Holographic recording medium and optical element including same

Abstract

The present invention relates to a holographic recording medium and an optical element including the same. The holographic recording medium not only has excellent optical recording properties, but also exhibits transparent optical properties and excellent reliability even in high temperature and high humidity environments.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0146043 dated November 4, 2022 and Korean Patent Application No. 10-2022-0146044 dated November 4, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

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

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

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

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

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

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

[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 placed in high-temperature / high-humidity environments. In these cases, the diffraction gratings can deform, distorting the image and preventing the intended function from being achieved. Therefore, there is a need to develop a highly reliable photopolymer layer and a holographic recording medium containing the same that exhibit minimal diffraction grating deformation despite the heat and moisture of the usage environment. Summary of the Invention [Problem to be solved by the invention]

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

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

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

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

[0013] In this specification, with respect to the environmental conditions in which a holographic recording medium or an element including the same is placed, the term "high temperature" can refer to a temperature of 60°C or higher. For example, high temperature can refer to a temperature of 65°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, 85°C or higher, or 90°C or higher. The upper limit of high temperature is not particularly limited, and may be, for example, 110°C or lower, 105°C or lower, 100°C or lower, 95°C or lower, 90°C or lower, 85°C or lower, or 80°C or lower. When temperature affects the characteristics of a substance, article, or each component, unless temperature is specifically mentioned, the temperature condition under which the characteristics are measured or described can refer to room temperature (e.g., a temperature in the range of about 15 to 30°C, where no particular cooling or heating is performed).

[0014] Furthermore, in this specification, "high humidity" in relation to the environmental conditions in which a holographic recording medium or an element including the same is placed can refer to a relative humidity of 80% or higher. For example, a high humidity condition can refer to a condition satisfying a relative humidity of 85% or higher, 90% or higher, or 95% or higher. When humidity affects the characteristics of a substance, article, or each component, unless otherwise specified, the humidity condition under which the characteristics are measured or described can be a condition with a relative humidity lower than that of a high humidity condition, for example, a relative humidity condition in the range of 15% or higher to less than 80%. Specifically, the humidity condition can refer to a relative humidity condition with a lower limit of 20% or higher, 25% or higher, 30% or higher, 35% or higher, or 40% or higher and an upper limit of 75% or lower, 70% or lower, 65% or lower, or 60% or lower.

[0015] In addition, in this specification, high temperature / high humidity conditions may refer to environmental conditions that satisfy one or more of the high temperature conditions and high humidity conditions described above.

[0016] According to one embodiment of the present invention, there is provided a holographic recording medium comprising: a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine-based compound, wherein the refractive index variation calculated by the following Equation 4 is 1.0% or less and the haze is 2% or less.

[0017] Refractive index change (%) = {|1-n1 / n0|} × 100 (Equation 4) In Equation 4, n0 is the refractive index of a sample obtained by storing an unrecorded holographic recording medium at a temperature of 20-25°C and a relative humidity of 40-50% and then bleaching it with a white LED (light-emitting diode), and n1 is the refractive index of a sample obtained by storing an unrecorded holographic recording medium at a temperature of 60°C and a relative humidity of 90% for 72 hours and then bleaching it with a white LED.

[0018] The present inventors have confirmed that when a specific photopolymer layer is included, it is possible to provide a holographic recording medium that exhibits improved optical recording properties while also exhibiting optical properties that are highly reliable and highly transparent even in high temperature / high humidity environments, and have thereby completed the present invention.

[0019] A holographic recording medium and an optical element including the holographic recording medium according to an embodiment of the present invention will be described in detail below.

[0020] A holographic recording medium according to one embodiment of the present invention includes a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine-based compound.

[0021] The photopolymer layer may be a pre-recorded photopolymer layer in which optical information can be recorded, or may be a photopolymer layer in which optical information has been recorded.

[0022] A photopolymer layer with optical information recorded on it can be fabricated by irradiating an object beam and a reference beam onto an unrecorded photopolymer layer. When the object beam and reference beam are irradiated onto an unrecorded photopolymer layer, the photoinitiator system remains in an inactive state in the destructive interference region due to the interference length between the object beam and the reference beam, preventing photopolymerization of the photoreactive monomer. However, the activated photoinitiator system in the constructive interference region photopolymerizes the photoreactive monomer. As the photoreactive monomer is continuously consumed in the constructive interference region, a concentration difference occurs between the destructive and constructive interference regions. As a result, the photoreactive monomer in the destructive interference region diffuses to the constructive interference region. At this time, the fluorine-based plasticizer migrates in the opposite direction to the photoreactive monomer. Because the photoreactive monomer and the photopolymer formed from it have a higher refractive index than the polymer matrix and the fluorine-based compound, spatial refractive index variations occur in the photopolymer layer. This spatial refractive index modulation in the photopolymer layer creates a grating. Such a grating surface acts as a reflective surface that reflects incident light due to the difference in refractive index. After hologram recording, when light of the recording wavelength is incident in the direction of the reference light, the Bragg condition is satisfied and the light is diffracted in the direction of the original object light, thereby reproducing the hologram optical information.

[0023] Therefore, when the photopolymer layer is in a pre-recorded state, the photopolymer layer may contain a photoreactive monomer, a photoinitiator system, and a fluorine-based compound randomly dispersed within a 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 so as to form a lattice with the polymer matrix.

[0025] The photopolymer layer is formed from a photopolymer composition containing a polymer matrix or its precursor formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)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-based polymer containing silane functional groups (Si—H) with a (meth)acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking a (meth)acrylic polyol with a siloxane-based polymer containing silane functional groups. More specifically, the hydroxyl groups of the (meth)acrylic polyol can form crosslinks with the silane functional groups of the siloxane-based polymer through a hydrosilylation reaction. The hydrosilylation reaction can be rapidly carried out in the presence of a Pt-based catalyst even at room temperature (e.g., a temperature in the range of about 15 to 30°C without heating or cooling). Therefore, by employing a polymer matrix as a support that can be rapidly crosslinked even at room temperature, the holographic recording medium of one embodiment can improve manufacturing efficiency and productivity.

[0027] The polymer matrix can enhance the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer through the flexible backbone of the siloxane polymer. In addition, the siloxane bond, which has excellent heat resistance and humidity resistance, can easily ensure the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium containing the same.

[0028] The polymer matrix may have a relatively low refractive index, thereby 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, the "refractive index" may be a value measured using an Abbe refractometer at 25°C.

[0029] The photopolymer layer may include the above-described crosslinked polymer matrix or a precursor thereof. When the photopolymer layer includes a precursor of the polymer matrix, it may include a siloxane-based polymer, a (meth)acrylic polyol, and a Pt-based catalyst.

[0030] The siloxane-based polymer may, for example, include a repeating unit represented by the following Chemical Formula 1 and a terminal group represented by the following Chemical Formula 2: [ka]

[0031] In chemical formula 1, Multiple R 11 and R 12 are the same or different and each independently represent hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms; k is an integer from 1 to 10,000; [ka] In chemical formula 2, Multiple R 13 ~R 15 are the same or different and each independently represent hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms; R of at least one repeating unit among the repeating units represented by Chemical Formula 1 and any one terminal group among the terminal groups represented by Chemical Formula 2 11 ~R 15 At least one of is hydrogen.

[0032] In Chemical Formula 2, -(O)- means that when Si of the terminal group represented by Chemical Formula 2 is bonded to the repeating unit represented by Chemical Formula 1, it is bonded via oxygen (O) or directly without oxygen (O).

[0033] As used herein, an "alkyl group" may be a straight-chain, branched-chain, or cyclic alkyl group. Non-limiting examples of "alkyl groups" include methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methylpentyl, etc.), methyl ether ... pentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), etc.

[0034] As an example, R in Chemical Formula 1 and Chemical Formula 2 11 ~R 15 is methyl or hydrogen, and multiple R 11 ~R 15 At least two of the R in Chemical Formula 1 may be hydrogen. 11 and R 12are methyl and hydrogen, respectively, and R in chemical formula 2 13 ~R 15 are each independently methyl or hydrogen (e.g., polymethylhydrosiloxanes terminated with trimethylsilyl or dimethylhydrosilyl groups); 11 and R 12 are methyl and hydrogen, respectively, and the remaining R 11 and R 12 are all methyl, and R in chemical formula 2 13 ~R 15 are each independently methyl or hydrogen (e.g., poly(dimethylsiloxane-co-methylhydrosiloxane) having terminal trimethylsilyl or dimethylhydrosilyl groups); or R 11 and R 12 are all methyl, and R in chemical formula 2 13 ~R 15 and the remaining groups are each independently methyl or hydrogen (for example, polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0035] The siloxane-based compound may have a number-average molecular weight (Mn) ranging from 200 to 4,000, for example. Specifically, the lower limit of the number-average molecular weight of the siloxane-based polymer may be, for example, 200 or more, 250 or more, 300 or more, or 350 or more, and the upper limit may be, for example, 3,500 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less. When the number-average molecular weight of the siloxane-based polymer satisfies the above range, problems such as a decrease in the degree of matrix crosslinking due to volatilization of the siloxane-based polymer during crosslinking with a (meth)acrylic polyol at room temperature or higher, or phase separation with other components of the photopolymer composition due to poor compatibility of the siloxane-based polymer with these components, can be prevented, thereby enabling holographic recording media formed from the photopolymer composition to exhibit excellent optical recording properties and excellent durability under high-temperature / high-humidity conditions.

[0036] The number average molecular weight refers to the number average molecular weight (unit: g / mol) measured in terms of polystyrene by gel permeation chromatography (GPC). The process of measuring the number average molecular weight in terms of polystyrene by GPC can use commonly known analytical equipment, detectors such as a refractive index detector, and analytical columns, and commonly used temperature conditions, solvents, and flow rates can be applied. Specific examples of measurement conditions include a temperature of 25°C, tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0037] The (meth)acrylic polyol can refer to a polymer in which one or more, specifically two or more, hydroxy groups are bonded to the main chain or side chain of a (meth)acrylate polymer. In this specification, unless otherwise specified, "(meth)acrylic (based)" refers to acrylic (based) and / or methacrylic (based), and is a term that encompasses all of acrylic (based), methacrylic (based), and a mixture of acrylic (based) and methacrylic (based).

[0038] The (meth)acrylic polyol may be a homopolymer of a (meth)acrylate monomer having a hydroxy group, a copolymer of two or more types of (meth)acrylate monomers having a hydroxy group, or a copolymer of a (meth)acrylate monomer having a hydroxy group and a (meth)acrylate monomer not having a hydroxy group. In this specification, the term "copolymer" encompasses random copolymers, block copolymers, and graft copolymers, unless otherwise specified.

[0039] Examples of (meth)acrylate monomers having a hydroxy group include hydroxyalkyl(meth)acrylates and hydroxyaryl(meth)acrylates, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms. Examples of (meth)acrylate monomers not having a hydroxy group include alkyl(meth)acrylate monomers and aryl(meth)acrylate monomers, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms.

[0040] The (meth)acrylic polyol may have a weight-average molecular weight (Mw) in the range of 150,000 to 1,000,000, for example. The weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene measured by the GPC method described above. For example, the lower limit of the weight-average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, 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 (meth)acrylic polyol satisfies the above range, the polymer matrix can fully function as a support, and the deterioration of the optical information recording properties is minimal even over time. The polymer matrix is ​​also provided with sufficient flexibility, and the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer composition is improved, thereby minimizing the deterioration of the optical information recording properties.

[0041] In order to adjust the crosslinking density of the (meth)acrylic polyol with the siloxane polymer to a level advantageous for ensuring the functionality of the holographic recording medium, the hydroxyl equivalent of the (meth)acrylic polyol can be adjusted to an appropriate level.

[0042] Specifically, the hydroxyl (—OH) equivalent of the (meth)acrylic polyol may be, for example, within a range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl (—OH) equivalent of the (meth)acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. The upper limit of the hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol may be 2900 g / equivalent or less, 2800 g / equivalent or less, 2700 g / equivalent or less, 2600 g / equivalent or less, 2500 g / equivalent or less, 2400 g / equivalent or less, 2300 g / equivalent or less, 2200 g / equivalent or less, 2100 g / equivalent or less, 2000 g / equivalent or less, or 1900 g / equivalent or less. The hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol is the equivalent weight (g / equivalent) per hydroxy functional group, and is calculated by dividing the weight-average molecular weight of the (meth)acrylic polyol by the number of hydroxy functional groups per molecule. The smaller the equivalent weight value, the higher the functional group density, and the larger the equivalent weight value, the lower the functional group density. When the hydroxyl group (-OH) equivalent of the (meth)acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslinking density and fully functions as a support, the fluidity of the components contained in the photopolymer layer is improved, and the boundary surface of the diffraction grating formed after recording does not collapse.The initial refractive index modulation value can be maintained at an excellent level even over time, and deterioration of the recording characteristics for optical information can be minimized.

[0043] The (meth)acrylic polyol may have a glass transition temperature (Tg) in the range of, for example, −60 to −10°C. Specifically, the lower limit of the glass transition temperature may be, for example, −55°C or higher, −50°C or higher, −45°C or higher, −40°C or higher, −35°C or higher, −30°C or higher, or −25°C or higher, and the upper limit may be, for example, −15°C or lower, −20°C or lower, −25°C or lower, −30°C or lower, or −35°C or lower. When the glass transition temperature falls within the above range, the glass transition temperature can be lowered without significantly reducing the modulus of the polymer matrix, thereby increasing the mobility (fluidity) of other components in the photopolymer 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).

[0044] The refractive index of the (meth)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 (meth)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 (meth)acrylic polyol has a refractive index within the above-mentioned range, it can contribute to increasing the refractive index modulation. The refractive index of the (meth)acrylic polyol is a theoretical refractive index and can be calculated using the refractive index of the monomers used in producing the (meth)acrylic polyol (measured at 25°C using an Abbe refractometer) and the fraction (molar ratio) of each monomer.

[0045] The (meth)acrylic polyol and siloxane polymer can be used so that the molar ratio (SiH / OH) of the silane functional groups (Si-H) of the siloxane polymer to the hydroxyl groups (-OH) of the (meth)acrylic polyol is 0.80 to 3.5. In other words, the type and content of the siloxane polymer and (meth)acrylic polyol can be selected so that the desired molar ratio is satisfied when forming the polymer matrix. The lower limit of the molar ratio (SiH / OH) can be, for example, 0.81 or more, 0.85 or more, 0.90 or more, 0.95 or more, 1.00 or more, or 1.05 or more, and the upper limit can be, for example, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.05 or less, or 3.0 or less. When the molar ratio (SiH / OH) satisfies the above range, the polymer matrix is ​​crosslinked at an appropriate crosslink density, improving reliability under high-temperature / high-humidity conditions and achieving sufficient refractive index modulation.

[0046] An example of the Pt-based catalyst may be Karstedt's catalyst, etc. The polymer matrix precursor may further include, in addition to the Pt-based catalyst, a rhodium-based, iridium-based, rhenium-based, molybdenum-based, iron-based, nickel-based, alkali metal or alkaline earth metal-based, Lewis acid-based, or carbene-based non-metal-based catalyst, if necessary.

[0047] Meanwhile, the photoreactive monomer may include a compound having a refractive index higher than that of the polymer matrix to achieve the above-described refractive index modulation. However, not all of the photoreactive monomers included in the photopolymer layer are limited to having a refractive index higher than that of the polymer matrix. At least some of the photoreactive monomers may have a refractive index higher than that of the polymer matrix to achieve a high refractive index modulation value. For example, the photoreactive monomer may include a monomer having a refractive index of 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or 1.60 or more and 1.70 or less.

[0048] 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.

[0049] Examples of the monofunctional monomer include benzyl (meth)acrylate (M1182 having a refractive index of 1.5140, Miwon), benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate (M1122 having a refractive index of 1.565, Miwon), phenol (ethylene oxide) (meth)acrylate (phenol (EO) (meth)acrylate; M140 having a refractive index of 1.516, Miwon), and phenol (ethylene oxide) 2 (meth)acrylate. (phenol (EO)2 (meth)acrylate; M142 having a refractive index of 1.510, Miwon), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol (EO) (meth)acrylate; M1142 having a refractive index of 1.577, Miwon), phenylthioethyl (meth)acrylate (M1162 having a refractive index of 1.560, Miwon), and biphenylmethyl (meth)acrylate may include one or more selected from the group consisting of phenylthioethyl (meth)acrylate (phenol (EO)2 (meth)acrylate; M142 having a refractive index of 1.510, Miwon), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol (EO) (meth)acrylate; M1142 having a refractive index of 1.577, Miwon), and biphenylmethyl (meth)acrylate.

[0050] The polyfunctional monomer is, for example, bisphenol A (ethylene oxide). 2~10 Di(meth)acrylate (bisphenol A (EO) 2~10 (Meth)acrylates; Miwon, M240 with a refractive index of 1.537, M241 with a refractive index of 1.529, M244 with a refractive index of 1.545, M245 with a refractive index of 1.537, M249 with a refractive index of 1.542, M2100 with a refractive index of 1.516, M2101 with a refractive index of 1.512), bisphenol A epoxy di(meth)acrylate (Miwon, PE210 with a refractive index of 1.557, PE2120A with a refractive index of 1.533, PE2120B with a refractive index of 1.534, PE2020C with a refractive index of 1.539, PE2120S with a refractive index of 1.556), bisfluorene di(meth)acrylate (Miwon, HR6022 with a refractive index of 1.600, HR6020 with a refractive index of 1.600) The epoxy resin may include one or more selected from the group consisting of modified bisphenol A fluorene di(meth)acrylate (Miwon, HR6040 having a refractive index of 1.600, HR6042 having a refractive index of 1.600), modified bisphenol A fluorene di(meth)acrylate (Miwon, HR6060 having a refractive index of 1.584, HR6100 having a refractive index of 1.562, HR6200 having a refractive index of 1.530), tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate (Miwon, M370 having a refractive index of 1.508), phenol novolac epoxy (meth)acrylate (Miwon, SC6300 having a refractive index of 1.525), and cresol novolac epoxy (meth)acrylate (Miwon, SC6400 having a refractive index of 1.522, SC6400C having a refractive index of 1.522).

[0051] The photopolymer layer may contain 50 to 300 parts by weight of the photoreactive monomer 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. Meeting the above ranges is advantageous in ensuring excellent optical recording properties and durability in high-temperature / high-humidity environments.

[0052] In this specification, the content of the polymer matrix refers to the combined content (by weight) of the (meth)acrylic polyol and siloxane polymer that form the matrix. In other words, the content of the polymer matrix refers to the content including both the polymer matrix formed by crosslinking the (meth)acrylic polyol and the siloxane polymer, and the partially uncrosslinked polymer matrix precursor.

[0053] The photopolymer layer includes a photoinitiator system, which can mean a photoinitiator or a combination of a photosensitizer and a coinitiator that allows polymerization to be initiated by light.

[0054] The photopolymer layer can include a photoreductant and a coinitiator as a photoinitiator system.

[0055] As the photosensitizer, for example, a photosensitive dye can be used. Specifically, examples of the photosensitive dye include silicon rhodamine compounds, sulfonium derivatives of ceramidonin, 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 dyes selected from the group consisting of fluorescein violet, brilliant green, Astrazon orange G, darrow red, pyronin Y, basic red 29, pyrrylium iodide, safranin O, cyanine, methylene blue, Azure A, and BODIPY may be used.

[0056] As an example, as the photosensitive dye, cyanine dyes such as Cy3 and Cy5 (H-Nu640, Spectra Group Limited) or Safranin O can be used.

[0057] The photopolymer layer can contain 0.01 to 10 parts by weight of the photosensitive dye relative to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the photosensitive dye can 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 can be, for example, 5 parts by weight or less. When the above range is satisfied, an appropriate polymerization reaction rate is exhibited, which is advantageous for ensuring the desired optical recording characteristics.

[0058] The coinitiator may be an electron donor, an electron acceptor, or a mixture thereof.

[0059] As an example, the photopolymer layer may include an electron donor as a coinitiator, such as a borate anion represented by Formula 3:

[0060] BX 1 X 2 X 3 X 4 (Chemical formula 3) In chemical formula 3, X 1 ~X 4 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group; X 1 ~X 4 At least one of is not an aryl group.

[0061] When the alkyl group having 1 to 20 carbon atoms, the alkenyl group having 2 to 20 carbon atoms, the aryl group having 6 to 30 carbon atoms, the arylalkyl group having 7 to 30 carbon atoms, the alkylaryl group having 7 to 30 carbon atoms or the allyl group is substituted, it may be substituted with one or more types selected from the group consisting of halogen and an alkoxy group having 1 to 5 carbon atoms.

[0062] Specifically, X 1 ~X 3 are each independently methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, cyclobutyl, cyclopentyl, cyclohexyl, ethenyl, propenyl, phenyl, methylphenyl, methoxyphenyl, naphthyl, methylnaphthyl, or methoxynaphthyl, substituted or unsubstituted by halogen; 4 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.

[0063] The cation bonded to the borate anion does not absorb light and may be an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation refers to an ammonium cation in which the nitrogen (N) is substituted with four substituents, and the four substituents may each independently be an alkyl group having 1 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 6 to 40 carbon atoms, or an alkyl group having 2 to 40 carbon atoms linked via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3).

[0064] As the electron donor, for example, commercially available butyryl choline triphenylbutylborate (Borate V, manufactured by Spectra Group) can be used.

[0065] As an example, the photopolymer layer can include an electron acceptor as a coinitiator. The electron acceptor can include, for example, an onium salt, such as a sulfonium salt, an iodonium salt, or a mixture thereof.

[0066] For example, the electron acceptor may include an iodonium salt, such as commercially available H-Nu254 (Spectra).

[0067] The photopolymer layer can contain 0.05 to 10 parts by weight of co-initiator per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the co-initiator content can 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 can be, for example, 5 parts by weight or less. When the above range is satisfied, an appropriate polymerization reaction rate is exhibited, which is advantageous for ensuring the desired optical recording characteristics.

[0068] The photoinitiator system can contain an additional photoinitiator to remove the color of the photosensitive dye and react all unreacted photoreactive monomers after irradiation for recording. Examples of photoinitiators that can be used include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, amine derivatives, diazonium salts, sulfonium salts, iodonium salts, sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η-benzene)(η-cyclopentadienyl)iron(II), benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosylphthalimide, and mixtures thereof.More specifically, examples of the photoinitiator include 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethan-1-one (product name: Irgacure 651 / manufacturer: BASF), 1-hydroxy- Cyclohexyl-phenyl-ketone (product name: Irgacure 184 / manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (product name: Irgacure 369 / manufacturer: BASF), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium (product name: Irgacure 784 / manufacturer: BASF), Ebecryl Examples include, but are not limited to, P-115 (manufactured by SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (manufactured by Dow Chemical Co. in USA), Irgacure 264, Irgacure 250 (manufactured by BASF), CIT-1682 (manufactured by Nippon Soda), or mixtures thereof.

[0069] The photopolymer layer contains a fluorine-based compound as a plasticizer.

[0070] The plasticizer facilitates refractive index modulation during the manufacture of a holographic recording medium. More specifically, the plasticizer lowers the glass transition temperature of the polymer matrix to improve the fluidity of the photoreactive monomer. Having a low refractive index and non-reactive properties, the plasticizer is uniformly distributed within the polymer matrix and can contribute to refractive index modulation by migrating in the opposite direction to the movement of the non-photopolymerized photoreactive monomer. The plasticizer can also contribute to improving the moldability of the photopolymer composition.

[0071] The fluorine-based compound may have a low refractive index of 1.45 or less to perform the above-mentioned function of the plasticizer. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less, and the lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. By using a fluorine-based compound having a refractive index lower than that of the above-mentioned photoreactive monomer, the refractive index of the polymer matrix can be lowered and the refractive index modulation with the photoreactive monomer can be increased.

[0072] The photopolymer layer contains a fluorine-based compound represented by the following chemical formula 4, which not only provides excellent optical recording properties but also provides a holographic recording medium with excellent reliability and high transparency even in high temperature / high humidity environments. [ka]

[0073] In chemical formula 4, Z 1 is -O- or -NH-, Z 2 is a single bond, —O— or —NH—, L 1 represents a single bond or a divalent to hexavalent organic group formed by removing a hydroxy group from a polyol having 2 to 6 alcohol groups, n and m are each independently an integer of 1 to 5; the sum of n and m is 2 to 6; R 1 is a methyl group or an ethyl group, R 2 ~R 4 at least one of the groups is a fluorine-containing substituent, which is an alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms and substituted with two or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms and substituted with two or more fluorine atoms; R 2 and R 3 are not fluorine-containing substituents, each independently represents hydrogen, 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 -CH2- groups are substituted with -O-, -S-, or -NH-; R 4 is not a fluorine-containing substituent, it is 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 it is a substituent in which one or more -CH2- groups are substituted with -O-, -S-, or -NH-.

[0074] More specifically, the fluorine-based compound represented by Chemical Formula 4 exhibits a sufficiently low refractive index, thereby increasing refractive index modulation with the photoreactive monomer and effectively fulfilling the role of a basic plasticizer that improves the diffusibility of components in the photopolymer composition. Furthermore, the fluorine-based compound represented by Chemical Formula 4 exhibits little migration to the surface of the photopolymer layer, even in high-temperature and high-humidity environments, and is resistant to heat and humidity, making it less susceptible to decomposition even under high-temperature / high-humidity conditions, thereby improving reliability in high-temperature / high-humidity environments. Furthermore, the fluorine-based compound represented by Chemical Formula 4 exhibits excellent compatibility with components having a high refractive index, ensuring highly transparent optical properties through its excellent humidity and heat resistance.

[0075] In chemical formula 4, L 1 is a moiety containing a carbonyl group and R 4 Therefore, the sum of n and m is 2 to 6, and L 1 is the same as the number of bonds in

[0076] As an example, in Chemical Formula 4, L 1 In Chemical Formula 4, L may be a single bond. 1 When is a single bond, n and m are 1, and Z 2 In this case, the fluorine-based compound represented by Chemical Formula 4 may be represented by the following Chemical Formula 4-1. [ka]

[0077] In chemical formula 4-1, Z 1 ', R 1 ', R 2 ', R 3 ' and R 4 ' are Z in chemical formula 4, respectively. 1 , R 1 , R 2 , R 3 and R 4 is the same as Z 1 ', R 1 ', R 2 ', R 3 ' and R 4 In the present specification, Z′ in Chemical Formula 4 1 , R 1 , R 2 , R 3 and R 4 The substituents may be those described as specific examples of the substituents.

[0078] As another example, in Chemical Formula 4, L 1 is a polyol having 2 to 6 alcohol groups, the hydroxy group of which is Z 1 and Z 2 The hydroxyl group may be a divalent to hexavalent organic group obtained by removing the hydroxyl group from the polyol by substitution with one of the following: glycerol having three alcohol groups; [ka] The trivalent organic group obtained by removing the hydroxy group from [ka] It is expressed as follows.

[0079] In chemical formula 4, L 1 may be, for example, a divalent organic group obtained by removing a hydroxy group from a diol such as ethanediol, propanediol, or butanediol; a trivalent organic group obtained by removing a hydroxy group from a triol such as glycerol or trimethylolpropane; a tetravalent organic group obtained by removing a hydroxy group from a tetraol such as pentaerythritol or ditrimethylolpropane; a pentavalent organic group obtained by removing a hydroxy group from a pentaol such as 6-methylheptanepentaol; or a hexavalent organic group obtained by removing a hydroxy group from a hexaol such as dipentaerythritol.

[0080] In chemical formula 4, L 1 When L is a single bond or a divalent organic group, n and m are each 1. 1 When is a trivalent to hexavalent organic group, n may be greater than m. For example, n may be an integer of 1 to 3, and m may be an integer of 1.

[0081] As an example, L 1 may be a trivalent organic group in the form in which a hydroxy group is removed from glycerol, which is a triol. n may be 2 and m may be 1. In this case, the fluorine-based compound represented by Chemical Formula 4 may be represented by the following Chemical Formula 4-2. [ka]

[0082] In chemical formula 4-2, Z 1” , Z 2” , R 1” , R 2” , R 3” and R 4” are Z in chemical formula 4, respectively. 1 , Z 2 , R 1 , R 2 , R 3 and R4 is the same as Z 1” , Z 2” , R 1” , R 2” , R 3” and R 4” is Z in Chemical Formula 4 in the present specification. 1 , Z 2 , R 1 , R 2 , R 3 and R 4 The substituents may be those described as specific examples of the substituents.

[0083] In chemical formula 4, R 2 ~R 4 At least one of the above is a fluorine-containing substituent. The fluorine-containing substituent may be an alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms and substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms and substituted with two or more fluorines. Specifically, the fluorine-containing substituent may be a linear alkyl group having 1 to 20 carbon atoms and 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, where a is an integer of 0 to 3, an integer of 0 to 2, or an integer of 1, and b is an integer of 0 to 19, an integer of 0 to 15, an integer of 0 to 12, an integer of 0 to 11, an integer of 0 to 10, or an integer of 0 to 9.

[0084] In chemical formula 4, R 2 and R 3 is not a fluorine-containing substituent, R 2 and R 3are each independently a hydrogen atom, 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 may be a substituent in which one or more -CH2- groups are replaced with -O-, -S-, or -NH-.

[0085] Specifically, in Chemical Formula 4, R 2 and R 3 is not a fluorine-containing substituent, R 2 and R 3 are each independently 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 -(R 5 -O) p -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, and R 6 is an alkyl group having 1 to 6 carbon atoms, and p may be an integer of 1 to 12.

[0086] More specifically, in Chemical Formula 4, R 2 and R 3 is not a fluorine-containing substituent, R 2 and R 3 are each independently a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a cyclohexyl group, a tetrahydropyranyl group, a phenyl group, or -(R 5 -O) p -R 6 Here, R 5 R may be an ethylene group, an n-propylene group or an n-butylene group, and in particular may be an ethylene group. 6may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and in particular may be a methyl group. p may be, for example, an integer of 1 to 12, an integer of 1 to 10, an integer of 1 to 8, an integer of 1 to 6, an integer of 1 to 5, an integer of 1 to 4, or an integer of 1 to 3.

[0087] In chemical formula 4, R 4 is not a fluorine-containing substituent, R 4 is 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 -CH2- groups are substituted with -O-, -S-, or -NH-.

[0088] Specifically, in Chemical Formula 4, R 4 is not a fluorine-containing substituent, R 4 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 -(R 5 -O) p -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, and R 6 is an alkyl group having 1 to 6 carbon atoms, and p may be an integer of 1 to 12.

[0089] More specifically, in Chemical Formula 4, R 4 is not a fluorine-containing substituent, R 4 is -(R 5 -O) p -R 6 Here, R 5 R may be an ethylene group, an n-propylene group or an n-butylene group, and in particular may be an ethylene group. 6may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and in particular may be a methyl group. p may be, for example, an integer of 1 to 12, an integer of 1 to 10, an integer of 1 to 8, an integer of 1 to 6, an integer of 1 to 5, an integer of 1 to 4, or an integer of 1 to 3.

[0090] The fluorine-based compound represented by Chemical Formula 4 can include a fluorine-based compound represented by Chemical Formula 4-1, a fluorine-based compound represented by Chemical Formula 4-2, or a mixture thereof. Specifically, the fluorine-based compound represented by Chemical Formula 4 can include one or more fluorine-based compounds selected from the group consisting of fluorine-based compounds represented by the following Chemical Formulas 4-1-1 to 4-1-5 and 4-2-1 to 4-2-5. [ka]

[0091] In chemical formula 4-1-1, R a1 is a methyl group or an ethyl group, R b1 and R b2 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, R c1 is CF3 or CHF2, Z a1 is -O- or -NH-, p1 and p2 each independently represent an integer of 0 to 3; q1 is an integer of 0 to 9. [ka]

[0092] In chemical formula 4-1-2, R a2 is a methyl group or an ethyl group, R b3 and R b4 are each independently a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group; Rc2 is CF3 or CHF2, Z a2 is -O- or -NH-, q2 is an integer of 0 to 9. [ka]

[0093] In chemical formula 4-1-3, R a3 is a methyl group or an ethyl group, R b5 and R b6 are each independently CF3 or CHF2, R c3 is an alkyl group having 1 to 4 carbon atoms, Z a3 is -O- or -NH-, p3 and p4 each independently represent an integer of 0 to 9; q3 is an integer of 0 to 3. [ka]

[0094] In chemical formula 4-1-4, R a4 is a methyl group or an ethyl group, R b7 is CF3 or CHF2, R c4 and R c5 are each independently an alkyl group having 1 to 4 carbon atoms, Z a4 is -O- or -NH-, p5 is an integer from 0 to 9, q4 and q5 each independently represent an integer of 0 to 3. [ka]

[0095] In chemical formula 4-1-5, Ra5 is a methyl group or an ethyl group, R b8 is CF3 or CHF2, R b9 is a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group, R c6 is an alkyl group having 1 to 4 carbon atoms, Z a5 is -O- or -NH-, p6 is an integer from 0 to 9, q6 is an integer of 0 to 3. [ka]

[0096] In chemical formula 4-2-1, R a6 is a methyl group or an ethyl group, R b10 and R b11 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, R c7 and R c8 are each independently CF3 or CHF2, Z a6 is -O- or -NH-, p7 and p8 each independently represent an integer of 0 to 3; q7 and q8 each independently represent an integer of 0 to 9. [ka]

[0097] In chemical formula 4-2-2, R a7 is a methyl group or an ethyl group, R b12 and R b13 are each independently CF3 or CHF2, R c9 and R c10are each independently an alkyl group having 1 to 4 carbon atoms, Z a7 is -O- or -NH-, p9 and p10 each independently represent an integer of 0 to 9; q9 and q10 each independently represent an integer of 0 to 3. [ka]

[0098] In chemical formula 4-2-3, R a8 is a methyl group or an ethyl group, R b14 and R b15 are each independently a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group; R c11 and R c12 are each independently CF3 or CHF2, Z a8 is -O- or -NH-, q11 and q12 each independently represent an integer of 0 to 9. [ka]

[0099] In chemical formula 4-2-4, R a9 is a methyl group or an ethyl group, R b16 is CF3 or CHF2, R b17 is a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group, R c13 and R c14 are each independently an alkyl group having 1 to 4 carbon atoms, Z a9 is -O- or -NH-, p11 is an integer from 0 to 9, q13 and q14 each independently represent an integer of 0 to 3. [ka]

[0100] In chemical formula 4-2-5, R a10 is a methyl group or an ethyl group, R b18 is CF3 or CHF2, R c15 ~R c17 are each independently an alkyl group having 1 to 4 carbon atoms, Z a10 is -O- or -NH-, p12 is an integer from 0 to 9, q15 to q17 each independently represent an integer of 0 to 3.

[0101] The photopolymer layer may contain 20 to 200 parts by weight of a 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 content satisfies the above range, there are no problems such as poor compatibility with components contained in the photopolymer layer, elution of some of the fluorine-based compound onto the surface of the photopolymer layer, or poor haze. Furthermore, the fluorine-based compound has a sufficiently low refractive index, allowing for a large refractive index modulation value after recording, which is advantageous for ensuring excellent optical recording properties.

[0102] The photopolymer layer may additionally contain additives such as antifoaming agents.

[0103] The photopolymer layer may contain a silicone-based reactive additive as an antifoaming agent, such as commercially available products such as Tego Rad 2500.

[0104] The content of the additive, for example, the antifoaming agent, can be appropriately adjusted to a level that does not impair the function of the holographic recording medium.

[0105] The photopolymer layer may be formed from a photopolymer composition that includes a solvent.

[0106] The solvent may be an organic solvent, and may be, for example, one or more organic solvents selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited thereto. Specific examples of such organic solvents include one or more selected from the group consisting of ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, and t-butanol; acetates such as ethyl acetate, i-propyl acetate, and polyethylene glycol monomethyl ether acetate; and ethers such as tetrahydrofuran and propylene glycol monomethyl ether.

[0107] The organic solvent may be added when the components contained in the photopolymer composition are mixed, or may be added to the photopolymer composition while the components are dispersed or mixed in the organic solvent.

[0108] The photopolymer composition may contain a solvent so that the solids concentration is 1 to 90 wt%. Specifically, the photopolymer composition may contain a solvent so that the solids concentration is 20 wt% or more, 30 wt% or more, 50 wt% or more, or 60 wt% or more, and 85 wt% or less, 80 wt% or less, 75 wt% or less, or 70 wt% or less. Within these ranges, the photopolymer composition exhibits appropriate flowability, can form a coating film without defects such as streaks, and can form a photopolymer layer with desired physical properties and surface characteristics without defects during the drying and curing process.

[0109] The holographic recording medium of one embodiment includes the above-described photopolymer layer, and thus can exhibit excellent reliability and high transparency even in high temperature / high humidity environments.

[0110] Specifically, in one embodiment of the holographic recording medium, the refractive index change calculated by the following formula 4 is 1.0% or less.

[0111] Refractive index change (%) = {|1-n1 / n0|} × 100 (Equation 4) In Equation 4, n0 is the refractive index of a sample of a holographic recording medium before recording that was stored at a temperature of 20-25°C and a relative humidity of 40-50% and then bleached with a white LED, and n1 is the refractive index of a sample of a holographic recording medium before recording that was stored at a temperature of 60°C and a relative humidity of 90% for 72 hours and then bleached with a white LED.

[0112] A refractive index change of 1.0% or less means that the holographic recording medium before recording exhibits excellent stability even when exposed to high temperature and humidity conditions, with a small difference in refractive index of 1.0% or less before and after exposure. In particular, because the plasticizer contained in the holographic recording medium before recording is fluid, it may migrate to the surface of the photopolymer layer, preventing the intended optical recording characteristics from being achieved. However, the holographic recording medium of one embodiment contains a fluorine-based compound represented by Chemical Formula 4 as a plasticizer, resulting in a very small refractive index change calculated by Formula 4.

[0113] The upper limit of the refractive index change of the holographic recording medium may be, for example, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.25% or less, or 0.2% or less, and the lower limit may be, for example, 0% or more.

[0114] On the other hand, since holographic recording media use a mixture of components having a low refractive index and a high refractive index to record optical properties, they tend to have opaque properties due to the miscibility between these components. However, the holographic recording media of one embodiment can exhibit highly transparent optical properties by using a fluorine-based compound with a specific structure that has excellent miscibility.

[0115] Specifically, the haze of the holographic recording medium of one embodiment is 2% or less. The upper limit of the haze may be, for example, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, or 0.7% or less. The lower limit of the haze is not particularly limited and may be 0% or more. The haze can be measured by the method described in the test examples below.

[0116] The holographic recording medium of one embodiment has excellent refractive index modulation, diffraction efficiency, and driving reliability despite having a thin photopolymer layer.

[0117] 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.

[0118] The holographic recording medium of one embodiment may further include a substrate on at least one side of the photopolymer layer. The type of substrate is not particularly limited, and substrates known in the related technical field may be used. For example, substrates such as glass, PET (polyethylene terephthalate), TAC (triacetyl cellulose), PC (polycarbonate), and COP (cycloolefin polymer) may be used.

[0119] The holographic recording medium of one embodiment may have high diffraction efficiency. For example, when a notch filter hologram is recorded on the holographic recording medium, the holographic recording medium may 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 on the holographic recording medium, 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, 90% or more, or 91% or more. Thus, the holographic recording medium of one embodiment may achieve excellent diffraction efficiency even when including a thin photopolymer layer. The diffraction efficiency can be measured using the method described in the test examples below.

[0120] In one embodiment, the holographic recording medium can achieve a refractive index modulation value (Δn) of 0.020 or more, 0.025 or more, 0.026 or more, 0.027 or more, 0.028 or more, 0.029 or more, 0.030 or more, 0.031 or more, 0.032 or more, 0.033 or more, 0.034 or more, or 0.035 or more, even when the photopolymer layer is as thin as 5 to 30 μm. The upper limit of the refractive index modulation value is not particularly limited, but may be, for example, 0.060 or less. The refractive index modulation value can be measured by the method described in the test examples below.

[0121] The holographic recording medium of one embodiment not only exhibits excellent durability in a high temperature / high humidity environment before recording, but also exhibits excellent durability in a high temperature / high humidity environment after recording.

[0122] As an example, the holographic recording medium of one embodiment may have a peak variation calculated by the following formula 3 of 3% or less.

[0123] Peak change = {|1-A1 / A0|} x 100 (Equation 3) In the above formula 3, A0 is the wavelength at which the holographic recording medium has the lowest transmittance in the wavelength range of 300 to 1,200 nm, and A1 is the wavelength at which the holographic recording medium has the lowest transmittance measured after being exposed to conditions of a temperature of 60°C and a relative humidity of 90% for 72 hours.

[0124] The peak shift describes the degree of shift in the wavelength showing the minimum transmittance before and after exposure to high temperature and humidity conditions. For example, if a hologram grating (e.g., a reflection hologram) is recorded to reflect light of a specific wavelength of 680 nm, the transmittance at 680 nm will have a minimum value. Then, if the transmittance is measured again after exposure to high temperature and humidity conditions, the minimum transmittance may be found at 675 nm. In this case, according to Equation 1 above, a peak shift of less than 1% is considered to occur. Thus, as the grating spacing decreases (i.e., the grating shrinks) depending on the conditions under which the hologram grating is operated or stored, a peak shift occurs in which the wavelength of the minimum transmittance shifts to a shorter wavelength. Conversely, as the grating spacing increases (i.e., the grating expands), a peak shift occurs in which the wavelength of the minimum transmittance shifts to a longer wavelength. The extent of this peak shift depends on the reliability of the grating.

[0125] In other words, a peak change of 3% or less means that the deformation (shrinkage or expansion) of the diffraction grating can be suppressed so that the peak change is 3% or less even when exposed to harsh conditions such as high temperature and high humidity. Such a holographic recording medium can provide good color reproducibility and image clarity even when exposed to harsh conditions.

[0126] The peak change for the holographic recording medium of one embodiment may be, for example, 2.5% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, or 1.1% or less. The lower limit of the peak change is not particularly limited and may be 0% or more.

[0127] The holographic recording medium may have a notch filter structure in conjunction with the diffraction grating structure. In one embodiment, a holographic recording medium having a notch filter structure may mean, for example, that the diffraction grating is non-slanted (substantially 0°) relative to the substrate surface, i.e., parallel to the substrate surface. Such a holographic recording medium may have a structure in which two layers with different refractive indices (e.g., a high refractive index layer and a low refractive index layer) are alternately repeated. The two repeated layers may have the same or different thicknesses. Such a non-slanted diffraction grating recording may be fabricated by making the angles of incidence of the incident object beam and reference beam equal relative to the normal. A non-slanted structure allows for a clearer degree of deformation (e.g., contraction or expansion) under high temperature / high humidity conditions than a slanted structure, and is less susceptible to the contraction and expansion of the substrate.

[0128] The application of the holographic recording medium of one embodiment is not particularly limited. As a non-limiting example, the holographic recording medium can be used in applications where there is a high possibility of exposure to high temperature / high humidity environments, specifically, smart devices such as mobile devices, components of wearable displays, or automotive components (e.g., head-up displays).

[0129] Meanwhile, in one embodiment, a holographic recording medium can be manufactured by applying a photopolymer composition to form a photopolymer layer, and then irradiating a predetermined region of the thus-prepared photopolymer layer with a coherent laser to selectively polymerize the photoreactive monomer contained in the photopolymer layer, thereby recording optical information.

[0130] In the step of forming the photopolymer layer, a photopolymer composition having the above-described structure can be first prepared. When preparing the photopolymer composition, a commonly known mixer, stirrer, or mixer can be used without any limitation to mix the components. This mixing process can be carried out at a temperature ranging from 0°C to 100°C, from 10°C to 80°C, or from 20°C to 60°C.

[0131] In the step of forming the photopolymer layer, a prepared photopolymer composition can be applied to form a coating film formed 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 groups of the (meth)acrylic polyol that remain unreacted and the silane functional groups of the siloxane polymer.

[0132] The photopolymer layer manufactured by the step of forming the photopolymer layer may have a fluorine-based compound, a photoreactive monomer, a photoinitiator system, and optional additives uniformly dispersed in a crosslinked polymer matrix.

[0133] Then, when a coherent laser is irradiated onto the photopolymer layer in the step of recording optical information, polymerization of the photoreactive monomer occurs in the area where constructive interference occurs, forming a photopolymer, while polymerization of the photoreactive monomer does not occur or is suppressed in the area where destructive interference occurs, leaving the photoreactive monomer. The unreacted photoreactive monomer then diffuses into the photopolymer where the concentration of the photoreactive monomer is low, causing refractive index modulation, which generates a diffraction grating. As a result, a hologram, i.e., optical information, is recorded in the photopolymer layer with the diffraction grating.

[0134] In one embodiment, the holographic recording medium 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 photobleaching, which is performed after the step of recording optical information by irradiating light entirely onto the photopolymer layer on which the optical information has been recorded.

[0135] For example, in the photobleaching step, ultraviolet rays (UVA) in the range of 320 to 400 nm are irradiated to terminate the reaction of the photoreactive monomer, thereby removing the color of the photosensitive dye.

[0136] Meanwhile, according to another embodiment of the present invention, there is provided a holographic recording medium comprising: a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer having a silane functional group and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer comprising a fluorine-based compound represented by the following chemical formula 4: [ka]

[0137] In chemical formula 4, Z 1 is -O- or -NH-, Z 2 is a single bond, —O— or —NH—, L 1is a single bond or a divalent to hexavalent organic group obtained by removing a hydroxy group from a polyol having 2 to 6 alcohol groups, n and m are each independently an integer of 1 to 5; the sum of n and m is 2 to 6; R 1 is a methyl group or an ethyl group, R 2 ~R 4 at least one of the groups is a fluorine-containing substituent, which is an alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms and substituted with two or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms and substituted with two or more fluorine atoms; R 2 and R 3 are not fluorine-containing substituents, each independently represents hydrogen, 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 -CH2- groups are replaced by -O-, -S-, or -NH-; R 4 is not a fluorine-containing substituent, it is 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 -CH2- groups are substituted with -O-, -S-, or -NH-.

[0138] The holographic recording medium according to another embodiment contains a fluorine-based compound having a specific structure as a plasticizer, thereby exhibiting improved optical recording properties and also exhibiting optical properties such as high reliability and high transparency even in high temperature / high humidity environments.

[0139] Holographic recording media according to other embodiments may exhibit high reliability even in high temperature / high humidity environments, for example, to the extent that the refractive index change calculated by the above formula 4 has a low value of 1.0% or less, and may exhibit high transparency with a haze of 2% or less, but are not limited thereto.

[0140] The polymer matrix or its precursor, the photoreactive monomer and photoinitiator system or the photopolymer obtained therefrom, and the fluorine-based compound represented by Chemical Formula 4 contained in the holographic recording medium according to the other embodiment may be the same as those contained in the holographic recording medium according to the first embodiment. The polymer matrix or its precursor, the photoreactive monomer and photoinitiator system or the photopolymer obtained therefrom, and the fluorine-based compound represented by Chemical Formula 4 have been described in detail above, so a detailed description thereof will be omitted here.

[0141] Meanwhile, according to still another embodiment of the present invention, there is provided an optical element including a holographic recording medium.

[0142] Specific examples of optical elements include smart devices such as mobile devices, components of wearable displays, vehicle accessories (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffractive elements, light guides, waveguides, holographic optical elements having the functions of projection screens and / or masks, media and light diffusion plates in optical memory systems, optical wavelength splitters, reflective and transmissive color filters, etc.

[0143] An example of an optical device including a holographic recording medium is a holographic display device, which includes a light source unit, an input unit, an optical system, and a display unit.

[0144] Specifically, the light source unit is a part that emits a laser beam used to provide, record, and reproduce three-dimensional image information of an object in the input unit and display unit.

[0145] The input unit is a part that inputs 3D image information of an object to be recorded on the display unit in advance. Specifically, it is a part that can input 3D information of an object such as spatial light intensity and phase into an electrically addressed liquid crystal SLM (Spatial Light Modulator), and can use the input beam at this time.

[0146] The optical system may be composed of mirrors, polarizers, beam splitters, beam shutters, lenses, etc. The optical system can distribute the laser beam emitted from the light source section into an input beam sent to the input section, a recording beam, a reference beam, an erasing beam, a read beam, etc. sent to the display section.

[0147] The display unit receives 3D image information of an object from the input unit, records it on a hologram plate consisting of an optically addressed SLM, and reconstructs the 3D image of the object. The 3D image information of the object can be recorded by the interference of the input beam and the reference beam. The 3D image information of the object recorded on the hologram plate can be reconstructed as a 3D image by the diffraction pattern generated by the read beam, and the erase beam can be used to quickly remove the formed diffraction pattern. Meanwhile, the hologram plate can be moved between the position where the 3D image is input and the position where it is reconstructed. [Effects of the Invention]

[0148] The holographic recording medium according to an embodiment of the present invention not only has excellent optical recording properties, but also exhibits transparent optical properties and excellent reliability even in high temperature and high humidity environments. [Brief explanation of the drawings]

[0149] [Figure 1]This diagram shows a schematic diagram of a recording device setup for holographic recording. Specifically, it shows the process in which a laser beam of a predetermined wavelength is emitted from a light source 10, then passes through mirrors 20 and 20', an iris 30, a spatial filter 40, an iris 30', a collimation lens 50, and a polarized beam splitter (PBS) 60, before being irradiated onto a holographic recording medium (PP) 80 positioned on one side of a mirror 70. DETAILED DESCRIPTION OF THE INVENTION

[0150] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, but these are presented as examples of the present invention and are not intended to limit the scope of the present invention in any way.

[0151] In the following Production Examples, Examples, Comparative Examples, etc., the contents of raw materials, etc. refer to the contents on a solid basis unless otherwise specified.

[0152] Production Example 1: Production of (meth)acrylic polyol A 2L jacketed reactor was charged with 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate, and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60-70°C, and stirring was continued for 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added, and stirring was continued for another 30 minutes. 0.24g of the polymerization initiator AIBN (azobisisobutyronitrile) was then added, and polymerization was continued for at least 4 hours at the reaction temperature until the residual acrylate content was less than 1%. This produced a (meth)acrylate copolymer with hydroxyl groups located in the branched chain (weight average molecular weight approximately 300,000, OH equivalent approximately 1802g / equivalent).

[0153] Example 1: Preparation of photopolymer composition and holographic recording medium (1) Preparation of photopolymer composition 1.27 g of poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number average molecular weight: approximately 390, Si-H equivalent: approximately 103 g / equivalent) as a siloxane polymer and 11.12 g of the (meth)acrylic polyol prepared in Preparation Example 1 were mixed first (SiH / OH molar ratio = 2.0).

[0154] Then, 20g of HR6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.08g of H-Nu640 (Spectra), 0.3g of Borate V and 0.05g of H-Nu254 (Spectra) as co-initiators, 10g of a fluorine-based compound represented by the following chemical formula a as a plasticizer, and 26g of methyl isobutyl ketone (MIBK) as a solvent were added and stirred in a paste mixer for approximately 30 minutes in the dark. A Karstedt (Pt-based) catalyst was then added for matrix crosslinking to produce a photopolymer composition. [ka]

[0155] (2) Manufacturing of holographic recording media The photopolymer composition was coated to a predetermined thickness on a 60 μm thick TAC substrate using a Mayer bar and dried for 10 minutes at 80° C. After drying, the thickness of the photopolymer layer was approximately 15 μm.

[0156] A diffraction grating was recorded using the setup shown in Figure 1. Specifically, the manufactured photopolymer layer was laminated on a mirror, and then irradiated with a laser. The interference between incident light L and light L' reflected by the mirror records a notch filter hologram with periodic refractive index modulation in the thickness direction. In this example, the notch filter hologram was recorded with an incident angle of 0°. Notch filters and Bragg reflectors are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indices are repeatedly stacked periodically at a constant thickness.

[0157] Examples 2 to 11 and Comparative Examples 1 to 4: Production of photopolymer compositions and holographic recording media Photopolymer compositions and holographic recording media were produced using the same methods as in Example 1, except that the components and contents of the photopolymer compositions were changed as shown in Table 1 below.

[0158] [Table 1] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0159] Test example: Performance evaluation of holographic recording media (1) Diffraction efficiency The diffraction efficiency (η) was calculated using the following formula 1.

[0160] η(%)={P D / (P D +P T )}×100 (Equation 1) In Equation 1, η is the diffraction efficiency, and P D is the power (mW / cm) of the diffracted beam in the sample after recording. 2 ) and P T is the power (mW / cm) of the beam transmitted through the sample after recording. 2 )

[0161] (2) Refractive index modulation value (Δn) The refractive index modulation value (Δn) was calculated using the following formula 2 and Bragg's equation.

number

[0162]

number

[0163] In the above formula, η is the reflectivity 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 incident angle of the incident light for recording, φ is the slant angle of the grating, Δn is the refractive index modulation value, n is the refractive index of the photopolymer, and Λ is the period of the diffraction grating. In the examples and comparative examples, holograms were recorded using a notch filter method, so θ (incident angle) and φ (slant angle of the grating) were both 0°.

[0164] (3) Hayes The haze was measured using a haze meter (Murakami Color Research Laboratory, HM-150) in accordance with JIS K 7136. The measuring light was incident on the side of the substrate of the holographic recording medium.

[0165] (4) Peak change To evaluate the reliability of holographic recording media with recorded diffraction gratings in high-temperature / high-humidity environments, we confirmed the degree of shift in the wavelength showing the maximum reflectance before and after exposing a sample with recorded diffraction gratings to high-temperature / high-humidity conditions.

[0166] First, the specific wavelength (or wavelength band) (A0) at which the sample with the recorded diffraction grating exhibited the maximum reflectance (i.e., the minimum transmittance) was analyzed (analysis was performed at room temperature and under non-humid conditions). A UV-Vis (Ultra Violet-Visible) spectrometer was used for the analysis, and the analytical wavelength range was 300 to 1,200 nm.

[0167] The same sample was then stored for 72 hours under conditions of 60°C and 90% relative humidity, and the wavelength (or wavelength band) (A1) with maximum reflectance (minimum transmittance) was recorded in the same manner. The peak change, which is the degree of shift in the wavelength with minimum transmittance before and after evaluation, was measured using the following equation 3. It was assumed that deformation (e.g., shrinkage or expansion) of the sample did not affect the surface pitch and occurred only in the direction perpendicular to the sample surface.

[0168] Peak change = {|1-A1 / A0|} x 100 (Equation 3) (5) Refractive index change To evaluate the stability of the holographic recording medium before recording the diffraction grating in a high-temperature / high-humidity environment, the degree of change in refractive index of the sample before recording the diffraction grating was confirmed before and after exposing it to high-temperature / high-humidity conditions.

[0169] Specifically, the holographic recording media before recording, manufactured as in the examples and comparative examples, were stored under constant temperature (20-25°C) and humidity (40-50% relative humidity) conditions, and then bleached with a white LED to prepare samples that had not been exposed to a high temperature / humidity environment before recording. The refractive index n0 of the samples was then measured using a prism coupler (SPA-3DR, SAIRON TECHNOLOGY).

[0170] Meanwhile, the unrecorded holographic recording media manufactured in the examples and comparative examples were stored at a temperature of 60°C and a relative humidity of 90% for 72 hours, and then bleached with a white LED to prepare samples exposed to a high temperature / high humidity environment before recording. The refractive index n1 of the samples was also measured using a prism coupler.

[0171] The refractive index change was calculated by substituting n0 and n1 into the following formula 4. Refractive index change (%) = {|1-n1 / n0|} × 100 (Equation 4) In Equation 4, n0 is the refractive index of a sample of a holographic recording medium before recording that was stored at a temperature of 20-25°C and a relative humidity of 40-50% and then bleached with a white LED, and n1 is the refractive index of a sample of a holographic recording medium before recording that was stored at a temperature of 60°C and a relative humidity of 90% for 72 hours and then bleached with a white LED.

[0172] [Table 2]

[0173] Referring to Table 2, it can be seen that the holographic recording media manufactured in Examples 1 to 11 exhibited excellent diffraction efficiency, refractive index modulation values, and low haze, and also exhibited excellent reliability even after exposure to high temperature / high humidity environments before and after recording. In contrast, the holographic recording media manufactured in Comparative Examples 2 to 4 were poor in optical recording properties, haze, and reliability in high temperature / high humidity environments, and the holographic recording media manufactured in Comparative Example 1 had excellent optical recording properties but high haze and showed poor reliability in high temperature / high humidity environments before and after recording.

[0174] This confirms that the holographic recording medium according to one embodiment of the present invention exhibits excellent optical recording properties, excellent reliability even in high temperature / high humidity environments, and high transparency due to the inclusion of a fluorine-based compound with a specific structure.

Claims

1. A holographic recording medium, a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol, or a precursor thereof; a photoreactive monomer and photoinitiator system or a photopolymer obtained therefrom; a photopolymer layer containing a fluorine-based compound, The refractive index change calculated by the following formula 4 is 1.0% or less, Refractive index change (%) = {|1-n １ / n ０ |}×100 (Formula 4) In formula 4, n ０ is the refractive index of a sample obtained by storing a holographic recording medium before recording at a temperature of 20 to 25°C and a relative humidity of 40 to 50%, and then bleaching it with a white LED, n １ is the refractive index of a sample obtained by storing an unrecorded holographic recording medium at a temperature of 60° C. and a relative humidity of 90% for 72 hours and then bleaching it with a white LED, A hologram recording medium, wherein the haze of the hologram recording medium is 2% or less.

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

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

4. The photoreactive monomer is Benzyl (meth)acrylate, benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, 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 one or more polyfunctional monomers selected from the group consisting of di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolac epoxy (meth)acrylate; or 3. The holographic recording medium according to claim 1, comprising a mixture of two or more of these materials.

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

6. The coinitiator includes a borate anion represented by the following formula 3: BX １ X ２ X ３ X ４ (Chemical Formula 3) In chemical formula 3, X １ ~X ４ each independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 30 carbon atoms, arylalkyl group having 7 to 30 carbon atoms, alkylaryl group having 7 to 30 carbon atoms, or allyl group, X １ ~X ４ The holographic recording medium according to claim 5 , wherein at least one of is not an aryl group.

7. The fluorine-based compound includes a fluorine-based compound represented by the following chemical formula 4: 【Transformation 3】 In chemical formula 4, Z １ is —O— or —NH—, Z ２ is a single bond, —O— or —NH—, L １ represents a single bond or a divalent to hexavalent organic group formed by removing a hydroxy group from a polyol having 2 to 6 alcohol groups, n and m are each independently an integer from 1 to 5; the sum of n and m is 2 to 6; R １ is a methyl group or an ethyl group, R ２ ~R ４ at least one of the above is a fluorine-containing substituent, which is an alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorine atoms, a cycloalkyl group having 3 to 30 carbon atoms and substituted with two or more fluorine atoms, or an aryl group having 6 to 30 carbon atoms and substituted with two or more fluorine atoms, R ２ and R ３ are not fluorine-containing substituents, each independently represents hydrogen, 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 one or more —CH ２ - is a substituent substituted with -O-, -S- or -NH-, R ４ is not a fluorine-containing substituent, it is 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 one or more of the substituents -CH ２ 3. The holographic recording medium according to claim 1, wherein - is a substituent substituted with -O-, -S- or -NH-.

8. L in Chemical Formula 4 １ teeth, a single bond, or 8. The holographic recording medium according to claim 7, wherein the trivalent organic group is a triol in which a hydroxy group has been removed from glycerol.

9. 8. The holographic recording medium according to claim 7, wherein the fluorine-containing substituent is a linear alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorine atoms.

10. The fluorine-containing substituent is —(CH ２ ) ａ (CF ２ ) ｂ CHF ２ or -(CH ２ ) ａ (CF ２ ) ｂ CF ３ and a is an integer from 0 to 3, 8. The holographic recording medium according to claim 7, wherein b is an integer of 0 to 19.

11. In chemical formula 4, R ２ and R ３ is not a fluorine-containing substituent, R ２ and R ３ are each independently 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 and R ５ is an alkylene group having 1 to 6 carbon atoms, R ６ is an alkyl group having 1 to 6 carbon atoms, 8. The holographic recording medium according to claim 7, wherein p is an integer from 1 to 12.

12. In chemical formula 4, R ４ is not a fluorine-containing substituent, R ４ 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 and R ５ is an alkylene group having 1 to 6 carbon atoms, R ６ is an alkyl group having 1 to 6 carbon atoms, 8. The holographic recording medium according to claim 7, wherein p is an integer from 1 to 12.

13. The fluorine-based compound represented by Chemical Formula 4 includes one or more fluorine-based compounds selected from the group consisting of fluorine-based compounds represented by the following Chemical Formulas 4-1-1 to 4-1-5 and the following Chemical Formulas 4-2-1 to 4-2-5, 【Chemistry 4】 In chemical formula 4-1-1, R ａ１ is a methyl group or an ethyl group, R ｂ１ and R ｂ２ are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, R ｃ１ is CF ３ or CHF ２ and Z ａ１ is —O— or —NH—, p1 and p2 each independently represent an integer of 0 to 3; q1 is an integer from 0 to 9, 【Transformation 5】 In chemical formula 4-1-2, R ａ２ is a methyl group or an ethyl group, R ｂ３ and R ｂ４ are each independently a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group; R ｃ２ is CF ３ or CHF ２ and Z ａ２ is —O— or —NH—, q2 is an integer from 0 to 9, 【Transformation 6】 In chemical formula 4-1-3, R ａ３ is a methyl group or an ethyl group, R ｂ５ and R ｂ６ are each independently CF ３ or CHF ２ and R ｃ３ is an alkyl group having 1 to 4 carbon atoms, Z ａ３ is —O— or —NH—, p3 and p4 each independently represent an integer of 0 to 9; q3 is an integer from 0 to 3, 【Transformation 7】 In chemical formula 4-1-4, R ａ４ is a methyl group or an ethyl group, R ｂ７ is CF ３ or CHF ２ and R ｃ４ and R ｃ５ are each independently an alkyl group having 1 to 4 carbon atoms, Z ａ４ is —O— or —NH—, p5 is an integer from 0 to 9, q4 and q5 each independently represent an integer of 0 to 3; 【Transformation 8】 In chemical formula 4-1-5, R ａ５ is a methyl group or an ethyl group, R ｂ８ is CF ３ or CHF ２ and R ｂ９ is a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group, R ｃ６ is an alkyl group having 1 to 4 carbon atoms, Z ａ５ is —O— or —NH—, p6 is an integer from 0 to 9, q6 is an integer of 0 to 3, 【Chemistry 9】 In chemical formula 4-2-1, R ａ６ is a methyl group or an ethyl group, R ｂ１０ and R ｂ１１ are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, R ｃ７ and R ｃ８ are each independently CF ３ or CHF ２ and Z ａ６ is —O— or —NH—, p7 and p8 each independently represent an integer of 0 to 3; q7 and q8 each independently represent an integer of 0 to 9; 【Chemistry 10】 In chemical formula 4-2-2, R ａ７ is a methyl group or an ethyl group, R ｂ１２ and R ｂ１３ are each independently CF ３ or CHF ２ and R ｃ９ and R ｃ１０ are each independently an alkyl group having 1 to 4 carbon atoms, Z ａ７ is —O— or —NH—, p9 and p10 each independently represent an integer of 0 to 9; q9 and q10 each independently represent an integer of 0 to 3, 【Chemistry 11】 In chemical formula 4-2-3, R ａ８ is a methyl group or an ethyl group, R ｂ１４ and R ｂ１５ are each independently a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group; R ｃ１１ and R ｃ１２ are each independently CF ３ or CHF ２ and Z ａ８ is —O— or —NH—, q11 and q12 each independently represent an integer of 0 to 9, 【Chemistry 12】 In chemical formula 4-2-4, R ａ９ is a methyl group or an ethyl group, R ｂ１６ is CF ３ or CHF ２ and R ｂ１７ is a cyclohexyl group, a tetrahydropyranyl group, or a phenyl group, R ｃ１３ and R ｃ１４ are each independently an alkyl group having 1 to 4 carbon atoms, Z ａ９ is —O— or —NH—, p11 is an integer from 0 to 9, q13 and q14 each independently represent an integer of 0 to 3; 【Chemistry 13】 In chemical formula 4-2-5, R ａ１０ is a methyl group or an ethyl group, R ｂ１８ is CF ３ or CHF ２ and R ｃ１５ ~R ｃ１７ are each independently an alkyl group having 1 to 4 carbon atoms, Z ａ１０ is —O— or —NH—, p12 is an integer from 0 to 9, 8. The holographic recording medium according to claim 7, wherein q15 to q17 are each independently an integer of 0 to 3.

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

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

16. 3. The holographic recording medium according to claim 1, wherein the photopolymer layer has a thickness of 5 to 30 μm, and the refractive index modulation value of the holographic recording medium is 0.020 or more.

17. An optical element comprising the holographic recording medium according to claim 1 or 2.

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