Holographic recording medium and optical element containing the same

Abstract

This application relates to a holographic recording medium and an optical element including the same. The holographic recording medium not only has excellent optical recording characteristics but can also exhibit excellent reliability and transparency even in high-temperature environments.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority under Korean Patent Application No. 10-2024-0022506 dated February 16, 2024, and all content disclosed in the said Korean Patent Application is incorporated herein as part of this specification.

[0002] This application relates to a holographic recording medium and an optical element including the same. [Background technology]

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

[0004] In this regard, photopolymer compositions can be used in the manufacture of holograms. Photopolymers can easily store optical interference patterns as holograms by photopolymerization of photoreactive monomers. Therefore, photopolymers can be used in a variety of fields, such as smart devices like mobile devices, components of wearable displays, automotive accessories (e.g., head-up displays), holographic fingerprint recognition systems, holographic optical elements having the functions of optical lenses, mirrors, deflectors, filters, diffusion screens, diffracting members, light guides, waveguides, projection screens and / or masks, media and light diffusers for optical memory systems, optical wavelength dividers, and reflective and transmissive color filters.

[0005] Specifically, the photopolymer composition for hologram production comprises a polymer matrix, photoreactive monomers, and a photoinitiator system. A photopolymer layer produced from such a composition is then irradiated with laser interference light to induce localized photopolymerization of the monomers.

[0006] Such localized photopolymerization processes lead to refractive index modulation, which in turn generates a diffraction grating. The refractive index modulation value (△n) is influenced by the thickness of the photopolymer layer and the diffraction efficiency (DE), and the angular selectivity widens as the thickness decreases.

[0007] Recently, there has been a growing demand for materials that offer high diffraction efficiency and can stably maintain holograms. As a result, various attempts are being made to manufacture holographic recording media that are thin yet possess high diffraction efficiency and refractive index modulation values.

[0008] On the other hand, when holographic recording media are used as optical elements in applications such as mobile devices and vehicle accessories (e.g., head-up displays), they are exposed to high-temperature environments. In this case, deformation of the diffraction grating occurs, causing image distortion or preventing the intended function from being performed. Therefore, there is a need to develop photopolymer layers and holographic recording media containing them that exhibit minimal deformation of the diffraction grating despite the heat of the operating environment and offer excellent reliability. [Overview of the project] [Problems that the invention aims to solve]

[0009] According to one embodiment of the present invention, a holographic recording medium is provided.

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

[0011] The following describes specific embodiments of the invention, including a holographic recording medium and an optical element containing the same.

[0012] In this specification, "hologram recording medium" means a medium (or media) capable of recording optical information in the entire visible light range and ultraviolet range (e.g., 300-1,200 nm) through an exposure process, unless otherwise specified. Therefore, the hologram recording medium in this specification may mean a medium on which optical information has been recorded, or a pre-recording medium in a state capable of recording optical information. The holograms in this specification may include all visual holograms, such as inline (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white light transmission holograms ("rainbow holograms"), Denisyuk holograms, off-axis reflection holograms, edge-literature holograms, or holographic stereograms.

[0013] In this specification, in relation to the environmental conditions in which a holographic recording medium or an element containing the same is placed, “high temperature” may mean a temperature of 60°C or higher. For example, such high temperature may mean a temperature of 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 for example, it may be 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. If temperature affects the characteristics of a substance, article or each component, unless otherwise specified, the temperature conditions under which such characteristics are measured or described may mean room temperature (e.g., a temperature in the range of about 15 to 30°C, where no particular cooling or heating is performed).

[0014] In this specification, unless otherwise specified, the measured values ​​should be understood as measurements of the photopolymer layer contained in the holographic recording medium.

[0015] According to one embodiment of the invention, a holographic recording medium is provided, comprising a polymer matrix or precursor formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine compound, wherein the P80, which is Pn measured at 80°C according to the following formula 1, is 0.10% or less.

[0016] [Formula 1] Pn(%) = {A1 / (A1+A2)} × 100

[0017] In the above formula 1, Pn is the thickness ratio of the different refractive index layers formed at n°C. A1 is the thickness of the differential refractive index layer formed at n°C, and the differential refractive index layer refers to the surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm. A2 is the thickness of the remaining portion of the photopolymer layer after removing the different refractive index layer.

[0018] The inventors have completed the present invention by confirming that, when a specific photopolymer layer is included, it is possible to provide a holographic recording medium that exhibits improved optical recording characteristics while also showing high reliability and high transparency even at high temperatures.

[0019] The following describes in detail a holographic recording medium and an optical element including the holographic recording medium according to one embodiment of the present invention.

[0020] The holographic recording medium of the above embodiment comprises a polymer matrix or its precursor formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine compound.

[0021] The aforementioned photopolymer layer may be a photopolymer layer in a pre-recording state capable of recording optical information, or a photopolymer layer in a state where optical information has been recorded.

[0022] A photopolymer layer with recorded optical information can be manufactured by irradiating a pre-recorded photopolymer layer with object light and reference light. When a pre-recorded photopolymer layer is irradiated with object light and reference light, the photoinitiator system is inactive in the canceling interference region due to the interference length of the object light and reference light, so photopolymerization of photoreactive monomers does not occur. In the reinforcing interference region, photopolymerization of photoreactive monomers occurs due to the activated photoinitiator system. In the reinforcing interference region, the photoreactive monomers are continuously consumed, creating a concentration difference between the canceling and reinforcing interference regions. As a result, the photoreactive monomers in the canceling interference region diffuse into the reinforcing interference region. At this time, the fluorine-based compound, which is a plasticizer, moves in the opposite direction to the photoreactive monomers. Since the photoreactive monomers and the photopolymers formed therefrom have a higher refractive index than the polymer matrix and the fluorine-based compound, a spatial change in refractive index occurs in the photopolymer layer, and a lattice is generated by this spatial refractive index modulation in the photopolymer layer. Such lattice surfaces act as reflective surfaces that reflect incident light due to differences in refractive index. After hologram recording, when light of the same wavelength as the recording is incident in the direction of the reference light, the Bragg condition is satisfied, and the light diffracts in the direction of the original object light, allowing the hologram optical information to be reconstructed.

[0023] Therefore, if the photopolymer layer is in its pre-recording state, the photopolymer layer may contain the photoreactive monomer, photoinitiator system, and fluorine-based compound in a form in which they are randomly dispersed within the polymer matrix or its precursor.

[0024] In contrast, if optical information is recorded in the photopolymer layer, the photopolymer layer may contain a photopolymer and a fluorine-based compound distributed to form a lattice with the polymer matrix.

[0025] The photopolymer layer is formed from a photopolymer composition comprising a polymer matrix or its precursor formed by crosslinking a siloxane polymer containing silane functional groups and an acrylic polyol; a photoreactive monomer and a photoinitiator system; and a fluorine-based compound.

[0026] The polymer matrix serves as a support for the photopolymer layer and is formed by crosslinking a siloxane polymer containing silane functional groups (Si-H) and an acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking an acrylic polyol with a siloxane polymer containing silane functional groups. 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. This hydrosilylation reaction can be carried out rapidly at room temperature (for example, at a temperature in the range of about 15 to 30°C without heating or deheating) under a Pt-based catalyst. Therefore, the photopolymer composition of the above embodiment can improve the manufacturing efficiency and productivity of holographic recording media by employing a polymer matrix that can be rapidly crosslinked at room temperature as a support.

[0027] The polymer matrix, through the flexible main chain of the siloxane polymer, can enhance the mobility of components contained in the photopolymer layer (e.g., photoreactive monomers or plasticizers). Furthermore, the siloxane bonds, which have excellent heat and moisture resistance, facilitate the assurance of reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium containing it.

[0028] The polymer matrix may have a relatively low refractive index, thereby playing a role in enhancing the refractive index modulation of the photopolymer layer. 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, "refractive index" may be a value measured with an Abbe refractometer at 25°C.

[0029] The photopolymer layer may contain or include a precursor of the crosslinked polymer matrix described above. If the photopolymer layer contains a precursor of the polymer matrix, it may include a siloxane polymer, an acrylic polyol, and a Pt-based catalyst.

[0030] The siloxane polymer may, as an example, include a repeating unit represented by the following chemical formula 1 and a terminal group represented by the following chemical formula 2.

[0031] [ka]

[0032] In the aforementioned chemical formula 1, Multiple R 11 and R 12 These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. k is an integer between 1 and 10,000.

[0033] [ka]

[0034] In the aforementioned chemical formula 2, Multiple R 13 ~R 15are the same as or different from each other, and each independently is hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, at least one repeating unit selected from the repeating units represented by the chemical formula 1, and R of any one of the end groups selected from the end groups represented by the chemical formula 2 11 ~R 15 at least one of is hydrogen.

[0035] In the chemical formula 2, -(O)- means that when Si of the end group represented by the chemical formula 2 is bonded to the repeating unit represented by the chemical formula 1, it is bonded via oxygen (O) or directly bonded without oxygen (O).

[0036] In the present specification, the "alkyl group" may be a straight-chain, branched-chain or cyclic alkyl group. As non-limiting examples, in the present specification, the "alkyl group" is 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-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.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), etc.

[0037] As an example, R of the chemical formulas 1 and 2 11 ~R 15 are methyl or hydrogen, and a plurality of R 11 ~R 15At least two of them may be hydrogen. More specifically, the siloxane polymer may be R of chemical formula 1. 11 and R 12 These are methyl and hydrogen, respectively, and R in the chemical formula 2. 13 ~R 15 Compounds in which each is independently methyl or hydrogen (for example, polymethylhydrosiloxanes whose terminal group is a trimethylsilyl group or a dimethylhydrosilyl group); R of part of the above chemical formula 1 11 and R 12 These are methyl and hydrogen, respectively, and the remaining R 11 and R 12 All are methyl, and R of the above chemical formula 2 13 ~R 15 Compounds in which each is independently methyl or hydrogen (for example, poly(dimethylsiloxane-co-methylhydrosiloxane) whose terminal group is a trimethylsilyl group or a dimethylhydrosilyl group; or R of the above chemical formula 1) 11 and R 12 All are methyl, and R of the above chemical formula 2 13 ~R 15 The compound may be one in which at least one of the terminal groups is hydrogen and the rest are independently methyl or hydrogen (for example, a polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0038] The siloxane-based compound may, for example, have a number-average molecular weight (Mn) in the range of 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, it is possible to prevent problems such as the siloxane-based polymer volatilizing during the crosslinking process with the acrylic polyol carried out at room temperature or above, resulting in a low degree of matrix crosslinking, or the siloxane-based polymer having poor compatibility with other components of the photopolymer layer, leading to phase separation with such components, thereby enabling the holographic recording medium to exhibit excellent optical recording characteristics and excellent durability under high-temperature conditions.

[0039] The aforementioned number-average molecular weight refers to the number-average molecular weight (unit: g / mol) on a polystyrene basis, measured by the GPC method. In the process of measuring the polystyrene-based number-average molecular weight measured by the GPC method, commonly known analytical instruments, detectors such as differential index detectors, and analytical columns can be used, and commonly applied 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.

[0040] The aforementioned acrylic polyol can mean a polymer in which one or more, specifically two or more hydroxyl 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 acryloyl groups, methacryloyl groups, and their derivatives, or to repeating units formed by the polymerization thereof, and unless otherwise specified, "acrylate" refers to one or more selected from acrylate and methacrylate, or to repeating units formed by the polymerization thereof.

[0041] The acrylic polyol may be a homopolymer of acrylate monomers having hydroxyl groups, a copolymer of acrylate monomers having two or more hydroxyl groups, or a copolymer of an acrylate monomer having hydroxyl groups and an acrylate monomer not having hydroxyl groups. In this specification, unless otherwise specified, "copolymer" is a term that encompasses random copolymers, block copolymers, and graft copolymers.

[0042] Examples of the acrylate monomer having a hydroxyl group include hydroxyalkyl (meth)acrylate or hydroxyaryl (meth)acrylate, where the alkyl is 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 hydroxyl group include alkyl (meth)acrylate or aryl (meth)acrylate, where the alkyl is 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" refers to acrylate and / or methacrylate unless otherwise specified.

[0043] The acrylic polyol may, for example, have a weight-average molecular weight (Mw) in the range of 150,000 to 1,000,000. The weight-average molecular weight refers to the weight-average molecular weight in polystyrene terms, measured by the GPC method as 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, 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 the acrylic polyol satisfies the above range, the polymer matrix fully performs its function as a support, resulting in minimal decrease in recording characteristics for optical information even after extended use. This imparts sufficient flexibility to the polymer matrix, improving the mobility of components contained in the photopolymer composition (e.g., photoreactive monomers or plasticizers), thereby minimizing the decrease in recording characteristics for optical information.

[0044] In order to adjust the crosslinking density of the acrylic polyol by the siloxane polymer to a level advantageous for ensuring the functionality of the holographic recording medium, the hydroxyl group equivalent of the acrylic polyol can be adjusted to an appropriate level.

[0045] Specifically, the hydroxyl group (-OH) equivalent of the acrylic polyol may be, for example, in the range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl group (-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. Furthermore, the upper limit of the hydroxyl group (-OH) equivalent 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 group (-OH) equivalent of the acrylic polyol is the equivalent amount (g / equivalent) per hydroxyl functional group, and is the value obtained by dividing the weight-average molecular weight of the acrylic polyol by the number of hydroxyl functional groups per molecule. The smaller the equivalent value, the higher the density of the functional group, and the larger the equivalent value, the lower the density of the functional group. When the hydroxyl group (-OH) equivalent of the acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslinking density and fully performs its role as a support, improving the fluidity of the components contained in the layer formed from the photopolymer composition. This prevents the breakdown of the diffraction grating interface after recording, maintains the initial refractive index modulation value at an excellent level even after time has passed, and minimizes the decrease in recording characteristics for optical information.

[0046] The acrylic polyol may have a glass transition temperature (Tg) in the range of -60 to -10°C, for example. 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 range is satisfied, 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 composition 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).

[0047] 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 range described above, 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 the production of the acrylic polyol (value measured using an Abbe refractometer at 25°C) and the fraction (molar ratio) of each monomer.

[0048] The acrylic polyol and siloxane polymer can be used such that the molar ratio (SiH / OH) of the silane functional group (Si-H) of the siloxane polymer to the hydroxyl group (-OH) of the acrylic polyol is 0.80 to 3.5. In other words, when forming the polymer matrix, the type and content of the siloxane polymer and acrylic polyol can be selected to satisfy the above 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 above molar ratio (SiH / OH) range is satisfied, the polymer matrix is ​​crosslinked with an appropriate crosslinking density, improving reliability under high-temperature conditions and enabling the achievement of a sufficient refractive index modulation value.

[0049] The Pt-based catalyst may, for example, be Karstedt's catalyst. The polymer matrix precursor may, if necessary, additionally contain non-metallic catalysts such as 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 catalysts, in addition to the Pt-based catalyst.

[0050] On the other hand, the photoreactive monomer may include compounds having a higher refractive index than the polymer matrix in order to achieve the refractive index modulation described above. However, it is not limited to all photoreactive monomers included in the photopolymer composition of the above embodiment having a higher refractive index than the polymer matrix, and at least some of the photoreactive monomers may have a higher refractive index than the polymer matrix in order to achieve a high refractive index modulation value. For example, the photoreactive monomer may include monomers with refractive indices of 1.50 or higher, 1.51 or higher, 1.52 or higher, 1.53 or higher, 1.54 or higher, 1.55 or higher, 1.56 or higher, 1.57 or higher, 1.58 or higher, 1.59 or higher, or 1.60 or higher and 1.70 or lower.

[0051] 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.

[0052] The monofunctional monomer may include, for example, one or more selected from the group consisting of benzyl (meth)acrylate (Miwon M1182 refractive index 1.5140), benzyl 2-phenyl acrylate, phenoxybenzyl (meth)acrylate (Miwon M1122 refractive index 1.565), phenol (ethylene oxide) (meth)acrylate (phenol(EO)(meth)acrylate; Miwon M140 refractive index 1.516), phenol (ethylene oxide) 2 (meth)acrylate (phenol(EO)2(meth)acrylate; Miwon M142 refractive index 1.510), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol(EO)(meth)acrylate; Miwon M1142 refractive index 1.577), phenylthioethyl (meth)acrylate (Miwon M1162 refractive index 1.560), and biphenylmethyl (meth)acrylate.

[0053] The aforementioned 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), Bisful Orange (meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR604 It may contain one or more substances selected from the group consisting of (2 refractive index 1.600), modified bisphenol full orange (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).

[0054] The photopolymer layer may contain 50 to 300 parts by weight of photoreactive monomers per 100 parts by weight of the polymer matrix. 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. In this case, the content of the standard polymer matrix refers to the combined content (by weight) of acrylic polyol and siloxane polymer that form the matrix. Satisfying the above range is advantageous in ensuring excellent optical recording characteristics and durability in high-temperature environments.

[0055] In this specification, the polymer matrix content refers to the combined content (by weight) of the acrylic polyol and siloxane polymer that form the matrix. In other words, the polymer matrix content includes both the polymer matrix formed by the crosslinking of the acrylic polyol and siloxane polymer, and the polymer matrix precursor that is not partially crosslinked.

[0056] The photopolymer layer includes a photoinitiator system. The photoinitiator system can mean a combination of a photoinitiator or photosensitizer and a coinitiator that enables polymerization to be initiated by light.

[0057] The photopolymer layer may include a photosensitizer and a co-initiator as a photoinitiator system.

[0058] For example, a photosensitive dye can be used as the photosensitizer. Specifically, the aforementioned photosensitive dyes include, for example, silicon rhodamine compounds, sulfonium derivatives of ceramidenin, new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose bengal, thionine, basic yellow, pinacyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, Quinaldine Red, and crystal violet. One or more substances selected from the group consisting of violet, Brilliant Green, Astrazon Orange G, Darrow Red, Pyronin Y, Basic Red 29, Pyrylium I (pyrylium iodide), Safranin O, Cyanine, Methylene Blue, Azure A, and BODIPY may be used.

[0059] As an example, the photosensitive dye can be a cyanine dye such as Cy3 and Cy5 (H-Nu640, Spectra), or safranin O can be used.

[0060] The photopolymer layer may contain the photosensitive dye 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 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 range is satisfied, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording characteristics.

[0061] The co-initiator may be an electron donor, an electron acceptor, or a mixture thereof.

[0062] As an example, the photopolymer layer may contain an electron donor as a co-initiator. The electron donor may, for example, include a borate anion represented by the following chemical formula 3.

[0063] [Chemical formula 3] BX 1 X 2 X 3 X 4

[0064] In the aforementioned chemical formula 3, X 1 ~X 4 Each of these is independently a substituted or unsubstituted C1-C20 alkyl group, a C2-C20 alkenyl group, a C6-C30 aryl group, a C7-C30 arylalkyl (arylalkyl) group, a C7-C30 alkylaryl (alkylaryl) group, or an allyl group, and X 1 ~X 4 At least one of them is not an aryl group.

[0065] When the C1-C20 alkyl group, C2-C20 alkenyl group, C6-C30 aryl group, C7-C30 arylalkyl (arylalkyl) group, C7-C30 alkylaryl (alkylaryl) group, or allyl group is substituted, it may be substituted with one or more selected from the group consisting of halogens and C1-C5 alkoxy groups.

[0066] Specifically, X 1 ~X 3 Each of these is independently halogen-substituted or unsubstituted methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, cyclobutyl, cyclopentyl, cyclohexyl, ethenyl, propenyl, phenyl, methylphenyl, methoxyphenyl, naphthyl, methylnaphthyl, or methoxynaphthyl, and X 4 This may be n-butyl, n-pentyl, or n-hexyl. More specifically, the borate anion represented by chemical formula 3 may be, for example, a triphenylbutyl borate anion.

[0067] 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 means an ammonium cation in which nitrogen (N) is substituted with four substituents, and each of the four substituents may independently be a C1-C40 alkyl group, a C6-C30 aryl group, a C6-C40 arylalkyl group, or a C2-C40 alkyl group linked via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3).

[0068] As the electron donor, for example, commercially available butyryl choline triphenylbutylborate (Borate V, manufacturer: Spectra group) can be used.

[0069] As an example, the photopolymer layer may contain an electron acceptor as a co-initiator. The electron acceptor may include, for example, an onium salt such as a sulfonium salt, an iodonium salt, or a mixture thereof.

[0070] As an example, the electron acceptor may include an iodonium salt. For example, commercially available H-Nu254 (Spectra) can be used as the electron acceptor.

[0071] The photopolymer layer may contain the co-initiator in an amount of 0.05 to 10 parts by weight per 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, 0.2 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 range is satisfied, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording characteristics.

[0072] The photoinitiator system may include additional photoinitiators to remove the color of the photosensitive dye and to react all unreacted photoreactive monomers after light irradiation for recording. Examples of photoinitiators include acetophenone compounds, oxime compounds, phosphine oxide compounds, thioxanthone compounds, benzoic acid ester compounds, imidazole compounds, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, amine derivatives, diazonium salts, sulfonium salts, iodonium salts, sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl)iron(II), benzointosylate, 2,5-dinitrobenzyltosylate, N-tosylphthalimide, or mixtures thereof.

[0073] More specifically, the photoinitiators 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-carbazole-3-yl]ethanone-1-(O-acetyloxime) (Irgacure OXE02, BASF), [(Z)-(1-oxo-1-phenylpropan-2-ylidene)amino]benzoate (such as 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-diphenylethane-1-one (Irgacure 651), 1-hydroxycyclohexyl-phenyl ketone (Irgacure 184), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-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 (in the USA).

[0074] The photopolymer layer contains a fluorine-based compound as a plasticizer. The plasticizer facilitates refractive index modulation during the manufacturing of the holographic recording medium. More specifically, the plasticizer lowers the glass transition temperature of the polymer matrix, improving the fluidity of photoreactive monomers. It has low refractive index and non-reactive properties, is uniformly distributed within the polymer matrix, and contributes to refractive index modulation by moving in the opposite direction to the movement of photoreactive monomers that have not been photopolymerized. The plasticizer can also contribute to improving the moldability of the photopolymer composition.

[0075] The fluorine-based compound may have a low refractive index of 1.45 or less in order to perform the function of a plasticizer as described above. 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, 1.39 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 lower refractive index than the photoreactive monomer described above, the refractive index of the polymer matrix can be made even lower, and the refractive index modulation with the photoreactive monomer can be made larger.

[0076] The non-reactive plasticizer is dispersed within the polymer matrix that supports the photopolymer layer without chemically bonding to it. This allows the non-reactive plasticizer to migrate to the surface of the photopolymer layer depending on the environment in which the holographic recording medium is used, and this migration is particularly easy at high temperatures. The plasticizer that migrates to the surface in this way forms a layer of different refractive indices on the surface of the photopolymer layer, and such a layer of different refractive indices is a major cause of deterioration in the reliability of the holographic recording medium.

[0077] The holographic recording medium according to the above embodiment may contain a branched fluorine-based compound that exhibits little to no migration to the surface of the photopolymer layer even in high-temperature environments. As a result, a layer of different refractive indices formed by the migration of plasticizers in the photopolymer layer to the surface is not formed or is formed at a very low level, allowing for clear reproduction of the intended image even at high temperatures and exhibiting high transparency.

[0078] The holographic recording medium of the above embodiment may have a sufficiently low Pn value calculated by the following formula 1. For example, the holographic recording medium of the above embodiment may have a P80 (thickness ratio of different refractive index layers formed at 80°C) of 0.10% or less, calculated by the following formula 1.

[0079] [Formula 1] Pn(%) = {A1 / (A1+A2)} × 100

[0080] In the above formula 1, Pn is the thickness ratio of the different refractive index layers formed at n°C. A1 is the thickness of the differential refractive index layer formed at n°C, and the differential refractive index layer refers to the surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm. A2 is the thickness of the remaining portion of the photopolymer layer after removing the different refractive index layer.

[0081] The aforementioned differential refractive index layer refers to the surface portion of the photopolymer layer that exhibits a refractive index different from the central refractive index of the photopolymer layer, and specifically refers to the portion that shows a refractive index difference of 0.0010% or more from the central refractive index. For example, if the central refractive index of the photopolymer layer is 1.5, the differential refractive index layer can be defined based on a boundary where the refractive index is 0.000015 (=1.5 × 0.00001) or more higher than 1.5, or lower.

[0082] The thickness (A1) of the differential refractive index layer is determined by measuring the refractive index from the surface to the center of the photopolymer layer within the wavelength range of 320 to 1680 nm and using the above formula 1. The thickness (A1) of the differential refractive index layer is determined by the thickness at the wavelength within the wavelength range of 320 to 1680 nm at which the thickness (A1) of the differential refractive index layer is observed to be the thickest.

[0083] A P80 value of 0.10% or less means that even when the holographic recording medium is exposed to high temperatures of 80°C, migration of fluorinated compounds to the surface is suppressed, and the degree of formation of a different refractive index layer due to the migration of fluorinated compounds is minimal. Therefore, when the Pn calculated by Equation 1 above shows a sufficiently low value, the holographic recording medium can reproduce the intended image clearly without any decrease in image reproduction capability, even at high temperatures.

[0084] The upper limit of P80 may 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. The lower limit may be, for example, 0% or more.

[0085] The method and detailed conditions for measuring the refractive index and other parameters for calculating Pn in Equation 1 above can be found in Test Example 1, described later. Pn in Equation 1 above may also be the thickness ratio of the different refractive index layer formed at n°C relative to the hologram recording medium before recording.

[0086] The holographic recording medium of the above embodiment may have a small difference in refractive index between the center and the surface. For example, at 80°C, the difference in refractive index between the center of the photopolymer layer and the surface with a thickness of 0.05% or less may be 0.080 or less.

[0087] The difference in refractive index between the center of the photopolymer layer and the surface up to 0.05% thick at 80°C may 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. The lower limit of the refractive index difference is not particularly limited and may be 0 or greater, or 0.001 or greater. For the method and detailed conditions for measuring the refractive index, refer to the contents described in Test Example 1 below.

[0088] Holographic recording media use a mixture of components with low refractive index and components with high refractive index for recording optical properties, and due to the mismatch between these components, they tend to exhibit opacity. Furthermore, at high temperatures, the decomposition and migration of plasticizers, which are components with low refractive index, to the surface further contribute to the opacity of holographic recording media.

[0089] However, the holographic recording medium of the above embodiment can maintain excellent transparency even when exposed to high temperatures by using a branched fluorine-based compound as a plasticizer, which minimizes decomposition and migration at high temperatures and exhibits excellent compatibility with components having a high refractive index.

[0090] Specifically, the holographic recording medium of the above embodiment can have a sufficiently low value for ΔHn, calculated by the following formula 2. For example, the holographic recording medium of the above embodiment may have a ΔH80 (haze rise at 80°C), calculated by the following formula 2, of 10%p or less.

[0091] [Formula 2] △Hn(%p)=B2-B1

[0092] In equation 2 above, △Hn is the haze rise of the hologram recording medium at n°C. B1 is the initial haze of the hologram recording medium before being left at n°C. B2 is the haze of the holographic recording medium after it has been left at n°C for 100 hours.

[0093] The fact that ΔH80 is 10%p or less means that even when the holographic recording medium is exposed to a high temperature of 80°C, the migration of fluorine-based compounds to the surface is suppressed, resulting in a small increase in haze. Therefore, if ΔHn calculated by equation 2 above shows a sufficiently low value, the holographic recording medium can exhibit transparent optical properties even at high temperatures.

[0094] The upper limit of △H80 may 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. The lower limit of the haze rise is not particularly limited and may be 0%p or more. The haze rise can be measured by the method described in Test Example 2 below. In Formula 2 above, △Hn may represent the haze rise at n°C for the hologram recording medium after recording.

[0095] As an example, the holographic recording medium according to the above embodiment may include the compound represented by the following chemical formula 4a as the branched fluorine-based compound.

[0096] [ka]

[0097] In the aforementioned chemical formula 4a, Z a1 is -O- or -NH-, Z a2 These are single bonds, -O- or -NH-, L a1 This is a single bond or a divalent to hexavalent organic group obtained by removing a hydroxyl group from a polyol having 2 to 6 alcohol groups. na and ma are independent integers between 1 and 5, and the sum of na and ma is between 2 and 6. R a1 , R a2 and R a3 These are independently either a methyl group or an ethyl group, R a4 This is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines.

[0098] In the chemical formula 4a, L a1 This consists of a part containing a carbonyl group (moiety) and R a4 The part containing is joined together. Therefore, the sum of na and ma is 2 to 6, L a1 This is the same as the number of connections.

[0099] As an example, in the above chemical formula 4a, L a1 L may be a single bond. In the above chemical formula 4a, a1 When it is a single bond, na and ma are each 1, and Z a2 It may also be a single bond. In this case, the fluorine-based compound represented by chemical formula 4a may also be represented by the following chemical formula 4a-1.

[0100] [ka]

[0101] In the aforementioned chemical formula 4a-1, Z a1’ , R a1’ , R a2’ , R a3’ and R a4’ These are the Z of chemical formula 4a mentioned above. a1 , R a1 , R a2 , R a3 and R a4 It is identical to the above Z a1’ , R a1’ , R a2’ , Ra3’ and R a4’ In this specification, Z of chemical formula 4a a1 , R a1 , R a2 , R a3 and R a4 The substituents described as specific examples may also be substituents.

[0102] As another example, in the above chemical formula 4a, L a1 The hydroxyl group of the polyol having 2 to 6 alcohol groups is Z a1 and Z a2 The polyol may be a divalent to hexavalent organic group from which a hydroxyl group has been removed by substitution. For example, glycerol having three alcohol groups.

[0103] [ka]

[0104] A trivalent organic group from which a hydroxyl group has been removed is

[0105] [ka]

[0106] It is expressed as follows.

[0107] In the chemical formula 4a, the L a1 This may be, for example, a divalent organic group obtained by removing a hydroxyl group from a diol such as ethanediol, propanediol, or butanediol; a trivalent organic group obtained by removing a hydroxyl group from a triol such as glycerol or trimethylolpropane; a tetravalent organic group obtained by removing a hydroxyl group from a tetraol such as pentaerythritol or ditrimethylolpropane; a pentavalent organic group obtained by removing a hydroxyl group from a pentaol such as 6-methylheptanepentaol; or a hexavalent organic group obtained by removing a hydroxyl group from a hexaol such as dipentaerythritol.

[0108] In the chemical formula 4a, L a1 is a single bond or, when it is a divalent organic group, na and ma are each 1. In case the L a1 is a trivalent to hexavalent organic group, na may be larger than ma. As an example, the na may be an integer from 1 to 3, and ma may be an integer of 1.

[0109] As an example, the L a1 may be a trivalent organic group in a form in which a hydroxy group is removed from glycerol which is a triol. And na may be 2, and ma may be 1. In this case, the fluorine-based compound represented by the chemical formula 4a may be represented by the following chemical formula 4a-2.

[0110] [Chemical formula]

[0111] In the chemical formula 4a-2, Z a1” , Z a2” , R a1” , R a2” , R a3” and R a4” are respectively the same as Z a1 , Z a2 , R a1 , R a2 , R a3 and R a4 in the chemical formula 4a. The Z a1” , Z a2” , R a1” , R a2” , R a3” and R a4” may be substituents described as specific examples of Z a1 , Z a2 , R a1 , R a2 , R a3 and R a4 in the chemical formula 4a in this specification.

[0112] In the chemical formula 4a, the fluorine-containing substituent may be a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. Specifically, the fluorine-containing substituent may be a C1-C20 linear alkyl group substituted with two or more fluorines. More specifically, the fluorine-containing substituent may be -(CH2) a (CF2) b CHF2 or -(CH2) a (CF2) b CF3 may also be used. Here, a is an integer between 0 and 3, an integer between 0 and 2, or an integer of 1, and b may be an integer between 0 and 19, an integer between 0 and 15, an integer between 0 and 12, an integer between 0 and 11, an integer between 0 and 10, or an integer between 0 and 9.

[0113] On the other hand, as another example, the holographic recording medium according to the above embodiment may include, as the branched fluorine-based compound, a compound represented by the following chemical formula 4b.

[0114] [ka]

[0115] In the aforementioned chemical formula 4b, Z b1 is -O- or -NH-, Z b2 These are single bonds, -O- or -NH-, L b1 This is a single bond or a divalent to hexavalent organic group obtained by removing a hydroxyl group from a polyol having 2 to 6 alcohol groups. nb and mb are independent integers between 1 and 5, and the sum of nb and mb is between 2 and 6. R b1 This is a methyl group or an ethyl group, R b2 ~R b4At least one of these is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. R b2 and R b3 If is not a fluorine-containing substituent, then each is independently hydrogen, a C1-C20 alkyl group, a C3-C30 cycloalkyl group, a C4-C30 heterocycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or a substituent in which one or more of the -CH2- of the substituent are replaced with -O-, -S-, or -NH-. R b4 If it is not a fluorine-containing substituent, it is either an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which one or more of the -CH2- groups of the substituent are replaced with -O-, -S-, or -NH- groups.

[0116] In the chemical formula 4b, L b1 This consists of a part containing a carbonyl group (moiety) and R b4 The part containing is concatenated. Therefore, the sum of nb and mb is 2 to 6, L b1 This is the same as the number of connections.

[0117] As an example, in the above chemical formula 4b, L b1 L may be a single bond. In the above chemical formula 4b, b1 If it is a single bond, then nb and mb are both 1, and Z b2 It may also be a single bond. In this case, the fluorine-based compound represented by chemical formula 4b may also be represented by the following chemical formula 4b-1.

[0118] [ka]

[0119] In the aforementioned chemical formula 4b-1, Z b1’ , R b1’ , R b2’ , R b3’ and R b4’ These are the Z of chemical formula 4b mentioned above. b1 , R b1 , R b2 , R b3 and R b4 It is identical to the above Z b1’ , R b1’ , R b2’ , R b3’ and R b4’ In this specification, Z of chemical formula 4b b1 , R b1 , R b2 , R b3 and R b4 The substituents described as specific examples may also be substituents.

[0120] As another example, in the above chemical formula 4b, L b1 The hydroxyl group of the polyol having 2 to 6 alcohol groups is Z b1 and Z b2 The hydroxyl group may be removed from the polyol by substitution, resulting in a divalent to hexavalent organic group.

[0121] In the chemical formula 4b, the L b1 This may be, for example, a divalent organic group obtained by removing a hydroxyl group from a diol such as ethanediol, propanediol, or butanediol; a trivalent organic group obtained by removing a hydroxyl group from a triol such as glycerol or trimethylolpropane; a tetravalent organic group obtained by removing a hydroxyl group from a tetraol such as pentaerythritol or ditrimethylolpropane; a pentavalent organic group obtained by removing a hydroxyl group from a pentaol such as 6-methylheptanepentaol; or a hexavalent organic group obtained by removing a hydroxyl group from a hexaol such as dipentaerythritol.

[0122] In the chemical formula 4b, Lb1 If it is a single bond or a divalent organic group, then nb and mb are each 1. b1 If the organic group is 3- to 6-valent, then nb may be greater than mb. For example, nb may be an integer between 1 and 3, and mb may be an integer of 1.

[0123] As an example, L b1 is a trivalent organic group obtained by removing a hydroxyl group from glycerol, which is a triol. Furthermore, nb may be 2 and mb may be 1. In this case, the fluorine-based compound represented by chemical formula 4b may also be represented by the following chemical formula 4b-2.

[0124] [ka]

[0125] In the aforementioned chemical formula 4b-2, Z b1” , Z b2” , R b1” , R b2” , R b3” and R b4” These are the Z of chemical formula 4b mentioned above. b1 , Z b2 , R b1 , R b2 , R b3 and R b4 It is identical to the above Z b1” , Z b2” , R b1” , R b2” , R b3” and R b4” In this specification, Z of chemical formula 4b b1 , Z b2 , R b1 , R b2 , R b3 and R b4 The substituents described as specific examples may also be substituents.

[0126] In the above chemical formula 4b, R b2 ~R b4At least one of the is a fluorine-containing substituent. The fluorine-containing substituent may be a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. Specifically, the fluorine-containing substituent may be a C1-C20 linear alkyl group substituted with two or more fluorines. More specifically, the fluorine-containing substituent may be -(CH2) a (CF2) b CHF2 or -(CH2) a (CF2) b CF3 may also be used. Here, a is an integer between 0 and 3, an integer between 0 and 2, or an integer of 1, and b may be an integer between 0 and 19, an integer between 0 and 15, an integer between 0 and 12, an integer between 0 and 11, an integer between 0 and 10, or an integer between 0 and 9.

[0127] In the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3 Each of these substituents may independently be hydrogen, a C1-C20 alkyl group, a C3-C30 cycloalkyl group, a C4-C30 heterocycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or a substituent in which one or more of the -CH2- groups of the substituent are replaced with -O-, -S-, or -NH-.

[0128] Specifically, in the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3 Each of these independently consists of hydrogen, a linear alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, or -(R 5 -O) p -R 6 It may be so. The above-(R 5 -O)p -R 6 In R 5 R is an alkylene group having 1 to 6 carbon atoms. 6 p is an alkyl group having 1 to 6 carbon atoms, and p may be an integer from 1 to 12.

[0129] More specifically, in the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3 Each of these is independently a hydrogen, methyl group, ethyl group, propyl group, butyl group, cyclohexyl group, tetrahydropyranyl group, phenyl group, or -(R 5 -O) p -R 6 This may also be the case. Here, the R 5 R may be a methylene group, an ethylene group, an n-propylene group, or an n-butylene group, and in particular may be a methylene group or an ethylene group. 6 p may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and in particular may be a methyl group. For example, p may be an integer from 1 to 12, an integer from 1 to 10, an integer from 1 to 8, an integer from 1 to 6, an integer from 1 to 5, an integer from 1 to 4, or an integer from 1 to 3.

[0130] In the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4 This substituent is either an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which one or more of the -CH2- groups of the substituent are replaced with -O-, -S-, or -NH- groups.

[0131] Specifically, in the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4This is a linear alkyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, or -(R 5 -O) p -R 6 It may be so. The above-(R 5 -O) p -R 6 In R 5 R is an alkylene group having 1 to 6 carbon atoms. 6 p is an alkyl group having 1 to 6 carbon atoms, and p may be an integer from 1 to 12.

[0132] More specifically, in the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4 is, -(R 5 -O) p -R 6 This may also be the case. Here, the R 5 R may be a methylene group, an ethylene group, an n-propylene group, or an n-butylene group, and in particular may be a methylene group or an ethylene group. 6 p may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and in particular may be a methyl group. For example, p may be an integer from 1 to 12, an integer from 1 to 10, an integer from 1 to 8, an integer from 1 to 6, an integer from 1 to 5, an integer from 1 to 4, or an integer from 1 to 3.

[0133] On the other hand, as yet another example, the holographic recording medium according to the above embodiment may include, as the branched fluorine-based compound, a compound represented by the following chemical formula 4c.

[0134] [ka]

[0135] In the aforementioned chemical formula 4c, Z c1 and Z c2 Each of these is independently -O-, -S-, or -NH-, R c1 ~R c4At least one of these is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. R c1 ~R c4 If is not a fluorine-containing substituent, each is independently a C1-C20 alkyl group, a C3-C30 cycloalkyl group, a C4-C30 heterocycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or a substituent in which one or more of the -CH2- groups of the substituent are replaced with -O-, -S-, or -NH-.

[0136] In the aforementioned chemical formula 4c, R c1 ~R c4 At least one of these is a fluorine-containing substituent. For example, R c1 This may be a fluorine-containing substituent.

[0137] The fluorine-containing substituent may be a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or an aryl group substituted with two or more fluorines.

[0138] Specifically, the fluorine-containing substituent may be a linear alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 12 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 14 carbon atoms substituted with two or more fluorines.

[0139] More specifically, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) bCF3 may be a decafluorocyclohexyl group or a pentafluorophenyl group. Here, a is an integer from 0 to 3, an integer from 0 to 2, or an integer from 0 to 1, and b may be an integer from 0 to 19, an integer from 0 to 15, an integer from 0 to 14, an integer from 0 to 13, an integer from 0 to 12, or an integer from 0 to 11.

[0140] As an example, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) b In the case of CF3 or decafluorocyclohexyl groups, it is possible to provide holographic recording media with low haze while contributing to large refractive index modulation.

[0141] In the aforementioned chemical formula 4c, R c1 ~R c4 If R is not a fluorine-containing substituent, c1 ~R c4 Each of these can independently be an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which one or more of the -CH2- groups of the substituent are replaced with -O-, -S-, or -NH- groups.

[0142] Specifically, in the above chemical formula 4c, R c1 ~R c4 If R is not a fluorine-containing substituent, c1 ~R c4 Each of these can independently be a linear alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heteroaryl group having 4 to 12 carbon atoms, an arylalkyl group having 7 to 16 carbon atoms, or -(R 5 -Y 1 ) c -R 6 It may be so. The above-(R 5 -Y 1 )c -R 6 In R 5 R is an alkylene group having 1 to 6 carbon atoms. 6 This is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, Y 1 is -O- or -S-, c may be an integer from 1 to 12, and when c is 2 or greater, R 5 These may be identical or different from one another.

[0143] More specifically, in the above chemical formula 4c, R c1 ~R c4 If R is not a fluorine-containing substituent, c1 ~R c4 Each of these is independently: ethyl group, propyl group, butyl group, pentyl group, hexyl group, phenyl group, benzyl group, pyridinyl group, pyrimidinyl group, methoxymethyl group, methoxyethyl group, methyl mercaptoethyl group, methylaminoethyl group, -(CH2CH2O) d1 CH3, -CH2O (CH2CH2O) d2 CH3 may be a cyclohexyloxyethyl group, a cyclohexyl mercaptoethyl group, or a phenyloxyethyl group. Here, d1 is an integer from 1 to 5, and d2 is an integer from 1 to 4.

[0144] The holographic recording medium according to the above embodiment may include at least one or more combinations selected from the fluorine compounds represented by the chemical formulas 4a to 4c as the branched fluorine compound.

[0145] 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 fluorine-based 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 the 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 range is satisfied, it is possible to show a large refractive index modulation value after recording by a fluorine-based compound with a sufficiently low refractive index, without problems such as poor compatibility with the components contained in the photopolymer composition, causing some of the fluorine-based compound to dissolve onto the surface of the photopolymer layer or poor haze, which is advantageous in ensuring excellent optical recording characteristics.

[0146] The photopolymer layer comprises a predetermined polymer matrix, a photoreactive monomer, and a fluorine-based compound, thereby ensuring superior high-temperature reliability.

[0147] As an example, the photopolymer layer may contain 25-40% by weight of the polymer matrix, 25-45% by weight of the photoreactive monomers, and 25-50% by weight of the fluorine-based compound, relative to the total weight of the polymer matrix, photoreactive monomers, and fluorine-based compound.

[0148] More specifically, the polymer matrix may be present in, for example, 25% or more by weight and 40% or less by weight, 35% or less by weight, or 33% or less by weight. The photoreactive monomer may be present in, for example, 25% or more by weight, 30% or more by weight, or 33% or more by weight and 45% or less by weight, 43% or less by weight, or 41% or less by weight. The fluorine-based compound may be present in, for example, 25% or more by weight, 30% or more by weight, or 33% or more by weight and 50% or less by weight, 45% or less by weight, 40% or less by weight, or 38% or less by weight. Within such ranges, migration of the fluorine-based compound to the surface at high temperatures can be effectively prevented, making it easier to ensure high-temperature reliability and high-temperature transparency.

[0149] The aforementioned photopolymer layer may additionally contain additives such as defoaming agents.

[0150] The photopolymer layer may contain a silicone-based reactive additive as an antifoaming agent. For example, a commercially available silicone-based reactive additive such as Tego Rad 2500 can be used.

[0151] The content of the aforementioned additive, for example, the defoaming agent, can be appropriately adjusted to a level that does not interfere with the function of the holographic recording medium.

[0152] The aforementioned photopolymer layer may be formed from a photopolymer composition containing a solvent.

[0153] The solvent may be an organic solvent, or, as an example, one or more organic solvents selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited to these. Specific examples of such organic solvents include ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; and one or more ethers selected from the group consisting of tetrahydrofuran or propylene glycol monomethyl ether.

[0154] The organic solvent may be added at the time when each component of the photopolymer composition is mixed, or it may be added to the photopolymer composition while each component is dispersed or mixed in the organic solvent.

[0155] The photopolymer composition may contain a solvent such that the solid content concentration is 1 to 90% by weight. Specifically, the photopolymer composition may contain a solvent such that the solid content concentration is 20% or more by weight, 30% or more by weight, 50% or more by weight, or 60% or more by weight, and 85% or less by weight, 80% or less by weight, 75% or less by weight, or 70% or less by weight. Within this range, the photopolymer composition can exhibit appropriate flowability, form a coating film without defects such as stripes, and form a photopolymer layer that exhibits desired physical properties and surface characteristics without defects occurring during the drying and curing process.

[0156] The holographic recording medium of the above 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 known in the relevant art can be used. For example, substrates such as glass, PET (polyethylene terephthalate), TAC (triacetyl cellulose), PC (polycarbonate), and COP (cycloolefin polymer) can be used.

[0157] The holographic recording medium of the above embodiment can exhibit a large refractive index modulation value and high diffraction efficiency despite its thin thickness.

[0158] 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.

[0159] The hologram recording medium of the above embodiment is not limited thereto, but may be one on which a reflective hologram or a transmissive hologram is recorded.

[0160] The holographic recording medium may have a notch filter structure, relating to the structure of the diffraction grating. The notch filter structure of the holographic recording medium in one embodiment means, for example, that the diffraction grating is not inclined with respect to the substrate surface (non-slanted) (substantially 0°), such that the diffraction grating is 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 repeating layers may each have the same or different predetermined thicknesses. Such non-slanted diffraction grating recordings can be manufactured in a manner that makes the incident angles of the incident object light and the reference light the same with respect to the normal. In a non-slanted structure, the degree of deformation (e.g., shrinkage or expansion) under high temperature and high humidity conditions is more clearly observed than in a slanted structure, and it is less affected by the shrinkage and expansion of the substrate.

[0161] The holographic recording medium of the above embodiment can have a high diffraction efficiency. For example, when a notch filter hologram is recorded on the holographic recording medium, it can have a diffraction efficiency of 70% or more. In this case, the thickness of the photopolymer layer may be, for example, 5 to 30 μm. Specifically, when a notch filter hologram is recorded, the diffraction efficiency may be 71% or more, 72% or more, 73% or more, 74% or more, 75% or more, 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90% or more. Thus, the holographic recording medium of the above embodiment can achieve excellent diffraction efficiency even when it includes a thin photopolymer layer. The diffraction efficiency can be measured by the method described in Test Example 2 below.

[0162] The holographic recording medium of the above embodiment can achieve refractive index modulation values ​​(Δn) of 0.020 or higher, 0.025 or higher, 0.026 or higher, 0.027 or higher, 0.028 or higher, 0.029 or higher, 0.030 or higher, 0.031 or higher, 0.032 or higher, 0.033 or higher, 0.034 or higher, or 0.035 or higher, even if the thickness of 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 for example, it may be 0.060 or lower. The refractive index modulation value can be measured by the method described in Test Example 2 below.

[0163] The holographic recording medium of the above embodiment is expected to provide a variety of optical elements that can be used even in environments where a lot of heat is generated, by exhibiting not only excellent optical recording characteristics and excellent durability in high-temperature environments, but also highly transparent optical characteristics.

[0164] The applications of the holographic recording medium of the above embodiment are not particularly limited. As an example of non-limiting applications, the holographic recording medium can be used in applications that are likely to be exposed to high-temperature environments, specifically in smart devices such as mobile devices, components of wearable displays, or automotive parts (e.g., head-up displays). The holographic recording medium of the above embodiment has excellent high-temperature reliability and can exhibit the intended optical recording characteristics even at high temperatures.

[0165] On the other hand, the hologram recording medium of the above embodiment can be manufactured in a form in which optical information is recorded by the step of applying a photopolymer composition to form a photopolymer layer, and irradiating a predetermined area of ​​the photopolymer layer manufactured in this way before recording with a coherent laser to selectively polymerize the photoreactive monomers contained in the photopolymer layer and record optical information.

[0166] In the step of forming the photopolymer layer, a photopolymer composition containing the above-described configuration can first be manufactured. When manufacturing the photopolymer composition, any commonly known mixer, stirrer, or similar device can be used for mixing the components without any limitations. Such a mixing process may be carried out at temperatures in the range of 0°C to 100°C, 10°C to 80°C, or 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 film made from the photopolymer composition. The coating film can be dried naturally at room temperature or at a temperature in the range of 30 to 80°C. This process can induce a hydrosilylation reaction between the hydroxyl group of the unreacted acrylic polyol and the silane functional group of the siloxane polymer.

[0168] The photopolymer layer produced in the step of forming the aforementioned photopolymer layer may have a fluorine-based compound, a photoreactive monomer and a photoinitiator system, and additives added as needed uniformly dispersed within the crosslinked polymer matrix.

[0169] Subsequently, when the photopolymer layer is irradiated with a coherent laser during the stage of recording the optical information, polymerization of photoreactive monomers occurs in regions where reinforcement interference occurs, forming a photopolymer. In regions where cancellation interference occurs, polymerization of photoreactive monomers does not occur or is suppressed, resulting in the presence of photoreactive monomers. The unreacted photoreactive monomers then diffuse towards the photopolymer side where the concentration of photoreactive monomers is lower, causing refractive index modulation, which generates a diffraction grating. As a result, a hologram, or optical information, is recorded on the photopolymer layer having the diffraction grating.

[0170] The hologram recording medium of the above embodiment can be provided in a state in which the reaction of the photoreactive monomer is terminated and the color of the photosensitive dye is removed by a step of photobleaching, which is performed after the step of recording the optical information, by irradiating the entire photopolymer layer on which the optical information is recorded with light.

[0171] For example, in the photobleaching step, ultraviolet light (UVA) in the 320-400 nm range is irradiated to terminate the reaction of the photoreactive monomer and remove the color of the photosensitive dye.

[0172] On the other hand, according to another embodiment of the invention, an optical element including the holographic recording medium is provided.

[0173] Specific examples of the optical elements include smart devices such as mobile devices, components for 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, projection screens and / or masks, media and light diffusion plates for optical memory systems, optical wavelength dividers, reflective and transmissive color filters, and the like.

[0174] An example of an optical element including the hologram recording medium is a hologram display device. The hologram display device includes a light source, an input unit, an optical system, and a display unit.

[0175] Specifically, the light source unit is the part that emits a laser beam used to provide, record, and reproduce three-dimensional image information of an object in the input unit and the display unit.

[0176] The aforementioned input unit is the part that pre-inputs three-dimensional image information of an object to be recorded on the display unit. Specifically, it is the part that can input three-dimensional information of an object, such as the intensity and phase of light in different spaces, to an electrically driven liquid crystal (SLM), and at this time, the input beam can be used.

[0177] The optical system may be composed of a mirror, a polarizer, a beam splitter, a beam shutter, a lens, etc. The optical system can distribute a laser beam emitted from the light source unit to an input beam sent to the input unit, a recording beam sent to the display unit, a reference beam, an erasing beam, a readout beam, etc.

[0178] The display unit can receive three-dimensional video information of an object from the input unit, record it on a hologram plate composed of an optically addressed SLM (optically addressed SLM), and reproduce the three-dimensional video of the object. At this time, the three-dimensional video information of the object can be recorded by the interference between the input beam and the reference beam. The three-dimensional video information of the object recorded on the hologram plate can be reproduced as a three-dimensional video by the diffraction pattern generated by the readout beam, and the erasing beam can be used to quickly remove the formed diffraction pattern. On the other hand, the hologram plate can move between the position where the three-dimensional video is input and the position where it is reproduced.

Advantages of the Invention

[0179] The hologram recording medium according to an embodiment of the invention not only has excellent optical recording characteristics but also can exhibit excellent reliability and transparency even in a high-temperature environment.

Brief Description of the Drawings

[0180] [Figure 1] It schematically shows the setup of a recording device for hologram recording. Specifically, FIG. 1 schematically shows the process in which a laser of a predetermined wavelength is irradiated from a light source 10, and then passes through mirrors (mirror) 20, 20', an iris (Iris) 30, a spatial filter (spatial filter) 40, an iris (Iris) 30', a collimation lens (collimation lens) 50, and a splitter (PBS, Polarized Beam Splitter) 60 and is irradiated onto a PP (hologram recording medium) 80 located on one side of a mirror 70. [Modes for carrying out the invention]

[0181] The function and effects of the invention will be explained in more detail below through specific embodiments of the invention. However, these are presented as examples of the invention and do not limit the scope of the invention's rights in any way.

[0182] In the following manufacturing examples, examples, and comparative examples, the content of raw materials, etc., refers to the content based on solid content unless otherwise specified.

[0183] Manufacturing Example 1: Production of Acrylic Polyols In a 2L jacketed reactor, 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate were added and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60-70°C, and the mixture was stirred for 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added, and the mixture was stirred for another 30 minutes. Subsequently, 0.24g of the polymerization initiator AIBN was added, and polymerization was carried out at the reaction temperature for 4 hours or more until the residual acrylate content was less than 1%, thereby producing an acrylate copolymer (weight-average molecular weight approximately 300,000, OH equivalent approximately 1802g / equivalent) in which the hydroxyl groups were located in the branched chains.

[0184] Example 1: Manufacture of photopolymer composition and holographic recording medium (1) Production of photopolymer compositions 0.57 g of poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number average molecular weight: approximately 590, Si-H equivalent: approximately 103 g / equivalent) as a siloxane polymer and 33.4 g of acrylic polyol with a solid content of 30% by weight, produced in Production Example 1 (solid content: 10.02 g), were mixed first (SiH / OH molar ratio = 1.0).

[0185] Then, 11.5 g of HR6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.08 g of the photosensitive dye H-Nu640 (Spectra), 0.3 g of the co-initiator Borate V, 11.5 g of a fluorine-based compound represented by the following chemical formula a as a plasticizer, and 26 g of the solvent methyl isobutyl ketone (MIBK) were added, and the mixture was stirred in a paste mixer for about 30 minutes while blocking out light. Subsequently, a Karstedt (Pt-based) catalyst was added to crosslink the matrix and produce a photopolymer composition.

[0186] [ka]

[0187] (2) Manufacturing of holographic recording media The aforementioned photopolymer composition was coated to a predetermined thickness onto a 60 μm thick TAC substrate using a Mayer bar, and dried at 80°C for 10 minutes. After drying, the thickness of the photopolymer layer was approximately 10 μm.

[0188] Examples 2-7, Comparative Examples 1 and 2: Production of photopolymer compositions and holographic recording media A photopolymer composition and a holographic recording medium were manufactured in the same manner as in Example 1, except that the type of plasticizer was different as shown in Table 1 below.

[0189] [Table 1A] [Table 1B]

[0190] Test Example 1: Evaluation of the migration properties of holographic recording media The temperature-dependent migration property of the hologram recording medium before recording was evaluated. Specifically, in order to evaluate the migration property according to the temperature of the photopolymer layer, the refractive index from the surface to the center of the photopolymer layer according to the temperature was measured. The refractive index was measured using spectroscopic ellipsometry from Ellipso Technology at an incident angle of 70° and a wavelength range of 320 to 1680 nm.

[0191] The thickness (A1) of the anisotropic refractive index layer showing a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer and the thickness (A2) of the remaining part of the photopolymer layer were measured for each temperature and described in Table 2 below.

[0192] In addition, the percentage (Pn) of the thickness (A1) of the anisotropic refractive index layer with respect to the total thickness (A1 + A2) of the photopolymer layer according to the temperature of Equation 1 below was calculated and described in Table 2 below.

[0193] [Equation 1] Pn(%) = {A1 / (A1 + A2)} × 100

[0194] In Equation 1 above, Pn is the thickness ratio of the anisotropic refractive index layer formed at n°C, A1 is the thickness of the anisotropic refractive index layer formed at n°C. The anisotropic refractive layer means the surface portion of the photopolymer layer showing a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm, A2 is the thickness of the remaining part of the photopolymer layer excluding the anisotropic refractive index layer.

[0195]

Table 2

[0196] On the other hand, the degree of migration according to the temperature of the hologram recording medium before recording was evaluated. Specifically, the refractive indices at the center and surface of the photopolymer layer were measured for each temperature and wavelength and described in Table 3 below. The refractive index was measured using the apparatus described above.

[0197] [Table 3]

[0198] Referring to Tables 2 and 3 above, it can be seen that the photopolymer layers of Examples 1 and 4 exhibit extremely thin layers of different refractive indices, at a negligible level that does not affect the function of the holographic recording medium, and that the difference in absolute refractive index between the center and the surface is also very small.

[0199] In contrast, the photopolymer layer of Comparative Example 1 was found to have an extremely thick layer of different refractive indices, to the extent that it impaired the function of the holographic recording medium, and the difference in absolute refractive index between the center and the surface was also very large.

[0200] Test Example 2: Performance Evaluation of Holographic Recording Media (1) P80 (Ratio of different refractive index layers at 80°C, %) The high-temperature migration properties of the hologram recording medium before recording were evaluated. Specifically, to evaluate the migration properties 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. The refractive index was measured using Ellipso Technology's spectroscopic ellipsometry at an incident angle of 70° and a wavelength of 320–1680 nm.

[0201] Then, P80 (the thickness ratio of the different refractive index layers at 80°C) was calculated using Equation 1 below and is listed in Table 4 below.

[0202] [Formula 1] Pn(%) = {A1 / (A1+A2)} × 100

[0203] In the above formula 1, Pn is the thickness ratio of the different refractive index layers formed at n°C. A1 is the thickness of the differential refractive index layer formed at n°C, and the differential refractive index layer refers to the surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm. A2 is the thickness of the remaining portion of the photopolymer layer after removing the different refractive index layer.

[0204] (2) △H80 (Haze increase at 80℃, %p) A diffraction grating was recorded using the setup shown in Figure 1. Specifically, after laminating the manufactured photopolymer layer onto a mirror, irradiating it with a laser allows for the recording of a notch filter hologram with periodic refractive index modulation in the thickness direction due to the interference between the incident light (L) and the light reflected by the mirror (L'). In this example, a notch filter hologram was recorded with an incident angle of 0° (degree). A notch filter and a Bragg reflector are optical elements that reflect only light of a specific wavelength and have a structure in which two layers with different refractive indices are periodically stacked to a constant thickness.

[0205] The haze difference before and after high-temperature exposure of a holographic recording medium containing a diffraction grating was evaluated. Haze was measured using a HAZE METER (Murakami Color Research Laboratory, HM-150) in accordance with JIS K 7136. The measurement light was incident on the side surface of the substrate of the holographic recording medium.

[0206] Specifically, the holographic recording medium was left at 80°C for 100 hours, and the difference in haze before and after the period was calculated using Equation 2 below. The haze increase at 80°C (△H80) is then shown in Table 4 below.

[0207] [Formula 2] △Hn(%p)=B2-B1

[0208] In equation 2 above, △Hn is the haze rise of the hologram recording medium at n°C. B1 is the initial haze of the hologram recording medium before being left at n°C. B2 is the haze of the holographic recording medium after it has been left at n°C for 100 hours.

[0209] (3) Diffraction efficiency The diffraction efficiency (η) was determined for a holographic recording medium on which a diffraction grating was recorded, using the following equation 3.

[0210] [Formula 3] η(%)={P D / (P D +P T )} × 100

[0211] In the above equation 3, η is the diffraction efficiency, and P D This is the output power (mW / cm²) of the diffracted beam of the sample after recording. 2 ) and P T This is the output power (mW / cm²) of the beam transmitted through the sample after recording. 2 )

[0212] (4) Refractive index modulation value (△n) For a holographic recording medium on which a diffraction grating was recorded, the refractive index modulation value (△n) was determined using Equation 4 and Bragg's equation below.

[0213]

number

[0214] In the above formula, η is the reflectance diffraction efficiency (DE), d is the thickness of the photopolymer layer, λ is the wavelength of the incident light for recording (660 nm or 532 nm), θ is the angle of incidence of the incident light for recording, φ is the slant angle of the grating, △n is the refractive index modulation value, n is the refractive index of the photopolymer, and Λ represents the period of the diffraction grating. In the above examples and comparative examples, the hologram was recorded using a notch filter method, so θ (angle of incidence) and φ (slant angle of the grating) are all 0°.

[0215] [Table 4]

[0216] Referring to Table 4 above, it can be seen that the holographic recording media produced in Examples 1 to 7 exhibit high diffraction efficiency and refractive index modulation values, while also demonstrating excellent high-temperature stability, minimal formation of different refractive index layers, and very little increase in haze. In contrast, the holographic recording media produced in Comparative Examples 1 and 2 exhibit poor optical recording characteristics, particularly at high temperatures where thicker different refractive index layers are formed, and where haze increases significantly.

[0217] This confirms that the holographic recording medium according to one embodiment of the invention exhibits excellent optical recording characteristics, high-temperature stability, and high transparency by containing a branched fluorine-based compound.

Claims

1. A polymer matrix or precursor formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine-based compound. A holographic recording medium having a P80 content of 0.10% or less, which is Pn measured at 80°C according to the following formula 1: [Formula 1] Pn (%) = {A1 / (A1+A2)}×100 In the above formula 1, Pn is the thickness ratio of the different refractive index layers formed at n°C. A1 is the thickness of the differential refractive index layer formed at n°C, and the differential refractive index layer refers to the surface portion of the photopolymer layer that shows a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm. A2 is the thickness of the remaining portion of the photopolymer layer after removing the layers with different refractive indices.

2. The holographic recording medium according to claim 1 comprises a repeating unit represented by the following chemical formula 1 and an end group represented by the following chemical formula 2: 【Chemistry 1】 In the aforementioned chemical formula 1, Multiple R １１ and R １２ These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. k is an integer between 1 and 10,000. 【Chemistry 2】 In the aforementioned chemical formula 2, Multiple R １３ ~R １５ These are either identical or different from each other, and each is independently hydrogen, a 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 one of the terminal groups selected from the terminal groups represented by chemical formula 2, R １１ ~R １５ At least one of them is hydrogen.

3. The holographic recording medium according to claim 1, wherein the acrylic polyol is a polymer having a structure in which a hydroxyl group is bonded to the main chain or side chain of an acrylate polymer.

4. The aforementioned photoreactive monomers are benzyl (meth)acrylate, benzyl 2-phenyl acrylate, 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 A 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, bisphenol orange (meth)acrylate, modified bisphenol orange (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.

5. The holographic recording medium according to claim 1, wherein the photoinitiator system comprises a photosensitive dye and a coinitiator.

6. The holographic recording medium according to claim 5 comprises a borate anion represented by the following chemical formula 3 as the co-initiator: [Chemical formula 3] BX １ X ２ X ３ X ４ In the above chemical formula 3, X １ ~X ４ Each of these is independently a substituted or unsubstituted C1-C20 alkyl group, a C2-C20 alkenyl group, a C6-C30 aryl group, a C7-C30 arylalkyl group, a C7-C30 alkylaryl group, or an allyl group, and X １ ~X ４ At least one of them is not an aryl group.

7. The holographic recording medium according to claim 1, wherein the fluorine-based compound includes a branched fluorine-based compound.

8. The hologram recording medium according to claim 7 comprises at least one selected from among the fluorine compounds represented by the following chemical formulas 4a to 4c: 【Transformation 3】 In the aforementioned chemical formula 4a, Z ａ１ is -O- or -NH-, Z ａ２ These are single bonds, -O- or -NH-, L ａ１ This is a divalent to hexavalent organic group obtained by removing a hydroxyl group from a polyol that is either a single bond or has 2 to 6 alcohol groups. na and ma are independent integers between 1 and 5, and the sum of na and ma is between 2 and 6. R ａ１ , R ａ２ and R ａ３ These are independently either a methyl group or an ethyl group, R ａ４ This is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. 【Chemistry 4】 In the aforementioned chemical formula 4b, Z ｂ１ is -O- or -NH-, Z ｂ２ These are single bonds, -O- or -NH-, L ｂ１ This is a divalent to hexavalent organic group obtained by removing a hydroxyl group from a polyol that is either a single bond or has 2 to 6 alcohol groups. nb and mb are each independent integers between 1 and 5, and the sum of nb and mb is between 2 and 6. R ｂ１ This is a methyl group or an ethyl group, R ｂ２ ~R ｂ４ At least one of these is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. R ｂ２ and R ｂ３ If is not a fluorine-containing substituent, then each is independently hydrogen, a C1-C20 alkyl group, a C3-C30 cycloalkyl group, a C4-C30 heterocycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or one or more of the substituents -CH ２ The substituent is substituted with -O-, -S-, or -NH-. R ｂ４ If it is not a fluorine-containing substituent, it is a C2-C20 alkyl group, a C3-C30 cycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or one or more of the substituents -CH ２ The substituent is substituted with -O-, -S-, or -NH-. 【Transformation 5】 In the aforementioned chemical formula 4c, Z ｃ１ and Z ｃ２ These are independently -O-, -S-, or -NH-, R ｃ１ ~R ｃ４ At least one of these is a fluorine-containing substituent, which is a C1-C20 alkyl group substituted with two or more fluorines, a C3-C30 cycloalkyl group substituted with two or more fluorines, or a C6-C30 aryl group substituted with two or more fluorines. R ｃ１ ~R ｃ４ If is not a fluorine-containing substituent, each is independently a C1-C20 alkyl group, a C3-C30 cycloalkyl group, a C4-C30 heterocycloalkyl group, a C7-C40 cycloalkylalkyl group, a C6-C30 aryl group, a C4-C30 heteroaryl group, or a C7-C40 arylalkyl group, or one or more of the substituents -CH ２ The - is a substituent substituted with -O-, -S-, or -NH-.

9. The hologram recording medium according to claim 1, wherein the fluorine-based compound is contained in an amount of 20 to 200 parts by weight per 100 parts by weight of the polymer matrix.

10. The hologram recording medium according to claim 1, wherein the diffraction efficiency is 70% or more when a notch filter hologram is recorded.

11. The hologram recording medium according to claim 1, wherein the thickness of the photopolymer layer is 5 to 30 μm and the refractive index modulation value is 0.020 or more.

12. The holographic recording medium according to claim 1, wherein at 80°C, the difference in refractive index between the center of the photopolymer layer and the surface with a thickness of 0.05% or less is 0.080 or less.

13. The hologram recording medium according to claim 1, wherein ΔH80, which is ΔHn measured at 80°C by the following formula 2, is 10%p or less: [Formula 2] △Hn(%p)=B2-B1 In the above equation 2, △Hn is the haze rise of the hologram recording medium at n°C. B1 is the initial haze of the hologram recording medium before being left at n°C. B2 is the haze of the holographic recording medium after it has been left at n°C for 100 hours.

14. An optical element comprising a holographic recording medium as described in claim 1.

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