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 characteristics, but also exhibits transparent optical characteristics 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. 10-2022-0146042 dated November 4, 2022 and Korean Patent Application No. 10-2022-0146046 dated November 4, 2022, and all contents disclosed in the documents of said Korean patent applications 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 thus recorded.

[0004] In this regard, the photopolymer composition can be used to manufacture holograms. Photopolymers can easily store optical interference patterns as holograms by photopolymerization of photoreactive monomers. Therefore, photopolymers can be used in a variety of fields, such as smart devices such as mobile devices, parts of wearable displays, vehicle accessories (e.g., head up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffraction members, light guides, wave guides, holographic optical elements having the functions of projection screens and / or masks, media and optical diffusion plates in optical memory systems, 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 local photopolymerization process induces a 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 is wider with decreasing thickness.

[0007] Recently, there has been an increasing demand for the development of materials that have high diffraction efficiency and can stably maintain holograms, and various attempts are being made to manufacture holographic recording media that have high diffraction efficiency and refractive index modulation values ​​while being thin.

[0008] Meanwhile, when a holographic recording medium is used as an optical element in applications such as mobile devices and vehicle accessories (e.g., head-up displays), it is placed in a high-temperature / high-humidity environment. In this case, the diffraction grating may deform, distorting the image or failing to perform its intended function. Therefore, it is necessary to develop a photopolymer layer and a holographic recording medium including the same that exhibit minimal diffraction grating deformation and are highly reliable 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] In the present specification, unless otherwise specified, the term "hologram recording medium" refers to a medium (or media) capable of recording optical information in the entire visible light range and ultraviolet light range (e.g., 300 to 1,200 nm) by an exposure process. Thus, the term "hologram recording medium" in the present specification may refer to a medium on which optical information is recorded, or to a medium before recording in a state in which optical information can be recorded. The term "hologram" in the present specification 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, or holographic stereograms.

[0013] In the present specification, in relation to the environmental conditions in which a holographic recording medium or an element including the same is placed, "high temperature" may mean a temperature of 60°C or higher. For example, high temperature may mean a temperature of 65°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, 85°C or higher, or 90°C or higher, and the upper limit 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 a different temperature is specifically mentioned, the temperature condition under which the characteristics are measured or described may mean room temperature (for example, a temperature in the range of about 15 to 30°C, which is a temperature at which no cooling or heating is performed).

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

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

[0016] According to one embodiment of the present invention, there is provided a holographic recording medium comprising a photopolymer layer including 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 fluorine-based compound, the peak variation calculated by the following formula 3 being 3% or less, and the photopolymer layer is laminated with an optically transparent adhesive layer, and after storing the photopolymer layer at a temperature of 60°C and a relative humidity of 90% for 72 hours, the adhesive strength measured under conditions of a peel angle of 180° and a peel speed of 5 mm / sec is 500 gf / 2.5 cm or more.

[0017] Peak change = {|1-A1 / A0|} x 100 (Equation 3) In formula 3, A0 is the wavelength at which the holographic recording medium has the minimum transmittance in the wavelength range of 300 to 1,200 nm, and A1 is the wavelength at which the holographic recording medium has the minimum transmittance measured after being exposed to conditions of a temperature of 60°C and a relative humidity of 90% for 72 hours.

[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 characteristics while also exhibiting optical characteristics that are highly reliable and highly transparent even in high temperature / high humidity environments, and have thus 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] The holographic recording medium of 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 including a fluorine-based compound.

[0021] The photopolymer layer may be a pre-recorded photopolymer layer on which optical information can be recorded, or may be a photopolymer layer with optical information recorded thereon.

[0022] A photopolymer layer in which optical information is recorded can be manufactured by irradiating an object beam and a reference beam onto an unrecorded photopolymer layer. When an object beam and a reference beam are irradiated onto an unrecorded photopolymer layer, the photoinitiator system is in an inactive state in the destructive interference region due to the interference length between the object beam and the reference beam, so photopolymerization of the photoreactive monomer does not occur, and the photoinitiator system is activated in the reinforcement interference region to photopolymerize the photoreactive monomer. In the reinforcement interference region, the photoreactive monomer is continuously consumed, so that a concentration difference occurs between the destructive interference region and the reinforcement interference region. As a result, the photoreactive monomer in the destructive interference region diffuses into the reinforcement interference region. At this time, the fluorine-based compound of the plasticizer moves in the opposite direction to the photoreactive monomer. The photoreactive monomer and the photopolymer formed therefrom have a higher refractive index than the polymer matrix and the fluorine-based compound, so that a spatial refractive index change occurs in the photopolymer layer, and a grating is generated due to the spatial refractive index modulation occurring in the photopolymer layer. 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 a wavelength is incident during recording 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, reproducing the hologram optical information.

[0023] Thus, when the photopolymer layer is in a pre-recorded state, the photopolymer layer may include the photoreactive monomer, the photoinitiator system, and the fluorine-based compound randomly dispersed within a polymer matrix or a precursor thereof.

[0024] In contrast, if the photopolymer layer has optical information recorded therein, the photopolymer layer may include 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 including a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing silane functional groups and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system; and a fluorine-based compound.

[0026] The polymer matrix plays a role of a support for the photopolymer layer, and is formed by crosslinking a siloxane-based polymer containing a silane functional group (Si-H) and a (meth)acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking a (meth)acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxyl group of the (meth)acrylic polyol can form a crosslink with the silane functional group of the siloxane polymer by a hydrosilylation reaction. The hydrosilylation reaction can be rapidly carried out under a Pt-based catalyst even at room temperature (for example, a temperature in a state without heating or cooling, in the range of about 15 to 30°C). Therefore, the holographic recording medium according to an embodiment of the present invention can improve manufacturing efficiency and productivity by adopting a polymer matrix that can be rapidly crosslinked even at room temperature as a support.

[0027] The polymer matrix can increase the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer through the flexible main chain of the siloxane polymer. In addition, the siloxane bond, which has excellent heat resistance and humidity and heat resistance, can easily ensure the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium including 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. And, 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 the present specification, the "refractive index" may be a value measured by an Abbe refractometer at 25°C.

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

[0030] The siloxane-based polymer may, for example, include a repeating unit represented by the following Chemical Formula 2 and an end group represented by the following Chemical Formula 3: [ka] In the formula 2, multiple R 11 and R 12 are the same or different and each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms, k is an integer from 1 to 10,000.

[0031] [ka] In formula 3, multiple R 13 ~R 15 are the same or different and each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms, At least one repeating unit among the repeating units represented by Chemical Formula 2 and any one terminal group among the terminal groups represented by Chemical Formula 3, R 11 ~R 15 At least one of is hydrogen.

[0032] In Chemical Formula 3, -(O)- means that when the Si of the terminal group represented by Chemical Formula 3 is bonded to the repeating unit represented by Chemical Formula 2, the bond is via oxygen (O) or is directly bonded without oxygen (O).

[0033] As used herein, an "alkyl group" may be a straight-chain, branched-chain or cyclic alkyl group. As a non-limiting example, an "alkyl group" as used herein may be methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethyl-propyl, 1-ethyl-propyl, 1-methyl-butyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methylpentyl, 1 ... pentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethyl-butyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), and the like.

[0034] As an example, R in Chemical Formula 2 and Chemical Formula 3 11 ~R 15 is methyl or hydrogen, and multiple R 11 ~R 15 At least two of the R in the formula 2 may be hydrogen. 11 and R 12 are methyl and hydrogen, respectively, and R in formula 3 13 ~R 15 are each independently methyl or hydrogen (e.g., polymethylhydrosiloxanes whose terminal groups are 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 formula 3 13 ~R 15are 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 formula 3 13 ~R 15 and the remaining 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) in the range of 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 the siloxane-based polymer volatilizing during the crosslinking process with the (meth)acrylic polyol performed at room temperature or higher, resulting in a decrease in the degree of matrix crosslinking, or the siloxane-based polymer being poorly compatible with other components of the photopolymer composition and phase separation occurring with such components, can be prevented, thereby allowing the holographic recording medium 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 means the number average molecular weight (unit: g / mol) in terms of polystyrene measured by GPC (Gel Permeation Chromatography). In the process of measuring the number average molecular weight in terms of polystyrene measured by GPC, a commonly known analytical device, a detector such as a refractive index detector, and an analytical column can be used, and commonly applied temperature conditions, solvents, and flow rates can be applied. Specific examples of measurement conditions include a temperature of 25°C, a tetrahydrofuran solvent, and a flow rate of 1 mL / min.

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

[0038] The (meth)acrylic polyol may be a homopolymer of a (meth)acrylate monomer having a hydroxy group, a copolymer of a (meth)acrylate monomer having two or more kinds of hydroxy groups, 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" is a term that 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 means a weight average molecular weight in terms of polystyrene measured by the GPC method as described above. For example, the lower limit of the weight average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, for example, 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less, or 450,000 or less. When the weight average molecular weight of the (meth)acrylic polyol satisfies the above-mentioned range, the polymer matrix can fully exhibit the function of a support, and the deterioration of the recording properties for optical information is small even after the passage of time in use, and sufficient flexibility is imparted to the polymer matrix, thereby improving the mobility of the components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer composition, thereby minimizing the deterioration of the recording properties for optical information.

[0041] In order to adjust the crosslinking density of the (meth)acrylic polyol by 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 group (-OH) equivalent of the (meth)acrylic polyol may be, for example, within the range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl group (-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 group (-OH) equivalent of the (meth)acrylic polyol may be 2900g / equivalent or less, 2800g / equivalent or less, 2700g / equivalent or less, 2600g / equivalent or less, 2500g / equivalent or less, 2400g / equivalent or less, 2300g / equivalent or less, 2200g / equivalent or less, 2100g / equivalent or less, 2000g / equivalent or less, or 1900g / equivalent or less. The hydroxyl group (-OH) equivalent of the (meth)acrylic polyol is the equivalent (g / equivalent) to one hydroxy functional group, and is the value obtained 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 value, the higher the density of the functional group, and the larger the equivalent value, the lower the density of the functional group. When the hydroxyl group (-OH) equivalent of the (meth)acrylic polyol satisfies the above-mentioned range, the polymer matrix has an appropriate crosslink density and fully functions as a support, and the fluidity of the components contained in the photopolymer layer is improved, so that the boundary surface of the diffraction grating generated after recording does not collapse, and the initial refractive index modulation value is maintained at an excellent level even over time, minimizing the deterioration of recording characteristics for optical information.

[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 more, -50°C or more, -45°C or more, -40°C or more, -35°C or more, -30°C or more, or -25°C or more, and the upper limit may be, for example, -15°C or less, -20°C or less, -25°C or less, -30°C or less, or -35°C or less. When the above-mentioned glass transition temperature range is satisfied, the glass transition temperature can be lowered without significantly decreasing 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 a known method, for example, a method 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 in 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 the production of the (meth)acrylic polyol (values ​​measured using an Abbe refractometer at 25°C) and the fraction (molar ratio) of each monomer.

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

[0046] The Pt-based catalyst may be, for example, Karstedt's catalyst, etc. The precursor of the polymer matrix 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 acids-based, or carbene-based nonmetallic catalyst, etc., as necessary.

[0047] Meanwhile, the photoreactive monomer may include a compound having a higher refractive index than the polymer matrix in order to realize the above-mentioned refractive index modulation. However, it is not limited that all the photoreactive monomers included in the photopolymer layer have a higher refractive index than the polymer matrix, and at least a part of the photoreactive monomers may have a higher refractive index than the polymer matrix in order to realize a high refractive index modulation value. As an 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-phenyl acrylate, 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), phenol (ethylene oxide) 2 (meth)acrylate (phenoxybenzyl (meth)acrylate, M1122 having a refractive index of 1.565, Miwon), The colorant may include at least one selected from the group consisting of EO2 (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.

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

[0051] The photopolymer layer may contain 50 to 300 parts by weight of the photoreactive monomer relative to 100 parts by weight of the polymer matrix. For example, the lower limit of the content of the photoreactive monomer may be 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or 90 parts by weight or more, and the upper limit may be 300 parts by weight or less, 280 parts by weight or less, 250 parts by weight or less, 220 parts by weight or less, 200 parts by weight or less, 190 parts by weight or less, or 180 parts by weight or less. When the above range is satisfied, it is advantageous to ensure excellent optical recording properties and durability in high temperature / high humidity environments.

[0052] In the present specification, the content of the polymer matrix means the combined content (weight) of the (meth)acrylic polyol and the siloxane polymer forming the matrix. In other words, the content of the polymer matrix means the content including the content of the polymer matrix formed by crosslinking the (meth)acrylic polyol and the siloxane polymer, and the content of the polymer matrix precursor that is not partially crosslinked.

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

[0054] The photopolymer layer may include a photosensitizer and a coinitiator as a photoinitiator system.

[0055] As the photosensitizer, for example, a photosensitive dye can be used. Specifically, examples of the light-sensitive dye include silicon rhodamine compounds, sulfonium derivatives of ceramidonine, 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, crystal violet, and the like. One or more selected from the group consisting of Cyanine, Methylene Blue, Azure A, and BODIPY may be used.

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

[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 may be, for example, 0.05 parts by weight or more, 0.07 parts by weight or more, or 0.10 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above-mentioned range is satisfied, it is advantageous to show an appropriate polymerization reaction speed and ensure 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, for example, a borate anion represented by the following formula 4:

[0060] BX 1 X 2 X 3 X 4 (Chemical formula 4) In chemical formula 4, 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, and 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 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, each of which may be substituted or unsubstituted by halogen; 4 may be n-butyl, n-pentyl or n-hexyl. More specifically, the borate anion represented by Chemical Formula 4 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 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, etc.).

[0064] As the electron donor, for example, commercially available butyryl choline triphenylbutylborate (Borate V, 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 an onium salt, such as, for example, a sulfonium salt, an iodonium salt, or a mixture thereof.

[0066] By way of example, the electron acceptor may include an iodonium salt, for example, commercially available H-Nu254 (Spectra Group).

[0067] The photopolymer layer may contain 0.05 to 10 parts by weight of the coinitiator relative to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the coinitiator may be, for example, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, or 0.5 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above-mentioned range is satisfied, it is advantageous to show an appropriate polymerization reaction speed and ensure the desired optical recording characteristics.

[0068] The photoinitiator system may contain an additional photoinitiator to remove the color of the photosensitive dye and to react all of the unreacted photoreactive monomers after irradiation with light for recording. Examples of the photoinitiator include 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, (η6-benzene)(η5-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: Irgacure184 / Manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (Product name: Irgacure369 / Manufacturer: BASF), Bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium (Product name: Irgacure784 / 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 realizes easier 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, and has a low refractive index and non-reactive properties, is uniformly distributed in the polymer matrix, and when the non-photopolymerized photoreactive monomer moves, the plasticizer moves in the opposite direction to the movement of the non-photopolymerized photoreactive monomer, thereby contributing to refractive index modulation. 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 in order to perform the function of the plasticizer described above. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 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. Since a fluorine-based compound having a refractive index lower than that of the above-mentioned photoreactive monomer is used, 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 1, which not only provides excellent optical recording properties but also provides a holographic recording medium with excellent reliability and highly transparent optical properties even in high temperature / high humidity environments. [ka]

[0073] In chemical formula 1, Z 1 and Z 2 are each independently -O-, -S- or -NH-; R 1 ~R 4 any 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 1 ~R 4are not fluorine-containing substituents, each independently represents 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- of the substituents is substituted with -O-, -S- or -NH-.

[0074] More specifically, the fluorine-based compound represented by Chemical Formula 1 exhibits a sufficiently low refractive index, thereby increasing the refractive index modulation with the photoreactive monomer, and can fully play the role of a basic plasticizer that improves the diffusivity of components in the photopolymer composition. In addition, the fluorine-based compound represented by Chemical Formula 1 has low migration to the surface of the photopolymer layer even in high temperature and high humidity environments, is resistant to heat and moisture, and is less likely to decompose even under high temperature / high humidity conditions, thereby improving the reliability in high temperature / high humidity environments. In addition, the fluorine-based compound represented by Chemical Formula 1 exhibits excellent compatibility with components having a high refractive index, and ensures high transparency optical properties due to its excellent resistance to moisture and heat.

[0075] In chemical formula 1, R 1 ~R 4 At least one of R is a fluorine-containing substituent. 1 may be a fluorine-containing substituent.

[0076] 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.

[0077] Specifically, the fluorine-containing substituent may be a linear alkyl group having 1 to 20 carbon atoms and substituted with two or more fluorines, a cycloalkyl group having 3 to 12 carbon atoms and substituted with two or more fluorines, or an aryl group having 6 to 14 carbon atoms and substituted with two or more fluorines.

[0078] More specifically, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) b CF3, a decafluorocyclohexyl group, or a pentafluorophenyl group, where a is an integer of 0 to 3, an integer of 0 to 2, or an integer of 0 to 1, and b is an integer of 0 to 19, an integer of 0 to 15, an integer of 0 to 14, an integer of 0 to 13, an integer of 0 to 12, or an integer of 0 to 11.

[0079] As an example, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) b In the case of CF3 or a decafluorocyclohexyl group, it is possible to provide a holographic recording medium having low haze while contributing to a large refractive index modulation.

[0080] In chemical formula 1, R 1 ~R 4 is not a fluorine-containing substituent, R 1 ~R 4 may each independently be an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or may be a substituent in which one or more -CH2- of the substituents is replaced with -O-, -S- or -NH-.

[0081] Specifically, in Chemical Formula 1, R 1 ~R 4 is not a fluorine-containing substituent, R 1 ~R 4each independently represents a linear alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heteroaryl group having 4 to 12 carbon atoms, an arylalkyl group having 7 to 16 carbon atoms, or -(R 5 -Y 1 ) c -R 6 -(R 5 -Y 1 ) c -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, R 6 is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms; Y 1 is -O- or -S-, c may be an integer of 1 to 12, and when c is 2 or more, R 5 may be the same or different from each other.

[0082] More specifically, in Chemical Formula 1, R 1 ~R 4 is not a fluorine-containing substituent, R 1 ~R 4 are each independently an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a phenyl group, a benzyl group, a pyridinyl group, a pyrimidinyl group, a methoxymethyl group, a methoxyethyl group, a methylmercaptoethyl group, a methylaminoethyl group, -(CH2CH2O) c1 CH3, -CH2O(CH2CH2O) c2 It may be CH3, a cyclohexyloxyethyl group, a cyclohexylmercaptoethyl group, or a phenyloxyethyl group, where c1 is an integer from 1 to 5, and c2 is an integer from 1 to 4.

[0083] The fluorine-based compound represented by Chemical Formula 1 can include one or more fluorine-based compounds selected from the group consisting of fluorine-based compounds represented by the following Chemical Formulas 1-1 to 1-9. [ka]

[0084] In chemical formula 1-1, Z a1 and Z b1 are each independently -O-, -S- or -NH-; R a1 and R b1 are each independently CF3 or CHF2; R c1 and R c2 are each independently an alkylene group having 1 to 6 carbon atoms, Y a1 and Y a2 are each independently -CH2-, -O-, -S- or -NH-; R d1 and R d2 each independently represents an alkylene group having 1 to 4 carbon atoms, R e1 and R e2 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p1 and p2 each independently represent an integer of 0 to 9, and q1 and q2 each independently represent an integer of 0 to 3. [ka]

[0085] In chemical formula 1-2, Z a2 and Z b2 are each independently -O-, -S- or -NH-; R a2 is CF3 or CHF2, R c3 ~R c5 are each independently an alkylene group having 1 to 6 carbon atoms, Y a3 ~Y a5 are each independently -CH2-, -O-, -S- or -NH-; R d3~R d5 each independently represents an alkylene group having 1 to 4 carbon atoms, R e3 ~R e5 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p3 is an integer of 0 to 9; q3 to q5 are each independently an integer of 0 to 3. [ka]

[0086] In chemical formula 1-3, Z a3 and Z b3 are each independently -O-, -S- or -NH-; R a3 , R b2 and R b3 are each independently CF3 or CHF2; R c6 is an alkylene group having 1 to 6 carbon atoms, Y a6 is -CH2-, -O-, -S- or -NH-, R d6 is an alkylene group having 1 to 4 carbon atoms, R e6 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, R f1 and R f2 are each independently hydrogen or fluorine; p4 to p6 each independently represent an integer of 0 to 9; q6 represents an integer of 0 to 3. [ka]

[0087] In chemical formula 1-4, Z a4 and Z b4 are each independently -O-, -S- or -NH-; R a4, R a5 , R b4 and R b5 are each independently CF3 or CHF2; R f3 ~R f6 are each independently hydrogen or fluorine; p7 to p10 each independently represent an integer of 0 to 9. [ka]

[0088] In chemical formula 1-5, Z a5 and Z b5 are each independently -O-, -S- or -NH-; R a6 and R a7 are each independently CF3 or CHF2; R c7 and R c8 are each independently an alkylene group having 1 to 6 carbon atoms, Y a7 and Y a8 are each independently -CH2-, -O-, -S- or -NH-; R d7 and R d8 each independently represents an alkylene group having 1 to 4 carbon atoms, R e7 and R e8 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p11 and p12 each independently represent an integer of 0 to 9; q7 and q8 each independently represent an integer of 0 to 3. [ka]

[0089] In chemical formula 1-6, Z a6 and Z b6are each independently -O-, -S- or -NH-; R a8 ~R a10 are each independently CF3 or CHF2; R c9 is an alkylene group having 1 to 6 carbon atoms, Y a9 is -CH2-, -O-, -S- or -NH-, R d9 is an alkylene group having 1 to 4 carbon atoms, R e9 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p13 to p15 each independently represent an integer of 0 to 9; q9 represents an integer of 0 to 3. [ka]

[0090] In chemical formula 1-7, Z a7 and Z b7 are each independently -O-, -S- or -NH-; R b9 , R c10 and R d10 are each independently a decafluorocyclohexyl group, a phenyl group, a pyridinyl group, a pyrimidinyl group, or a methoxyethyl group. [ka]

[0091] In chemical formula 1-8, Z a8 and Z b8 are each independently -O-, -S- or -NH-; R b10 , R c11 and R d11 are each independently 2,2,3,3,4,4,5,5-oxafluoro-1-pentyl, decafluorocyclohexyl, phenyl, or methoxyethyl. [ka]

[0092] In chemical formula 1-9, Z a9 and Z b9 are each independently -O-, -S- or -NH-; R a11 and R b11 are each independently CF3 or CHF2; R c12 and R d12 are each independently a phenyl group or a benzyl group; p16 and p17 each independently represent an integer of 0 to 9.

[0093] The photopolymer layer may contain 20 to 200 parts by weight of a fluorine-based compound relative to 100 parts by weight of a polymer matrix. Specifically, the lower limit of the content of the fluorine-based compound may be, for example, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, 50 parts by weight or more, or 55 parts by weight or more, and the upper limit may be, for example, 200 parts by weight or less, 180 parts by weight or less, 150 parts by weight or less, 120 parts by weight or less, or 100 parts by weight or less. When the above-mentioned range is satisfied, it is possible to show a large refractive index modulation value after recording by a fluorine-based compound having a sufficiently low refractive index without problems such as poor compatibility with the components contained in the photopolymer layer, some of the fluorine-based compound dissolving on the surface of the photopolymer layer, or poor haze, which is advantageous for ensuring excellent optical recording characteristics.

[0094] The photopolymer layer may additionally contain additives such as antifoaming agents.

[0095] The photopolymer layer may contain a silicone-based reactive additive as an antifoaming agent, such as a commercially available product such as Tego Rad 2500.

[0096] The content of the additive, for example, the defoaming agent, can be appropriately adjusted to a level that does not impair the function of the holographic recording medium.

[0097] The photopolymer layer may be formed from a solvent-containing photopolymer composition.

[0098] 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.

[0099] The organic solvent may be added when the components to be contained in the photopolymer composition are mixed, or may be included in the photopolymer composition while the components are being added in a dispersed or mixed state in the organic solvent.

[0100] The photopolymer composition may contain a solvent so that the solid content concentration is 1 to 90% by weight. Specifically, the photopolymer composition may contain a solvent so that the solid content concentration is 20% by weight or more, 30% by weight or more, 50% by weight or more, or 60% by weight or more, and 85% by weight or less, 80% by weight or less, 75% by weight or less, or 70% by weight or less. Within these ranges, the photopolymer composition exhibits appropriate flowability, can form a coating film without defects such as stripes, and can form a photopolymer layer exhibiting desired physical properties and surface characteristics without defects during the drying and curing process.

[0101] The holographic recording medium of one embodiment includes the above-mentioned photopolymer layer, and thus can exhibit excellent reliability even in high temperature / high humidity environments.

[0102] Specifically, in one embodiment of the holographic recording medium, the peak change calculated by the following formula 3 is 3% or less. Peak change = {|1-A1 / A0|} x 100 (Equation 3)

[0103] In Equation 3, A0 is the wavelength of minimum transmittance of the holographic recording medium in the wavelength range of 300 to 1,200 nm, and A1 is the wavelength of minimum transmittance measured after exposing the holographic recording medium to conditions of a temperature of 60°C and a relative humidity of 90% for 72 hours.

[0104] The peak change describes the degree of shift of the wavelength showing the minimum transmittance before and after high temperature / high humidity conditions. For example, if a hologram grating (e.g., a reflection type hologram) is recorded to reflect light of a specific wavelength of 680 nm, the transmittance has a minimum value at 680 nm. If the transmittance is measured again after exposure to high temperature / high humidity conditions, the minimum transmittance may appear at 675 nm. In this case, according to the above formula 1, it is considered that there is a peak change of less than 1%. As such, as the interval of the diffraction grating decreases (i.e., the diffraction grating shrinks) depending on the conditions under which the hologram grating is driven or stored, a peak change occurs in which the minimum transmittance wavelength moves to a shorter wavelength. Conversely, if the interval of the hologram diffraction grating increases (diffraction grating expansion), a peak change may occur in which the minimum transmittance wavelength moves to a longer wavelength. The degree of such a peak change varies depending on the reliability of the diffraction grating.

[0105] 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 / high humidity. Such a holographic recording medium can provide good color reproducibility and image clarity even when exposed to harsh conditions.

[0106] The peak change for the holographic recording medium of an 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.

[0107] The holographic recording medium of the embodiment has high durability against heat and humidity, and can exhibit high adhesive strength even after aging in a high temperature / high humidity environment. Specifically, the holographic recording medium of the embodiment has an adhesive strength of 500 gf / 2.5 cm or more measured at a peel angle of 180° and a peel speed of 5 mm / sec after storing the holographic recording medium at a temperature of 60° C. and a relative humidity of 90% for 72 hours in a state where an optically transparent adhesive layer is laminated on a photopolymer layer.

[0108] The type of the optically transparent adhesive layer is not particularly limited, and may be, for example, a rubber-based adhesive layer, an acrylic-based adhesive layer, or a silicone-based adhesive layer. The holographic recording medium of the embodiment is not limited to exhibiting excellent adhesive strength with respect to all types of adhesive layers. However, the holographic recording medium of the embodiment can exhibit excellent adhesive strength with respect to various types of adhesive layers.

[0109] The lower limit of the adhesive strength may be, for example, 530gf / 2.5cm or more, 550gf / 2.5cm, 600gf / 2.5cm or more, 700gf / 2.5cm or more, 800gf / 2.5cm or more, 850gf / 2.5cm or more, 900gf / 2.5cm or more, 950gf / 2.5cm or more, 1000gf / 2.5cm or more, 1020gf / 2.5cm or more, 1050gf / 2.5cm or more, or 1100gf / 2.5cm or more. The method for measuring the adhesive strength may refer to the method described in the test examples described later. The upper limit of the adhesive strength is not particularly limited, and may be 2500gf / 2.5cm or less.

[0110] The holographic recording medium of one embodiment has a photopolymer layer with a small thickness, yet has excellent refractive index modulation, diffraction efficiency, and driving reliability.

[0111] 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. And 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.

[0112] The holographic recording medium of the embodiment may further include a substrate on at least one side of the photopolymer layer. The type of substrate is not particularly limited, and any substrate 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.

[0113] The holographic recording medium of the embodiment may have high diffraction efficiency. As an example, the holographic recording medium may have a diffraction efficiency of 70% or more when a notch filter hologram is recorded. In this case, the thickness of the photopolymer layer may be, for example, 5 to 30 μm. Specifically, when a notch filter hologram is recorded, the diffraction efficiency may be 75% or more, 80% or more, 85% or more, 86% or more, 87% or more, or 88% or more. In this way, the holographic recording medium of the other embodiment may achieve excellent diffraction efficiency even if it includes a thin photopolymer layer. The diffraction efficiency may be measured by a method described in the test example described later.

[0114] In one embodiment, the holographic recording medium can realize 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 if the thickness of the photopolymer layer is as thin as 5 to 30 μm. The upper limit of the refractive index modulation value is not particularly limited, but may be, for example, 0.060 or less. The refractive index modulation value can be measured by the method described in the test example described later.

[0115] On the other hand, since a holographic recording medium uses a mixture of a component having a low refractive index and a component having a high refractive index for recording optical characteristics, the holographic recording medium tends to have opaque characteristics due to the compatibility between the components. However, the holographic recording medium of one embodiment uses a fluorine-based compound having a specific structure with excellent compatibility, thereby exhibiting highly transparent optical characteristics.

[0116] As an example, the haze of the holographic recording medium may be 2% or less. The upper limit of the haze may be, for example, 1.7% or less, 1.6% or less, 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 example below.

[0117] The holographic recording medium of one embodiment is expected to exhibit not only excellent optical recording characteristics and excellent durability in high temperature / high humidity environments, but also highly transparent optical characteristics, thereby providing a variety of optical elements that can be used in environments where high heat is generated or humidity is high.

[0118] The holographic recording medium of the embodiment is not limited to this, but may be one in which a reflection type hologram or a transmission type hologram is recorded.

[0119] As an example, the diffraction grating of the photopolymer layer may be a reflection type hologram grating. In the case of a transmission type hologram grating, since the diffraction grating is formed in a direction perpendicular to the plane of the substrate, the linear expansion coefficient of the substrate and the linear expansion coefficient of the photopolymer have a greater effect on the deformation of the grating. In contrast, since the reflection type hologram grating is formed in a direction parallel to the plane of the substrate, the expansion or contraction of the volume type hologram grating formed inside the photopolymer has a greater effect on the clarity of the image than the mismatch between the linear expansion coefficient of the substrate and the diffraction grating. As a result, a hologram recording medium having such peak change characteristics is more suitable for a reflection type hologram.

[0120] For example, the diffraction grating of the photopolymer layer may be formed in a direction parallel or horizontal to the bottom surface on which the substrate is placed. In this case, parallel or horizontal means substantially parallel or horizontal, and may mean that the fringe angle of the diffraction grating with respect to the bottom surface on which the substrate is placed is parallel or horizontal within an error range of ±5°, ±4°, ±3°, ±2°, or ±1°.

[0121] The holographic recording medium may have a notch filter structure in relation to the diffraction grating structure. The notch filter structure of the holographic recording medium of the embodiment may mean that the diffraction grating is non-slanted (substantially 0°) with respect to the substrate surface, for example, so that the diffraction grating is parallel to the substrate surface. Such a holographic recording medium may have a structure in which two layers having 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 predetermined thicknesses. Such a non-slanted diffraction grating record may be manufactured by making the angles of incidence of the object light and the reference light, which are respectively incident, the same with respect to the normal line. In the non-slanted structure, the degree of deformation (e.g., contraction or expansion) under high temperature / high humidity conditions is more clearly confirmed than in the slanted structure, and the non-slanted structure is less affected by the contraction and expansion of the substrate.

[0122] The application of the holographic recording medium according to the 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, parts of wearable displays, or parts for automobiles (e.g., head-up displays).

[0123] Meanwhile, in one embodiment, a holographic recording medium can be manufactured by forming a photopolymer layer by applying a photopolymer composition, and then irradiating a coherent laser onto a predetermined region of the thus-manufactured unrecorded photopolymer layer to selectively polymerize the photoreactive monomers contained in the photopolymer layer, thereby recording optical information, so that the holographic recording medium can be manufactured in a form in which optical information is recorded.

[0124] In the step of forming the photopolymer layer, a photopolymer composition having the above-mentioned structure can be produced first. When producing the photopolymer composition, a generally known mixer, stirrer, mixer, etc. can be used to mix each component without any limitation. Such a mixing process may be performed at a temperature in the range of 0°C to 100°C, a temperature in the range of 10°C to 80°C, or a temperature in the range of 20°C to 60°C.

[0125] In the step of forming the photopolymer layer, the prepared photopolymer composition may be applied to form a coating film formed from the photopolymer composition. The coating film may be naturally dried at room temperature or may be dried at a temperature in the range of 30 to 80° C. This process may induce a hydrosilylation reaction between the hydroxyl group of the (meth)acrylic polyol remaining unreacted and the silane functional group of the siloxane polymer.

[0126] 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 additives added as needed uniformly dispersed within a crosslinked polymer matrix.

[0127] 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, and photoreactive monomer exists. The unreacted photoreactive monomer diffuses to the photopolymer side where the concentration of the photoreactive monomer is low, causing refractive index modulation, and a diffraction grating is generated by the refractive index modulation. As a result, a hologram, i.e., optical information, is recorded in the photopolymer layer having the diffraction grating.

[0128] 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 is recorded.

[0129] 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, and the color of the photosensitive dye can be removed.

[0130] 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 including a fluorine-based compound represented by the following Chemical Formula 1: [ka]

[0131] In chemical formula 1, Z 1 and Z 2 are each independently -O-, -S- or -NH-; R 1 ~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 1 ~R 4are not fluorine-containing substituents, each independently represents 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- of the substituents is replaced by -O-, -S- or -NH-.

[0132] The holographic recording medium according to another embodiment includes a fluorine-based compound having a specific structure as a plasticizer, thereby exhibiting improved optical recording characteristics, and also exhibiting optical characteristics of high reliability and high transparency even in high temperature / high humidity environments.

[0133] Holographic recording media according to other embodiments may exhibit high reliability even in high temperature / high humidity environments, for example, by having a peak change calculated by Equation 3 above of 3% or less, and by laminating an optically transparent adhesive layer onto a photopolymer layer, storing the layer at a temperature of 60° C. and a relative humidity of 90%, and then having an adhesive strength of 500 gf / 2.5 cm or more measured under conditions of a peel angle of 180° and a peel speed of 5 mm / sec, but this is not limited thereto.

[0134] 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 1 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 one 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 1 have been described in detail above, so a detailed description thereof will be omitted here.

[0135] Meanwhile, according to still another embodiment of the present invention, there is provided an optical element including a holographic recording medium.

[0136] 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, holographic optical elements having the functions of optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffraction members, light guides, waveguides, projection screens and / or masks, media and light diffusers in optical memory systems, optical wavelength splitters, reflective and transmissive color filters, etc.

[0137] An example of an optical element 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.

[0138] Specifically, the light source unit is a part that irradiates a laser beam that is used to provide, record, and reproduce three-dimensional image information of an object in the input unit and display unit.

[0139] 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 possible to input 3D information of an object such as spatial light intensity and phase to an electrically addressed liquid crystal SLM (Spatial Light Modulator), and at this time, it is a part that can use the input beam.

[0140] 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 erase beam, a read beam, etc. sent to the display section.

[0141] The display unit receives 3D image information of an object from the input unit, records it on a hologram plate made of an optically addressed SLM, and can reproduce a 3D image of the object. At this time, the 3D image information of the object can be recorded by interference between the input beam and the reference beam. The 3D image information of the object recorded on the hologram plate can be reproduced 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 reproduced. Effect of the Invention

[0142] The holographic recording medium according to an embodiment of the present invention not only has excellent optical recording characteristics, but also exhibits transparent optical characteristics and excellent reliability even in high temperature and high humidity environments. [Brief description of the drawings]

[0143] [Figure 1] This is a schematic diagram of the setup of a recording device for holographic recording. Specifically, the process is shown in which a laser of a certain wavelength is emitted from a light source 10, and then the light passes through mirrors 20, 20', an iris 30, a spatial filter 40, an iris 30', a collimation lens 50, and a polarized beam splitter (PBS) 60, and is then irradiated onto a PP (holographic recording medium) 80 located on one side of a mirror 70. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0144] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, which are presented as examples of the present invention and are not intended to limit the scope of the invention in any way.

[0145] In the following Production Examples, Examples, Comparative Examples, and the like, the contents of raw materials and the like refer to the contents on a solid basis unless otherwise specified.

[0146] Production Example 1: Production of (meth)acrylic polyol In a 2L jacketed reactor, 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate were added and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60-70°C and stirring was continued for about 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added and stirring was continued for about 30 minutes. Then, 0.24g of AIBN (azobisisobutyronitrile) was added as a polymerization initiator and polymerization was continued for more than 4 hours at the reaction temperature until the content of residual acrylate was less than 1%, and a (meth)acrylate copolymer with hydroxyl groups located in the branched chain (weight average molecular weight about 300,000, OH equivalent about 1802g / equivalent) was produced.

[0147] 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: about 390, Si-H equivalent: about 103 g / equivalent) as a siloxane polymer and 11.12 g of the (meth)acrylic polyol produced in Production Example 1 were mixed first (SiH / OH molar ratio = 2.0).

[0148] 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 coinitiators, 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 about 30 minutes while blocking light. Then, a Karstedt (Pt) catalyst was added for matrix crosslinking to produce a photopolymer composition. [ka]

[0149] (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.

[0150] 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. A notch filter hologram with periodic refractive index modulation in the thickness direction can be recorded due to the interference between the incident light L and the light L' reflected by the mirror. 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 laminated periodically at a constant thickness.

[0151] Examples 2 to 9 and Comparative Examples 1 to 3: Production of photopolymer compositions and holographic recording media Photopolymer compositions and holographic recording media were produced therefrom in the same manner as in Example 1, except that the components and contents of the photopolymer compositions were changed as shown in Table 1 below.

[0152] [Table 1] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0153] Test example: Performance evaluation of holographic recording media (1) Diffraction efficiency The diffraction efficiency (η) was calculated by the following formula 1.

[0154] η(%)={P D / (P D +P T )}×100 (Equation 1) In Equation 1, η is the diffraction efficiency, P D is the power (mW / cm) of the diffracted beam from the sample after recording. 2 ), and P Tis the power of the beam transmitted through the sample after recording (mW / cm 2 ).

[0155] (2) Refractive index modulation value (Δn) The refractive index modulation value (Δn) was calculated from the following formula 2 and Bragg's equation.

number

[0156]

number

[0157] In the above formula, η is the reflectance diffraction efficiency (DE), d is the thickness of the photopolymer layer, λ is the wavelength of the incident light for recording (660 nm or 532 nm), θ is the 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, θ (incident angle) and φ (slant angle of the grating) are all 0° because the holograms were recorded using a notch filter method.

[0158] (3) Hayes The haze was measured using a HAZE METER (Murakami Color Research Laboratory, HM-150) in accordance with JIS K7136. The measuring light was incident on the side surface of the substrate of the holographic recording medium.

[0159] (4) Peak change First, the specific wavelength (or wavelength band) (A0) at which the sample with the recorded diffraction grating had the maximum reflectance (i.e., the minimum transmittance) was analyzed (analysis was performed at room temperature and in non-humid conditions). A UV-Vis (Ultra Violet-Visible) spectrometer was used for the analysis, and the analysis wavelength range was 300 to 1,200 nm.

[0160] Then, the same sample was stored for 72 hours under a temperature of 60°C and a relative humidity of 90%, and the wavelength (or wavelength band) (A1) with the maximum reflectance (minimum transmittance) was recorded in the same manner. The peak change, which is the degree of shift in the wavelength with the minimum transmittance before and after the evaluation, was measured using the following formula 3. At this time, it was assumed that deformation (e.g., shrinkage or expansion) of the sample does not affect the surface grating (pitch) and occurs only in the vertical direction of the sample surface. Peak change = {|1-A1 / A0|} x 100 (Equation 3)

[0161] (5) Adhesion strength after aging A rubber-based OCA (optically clear adhesive) tesa (registered trademark) 61563 (thickness 50 μm, TESA) was laminated on a glass substrate to form an adhesive layer, and then the photopolymer layer of the sample on which the diffraction grating was recorded was laminated so that it was in contact with the adhesive layer. The obtained sample was then cut to a width of 2.5 cm to prepare a sample in which the glass substrate, adhesive layer, photopolymer layer, and TAC base material were laminated in this order.

[0162] The prepared samples were stored at 60°C and 90% relative humidity for 72 hours, and then the adhesion between the photopolymer layer and the adhesive layer was measured using a texture analyzer. The peel angle and peel speed during adhesion measurement were 180° and 5mm / sec, respectively.

[0163] [Table 2]

[0164] Referring to Table 2, it can be seen that the holographic recording media manufactured in Examples 1 to 9 exhibit excellent diffraction efficiency, refractive index modulation value, and low haze, and have little change in the wavelength at which the maximum reflectance is exhibited even after exposure to a high temperature / high humidity environment, and exhibit high adhesive strength, thereby demonstrating excellent reliability in a high temperature / high humidity environment. In contrast, the holographic recording media manufactured in Comparative Example 2 was poor in optical recording characteristics, haze, and reliability in a high temperature / high humidity environment, and the holographic recording media manufactured in Comparative Examples 1 and 3 exhibited excellent optical recording characteristics but poor reliability in a high temperature / high humidity environment.

[0165] This confirms that the holographic recording medium according to an embodiment of the present invention exhibits excellent optical recording characteristics, excellent reliability even in high temperature / high humidity environments, and high transparency due to the inclusion of a fluorine-based compound having 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 including a fluorine-based compound, The peak change calculated by the following formula 3 is 3% or less, Peak change = {|1 - A １ / A ０ |}×100 (Formula 3) In the above formula 3, A ０ is the wavelength at which the holographic recording medium has the minimum transmittance in the wavelength range of 300 to 1,200 nm, A １ is the wavelength of the minimum transmittance measured after exposing the holographic recording medium to a temperature of 60° C. and a relative humidity of 90% for 72 hours, A holographic recording medium, comprising: an optically transparent adhesive layer laminated on the photopolymer layer; and after storing the laminate under conditions of a temperature of 60° C. and a relative humidity of 90% for 72 hours, the adhesive strength measured under conditions of a peel angle of 180° and a peel speed of 5 mm / sec is 500 gf / 2.5 cm or more.

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

5. The holographic recording medium of 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 4: BX １ X ２ X ３ X ４ (Chemical formula 4) In chemical formula 4, X １ ~X ４ each independently represents 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 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 1: 【Chemistry 3】 In chemical formula 1, Z １ and Z ２ are each independently —O—, —S—, or —NH—, R １ ~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 １ ~R ４ are not fluorine-containing substituents, each independently represents 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 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. In chemical formula 1, R １ The holographic recording medium according to claim 7 , wherein: is a fluorine-containing substituent.

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 fluorines, a cycloalkyl group having 3 to 12 carbon atoms and substituted with two or more fluorines, or an aryl group having 6 to 14 carbon atoms and substituted with two or more fluorines.

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

11. In chemical formula 1, R １ ~R ４ is not a fluorine-containing substituent, R １ ~R ４ are each independently a linear alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heteroaryl group having 4 to 12 carbon atoms, an arylalkyl group having 7 to 16 carbon atoms, or -(R ５ -Y １ ) ｃ -R ６ 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, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, Y １ is —O— or —S—, c is an integer from 1 to 12; When c is 2 or more, R ５ 8. The holographic recording medium according to claim 7, wherein: are the same or different from each other.

12. The fluorine-based compound represented by Chemical Formula 1 includes one or more fluorine-based compounds selected from the group consisting of fluorine-based compounds represented by the following Chemical Formulas 1-1 to 1-9: 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 In chemical formula 1-1, Z ａ１ and Z ｂ１ are each independently —O—, —S—, or —NH—, R ａ１ and R ｂ１ are each independently ３ or CHF ２ and R ｃ１ and R ｃ２ are each independently an alkylene group having 1 to 6 carbon atoms, Y ａ１ and Y ａ２ are each independently -CH ２ -, -O-, -S- or -NH-; R ｄ１ and R ｄ２ are each independently an alkylene group having 1 to 4 carbon atoms, R ｅ１ and R ｅ２ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group; p1 and p2 each independently represent an integer from 0 to 9; q1 and q2 each independently represent an integer of 0 to 3; In chemical formula 1-2, Z ａ２ and Z ｂ２ are each independently —O—, —S—, or —NH—, R ａ２ CF ３ or CHF ２ and R ｃ３ ~R ｃ５ are each independently an alkylene group having 1 to 6 carbon atoms, Y ａ３ ~Y ａ５ are each independently -CH ２ -, -O-, -S- or -NH-; R ｄ３ ~R ｄ５ are each independently an alkylene group having 1 to 4 carbon atoms, R ｅ３ ~R ｅ５ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group; p3 is an integer from 0 to 9, q3 to q5 each independently represent an integer of 0 to 3, In chemical formula 1-3, Z ａ３ and Z ｂ３ are each independently —O—, —S—, or —NH—, R ａ３ , R ｂ２ and R ｂ３ are each independently ３ or CHF ２ and R ｃ６ is an alkylene group having 1 to 6 carbon atoms, Y ａ６ is -CH ２ -, -O-, -S- or -NH-; R ｄ６ is an alkylene group having 1 to 4 carbon atoms, R ｅ６ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, R ｆ１ and R ｆ２ are each independently hydrogen or fluorine; p4 to p6 each independently represent an integer from 0 to 9, q6 is an integer from 0 to 3, In chemical formula 1-4, Z ａ４ and Z ｂ４ are each independently —O—, —S—, or —NH—, R ａ４ , R ａ５ , R ｂ４ and R ｂ５ are each independently ３ or CHF ２ and R ｆ３ ~R ｆ６ are each independently hydrogen or fluorine; p7 to p10 each independently represent an integer from 0 to 9; In chemical formula 1-5, Z ａ５ and Z ｂ５ are each independently —O—, —S—, or —NH—, R ａ６ and R ａ７ are each independently ３ or CHF ２ and R ｃ７ and R ｃ８ are each independently an alkylene group having 1 to 6 carbon atoms, Y ａ７ and Y ａ８ are each independently -CH ２ -, -O-, -S- or -NH-; R ｄ７ and R ｄ８ are each independently an alkylene group having 1 to 4 carbon atoms, R ｅ７ and R ｅ８ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group; p11 and p12 each independently represent an integer from 0 to 9; q7 and q8 each independently represent an integer of 0 to 3; In chemical formula 1-6, Z ａ６ and Z ｂ６ are each independently —O—, —S—, or —NH—, R ａ８ ~R ａ１０ are each independently ３ or CHF ２ and R ｃ９ is an alkylene group having 1 to 6 carbon atoms, Y ａ９ is -CH ２ -, -O-, -S- or -NH-; R ｄ９ is an alkylene group having 1 to 4 carbon atoms, R ｅ９ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p13 to p15 each independently represent an integer from 0 to 9; q9 is an integer from 0 to 3, In chemical formula 1-7, Z ａ７ and Z ｂ７ are each independently —O—, —S—, or —NH—, R ｂ９ , R ｃ１０ and R ｄ１０ are each independently a decafluorocyclohexyl group, a phenyl group, a pyridinyl group, a pyrimidinyl group, or a methoxyethyl group; In chemical formula 1-8, Z ａ８ and Z ｂ８ are each independently —O—, —S—, or —NH—, R ｂ１０ , R ｃ１１ and R ｄ１１ are each independently a 2,2,3,3,4,4,5,5-oxafluoro-1-pentyl group, a decafluorocyclohexyl group, a phenyl group, or a methoxyethyl group; In chemical formula 1-9, Z ａ９ and Z ｂ９ are each independently —O—, —S—, or —NH—, R ａ１１ and R ｂ１１ are each independently ３ or CHF ２ and R ｃ１２ and R ｄ１２ are each independently a phenyl group or a benzyl group; 3. The holographic recording medium according to claim 1, wherein p16 and p17 each independently represent an integer of 0 to 9.

13. 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.

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

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

16. 3. The holographic recording medium according to claim 1, wherein the haze of the holographic recording medium is 2% or less.

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

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