Hologram recording medium and optical element comprising same

Abstract

The present invention relates to a hologram recording medium and an optical element comprising same. The hologram recording medium not only has excellent optical recording properties, but can also exhibit excellent reliability and transparency even in a high-temperature environment.

Description

Holographic recording medium and optical element including the same

[0001] [Cross-reference with related application(s)]

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0022506, filed February 16, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present application relates to a holographic recording medium and an optical element including the same.

[0004] A holographic recording medium records information by changing the refractive index within the holographic recording layer through an exposure process, and reproduces the information by reading the difference in the recorded refractive index.

[0005] In this regard, the photopolymer composition can be used to manufacture a hologram. The photopolymer can easily store an optical interference pattern as a hologram by photopolymerization of a photoreactive monomer. Therefore, the photopolymer can be used in various fields, such as smart devices such as mobile devices, components of wearable displays, automotive products (e.g., head-up displays), holographic fingerprint recognition systems, holographic optical elements having the functions of optical lenses, mirrors, deflecting mirrors, filters, diffusion screens, diffractive elements, light guides, waveguides, projection screens, and / or masks, media for optical memory systems, optical diffusers, optical wavelength splitters, reflective and transmissive color filters, etc.

[0006] Specifically, a photopolymer composition for hologram production comprises a polymer matrix, a photoreactive monomer, and a photoinitiator system. Then, a photopolymer layer produced from this composition is irradiated with laser interference light to induce local photopolymerization of the monomer.

[0007] This local photopolymerization process creates a refractive index modulation, which in turn creates a diffraction grating. The refractive index modulation value (△n) is influenced by the thickness and diffraction efficiency (DE) of the photopolymer layer, and the angular selectivity broadens as the thickness decreases.

[0008] Recently, there has been an increasing demand for the development of materials that can maintain high diffraction efficiency and stable holograms, and various attempts are being made to manufacture holographic recording media that have a thin thickness but high diffraction efficiency and refractive index modulation value.

[0009] Meanwhile, when holographic recording media are used as optical elements in applications such as mobile devices or automotive components (e.g., head-up displays), they are subjected to high-temperature environments. In such cases, deformation of the diffraction grating can occur, distorting the image or preventing it from functioning as intended. Therefore, there is a need for the development of a highly reliable photopolymer layer and a holographic recording medium containing the same, with minimal deformation of the diffraction grating despite the heat of the environment in which it is used.

[0010] According to one embodiment of the present invention, a holographic recording medium is provided.

[0011] According to another embodiment of the present invention, an optical element including the holographic recording medium is provided.

[0012] Hereinafter, a holographic recording medium and an optical element including the same according to specific embodiments of the invention will be described.

[0013] As used herein, “hologram recording medium” means a medium or media capable of recording optical information in the entire visible light range and ultraviolet range (e.g., 300 to 1,200 nm) through an exposure process, unless specifically stated otherwise. Therefore, the hologram recording medium in this specification may mean a medium on which optical information is recorded, or may mean a pre-recording medium capable of recording optical information. The hologram in this specification may include any visual hologram, such as an in-line (Gabor) hologram, an off-axis hologram, a full-aperture pre-hologram, a white-light transmission hologram (“rainbow hologram”), a Denisyuk hologram, a biaxial reflection hologram, an edge-literature hologram, or a holographic stereogram.

[0014] In this specification, with respect to environmental conditions in which a holographic recording medium or a device including the same is placed, “high temperature” may mean a temperature of 60°C or higher. For example, the 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 thereof is not particularly limited, but 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, object, or each component, unless specifically mentioned otherwise, the temperature conditions under which the characteristics are measured or described may mean room temperature (e.g., a temperature at which no special cooling or heating is performed, in the range of about 15 to 30°C).

[0015] In this specification, unless specifically stated otherwise, the measurement values ​​may be understood as measurement values ​​of a photopolymer layer included in a holographic recording medium.

[0016] According to one embodiment of the invention, a hologram recording medium is provided, which comprises a polymer matrix or a precursor thereof formed by cross-linking a siloxane-based polymer and an acrylic polyol containing a silane functional group; a photopolymer layer containing a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a fluorine-based compound, wherein P80, which is Pn measured at 80° C. through the following formula 1, is 0.10% or less.

[0017] [Formula 1]

[0018] Pn (%) = {A1 / (A1+A2)} * 100

[0019] In the above equation 1, Pn is the thickness ratio of the different refractive index layer formed at n ℃,

[0020] A1 is the thickness of the refractive index layer formed at n ℃, and the refractive index layer means a surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm.

[0021] A2 is the thickness of the remaining portion of the photopolymer layer excluding the refractive index layer.

[0022]

[0023] The present inventors have confirmed that a holographic recording medium exhibiting improved optical recording characteristics when including a specific photopolymer layer, while also exhibiting optical characteristics of high reliability and high transparency even at high temperatures, has been provided, and the present invention has been completed.

[0024]

[0025] Hereinafter, a holographic recording medium and an optical element including the holographic recording medium according to one embodiment of the present invention will be described in detail.

[0026] The holographic recording medium of the above embodiment comprises a polymer matrix or a precursor thereof formed by cross-linking a siloxane-based polymer containing a silane functional group and an acrylic polyol; a photopolymer obtained from a photoreactive monomer and a photoinitiator system; and a photopolymer layer containing a fluorine-based compound.

[0027] The above photopolymer layer may be a photopolymer layer in a state before recording that can record optical information, or a photopolymer layer in a state in which optical information is recorded.

[0028] A photopolymer layer having optical information recorded thereon can be manufactured by irradiating the photopolymer layer with object light and reference light before recording. When the photopolymer layer is irradiated with object light and reference light before recording, the photoinitiator system remains in an inactive state in the destructive interference region due to the interference fields of the object light and reference light, so photopolymerization of the photoreactive monomer does not occur, but photopolymerization of the photoreactive monomer occurs in the constructive interference region due to the activated photoinitiator system. In the constructive interference region, as the photoreactive monomer is continuously consumed, a concentration difference occurs between the photoreactive monomers in the destructive interference region and the constructive interference region. As a result, the photoreactive monomers in the destructive interference region diffuse into the constructive interference region. At this time, the fluorine-based compound, which is a plasticizer, moves in the opposite direction to the photoreactive monomers. Since the photoreactive monomer and the photopolymer formed therefrom have a high refractive index compared to the polymer matrix and the fluorine-based compound, a spatial refractive index change occurs in the photopolymer layer, and a grating is created due to the spatial refractive index modulation occurring in the photopolymer layer. This grating surface acts as a reflective surface that reflects incident light due to the difference in refractive index, and when light of the wavelength at the time of recording is incident in the direction of the reference light after recording a hologram, the Bragg condition is satisfied, so that the light is diffracted in the direction of the original object light, and the holographic optical information can be reproduced.

[0029] Accordingly, if the photopolymer layer is in a pre-recording state, the photopolymer layer may include a photoreactive monomer, a photoinitiator, and a fluorine-based compound in a randomly dispersed form within the polymer matrix or its precursor.

[0030] On the other hand, if optical information is recorded in the photopolymer layer, the photopolymer layer may include a photopolymer and a fluorine-based compound distributed so as to form a polymer matrix and a lattice.

[0031] The above photopolymer layer is formed from a photopolymer composition comprising a polymer matrix or a precursor thereof formed by cross-linking a siloxane-based polymer containing a silane functional group and an acrylic polyol; a photoreactive monomer and a photoinitiator; and a fluorine-based compound.

[0032] The polymer matrix serves as a support for the photopolymer layer, and is formed by crosslinking a siloxane-based polymer containing a silane functional group (Si-H) and an acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking an acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxyl group of the acrylic polyol can form a crosslinking bond through a hydrosilylation reaction with the silane functional group of the siloxane-based polymer. The hydrosilylation reaction can proceed rapidly even at room temperature (for example, a temperature in a range of about 15 to 30°C as a temperature in a heated or non-heated state) in the presence of a Pt-based catalyst. Therefore, the photopolymer composition of one embodiment can improve the manufacturing efficiency or productivity of a hologram recording medium by employing a polymer matrix that can be rapidly crosslinked even at room temperature as a support.

[0033] The polymer matrix described above can enhance the mobility of components (e.g., photoreactive monomers or plasticizers) included in the photopolymer layer due to the flexible main chain of the siloxane-based polymer. In addition, the siloxane bond, which has excellent heat and moisture resistance properties, can facilitate securing the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium including the same.

[0034] The polymer matrix may have a relatively low refractive index, thereby serving to increase 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, "refractive index" may be a value measured with an Abbe refractometer at 25°C.

[0035] The photopolymer layer may include the above-described cross-linked polymer matrix or a precursor thereof. When the photopolymer layer includes a precursor of the polymer matrix, it may include a siloxane-based polymer, an acrylic polyol, and a Pt-based catalyst.

[0036] The above siloxane polymer may include, for example, a repeating unit represented by the following chemical formula 1 and a terminal group represented by the following chemical formula 2.

[0037] [Chemical Formula 1]

[0038]

[0039] In the above chemical formula 1,

[0040] Multiple R's 11 and R 12are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,

[0041] k is an integer between 1 and 10,000,

[0042] [Chemical Formula 2]

[0043]

[0044] In the above chemical formula 2,

[0045] Multiple R's 13 Inland R 15 are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,

[0046] At least one repeating unit selected from among the repeating units represented by the above chemical formula 1 and R of one terminal group selected from among the terminal groups represented by the above chemical formula 2 11 Inland R 15 At least one of them is hydrogen.

[0047] In the above chemical formula 2, -(O)- means that when Si of the terminal group represented by the above chemical formula 2 is bonded to the repeating unit represented by the above chemical formula 1, it is bonded via oxygen (O) or directly without oxygen (O).

[0048] In this specification, “alkyl group” may be a straight-chain, branched-chain or cyclic alkyl group. By way of non-limiting example, the term “alkyl group” herein includes methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethyl-propyl, 1-ethyl-propyl, 1-methyl-butyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethyl-butyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), It can be octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), etc.

[0049] For example, R of the above chemical formulas 1 and 2 11 Inland R 15 is methyl or hydrogen, and plural R 11 Inland R 15 At least two of them may be hydrogen. More specifically, the siloxane polymer is R of the chemical formula 1. 11 and R 12 are methyl and hydrogen, respectively, and R of the above chemical formula 2 13 Inland R 15 A compound in which each independently represents methyl or hydrogen (e.g., polymethylhydrosiloxane in which the terminal group is a trimethylsilyl group or a dimethylhydrosilyl group); some R of the above formula 1 11 and R 12 are methyl and hydrogen respectively, and the remaining R 11 and R 12 All are methyl, and R in the above chemical formula 2 13 Inland R 15A compound in which each independently represents methyl or hydrogen (e.g., poly(dimethylsiloxane-co-methylhydrosiloxane) in which the terminal group is a trimethylsilyl group or a dimethylhydrosilyl group); or R of the above formula 1 11 and R 12 All are methyl, and R of the above chemical formula 2 13 Inland R 15 It may be a compound in which at least one of the terminal groups is hydrogen and the others are each independently methyl or hydrogen (e.g., polydimethylsiloxane in which one or both of the terminal groups are dimethylhydrosilyl groups).

[0050] The above siloxane compound may have, for example, a number average molecular weight (Mn) in the range of 200 to 4,000. Specifically, the lower limit of the number average molecular weight of the siloxane 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 above siloxane polymer satisfies the above range, problems such as a decrease in the degree of matrix crosslinking due to volatilization of the siloxane polymer during the crosslinking process with the acrylic polyol at room temperature or a higher temperature, or a phase separation occurring with the components of other photopolymer layers due to poor compatibility of the siloxane polymer with these components are prevented, thereby enabling the holographic recording medium to exhibit excellent optical recording characteristics and excellent durability under high-temperature conditions.

[0051] The above number average molecular weight refers to the number average molecular weight (unit: g / mol) converted to polystyrene as measured by the GPC method. In the process of measuring the number average molecular weight converted to polystyrene as measured by the GPC method, a commonly known analysis device and a detector such as a refractive index detector and an analysis column can be used, and commonly applied temperature conditions, solvents, and flow rates can be applied. Specific examples of the above measurement conditions include a temperature of 25°C, a tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0052] The above acrylic polyol may refer to a polymer having one or more, specifically two or more, hydroxyl groups bonded to the main chain or side chain of an acrylate polymer. In the present specification, "acrylic" refers to at least one selected from acryloyl groups, methacryloyl groups, and derivatives thereof, or a repeating unit formed by polymerization thereof, unless specifically stated otherwise, and "acrylate" refers to at least one selected from acrylates and methacrylates, or a repeating unit formed by polymerization thereof, unless specifically stated otherwise.

[0053] The above acrylic polyol may be a homopolymer of an acrylate monomer having a hydroxyl group, a copolymer of two or more acrylate monomers having hydroxyl groups, or a copolymer of an acrylate monomer having a hydroxyl group and an acrylate monomer not having a hydroxyl group. In this specification, “copolymer” is a term encompassing all random copolymers, block copolymers, and graft copolymers, unless specifically stated otherwise.

[0054] As the acrylate monomer having the above hydroxyl group, examples thereof include hydroxyalkyl (meth)acrylate or hydroxyaryl (meth)acrylate, and the like, wherein the alkyl is an alkyl having 1 to 30 carbon atoms, and the aryl may be an aryl having 6 to 30 carbon atoms. In addition, as the acrylate monomer not having the above hydroxyl group, examples thereof include alkyl (meth)acrylate or aryl (meth)acrylate, and the like, wherein the alkyl is an alkyl having 1 to 30 carbon atoms, and the aryl may be an aryl having 6 to 30 carbon atoms. In the present specification, “(meth)acrylate” is a term referring to acrylate and / or methacrylate, unless specifically stated otherwise.

[0055] The above-mentioned acrylic polyol may have, for example, a weight average molecular weight (Mw) within the range of 150,000 to 1,000,000. The weight average molecular weight refers to a weight average molecular weight in terms of polystyrene measured by the GPC method described above. For example, the lower limit of the weight average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, for example, 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less, or 450,000 or less. When the weight average molecular weight of the acrylic polyol satisfies the above range, the polymer matrix sufficiently functions as a support, so that even with the passage of time in use, the decrease in recording characteristics for optical information is small, and sufficient flexibility is provided to the polymer matrix to improve the mobility of components (e.g., photoreactive monomers or plasticizers) included in the photopolymer composition, thereby minimizing the decrease in recording characteristics for optical information.

[0056] In order to adjust the crosslinking density of the acrylic polyol by the siloxane polymer to a level advantageous for securing the function of the hologram recording medium, the hydroxyl equivalent of the acrylic polyol can be adjusted to an appropriate level.

[0057] Specifically, the hydroxyl group (-OH) equivalent of the acrylic polyol may be, for example, in the range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl group (-OH) equivalent of the acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. And, the upper limit of the hydroxyl group (-OH) equivalent of the acrylic polyol may be 2900 g / equivalent or less, 2800 g / equivalent or less, 2700 g / equivalent or less, 2600 g / equivalent or less, 2500 g / equivalent or less, 2400 g / equivalent or less, 2300 g / equivalent or less, 2200 g / equivalent or less, 2100 g / equivalent or less, 2000 g / equivalent or less, or 1900 g / equivalent or less. The hydroxyl group (-OH) equivalent of the acrylic polyol is the equivalent (g / equivalent) for one hydroxyl functional group, and is a value obtained by dividing the weight average molecular weight of the acrylic polyol by the number of hydroxyl functional groups per molecule. The smaller the equivalent value, the higher the density of the functional group, and the larger the equivalent value, the smaller the density of the functional group.When the hydroxyl group (-OH) equivalent of the above acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslinking density and sufficiently functions as a support, and the fluidity of the components included in the layer formed from the photopolymer composition is improved, so that the initial refractive index modulation value is maintained at an excellent level even after time passes without the problem of the boundary surface of the diffraction gratings generated after recording collapsing, thereby minimizing the decrease in recording characteristics for optical information.

[0058] The above acrylic polyol may have a glass transition temperature (Tg) in the range of, for example, -60 to -10°C. Specifically, the lower limit of the glass transition temperature may be, for example, -55°C or higher, -50°C or higher, -45°C or higher, -40°C or higher, -35°C or higher, -30°C or higher, or -25°C or higher, and the upper limit may be, for example, -15°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, or -35°C or lower. When the above glass transition temperature range is satisfied, the glass transition temperature may be lowered without significantly lowering the modulus of the polymer matrix, thereby increasing the mobility (fluidity) of other components in the photopolymer composition and also improving the moldability of the photopolymer composition. The above 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).

[0059] The refractive index of the acrylic polyol may be, for example, 1.40 or more and less than 1.50. Specifically, the lower limit of the refractive index of the acrylic polyol may be, for example, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more, and the upper limit may be, for example, 1.49 or less, 1.48 or less, 1.47 or less, 1.46 or less, or 1.45 or less. When the acrylic polyol has a refractive index in the above-described range, it may contribute to increasing refractive index modulation. The refractive index of the acrylic polyol is a theoretical refractive index and may be calculated using the refractive index of a monomer used in producing the acrylic polyol (a value measured using an Abbe refractometer at 25°C) and the fraction (mole ratio) of each monomer.

[0060] The above acrylic polyol and siloxane polymer may be used so that the molar ratio (SiH / OH) of the silane functional group (Si-H) of the siloxane polymer to the hydroxyl group (-OH) of the acrylic polyol is 0.80 to 3.5. That is, the type and content of the siloxane polymer and the acrylic polyol may be selected so as to satisfy the molar ratio when forming the polymer matrix. The lower limit of the molar ratio (SiH / OH) may be, for example, 0.81 or more, 0.85 or more, 0.90 or more, or 0.95 or more, and the upper limit may be, for example, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.05 or less, or 3.0 or less. When the above molar ratio (SiH / OH) range is satisfied, the polymer matrix is ​​crosslinked at an appropriate crosslinking density, thereby improving reliability under high temperature conditions and implementing a sufficient refractive index modulation value.

[0061] The above Pt series catalyst may be, for example, Karstedt's catalyst. The polymer matrix precursor may additionally include, in addition to the Pt series catalyst, a non-metal series catalyst such as a Rhodium series, an Iridium series, a Rhenium series, a Molybdenum series, an Iron series, a Nickel series, an alkali metal or alkaline earth metal series, a Lewis acid series, or a Carbene series, as needed.

[0062] Meanwhile, the photoreactive monomer may include a compound having a higher refractive index than the polymer matrix in order to implement the above-described refractive index modulation. However, it is not limited to all photoreactive monomers included in the photopolymer composition of the above embodiment having a higher refractive index than the polymer matrix, and at least some photoreactive monomers may have a higher refractive index than the polymer matrix in order to implement a high refractive index modulation value. For example, the photoreactive monomer may include a monomer having a refractive index of 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or 1.60 or more but 1.70 or less.

[0063] The photoreactive monomer may include at least one monomer selected from the group consisting of a monofunctional monomer having one photoreactive functional group and a polyfunctional monomer 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.

[0064] The above monofunctional monomers include, for example, benzyl (meth)acrylate (Miwon's M1182 refractive index 1.5140), benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate (Miwon's M1122 refractive index 1.565), phenol (ethylene oxide) (meth)acrylate (phenol (EO) (meth)acrylate; Miwon's M140 refractive index 1.516), phenol (ethylene oxide) 2 (meth)acrylate (phenol (EO) 2 (meth)acrylate; Miwon's M142 refractive index 1.510), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol (EO) (meth)acrylate; Miwon's M1142 refractive index 1.577), and phenylthioethyl (meth)acrylate (Miwon's M1162 refractive index 1.560) and biphenylmethyl (meth)acrylate.

[0065] The above multifunctional monomer is, for example, bisphenol A (ethylene oxide). 2~10 Di(meth)acrylate (bisphenol A (EO) 2~10(meth)acrylate; Miwon's M240 refractive index 1.537, M241 refractive index 1.529, M244 refractive index 1.545, M245 refractive index 1.537, M249 refractive index 1.542, M2100 refractive index 1.516, M2101 refractive index 1.512), bisphenol A epoxy di(meth)acrylate (Miwon's PE210 refractive index 1.557, PE2120A refractive index 1.533, PE2120B refractive index 1.534, PE2020C refractive index 1.539, PE2120S refractive index 1.556), bisfluorene di(meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR6042 refractive index 1.600), modified bisphenol fluorene di(meth)acrylate (Miwon's HR 6060 refractive index 1.584, HR6100 refractive index 1.562, HR6200 refractive index 1.530), tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate (Miwon's M370 refractive index 1.508), phenol novolac epoxy (meth)acrylate (Miwon's SC6300 refractive index 1.525), and cresol novolac epoxy (meth)acrylate (Miwon's SC6400 refractive index 1.522, SC6400C refractive index 1.522).

[0066] The above photopolymer layer may contain 50 to 300 parts by weight of a photoreactive monomer based on 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. In this case, the content of the reference polymer matrix means the sum of the contents (weights) of the acrylic polyol and the siloxane polymer forming the matrix. When the above range is satisfied, it is advantageous to secure excellent optical recording characteristics and durability in a high-temperature environment.

[0067] In this specification, the content of the polymer matrix means the sum of the contents (weight) of the acrylic polyol and the siloxane polymer forming the matrix. In other words, the content of the polymer matrix means including both the polymer matrix formed by cross-linking the acrylic polyol and the siloxane polymer and some non-cross-linked polymer matrix precursor.

[0068] The above photopolymer layer includes a photoinitiator system. The photoinitiator system may refer to a combination of a photoinitiator or photosensitizer and a coinitiator that can initiate polymerization by light.

[0069] The above photopolymer layer may include a photosensitizer and a co-initiator as a photoinitiator system.

[0070] As the above photosensitizer, for example, a photosensitizing dye can be used. Specifically, the above-mentioned photosensitizing dyes include, for example, silicon rhodamine compounds, sulfonium derivatives of ceramidonine, new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose bengal, thionine, basic yellow, pinacynol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, QuinaldineRed, and crystal. One or more selected from the group consisting of crystal violet, brilliant green, astrazon orange G, darrow red, pyronin Y, basic red 29, pyrylium iodide, safranin O, cyanine, methylene blue, Azure A, and BODIPY may be used.

[0071] For example, as the above-mentioned photosensitizing dye, Cy3 and Cy5 (H-Nu 640, spectra) as cyanine dyes or safranin O can be used.

[0072] The photopolymer layer may contain the photosensitive dye in an amount ranging from 0.01 to 10 parts by weight based on 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 range is satisfied, it is advantageous to secure the desired optical recording characteristics by exhibiting an appropriate polymerization reaction speed.

[0073] The above public agent may be an electron donor, an electron acceptor, or a mixture thereof.

[0074] For example, the photopolymer layer may include an electron donor as a public agent. The electron donor may include, for example, a borate anion represented by the following chemical formula 3.

[0075] [Chemical Formula 3]

[0076] BX 1 X 2 X 3 X 4

[0077] In the above chemical formula 3, X 1 Inland 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 Inland X 4 At least one of them is not an aryl group.

[0078] When the above-mentioned alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 30 carbon atoms, arylalkyl group having 7 to 30 carbon atoms, alkylaryl group having 7 to 30 carbon atoms or allyl group is substituted, it may be substituted with at least one selected from the group consisting of halogen and alkoxy group having 1 to 5 carbon atoms.

[0079] Specifically, X 1 Inland 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 independently substituted or unsubstituted with halogen, and X 4 may be n-butyl, n-pentyl or n-hexyl. More specifically, the borate anion represented by the above chemical formula 3 may be, for example, a triphenylbutylborate anion.

[0080] The cation combined with the above 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 connected via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3, etc.).

[0081] As the electron donor, for example, commercially available butyryl choline triphenylbutylborate (Borate V, manufacturer: Spectra group) can be used.

[0082] For example, the photopolymer layer may include an electron acceptor as a public agent. The electron acceptor may include, for example, an onium salt, such as a sulfonium salt, an iodonium salt, or a mixture thereof.

[0083] For example, the electron acceptor may include an iodonium salt. For example, commercially available H-Nu 254 (Spectra) may be used as the electron acceptor.

[0084] The photopolymer layer may contain the public domain agent in an amount of 0.05 to 10 parts by weight based on 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the public domain agent may be, for example, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, or 0.5 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above range is satisfied, it is advantageous to secure the desired optical recording characteristics by exhibiting an appropriate polymerization reaction rate.

[0085] The above photoinitiator system may include an additional photoinitiator to remove the color of the photosensitive dye after light irradiation for recording and to react any unreacted photoreactive monomer. As the photoinitiator, for example, an acetophenone-based compound, an oxime-based compound, a phosphine oxide-based compound, a thioxanthone-based compound, a benzoic acid ester-based compound, an imidazole-based compound, an N-aryl glycine derivative, an organic azide compound, a titanocene, an aluminate complex, an organic peroxide, an N-alkoxy pyridinium salt, an amine derivative, a diazonium salt, a sulfonium salt, an iodonium salt, a sulfonic acid ester, an imide sulfonate, a dialkyl-4-hydroxy sulfonium salt, an aryl sulfonic acid-p-nitro benzyl ester, a silanol-aluminum complex, (η6-benzene) (η5-cyclopentadienyl)iron (II), benzoin tosylate, 2,5-dinitro benzyl tosylate, N-tosylphthalic acid imide, or a mixture thereof may be used.

[0086] More specifically, the photoinitiator includes 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (Irgacure 369), 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyloxime) (Irgacure OXE02, BASF), [(Z)-(1-oxo-1-phenylpropan-2-ylidene)amino] benzoate (TPI-057 or TPI-059 manufactured by TREEEL), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure TPO), Bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide (Irgacure 1700), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Irgacure 819), 2,4-diethyl thioxanthone, 2-chlorothioxanthone, isopropyl thioxanthone, diisopropyl thioxanthone, ethyl 4-(dimethylamino)benzoate, 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazoline, 2-mercaptobenzimidazole, Examples include, but are not limited to, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethan-1-one (Irgacure 651), 1-hydroxy-cyclohexyl-phenylketone (Irgacure 184), bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium (Irgacure 784), Ebecryl P-115 (SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (Dow Chemical Co. in USA), Irgacure 264, Irgacure 250 (BASF), CIT-1682 (Nippon Soda), or mixtures thereof. no.

[0087] The above photopolymer layer includes a fluorine-based compound as a plasticizer. The plasticizer facilitates refractive index modulation during the manufacture of a holographic recording medium. More specifically, the plasticizer lowers the glass transition temperature of the polymer matrix, thereby improving the fluidity of the photoreactive monomer. Furthermore, the plasticizer has low refractive index and non-reactivity characteristics, and thus, when the photoreactive monomer is uniformly distributed within the polymer matrix and moves in the opposite direction to the non-photopolymerized photoreactive monomer, the plasticizer can contribute to refractive index modulation. In addition, the plasticizer can also contribute to improving the formability of the photopolymer composition.

[0088] The above fluorine-based compound may have a low refractive index of 1.45 or less in order to perform the above-described plasticizer function. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less, and the lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. Since the fluorine-based compound having a lower refractive index than the above-described photoreactive monomer is used, the refractive index of the polymer matrix can be further lowered, and the refractive index modulation with the photoreactive monomer can be further increased.

[0089] The non-reactive plasticizer is dispersed within the polymer matrix, which serves as the support for the photopolymer layer, without being chemically bonded to the polymer matrix. Accordingly, the non-reactive plasticizer can migrate to the surface of the photopolymer layer depending on the environment in which the holographic recording medium is used, and can migrate to the surface of the photopolymer layer particularly easily at high temperatures. The plasticizer that migrates to the surface in this way forms a different refractive index layer with different refractive indices on the surface of the photopolymer layer, and this different refractive index layer is a major cause of deterioration in the reliability of the holographic recording medium.

[0090] The holographic recording medium according to the above embodiment may include a branched fluorine compound that is hardly migrated to the surface of the photopolymer layer or is so small that it can be ignored even in a high-temperature environment. Accordingly, a different refractive index layer formed by the migration of the plasticizer within the photopolymer layer to the surface is not formed or is formed at a very small level, so that the originally intended image can be clearly reproduced and high transparency can be exhibited even at high temperatures.

[0091] The holographic recording medium of the above embodiment may have a sufficiently low value of Pn calculated by Equation 1 below. For example, the holographic recording medium of the above embodiment may have a P80 (thickness ratio of the refractive index layer formed at 80°C) calculated by Equation 1 below of 0.10% or less.

[0092] [Formula 1]

[0093] Pn (%) = {A1 / (A1+A2)} * 100

[0094] In the above equation 1, Pn is the thickness ratio of the refractive index layer formed at n ℃,

[0095] A1 is the thickness of the refractive index layer formed at n ℃, and the refractive index layer means a surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm.

[0096] A2 is the thickness of the remaining portion of the photopolymer layer excluding the refractive index layer.

[0097] The above-mentioned different refractive index layer refers to a surface portion of a photopolymer layer that exhibits a different refractive index from the central refractive index of the photopolymer layer, and refers to a portion that exhibits a refractive index difference of 0.0010% or more from the central refractive index. As an example, if the central refractive index of the photopolymer layer is 1.5, the different refractive index layer can be defined based on the boundary where the refractive index is 0.000015 (= 1.5 * 0.00001) or more higher or lower than 1.5.

[0098] The thickness (A1) of the above-mentioned refractive index layer can be obtained through Equation 1 by measuring the refractive index from the surface to the center of the photopolymer layer within the wavelength range of 320 to 1680 nm. The thickness (A1) of the above-mentioned refractive index layer can be defined as the thickness at the wavelength at which the thickness (A1) of the refractive index layer is observed to be the thickest within the wavelength range of 320 to 1680 nm.

[0099] The above P80 being 0.10% or less means that even when the holographic recording medium is exposed to a high temperature of 80°C, the migration of the fluorine compound to the surface is suppressed, and the degree of formation of a variable refractive index layer due to the migration of the fluorine compound is minimal. Accordingly, when the Pn calculated by the above formula 1 shows a sufficiently low value, the holographic recording medium can clearly reproduce the originally intended image without any degradation in image reproduction ability even at high temperatures.

[0100] The upper limit of the above P80 may be, for example, 0.10% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, or 0.05% or less. And the lower limit may be, for example, 0% or more.

[0101] The method and detailed conditions for measuring the refractive index, etc. for calculating Pn of the above formula 1 may refer to the contents described in Test Example 1 described below. Pn of the above formula 1 may be the thickness ratio of the refractive index layer formed at n ℃ for the hologram recording medium before recording.

[0102] The holographic recording medium of the above embodiment may have a small difference in refractive index between the center and the surface. For example, at 80°C, the difference in refractive index between the center of the photopolymer layer and the surface within a thickness of 0.05% may be 0.080 or less.

[0103] The difference in refractive index between the center of the photopolymer layer and the surface within a thickness of 0.05% at 80°C may be, for example, 0.080 or less, 0.070 or less, 0.060 or less, 0.050 or less, 0.040 or less, 0.030 or less, 0.028 or less, or 0.026 or less. The lower limit of the refractive index difference is not particularly limited and may be 0 or more or 0.001 or more. The method and detailed conditions for measuring the refractive index may refer to the contents described in Test Example 1 described below.

[0104] Holographic recording media utilize a mixture of low-refractive index and high-refractive index components to record optical properties. Due to their compatibility, they are prone to opacity. Furthermore, at high temperatures, the decomposition or surface migration of plasticizers, which are low-refractive index components, can further increase the opacity of the holographic recording media.

[0105] However, the holographic recording medium of the above embodiment can maintain excellent transparency even when exposed to high temperatures by using a branched fluorine compound that minimizes decomposition and migration at high temperatures as a plasticizer and exhibits excellent compatibility with a component having a high refractive index.

[0106] Specifically, the holographic recording medium of the above embodiment may have a sufficiently low value of △Hn calculated by Equation 2 below. For example, the holographic recording medium of the above embodiment may have a △H80 (haze increase at 80°C) calculated by Equation 2 below of 10 %p or less.

[0107] [Formula 2]

[0108] △Hn (%p) = B2 - B1

[0109] In the above equation 2, △Hn is the haze increase of n ℃ of the holographic recording medium,

[0110] B1 is the initial haze of the holographic recording medium before being exposed to n ℃,

[0111] B2 is the haze of the holographic recording medium after leaving the holographic recording medium at n ℃ for 100 hours.

[0112] The above △H80 being 10%p or less means that even when the holographic recording medium is exposed to a high temperature of 80°C, the migration of fluorine compounds to the surface is suppressed, resulting in a small increase in haze. Accordingly, when △Hn calculated by the above formula 2 exhibits a sufficiently low value, the holographic recording medium can exhibit transparent optical properties even at high temperatures.

[0113] The upper limit of the above △H80 may be, for example, 9 %p or less, 8 %p or less, 7 %p or less, 6 %p or less, 5 %p or less, 4 %p or less, 3 %p or less, 2.5 %p or less, 2 %p or less, 1.5 %p or less, or 1.0 %p or less. The lower limit of the above haze increase is not particularly limited and may be 0 %p or more. The above haze increase can be measured by the method described in Test Example 2 described below. △Hn in the above formula 2 may mean the haze increase at n ℃ for the hologram recording medium after recording.

[0114] For example, the holographic recording medium according to the above embodiment may include a compound represented by the following chemical formula 4a as the branched fluorine compound.

[0115] [Chemical Formula 4a]

[0116]

[0117] In the above chemical formula 4a,

[0118] Z a1 is -O- or -NH-,

[0119] Z a2 is a single bond, -O- or -NH-,

[0120] L a1 is a single bond or a 2- to 6-valent organic group in which a hydroxyl group is removed from a polyol having 2 to 6 alcohol groups,

[0121] na and ma are each independently integers from 1 to 5, and the sum of na and ma is from 2 to 6,

[0122] R a1 , R a2 and R a3 are each independently a methyl group or an ethyl group,

[0123] R a4 is a fluorine-containing substituent, such as an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines.

[0124] In the above chemical formula 4a, L a1 A moiety containing a carbonyl group and R a4 Connect the parts that include . Therefore, the sum of na and ma is 2 to 6, L a1 It is equal to the combination number of .

[0125] For example, in the chemical formula 4a, L a1 may be a single bond. In the above chemical formula 4a, L a1 In this single bond case, na and ma are each 1, and Z a2 It may also be a single bond. In this case, the fluorine compound represented by the above chemical formula 4a may be represented by the following chemical formula 4a-1.

[0126] [Chemical Formula 4a-1]

[0127]

[0128] In the above chemical formula 4a-1,

[0129] Z a1' , R a1' , R a2' , R a3' and R a4' are respectively Z of the above chemical formula 4a a1 , R a1 , R a2 , R a3 and R a4 Same as above Z a1' , R a1' , R a2' , R a3' and R a4' In this specification, Z of the above chemical formula 4a a1 , R a1 , R a2 , R a3 and R a4 These may be substituents described as specific examples.

[0130] As another example, in the above chemical formula 4a, L a1 The hydroxyl group of the polyol having 2 to 6 alcohol groups is Z a1 and Z a2 It can be a 2 to 6-valent organic group in which the hydroxyl group is removed from the polyol by substitution. As an example, glycerol having three alcohol groups A trivalent organic group from which the hydroxyl group has been removed is It is displayed as follows.

[0131] In the above chemical formula 4a, the L a1 For example, it may be a divalent organic group in which a hydroxy group is removed from a diol such as ethanediol, propanediol or butanediol; a trivalent organic group in which a hydroxy group is removed from a triol such as glycerol or trimethylolpropane; a tetravalent organic group in which a hydroxy group is removed from a tetraol such as pentaerythritol or ditrimethylolpropane; a pentavalent organic group in which a hydroxy group is removed from a pentaol such as 6-methylheptanepentaol; or a hexavalent organic group in which a hydroxy group is removed from a hexaol such as dipentaerythritol.

[0132] In the above chemical formula 4a, L a1 If this is a single bond or a divalent organic group, na and ma are each 1. If the above L a1 In the case of an organic group of 3 to 6, na may be greater than ma. For example, na may be an integer from 1 to 3, and ma may be an integer of 1.

[0133] For example, the above L a1 It can be a trivalent organic group in the form of a hydroxyl group removed from glycerol, which is a triol. In addition, na can be 2 and ma can be 1. In this case, the fluorine-containing compound represented by the above chemical formula 4a can be represented by the following chemical formula 4a-2.

[0134] [Chemical Formula 4a-2]

[0135]

[0136] In the above chemical formula 4a-2,

[0137] Z a1" , Z a2" , R a1" , R a2" , R a3" and R a4" are respectively Z of the above chemical formula 4a a1 , Z a2 , R a1 , R a2 , R a3 and R a4 Same as above Z a1" , Z a2" , R a1" , R a2" , R a3" and R a4" In this specification, Z of the above chemical formula 4a a1 , Z a2 , R a1 , R a2 , R a3 and R a4 These may be substituents described as specific examples.

[0138] In the above chemical formula 4a, the fluorine-containing substituent may be an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines. Specifically, the fluorine-containing substituent may be a straight-chain alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines. More specifically, the fluorine-containing substituent may be -(CH2) a (CF2) b CHF2 or -(CH2) a (CF2) b It can be CF3. Here, a is an integer from 0 to 3, an integer from 0 to 2, or an integer of 1, and b can be an integer from 0 to 19, an integer from 0 to 15, an integer from 0 to 12, an integer from 0 to 11, an integer from 0 to 10, or an integer from 0 to 9.

[0139] Meanwhile, as another example, the holographic recording medium according to the above embodiment may include a compound represented by the following chemical formula 4b as the branched fluorine compound.

[0140] [Chemical Formula 4b]

[0141]

[0142] In the above chemical formula 4b,

[0143] Z b1 is -O- or -NH-,

[0144] Z b2 is a single bond, -O- or -NH-,

[0145] L b1 is a single bond or a 2- to 6-valent organic group in which a hydroxyl group is removed from a polyol having 2 to 6 alcohol groups,

[0146] nb and mb are each independently integers from 1 to 5, and the sum of nb and mb is from 2 to 6,

[0147] Rb1 is a methyl group or an ethyl group,

[0148] R b2 Inland R b4 At least one of the fluorine-containing substituents is an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines,

[0149] R b2 and R b3 If each of the substituents is not a fluorine-containing substituent, each independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-,

[0150] R b4 If it is not a fluorine-containing substituent, it is an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-.

[0151] In the above chemical formula 4b, L b1 A moiety containing a carbonyl group and R b4 Connect the part containing . Therefore, the sum of nb and mb is 2 to 6, L b1 It is equal to the combination number of .

[0152] For example, in the chemical formula 4b, L b1 may be a single bond. In the above chemical formula 4b, L b1In this single bond case, nb and mb are each 1, and Z b2 It may also be a single bond. In this case, the fluorine compound represented by the above chemical formula 4b may be represented by the following chemical formula 4b-1.

[0153] [Chemical Formula 4b-1]

[0154]

[0155] In the above chemical formula 4b-1,

[0156] Z b1' , R b1' , R b2' , R b3' and R b4' are respectively Z of the above chemical formula 4b b1 , R b1 , R b2 , R b3 and R b4 Same as above Z b1' , R b1' , R b2' , R b3' and R b4' In this specification, Z of the above chemical formula 4b b1 , R b1 , R b2 , R b3 and R b4 These may be substituents described as specific examples.

[0157] As another example, in the chemical formula 4b, L b1 The hydroxyl group of the polyol having 2 to 6 alcohol groups is Z b1 and Z b2 It may be a 2-6 valent organic group in which the hydroxyl group is removed from the polyol by substitution.

[0158] In the above chemical formula 4b, the L b1For example, it may be a divalent organic group in which a hydroxy group is removed from a diol such as ethanediol, propanediol or butanediol; a trivalent organic group in which a hydroxy group is removed from a triol such as glycerol or trimethylolpropane; a tetravalent organic group in which a hydroxy group is removed from a tetraol such as pentaerythritol or ditrimethylolpropane; a pentavalent organic group in which a hydroxy group is removed from a pentaol such as 6-methylheptanepentaol; or a hexavalent organic group in which a hydroxy group is removed from a hexaol such as dipentaerythritol.

[0159] In the above chemical formula 4b, L b1 If this is a single bond or a divalent organic group, nb and mb are each 1. If the above L b1 In the case of an organic group of 3 to 6, nb may be greater than mb. For example, nb may be an integer from 1 to 3, and mb may be an integer of 1.

[0160] For example, the above L b1 It can be a trivalent organic group in the form of glycerol in which a hydroxyl group is removed. In addition, nb can be 2 and mb can be 1. In this case, the fluorine-containing compound represented by the chemical formula 4b can be represented by the following chemical formula 4b-2.

[0161] [Chemical Formula 4b-2]

[0162]

[0163] In the above chemical formula 4b-2,

[0164] Z b1" , Z b2" , R b1" , R b2" , R b3" and R b4" are respectively Z of the above chemical formula 4b b1 , Z b2 , R b1 , R b2 , R b3 and R b4 Same as above Z b1" , Z b2" , Rb1" , R b2" , R b3" and R b4" In this specification, Z of the above chemical formula 4b b1 , Z b2 , R b1 , R b2 , R b3 and R b4 These may be substituents described as specific examples.

[0165] In the above chemical formula 4b, R b2 Inland R b4 At least one of the fluorine-containing substituents is a fluorine-containing substituent. The fluorine-containing substituent may be an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines. Specifically, the fluorine-containing substituent may be a straight-chain alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines. More specifically, the fluorine-containing substituent may be -(CH2) a (CF2) b CHF2 or -(CH2) a (CF2) b It can be CF3. Here, a is an integer from 0 to 3, an integer from 0 to 2, or an integer of 1, and b can be an integer from 0 to 19, an integer from 0 to 15, an integer from 0 to 12, an integer from 0 to 11, an integer from 0 to 10, or an integer from 0 to 9.

[0166] In the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituents is replaced with -O-, -S-, or -NH-.

[0167] Specifically, in the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3 are each independently hydrogen, a straight-chain alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, or -(R 5 -O) p -R 6 It can be. The above -(R 5 -O) p -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, and R 6 is an alkyl group having 1 to 6 carbon atoms, and p can be an integer from 1 to 12.

[0168] More specifically, in the above chemical formula 4b, R b2 and R b3 If R is not a fluorine-containing substituent, b2 and R b3 are each independently hydrogen, methyl, ethyl, propyl, butyl, cyclohexyl, tetrahydropyranyl, phenyl or -(R 5 -O) p -R 6 It can be. Here, the R 5R may be a methylene group, an ethylene group, an n-propylene group or an n-butylene group, and among these, it may be a methylene group or an ethylene group. 6 may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and among these, may be a methyl group. The p may be, for example, an integer from 1 to 12, an integer from 1 to 10, an integer from 1 to 8, an integer from 1 to 6, an integer from 1 to 5, an integer from 1 to 4, or an integer from 1 to 3.

[0169] In the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4 is an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-.

[0170] Specifically, in the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4 is a straight chain alkyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, or -(R 5 -O) p -R 6 It can be. The above -(R 5 -O) p -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, and R 6 is an alkyl group having 1 to 6 carbon atoms, and p can be an integer from 1 to 12.

[0171] More specifically, in the above chemical formula 4b, R b4 If R is not a fluorine-containing substituent, b4 is -(R 5 -O) p -R6 It can be. Here, the R 5 R may be a methylene group, an ethylene group, an n-propylene group or an n-butylene group, and among these, it may be a methylene group or an ethylene group. 6 may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and among these, may be a methyl group. The p may be, for example, an integer from 1 to 12, an integer from 1 to 10, an integer from 1 to 8, an integer from 1 to 6, an integer from 1 to 5, an integer from 1 to 4, or an integer from 1 to 3.

[0172] Meanwhile, as another example, the holographic recording medium according to the above embodiment may include a compound represented by the following chemical formula 4c as the branched fluorine compound.

[0173] [Chemical formula 4c]

[0174]

[0175] In the above chemical formula 4c,

[0176] Z c1 and Z c2 are each independently -O-, -S- or -NH-,

[0177] R c1 Inland R c4 At least one of the fluorine-containing substituents is an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines,

[0178] R c1 Inland R c4When the substituents are not fluorine-containing, 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 at least one -CH2- of the substituents is replaced with -O-, -S-, or -NH-.

[0179] In the above chemical formula 4c, R c1 Inland R c4 At least one of which is a fluorine-containing substituent. For example, the R c1 may be a fluorine-containing substituent.

[0180] The fluorine-containing substituent may be an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines.

[0181] Specifically, the fluorine-containing substituent may be a straight-chain alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 12 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 14 carbon atoms substituted with two or more fluorines.

[0182] More specifically, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) b CF3, a decafluorocyclohexyl group, or a pentafluorophenyl group. Here, a is an integer from 0 to 3, an integer from 0 to 2, or an integer from 0 to 1, and b is an integer from 0 to 19, an integer from 0 to 15, an integer from 0 to 14, an integer from 0 to 13, an integer from 0 to 12, or an integer from 0 to 11.

[0183] For example, the fluorine-containing substituent is -(CH2) a (CF2) b CHF2, -(CH2) a (CF2) b In the case of CF3 or decafluorocyclohexyl group, it is possible to provide a holographic recording medium with low haze while contributing to greatly modulating the refractive index.

[0184] In the above chemical formula 4c, R c1 Inland R c4 If R is not a fluorine-containing substituent, c1 Inland R c4 are each independently 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 at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-.

[0185] Specifically, in the above chemical formula 4c, R c1 Inland R c4 If R is not a fluorine-containing substituent, c1 Inland R c4 are each independently a straight chain alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heteroaryl group having 4 to 12 carbon atoms, an arylalkyl group having 7 to 16 carbon atoms, or -(R 5 -Y 1 ) c -R 6 It can be. The above -(R 5 -Y 1 ) c -R 6 In R 5 is an alkylene group having 1 to 6 carbon atoms, and R 6is 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, and Y 1 is -O- or -S-, c can be an integer from 1 to 12, and when c is 2 or greater, R 5 may be identical or different.

[0186] More specifically, in the above chemical formula 4c, R c1 Inland R c4 If R is not a fluorine-containing substituent, c1 Inland R c4 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) d1 CH3, -CH2O(CH2CH2O) d2 CH3, cyclohexyloxyethyl group, cyclohexylmercaptoethyl group or phenyloxyethyl group. Here, d1 is an integer from 1 to 5, and d2 is an integer from 1 to 4.

[0187] The hologram recording medium according to the above embodiment may include at least one or a combination of two or more fluorine compounds selected from among the fluorine compounds represented by the above chemical formulae 4a to 4c as the branched fluorine compound.

[0188] The above photopolymer layer may contain 20 to 200 parts by weight of the fluorine-based compound based on 100 parts by weight of the 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 range is satisfied, the fluorine-based compound having a sufficiently low refractive index can exhibit a large refractive index modulation value after recording without problems such as poor compatibility with components included in the photopolymer composition, causing some of the fluorine-based compound to leach to the surface of the photopolymer layer, or worsening haze, thereby securing excellent optical recording characteristics.

[0189] The above photopolymer layer can secure better high-temperature reliability by including a predetermined polymer matrix, a photoreactive monomer, and a fluorine-based compound.

[0190] For example, the photopolymer layer may include 25 to 40 wt% of the polymer matrix, 25 to 45 wt% of the photoreactive monomer, and 25 to 50 wt% of the fluorinated compound, based on the total weight of the polymer matrix, the photoreactive monomer, and the fluorinated compound.

[0191] More specifically, the polymer matrix may be included in an amount of, for example, 25 wt% or more and 40 wt% or less, 35 wt% or less, or 33 wt% or less. The photoreactive monomer may be included in an amount of, for example, 25 wt% or more, 30 wt% or more, or 33 wt% or more, but 45 wt% or less, 43 wt% or less, or 41 wt% or less. The fluorine-based compound may be included in an amount of, for example, 25 wt% or more, 30 wt% or more, or 33 wt% or more, but 50 wt% or less, 45 wt% or less, 40 wt% or less, or 38 wt% or less. Within this range, the migration of the fluorine-based compound to the surface at high temperatures can be effectively prevented, thereby more easily securing high-temperature reliability and high-temperature transparency.

[0192] The above photopolymer layer may additionally include additives such as a defoaming agent.

[0193] The above photopolymer layer may include a silicone-based reactive additive as a defoaming agent. As the silicone-based reactive additive, commercially available products such as Tego Rad 2500 may be used, for example.

[0194] The content of the above additives, for example, the defoaming agent, can be appropriately adjusted to a level that does not impede the function of the holographic recording medium.

[0195] The above photopolymer layer may be formed from a photopolymer composition containing a solvent.

[0196] The solvent may be an organic solvent, and for example, may be at least one organic solvent selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited thereto. Specific examples of such organic solvents include at least one selected from the group consisting of ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; and ethers such as tetrahydrofuran or propylene glycol monomethyl ether.

[0197] The organic solvent may be added at the time when each component included in the photopolymer composition is mixed, or may be included in the photopolymer composition while each component is added in a dispersed or mixed state in the organic solvent.

[0198] The photopolymer composition may include a solvent so that the solid concentration is 1 to 90 wt%. Specifically, the photopolymer composition may include a solvent so that the solid concentration is 20 wt% or more, 30 wt% or more, 50 wt% or more, or 60 wt% or more, and 85 wt% or less, 80 wt% or less, 75 wt% or less, or 70 wt% or less. Within this range, the photopolymer composition exhibits appropriate flowability and can form a coating film without defects such as stripes, and no defects occur during the drying and curing processes thereof, so that a photopolymer layer exhibiting desired physical properties and surface characteristics can be formed.

[0199] The holographic recording medium of the above embodiment may further include a substrate on at least one surface of the photopolymer layer. The type of substrate is not particularly limited, and any substrate known in the relevant 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.

[0200] The holographic recording medium of the above embodiment can exhibit a large refractive index modulation value and high diffraction efficiency despite its thin thickness.

[0201] 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.

[0202] The hologram recording medium of the above embodiment is not limited thereto, but may be one on which a reflective hologram or a transmissive hologram is recorded.

[0203] The above holographic recording medium may have a notch filter structure in relation to the diffraction grating structure. That the holographic recording medium of the above embodiment has a notch filter structure may mean, for example, that the diffraction grating is not inclined (non-slanted) (substantially 0°) with respect to the substrate plane, such as that the diffraction grating is parallel to the substrate plane. 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. In addition, the two repeated layers may each have a predetermined thickness that is the same or different from each other. Such a non-slanted diffraction grating recording can be manufactured in a manner in which the incident angles of the object light and the reference light are the same with respect to the normal. In a non-slanted structure, the degree of deformation (e.g., shrinkage or expansion) under high temperature and high humidity conditions is more clearly confirmed than in a slanted structure, and the recording medium may be less affected by shrinkage and expansion of the substrate.

[0204] The hologram recording medium of the above embodiment can have high diffraction efficiency. For example, the hologram recording medium can have a diffraction efficiency of 70% or more when recording a notch filter hologram. At this time, the thickness of the photopolymer layer can be, for example, 5 to 30 μm. Specifically, when recording the notch filter hologram, the diffraction efficiency can be 71% or more, 72% or more, 73% or more, 74% or more, 75% or more, 80% or more, 81% or more, 82% or more, 83% or more, 84% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90% or more. In this way, the hologram recording medium of the above embodiment can implement excellent diffraction efficiency even if it includes a photopolymer layer with a thin thickness. The above diffraction efficiency can be measured by the method described in Test Example 2 described below.

[0205] The holographic recording medium of the above embodiment can implement a refractive index modulation value (△n) 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 ㎛. 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 Test Example 2 described below.

[0206] The holographic recording medium of the above embodiment is expected to provide various optical elements that can be used even in environments where a lot of heat is generated, as it exhibits excellent optical recording characteristics, excellent durability in high-temperature environments, and high-transparency optical characteristics.

[0207] The uses of the holographic recording medium of the above embodiment are not particularly limited. As a non-limiting example, the holographic recording medium may be used in applications likely to be exposed to high-temperature environments, specifically, smart devices such as mobile devices, components of wearable displays, or automotive components (e.g., head-up displays). The holographic recording medium of the above embodiment has excellent high-temperature reliability and can thus exhibit its originally intended optical recording characteristics even at high temperatures.

[0208] Meanwhile, the hologram recording medium of the above embodiment is manufactured through a step of forming a photopolymer layer by applying a photopolymer composition, and a step of irradiating a coherent laser to a predetermined area of ​​the photopolymer layer manufactured in this way before recording to selectively polymerize a photoreactive monomer included in the photopolymer layer, thereby recording optical information, so that the optical information can be manufactured in a form in which optical information is recorded.

[0209] In the step of forming the photopolymer layer, a photopolymer composition comprising the above-described composition may first be prepared. When preparing the photopolymer composition, a commonly known mixer, stirrer, or mixer may be used to mix each component without particular limitation. In addition, this mixing process may be performed at a temperature ranging from 0°C to 100°C, from 10°C to 80°C, or from 20°C to 60°C.

[0210] In the step of forming the above photopolymer layer, the prepared photopolymer composition may be applied to form a coating film formed from the photopolymer composition. The coating film may be dried naturally at room temperature or at a temperature in the range of 30 to 80°C. Through this process, a hydrosilylation reaction between the unreacted hydroxyl groups of the acrylic polyol and the silane functional groups of the siloxane polymer may be induced.

[0211] The photopolymer layer manufactured through the step of forming the above photopolymer layer may have a fluorine-based compound, a photoreactive monomer, a photoinitiator, and additives added as needed uniformly dispersed within the crosslinked polymer matrix.

[0212] Thereafter, when a coherent laser is irradiated on the photopolymer layer in the step of recording optical information, polymerization of the photoreactive monomer occurs in the region where constructive interference occurs, thereby forming a photopolymer, and polymerization of the photoreactive monomer does not occur or is suppressed in the region where destructive interference occurs, thereby forming a photoreactive monomer. Then, the unreacted photoreactive monomer diffuses toward 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. Accordingly, a hologram, i.e., optical information, is recorded on the photopolymer layer having the diffraction grating.

[0213] The holographic recording medium of the above embodiment can be provided in a state where the reaction of the photoreactive monomer is terminated and the color of the photosensitive dye is removed through a photobleaching step in which the photopolymer layer on which the optical information is recorded is irradiated with light throughout the entire layer, which can be performed after the step of recording the optical information.

[0214] For example, in the photobleaching step, ultraviolet (UVA) rays in the range of 320 to 400 nm can be irradiated to terminate the reaction of the photoreactive monomer and remove the color of the photosensitive dye.

[0215] Meanwhile, according to another embodiment of the invention, an optical element including the holographic recording medium is provided.

[0216] Specific examples of the optical element include smart devices such as mobile devices, components of wearable displays, automotive products (e.g., head up displays), holographic fingerprint recognition systems, holographic optical elements having the functions of optical lenses, mirrors, deflecting mirrors, filters, diffusion screens, diffractive elements, light guides, waveguides, projection screens and / or masks, media and optical diffusion plates of optical memory systems, optical wavelength splitters, reflective and transmissive color filters, etc.

[0217] An example of an optical element including the above holographic recording medium is a holographic display device. The holographic display device includes a light source unit, an input unit, an optical system, and a display unit.

[0218] Specifically, the light source unit is a unit that irradiates a laser beam used to provide, record, and reproduce three-dimensional image information of an object in the input unit and display unit.

[0219] The above input section is a section that inputs 3D image information of an object to be recorded on a display section in advance, and specifically, it is a section that can input 3D information of an object, such as the intensity and phase of light by space, into an electrically addressed liquid crystal SLM, and at this time, an input beam can be used.

[0220] The above optical system may be composed of a mirror, a polarizer, a beam splitter, a beam shutter, a lens, etc. The above optical system may distribute a laser beam emitted from a light source unit into an input beam sent to an input unit, a recording beam sent to a display unit, a reference beam, an erase beam, a readout beam, etc.

[0221] The display unit can receive three-dimensional image information of an object from an input unit, record it on a hologram plate formed of an optically addressed SLM, and reproduce a three-dimensional image of the object. At this time, the three-dimensional image information of the object can be recorded through interference between an input beam and a reference beam. The three-dimensional image information of the object recorded on the hologram plate can be reproduced as a three-dimensional image by a diffraction pattern generated by a readout beam, and an erase beam can be used to quickly remove the formed diffraction pattern. Meanwhile, the hologram plate can be moved between a position for inputting a three-dimensional image and a position for reproducing the image.

[0222] A holographic recording medium according to one embodiment of the invention not only has excellent optical recording characteristics, but also exhibits excellent reliability and transparency even in a high-temperature environment.

[0223] Fig. 1 schematically illustrates a recording equipment setup for hologram recording. Specifically, Fig. 1 schematically illustrates a process in which a laser of a predetermined wavelength is irradiated from a light source (10), and then passes through a mirror (20, 20'), an iris (30), a spatial filter (40), an iris (30'), a collimation lens (50), and a splitter (PBS, Polarized Beam Splitter) (60), and is irradiated onto a PP (hologram recording medium) (80) located on one surface of a mirror (70).

[0224] The following specific examples of the invention will further illustrate its functions and effects. However, these examples are presented as illustrative examples and do not limit the scope of the invention in any way.

[0225] In the following manufacturing examples, examples, and comparative examples, the content of raw materials, etc. refers to the content based on solid content unless otherwise specified.

[0226]

[0227] Manufacturing Example 1: Manufacturing of acrylic polyol

[0228] In a 2 L jacketed reactor, 132 g of butyl acrylate, 420 g of ethyl acrylate, and 48 g of hydroxybutyl acrylate were added, and diluted with 1,200 g of ethyl acetate. The reaction temperature was set to 60 to 70 °C, and stirring was performed for about 30 minutes to 1 hour. 0.42 g of n-dodecyl mercaptan (n-DDM) was additionally added, and stirring was performed for about another 30 minutes. Thereafter, 0.24 g of AIBN, a polymerization initiator, was added, and polymerization was performed at the reaction temperature for more than 4 hours until the residual acrylate content became less than 1%, thereby producing an acrylate copolymer (weight average molecular weight of about 300,000, OH equivalent of about 1802 g / equivalent) in which the hydroxyl group was located in the branched chain.

[0229]

[0230] Example 1: Preparation of photopolymer composition and holographic recording medium

[0231] (1) Preparation of photopolymer composition

[0232] First, 0.57 g of poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number average molecular weight: approximately 590, Si-H equivalent: approximately 103 g / equivalent) as a siloxane polymer and 33.4 g of acrylic polyol having a solid content of 30 wt% (solid content: 10.02 g) manufactured in Manufacturing Example 1 were mixed (SiH / OH molar ratio = 1.0).

[0233] Then, 11.5 g of HR 6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.08 g of photosensitive dye H-Nu 640 (Spectra), 0.3 g of Borate V as a public-use reagent, 11.5 g of a fluorine-based compound represented by the following chemical formula a as a plasticizer, and 26 g of methyl isobutyl ketone (MIBK) as a solvent were added, and stirred for about 30 minutes with a paste mixer in a light-blocking state. Thereafter, a Karstedt (Pt series) catalyst was added for matrix crosslinking to prepare a photopolymer composition.

[0234] [chemical formula a]

[0235]

[0236]

[0237] (2) Manufacturing of holographic recording media

[0238] The above photopolymer composition was coated to a predetermined thickness on a 60 μm thick TAC substrate using a Mayer bar and dried at 80°C for 10 minutes. The thickness of the photopolymer layer after drying was approximately 10 μm.

[0239]

[0240] Examples 2 to 7, Comparative Examples 1 and 2: Preparation of photopolymer composition and holographic recording medium

[0241] A photopolymer composition and a holographic recording medium therefrom were manufactured in the same manner as in Example 1, except that the type of plasticizer was changed as described in Table 1 below.

[0242] Plasticizer Example 1 [Chemical Formula a] Example 2 [Chemical Formula b] Example 3 [Chemical Formula c] Example 4 [Chemical Formula d] Example 5 [Chemical Formula e] Example 6 [Chemical Formula f] Example 7 [Chemical Formula g] Comparative Example 1 [Chemical Formula h] Comparative Example 2 [Chemical Formula i]

[0243]

[0244] Test Example 1: Evaluation of the Transitivity of Holographic Recording Media

[0245] The temperature-dependent migration properties of the holographic recording medium were evaluated. Specifically, to evaluate the temperature-dependent migration properties of the photopolymer layer, the refractive index from the surface to the center of the photopolymer layer was measured as a function of temperature. The refractive index was measured using a spectroscopic ellipsometry device from Ellipso Technology at an incident angle of 70° and a wavelength range of 320 to 1680 nm.

[0246] The thickness (A1) of the refractive index layer having a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer and the thickness (A2) of the remaining portion of the photopolymer layer were measured at different temperatures and are shown in Table 2 below.

[0247] In addition, the percentage (Pn) of the thickness (A1) of the refractive index layer to the total thickness (A1+A2) of the photopolymer layer according to the temperature in Equation 1 below was calculated and shown in Table 2 below.

[0248] [Formula 1]

[0249] Pn (%) = {A1 / (A1+A2)} * 100

[0250] In the above equation 1, Pn is the thickness ratio of the refractive index layer formed at n ℃,

[0251] A1 is the thickness of the refractive index layer formed at n ℃, and the refractive index layer means a surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm.

[0252] A2 is the thickness of the remaining portion of the photopolymer layer excluding the refractive index layer.

[0253]

[0254] Example 1 Example 4 Comparative Example 123 ℃ A10.00760.00880.0094 A215.656716.25416.3077P230.05 %0.05 %0.06 %40 ℃ A10.01270.01050.0303 A215.785016.32216.3352P400.08 %0.06 %0.19 %60 ℃ A10.01100.00950.0404 A215.930716.553216.5539P600.07 %0.06 %0.24 %80 ℃A10.00850.00850.0740A216.047716.729116.7313P800.05 %0.05 %0.44 %

[0255]

[0256] Meanwhile, the degree of temperature-dependent transition of the holographic recording medium before recording was evaluated. Specifically, the refractive indices at the center and surface of the photopolymer layer were measured by temperature and wavelength, and are listed in Table 3 below. The refractive indices were measured using the equipment described above.

[0257]

[0258] Example 1 Example 4 Comparative Example 1 Temperature Wavelength Center Refractive Index Surface Refractive Index of Thickness 0.05 % Center Refractive Index Surface Refractive Index of Thickness 0.05 % Center Refractive Index Surface Refractive Index of Thickness 0.05 % 23 ℃ 530 ㎚ 1.50 89 1.50 93 1.51 52 1.51 56 1.52 0 7 1.53 96 580 ㎚ 1.50 3 2 1.50 2 2 1.50 95 1.50 8 5 1.51 8 4 1.53 3 96 50 ㎚ 1.49 8 1.49 50 1.50 5 11.50 13 1.51 6 11.52 5 48 50 ㎚ 1.49 2 6 1.48 3 7 1.49 8 9 1.48 9 1.51 3 2 1.51 6 240 ℃ 530 ㎚1.50501.50861.51131.51491.51961.4527580 ㎚1.50091.50061.50721.50691.51741.4486650 ㎚1.49751.49321.50381.49951.51431.4429850 ㎚1.48841.48221.49471.49071.51021.437160 ℃530 ㎚1.49711.51821.50341.52461.51371.4072580 ㎚1.49371.51071.50001.51701.51211.4046650 ㎚1.49201.50771.49831.50741.49881.4019850 ㎚1.48091.49411.48711.50031.49111.395580 ℃530 ㎚1.49261.51781.50191.52721.51331.4170580 ㎚1.48901.50961.49821.51901.51121.4115650 ㎚1.48541.50601.49461.51531.49721.4029850 ㎚1.47881.49221.48801.50151.48771.3983

[0259]

[0260] Referring to Tables 2 and 3 above, the photopolymer layers of Examples 1 and 4 are observed to have a very thin refractive index layer with a negligible thickness that does not affect the function of the holographic recording medium, and the difference in absolute refractive index at the center and the surface is also confirmed to be very small.

[0261] In contrast, the photopolymer layer of Comparative Example 1 has a very thick refractive index layer that interferes with the function of the holographic recording medium, and the difference in absolute refractive index between the center and the surface is also very large.

[0262]

[0263] Test Example 2: Performance Evaluation of Holographic Recording Media

[0264] (1) P80 (thickness ratio of the refractive index layer at 80 ℃, %)

[0265] The high-temperature transferability of the holographic recording medium before recording was evaluated. Specifically, to evaluate the transferability of the photopolymer layer at 80°C, the refractive index from the surface to the center of the photopolymer layer at 80°C was measured. The refractive index was measured at an incident angle of 70° and a wavelength of 320 to 1680 nm using spectroscopic ellipsometry from Ellipso Technology.

[0266] And, P80 (thickness ratio of the refractive index layer at 80 ℃) of the following equation 1 was calculated and recorded in Table 4 below.

[0267] [Formula 1]

[0268] Pn (%) = {A1 / (A1+A2)} * 100

[0269] In the above equation 1, Pn is the thickness ratio of the refractive index layer formed at n ℃,

[0270] A1 is the thickness of the refractive index layer formed at n ℃, and the refractive index layer means a surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm.

[0271] A2 is the thickness of the remaining portion of the photopolymer layer excluding the refractive index layer.

[0272]

[0273] (2) △H80 (haze increase at 80 ℃, %p)

[0274] A diffraction grating was recorded using a setup similar to that in Fig. 1. Specifically, when the manufactured photopolymer layer is laminated on a mirror and then irradiated with a laser, a notch filter hologram having a periodic refractive index modulation in the thickness direction can be recorded through interference between the incident light (L) and the light reflected from the mirror (L'). In this example, the notch filter hologram was recorded with an incident angle of 0 ° (degree). A notch filter and a Bragg reflector are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with a difference in refractive index are periodically and repeatedly laminated at a constant thickness.

[0275] The difference in haze before and after high-temperature exposure of a holographic recording medium containing a diffraction grating was evaluated. Haze was measured using a HAZE METER (Murakami Color Research Laboratory, HM-150) in accordance with JIS K 7136. The measurement light was incident on the substrate side of the holographic recording medium.

[0276] Specifically, the holographic recording medium was left at 80°C for 100 hours, and the difference in haze before and after leaving was calculated using Equation 2 below. Then, the haze increase at 80°C (△H80) was recorded in Table 4 below.

[0277] [Formula 2]

[0278] △Hn (%p) = B2 - B1

[0279] In the above equation 2, △Hn is the haze increase of n ℃ of the holographic recording medium,

[0280] B1 is the initial haze of the holographic recording medium before being exposed to n ℃,

[0281] B2 is the haze of the holographic recording medium after leaving the holographic recording medium at n ℃ for 100 hours.

[0282]

[0283] (3) Diffraction efficiency

[0284] The diffraction efficiency (η) was obtained using Equation 3 below for a holographic recording medium that recorded a diffraction grating.

[0285] [Formula 3]

[0286] η(%) = {P D / (P D + P T )} X 100

[0287] In the above equation 3, η is the diffraction efficiency, and P D is the output power (mW / cm2) of the diffracted beam of the sample after recording, and P T is the output power (mW / cm2) of the beam transmitted through the sample after recording.

[0288]

[0289] (4) Refractive index modulation value (△n)

[0290] For a holographic recording medium recording a diffraction grating, the refractive index modulation value (△n) was obtained using Equation 4 and Bragg's equation below.

[0291] [Formula 4]

[0292]

[0293] [Bragg's equation]

[0294]

[0295] In the above equations, 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, △n is the refractive index modulation value, n is the refractive index of the photopolymer, and Λ represents the diffraction grating period. In the above examples and comparative examples, since the hologram was recorded using the notch filter method, θ (incident angle) and φ (slant angle of the grating) are both 0°.

[0296]

[0297] Diffraction Efficiency (%) Refractive Index Modulation Value (△n) P80 (%) △H80 (%p) Example 1870.0370.051.0 Example 2850.0350.070.7 Example 3870.0370.040.9 Example 4910.0410.051.5 Example 5950.0400.071.3 Example 6870.0380.062.1 Example 7920.0410.091.6 Comparative Example 1520.0220.4415.2 Comparative Example 2470.0190.4014.8

[0298]

[0299] Referring to Table 4 above, it was confirmed that the holographic recording media manufactured in Examples 1 to 7 exhibited high diffraction efficiency and refractive index modulation values, while also having excellent high-temperature stability, so that the degree of formation of the refractive index layer was minimal, and the increase in haze was also very small. In contrast, the holographic recording media manufactured in Comparative Examples 1 and 2 had poor optical recording characteristics, and in particular, the refractive index layer was formed thickly at high temperatures, and the haze also increased significantly.

[0300] Accordingly, it is confirmed that the holographic recording medium according to one embodiment of the invention exhibits excellent optical recording properties, high-temperature stability, and high transparency by including a branched fluorine compound.

Claims

1. A polymer matrix or precursor thereof formed by cross-linking a siloxane-based polymer containing a silane functional group and an acrylic polyol; a photopolymer layer containing a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a fluorine-based compound. A holographic recording medium having a Pn of 0.10% or less, P80, which is measured at 80°C using the following formula 1: [Formula 1] Pn (%) = {A1 / (A1+A2)} * 100 In the above equation 1, Pn is the thickness ratio of the refractive index layer formed at n ℃, A1 is the thickness of the refractive index layer formed at n ℃, and the refractive index layer means a surface portion of the photopolymer layer that exhibits a refractive index difference of 0.0010% or more from the central refractive index of the photopolymer layer measured at an incident angle of 70° and a wavelength of 320 to 1680 nm. A2 is the thickness of the remaining portion of the photopolymer layer excluding the refractive index layer.

2. In the first paragraph, the siloxane polymer comprises a repeating unit represented by the following chemical formula 1 and a terminal group represented by the following chemical formula 2, a holographic recording medium: [Chemical Formula 1] In the above chemical formula 1, Multiple R's 11 and R 12 are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, k is an integer between 1 and 10,000, [Chemical Formula 2] In the above chemical formula 2, Multiple R's 13 Inland R 15 are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, At least one repeating unit selected from among the repeating units represented by the above chemical formula 1 and R of one terminal group selected from among the terminal groups represented by the above chemical formula 2 11 Inland R 15 At least one of them is hydrogen.

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

4. In the first paragraph, the photoreactive monomer is at least one monofunctional monomer selected from the group consisting of benzyl (meth)acrylate, benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, phenol (ethylene oxide) 2 (meth)acrylate, O-phenylphenol (ethylene oxide) (meth)acrylate, phenylthioethyl (meth)acrylate, and biphenylmethyl (meth)acrylate; bisphenol A (ethylene oxide) 2~10 A holographic recording medium comprising at least one polyfunctional monomer selected from the group consisting of di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolac epoxy (meth)acrylate; or a mixture of two or more thereof.

5. A holographic recording medium according to claim 1, wherein the photoinitiator system comprises a photosensitive dye and a public initiator.

6. In the fifth paragraph, the public disclosure agent comprises a borate anion represented by the following chemical formula 3, a holographic recording medium: [Chemical Formula 3] BX 1 X 2 X 3 X 4 In the above chemical formula 3, X 1 Inland 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 or an allyl group having 7 to 30 carbon atoms, and X 1 Inland X 4 At least one of them is not an aryl group.

7. In the first paragraph, the fluorine-based compound is a holographic recording medium including a branched fluorine-based compound.

8. In the 7th paragraph, the branched fluorine compound comprises at least one selected from among the fluorine compounds represented by the following chemical formulae 4a to 4c: A holographic recording medium: [Chemical Formula 4a] In the above chemical formula 4a, Z a1 is -O- or -NH-, Z a2 is a single bond, -O- or -NH-, L a1 is a single bond or a 2- to 6-valent organic group in which a hydroxyl group is removed from a polyol having 2 to 6 alcohol groups, na and ma are each independently integers from 1 to 5, and the sum of na and ma is from 2 to 6, R a1 , R a2 and R a3 are each independently a methyl group or an ethyl group, R a4 is a fluorine-containing substituent, an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines. [Chemical Formula 4b] In the above chemical formula 4b, Z b1 is -O- or -NH-, Z b2 is a single bond, -O- or -NH-, L b1 is a single bond or a 2- to 6-valent organic group in which a hydroxyl group is removed from a polyol having 2 to 6 alcohol groups, nb and mb are each independently integers from 1 to 5, and the sum of nb and mb is from 2 to 6, R b1 is a methyl group or an ethyl group, R b2 Inland R b4 At least one of the fluorine-containing substituents is an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines, R b2 and R b3 If each of the substituents is not a fluorine-containing substituent, each independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-, R b4 If it is not a fluorine-containing substituent, it is an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms, or an arylalkyl group having 7 to 40 carbon atoms, or a substituent in which at least one -CH2- of the above substituent is replaced with -O-, -S-, or -NH-, [Chemical formula 4c] In the above chemical formula 4c, Z c1 and Z c2 are each independently -O-, -S- or -NH-, R c1 Inland R c4 At least one of the fluorine-containing substituents is an alkyl group having 1 to 20 carbon atoms substituted with two or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with two or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with two or more fluorines, R c1 Inland R c4 When the substituents are not fluorine-containing, 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 at least one -CH2- of the substituents is replaced with -O-, -S-, or -NH-.

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

10. A hologram recording medium having a diffraction efficiency of 70% or more when recording a notch filter hologram in accordance with paragraph 1.

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

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

13. In the first paragraph, a holographic recording medium in which △H80, which is △Hn measured at 80 ℃ through the following formula 2, is 10 %p or less: [Formula 2] △Hn (%p) = B2 - B1 In the above equation 2, △Hn is the haze increase of n ℃ of the holographic recording medium, B1 is the initial haze of the holographic recording medium before being exposed to n ℃, B2 is the haze of the holographic recording medium after leaving the holographic recording medium at n ℃ for 100 hours.

14. An optical element comprising a holographic recording medium of paragraph 1.

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