive dyes include a red region photosensitive dye, a green region photosensitive dye, and a blue region photosensitive dye, and the holographic recording medium satisfies the following formulas 1 and 2:

[0017] [Formula 1] T avg ≧90%

[0018] In the above formula 1, T avg is the average transmittance measured in the 400 to 700 nm region for the photopolymer layer that has been photobleached without any optical information recorded thereon;

[0019]

number

[0020] In the above formula 2, ΔE is the color difference between a sample obtained by photobleaching the photopolymer layer without recording optical information and a white light having the same brightness as the photopolymer layer; L S * , a S * and b S * is the color value of the Lab color coordinate system derived from the transmission spectrum of the photobleached sample in the region of 400 to 700 nm, standard illuminant D65, and a viewing angle of 10°, and L R * , a R * and b R * is the color value of the white light in the Lab color coordinate system.

[0021] In order to reproduce hologram images with excellent dynamics, three-dimensionality, realism, and visibility, a hologram recording medium must exhibit high optical recording characteristics and high transparency across all red, green, and blue regions. However, increasing the content of the photosensitive dye to improve the optical recording characteristics results in a decrease in transparency, and decreasing the content of the photosensitive dye to improve transparency also results in a decrease in the optical recording characteristics.

[0022] The holographic recording medium of the embodiment is intended to solve these problems, and is capable of optical recording in the red, green, and blue regions, exhibits high transparency, and can provide holographic images that are dynamic, three-dimensional, realistic, and highly visible.

[0023] Hereinafter, a holographic recording medium according to an embodiment of the present invention, a method for manufacturing the same, and an optical element including the holographic recording medium will be described in detail.

[0024] The holographic recording medium of the embodiment includes a polymer matrix or a precursor thereof; and a photopolymer layer including a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom.

[0025] The photopolymer layer may be a photopolymer layer in a pre-recorded state in which optical information can be recorded, or may be a photopolymer layer in a state in which optical information has been recorded.

[0026] A photopolymer layer with optical information recorded on it can be manufactured by irradiating an object beam and a reference beam onto an unrecorded photopolymer layer. When the object beam and the reference beam are irradiated onto the unrecorded photopolymer layer, the photoinitiator system remains in an inactive state in the destructive interference region due to the interference length between the object beam and the reference beam, preventing photopolymerization of the photoreactive monomer. However, the activated photoinitiator system in the constructive interference region photopolymerizes the photoreactive monomer. As the photoreactive monomer is continuously consumed in the constructive interference region, a concentration difference occurs between the destructive interference region and the constructive interference region. As a result, the photoreactive monomer in the destructive interference region diffuses into the constructive interference region. Because the photoreactive monomer and the photopolymer formed therefrom have a higher refractive index than the polymer matrix, a spatial refractive index change occurs in the photopolymer layer, and this spatial refractive index modulation in the photopolymer layer creates a grating. Such a grating surface acts as a reflective surface that reflects incident light due to the difference in refractive index. After hologram recording, when light of the wavelength used during recording is incident in the direction of the reference light, the Bragg condition is satisfied, and the light is diffracted in the direction of the original object light, allowing the hologram optical information to be reproduced.

[0027] Thus, when the photopolymer layer is in a pre-recorded state, the photopolymer layer may include a photoreactive monomer and a photoinitiator system randomly dispersed within the polymer matrix or its precursor.

[0028] On the other hand, if optical information is recorded in the photopolymer layer, the photopolymer layer may include a photopolymer distributed so as to form a lattice with the polymer matrix.

[0029] The photopolymer layer may be formed from a photopolymer composition that includes a polymeric matrix or its precursor, a photoreactive monomer, and a photoinitiator system.

[0030] The polymer matrix may be formed by crosslinking, for example, a siloxane-based polymer containing a silane functional group (Si—H) and an acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking an acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxyl groups of the acrylic polyol can form crosslinks with the silane functional groups of the siloxane polymer through a hydrosilylation reaction. The hydrosilylation reaction can be rapidly carried out in the presence of a Pt catalyst even at room temperature (e.g., a temperature in the range of about 15 to 30°C without heating or cooling). Therefore, by employing a polymer matrix that can be rapidly crosslinked even at room temperature as the support for the photopolymer layer, the manufacturing efficiency and productivity of holographic recording media can be improved.

[0031] The polymer matrix can enhance the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer through the flexible backbone of the siloxane-based polymer. In addition, the siloxane bond, which has excellent heat resistance and humidity resistance, can easily ensure the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium including the same.

[0032] The polymer matrix may have a relatively low refractive index, thereby enhancing the refractive index modulation of the layer formed from the photopolymer composition. For example, the upper limit of the refractive index of the polymer matrix may be 1.53 or less, 1.52 or less, 1.51 or less, 1.50 or less, or 1.49 or less. The lower limit of the refractive index of the polymer matrix may be, for example, 1.40 or more, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more. In this specification, the "refractive index" may be a value measured using an Abbe refractometer at 25°C.

[0033] The photopolymer layer may include the above-described crosslinked polymer matrix or a precursor thereof. When the photopolymer layer includes a precursor of the polymer matrix, it may include a siloxane-based polymer, an acrylic polyol, and a Pt-based catalyst.

[0034] The siloxane-based polymer may include, for example, a repeating unit represented by the following Chemical Formula 1 and a terminal group represented by the following Chemical Formula 2:

[0035] [ka]

[0036] In the above Chemical Formula 1, Multiple R 11 and R 12 are the same or different and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, k is an integer from 1 to 10,000;

[0037] [ka]

[0038] In the above Chemical Formula 2, Multiple R 13 ~R 15 are the same or different and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, At least one repeating unit selected from the repeating units represented by Chemical Formula 1 and any one of the terminal groups selected from the terminal groups represented by Chemical Formula 2, 11 ~R 15 At least one of is hydrogen.

[0039] In Chemical Formula 2, -(O)- means that when Si of the terminal group represented by Chemical Formula 2 is bonded to the repeating unit represented by Chemical Formula 1, it is bonded via oxygen (O) or directly without oxygen (O).

[0040] As used herein, the term "alkyl group" may be a straight-chain, branched-chain, or cyclic alkyl group. Non-limiting examples of the term "alkyl group" include methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methylpentyl, etc.), methyl ether ... pentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), etc.

[0041] As an example, R in Formulas 1 and 2 11 ~R 15 is methyl or hydrogen, and multiple R 11 ~R 15 At least two of the R in Formula 1 may be hydrogen. 11 and R 12 are methyl and hydrogen, respectively, and R 13 ~R 15 are each independently methyl or hydrogen (e.g., polymethylhydrosiloxane having a terminal trimethylsilyl group or dimethylhydrosilyl group); 11 and R12 are methyl and hydrogen, respectively, and the remaining R 11 and R 12 are all methyl, and R in the formula 2 13 ~R 15 are each independently methyl or hydrogen (e.g., poly(dimethylsiloxane-co-methylhydrosiloxane) having a terminal trimethylsilyl group or a dimethylhydrosilyl group); or R 11 and R 12 are all methyl, and R in the formula 2 13 ~R 15 and the remaining groups are each independently methyl or hydrogen (for example, polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0042] The siloxane-based compound may have a number-average molecular weight (Mn) ranging from 200 to 4,000. Specifically, the lower limit of the number-average molecular weight of the siloxane-based polymer may be, for example, 200 or more, 250 or more, 300 or more, or 350 or more, and the upper limit may be, for example, 3,500 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less. When the number-average molecular weight of the siloxane-based polymer satisfies the above range, problems such as a decrease in the degree of matrix crosslinking due to volatilization of the siloxane-based polymer during crosslinking with an acrylic polyol at room temperature or higher, or poor compatibility of the siloxane-based polymer with other components of the photopolymer layer, causing phase separation with such components, can be prevented, thereby enabling the holographic recording medium of the embodiment to exhibit excellent optical recording characteristics and excellent durability under high-temperature conditions.

[0043] The number average molecular weight refers to the number average molecular weight (unit: g / mol) measured in terms of polystyrene by GPC. The process of measuring the number average molecular weight in terms of polystyrene by GPC can use commonly known analytical equipment, detectors such as a refractive index detector, and analytical columns, and commonly used temperature conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 25°C, tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0044] The acrylic polyol may refer to a polymer in which one or more, specifically two or more, hydroxy groups are bonded to the main chain or side chain of an acrylate polymer. In this specification, unless otherwise specified, "acrylic" refers to one or more selected from an acryloyl group, a methacryloyl group, and derivatives thereof, or a repeating unit formed by polymerization thereof, and unless otherwise specified, "acrylate" refers to one or more selected from an acrylate and a methacrylate, or a repeating unit formed by polymerization thereof.

[0045] The acrylic polyol may be a homopolymer of an acrylate monomer having a hydroxy group, a copolymer of two or more acrylate monomers having a hydroxy group, or a copolymer of an acrylate monomer having a hydroxy group and an acrylate monomer not having a hydroxy group. In this specification, the term "copolymer" encompasses random copolymers, block copolymers, and graft copolymers unless otherwise specified.

[0046] Examples of the acrylate monomer having a hydroxy group include hydroxyalkyl(meth)acrylate and hydroxyaryl(meth)acrylate, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms. Examples of the acrylate monomer not having a hydroxy group include alkyl(meth)acrylate and aryl(meth)acrylate, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms. In this specification, "(meth)acrylate" is a term that refers to acrylate and / or methacrylate unless otherwise specified.

[0047] The acrylic polyol may have a weight-average molecular weight (Mw) in the range of 150,000 to 1,000,000. The weight-average molecular weight refers to a weight-average molecular weight in terms of polystyrene measured by the GPC method described above. For example, the lower limit of the weight-average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less, or 450,000 or less. When the weight-average molecular weight of the acrylic polyol satisfies the above range, the polymer matrix can fully function as a support, resulting in little deterioration in the recording properties for optical information even over time. Furthermore, the polymer matrix can be given sufficient flexibility, improving the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer, thereby minimizing the deterioration in the recording properties for optical information.

[0048] In order to adjust the crosslink density of the acrylic polyol with the siloxane polymer to a level advantageous for ensuring the functionality of the holographic recording medium, the hydroxyl equivalent of the acrylic polyol can be adjusted to an appropriate level.

[0049] Specifically, the hydroxyl (—OH) equivalent of the acrylic polyol may be, for example, within a range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl (—OH) equivalent of the acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. The upper limit of the hydroxyl (-OH) equivalent weight of the acrylic polyol may be 2900 g / equivalent or less, 2800 g / equivalent or less, 2700 g / equivalent or less, 2600 g / equivalent or less, 2500 g / equivalent or less, 2400 g / equivalent or less, 2300 g / equivalent or less, 2200 g / equivalent or less, 2100 g / equivalent or less, 2000 g / equivalent or less, or 1900 g / equivalent or less. The hydroxyl (-OH) equivalent weight of the acrylic polyol is the equivalent weight (g / equivalent) per hydroxy functional group, and is calculated by dividing the weight-average molecular weight of the acrylic polyol by the number of hydroxy functional groups per molecule. The smaller the equivalent weight value, the higher the functional group density, and the larger the equivalent weight value, the lower the functional group density. When the hydroxyl group (—OH) equivalent of the acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslink density and fully functions as a support, and the fluidity of the components contained in the photopolymer layer is improved, so that the boundary surface of the diffraction grating formed after recording does not collapse, and the initial refractive index modulation value can be maintained at an excellent level even over time, minimizing the deterioration of recording characteristics for optical information.

[0050] The acrylic polyol may have a glass transition temperature (Tg) in the range of, for example, −60 to −10°C. Specifically, the lower limit of the glass transition temperature may be, for example, −55°C or higher, −50°C or higher, −45°C or higher, −40°C or higher, −35°C or higher, −30°C or higher, or −25°C or higher, and the upper limit may be, for example, −15°C or lower, −20°C or lower, −25°C or lower, −30°C or lower, or −35°C or lower. When the glass transition temperature falls within the range, the glass transition temperature can be lowered without significantly reducing the modulus of the polymer matrix, thereby increasing the mobility (fluidity) of other components in the photopolymer layer and improving the moldability of the photopolymer composition. The glass transition temperature can be measured using known methods, such as DSC (Differential Scanning Calorimetry) or DMA (Dynamic Mechanical Analysis).

[0051] The refractive index of the acrylic polyol may be, for example, 1.40 or more and less than 1.50. Specifically, the lower limit of the refractive index of the acrylic polyol may be, for example, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more, and the upper limit may be, for example, 1.49 or less, 1.48 or less, 1.47 or less, 1.46 or less, or 1.45 or less. When the acrylic polyol has a refractive index within the above range, it can contribute to enhancing refractive index modulation. The refractive index of the acrylic polyol is a theoretical refractive index and can be calculated using the refractive index of the monomers used in producing the acrylic polyol (measured at 25°C using an Abbe refractometer) and the fraction (molar ratio) of each monomer.

[0052] The acrylic polyol and siloxane polymer can be used so that the molar ratio (SiH / OH) of the silane functional groups (Si-H) of the siloxane polymer to the hydroxy groups (-OH) of the acrylic polyol is 0.80 to 3.5. That is, when forming the polymer matrix, the type and content of the siloxane polymer and the acrylic polyol can be selected so as to satisfy this molar ratio. The lower limit of the molar ratio (SiH / OH) may be, for example, 0.81 or more, 0.85 or more, 0.90 or more, or 0.95 or more, and the upper limit may be, for example, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.05 or less, or 3.0 or less. When the molar ratio (SiH / OH) satisfies this range, the polymer matrix is ​​crosslinked at an appropriate crosslink density, improving reliability under high-temperature conditions and achieving sufficient refractive index modulation.

[0053] The Pt-based catalyst may be, for example, Karstedt's catalyst, etc. The polymer matrix precursor may further include, in addition to the Pt-based catalyst, a rhodium-based, iridium-based, rhenium-based, molybdenum-based, iron-based, nickel-based, alkali metal or alkaline earth metal-based, Lewis acid-based, or carbene-based non-metallic catalyst, if necessary.

[0054] Meanwhile, optical information can be recorded on the holographic recording medium of the embodiment by irradiating an object beam and a reference beam. Due to the interference length between the object beam and the reference beam, photopolymerization of the photoreactive monomer does not occur in the destructive interference region, but occurs in the constructive interference region. As the photoreactive monomer is continuously consumed in the constructive interference region, a concentration difference occurs between the photoreactive monomer in the destructive interference region and the constructive interference region, resulting in diffusion of the photoreactive monomer in the destructive interference region into the constructive interference region. The resulting refractive index modulation generates a diffraction grating.

[0055] Therefore, the photoreactive monomer may include a compound having a refractive index higher than that of the polymer matrix to achieve the above-described refractive index modulation. However, not all of the photoreactive monomers included in the photopolymer composition of the embodiment are limited to having a refractive index higher than that of the polymer matrix. At least some of the photoreactive monomers may have a refractive index higher than that of the polymer matrix to achieve a high refractive index modulation value. For example, the photoreactive monomer may include a monomer having a refractive index of 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or 1.60 or more and 1.70 or less.

[0056] The photoreactive monomer may include one or more monomers selected from the group consisting of monofunctional monomers having one photoreactive functional group and polyfunctional monomers having two or more photoreactive functional groups. In this case, the photoreactive functional group may be, for example, a (meth)acryloyl group, a vinyl group, or a thiol group. More specifically, the photoreactive functional group may be a (meth)acryloyl group.

[0057] The monofunctional monomer may include, for example, one or more selected from the group consisting of benzyl (meth)acrylate (Miwon Corporation, M1182, refractive index 1.5140), benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate (Miwon Corporation, M1122, refractive index 1.565), phenol (ethylene oxide) (meth)acrylate (phenol (EO) (meth)acrylate; Miwon Corporation, M140, refractive index 1.516), phenol (ethylene oxide) 2 (meth)acrylate (Miwon Corporation, M142, refractive index 1.510), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol (EO) (meth)acrylate; Miwon Corporation, M1142, refractive index 1.577), phenylthioethyl (meth)acrylate (Miwon Corporation, M1162, refractive index 1.560), and biphenylmethyl (meth)acrylate.

[0058] The polyfunctional monomer is, for example, bisphenol A (ethylene oxide). 2~10 Di(meth)acrylate (bisphenol A (EO) 2~10(meth)acrylate; Miwon's M240 refractive index 1.537, M241 refractive index 1.529, M244 refractive index 1.545, M245 refractive index 1.537, M249 refractive index 1.542, M2100 refractive index 1.516, M2101 refractive index 1.512), bisphenol A epoxy di(meth)acrylate (Miwon's PE210 refractive index 1.557, PE2120A refractive index 1.533, PE2120B refractive index 1.534, PE2020C refractive index 1.539, PE2120S refractive index 1.556), bisfluorene di(meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR604 The epoxy resin may include one or more selected from the group consisting of modified bisphenol A fluorene di(meth)acrylate (Miwon's HR6060 refractive index 1.584, HR6100 refractive index 1.562, HR6200 refractive index 1.530), tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate (Miwon's M370 refractive index 1.508), phenol novolac epoxy (meth)acrylate (Miwon's SC6300 refractive index 1.525), and cresol novolac epoxy (meth)acrylate (Miwon's SC6400 refractive index 1.522, SC6400C refractive index 1.522).

[0059] The photopolymer layer may contain 50 to 300 parts by weight of the photoreactive monomer relative to 100 parts by weight of the polymer matrix. For example, the lower limit of the content of the photoreactive monomer may be 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or 90 parts by weight or more, and the upper limit may be 300 parts by weight or less, 280 parts by weight or less, 250 parts by weight or less, 220 parts by weight or less, 200 parts by weight or less, 190 parts by weight or less, or 180 parts by weight or less. Satisfying these ranges is advantageous in ensuring excellent optical recording properties and durability in high-temperature environments.

[0060] In this specification, the content of the polymer matrix refers to the combined content (by weight) of the acrylic polyol and siloxane polymer that form the matrix, i.e., the content of the polymer matrix includes both the polymer matrix formed by crosslinking the acrylic polyol and the siloxane polymer and the partially uncrosslinked polymer matrix precursor.

[0061] The photopolymer layer includes a photopolymer that contains or is polymerized by a photoinitiator system, which refers to a combination of a photosensitive dye and a coinitiator that allows polymerization to be initiated by light.

[0062] The holographic recording medium according to the embodiment includes a red region photosensitive dye, a green region photosensitive dye, and a blue region photosensitive dye as photosensitive dyes, and is capable of optical recording in the red, green, and blue regions.

[0063] In particular, the holographic recording medium according to the embodiment employs compounds of specific structures as the red region photosensitive dye, the green region photosensitive dye, and the blue region photosensitive dye, thereby exhibiting high optical recording properties and transparency.

[0064] The red light-sensitive dye, green light-sensitive dye, and blue light-sensitive dye refer to dyes that selectively respond to light in the red, green, and blue regions, respectively. Within the visible light wavelength range of 400 to 700 nm, the red region refers to, for example, a wavelength range of 600 to 700 nm, 600 to 680 nm, 600 to 670 nm, 600 to 660 nm, 600 to 650 nm, or 600 to 640 nm; the green region refers to, for example, a wavelength range of 490 to 570 nm, 490 to 560 nm, 490 to 550 nm, 490 to 540 nm, or 492 to 535 nm; and the blue region refers to, for example, a wavelength range of 400 to 480 nm, 400 to 470 nm, 410 to 470 nm, 410 to 460 nm, or 420 to 460 nm.

[0065] While existing holographic recording media capable of optical recording in the blue region tend to have low transparency, which reduces the realism and visibility of holographic images, the holographic recording media according to the present embodiment employs a compound with a specific structure as the blue region photosensitive dye, thereby exhibiting high transparency.

[0066] The blue light-sensitive dye may include, for example, a cation-containing compound represented by the following Chemical Formula 3:

[0067] [ka]

[0068] In the above Chemical Formula 3, R 1 is an alkylene group having 1 to 6 carbon atoms, and R 2 is an alkyl group having 1 to 6 carbon atoms, n1 is an integer from 1 to 6, R 3 is an alkyl group having 3 to 12 carbon atoms, R 4 is hydrogen or an alkyl group having 1 to 6 carbon atoms, R 5 and R 6 are each independently a halogen, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, n2 and n3 each independently represent an integer of 0 to 4, Z is oxygen, sulfur or CR 7 R 8 and R 7 and R 8 are each independently an alkyl group having 1 to 6 carbon atoms.

[0069] In the above chemical formula 3, R 1may be, for example, a methylene group, a 1,2-ethylene group, a 1,3-propylene group, a 1,2-propylene group, a 1,4-butylene group, a 1,3-butylene group, a 1,2-butylene group, or an isobutylene group. 1 may be, for example, a 1,2-ethylene group, a 1,2-propylene group, or an isobutylene group. More specifically, R 1 may be, for example, a 1,2-ethylene group.

[0070] In the above chemical formula 3, R 2 may be a methyl group, an ethyl group, n-propyl, isopropyl, 1-butyl, 2-butyl, isobutyl, or t-butyl group. 2 may be, for example, a methyl group, an ethyl group, or an n-propyl group. More specifically, R 2 may be, for example, a methyl group.

[0071] In the above Chemical Formula 3, n1 may be, for example, an integer of 1 to 4, an integer of 1 to 3, or an integer of 1 to 2.

[0072] In the above chemical formula 3, R 3 may be, for example, a branched or cyclic alkyl group having 3 to 12 carbon atoms. 3 may be, for example, isopropyl, isobutyl, t-butyl, isopentyl, 1-methyl-1-butyl, 2-methyl-2-butyl, t-pentyl, isohexyl, 1-methyl-1-pentyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, t-hexyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclopropylethyl, cyclobutylethyl, cyclopentylethyl, or cyclohexylethyl. More specifically, R 3 may be, for example, isopropyl, isobutyl, t-butyl, isopentyl, isohexyl, 2,2-dimethyl-1-butyl or 3,3-dimethyl-1-butyl.

[0073] In the above chemical formula 3, R 4 may be, for example, hydrogen, a methyl group, or an ethyl group. More specifically, R 4 may be, for example, hydrogen.

[0074] In the above chemical formula 3, R 5 and R 6 For example, each independently may be a halogen, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. 5 and R 6 may be, for example, each independently fluorine, chlorine, a methyl group, an ethyl group, a methoxy group, or an ethoxy group.

[0075] In the above Chemical Formula 3, n2 and n3 are, for example, each independently an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, an integer of 0 to 1, or 0.

[0076] In the above formula 3, Z is, for example, oxygen, sulfur, or CR. 7 R 8 and R 7 and R 8 are each independently an alkyl group having 1 to 3 carbon atoms. Specifically, Z is, for example, oxygen, sulfur, or a 2,2-propylene group. More specifically, Z is, for example, a 2,2-propylene group.

[0077] The cation-containing compound represented by Chemical Formula 3 can be composed of a cation represented by Chemical Formula 3 and an anion. The type of the anion is not particularly limited, but may be, for example, tetraarylborate. The four aryl groups of the tetraarylborate may be the same or different and may be, for example, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 30 carbon atoms, or a substituted or unsubstituted alkylaryl group having 7 to 30 carbon atoms.

[0078] In this specification, unless otherwise specified, the term "substituted or unsubstituted" means that hydrogen or carbon is substituted with another element. Non-limiting examples include: hydrogen may be substituted with halogen, vinyl group, hydroxy group, alkyl group having 1 to 10 carbon atoms, haloalkyl group having 1 to 10 carbon atoms, or alkoxy group having 1 to 10 carbon atoms; and carbon (-CH-) may be substituted with -O- or -CO-.

[0079] As an example, the tetraarylborate may be at least one anion selected from the group consisting of tetraphenylborate, tetrakis(fluorophenyl)borate, tetrakis(chlorophenyl)borate, tetrakis(methylphenyl)borate, tetrakis(methoxyphenyl)borate, tetrakis(fluoromethylphenyl)borate, tetrakis(fluoromethoxyphenyl), tetrakis(chloromethylphenyl)borate, and tetrakis(chloromethoxyphenyl)borate.

[0080] The blue-region photosensitive dye can be used in sufficient amounts to exhibit excellent optical recording properties, thereby providing a highly transparent holographic recording medium. For example, the blue-region photosensitive dye may be included in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the blue-region photosensitive dye may be, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above ranges are satisfied, a highly transparent holographic recording medium can be provided, while exhibiting superior optical recording properties in the blue region.

[0081] The holographic recording medium according to the embodiment uses a compound having a specific structure as the red-region photosensitive dye, and can exhibit high optical recording properties and transparency.

[0082] The red light-sensitive dye may include, for example, a silicon rhodamine compound represented by the following Chemical Formula 4:

[0083] [ka]

[0084] In the above Chemical Formula 4, R 21 ~R 29 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, d and e each independently represent an integer of 0 to 3; f is an integer from 0 to 5, An - is an anion.

[0085] In the above chemical formula 4, R 21 ~R 28 may each independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. 21 ~R 28 may each independently be an alkyl group having 1 to 6 carbon atoms. More specifically, in the above-mentioned chemical formula 4, R 21 ~R 28 may be a methyl group.

[0086] In the above chemical formula 4, d and e may each independently be an integer of 0 to 2, an integer of 0 to 1, or 0.

[0087] In the above Chemical Formula 4, f may be an integer of 0 to 5, an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, or an integer of 1 to 2.

[0088] In the above chemical formula 4, R 29 may be a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. 29 may be an alkoxy group having 1 to 6 carbon atoms. More specifically, in the above-mentioned chemical formula 4, R 29 may be a methoxy group.

[0089] In the above formula 4, the anion (An - ) may be a halide anion, a cyano anion, a sulfonate anion, an alkoxy anion having 1 to 30 carbon atoms, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0090] Specifically, in the above-mentioned Chemical Formula 4, the anion (An - ) may be a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0091] More specifically, in the above Chemical Formula 4, the anion (An - ) may be an alkylsulfonate anion having 2 to 15 carbon atoms in which one or more hydrogen atoms are substituted or unsubstituted with fluorine, an alkylsulfonate anion having 6 to 30 carbon atoms in which one or more carbon atoms are substituted or unsubstituted with -O- or -CO-, a phenylsulfonate anion substituted or unsubstituted with methyl, or a substituted or unsubstituted tetraarylborate anion. - ) is a dodecyl sulfonate anion, a perfluorobutyl sulfonate anion, a phenyl sulfonate anion, a methyl phenyl sulfonate anion,

[0092] [ka]

[0093] Alternatively, it may be a tetraphenylborate anion.

[0094] The red-region photosensitive dye can be used in sufficient amounts to exhibit excellent optical recording properties, thereby providing a highly transparent holographic recording medium. For example, the red-region photosensitive dye may be included in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the red-region photosensitive dye may be, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the content satisfies this range, a highly transparent holographic recording medium can be provided, while exhibiting excellent optical recording properties in the red region.

[0095] The holographic recording medium according to the embodiment uses a compound having a specific structure as the green region photosensitive dye, and can exhibit high optical recording properties and transparency.

[0096] The green light-sensitive dye may include, for example, one or more compounds selected from the group consisting of a compound represented by the following Chemical Formula 5, a compound represented by the following Chemical Formula 6, thioerythrosine triethylammonium, and a compound represented by erythrosine B:

[0097] [ka]

[0098] In the above Chemical Formula 5, Y is O or S; R 61 ~R 66 are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, R 67 is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, g and h each independently represent an integer of 0 to 3; i is an integer from 0 to 5, Ani -is an anion.

[0099] [ka]

[0100] In the above Chemical Formula 6, R 71 ~R 77 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, Anii - is an anion.

[0101] In the above chemical formula 5, R 61 ~R 66 may each independently be hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. 61 ~R 66 may each independently be a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group. 61 and R 63 is hydrogen and R 62 and R 64 ~R 66 may each independently be a methyl group or an ethyl group.

[0102] In the above chemical formula 5, R 67 may be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. 67 may be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group. 67 may be a methyl group or an ethyl group.

[0103] In the above Chemical Formula 5, g and h may each independently be an integer of 0 to 2, an integer of 1 to 2, or 1.

[0104] In the above Chemical Formula 5, i may be an integer of 0 to 5, an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, or an integer of 1 or 2.

[0105] In the above formula 5, the anion (Ani - ) may be a halide anion, a cyano anion, a sulfonate anion, a bistriflimide anion, an alkoxy anion having 1 to 30 carbon atoms, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0106] Specifically, in the above-mentioned Chemical Formula 5, the anion (Ani - ) may be a halide anion, a bistriflimide anion, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0107] More specifically, in the above Chemical Formula 5, the anion (Ani - ) may be a chloride anion, a bistriflimide anion, an unsubstituted alkylsulfonate anion having 2 to 15 carbon atoms, a methyl-substituted or unsubstituted phenylsulfonate anion, or a substituted or unsubstituted tetraarylborate anion. - ) may be a chloride anion, a bistriflimide anion, a hexylsulfonate anion, a dodecylsulfonate anion, a methylphenylsulfonate anion, or a tetraphenylborate anion.

[0108] In the above chemical formula 6, R 71 ~R 76 may each independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. 71 ~R 76may each independently be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group. 71 ~R 76 may each independently be a methyl group or an ethyl group.

[0109] In the above Chemical Formula 6, the anion (Anii - ) may be a halide anion, a cyano anion, a sulfonate anion, a bistriflimide anion, an alkoxy anion having 1 to 30 carbon atoms, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0110] Specifically, in the above-mentioned Chemical Formula 6, the anion (Anii - ) may be a halide anion, a bistriflimide anion, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0111] More specifically, in the above Chemical Formula 6, - ) may be a halide anion. - ) may be a chloride anion.

[0112] The green-region photosensitive dye can be used in sufficient amounts to exhibit excellent optical recording properties, thereby providing a highly transparent holographic recording medium. For example, the green-region photosensitive dye may be included in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the green-region photosensitive dye may be, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above ranges are satisfied, a highly transparent holographic recording medium can be provided, while exhibiting superior optical recording properties in the green region.

[0113] The coinitiator may be an electron donor, an electron acceptor, or a mixture thereof.

[0114] For example, the coinitiator may include an electron donor, such as a borate anion represented by the following formula 7:

[0115] [Chemical formula 7] BX 1 X 2 X 3 X 4

[0116] In the above chemical formula 7, X 1 ~X 4 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 30 carbon atoms, a substituted or unsubstituted alkylaryl group having 7 to 30 carbon atoms, or a substituted or unsubstituted allyl group, and X 1 ~X 4 At least one of is not an aryl group.

[0117] When the alkyl group having 1 to 20 carbon atoms, the alkenyl group having 2 to 20 carbon atoms, the aryl group having 6 to 30 carbon atoms, the arylalkyl group having 7 to 30 carbon atoms, the alkylaryl group having 7 to 30 carbon atoms or the allyl group is substituted, it may be substituted with one or more selected from the group consisting of halogen, a vinyl group, a haloalkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms.

[0118] Specifically, X 1 ~X 3 are each independently methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, cyclobutyl, cyclopentyl, cyclohexyl, ethenyl, propenyl, phenyl, methylphenyl, methoxyphenyl, naphthyl, methylnaphthyl, or methoxynaphthyl, substituted or unsubstituted with halogen; 4 may be n-butyl, n-pentyl, or n-hexyl. More specifically, the borate anion represented by Chemical Formula 7 may be, for example, a triphenylbutylborate anion.

[0119] The cation bonded to the borate anion does not absorb light and may be an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation refers to an ammonium cation in which nitrogen (N) is substituted with four substituents, and the four substituents may each independently be an alkyl group having 1 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 6 to 40 carbon atoms, or an alkyl group having 2 to 40 carbon atoms linked via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3).

[0120] As the electron donor, for example, commercially available butyryl choline triphenylbutylborate (Borate V, manufactured by Spectra Group) can be used.

[0121] For example, the coinitiator may include an electron acceptor, such as an onium salt, such as a sulfonium salt or an iodonium salt; a triazine compound, such as a tris(trihalomethyl)triazine or a substituted bis(trihalomethyl)triazine; or a mixture thereof.

[0122] Specifically, the electron acceptor may include (4-(octyloxy)phenyl)(phenyl)iodonium salt as an iodonium salt or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine as a triazine compound. The electron acceptor may be, for example, commercially available H-Nu254 (Spectra) or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (TCI).

[0123] The co-initiator may be contained in an amount ranging from 0.05 to 50 parts by weight relative to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the co-initiator content may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more, and the upper limit may be, for example, 30 parts by weight or less. When the above range is satisfied, an appropriate polymerization reaction rate is exhibited, which is advantageous for ensuring the desired optical recording properties.

[0124] The photoinitiator system may contain an additional photoinitiator to remove the color of the photosensitive dye and to react all of the unreacted photoreactive monomers after irradiation with light for recording. Examples of the photoinitiator include acetophenone-based compounds, oxime-based compounds, phosphine oxide-based compounds, thioxanthone-based compounds, benzoate ester-based compounds, imidazole-based compounds, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, amine derivatives, diazonium salts, sulfonium salts, iodonium salts, sulfonate esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl)iron(II), benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosylphthalimide, and mixtures thereof.

[0125] More specifically, examples of the photoinitiator include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (Irgacure 369), 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyloxime) (Irgacure OXE02, BASF), [(Z)-(1-oxo-1-phenylpropan-2-ylidene)amino]benzoate (e.g., TPI-057 or TPI-059 manufactured by TREEEL), and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure TPO), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (Irgacure 1700), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Irgacure 819), 2,4-diethylthioxanthone, 2-chlorothioxanthone, isopropylthioxanthone, diisopropylthioxanthone, ethyl 4-(dimethylamino)benzoate, 1,3-di(t-butyldioxycarbonyl)benzophenone, 3 ,3',4,4''-Tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazoline, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethan-1-one (Irgacure 651), 1-hydroxy-cyclohexyl-phenyl ketone (Irgacure 184), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium (Irgacure 784), Ebecryl P-115 (SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (Dow Chemical Co.Examples include, but are not limited to, Irgacure 264, Irgacure 250 (BASF), CIT-1682 (Nippon Soda), or mixtures thereof.

[0126] The holographic recording medium according to one embodiment may further include a plasticizer. When the photopolymer layer includes a plasticizer, refractive index modulation can be more easily achieved during hologram recording. More specifically, the plasticizer lowers the glass transition temperature of the polymer matrix, improving the fluidity of the photoreactive monomer. The plasticizer has a low refractive index and non-reactive properties, allowing it to be uniformly distributed within the polymer matrix. When the non-photopolymerized photoreactive monomer moves, the plasticizer migrates in the opposite direction, contributing to refractive index modulation. The plasticizer also contributes to improving the moldability of the photopolymer composition.

[0127] The photopolymer layer may contain a fluorine-based compound as such a plasticizer.

[0128] The fluorine-based compound may have a low refractive index of 1.45 or less to perform the function of the plasticizer. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less, and the lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. By using a fluorine-based compound having a refractive index lower than that of the photoreactive monomer, the refractive index of the polymer matrix can be lowered and the refractive index modulation with the photoreactive monomer can be increased.

[0129] The fluorine-based compound may contain, for example, one or more functional groups selected from the group consisting of an ether group, an ester group, and an amide group, and two or more difluoromethylene groups. More specifically, the fluorine-based compound may be, for example, a compound containing a repeating unit represented by the following chemical formula 8:

[0130] [ka]

[0131] In the above Chemical Formula 8, Multiple R 31 ~R 34 are each independently hydrogen or fluorine, and at least R 31 ~R 34 is fluorine, and m is an integer of 2 to 12.

[0132] More specifically, the fluorine-based compound may be a compound containing 1 to 3 units represented by the following chemical formula 8-1.

[0133] [ka]

[0134] In the above chemical formula 8-1, R 41 ~R 44 and R 53 ~R 56 are each independently hydrogen or fluorine, and R 45 ~R 52 is fluorine.

[0135] As an example, in the above-mentioned chemical formula 8-1, R 41 , R 42 , R 55 and R 56 is hydrogen and R 43 ~R 54 is fluorine.

[0136] The fluorine-based compound containing (repeating) units represented by Formulas 8 and 8-1 is not particularly limited, but may be capped with an end capping agent widely used in the related art. For example, the end of the fluorine-based compound containing (repeating) units represented by Formulas 8 and 8-1 may be an alkyl group or an alkyl group substituted with one or more alkoxy groups. As a non-limiting example, when 2-methoxyethoxymethyl chloride is used as an end capping agent, the end of the fluorine-based compound containing (repeating) units represented by Formulas 8 and 8-1 may be a 2-methoxyethoxymethyl group.

[0137] The fluorine-based compound may have a weight-average molecular weight of 300 or more. Specifically, the lower limit of the weight-average molecular weight of the fluorine-based compound may be, for example, 350 or more, 400 or more, 450 or more, 500 or more, or 550 or more, and the upper limit may be, for example, 1000 or less, 900 or less, 800 or less, 700 or less, or 600 or less. It is preferable to satisfy the above weight-average molecular weight range when considering refractive index modulation, compatibility with other components, and elution issues of the fluorine-based compound. Here, the weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene measured by the GPC method as described above.

[0138] The photopolymer layer may contain 20 to 200 parts by weight of the fluorine-based compound per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the fluorine-based compound may be, for example, 25 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, or 80 parts by weight or more, and the upper limit may be, for example, 190 parts by weight or less, 180 parts by weight or less, 170 parts by weight or less, 160 parts by weight or less, or 150 parts by weight or less. When the content satisfies this range, a fluorine-based compound with a sufficiently low refractive index can exhibit a large refractive index modulation value after recording, advantageously ensuring excellent optical recording properties, without problems such as poor compatibility with components contained in the photopolymer layer, causing some of the fluorine-based compound to leach out to the surface of the photopolymer layer, or causing poor haze.

[0139] The holographic recording medium of the embodiment may further include an additive such as a surfactant or an antifoaming agent.

[0140] Examples of the surfactant include silicone surfactants, fluorine surfactants, and mixtures thereof.

[0141] Examples of the silicone surfactant that can be used include BYK-077, BYK-085, BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-320, BYK-322, BYK-323, BYK-325, BYK-330, BYK-331, BYK-333, BYK-335, BYK-341v344, BYK-345v346, BYK-348, BYK-354, BYK355, BYK-356, BYK-358, BYK-361, BYK-370, BYK-371, BYK-375, BYK-380, BYK-390, and BYK-3550, all of which are manufactured by BYK Chemie. Examples of the fluorine-based surfactant include F-114, F-177, F-410, F-411, F-450, F-493, F-494, F-443, F-444, F-445, F-446, F-470, F-471, F-472SF, F-474, F-475, F-477, F-478, F-479, F-480SF, F-482, F-483, F-484, F-485, F-486, F-487, F-488, F-489, F-481, F-482SF, F-483, F-484, F-485, F-486, F-487, F-488, F-489, F-489, F-481SF ...90SF, F-491, F-492SF, F-493, F-494, F-495, F-496, F-497, F-498, F-499, F-500SF, F-501SF, F-502SF, F -486, F-487, F-172D, MCF-350SF, TF-1025SF, TF-1117SF, TF-1026SF, TF-1128, TF-1127, TF1129, TF-1126, TF-1130, TF-1116SF, TF-1131, TF1132, TF1027SF, TF-1441, TF-1442, etc. can be used.

[0142] If the holographic recording medium of the embodiment includes a surfactant, the surfactant may be present in an amount of at least 0.01 parts by weight, at least 0.02 parts by weight, at least 0.03 parts by weight, at least 0.05 parts by weight, and at most 5 parts by weight, or at most 3 parts by weight, per 100 parts by weight of the polymer matrix. When the surfactant is present in this range, excellent adhesion and releasability can be imparted to the photopolymer layer, thereby preserving excellent optical recording properties.

[0143] The holographic recording medium of the embodiment may include a silicone-based reactive additive as an antifoaming agent. Examples of the silicone-based reactive additive include commercially available products such as Tego Rad 2500. The content of the antifoaming agent can be appropriately adjusted to a level that does not interfere with the function of the holographic recording medium.

[0144] The photopolymer layer may be formed from a photopolymer composition that includes a solvent.

[0145] The solvent may be an organic solvent, and may be, for example, one or more organic solvents selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited thereto. Specific examples of such organic solvents include one or more selected from the group consisting of ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, and t-butanol; acetates such as ethyl acetate, i-propyl acetate, and polyethylene glycol monomethyl ether acetate; and ethers such as tetrahydrofuran and propylene glycol monomethyl ether.

[0146] The organic solvent may be added when the components of the photopolymer composition are mixed together, or the components may be added in a dispersed or mixed state in the organic solvent and then added to the photopolymer composition.

[0147] The photopolymer composition may contain a solvent so that the solids concentration is 1 to 90 wt %. Specifically, the photopolymer composition may contain a solvent so that the solids concentration is 20 wt % or more or 30 wt % or more and 85 wt % or less, 80 wt % or less, 75 wt % or less, or 70 wt % or less. Within these ranges, the photopolymer composition exhibits appropriate flowability, can form a coating film without defects such as streaks, and can form a photopolymer layer with desired physical properties and surface characteristics without defects during the drying and curing process.

[0148] The holographic recording medium of the embodiment may further include a substrate on at least one surface of the photopolymer layer. The type of substrate is not particularly limited, and any substrate known in the related art may be used. For example, substrates such as glass, polyethylene terephthalate (PET), triacetyl cellulose (TAC), polycarbonate (PC), and cycloolefin polymer (COP) may be used.

[0149] The holographic recording medium of the embodiment has excellent refractive index modulation, diffraction efficiency, and driving reliability despite having a thin photopolymer layer.

[0150] The thickness of the photopolymer layer may be, for example, in the range of 5.0 to 40.0 μm. Specifically, the lower limit of the thickness of the photopolymer layer may be, for example, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more. The upper limit of the thickness may be, for example, 35 μm or less, 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, 25 μm or less, 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, 19 μm or less, or 18 μm or less.

[0151] The holographic recording medium of the embodiment can achieve a refractive index modulation value (Δn) of 0.020 or more, 0.025 or more, 0.026 or more, 0.027 or more, 0.028 or more, 0.029 or more, 0.030 or more, 0.031 or more, 0.032 or more, 0.033 or more, 0.034 or more, or 0.035 or more, even when the photopolymer layer is as thin as 5 to 30 μm. The upper limit of the refractive index modulation value is not particularly limited, but may be, for example, 0.060 or less.

[0152] The holographic recording medium of the embodiment can record optical information in the red, green, and blue regions, while exhibiting very high transparency.

[0153] Specifically, the holographic recording medium of the embodiment can satisfy the following formulas 1 and 2.

[0154] [Formula 1] T avg ≧90%

[0155] In the above formula 1, T avg is the average transmittance measured in the region of 400 to 700 nm for the photopolymer layer that has been photobleached in a state where no optical information has been recorded.

[0156]

number

[0157] In the above formula 2, ΔE is the color difference between a sample obtained by photobleaching the photopolymer layer without recording optical information and a white light having the same brightness as the photopolymer layer; L S * , a S * and b S * is the color value of the Lab color coordinate system derived from the transmission spectrum of the photobleached sample in the region of 400 to 700 nm, standard illuminant D65, and a viewing angle of 10°, and LR * , a R * and b R * is the color value of the white light in the Lab color coordinate system.

[0158] T in the above formula 1 avg is the average transmittance of the photobleached photopolymer layer in the visible light region (400 to 700 nm region) before recording. avg When T in the above formula 1 is 90% or more, it means that the photopolymer layer has a high transmittance in the visible light region and is very transparent. avg may be, for example, 90.0% or more, 90.1% or more, 90.2% or more, 90.3% or more, or 90.4% or more. avg The upper limit is not particularly limited, and may be 100% or less or 98% or less.

[0159] ΔE in the above formula 2 is the color difference in the visible light region (400 to 700 nm) between the photobleached photopolymer layer before recording and the reference sample. In the above formula 2, ΔE is the color difference in the visible light region (400 to 700 nm) between the photobleached photopolymer layer before recording and the reference sample. R * =L S * , a R * and b R * =0).

[0160] The low ΔE means that the red, green, and blue light rays pass through the holographic recording medium evenly without being biased to one side, so that the color of the image seen through the holographic recording medium is not significantly different from the actual color (the originally intended color). Therefore, the holographic recording medium of the present embodiment has a ΔE of 2.5 or less in the above formula 2, thereby providing a holographic image with dynamism, three-dimensionality, realism, and visibility.

[0161] ΔE in the above formula 2 may be, for example, 2.50 or less, 2.40 or less, 2.30 or less, 2.20 or less, 2.10 or less, 2.00 or less, 1.95 or less, or 1.90 or less. The lower limit of ΔE in the above formula 2 is not particularly limited, and may be 0 or more or 0.5 or more.

[0162] The holographic recording medium of the embodiment is not limited to this, but may be one in which a reflection hologram or a transmission hologram is recorded.

[0163] The holographic recording medium of the embodiment may have a notch filter structure in relation to the diffraction grating structure. The notch filter structure of the holographic recording medium of the embodiment may mean, for example, that the diffraction grating is non-slanted (substantially 0°) relative to the substrate surface, i.e., parallel to the substrate surface. Such a holographic recording medium may have a structure in which two layers with different refractive indices (e.g., a high refractive index layer and a low refractive index layer) are alternately repeated. The two repeated layers may have the same or different thicknesses. Such a non-slanted diffraction grating recording may be fabricated by making the angles of incidence of the incident object beam and reference beam equal relative to the normal. The non-slanted structure exhibits a clearer degree of deformation (e.g., contraction or expansion) under high temperature and high humidity conditions than the slanted structure, and is less susceptible to the contraction and expansion of the substrate.

[0164] The holographic recording medium of the present embodiment can record optical information in the red (R), green (G), and blue (B) regions (hereinafter referred to as the RGB region). When all optical information in the RGB region is recorded, a full-color holographic image can be reproduced. The holographic recording medium of the present embodiment exhibits high diffraction efficiency in the entire RGB region, thereby enabling reproduction of vivid and realistic full-color holographic images.

[0165] Specifically, when the photopolymer layer is irradiated with light in the red, green, and blue regions to record a notch filter hologram, the total diffraction efficiency in the RGB region may be 150% or more. The diffraction efficiency may be a value calculated by Equation 8 described in the test example below for a holographic recording medium in which a notch filter hologram is recorded in a photopolymer layer having a thickness of 5 to 30 μm.

[0166] The diffraction efficiency of the red (R) region, the diffraction efficiency of the green (G) region, and the diffraction efficiency of the blue (B) region refer to the diffraction efficiencies at the recording wavelengths of the red (R), green (G), and blue (B) regions, respectively. The total diffraction efficiency of the RGB regions is calculated by calculating the diffraction efficiency (unit: %) for each of the RGB regions and then adding up the diffraction efficiencies of the three regions, and is expressed in %. Theoretically, the total diffraction efficiency of the RGB regions has a numerical range of 0% to 300%.

[0167] In the holographic recording medium according to the embodiment, the total diffraction efficiency of the RGB regions may be, for example, 150% or more, 160% or more, 170% or more, 180% or more, or 190% or more, and the upper limit is not particularly limited, but may be 300% or less or 250% or less.

[0168] However, the present invention is not limited thereto, and optical information can be recorded by irradiating the holographic recording medium with light in one or two regions selected from the red (R), green (G), and blue (B) regions depending on the intended use of the holographic recording medium. As a non-limiting example, the holographic recording medium of the embodiment has high visibility and can be used to reproduce holographic images such as letters. In this case, optical information can be recorded by irradiating the holographic recording medium with light in only one region selected from the red (R), green (G), and blue (B) regions.

[0169] For example, when the photopolymer layer is irradiated with light in the red (R), green (G), or blue (B) region alone to record a notch filter hologram, the diffraction efficiency in the red (R), green (G), or blue (B) region may be 80% or more.

[0170] In this specification, recording optical information by irradiating a single region of light selected from the red (R), green (G), or blue (B) regions is referred to as “single recording,” and the diffraction efficiency measured in this case is referred to as “diffraction efficiency during single recording.” The diffraction efficiency during single recording can be a value calculated using Equation 8 described in the test example below for a holographic recording medium in which a notch filter hologram is recorded in a photopolymer layer with a thickness of 5 to 30 μm.

[0171] The lower limit of the diffraction efficiency during single recording may be, for example, 80% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90% or more, and the upper limit is not particularly limited, but may be 100% or less or 99% or less.

[0172] As an example, in the holographic recording medium of the embodiment, when three unrecorded holographic recording media of the same type are irradiated with light in the red (R), green (G), and blue (B) regions to record optical information individually, the diffraction efficiency of each region can all satisfy the above range.

[0173] The holographic recording medium of the embodiment satisfies the above formulas 1 and 2 and exhibits excellent diffraction efficiency throughout the RGB range. This means that even when a holographic image is reproduced in space through the holographic recording medium, the holographic recording medium is invisible, and the holographic image can be reproduced vividly and realistically in the void, demonstrating extremely excellent visibility.

[0174] The holographic recording medium of the embodiment can record optical information in the red, green, and blue regions while exhibiting very high temperature stability. Specifically, the holographic recording medium of the embodiment can exhibit excellent high temperature stability even after recording. More specifically, the holographic recording medium of the embodiment can satisfy the following formula 3:

[0175] [Formula 3] △T 400 =T 400 a -T 400 b ≦10%p

[0176] In the above formula 3, T 400 a is the initial transmittance measured at 400 nm for the photopolymer layer that has been photobleached with optical information recorded thereon; T 400 b is the transmittance measured at 400 nm after the photopolymer layer whose initial transmittance has been measured is exposed to 120° C. for 500 hours.

[0177] △T in the above formula 3 400 is an index that can confirm the high-temperature stability of the photopolymer layer, and is the difference (variation) in transmittance before and after exposure to high temperatures.

[0178] The holographic recording medium of the embodiment can exhibit excellent high-temperature stability even when optical information is recorded by irradiating light in one or two regions selected from the red (R), green (G), and blue (B) regions, or when optical information in all of the RGB regions is recorded.

[0179] △T in the above formula 3 400 That the transmittance is 10%p or less means that the photopolymer layer has excellent thermal stability and the change in transmittance before and after exposure to high temperatures is not large.

[0180] △T in the above formula 3 400may be, for example, 10.0%p or less, 9.5%p or less, 9.0%p or less, 8.5%p or less, 8.3%p or less, 8.0%p or less, 7.8%p or less, or 7.5%p or less. 400 The lower limit is not particularly limited, and may be 0%p or more or 0.5%p or more.

[0181] The holographic recording medium of the embodiment can maintain excellent optical recording properties and exhibit high reliability even when exposed to high temperatures for a long period of time.

[0182] As an example, the holographic recording medium of the embodiment may have a diffraction efficiency maintenance rate of 80% or more, calculated by the following formula 4.

[0183] [Formula 4] Diffraction efficiency maintenance rate (%) = 100 × DE b / DE a

[0184] In the above formula 4, DE a is the diffraction efficiency in the recording wavelength region measured by irradiating the holographic recording medium with light in one or more regions selected from red, green, and blue regions to record a notch filter hologram, or is the sum of these values; DE b is the diffraction efficiency in the recording wavelength region measured after leaving the recorded hologram recording medium at 120° C. for 500 hours, or is the sum of these values.

[0185] When measuring the diffraction efficiency maintenance rate, if optical information is recorded by irradiating the holographic recording medium with light in one of the red (R), green (G) and blue (B) regions, the diffraction efficiency in the corresponding recording wavelength region is measured as DE. a and D.E. b If optical information is recorded by irradiating the holographic recording medium with light in two or more of the red (R), green (G), and blue (B) regions, the sum of the diffraction efficiencies in the relevant recording wavelength region is DE a and D.E. bFor a detailed method of measuring the diffraction efficiency maintenance rate, the method described in the test examples below can be referred to.

[0186] The diffraction efficiency maintenance rate may be, for example, 80% or more, 85% or more, 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more. The upper limit of the diffraction efficiency maintenance rate is not particularly limited and may be 100% or less. Due to measurement error or equipment deviation, the diffraction efficiency after long-term storage may be higher than the diffraction efficiency before long-term storage. In this case, the diffraction efficiency maintenance rate after long-term storage is considered to be 100%.

[0187] The use of the holographic recording medium according to the embodiment is not particularly limited. For example, the holographic recording medium may be used in smart devices such as mobile devices, components of wearable displays, or components for automobiles (e.g., head-up displays).

[0188] Meanwhile, according to another embodiment of the present invention, there is provided a method for manufacturing a holographic recording medium, comprising the step of forming a photopolymer layer by applying a photopolymer composition including a polymer matrix or its precursor, a photoreactive monomer, and a photoinitiator system, wherein the photoinitiator system includes a photosensitive dye and a coinitiator, and the photosensitive dyes include a red-region photosensitive dye, a green-region photosensitive dye, and a blue-region photosensitive dye, and the photopolymer layer satisfies the above formulas 1 and 2.

[0189] The photopolymer composition may be a photopolymer composition for forming a photopolymer layer of the holographic recording medium of one embodiment described above, and its constituent components have been described in detail above, so a detailed description will be omitted here.

[0190] In the step of forming the photopolymer layer, a photopolymer composition having the above-described structure can be first prepared. When preparing the photopolymer composition, a commonly known mixer, agitator, or mixer can be used without any limitation to mix the components. This mixing process can be carried out at a temperature ranging from 0°C to 100°C, from 10°C to 80°C, or from 20°C to 60°C.

[0191] In the step of forming the photopolymer layer, a prepared photopolymer composition may be applied to form a coating film formed from the photopolymer composition. The coating film may be dried naturally at room temperature or at a temperature ranging from 30 to 80°C. This process may induce a hydrosilylation reaction between the remaining unreacted hydroxyl groups of the acrylic polyol and the silane functional groups of the siloxane polymer.

[0192] The photopolymer layer manufactured by the step of forming the photopolymer layer may have a photoreactive monomer, a photosensitive dye, a coinitiator, and optional additives uniformly dispersed in a crosslinked polymer matrix.

[0193] The method for manufacturing a holographic recording medium according to another embodiment may include, after forming a photopolymer layer, irradiating a predetermined region of the photopolymer layer with a coherent laser to selectively polymerize photoreactive monomers contained in the photopolymer layer, thereby recording optical information.

[0194] When a coherent laser is irradiated onto the photopolymer layer during the optical information recording step, polymerization of the photoreactive monomer occurs in regions where constructive interference occurs, forming a photopolymer, while polymerization of the photoreactive monomer does not occur or is suppressed in regions where destructive interference occurs, leaving the photoreactive monomer. The unreacted photoreactive monomer then diffuses into the photopolymer where the concentration of the photoreactive monomer is low, causing refractive index modulation, which in turn produces a diffraction grating. As a result, a hologram, i.e., optical information, is recorded in the photopolymer layer having the diffraction grating.

[0195] In another embodiment, the method for manufacturing a holographic recording medium may further include, after the step of recording optical information, a step of photobleaching by irradiating light entirely onto the photopolymer layer on which the optical information is recorded.

[0196] In the photo-bleaching step, ultraviolet light is irradiated onto the photopolymer layer on which optical information is recorded, thereby terminating the reaction of the photoreactive monomer remaining in the photopolymer layer and removing the color of the photosensitive dye. For example, in the photo-bleaching step, ultraviolet light (UVA) in the range of 320 to 400 nm is irradiated to terminate the reaction of the photoreactive monomer and remove the color of the photosensitive dye.

[0197] Meanwhile, according to still another embodiment of the present invention, there is provided an optical element including the holographic recording medium.

[0198] Specific examples of the optical element include smart devices such as mobile devices, components of wearable displays, vehicle accessories (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffraction members, light guides, waveguides, holographic optical elements having the functions of projection screens and / or masks, media and light diffusion plates in optical memory systems, optical wavelength splitters, reflective and transmissive color filters, etc.

[0199] An example of an optical element including the hologram recording medium is a hologram display device, which includes a light source unit, an input unit, an optical system, and a display unit.

[0200] Specifically, the light source unit is a part that emits a laser beam used to provide, record and reproduce three-dimensional image information of an object in the input unit and display unit.

[0201] The input unit is a part that inputs 3D image information of an object to be recorded on the display unit in advance. Specifically, it is a part that can input 3D information of an object, such as spatial light intensity and phase, into an electrically addressed liquid crystal SLM, and can use an input beam at this time.

[0202] The optical system may be composed of mirrors, polarizers, beam splitters, beam shutters, lenses, etc. The optical system can split the laser beam emitted from the light source unit into an input beam sent to the input unit, a recording beam sent to the display unit, a reference beam, an erase beam, a read beam, etc.

[0203] The display unit receives 3D image information of an object from the input unit, records it on a hologram plate consisting of an optically addressed SLM (SLM), and reproduces the 3D image of the object. The 3D image information of the object can be recorded by interference between an input beam and a reference beam. The 3D image information of the object recorded on the hologram plate can be reproduced as a 3D image by a diffraction pattern generated by a read beam, and an erase beam can be used to quickly remove the formed diffraction pattern. Meanwhile, the hologram plate can be moved between a position where the 3D image is input and a position where it is reproduced. [Effects of the Invention]

[0204] The holographic recording medium according to one embodiment of the invention has excellent diffraction efficiency and transparency, so that even when a holographic image is reproduced in space through the holographic recording medium, the holographic recording medium is invisible, and the holographic image can be reproduced in the void in a vivid and realistic manner, demonstrating excellent visibility. [Brief explanation of the drawings]

[0205] [Figure 1] 1 is a schematic diagram showing the setup of a recording device for hologram recording. Specifically, Fig. 1 shows the process in which a laser beam of a predetermined wavelength is emitted from a light source 10, and then passes through mirrors 20, 20', an iris 30, a spatial filter 40, an iris 30', a collimation lens 50, and a polarized beam splitter (PBS) 60 before being irradiated onto a hologram recording medium (PP) 80 positioned on one side of a mirror 70. [Figure 2] 10 is a graph showing the transmittance in the visible light region of the holographic recording medium manufactured in Example 2. [Figure 3] 10 is a graph showing the diffraction efficiency (DE) as a function of wavelength (W / L) when full-color optical information is recorded on the holographic recording medium manufactured in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0206] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, but these are presented as examples of the present invention and do not limit the scope of the invention in any way.

[0207] In the following Production Examples, Examples, Comparative Examples, etc., the contents of raw materials and the like refer to the contents on a solid basis unless otherwise specified.

[0208] Production Example 1: Production of acrylic polyol A 2L jacketed reactor was charged with 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60-70°C and stirring was continued for 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added and stirring was continued for another 30 minutes. 0.24g of polymerization initiator AIBN was then added and polymerization was continued for at least 4 hours at the reaction temperature until the residual acrylate content was less than 1%. This produced an acrylate copolymer with hydroxyl groups located in the branched chain (weight average molecular weight approximately 300,000, OH equivalent approximately 1802g / equivalent).

[0209] Production Example 2: Production of Fluorine-Based Compounds A 1000 mL flask was charged with 20.51 g of 2,2'-{oxybis[(1,1,2,2-tetrafluoroethane-2,1-diyl)oxy]}bis(2,2-difluoroethan-1-ol) and dissolved in 500 g of tetrahydrofuran. While stirring at 0°C, 4.40 g of sodium hydride (60% dispersion in mineral oil) was carefully added over several times. After stirring at 0°C for 20 minutes, 12.50 mL of 2-methoxyethoxymethyl chloride was slowly added dropwise. After confirming the complete consumption of the reactants by 1H NMR, work-up using dichloromethane yielded 29g of a liquid product with a purity of over 95% in 98% yield. The weight-average molecular weight of the produced fluorine-based compound was 586, and the refractive index measured with an Abbe refractometer was 1.361.

[0210] Example 1: Preparation of photopolymer composition and holographic recording medium (1) Preparation of photopolymer composition A mixture was prepared by first mixing 0.57 g of a siloxane polymer, poly(methylhydrosiloxane) (Sigma-Aldrich, number average molecular weight: approximately 590, Si-H equivalent: approximately 103 g / equivalent), and 33.4 g of the acrylic polyol (solid content: 10.02 g) with a solid content of 30 wt% prepared in Preparation Example 1 (SiH / OH molar ratio = 1.0).

[0211] To the mixture were added 0.11 g of a compound represented by the following formula A-1 (blue) as a photosensitive dye, 0.11 g of a compound represented by the following formula B (red), and 0.10 g of rhodamine 6G (green) as a photosensitive dye, 13.5 g of the fluorine-based compound prepared in Preparation Example 2 as a plasticizer, 0.10 g of Tego Rad 2500 as a silicone-based reactive additive, and methyl isobutyl ketone and methyl ethyl ketone as solvents, and the mixture was stirred in a paste mixer for about 10 minutes in the dark. A Karstedt (Pt-based) catalyst was added to the mixture for matrix crosslinking.

[0212] To the mixture, 16.9 g of HR6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 1.0 g of Borate V as an electron donor coinitiator, and 0.53 g of Irgacure 819 as a photoinitiator were added, and the mixture was stirred for 5 minutes or more to prepare a photopolymer composition.

[0213] [ka]

[0214] (2) Manufacturing of holographic recording media The photopolymer composition was coated to a predetermined thickness on a 60 μm thick TAC substrate using a Mayer bar and dried within 30 minutes at 60° C. After drying, the thickness of the photopolymer layer was approximately 15 μm.

[0215] Example 2 and Comparative Examples 1 to 6: Production of photopolymer compositions and holographic recording media Photopolymer compositions and holographic recording media were produced using the same methods as in Example 1, except that the photosensitive dyes were changed as shown in Table 1 below.

[0216] [Table 1A] [Table 1B]

[0217] Test example 1: Performance evaluation of holographic recording media (1) Average transmittance in visible light region (T avg , %) A holographic recording medium without optical information recorded thereon (hereinafter referred to as a pre-recorded sample) was subjected to photo-bleaching, and then the transmittance in the visible light region (wavelength region of 400 to 700 nm) was measured.

[0218] Specifically, the unrecorded sample was irradiated with ultraviolet (UV) and a white LED to obtain a photobleached sample. The transmittance of the photobleached sample was measured in the 400-700 nm region using a UV-Vis spectrometer.

[0219] The average value of the transmittance measured in the range of 400 to 700 nm was calculated and defined as the average transmittance in the visible light range.

[0220] The transmittance in the visible light region of the holographic recording medium manufactured in Example 2 is shown in FIG.

[0221] (2) Color difference (△E) The transmittance of the photobleached sample in the visible light region (wavelength region of 400 to 700 nm) was measured in the same manner as in the method for measuring the average transmittance in the visible light region, to obtain a transmission spectrum.

[0222] The tristimulus values ​​(X, Y, Z) in the CIE XYZ color space were calculated from the transmission spectrum of the photobleached sample. The tristimulus values ​​were calculated using Equation 5 below.

[0223]

number

[0224] In the above formula 5, S(λ) is the output distribution function of the standard light source (D65),

[0225]

number

[0226] is the color correspondence function in the CIE XYZ color space at a viewing angle of 10°,

[0227]

number

[0228] is the transmission distribution function (transmission spectrum) of the photobleached sample, and λ is the wavelength.

[0229] The trichromatic stimulus values ​​calculated by the above formula 5 are converted into L in the CIE Lab color space by the following formula 6. * , a * , b * converted to a value.

[0230]

number

[0231] In the above formula 6, X n , Y n and Z n has values ​​of 94.71, 100.00, and 107.08 for standard illuminant (D65) and a viewing angle of 10°, respectively, and t is X / X n , Y / Y n or Z / Z n is.

[0232] L calculated using the above formula 6 * , a * , b * was substituted into the following equation 7 to determine the color difference (ΔE).

[0233]

number

[0234] In the above formula 7, L S * , a S * and b S * is the value of the target sample for which color difference is to be measured, and L R * , a R * and b R * is the value of the reference sample.

[0235] In this test example, the reference sample is set to the same brightness (L * ), and assume white light with R * L S * By being identical to (L S * -L R * ) 2 is 0, and a R * and b R * is also 0.

[0236] The low ΔE means that the red, green, and blue light rays pass through the holographic recording medium evenly without being biased to one side, so that the color of the image seen through the holographic recording medium is not significantly different from the actual color (the originally intended color).

[0237] (3) Diffraction efficiency (DE) a) Full-color optical information recording (simultaneous recording) A diffraction grating was recorded using the setup shown in Figure 1. Specifically, the fabricated photopolymer layer was laminated onto a mirror, and then irradiated with a laser. This allowed the recording of a notch filter hologram with periodic refractive index modulation in the thickness direction due to interference between the incident light (L) and the light (L') reflected by the mirror.

[0238] For full-color optical information recording, lasers with wavelengths of 640 nm (red), 532 nm (green), and 460 nm (blue) were used to simultaneously irradiate the media with light of these wavelengths. The incident angle was 0°, and the total laser intensity of each wavelength was 1.5 mW / cm. 2 A notch filter hologram was recorded with a light exposure time of 30 seconds. After recording the hologram, the sample was irradiated with ultraviolet (UV) and a white LED to obtain a photobleached sample after recording. Notch filters and Bragg reflectors are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indices are repeatedly stacked at a fixed thickness.

[0239] b) Solo record Optical information was recorded in the same manner as for recording full-color optical information, except that optical information was recorded independently using a laser in only one region selected from the red, green, and blue regions. In other words, holographic recording media in which three types of optical information were independently recorded were manufactured for each type of holographic recording medium manufactured in the examples and comparative examples.

[0240] c) Measurement of diffraction efficiency After recording, the diffraction efficiency (DE) of the sample was calculated using the following formula 8.

[0241] [Formula 8] DE X_λ (%)={(T0-T m ) / T0}×100

[0242] In the above formula 8, X is represented by F when light in the red, green, and blue regions is irradiated simultaneously in the recording method, and by S when light in the red, green, or blue region is irradiated alone. λ is a recording wavelength region, which is one of the red region (RED), green region (GREEN), and blue region (BLUE), DE X_λ is the diffraction efficiency in the recording wavelength region of the sample recorded by the X method, T0 is the transmittance in the recording wavelength region of the unrecorded sample after photobleaching, and T m is the transmittance of the photobleached sample after recording in the recording wavelength region.

[0243] [Table 2]

[0244] In Table 2, ΣDE means the total diffraction efficiency of the red, green and blue regions of a holographic recording medium in which full-color optical information is recorded.

[0245] Referring to Table 2 above, it can be seen that in Examples 1 and 2, the photo-bleached samples exhibit high transmittance and low color difference in the visible light region, providing a holographic recording medium capable of recording full-color optical information and having colorless and transparent optical properties.

[0246] The diffraction efficiency (DE) as a function of wavelength (W / L) when full-color optical information was recorded on the holographic recording medium manufactured in Example 2 is shown in Figure 3. Referring to Table 2 and Figure 3, it can be seen that Examples 1 and 2 exhibit excellent optical recording characteristics in all of the red, green, and blue regions, not only when optical information was recorded alone but also when full-color optical information was recorded.

[0247] In contrast, Comparative Example 1 showed poor diffraction efficiency in the red region, Comparative Examples 2 and 3 showed poor diffraction efficiency in the green region, and Comparative Examples 4 to 6 showed poor diffraction efficiency in the blue region. Furthermore, in Comparative Examples 1 to 6, the photo-bleached samples showed low transmittance and high color difference in the visible light region, confirming that it is difficult to provide a colorless and transparent holographic recording medium capable of recording full-color optical information.

[0248] This confirms that the holographic recording medium according to one embodiment of the present invention has excellent diffraction efficiency in all of the red, green and blue regions, is capable of recording full-color optical information, and exhibits colorless and transparent optical properties.

[0249] Test Example 2: Evaluation of high temperature stability of holographic recording media To confirm the high-temperature stability (reliability) of the recorded sample, the difference in physical properties before and after exposing the recorded sample to a high-temperature environment was confirmed.

[0250] (1) Measurement of initial physical properties i) Initial transmittance (T 400 a ) measurement Before exposure to a high-temperature environment, the full-color optical information was recorded and the photobleached sample was measured for initial transmittance (T) at 400 nm using a UV-Vis spectrometer. 400 a ) was measured.

[0251] ii) Initial diffraction efficiency (DE a ) measurement Before exposure to a high-temperature environment, the diffraction efficiency of the sample that had recorded full-color optical information and was photobleached was calculated using the above formula 8. Specifically, the diffraction efficiency in the red region, the diffraction efficiency in the green region, and the diffraction efficiency in the blue region were calculated, and these were summed to obtain the initial diffraction efficiency (DE a ) was established.

[0252] (2) Measurement of physical properties after exposure to high temperature environments The photopolymer layer of the sample, which had been recorded with full-color optical information and photobleached, was laminated onto glass using OCA (Optically Clear Adhesive) and then stored at 120°C for 500 hours.

[0253] i) Transmittance variation (△T 400 %p) Using a UV-Vis spectrometer, the transmittance at 400 nm (T) of the photobleached sample after recording exposed to a high-temperature environment was measured. 400 b The transmittance (initial transmittance, T400) measured before exposure to a high temperature environment was a ) and the transmittance (T 400 b ) and the difference (T 400 a -T 400 b ) and transmittance mutation (△T 400 ) was established.

[0254] ii) Diffraction efficiency maintenance rate (%) The diffraction efficiency (DE) was measured for the photobleached sample after exposure to a high-temperature environment using the same method as the initial diffraction efficiency measurement method described above. b ) was measured.

[0255] The diffraction efficiency measured before exposure to a high-temperature environment (initial diffraction efficiency, DE a ) versus the diffraction efficiency (DE) measured after exposure to a high temperature environment. b ) was defined as the diffraction efficiency maintenance rate (DE maintenance rate, %) and calculated using the following formula 4.

[0256] [Formula 4] Diffraction efficiency maintenance rate (%) = 100 × DE b / DE a

[0257] In the above formula 4, DE ais the diffraction efficiency in the recording wavelength region measured by irradiating the holographic recording medium with light in one or more regions selected from red, green, and blue regions to record a notch filter hologram, or is the sum of these values; DE b is the diffraction efficiency in the recording wavelength region measured after leaving the recorded hologram recording medium at 120° C. for 500 hours, or is the sum of these values.

[0258] [Table 3]

[0259] Referring to Table 3, it can be seen that in Examples 1 and 2, even when exposed to high temperatures for a long time, the variation in transmittance is small and the maintenance rate of diffraction efficiency is excellent.

[0260] In contrast, it was confirmed that in Comparative Examples 4 to 6, when exposed to high temperatures, the transmittance varied greatly and the diffraction efficiency maintenance rate decreased significantly.

[0261] As a result, it has been confirmed that the holographic recording medium according to one embodiment of the invention is capable of recording full-color optical information, has excellent optical recording characteristics and transparent optical characteristics, and that these characteristics are well maintained even after prolonged exposure to high temperatures, resulting in high high-temperature reliability.

Claims

1. a polymeric matrix or a precursor thereof; and a photopolymer layer comprising a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; the photoinitiator system comprises a photosensitive dye and a coinitiator; The photosensitive dyes include a red-region photosensitive dye, a green-region photosensitive dye, and a blue-region photosensitive dye; A holographic recording medium that satisfies the following formulas 1 and 2: [Formula 1] T ａｖｇ ≧90% In the above formula 1, T ａｖｇ is the average transmittance measured in the 400 to 700 nm region for the photopolymer layer that has been photobleached without any optical information recorded thereon; [Equation 1] In the above formula 2, ΔE is the color difference between a sample obtained by photobleaching the photopolymer layer without recording optical information and a white light having the same brightness as the photopolymer layer; L Ｓ ＊ , a Ｓ ＊ and b Ｓ ＊ is the color value in the Lab color coordinate system derived from the transmission spectrum of the photobleached sample in the region of 400 to 700 nm, standard illuminant D65, and a viewing angle of 10°; L Ｒ ＊ , a Ｒ ＊ and b Ｒ ＊ is the color value of the white light in the Lab color coordinate system.

2. 2. The holographic recording medium according to claim 1, wherein the polymer matrix is ​​formed by cross-linking a siloxane-based polymer containing a silane functional group and an acrylic polyol.

3. 3. The holographic recording medium according to claim 2, wherein the siloxane-based polymer comprises a repeating unit represented by the following chemical formula 1 and a terminal group represented by the following chemical formula 2: 【Chemistry 1】 In the above Chemical Formula 1, Multiple R １１ and R １２ are the same or different and each independently represent hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, k is an integer from 1 to 10,000; 【Chemistry 2】 In the above Chemical Formula 2, Multiple R １３ ~R １５ are the same or different and each independently represent hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, At least one repeating unit selected from the repeating units represented by Chemical Formula 1 and any one of the terminal groups selected from the terminal groups represented by Chemical Formula 2, １１ ~R １５ At least one of is hydrogen.

4. 3. The holographic recording medium according to claim 2, wherein the acrylic polyol is a polymer having a structure in which a hydroxy group is bonded to a main chain or a side chain of an acrylate polymer.

5. The photoreactive monomers include benzyl (meth)acrylate, benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, and phenol (ethylene oxide) ２ one or more monofunctional monomers selected from the group consisting of (meth)acrylate, O-phenylphenol(ethylene oxide)(meth)acrylate, phenylthioethyl(meth)acrylate, and biphenylmethyl(meth)acrylate; bisphenol A(ethylene oxide) ２～１０ 2. The holographic recording medium according to claim 1, comprising one or more polyfunctional monomers selected from the group consisting of di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolac epoxy (meth)acrylate; or a mixture of two or more thereof.

6. 2. The holographic recording medium of claim 1, wherein the blue light-sensitive dye comprises a cation-containing compound represented by the following chemical formula 3: 【Transformation 3】 In the above Chemical Formula 3, R １ is an alkylene group having 1 to 6 carbon atoms, and R ２ is an alkyl group having 1 to 6 carbon atoms, n1 is an integer from 1 to 6, R ３ is an alkyl group having 3 to 12 carbon atoms, R ４ is hydrogen or an alkyl group having 1 to 6 carbon atoms, R ５ and R ６ are each independently a halogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, n2 and n3 each independently represent an integer of 0 to 4; Z is oxygen, sulfur or CR ７ R ８ and R ７ and R ８ are each independently an alkyl group having 1 to 6 carbon atoms.

7. The holographic recording medium according to claim 6 , wherein the cation-containing compound represented by Chemical Formula 3 contains tetraarylborate as an anion.

8. 8. The holographic recording medium according to claim 7, wherein the tetraarylborate contains at least one anion selected from the group consisting of tetraphenylborate, tetrakis(fluorophenyl)borate, tetrakis(chlorophenyl)borate, tetrakis(methylphenyl)borate, tetrakis(methoxyphenyl)borate, tetrakis(fluoromethylphenyl)borate, tetrakis(fluoromethoxyphenyl), tetrakis(chloromethylphenyl)borate, and tetrakis(chloromethoxyphenyl)borate.

9. 2. The holographic recording medium of claim 1, wherein the red light-sensitive dye comprises a silicon rhodamine compound represented by the following chemical formula 4: 【Chemistry 4】 In the above Chemical Formula 4, R ２１ ~R ２９ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, d and e each independently represent an integer of 0 to 3; f is an integer from 0 to 5, An － is an anion.

10. 2. The holographic recording medium of claim 1, wherein the green light-sensitive dye comprises one or more compounds selected from the group consisting of a compound represented by the following Chemical Formula 5, a compound represented by the following Chemical Formula 6, a compound represented by thioerythrosine triethylammonium, and a compound represented by erythrosine B: 【Transformation 5】 In the above Chemical Formula 5, Y is O or S; R ６１ ~R ６６ are each independently hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; R ６７ is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, g and h each independently represent an integer of 0 to 3; i is an integer from 0 to 5, Ani － is an anion, 【Transformation 6】 In the above Chemical Formula 6, R ７１ ~R ７７ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, Anii － is an anion.

11. 2. The holographic recording medium according to claim 1, wherein when the photopolymer layer is irradiated with light in the red, green, and blue regions to record a notch filter hologram, the total diffraction efficiency of the red, green, and blue regions is 150% or more.

12. 2. The holographic recording medium according to claim 1, wherein when the photopolymer layer is irradiated with light in the red, green, or blue region to record a notch filter hologram, the diffraction efficiency in the red, green, or blue region is 80% or more.

13. The holographic recording medium according to claim 1, which satisfies the following formula 3: [Formula 3] △T ４００ =T ４００ ａ -T ４００ ｂ ≦10%p In the above formula 3, T ４００ ａ is the initial transmittance measured at 400 nm for the photopolymer layer photobleached with recorded optical information, T ４００ ｂ is the transmittance measured at 400 nm after the photopolymer layer whose initial transmittance has been measured is exposed to 120° C. for 500 hours.

14. 2. The holographic recording medium according to claim 1, wherein the diffraction efficiency maintenance rate calculated by the following formula 4 is 80% or more: [Formula 4] Diffraction efficiency maintenance rate (%) = 100 × DE ｂ / DE ａ In the above formula 4, DE ａ is the diffraction efficiency in the recording wavelength region measured by irradiating the holographic recording medium with light in one or more regions selected from red, green, and blue regions to record a notch filter hologram, or is the sum of these values; DE ｂ is the diffraction efficiency in the recording wavelength region measured after leaving the recorded hologram recording medium at 120° C. for 500 hours, or is the sum of these values.

15. applying a photopolymer composition comprising a polymer matrix or a precursor thereof, a photoreactive monomer, and a photoinitiator system to form a photopolymer layer; the photoinitiator system comprises a photosensitive dye and a coinitiator; The photosensitive dyes include a red-region photosensitive dye, a green-region photosensitive dye, and a blue-region photosensitive dye; The photopolymer layer satisfies the following formulas 1 and 2: [Formula 1] T ａｖｇ ≧90% In the above formula 1, T ａｖｇ is the average transmittance measured in the 400 to 700 nm region for the photopolymer layer that has been photobleached without any optical information recorded thereon; [Equation 2] In the above formula 2, ΔE is the color difference between a sample obtained by photobleaching the photopolymer layer without recording optical information and a white light having the same brightness as the photopolymer layer; L Ｓ ＊ , a Ｓ ＊ and b Ｓ ＊ is the color value in the Lab color coordinate system derived from the transmission spectrum of the photobleached sample in the region of 400 to 700 nm, standard illuminant D65, and a viewing angle of 10°; L Ｒ ＊ , a Ｒ ＊ and b Ｒ ＊ is the color value of the white light in the Lab color coordinate system.

16. 16. The method of claim 15, further comprising irradiating a predetermined region of the photopolymer layer with a coherent laser to selectively polymerize a photoreactive monomer contained in the photopolymer layer, thereby recording optical information.

17. An optical element comprising the holographic recording medium according to claim 1 .

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