Photopolymer composition, hologram recording medium, method of preparing same, and optical element including same

Abstract

The present disclosure relates to a photopolymer composition, a hologram recording medium, a method of preparing the same, and an optical element including the same. The photopolymer composition can provide a hologram recording medium exhibiting not only excellent optical recording characteristics but also excellent reliability and transparency even at high temperatures, and an optical element including the same.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0022505, filed on February 16, 2024, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

[0003] This disclosure relates to photopolymer compositions, holographic recording media, methods for their preparation, and optical elements including the same. Background Technology

[0004] Holographic recording media record information by changing the refractive index of the holographic recording layer in the medium through an exposure process, and then read the changes in the refractive index in the recorded medium to reproduce the information.

[0005] In this regard, photopolymer compositions can be used to prepare holograms. Photopolymers can readily store optical interference patterns as holograms through the photopolymerization of photoreactive monomers. Therefore, photopolymers can be used in various fields, such as smart devices like mobile devices, wearable display components, vehicle products (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflectors, filters, diffusers, diffracting elements, light guides, waveguides, holographic optical elements with projection screen and / or mask functions, media for optical storage systems and light diffusers, optical wavelength multiplexers, reflective color filters, transmissive color filters, etc.

[0006] Specifically, the photopolymer composition used to prepare holograms comprises a polymer matrix, photoreactive monomers, and a photoinitiator system, and the photopolymer layer prepared from such a composition is irradiated with laser interference light to induce localized photopolymerization of monomers.

[0007] This local photopolymerization process generates refractive index modulation, which in turn produces a diffraction grating. The refractive index modulation value (Δn) is affected by the thickness of the photopolymer layer and the diffraction efficiency (DE), and the angular selectivity increases as the thickness decreases.

[0008] Recently, there has been an increasing demand for materials that can maintain stable holograms at high diffraction efficiencies, and various attempts have been made to prepare photopolymer layers with high diffraction efficiencies, high refractive index modulation values, and thin thickness.

[0009] On the other hand, when holographic recording media are used as optical elements in applications such as mobile devices or vehicle components (e.g., head-up displays), they are exposed to high-temperature environments. In such cases, when the diffraction grating deforms, the image becomes distorted and may fail to perform its originally intended function. Therefore, there is a need to develop photopolymer layers and holographic recording media incorporating them that exhibit minimal diffraction grating deformation despite ambient heat and possess excellent reliability. Summary of the Invention

[0010] Technical issues

[0011] According to one embodiment of this disclosure, a photopolymer composition is provided.

[0012] According to another embodiment of this disclosure, a holographic recording medium is provided.

[0013] According to yet another embodiment of this disclosure, a method for preparing the holographic recording medium is provided.

[0014] According to another embodiment of this disclosure, an optical element comprising the holographic recording medium is provided.

[0015] Technical solution

[0016] The following will describe specific embodiments of photopolymer compositions, holographic recording media, methods for their preparation, and optical elements thereof, according to the present disclosure.

[0017] Unless otherwise specified, the term "holographic recording medium" as used herein means a medium on which optical information can be recorded via an exposure process throughout the visible and ultraviolet range (e.g., 300 nm to 1200 nm). Holograms as used herein can include all visual holograms, such as coaxial (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white light transmission holograms ("rainbow holograms"), Denisyuk holograms, off-axis reflection holograms, edge-illumination holograms, or holographic stereographs.

[0018] In this specification, regarding the environmental conditions under which the holographic recording medium or the device comprising it is placed, "high temperature" may mean a temperature of 60°C or higher. For example, high temperature may mean 65°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, 85°C or higher, or 90°C or higher, and there is no particular upper limit, but it may be, for example, 110°C or lower, 105°C or lower, 100°C or lower, 95°C or lower, 90°C or lower, 85°C or lower, or 80°C or lower. When temperature affects the properties of a material, object, or component, unless otherwise specifically mentioned, the temperature conditions for measuring or describing the properties may mean room temperature (e.g., a temperature in the range of about 15°C to 30°C, which is a temperature without heating or cooling).

[0019] In this specification, unless otherwise stated, the measurements should be understood as measurements of the photopolymer layer included in the holographic recording medium.

[0020] According to one embodiment of the present disclosure, a photopolymer composition is provided comprising: a polymer matrix or precursor formed by crosslinking a siloxane-based polymer containing silane functional groups with an acrylic polyol; a fluorinated compound represented by the following chemical formula 1; a photoreactive monomer; and a photoinitiator system.

[0021] [Chemical Formula 1]

[0022]

[0023] In chemical formula 1,

[0024] Z 1 It is -O- or -NH-.

[0025] Z 2 It is a single bond, -O- or -NH-.

[0026] L 1 It is a single bond or a divalent to hexavalent organic group in which the hydroxyl groups have been removed from polyols having 2 to 6 hydroxyl groups.

[0027] n and m are each independent integers from 1 to 5, where the sum of n and m is from 2 to 6.

[0028] R 1 R 2 and R 3 Each is independently either methyl or ethyl.

[0029] R 4The fluorinated substituent is an alkyl group having 1 to 20 carbon atoms that has been substituted with 2 or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms.

[0030] Through experiments, the inventors discovered that when a fluorinated compound with a specific structure is used as a plasticizer in a photopolymer composition, a holographic recording medium with excellent optical recording properties, high reliability under high temperature conditions, and high transparency can be provided, thus completing this invention.

[0031] The following describes an embodiment of a photopolymer composition according to the present disclosure, a holographic recording medium formed from the photopolymer composition, a method for preparing the same, and optical elements including the holographic recording medium.

[0032] According to one embodiment of the present disclosure, a photopolymer composition comprises a polymer matrix or a precursor thereof, which serves as a support for a photopolymer layer formed from the photopolymer composition.

[0033] The polymer matrix is ​​formed by crosslinking a siloxane-based polymer containing silane functional groups (Si-H) with an acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking an acrylic polyol with a siloxane-based polymer containing silane functional groups. More specifically, the hydroxyl groups of the acrylic polyol can be crosslinked with the silane functional groups of the siloxane-based polymer via a hydrosilylation reaction. The hydrosilylation reaction can proceed rapidly even at room temperature (e.g., at temperatures in the range of about 15°C to 30°C, which is a temperature without heating or cooling) under a Pt-based catalyst. Therefore, the photopolymer composition according to one embodiment of this disclosure uses a polymer matrix that can be rapidly crosslinked even at room temperature as a support, thereby improving preparation efficiency and productivity.

[0034] The polymer matrix enhances the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer due to the flexible backbone of the siloxane-based polymer. Furthermore, the excellent heat and humidity resistance of the siloxane bonds helps ensure the reliability of the photopolymer layer in which optical information is recorded, as well as the holographic recording medium comprising it.

[0035] The polymer matrix can have a relatively low refractive index, which can be used to enhance the refractive index modulation of layers formed from photopolymer compositions. For example, the upper limit of the refractive index of the polymer matrix can be 1.53 or less, 1.52 or less, 1.51 or less, 1.50 or less, or 1.49 or less. Furthermore, the lower limit of the refractive index of the polymer matrix can be, for example, 1.40 or greater, 1.41 or greater, 1.42 or greater, 1.43 or greater, 1.44 or greater, 1.45 or greater, or 1.46 or greater. As used herein, "refractive index" can be a value measured using an Abbe refractometer at 25°C.

[0036] A photopolymer composition according to one embodiment of this disclosure may comprise a cross-linked polymer matrix as described above, or may comprise a precursor thereof. When the photopolymer composition comprises a precursor to the polymer matrix, it may comprise a siloxane-based polymer, an acrylic polyol, and a Pt-based catalyst.

[0037] Siloxane-based polymers may contain, for example, repeating units represented by the following chemical formula 2 and terminal groups represented by the following chemical formula 3.

[0038] [Chemical Formula 2]

[0039]

[0040] In chemical formula 2,

[0041] Complex R 11 and R 12 They may be the same as or different from each other, and each is independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and

[0042] k is an integer from 1 to 10,000.

[0043] [Chemical Formula 3]

[0044]

[0045] In chemical formula 3,

[0046] Complex R 13 To R 15 They may be the same as or different from each other, and each is independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and

[0047] R is selected from at least one repeating unit from the repeating units represented by chemical formula 2 and any one of the terminal groups from the terminal groups represented by chemical formula 3. 11 To R 15 At least one of them is hydrogen.

[0048] In Formula 3, -(O)- means that when the Si of the terminal group represented by Formula 3 is bonded to the repeating unit represented by Formula 2, it is bonded by oxygen (O) or directly in the absence of oxygen (O).

[0049] As used herein, "alkyl" can be a straight-chain alkyl, branched alkyl, or cyclic alkyl. As a non-limiting example, "alkyl" as used herein can be 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-dimethyl-propyl, 1-ethyl-propyl, 1-methyl-butyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methyl-ethyl-propyl, 1-methyl-ethyl-propyl, 1-methyl-ethyl-propyl, 1-methyl-ethyl-propyl, cyclopentyl, etc.). Examples of compounds include methylpentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethyl-butyl, 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.), and nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.).

[0050] In one example, R in chemical formula 2 and chemical formula 3 11 To R 15 It is either methyl or hydrogen, and R 11 To R 15 At least two of them can be hydrogen. More specifically, the siloxane-based polymer can be R of chemical formula 2 in which 11 and R 12 Each is independently methyl and hydrogen, and R in chemical formula 3. 13 To R 15 Compounds that are each independently methyl or hydrogen (e.g., polymethylhydrosiloxanes with terminal groups of trimethylsilyl or dimethylhydrosilyl); wherein some R of formula 2 11 and R 12 They are methyl and hydrogen, respectively, and the remaining R... 11 and R 12 All are methyl groups, and R in chemical formula 3. 13 To R 15 Compounds in which each is independently methyl or hydrogen (e.g., poly(dimethylsiloxane-copoly-methylhydrosiloxane) with a terminal group of trimethylsilyl or dimethylhydrosilyl); or wherein R of formula 2 11 and R 12 Both are methyl groups, and the R in chemical formula 3 is... 13 To R 15The compound in which at least one of the components is hydrogen, and the remainder is methyl or hydrogen (e.g., polydimethylsiloxane in which either or both of the terminal groups are dimethylhydrosilyl).

[0051] As an example, the number-average molecular weight (Mn) of siloxane-based compounds can range from 200 to 4,000. Specifically, the lower limit of the number-average molecular weight of siloxane-based polymers can be, for example, 200 or greater, 250 or greater, 300 or greater, or 350 or greater, and the upper limit can 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 meets the above range, the following problems can be prevented, thereby enabling the holographic recording medium formed from the photopolymer composition to exhibit excellent optical recording properties and durability at high temperatures: the siloxane-based polymer volatilizes and the matrix crosslinking degree decreases during the crosslinking process with acrylic polyols at room temperature or higher, or the siloxane-based polymer has poor compatibility with other components of the photopolymer composition, and therefore phase separation occurs between the components.

[0052] Number-average molecular weight (NMR) refers to the number-average molecular weight (in g / mol) of polystyrene as determined by GPC. In determining the NMR of polystyrene as measured by GPC, known analytical apparatus, detectors such as refractive index detectors, and analytical columns can be used, along with commonly applied temperature, solvent, and flow rate conditions. Specific examples of measurement conditions may include a temperature of 25°C, tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0053] Acrylic polyols can refer to polymers in which one or more, specifically two or more, hydroxyl groups are bonded to the main chain or side chain of an acrylate-based polymer. Unless otherwise specified, "acrylic" as used herein means one or more selected from acryloyl, methacryl, and their derivatives, or repeating units formed by the polymerization of these. Unless otherwise specified, "acrylate-based" as used herein means one or more selected from acrylates and methacrylates, or repeating units formed by the polymerization of these.

[0054] Acrylic polyols are homopolymers of hydroxyl-based acrylate monomers, copolymers of two or more types of hydroxyl-based acrylate monomers, or copolymers of hydroxyl-based acrylate monomers and non-hydroxyl-based acrylate monomers. Unless otherwise stated, the term "copolymer" as used herein is a term encompassing all random copolymers, block copolymers, and graft copolymers.

[0055] acrylate-based monomers having hydroxyl groups may include, for example, hydroxyalkyl (meth)acrylate, hydroxyaryl (meth)acrylate, etc., where the alkyl group is an alkyl group having 1 to 30 carbon atoms, and the aryl group is an aryl group having 6 to 30 carbon atoms. Furthermore, acrylate-based monomers without hydroxyl groups may include, for example, alkyl (meth)acrylate, aryl (meth)acrylate, etc., where the alkyl group is an alkyl group having 1 to 30 carbon atoms, and the aryl group is an aryl group having 6 to 30 carbon atoms. Unless otherwise specified, "(meth)acrylate" as used herein refers to acrylates and / or methacrylates.

[0056] As an example, the weight-average molecular weight (Mw) of acrylic polyols can range from 150,000 to 1,000,000. Weight-average molecular weight refers to the weight-average molecular weight of polystyrene as measured by the GPC method as described above. For example, the lower limit of the weight-average molecular weight can be 150,000 or greater, 200,000 or greater, or 250,000 or greater, and its upper limit can be, for example, 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 acrylic polyols meets the above range, the polymer matrix fully performs its function as a support, and therefore the recording properties of optical information are reduced less even after the use time has passed. It also gives the polymer matrix sufficient flexibility to improve the mobility of components contained in the photopolymer composition (e.g., photoreactive monomers or plasticizers) and minimize the reduction in the recording properties of optical information.

[0057] In order to adjust the crosslinking density of acrylic polyols to a level that is conducive to ensuring the function of holographic recording media through siloxane-based polymers, the hydroxyl equivalent of acrylic polyols can be adjusted to an appropriate level.

[0058] Specifically, the hydroxyl (-OH) equivalent of acrylic polyols can be, for example, in the range of 500 g / equivalent to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl (-OH) equivalent of acrylic polyols can be 600 g / equivalent or greater, 700 g / equivalent or greater, 800 g / equivalent or greater, 900 g / equivalent or greater, 1000 g / equivalent or greater, 1100 g / equivalent or greater, 1200 g / equivalent or greater, 1300 g / equivalent or greater, 1400 g / equivalent or greater, 1500 g / equivalent or greater, 1600 g / equivalent or greater, 1700 g / equivalent or greater, or 1750 g / equivalent or greater. Furthermore, the upper limit for the hydroxyl (-OH) equivalent of acrylic polyols can 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 of acrylic polyols refers to the equivalent weight (g / equivalent) of each individual hydroxyl group, and is obtained by dividing the weight-average molecular weight of the acrylic polyol by the number of hydroxyl groups per molecule. Therefore, the smaller the equivalent value, the higher the density of the functional group, and vice versa. When the hydroxyl (-OH) equivalent of the acrylic polyol meets the above range, the polymer matrix has an appropriate crosslinking density and thus fully functions as a support. Furthermore, the mobility of the components contained in the layer formed by the photopolymer composition is improved, which allows the initial refractive index modulation value to remain at an excellent level even over time, without the problem of boundary collapse of the diffraction grating after recording, thereby minimizing the reduction in the recording characteristics of optical information.

[0059] For example, the glass transition temperature (Tg) of acrylic polyols can be in the range of -60°C to -10°C. Specifically, the lower limit of the glass transition temperature can 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 its upper limit can be, for example, -15°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, or -35°C or lower. If the above glass transition temperature range is met, the glass transition temperature can be reduced without significantly reducing the modulus of the polymer matrix, thereby improving the mobility (flowability) of other components in the photopolymer composition and also 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).

[0060] The refractive index of acrylic polyols can be, for example, 1.40 or greater and less than 1.50. Specifically, the lower limit of the refractive index of acrylic polyols can be, for example, 1.41 or greater, 1.42 or greater, 1.43 or greater, 1.44 or greater, 1.45 or greater, or 1.46 or greater, and the upper limit can 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 acrylic polyols have a refractive index within the above range, it can help to improve refractive index modulation. The refractive index of acrylic polyols is a theoretical refractive index and can be calculated using the refractive index of the monomers used to prepare the acrylic polyols (values ​​measured using an Abbe refractometer at 25°C) and the fraction (molar ratio) of each monomer.

[0061] The polymer may contain acrylic polyols and siloxane-based polymers such that the molar ratio (SiH / OH) of the silane functional groups (Si-H) of the siloxane-based polymer to the hydroxyl groups (-OH) of the acrylic polyol is from 0.80 to 3.5. That is, the type and content of the siloxane-based polymer and the acrylic polyol can be selected to satisfy the molar ratio when forming the polymer matrix. The lower limit of the molar ratio (SiH / OH) can be, for example, 0.81 or greater, 0.85 or greater, 0.90 or greater, or 0.95 or greater, and its upper limit can 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 above molar ratio (SiH / OH) range is met, the polymer matrix crosslinks to an appropriate crosslinking density, thereby improving reliability under high-temperature conditions and achieving sufficient refractive index modulation values.

[0062] Pt-based catalysts can be, for example, Karstedt catalysts. In addition to Pt-based catalysts, the polymer matrix precursor may optionally include rhodium-based catalysts, iridium-based catalysts, rhenium-based catalysts, molybdenum-based catalysts, iron-based catalysts, nickel-based catalysts, alkali metal or alkaline earth metal-based catalysts, Lewis acid-based catalysts, or carbene-based nonmetallic catalysts.

[0063] On the other hand, a holographic recording medium can be prepared by irradiating an object beam and a reference beam onto a photopolymer layer formed from a photopolymer composition according to one embodiment of the present disclosure. Due to the interference field between the object beam and the reference beam, photopolymerization of photoreactive monomers does not occur in the destructive interference region, but it does occur in the constructive interference region. As the photoreactive monomers are continuously consumed in the constructive interference region, a concentration difference appears between the photoreactive monomers in the destructive and constructive interference regions, thus causing the photoreactive monomers in the destructive interference region to diffuse into the constructive interference region. A diffraction grating is generated by the resulting refractive index modulation.

[0064] Therefore, the photoreactive monomer can contain compounds with a refractive index higher than that of the polymer matrix to achieve the aforementioned refractive index modulation. However, all photoreactive monomers contained in the photopolymer composition according to one embodiment of this disclosure are not limited to those with a refractive index higher than that of the polymer matrix, and at least a portion of the photoreactive monomers can have a higher refractive index than that of the polymer matrix to achieve a high refractive index modulation value. In one example, the photoreactive monomer can contain monomers with refractive indices of 1.50 or greater, 1.51 or greater, 1.52 or greater, 1.53 or greater, 1.54 or greater, 1.55 or greater, 1.56 or greater, 1.57 or greater, 1.58 or greater, 1.59 or greater, or 1.60 or greater and 1.70 or less.

[0065] The photoreactive monomer may comprise at least one monomer selected from monofunctional monomers having one photoreactive functional group and polyfunctional monomers having two or more photoreactive functional groups. The photoreactive functional group may be, for example, (meth)acryloyl, vinyl, thiol, etc. More specifically, the photoreactive functional group may be (meth)acryloyl.

[0066] Monofunctional monomers may include, for example, at least one selected from the following: benzyl (meth)acrylate (M1182 with a refractive index of 1.5140, Miwon Specialty Chemical), 2-phenylbenzyl acrylate, phenoxybenzyl (meth)acrylate (M1122 with a refractive index of 1.565, Miwon Specialty Chemical), phenol(ethylene oxide)(meth)acrylate (phenol(EO)(meth)acrylate; M140 with a refractive index of 1.516, Miwon Specialty Chemical), phenol(ethylene oxide)2(meth)acrylate (phenol(EO)2(meth)acrylate; M142 with a refractive index of 1.510, Miwon Specialty Chemical), o-phenylphenol(ethylene oxide)(meth)acrylate (o-phenylphenol(EO)(meth)acrylate; M1142 with a refractive index of 1.577, Miwon Specialty Chemical), and phenylthioethyl (meth)acrylate (M1162 with a refractive index of 1.560, Miwon Specialty Chemical). Specialty Chemical), and (meth)acrylate biphenyl methyl ester.

[0067] Multifunctional monomers may include, for example, at least one selected from the following: bisphenol A (ethylene oxide). 2～10 Di(meth)acrylate (bisphenol A(EO)) 2～10(Meth)acrylates; M240 with refractive index 1.537, M241 with refractive index 1.529, M244 with refractive index 1.545, M245 with refractive index 1.537, M249 with refractive index 1.542, M2100 with refractive index 1.516, M2101 with refractive index 1.512, Miwon Specialty Chemical), bisphenol A epoxy di(meth)acrylates (PE210 with refractive index 1.557, PE2120A with refractive index 1.533, PE2120B with refractive index 1.534, PE2020C with refractive index 1.539, PE2120S with refractive index 1.556, Miwon Specialty Chemical), bisfluorene di(meth)acrylate (HR6022, HR6040, and HR6042 with refractive index 1.600, Miwon Specialty Chemical), modified bisphenol fluorene di(meth)acrylate (HR6060, HR6100, and HR6200 with refractive index 1.584, Miwon Specialty Chemical), tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate (M370 with refractive index 1.508, Miwon Specialty Chemical), phenolic epoxy (meth)acrylate (SC6300 with refractive index 1.525, Miwon Specialty Chemical), and cresolic epoxy (meth)acrylate (SC6400 and SC6400C with refractive index 1.522, Miwon Specialty Chemical). Specialty Chemical).

[0068] Based on 100 parts by weight of a polymer matrix, the photopolymer composition according to one embodiment of this disclosure may contain photoreactive monomers in an amount from 50 parts by weight to 300 parts by weight. For example, the lower limit of the photoreactive monomer content 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. Here, "polymer matrix content" refers to the total content (by weight) of acrylic polyols and siloxane-based polymers forming the matrix. Meeting these ranges is beneficial for ensuring excellent optical recording properties and durability under high-temperature conditions.

[0069] In this specification, the content of polymer matrix means the total content (by weight) of the acrylic polyols and siloxane-based polymers that form the matrix. In other words, the content of polymer matrix means both the content of the polymer matrix formed by crosslinking the acrylic polyols and siloxane-based polymers and the content of the partially uncrosslinked polymer matrix precursors.

[0070] One embodiment of the photopolymer composition according to this disclosure includes a photoinitiator system. The photoinitiator system may refer to a photoinitiator that enables polymerization by photoinitiation, or a combination of a photosensitizer and a co-initiator.

[0071] One embodiment of the photopolymer composition may include a photosensitizer and a co-initiator as a photoinitiator system.

[0072] As photosensitizers, photosensitive dyes can be used. Specifically, photosensitive dyes may include, for example, at least one selected from the following: silirodamine compounds, sulfonium derivatives of anthraquinone (9,1-bc)naphthoquinone (3,2,1-kl)acridine, neomethylene blue, triethylammonium thioerythrine, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose red, thionine, basic yellow, pinacyanine chloride, rhodamine 6G, benzoin, ethyl violet, Victoria blue R, azurite blue, quinazon red, crystal violet, brilliant green, basic orange G, darrow red, pyronin Y, basic red 29, pyran. I (pyran) Iodides), Safranin O, Anthocyanin, Methylene Blue, Azurite A, and BODIPY.

[0073] In one instance, as a photosensitive dye, cyanine dyes Cy3 and Cy5 (H-Nu640, Spectra Group Limited) or safranin O can be used.

[0074] Based on 100 parts by weight of a polymer matrix, one embodiment of the photopolymer composition may contain a photosensitive dye in an amount from 0.01 parts by weight to 10 parts by weight. Specifically, the lower limit of the photosensitive dye content may be, for example, 0.05 parts by weight or more, 0.07 parts by weight or more, or 0.10 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above ranges are met, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording properties.

[0075] Co-initiators may include electron donors, electron acceptors, or mixtures thereof.

[0076] In one example, a photopolymer composition of one embodiment may include an electron donor as a co-initiator. The electron donor may include, for example, a borate anion represented by the following chemical formula 4.

[0077] [Chemical Formula 4]

[0078] BX 1 X 2 X 3 X 4

[0079] In chemical formula 4, X 1 To X 4 Each is independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, provided that X 1 To X 4 At least one of them is not an aryl.

[0080] When an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group is substituted, it may be substituted with at least one selected from halogens and alkoxy groups having 1 to 5 carbon atoms.

[0081] Specifically, X 1 To X 3 Each of these can be independently halogenated or unsubstituted methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, cyclobutyl, cyclopentyl, cyclohexyl, vinyl, propenyl, phenyl, methylphenyl, methoxyphenyl, naphthyl, methylnaphthyl, or methoxynaphthyl, and X. 4 It can be n-butyl, n-pentyl, or n-hexyl. More specifically, the borate anion represented by chemical formula 4 can be, for example, triphenylbutylborate anion.

[0082] The cation bonded to the borate anion does not absorb light and can be an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation can be an ammonium cation in which nitrogen (N) is substituted with four substituents, and each of the four substituents is independently 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 by an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3, etc.).

[0083] As an electron donor, commercially available butyrylcholine triphenylbutylborate (Borate V, manufactured by Spectra Group) can be used, for example.

[0084] In one example, the photopolymer composition may include an electron acceptor as a co-initiator. The electron acceptor may include, for example... Salt, such as matte salt and iodine salt Salt, or a mixture thereof.

[0085] In one instance, the electron acceptor may include iodine. Salt. As an electron acceptor, commercially available H-Nu 254 (Spectra Group) can be used, for example.

[0086] Based on 100 parts by weight of the polymer matrix, the photopolymer composition may contain a co-initiator ranging from 0.05 parts by weight to 10 parts by weight. Specifically, the lower limit of the co-initiator content may be, for example, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, or 0.5 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above ranges are met, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording properties.

[0087] The photoinitiator system may include additional photoinitiators to remove the color of the photosensitive dye and react all unreacted photoreactive monomers after light irradiation for recording. Photoinitiators may include, for example, acetophenone-based compounds, oxime-based compounds, phosphine oxide-based compounds, thioxanthone-based compounds, benzoate-based compounds, imidazole-based compounds, N-arylglycine derivatives, organoazides, titanocerocene, aluminate complexes, organic peroxides, and N-alkoxypyridine. Salts, amine derivatives, diazonium salts, sulfonium salts, iodine Salts, sulfonates / esters, imide sulfonates / esters, dialkyl-4-hydroxysulfonate, arylsulfonic acid-p-nitrobenzyl ester, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl)iron(II), benzoin toluenesulfonate / ester, 2,5-dinitrobenzyl toluenesulfonate / ester, N-toluenesulfonyl phthalimide, or mixtures thereof.

[0088] More specifically, photoinitiators may include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinoprop-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-but-1-one (Irgacure 369), 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl] ethyl ketone-1-(O-acetyl oxime) (Irgacure OXE02, BASF), [(Z)-(1-oxo-1-phenylpropane-2-yl)amino]benzoate (e.g., TPI-057 or TPI-059, manufactured by TREEEL), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure TPO), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (Irgacure 1700), phenyl bis(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(tert-butyldioxycarbonyl)benzophenone, 3,3′,4,4″-tetra(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5-iso Azoline, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethyl-1-one (Irgacure 651), 1-hydroxycyclohexylphenyl ketone (Irgacure 184), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrolo-1-yl)phenyl)titanium (Irgacure 784), EbecrylP-115 (SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (Dow Chemical Co., USA), Irgacure 264, Irgacure 250 (BASF), CIT-1682 (Nippon Soda), or mixtures thereof, but not limited thereto.

[0089] One embodiment of the photopolymer composition according to this disclosure contains a fluorinated compound as a plasticizer.

[0090] Plasticizers facilitate refractive index modulation when recording holographic media. More specifically, plasticizers lower the glass transition temperature of the polymer matrix, improve the mobility of photoreactive monomers, and possess low refractive index and non-reactive properties. Therefore, when photoreactive monomers uniformly distributed within the polymer matrix but not photopolymerized move, they can move in the opposite direction, contributing to refractive index modulation. Furthermore, plasticizers can also help improve the formability of photopolymer compositions.

[0091] Fluorinated compounds can have a low refractive index of 1.45 or less to perform the aforementioned plasticizer function. Specifically, the upper limit of the refractive index can be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less. The lower limit of the refractive index can be, for example, 1.30 or greater, 1.31 or greater, 1.32 or greater, 1.33 or greater, 1.34 or greater, or 1.35 or greater. By using fluorinated compounds with a refractive index lower than that of the aforementioned photoreactive monomers, the refractive index of the polymer matrix can be further reduced, and the refractive index modulation of the photoreactive monomers can be further enhanced.

[0092] Non-reactive plasticizers are dispersed within the polymer matrix that supports the photopolymer layer, without being chemically bonded to it. Therefore, depending on the environment in which the holographic recording medium is used, the non-reactive plasticizers may migrate to the surface of the photopolymer layer, especially at high temperatures, where they may readily migrate to the surface. The plasticizers that migrate to the surface form anisorefractive layers (or layers with different refractive indices) in the surface regions of the photopolymer layer, and such layers are a major cause of reduced reliability in holographic recording media.

[0093] One embodiment of the photopolymer composition may contain a fluorinated compound that hardly migrates to the surface of the photopolymer layer or migrates to a negligible degree, such that an anisorefringent layer does not form or forms to a very small degree even at high temperatures. Therefore, a holographic recording medium that can clearly reproduce the original intended image and maintain high transparency even at high temperatures can be provided.

[0094] One embodiment of the photopolymer composition comprises a fluorinated compound represented by the following chemical formula 1.

[0095] [Chemical Formula 1]

[0096]

[0097] In chemical formula 1,

[0098] Z 1 It is -O- or -NH-.

[0099] Z 2 It is a single bond, -O- or -NH-.

[0100] L 1 It is a single bond or a divalent to hexavalent organic group in which the hydroxyl groups have been removed from polyols having 2 to 6 hydroxyl groups.

[0101] n and m are each independent integers from 1 to 5, where the sum of n and m is from 2 to 6.

[0102] R 1 R 2 and R 3 Each is independently either methyl or ethyl.

[0103] R 4 The fluorinated substituent is an alkyl group having 1 to 20 carbon atoms that has been substituted with 2 or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms.

[0104] In chemical formula 1, L 1 The carbonyl-containing portion and the R-containing portion 4 The partial connection. Therefore, the sum of n and m is 2 to 6, which equals L. 1 The number of keys in the code.

[0105] In one example, in chemical formula 1, L 1 It can be a single bond. In chemical formula 1, when L... 1 When it is a single bond, n and m are both 1, and Z is 1. 2 It can also be a single bond. In such cases, the fluorinated compound represented by chemical formula 1 can be represented by the following chemical formula 1-1.

[0106] [Chemical Formula 1-1]

[0107]

[0108] In chemical formula 1-1,

[0109] Z 1' R 1' R 2' R 3' and R 4' Respectively with Z in chemical formula 1 1 R 1 R 2 R 3 and R 4 Same. Z 1' R 1' R 2' R3' and R 4' Z can be used as chemical formula 1 in this article. 1 R 1 R 2 R 3 and R 4 The specific examples of substituents are described.

[0110] In another example, in formula 1, when the hydroxyl groups of a polyol having 2 to 6 hydroxyl groups are Z 1 and Z 2 When replacing, L 1 This can be divalent to hexavalent organic groups in which hydroxyl groups have been removed from the polyol. In one example, glycerol having three hydroxyl groups has been removed from the polyol. The trivalent organic group with the hydroxyl group removed is represented as:

[0111] In chemical formula 1, L 1 It can be, for example: a divalent organic group in which the hydroxyl group has been removed from a diol such as ethylene glycol, propylene glycol or butanediol; a trivalent organic group in which the hydroxyl group has been removed from a triol such as glycerol or trimethylolpropane; a tetravalent organic group in which the hydroxyl group has been removed from a tetraol such as pentaerythritol or bis(trimethylolpropane); a pentavalent organic group in which the hydroxyl group has been removed from a pentaol such as 6-methylheptanepentol; or a hexavalent organic group in which the hydroxyl group has been removed from a hexaol such as dipentaerythritol.

[0112] In chemical formula 1, when L 1 When the organic group is a single bond or a divalent organic group, n and m are both 1. If L 1 If the organic group is trivalent to hexavalent, then n can be greater than m. In one instance, n can be an integer from 1 to 3, and m can be an integer of 1.

[0113] In one instance, L 1 It can be a trivalent organic group in which the hydroxyl group has been removed from glycerol, which is a triol. Furthermore, n can be 2, and m can be 1. In such a case, the fluorinated compound represented by formula 1 can be represented by the following formulas 1-2.

[0114] [Chemical Formula 1-2]

[0115]

[0116] In chemical formulas 1-2,

[0117] Z 1” Z 2” R 1” R 2” R 3” and R 4”Z, respectively with chemical formula 1 1 Z 2 R 1 R 2 R 3 and R 4 Same. Z 1” Z 2” R 1” R 2” R 3” and R 4” Z can be used as chemical formula 1 in this article. 1 Z 2 R 1 R 2 R 3 and R 4 The specific examples of substituents are described.

[0118] In Formula 1, the fluorinated substituent can be an alkyl group having 1 to 20 carbon atoms substituted with 2 or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms substituted with 2 or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms substituted with 2 or more fluorine atoms. Specifically, the fluorinated substituent can be a straight-chain alkyl group having 1 to 20 carbon atoms substituted with 2 or more fluorine atoms. More specifically, the fluorinated substituent can be -(CH2). a (CF2) b CHF2 or -(CH2) a (CF2) b CF3. Where a is an integer from 0 to 3, an integer from 0 to 2, or an integer from 1, and b can be an integer from 0 to 19, an integer from 0 to 15, an integer from 0 to 12, an integer from 0 to 11, an integer from 0 to 10, or an integer from 0 to 9.

[0119] Based on 100 parts by weight of a polymer matrix, the photopolymer composition according to one embodiment of this disclosure may contain a fluorinated compound in an amount of 20 to 200 parts by weight. Specifically, the lower limit of the fluorinated compound content may be, for example, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, 50 parts by weight or more, or 55 parts by weight or more, and its upper limit may be, for example, 200 parts by weight or less, 180 parts by weight or less, 150 parts by weight or less, 120 parts by weight or less, or 100 parts by weight or less. When the above ranges are met, it can exhibit a large refractive index modulation value after recording because the fluorinated compound has a sufficiently low refractive index, without causing compatibility degradation with the components contained in the photopolymer composition, some fluorinated compound flowing to the surface of the photopolymer layer, or haze degradation, which is beneficial to ensuring excellent optical recording characteristics.

[0120] One embodiment of the photopolymer composition may contain a polymer matrix, a photoreactive monomer, and a fluorinated compound in predetermined amounts, thereby ensuring high reliability at high temperatures.

[0121] In one example, based on the total weight of the polymer matrix, photoreactive monomer, and fluorinated compound, the photopolymer composition may comprise 25% to 40% by weight of the polymer matrix, 25% to 45% by weight of the photoreactive monomer, and 25% to 50% by weight of the fluorinated compound.

[0122] More specifically, the polymer matrix may be included, for example, in amounts of 25% or more and 40% or less, 35% or less, or 33% or less. The photoreactive monomer may be included, for example, in amounts of 25% or more, 30% or more, or 33% or more and 45% or less, 43% or less, or 41% or less. The fluorinated compound may be included, for example, in amounts of 25% or more, 30% or more, or 33% or more and 50% or less, 45% or less, 40% or less, or 38% or less. Within this range, the migration of fluorinated compounds to the surface at high temperatures can be effectively suppressed, thereby contributing to high reliability and high transparency at high temperatures.

[0123] The photopolymer composition of one embodiment may also contain additives, such as defoamers.

[0124] One embodiment of the photopolymer composition may include a silicone-based reactive additive as an antifoaming agent. As a silicone-based reactive additive, for example, a commercially available product such as Tego Rad 2500 can be used.

[0125] The content of defoamer can be appropriately adjusted to a level that does not impede the function of the holographic recording medium.

[0126] The photopolymer composition of one embodiment may also contain a solvent.

[0127] The solvent may be an organic solvent, and examples of such solvents may be at least one organic solvent selected from ketones, alcohols, acetates, and ethers, but are not limited thereto. Specific examples of such organic solvents include at least one selected from: ketones, such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, or tert-butanol; acetates, such as ethyl acetate, isopropyl acetate, or polyethylene glycol monomethyl ether acetate; and ethers, such as tetrahydrofuran or propylene glycol monomethyl ether.

[0128] The organic solvent can be added at the time point when the components in the photopolymer composition are mixed, or it can be included in the photopolymer composition when the components are added in a dispersed or mixed state in the organic solvent.

[0129] One embodiment of the photopolymer composition may contain a solvent with a solids content concentration of 1% to 90% by weight. Specifically, the photopolymer composition may contain a solvent with a solids concentration of 20% or more, 30% or more, 50% or more, or 60% or more, and 85% or less, 80% or less, 75% or less, or 70% or less. Within this range, the photopolymer composition exhibits suitable fluidity and can form a coating without defects such as streaks. No defects occur during the drying and curing processes, and thus a photopolymer layer exhibiting the desired physical and surface properties can be formed.

[0130] On the other hand, according to another embodiment of this disclosure, a holographic recording medium is provided, which includes a photopolymer layer formed from the photopolymer composition.

[0131] Because the holographic recording medium in another embodiment contains a fluorinated compound represented by Formula 1, an anisotropic layer, formed by the migration of plasticizers from the photopolymer layer to the surface, is not formed, or is formed to a very small extent, even at high temperatures. Therefore, the holographic recording medium can clearly reproduce the original intended image and maintain high transparency even at high temperatures.

[0132] Another embodiment of the holographic recording medium may have a sufficiently low Pn value calculated by Equation 1 below. In one example, the P80 (the thickness ratio of the anisotropic layer formed at 80°C) of the holographic recording medium of another embodiment, calculated by Equation 1 below, may be 0.10% or less.

[0133] [Equation 1]

[0134] Pn(%)={A1 / (A1+A2)}×100

[0135] In Equation 1, Pn represents the thickness ratio of the anisorefringent layer formed at n℃.

[0136] A1 represents the thickness of the anisorefringent layer formed at n °C, where the anisorefringent layer refers to the portion of the surface of the photopolymer layer exhibiting a refractive index difference of at least 0.0010% with respect to the central refractive index measured at an incident angle of 70° in the wavelength range of 320 nm to 1680 nm.

[0137] A2 is the thickness of the remaining portion of the photopolymer layer excluding the anisorefractive layer.

[0138] An anisotropic layer refers to a portion of the surface of the photopolymer layer that exhibits a refractive index different from that of the center of the photopolymer layer. Specifically, the refractive index difference from the center refractive index is at least 0.0010%. In one example, if the center refractive index of the photopolymer layer is 1.5, the anisotropic layer can be defined based on a boundary where the refractive index is 0.000015 (=1.5 × 0.00001) higher or lower than 1.5.

[0139] The thickness (A1) of the anisotropic layer can be determined by measuring the refractive index from the surface to the center of the photopolymer layer in the wavelength range of 320 nm to 1680 nm and applying Equation 1. The thickness (A1) can be defined as the thickness observed at the wavelength where the anisotropic layer is thickest in this range.

[0140] A P80 of 0.10% or less means that even when the holographic recording medium is exposed to a high temperature of 80°C, the migration of fluorinated compounds to the surface can be suppressed, resulting in a very small degree of anisotropic layer formation. Therefore, if the Pn calculated by Equation 1 is low enough, the holographic recording medium can clearly reproduce the original intended image at high temperatures without reducing its image reproduction capability.

[0141] The upper limit of P80 can be, for example, 0.10% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, or 0.05% or less, and its lower limit can be, for example, 0% or more.

[0142] Details regarding the method and specific conditions for measuring the refractive index to calculate Pn using Equation 1 can be found in Test Example 1 described below. In Equation 1, Pn can refer to the thickness ratio of the anisorefringent layer formed at n °C in the holographic recording medium prior to recording.

[0143] In another embodiment, the difference between the refractive index at the center and the refractive index at the surface of the holographic recording medium can be small. In one example, at 80°C, the refractive index difference between the center of the photopolymer layer and the surface within 0.05% of the thickness can be 0.080 or less.

[0144] At 80°C, the refractive index difference between the center and a surface within 0.05% of the thickness can be, for example, 0.080 or less, 0.070 or less, 0.060 or less, 0.050 or less, 0.040 or less, 0.030 or less, 0.028 or less, or 0.026 or less. There is no particular limitation on the lower limit of this refractive index difference, but it can be, for example, 0 or greater, or 0.001 or greater. The method and conditions for measuring the refractive index are provided in Test Example 1 described below.

[0145] Because holographic recording media use a mixture of components with low and high refractive indices to record optical properties, they tend to be opaque due to their compatibility. Furthermore, the decomposition or migration of components with low refractive indices (such as plasticizers) can make holographic recording media even more opaque at high temperatures.

[0146] However, since the holographic recording medium of another embodiment contains a fluorinated compound represented by chemical formula 1 as a plasticizer (which exhibits very little decomposition and migration even at high temperatures and shows excellent compatibility with components having high refractive indices), it maintains excellent transparency even when exposed to high temperatures.

[0147] Specifically, the holographic recording medium of another embodiment may have a sufficiently low ΔHn value calculated by Equation 2 below. In one example, the ΔH80 (haze increase at 80°C) of the holographic recording medium of another embodiment, calculated by Equation 2 below, may be 10%p or less.

[0148] [Equation 2]

[0149] ΔHn(%p)=B2-B1

[0150] In Equation 2, ΔHn represents the increase in haze of the holographic recording medium at n℃.

[0151] B1 represents the initial haze of the holographic recording medium before storage at n℃, and

[0152] B2 represents the haze of the holographic recording medium after 100 hours of storage at n℃.

[0153] A ΔH80 of 10%p or less means that even when the holographic recording medium is exposed to a high temperature of 80°C, the migration of fluorinated compounds to the surface can be suppressed, resulting in minimal increase in haze. Therefore, if the ΔHn calculated by Equation 2 is low enough, the holographic recording medium can exhibit transparent optical properties even at high temperatures.

[0154] The upper limit of ΔH80 can be, for example, 9%p or less, 8%p or less, 7%p or less, 6%p or less, 5%p or less, 4%p or less, 3%p or less, 2.5%p or less, 2%p or less, 1.5%p or less, or 1.0%p or less. There is no particular limitation on the lower limit of haze increase, but it can be, for example, 0%p or greater. The haze increase can be measured by the method described in Test Example 2 below. In Equation 2, ΔHn can refer to the haze increase of the holographic recording medium after recording, measured at n °C.

[0155] Another embodiment of the holographic recording medium may further include a substrate on at least one surface of the photopolymer layer. There are no particular limitations on the type of substrate, and those known in the relevant art can be used. For example, substrates such as glass, PET (polyethylene terephthalate), TAC (triacetyl cellulose), PC (polycarbonate), or COP (cyclic olefin polymer) can be used.

[0156] Since the photopolymer layer is formed from the photopolymer composition, it can achieve excellent refractive index modulation and high diffraction efficiency even with a thin thickness, thereby providing excellent optical recording characteristics and exhibiting excellent reliability even under high temperature conditions.

[0157] The thickness of the photopolymer layer can be, for example, in the range of 5.0 μm to 40.0 μm. Specifically, the lower limit of the thickness of the photopolymer layer can be, for example, 6 μm or greater, 7 μm or greater, 8 μm or greater, or 9 μm or greater. Furthermore, the upper limit of the thickness can 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.

[0158] Another embodiment of the hologram recording medium is not limited to this, but may be a medium on which a reflection hologram or a transmission hologram is recorded.

[0159] Regarding the diffraction grating structure, the holographic recording medium can have a notch filter structure. Another embodiment of the holographic recording medium with a notch filter structure can mean that the diffraction grating is not tilted relative to the substrate surface (essentially 0°), for example, as if the diffraction grating were parallel to the substrate surface. Such a holographic recording medium can 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. Furthermore, the two repeating layers can each have a predetermined thickness that is the same as or different from each other. Such a non-tilted diffraction grating record can be prepared such that the incident angle of the object light and the incident angle of the reference light are equal based on the normal. In the non-tilted structure, the degree of deformation (e.g., shrinkage or expansion) under high temperature and high humidity conditions is more clearly identified compared to the tilted structure, and it is less affected by the shrinkage and expansion of the substrate.

[0160] Another embodiment of the hologram recording medium can have high diffraction efficiency. In one example, the hologram recording medium can have a diffraction efficiency of 70% or higher when recording a notch filter hologram. The thickness of the photopolymer layer can be, for example, from 5 μm to 30 μm. Specifically, when recording a notch filter hologram, the diffraction efficiency can be 71% or higher, 72% or higher, 73% or higher, 74% or higher, 75% or higher, 80% or higher, 81% or higher, 82% or higher, 83% or higher, 84% or higher, 85% or higher, 86% or higher, or 87% or higher. In this way, even if the hologram recording medium of another embodiment comprises a thin photopolymer layer, it can achieve excellent diffraction efficiency. The diffraction efficiency can be measured by the method described in Test Example 2 below.

[0161] Even with a photopolymer layer thickness as thin as 5 μm to 30 μm, another embodiment of the holographic recording medium can achieve refractive index modulation values ​​(Δn) of 0.020 or greater, 0.025 or greater, 0.026 or greater, 0.027 or greater, 0.028 or greater, 0.029 or greater, 0.030 or greater, 0.031 or greater, 0.032 or greater, 0.033 or greater, 0.034 or greater, or 0.035 or greater. There is no particular upper limit to the refractive index modulation value, but it can be, for example, 0.060 or less. The refractive index modulation value can be measured using the method described in Test Example 2 below.

[0162] Another embodiment of the holographic recording medium promises to provide a variety of optical elements that can be used at high temperatures, exhibiting not only excellent optical recording properties and high-temperature durability, but also high-transparency optical properties.

[0163] The use of the holographic recording medium in another embodiment is not particularly limited. As a non-limiting example, the holographic recording medium can be used in applications that may be exposed to high-temperature environments, specifically in smart devices such as mobile devices, components of wearable displays, and vehicle articles (e.g., head-up displays). The holographic recording medium in another embodiment exhibits excellent reliability at high temperatures, enabling it to maintain the expected optical recording characteristics even at high temperatures.

[0164] On the other hand, according to yet another embodiment of this disclosure, a method for preparing a holographic recording medium is provided, which includes the step of applying a photopolymer composition to form a photopolymer layer.

[0165] The photopolymer composition can be one embodiment of the photopolymer composition. Since its components have already been described in detail, a detailed description will be omitted here.

[0166] In the step of forming the photopolymer layer, a photopolymer composition comprising the above-described configuration can be prepared first. When preparing the photopolymer composition, known mixers, stirrers, or blenders can be used to mix the components without particular limitation. Furthermore, such a mixing process can be carried out at temperatures ranging from 0°C to 100°C, from 10°C to 80°C, or from 20°C to 60°C.

[0167] In the step of forming the photopolymer layer, the prepared photopolymer composition can be applied to form a coating formed by the photopolymer composition. The coating can be air-dried at room temperature or dried at a temperature between 30°C and 80°C. This process can induce a hydrosilylation reaction between the hydroxyl groups of the unreacted acrylic polyol and the silane functional groups of the siloxane-based polymer.

[0168] In the photopolymer layer prepared by the step of forming a photopolymer layer, fluorinated compounds, photoreactive monomers, photoinitiator systems, and additives added as needed can be uniformly dispersed in the crosslinked polymer matrix.

[0169] According to another embodiment, the method for preparing a holographic recording medium may further include, after the step of forming the photopolymer layer, a step of recording optical information by irradiating a predetermined area of ​​the photopolymer layer with a coherent laser and selectively polymerizing photoreactive monomers contained in the photopolymer layer.

[0170] In the step of recording optical information, if a coherent laser irradiates the photopolymer layer, the polymerization of photoreactive monomers occurs in the constructive interference region to form a photopolymer, while in the destructive interference region, the polymerization of photoreactive monomers does not occur or is inhibited, resulting in the presence of photoreactive monomers. Furthermore, as unreacted photoreactive monomers diffuse toward the photopolymer side with a lower concentration of photoreactive monomers, refractive index modulation occurs, generating a diffraction grating through refractive index modulation. Thus, a hologram (i.e., optical information) is recorded on the photopolymer layer with the diffraction grating.

[0171] According to another embodiment, the method for preparing a holographic recording medium may further include, after the step of recording optical information, a step of photobleaching by irradiating light onto the entire photopolymer layer on which the optical information is recorded.

[0172] In the photobleaching step, ultraviolet light is irradiated onto the photopolymer layer on which optical information has been recorded to terminate the reaction of the remaining photoreactive monomers in the photopolymer layer and remove the color of the photosensitive dye. In one example, in the photobleaching step, ultraviolet light (UVA) in the range of 320 nm to 400 nm is irradiated to terminate the reaction of the photoreactive monomers and remove the color of the photosensitive dye.

[0173] On the other hand, according to another embodiment of this disclosure, an optical element including the holographic recording medium is provided.

[0174] Specific examples of optical elements may include smart devices such as mobile devices, components of wearable displays, vehicle products (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflectors, filters, diffusers, diffraction elements, light guides, waveguides, holographic optical elements with projection screen and / or mask functions, media for optical storage systems and light diffusers, optical wavelength multiplexers, reflective color filters, transmissive color filters, etc.

[0175] Examples of optical elements that include the holographic recording medium may include a holographic display device. A holographic display device includes a light source unit, an input unit, an optical system, and a display unit.

[0176] Specifically, the light source unit is the part that illuminates the laser beam used to provide, record, and reproduce three-dimensional image information of the object in the input unit and the display unit.

[0177] The input unit is the part that pre-inputs the three-dimensional image information of the object to be recorded on the display unit. Specifically, three-dimensional information of the object, such as the intensity and phase of light in various spaces, can be input into the part of the electrically addressed liquid crystal SLM, where an input beam can be used.

[0178] The optical system may include mirrors, polarizers, beam splitters, beam gates, lenses, etc. The optical system can be configured as an input beam for sending a laser beam emitted from the light source unit to the input unit, a recording beam for sending the laser beam to the display unit, a reference beam, an erasing beam, a reading beam, etc.

[0179] The display unit can receive three-dimensional image information of an object from the input unit, record it on a hologram including an optically addressed SLM, and reconstruct the three-dimensional image of the object. At this time, the three-dimensional image information of the object can be recorded by the interference of the input beam and the reference beam. The three-dimensional image information of the object recorded on the hologram can be reconstructed into a three-dimensional image by the diffraction pattern generated by the readout beam. The eraser beam can be used to quickly remove the formed diffraction pattern. Furthermore, the hologram can be moved between the position of the input three-dimensional image and the position of the reconstructed three-dimensional image.

[0180] Beneficial effects

[0181] According to one embodiment of this disclosure, the photopolymer composition is capable of providing a holographic recording medium and optical elements comprising therein that not only exhibit excellent optical recording properties but also excellent reliability and transparency even at high temperatures. Attached Figure Description

[0182] Figure 1 The recording device setup for hologram recording is illustrated schematically. Specifically, Figure 1 The process is illustrated schematically as follows: a laser of a predetermined wavelength is radiated from a light source 10 and illuminates a PP (holographic recording medium) 80 located on a surface of a mirror 70 via mirrors 20 and 20', aperture 30, spatial filter 40, aperture 30', collimating lens 50 and PBS (Polarized Beam Splitter) 60. Detailed Implementation

[0183] In the following description, the effects and functions of the invention will be described in more detail with reference to specific embodiments thereof. However, these embodiments are presented for illustrative purposes only, and the scope of the invention is not limited thereto in any way.

[0184] In the following preparation examples, embodiments, comparative examples, etc., unless otherwise stated, the content of raw materials, etc., means the content based on the solid content.

[0185] Preparation Example 1: Preparation of Acrylic Polyols

[0186] 132 g of butyl acrylate, 420 g of ethyl acrylate, and 48 g of hydroxybutyl acrylate were added to a 2 L jacketed reactor and diluted with 1200 g of ethyl acetate. The reaction temperature was set to 60 °C to 70 °C, and the mixture was stirred for approximately 30 minutes to 1 hour. 0.42 g of n-dodecyl mercaptan (n-DDM) was then added, and stirring was continued for approximately 30 minutes. Then, 0.24 g of AIBN as a polymerization initiator was added, and polymerization was carried out at the reaction temperature for 4 hours or longer, continuing until the residual acrylate content became less than 1%. Thus, an acrylate-based copolymer in which hydroxyl groups are branched was prepared (weight-average molecular weight of approximately 300,000, OH equivalent of approximately 1802 g / equivalent).

[0187] Example 1: Preparation of photopolymer composition and holographic recording medium

[0188] (1) Preparation of photopolymer compositions

[0189] First, 0.57 g of poly(methylhydrosiloxane) (Sigma-Aldrich, number-average molecular weight: about 590, Si-H equivalent: about 103 g / equivalent) as a siloxane-based polymer and 33.4 g of acrylic polyol (solid content: 10.02 g) (solid content: 30 wt%) prepared in Preparation Example 1 were mixed (SiH / OH molar ratio = 1.0).

[0190] Then, 11.5 g of HR 6042 (Miwon Specialty Chemical, refractive index 1.60) as a photoreactive monomer, 0.08 g of the photosensitive dye H-Nu 640 (Spectra Group), 0.3 g of Borate V as a co-initiator, 11.5 g of a fluorinated compound represented by the following chemical formula a as a plasticizer, and 26 g of methyl isobutyl ketone (MIBK) as a solvent were added, and the mixture was stirred in a paste mixer for about 30 minutes while being protected from light. Subsequently, a photopolymer composition was prepared by adding a Karstedt (Pt-based) catalyst for matrix crosslinking.

[0191] [Chemical formula a]

[0192]

[0193] (2) Preparation of holographic recording media

[0194] The photopolymer composition was coated onto a 60 μm thick TAC substrate using a Mayer rod to a predetermined thickness and dried at 80°C for 10 minutes. The thickness of the dried photopolymer layer was approximately 10 μm.

[0195] Examples 2 and 3 and Comparative Examples 1 and 2: Preparation of photopolymer compositions and holographic recording media

[0196] The photopolymer composition and holographic recording medium were prepared in the same manner as in Example 1, except that the plasticizer was changed as shown in Table 1 below.

[0197] [Table 1]

[0198]

[0199] Test Example 1: Evaluation of the migration degree of holographic recording media

[0200] The migration of the holographic recording medium prior to recording was evaluated at multiple temperatures. Specifically, to evaluate the migration of the photopolymer layer at multiple temperatures, the refractive index from the surface to the center of the photopolymer layer was measured at multiple temperatures with an incident angle of 70° in the wavelength range of 320 nm to 1680 nm using a spectroscopic ellipsometer (Ellipso Technology).

[0201] The thickness (A1) of the anisorefractive layer exhibiting a refractive index difference of at least 0.0010% from the center refractive index of the photopolymer layer and the thickness (A2) of the remaining portion of the photopolymer layer were measured at multiple temperatures, and the values ​​are shown in Table 2 below.

[0202] Furthermore, the percentage (Pn) of the thickness (A1) of the anisorefractive layer relative to the total thickness (A1+A2) of the photopolymer layer at multiple temperatures was calculated according to Equation 1 below and is shown in Table 2 below.

[0203] [Equation 1]

[0204] Pn(%)={A1 / (A1+A2)}×100

[0205] In Equation 1, Pn represents the thickness ratio of the anisorefringent layer formed at n℃.

[0206] A1 represents the thickness of the anisorefringent layer formed at n °C, where the anisorefringent layer refers to the portion of the surface of the photopolymer layer exhibiting a refractive index difference of at least 0.0010% with the central refractive index measured at an incident angle of 70° in the wavelength range of 320 nm to 1680 nm.

[0207] A2 is the thickness of the remaining portion of the photopolymer layer excluding the anisorefractive layer.

[0208] [Table 2]

[0209]

[0210] Meanwhile, the migration of the holographic recording medium prior to recording was evaluated at multiple temperatures and wavelengths by measuring the refractive index at the center and surface of the photopolymer layer, as shown in Table 3 below. The refractive index was measured using the same equipment described above.

[0211] [Table 3]

[0212]

[0213] Referring to Tables 2 and 3, it is determined that a very thin anisotropic layer is formed in the photopolymer layer of Example 1, with negligible thickness, which does not affect the function of the holographic recording medium, and the absolute difference in refractive index between the center and the surface is also very small.

[0214] In contrast, it was determined that a significantly thicker anisotropic layer was formed in the photopolymer layer of Comparative Example 1, which would adversely affect the function of the holographic recording medium, and the absolute difference in refractive index between the center and the surface was also very large.

[0215] Test Example 2: Performance Evaluation of Holographic Recording Media

[0216] (1) P80 (the thickness ratio of the anisotropic layer formed at 80℃, %)

[0217] The migration of the holographic recording medium prior to recording was evaluated at high temperatures. Specifically, to assess the migration of the photopolymer layer at 80°C, the refractive index from the surface to the center of the photopolymer layer was measured at 80°C with an incident angle of 70° in the wavelength range of 320 nm to 1680 nm using a spectroscopic ellipsometer (Ellipso Technology).

[0218] Then, P80 (the thickness ratio of the anisotropic layer formed at 80°C) is calculated according to Equation 1 below and is shown in Table 4 below.

[0219] [Equation 1]

[0220] Pn(%)={A1 / (A1+A2)}×100

[0221] In Equation 1, Pn represents the thickness ratio of the anisorefringent layer formed at n℃.

[0222] A1 represents the thickness of the anisorefringent layer formed at n °C, where the anisorefringent layer refers to the portion of the surface of the photopolymer layer exhibiting a refractive index difference of at least 0.0010% with respect to the central refractive index measured at an incident angle of 70° in the wavelength range of 320 nm to 1680 nm.

[0223] A2 is the thickness of the remaining portion of the photopolymer layer excluding the anisorefractive layer.

[0224] (2) ΔH80 (the increase in haze at 80℃, %p)

[0225] Use and Figure 1 The same setup is used to record the diffraction grating. Specifically, when the prepared photopolymer layer is laminated onto a mirror and then irradiated with a laser, a notch filter hologram with periodic refractive index modulation in the thickness direction can be recorded by the interference between the incident light (L) and the light reflected from the mirror (L'). In this example, the notch filter hologram is recorded at an incident angle of 0°. Notch filters and Bragg reflectors are optical devices that reflect only light of a specific wavelength and have a structure in which two layers with different refractive indices are periodically and repeatedly stacked with a constant thickness.

[0226] The haze difference of a holographic recording medium with a diffraction grating was evaluated before and after high-temperature exposure. Haze was measured using a haze meter (HM-150) from Murakami Color Research Laboratory, according to JIS K 7136. Measurement light was incident on the substrate-side surface of the holographic recording medium.

[0227] Specifically, the holographic recording medium was stored at 80°C for 100 hours, and the haze difference before and after storage was calculated according to Equation 2 below. The haze increase (ΔH80) at 80°C is shown in Table 4 below.

[0228] [Equation 2]

[0229] ΔHn(%p)=B2-B1

[0230] In Equation 2, ΔHn represents the increase in haze of the holographic recording medium at n℃.

[0231] B1 represents the initial haze of the holographic recording medium before storage at n℃, and

[0232] B2 represents the haze of the holographic recording medium after 100 hours of storage at n℃.

[0233] (3) Diffraction efficiency

[0234] For a holographic recording medium containing a diffraction grating, the diffraction efficiency (η) is determined by the following Equation 3.

[0235] [Equation 3]

[0236] η(%)={P D / (P D +P T )}×100

[0237] In Equation 3, η is the diffraction efficiency, and P... D To record the output of the diffracted beam of the sample afterwards (mW / cm) 2 ), and P T To record the output of the transmitted beam of the sample afterward (mW / cm). 2 ).

[0238] (4) Refractive index modulation value (Δn)

[0239] For a holographic recording medium containing a diffraction grating, the refractive index modulation value (Δn) is determined using Equation 4 and Bragg's equation.

[0240] [Equation 4]

[0241]

[0242] [Bragg's Equation]

[0243]

[0244] In the equation, η is the reflection diffraction efficiency (DE), d is the thickness of the photopolymer layer, λ is the wavelength of the incident light used for recording (660 nm or 532 nm), θ is the incident angle of the incident light used for recording, φ is the tilt angle of the grating, Δn is the refractive index modulation value, n is the refractive index of the photopolymer, and Λ refers to the period of the diffraction grating. In the above embodiments and comparative examples, since the hologram is recorded using a notch filter method, both θ (incident angle) and φ (tilt angle of the grating) are 0°.

[0245] [Table 4]

[0246] Diffraction efficiency (%) Refractive index modulation value (Δn) P80(％) ΔH80(%p) Example 1 87 0.037 0.05 1.0 Example 2 85 0.035 0.07 0.7 Example 3 87 0.037 0.04 0.9 Comparative Example 1 52 0.022 0.44 15.2 Comparative Example 2 47 0.019 0.40 14.8

[0247] Referring to Table 4, the holographic recording media manufactured in Examples 1 to 3 were found to exhibit high diffraction efficiency and refractive index modulation values, as well as excellent high-temperature stability, resulting in minimal formation of anisorefractive layers and very little increase in haze. In contrast, the holographic recording media manufactured in Comparative Examples 1 and 2 were found to have poor optical recording characteristics, and in particular, thick anisorefractive layers formed at high temperatures, with a significant increase in haze.

[0248] Therefore, it has been determined that a photopolymer composition according to one embodiment of the present disclosure, by comprising a fluorinated compound having a specific structure, can provide a holographic recording medium exhibiting excellent optical recording properties, high-temperature stability, and high transparency.

Claims

1. A photopolymer composition comprising: A polymer matrix or its precursor formed by crosslinking a siloxane-based polymer containing silane functional groups with an acrylic polyol; Fluorinated compounds represented by the following chemical formula 1; Photoreactive monomers; as well as Photoinitiator system: [Chemical Formula 1] In chemical formula 1, Z 1 It is -O- or -NH-. Z 2 It is a single bond, -O- or -NH-. L 1 It is a single bond or a divalent to hexavalent organic group in which the hydroxyl groups have been removed from polyols having 2 to 6 hydroxyl groups. n and m are each independent integers from 1 to 5, where the sum of n and m is from 2 to 6. R 1 R 2 and R 3 Each is independently either methyl or ethyl. R 4 The fluorinated substituent is an alkyl group having 1 to 20 carbon atoms that has been substituted with 2 or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms that has been substituted with 2 or more fluorine atoms.

2. The photopolymer composition according to claim 1, wherein the siloxane-based polymer comprises a repeating unit represented by chemical formula 2 and a terminal group represented by chemical formula 3: [Chemical Formula 2] In chemical formula 2, Complex R 11 and R 12 They may be the same as or different from each other, and each is independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and k is an integer from 1 to 10,000. [Chemical Formula 3] In chemical formula 3, Complex R 13 To R 15 They may be the same as or different from each other, and each is independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and R is selected from at least one repeating unit of the repeating unit represented by chemical formula 2 and any one of the terminal groups of the terminal groups represented by chemical formula 3. 11 To R 15 At least one of them is hydrogen.

3. The photopolymer composition according to claim 1, wherein the acrylic polyol is a polymer in which hydroxyl groups are bonded to the main chain or side chain of an acrylate-based polymer.

4. The photopolymer composition according to claim 1, wherein the photoreactive monomer comprises: The monomer is selected from at least one monofunctional monomer chosen from the following: benzyl (meth)acrylate, 2-phenylbenzyl acrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, phenol (ethylene oxide)-2 (meth)acrylate, o-phenylphenol (ethylene oxide) (meth)acrylate, phenylthioethyl (meth)acrylate, and biphenyl methyl (meth)acrylate; bisphenol A (ethylene oxide) 2～10 At least one polyfunctional monomer selected from the following: di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tri(2-hydroxyethyl) isocyanurate tri(meth)acrylate, phenolic epoxy (meth)acrylate and cresol phenolic epoxy (meth)acrylate; or a mixture of two or more thereof.

5. The photopolymer composition according to claim 1, wherein the photoreactive monomer is included in an amount of 50 to 300 parts by weight based on 100 parts by weight of the polymer matrix.

6. The photopolymer composition according to claim 1, wherein the photoinitiator system comprises a photosensitive dye and a co-initiator.

7. The photopolymer composition according to claim 6, wherein the co-initiator comprises a borate anion represented by the following chemical formula 4: [Chemical Formula 4] BX 1 X 2 X 3 X 4 In chemical formula 4, X 1 To X 4 Each is independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, provided that X 1 To X 4 At least one of them is not an aryl.

8. The photopolymer composition according to claim 1, wherein L in formula 1 1 It is a single bond; or a trivalent organic group in which the hydroxyl group has been removed from glycerol which is a triol.

9. The photopolymer composition according to claim 1, wherein the fluorinated substituent is a straight-chain alkyl group having 1 to 20 carbon atoms that has been substituted with 2 or more fluorine atoms.

10. The photopolymer composition according to claim 1, wherein the fluorinated substituent is -(CH2). a (CF2) b CHF2 or -(CH2) a (CF2) b CF3, where a is an integer from 0 to 3, and b is an integer from 0 to 19.

11. The photopolymer composition according to claim 1, wherein the fluorinated compound represented by chemical formula 1 comprises at least one fluorinated compound selected from the following fluorinated compounds represented by chemical formulas 1-1 and 1-2: [Chemical Formula 1-1] In chemical formula 1-1, Z 1' R 1' R 2' R 3' and R 4' Each is related to Z in chemical formula 1 1 R 1 R 2 R 3 and R 4 same, [Chemical Formula 1-2] In chemical formulas 1-2, Z 1” Z 2” R 1” R 2” R 3” and R 4” Z, respectively with chemical formula 1 1 Z 2 R 1 R 2 R 3 and R 4 same.

12. The photopolymer composition according to claim 1, wherein the fluorinated compound represented by chemical formula 1 is included in an amount of 20 to 200 parts by weight based on 100 parts by weight of the polymer matrix.

13. A holographic recording medium comprising a photopolymer layer formed from the photopolymer composition according to claim 1.

14. A method for preparing a holographic recording medium, comprising the step of applying the photopolymer composition according to claim 1 to form a photopolymer layer.

15. The method of claim 14, further comprising the step of recording optical information by irradiating a predetermined region of the photopolymer layer with a coherent laser and selectively polymerizing the photoreactive monomers contained in the photopolymer layer.

16. An optical element comprising the holographic recording medium according to claim 13.

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