Holographic recording medium, method for manufacturing the same, and optical element including the same

Abstract

The present invention relates to a hologram recording medium, a method for manufacturing the same, and an optical element including the same. By controlling the elemental ratio of fluorine on the surface of the photopolymer layer within a specific range, the hologram recording medium can have excellent optical recording characteristics and low haze, and can provide an optical element with excellent visibility.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights under Korean Patent Application No. 10-2023-0076829 dated June 15, 2023, and Korean Patent Application No. 10-2024-0068785 dated May 27, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

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

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

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

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

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

[0007] Recently, there has been a growing demand for the development of materials that possess both high diffraction efficiency and high visibility. [Overview of the project] [Problems that the invention aims to solve]

[0008] According to one embodiment of the present invention, a holographic recording medium is provided.

[0009] According to another embodiment of the present invention, a method for manufacturing the hologram recording medium is provided.

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

[0011] The following describes a holographic recording medium, a method for manufacturing the same, and an optical element including the same, according to specific embodiments of the invention.

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

[0013] According to one embodiment of the invention, a holographic recording medium is provided comprising a polymer matrix formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer containing a fluorine compound, wherein the elemental ratio of fluorine to the total amount of carbon, oxygen, fluorine, and silicon atoms, as confirmed by photoelectron spectroscopy for chemical analysis (ESCA) on the surface of the photopolymer layer, is 0.05 atomic% to 3 atomic%.

[0014] The inventors of the present invention conducted research to improve the visibility of holographic recording media while maintaining their various physical properties at an excellent level. As a result, they confirmed that improving the compatibility of the photopolymer composition reduces the haze of the holographic recording media produced thereby, thereby improving visibility.

[0015] Furthermore, it was confirmed that the elemental ratio of fluorine on the surface of the photopolymer layer decreases as the compatibility of the photopolymer composition improves. However, it was confirmed that if the elemental ratio of fluorine on the surface of the photopolymer layer becomes excessively low, the various physical properties of the hologram recording medium deteriorate. Through experiments, it was confirmed that only when the elemental ratio of fluorine on the surface of the photopolymer layer satisfies a specific range, the hologram recording medium can exhibit excellent optical recording properties, excellent compatibility of the materials constituting the photopolymer layer, and a low haze value, thereby demonstrating excellent visibility. This led to the completion of the present invention.

[0016] Specifically, the elemental ratios on the surface of the photopolymer layer can be confirmed by using photoelectron spectroscopy for chemical analysis (ESCA). According to the ESCA described in the test examples below, after qualitatively analyzing the elements found on the surface of the sample to be analyzed by a survey scan, the elemental ratios can be measured by performing a narrow scan for each element found. The elemental ratios of the photopolymer layer in this specification may be understood as either the elemental ratios of the photopolymer layer before recording or the elemental ratios of the photopolymer layer after recording. The elemental ratios of the photopolymer layer before recording and the elemental ratios of the photopolymer layer after recording may be the same within the experimental error range, but may be different in some embodiments. In other words, even if the elemental ratios of the photopolymer layer before recording and the elemental ratios after recording differ from each other beyond the error range, as long as the elemental ratios before or after recording are within the range described above, the intended effect of the hologram recording medium of one embodiment can be demonstrated.

[0017] The elemental ratio of fluorine on the surface of the photopolymer layer contained in the holographic recording medium of the above embodiment is 0.05 atomic% or more, 0.06 atomic% or more, 0.07 atomic% or more, 0.08 atomic% or more, 0.09 atomic% or more, or 0.10 atomic% or more, and may be 3 atomic% or less, 2.9 atomic% or less, 2.8 atomic% or less, or 2.7 atomic% or less.

[0018] On the surface of the photopolymer layer, the elemental ratio of carbon to the total amount of carbon, oxygen, fluorine, and silicon atoms confirmed by ESCA may be 50 to 80 atoms, the elemental ratio of oxygen may be 15 to 40 atoms, and the elemental ratio of silicon may be 0.5 to 10 atoms.

[0019] Specifically, the elemental ratio of carbon on the surface of the photopolymer layer is 50 atomic% or more, 55 atomic% or more, 60 atomic% or more, 65 atomic% or more, 70 atomic% or more, 71 atomic% or more, or 72 atomic% or more, and may be 80 atomic% or less, 79 atomic% or less, or 78.5 atomic% or less.

[0020] The elemental ratio of oxygen on the surface of the photopolymer layer is 15 atomic% or more, 16 atomic% or more, or 17 atomic% or more, and may be 40 atomic% or less, 35 atomic% or less, 30 atomic% or less, 28 atomic% or less, 26 atomic% or less, 24 atomic% or less, or 22 atomic% or less.

[0021] The elemental ratio of silicon on the surface of the photopolymer layer is 0.5 atomic% or more, 1.0 atomic% or more, or 1.2 atomic% or more, and may be 10 atomic% or less, 9 atomic% or less, or 8 atomic% or less.

[0022] The elemental ratios of carbon, oxygen, fluorine, and silicon are expressed as percentages (atomic %) of the total amount of carbon, oxygen, fluorine, and silicon atoms confirmed by ESCA on the surface of the photopolymer layer.

[0023] The photopolymer layer exhibits excellent optical recording properties, low haze, and superior visibility by having the elemental composition ratio described above. In particular, if the elemental ratio of fluorine is below the range described above, the optical recording properties may deteriorate, and if the elemental ratio of fluorine exceeds the range described above, the haze may increase and visibility may decrease.

[0024] The holographic recording medium of the above embodiment includes a polymer matrix formed by crosslinking a siloxane 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.

[0025] The aforementioned photopolymer layer may be a photopolymer layer in a pre-recording state capable of recording optical information, or it may be a photopolymer layer in a state where optical information has been recorded.

[0026] A photopolymer layer with recorded optical information can be manufactured by irradiating a pre-recorded photopolymer layer with object light and reference light. When a pre-recorded photopolymer layer is irradiated with object light and reference light, the photoinitiator system is inactive in the canceling interference region due to the interference lengths of the object light and reference light, so photopolymerization of photoreactive monomers does not occur. In the reinforcing interference region, photopolymerization of photoreactive monomers occurs due to the activated photoinitiator system. In the reinforcing interference region, the photoreactive monomers are continuously consumed, creating a concentration difference between the canceling and reinforcing interference regions. As a result, the photoreactive monomers in the canceling interference region diffuse into the reinforcing interference region. At this time, the fluorine-based plasticizer moves in the opposite direction to the photoreactive monomers. Since the photoreactive monomers and the photopolymers formed therefrom have a higher refractive index than the polymer matrix and fluorine-based compounds, a spatial change in refractive index occurs in the photopolymer layer, and a lattice is formed by this spatial refractive index modulation in the photopolymer layer. Such lattice surfaces act as reflective surfaces that reflect incident light due to differences in refractive index. After hologram recording, when light of the recording wavelength is incident in the direction of the reference light, the Bragg condition is satisfied, and the light diffracts in the direction of light of the original object, allowing the holographic information to be reconstructed.

[0027] Therefore, if the photopolymer layer is in its pre-recording state, the photopolymer layer may contain photoreactive monomers, photoinitiators, and fluorine compounds randomly dispersed within the polymer matrix.

[0028] In contrast, if optical information is recorded in the photopolymer layer, the photopolymer layer may include a polymer matrix, photopolymers distributed to form a lattice, and a fluorine-based compound.

[0029] The photopolymer layer is formed from a photopolymer composition comprising a polymer matrix and its precursor formed by crosslinking a siloxane polymer containing silane functional groups and an acrylic polyol; a fluorine-based compound; a photoreactive monomer; and a photoinitiator system.

[0030] The polymer matrix is ​​formed by crosslinking a siloxane polymer containing silane functional groups (Si-H) with an acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking an acrylic polyol with a siloxane polymer containing silane functional groups. More specifically, the hydroxyl groups of the acrylic polyol can form crosslinks with the silane functional groups of the siloxane polymer through a hydrosilylation reaction. This hydrosilylation reaction can be carried out rapidly even at relatively low temperatures (for example, around 60°C) under a Pt-based catalyst. Therefore, by employing a polymer matrix that can be rapidly crosslinked even at relatively low temperatures as a support for the photopolymer layer, the manufacturing efficiency and productivity of holographic recording media can be improved.

[0031] The polymer matrix, with its flexible main chain of siloxane polymer, can enhance the mobility of components contained in the photopolymer layer (e.g., photoreactive monomers or plasticizers). Furthermore, the siloxane bonds, which have excellent heat resistance and moisture resistance, facilitate the assurance of reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium containing it.

[0032] The polymer matrix may have a relatively low refractive index, thereby playing a role in enhancing the refractive index modulation of the photopolymer layer. For example, the upper limit of the refractive index of the polymer matrix may be 1.53 or less, 1.52 or less, 1.51 or less, 1.50 or less, or 1.49 or less. The lower limit of the refractive index of the polymer matrix may be, for example, 1.40 or more, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more. In this specification, "refractive index" may be a value measured with an Abbe refractometer at 25°C.

[0033] The photopolymer layer includes a polymer matrix formed by crosslinking a siloxane-based polymer containing the silane functional group described above and an acrylic polyol, but may also include a polymer matrix precursor that is not partially crosslinked. In this case, the polymer matrix precursor can mean a siloxane-based polymer, an acrylic polyol, and a Pt-based catalyst.

[0034] The siloxane polymer may, for example, include a repeating unit represented by the following chemical formula 1 (Chemical Formula 1) and a terminal group represented by the following chemical formula 2 (Chemical Formula 2).

[0035] [ka]

[0036] In the aforementioned chemical formula 1, Multiple R 1 and R 2 These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. n is an integer between 1 and 10,000.

[0037] [ka]

[0038] In the aforementioned chemical formula 2, Multiple R 11 ~R 13 These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. At least one repeating unit of the repeating unit represented by chemical formula 1, and one of the terminal groups of the terminal groups represented by chemical formula 2, R 1 , R 2 and R 11 ~R 13 At least one of them is hydrogen.

[0039] In Chemical Formula 2, -(O)- means that when Si of the terminal group represented by Chemical Formula 2 binds to the repeating unit represented by Chemical Formula 1, it binds through oxygen (O) or binds directly without oxygen (O).

[0040] As used herein, an "alkyl group" may be a straight-chain, branched-chain or cyclic alkyl group. By way of non-limiting example, as used herein, an "alkyl group" 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.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), and the like.

[0041] As an example, R in Chemical Formulas 1 and 2 1 , R 2 and R 11 ~R 13 are methyl or hydrogen, and at least two of the plurality of R 1 , R 2 and R 11 ~R 13 may be hydrogen. More specifically, as the siloxane polymer, R 1 and R 2 in Chemical Formula 1 are methyl and hydrogen, respectively, and R 11 ~R 13Compounds in which each is independently methyl or hydrogen (for example, polymethylhydrosiloxanes whose terminal group is a trimethylsilyl group or a dimethylhydrosilyl group); R of part of the above chemical formula 1 1 and R 2 These are methyl and hydrogen, respectively, and the remaining R 1 and R 2 All are methyl, and R of the above chemical formula 2 11 ~R 13 Compounds in which each is independently methyl or hydrogen (for example, poly(dimethylsiloxane-co-methylhydrosiloxane) whose terminal group is a trimethylsilyl group or a dimethylhydrosilyl group; or R of the above chemical formula 1) 1 and R 2 All are methyl, and R of the above chemical formula 2 11 ~R 13 The compound may be one in which at least one of the terminal groups is hydrogen, and the rest are independently methyl or hydrogen (for example, a polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0042] The siloxane-based compound may, for example, have a number-average molecular weight (Mn) in the range of 200 to 4,000. Specifically, the lower limit of the number-average molecular weight of the siloxane-based polymer may be, for example, 200 or more, 250 or more, 300 or more, or 350 or more, and the upper limit may be, for example, 3,500 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less. When the number-average molecular weight of the siloxane-based polymer satisfies the above range, the holographic recording medium can exhibit excellent optical recording properties and heat and humidity resistance by preventing problems such as the siloxane-based polymer volatilizing and the matrix crosslinking degree decreasing during the crosslinking process with the acrylic polyol carried out at room temperature or above, or the siloxane-based polymer having poor compatibility with other components of the photopolymer layer and resulting in phase separation with such components.

[0043] The aforementioned number-average molecular weight refers to the number-average molecular weight (unit: g / mol) on a polystyrene basis, measured by the GPC method. In the process of measuring the polystyrene-based number-average molecular weight measured by the GPC method, commonly known analytical instruments, detectors such as differential index detectors, and analytical columns can be used, and commonly applied temperature conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30°C, tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0044] The silane functional group (Si-H) equivalent of the siloxane polymer may be, for example, in the range of 30 g / equivalent to 200 g / equivalent. More specifically, the silane functional group (Si-H) equivalent of the siloxane polymer may be 50 g / equivalent or more, 60 g / equivalent or more, 70 g / equivalent or more, 80 g / equivalent or more, or 90 g / equivalent or more, and 180 g / equivalent or less, or 150 g / equivalent or less.

[0045] In this specification, "equivalent weight of a functional group" is an abbreviation for the number of g equivalents (sometimes called equivalent weight) expressed in units of g / equivalent, and means the value obtained by dividing the molecular weight (such as weight-average molecular weight or number-average molecular weight) of the molecule or polymer containing the functional group by the number of the functional group. Therefore, the smaller the equivalent value, the higher the density of the functional group, and the larger the equivalent value, the lower the density of the functional group.

[0046] When the silane functional group equivalent of the siloxane polymer satisfies the above range, the polymer matrix has an appropriate crosslinking density and fully performs its role as a support, improving the fluidity of the components contained in the photopolymer layer, and without the problem of the diffraction grating interface collapsing after recording, the initial refractive index modulation value can be maintained at an excellent level even after time has passed, minimizing the decrease in recording characteristics for optical information.

[0047] The aforementioned acrylic polyol can mean a polymer in which one or more, specifically two or more hydroxyl groups are bonded to the main chain or side chain of an acrylate polymer. In this specification, unless otherwise specified, "acrylic" refers to one or more selected from acryloyl groups, methacryloyl groups and their derivatives, or to repeating units formed by the polymerization thereof, and unless otherwise specified, "acrylate" refers to one or more selected from acrylate and methacrylate, or to repeating units formed by the polymerization thereof.

[0048] The acrylic polyol may be a homopolymer of acrylate monomers having hydroxyl groups, a copolymer of acrylate monomers having two or more hydroxyl groups, or a copolymer of acrylate monomers having hydroxyl groups and acrylate monomers not having hydroxyl groups. In this specification, unless otherwise specified, "copolymer" is a term that encompasses random copolymers, block copolymers, and graft copolymers.

[0049] Examples of acrylate monomers having a hydroxyl group include hydroxyalkyl (meth)acrylate or hydroxyaryl (meth)acrylate, where the alkyl is an alkyl having 1 to 30 carbon atoms, and the aryl may be an aryl having 6 to 30 carbon atoms. Examples of acrylate monomers not having a hydroxyl group include alkyl (meth)acrylate or aryl (meth)acrylate, where the alkyl is an alkyl having 1 to 30 carbon atoms, and the aryl may be an aryl having 6 to 30 carbon atoms. In this specification, "(meth)acrylate" refers to acrylate and / or methacrylate unless otherwise specified.

[0050] The acrylic polyol may, for example, have a weight-average molecular weight (Mw) in the range of 150,000 to 1,000,000. The weight-average molecular weight refers to the weight-average molecular weight in polystyrene terms, measured by the GPC method as described above. The lower limit of the weight-average molecular weight may be, for example, 150,000 or more, 200,000 or more, or 250,000 or more. The upper limit of the weight-average molecular weight 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 450,000 or less. When the weight-average molecular weight of the acrylic polyol satisfies the aforementioned range, the polymer matrix fully performs its function as a support, resulting in minimal decrease in recording characteristics for optical information even after extended use. This provides the polymer matrix with sufficient flexibility, improving the fluidity (mobility) of components contained in the photopolymer layer (e.g., photoreactive monomers or plasticizers), thereby minimizing the decrease in recording characteristics for optical information.

[0051] In order to adjust the crosslinking density of the acrylic polyol by the siloxane polymer to a level advantageous for ensuring the functionality of the holographic recording medium, the hydroxyl group equivalent of the acrylic polyol can be adjusted to an appropriate level.

[0052] Specifically, the hydroxyl group (-OH) equivalent of the acrylic polyol may be, for example, in the range of 500 g / equivalent to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl group (-OH) equivalent of the acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. Furthermore, the upper limit of the hydroxyl group (-OH) equivalent of the acrylic polyol may be 2900 g / equivalent or less, 2800 g / equivalent or less, 2700 g / equivalent or less, 2600 g / equivalent or less, 2500 g / equivalent or less, 2400 g / equivalent or less, 2300 g / equivalent or less, 2200 g / equivalent or less, 2100 g / equivalent or less, 2000 g / equivalent or less, or 1900 g / equivalent or less.

[0053] When the hydroxyl group (-OH) equivalent of the acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslinking density and fully performs its role as a support, improving the fluidity of the components contained in the photopolymer layer. This prevents the breakdown of the diffraction grating interface after recording, maintains the initial refractive index modulation value at an excellent level even after time has passed, and minimizes the decrease in recording characteristics for optical information.

[0054] The acrylic polyol may have a glass transition temperature (Tg) in the range of -60°C to -10°C, for example. Specifically, the lower limit of the glass transition temperature may be, for example, -55°C or higher, -50°C or higher, -45°C or higher, -40°C or higher, -35°C or higher, -30°C or higher, or -25°C or higher. The upper limit of the glass transition temperature may be, for example, -15°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, or -35°C or lower. When the glass transition temperature range is satisfied, the glass transition temperature can be lowered without significantly reducing the modulus of the polymer matrix, thereby increasing the mobility (fluidity) of other components in the photopolymer layer and improving the moldability of the photopolymer composition. The glass transition temperature can be measured using known methods, such as DSC (Differential Scanning Calorimetry) or DMA (dynamic mechanical analysis).

[0055] 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. The upper limit of the refractive index of the acrylic polyol may be, for example, 1.49 or less, 1.48 or less, 1.47 or less, 1.46 or less, or 1.45 or less. When the acrylic polyol has a refractive index within the range described above, it can contribute to enhancing refractive index modulation. The refractive index of the acrylic polyol is a theoretical refractive index and can be calculated using the refractive index of the monomers used in the production of the acrylic polyol (value measured using an Abbe refractometer at 25°C) and the fraction (molar ratio) of each monomer.

[0056] The acrylic polyol and siloxane polymer may be included in such a way 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 1.5 to 4.

[0057] The molar ratio of silane functional groups of a siloxane polymer to the hydroxyl groups of the acrylic polyol (hereinafter abbreviated as the SiH / OH molar ratio) can be calculated from the weight of each polymer and the number of moles of the functional group confirmed from the equivalent amount of the functional group in each polymer.

[0058] Specifically, the silane functional group equivalent of a siloxane polymer is the value obtained by dividing the molecular weight (e.g., number-average molecular weight) of the siloxane polymer by the number of silane functional groups per molecule, and the hydroxyl group equivalent of an acrylic polyol is the value obtained by dividing the molecular weight (e.g., weight-average molecular weight) of the acrylic polyol by the number of hydroxyl functional groups per molecule. Therefore, by dividing the weight of a siloxane polymer by the silane functional group equivalent of the siloxane polymer, the number of moles of silane functional groups can be determined, and by dividing the weight of an acrylic polyol by the hydroxyl group equivalent of the acrylic polyol, the number of moles of hydroxyl groups can be determined. More specifically, taking Example 1 described below as an example, dividing the weight of the siloxane polymer used in Example 1 (2.5 g) by the silane functional group equivalent of the siloxane polymer used in Example 1 (103 g / equivanlent) gives the number of moles of silane functional groups (0.024 mol). Dividing the weight of the acrylic polyol used in Example 1 (21.5 g) by the hydroxyl group equivalent of the acrylic polyol used in Example 1 (1802 g / equivanlent) gives the number of moles of hydroxyl groups (0.012 mol). Dividing the thus calculated number of moles of silane functional groups (0.024 mol) by the number of moles of hydroxyl groups (0.012 mol) confirms that the SiH / OH molar ratio is calculated as 2.

[0059] The lower limit of the SiH / OH molar ratio may be, for example, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, or 2.0 or more. The upper limit of the SiH / OH molar ratio may be, for example, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, or 3.5 or less. When the range of the SiH / OH molar ratio is satisfied, the polymer matrix is ​​crosslinked with an appropriate crosslinking density, improving the fluidity of recording components (e.g., photoreactive monomers and plasticizers, etc.) and ensuring excellent optical recording properties. Even when placed in a high temperature / high humidity environment after recording, the migration, deformation, or penetration of moisture into the photopolymer layer of components in the photopolymer layer is suppressed, resulting in excellent heat and humidity resistance and transparent optical properties.

[0060] The Pt-based catalyst may, for example, be Karstedt's catalyst. The Pt-based catalyst may be present in an amount of 0.01 to 2 parts by weight per 100 parts by weight of the acrylic polyol. Specifically, the Pt-based catalyst may be present in an amount of 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, 0.05 parts by weight or more, or 0.06 parts by weight or more per 100 parts by weight of the acrylic polyol. The Pt-based catalyst may also be present in an amount of 1.5 parts by weight or less, 1.0 part by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, 0.15 parts by weight or less, 0.14 parts by weight or less, 0.13 parts by weight or less, or 0.12 parts by weight or less per 100 parts by weight of the acrylic polyol. When the Pt-based catalyst is used in the above-mentioned amounts, the polymer matrix can be crosslinked with an appropriate crosslinking density to exhibit the desired optical recording characteristics.

[0061] The polymer matrix precursor may optionally contain, in addition to the Pt-based catalyst, other non-metallic catalysts such as rhodium-based, iridium-based, rhenium-based, molybdenum-based, iron-based, nickel-based, alkali metal or alkaline earth metal-based, Lewis acid-based, or carbene-based catalysts.

[0062] On the other hand, in the holographic recording medium of the above embodiment, optical information can be recorded by irradiating the photopolymer layer with object light and reference light. Depending on the interference length of the object light and reference light, photopolymerization of photoreactive monomers does not occur in the canceling interference region, while photopolymerization of photoreactive monomers occurs in the reinforcement interference region. As the photoreactive monomers are continuously consumed in the reinforcement interference region, a concentration difference between the photoreactive monomers in the canceling interference region and the reinforcement interference region is created, and as a result, the photoreactive monomers in the canceling interference region diffuse into the reinforcement interference region. A diffraction grating is generated by the refractive index modulation that occurs in this way.

[0063] Therefore, in order to achieve the refractive index modulation described above, the photoreactive monomer may include compounds having a higher refractive index than the polymer matrix. However, it is not limited to all photoreactive monomers having a higher refractive index than the polymer matrix; at least some photoreactive monomers may have a higher refractive index than the polymer matrix in order to achieve a high refractive index modulation value. For example, the photoreactive monomer may include monomers with refractive indices of 1.50 or higher, 1.51 or higher, 1.52 or higher, 1.53 or higher, 1.54 or higher, 1.55 or higher, 1.56 or higher, 1.57 or higher, 1.58 or higher, 1.59 or higher, or 1.60 or higher. The upper limit of the refractive index of the monomers included in the photoreactive monomer is not particularly limited and may be, for example, 1.70 or lower.

[0064] In the holographic recording medium of the above embodiment, the photoreactive monomer may include 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.

[0065] The ratio of monofunctional monomers within the photoreactive monomer is closely related to the compatibility of the materials constituting the photopolymer layer. Specifically, the weight ratio of monofunctional monomers to the total weight of the photoreactive monomer can be adjusted from 30% to 68% by weight. More specifically, the weight ratio of monofunctional monomers to the total weight of the photoreactive monomer may be, for example, 30% or more by weight, 31% or more by weight, 32% or more by weight, 33% or more by weight, 34% or more by weight, 35% or more by weight, 36% or more by weight, 37% or more by weight, 38% or more by weight, 39% or more by weight, 40% or more by weight, 41% or more by weight, 42% or more by weight, 43% or more by weight, 44% or more by weight, or 45% or more by weight. The weight ratio of monofunctional monomers to the total weight of the photoreactive monomer may also be, for example, 68% or less by weight, 67% or less by weight, 66% or less by weight, 65% or less by weight, 64% or less by weight, or 63% or less by weight. If the weight ratio of the monofunctional monomer is below the range, the compatibility of the materials constituting the photopolymer layer is poor, which can lead to problems such as a high elemental ratio of fluorine on the surface of the photopolymer layer and increased haze of the hologram recording medium. Furthermore, if the weight ratio of the monofunctional monomer exceeds the range, the degree of crosslinking of the photopolymer layer decreases, which can lead to increased tackiness and a deterioration in optical recording characteristics.

[0066] The aforementioned monofunctional monomer may include monofunctional (meth)acrylates with a molecular weight of 85 to 500. Specifically, the monofunctional monomer may include, for example, one or more selected from the group consisting of benzyl (meth)acrylate (Miwon M1182 refractive index 1.5140), benzyl 2-phenyl acrylate, phenoxybenzyl (meth)acrylate (Miwon M1122 refractive index 1.565), phenol (ethylene oxide) (meth)acrylate (phenol(EO)(meth)acrylate; Miwon M140 refractive index 1.516), phenol (ethylene oxide) 2 (meth)acrylate (phenol(EO)2(meth)acrylate; Miwon M142 refractive index 1.510), O-phenylphenol (ethylene oxide) (meth)acrylate (O-phenylphenol(EO)(meth)acrylate; Miwon M1142 refractive index 1.577), phenylthioethyl (meth)acrylate (Miwon M1162 refractive index 1.560), and biphenylmethyl (meth)acrylate.

[0067] The aforementioned polyfunctional monomer is, for example, bisphenol A (ethylene oxide) 2~10 Di(meth)acrylate (bisphenol A(EO) 2~10(meth)acrylate; Miwon's M240 refractive index 1.537, M241 refractive index 1.529, M244 refractive index 1.545, M245 refractive index 1.537, M249 refractive index 1.542, M2100 refractive index 1.516, M2101 refractive index 1.512), Bisphenol A epoxy di(meth)acrylate (Miwon's PE210 refractive index 1.557, PE2120A refractive index 1.533, PE2120B refractive index 1.534, PE2020C refractive index 1.539, PE2120S refractive index 1.556), Bisful Orange (meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR604 It may contain one or more substances selected from the group consisting of (2 refractive index 1.600), modified bisphenol full orange (meth)acrylate (Miwon's HR6060 refractive index 1.584, HR6100 refractive index 1.562, HR6200 refractive index 1.530), tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate (Miwon's M370 refractive index 1.508), phenol novolac epoxy (meth)acrylate (Miwon's SC6300 refractive index 1.525), and cresol novolac epoxy (meth)acrylate (Miwon's SC6400 refractive index 1.522, SC6400C refractive index 1.522).

[0068] The photopolymer layer may contain 50 to 300 parts by weight of a photoreactive monomer per 100 parts by weight of the polymer matrix. The lower limit of the photoreactive monomer content may be, for example, 50 parts by weight or more, 70 parts by weight or more, 100 parts by weight or more, or 110 parts by weight or more. The upper limit of the photoreactive monomer content may be, for example, 300 parts by weight or less, 290 parts by weight or less, 280 parts by weight or less, or 270 parts by weight or less.

[0069] In this case, the standard polymer matrix content refers to the combined content (by weight) of acrylic polyols and siloxane polymers that form the matrix.

[0070] When the above range is met, a photopolymer layer exhibiting excellent optical recording characteristics, heat resistance, heat and humidity resistance, and high transparency can be provided.

[0071] The photopolymer layer includes a photoinitiator system. The photoinitiator system can mean a combination of a photoinitiator or photosensitizer and a coinitiator that enables polymerization to be initiated by light.

[0072] The aforementioned photopolymer layer may include a photosensitizer and a co-initiator as a photoinitiator system.

[0073] For example, a photosensitive dye can be used as the photosensitizer. Specifically, the photosensitive dyes include, for example, silicon rhodamine compounds, sulfonium derivatives of ceramidenin, new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose bengal, thionine, basic yellow, pinacyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, Quinaldine Red, crystal violet, and brilliant green. One or more dyes selected from the group consisting of Green, Astrazon Orange G, Darrow Red, Pyronin Y, Basic Red 29, Pyrylium I (pyrylium iodide), Safranin O, Cyanine, Methylene Blue, Azure A, and BODIPY can be used. As the cyanine dye, for example, Cy3 and Cy5 (H-Nu640, Spectra) can be used.

[0074] The photopolymer layer may contain the photosensitive dye in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the photosensitive dye content may be, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more. The upper limit of the photosensitive dye content may be, for example, 5 parts by weight or less. When the above ranges are met, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording characteristics.

[0075] The co-initiator may be an electron donor, an electron acceptor, or a mixture thereof.

[0076] As an example, the photopolymer composition of the above embodiment may contain an electron donor as a co-initiator. The electron donor may, for example, include a borate anion represented by the following chemical formula 3 (Chemical Formula 3).

[0077] [ka]

[0078] In the aforementioned chemical formula 3, X 1 ~X 4 Each of these is independently a substituted or unsubstituted C1-C20 alkyl group, a C2-C20 alkenyl group, a C6-C30 aryl group, a C7-C30 arylalkyl (arylalkyl) group, a C7-C30 alkylaryl (alkylaryl) group, or an allyl group, and X 1 ~X 4 At least one of them is not an aryl group.

[0079] When the C1-C20 alkyl group, C2-C20 alkenyl group, C6-C30 aryl group, C7-C30 arylalkyl (arylalkyl) group, C7-C30 alkylaryl (alkylaryl) group, or allyl group is substituted, it may be substituted with one or more selected from the group consisting of halogens, vinyl groups, C1-C5 haloalkyl groups, and C1-C5 alkoxy groups.

[0080] Specifically, X 1 ~X 3 Each of these is independently a phenyl, methylphenyl, naphthyl, or methylnaphthyl substituted or unsubstituted with one or more substituents selected from the group consisting of halogens, vinyl groups, trifluoromethyl groups, and methoxy groups, and X 4 This may be a linear alkyl group having 1 to 12 carbon atoms.

[0081] More specifically, the borate anion represented by chemical formula 3 may be one or more selected from the group consisting of borate anions represented by the following chemical formulas 3-1 (Chemical Formula 4) and 3-2 (Chemical Formula 5).

[0082] [ka]

[0083] In the aforementioned chemical formula 3-1, R 102 These are, independently, methyl or halogen, R 103 Each is independently of hydrogen, methyl, or halogen, and adjacent to R 102 If it is methyl, it is a halogen, X 4’ These are linear alkyl groups having 1 to 12 carbon atoms.

[0084] [ka]

[0085] In the aforementioned chemical formula 3-2, R 106 These are, independently, hydrogen, methyl, or halogen. X 4” These are linear alkyl groups having 1 to 12 carbon atoms.

[0086] In the above chemical formula 4-2, R 106 Each of these elements is independently hydrogen, methyl, or halogen, and at least one of them may be a halogen.

[0087] When using borate anions represented by chemical formulas 3-1 and 3-2 below as the electron donor, excellent heat resistance can be ensured even before recording.

[0088] In the chemical formulas 3-1 and 3-2, the halogen may be fluorine or chlorine. In particular, chlorine can ensure even better heat resistance.

[0089] The cation bonded to the borate anion is one or more cations selected from the group consisting of alkali metal cations, quaternary ammonium cations, and nitrogen-containing heterocyclic cations, and does not absorb light.

[0090] The alkali metal cation may be one or more selected from the group consisting of, for example, lithium, sodium, potassium, rubidium, and cesium.

[0091] The quaternary ammonium cation may be an ammonium cation in which nitrogen (N) is substituted with four substituents, or a cyclic ammonium cation in which two substituents substituted with nitrogen are linked together, or a mixture thereof.

[0092] Specifically, the quaternary ammonium cation may be a cation represented by the following chemical formula 3-3 (Chemical Formula 6).

[0093] [ka]

[0094] In the above chemical formula 3-3, Y 1 ~Y 4 Two of the substituents may or may not be linked to each other to form an aliphatic ring having 4 to 10 carbon atoms. Y that does not form an aliphatic ring 1 ~Y 4 Each of these is independently an alkyl group having 1 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 6 to 40 carbon atoms, or an alkyl group having 2 to 40 carbon atoms linked via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3), Y 1 ~Y 4 If all substituents are methyl groups, or if two or more substituents are alkyl groups with 16 or more carbon atoms, then it is excluded.

[0095] In the above chemical formula 3-3, Y 1 ~Y 4 If all substituents are methyl groups, or if two or more substituents are alkyl groups having 16 or more carbon atoms, the electron donor may not dissolve well in the photopolymer composition and may not exhibit the desired optical recording properties.

[0096] Specifically, Y 1 ~Y 4 Two of the substituents can be linked together to form a piperidine or pyrrolidine.

[0097] The aforementioned Y 1 ~Y 4 Among these substituents that do not form an aliphatic ring, each may independently be a linear alkyl group having 1 to 32 carbon atoms, a phenyl group, a benzyl group, or -CH2CH2-O-CO-CH2CH2CH3. More specifically, the Y 1 ~Y 4The substituents that do not form an aliphatic ring may independently be a methyl group, a butyl group, a hexadecyl group, a hentriacontyl group, a phenyl group, or a benzyl group.

[0098] The nitrogen-containing heterocyclic cation may also be a heteroaromatic cation containing one or more nitrogen atoms. Examples of such heteroaromatic cations include pyrrole, pyrazole, imidazole, or pyridine cations, and these hydrogen atoms may be substituted or unsubstituted.

[0099] As an example, the nitrogen-containing heterocyclic cation may be a cation represented by the following chemical formula 3-4 (Chemical Formula 7).

[0100] [ka]

[0101] In the above chemical formulas 3 and 4, R 107 , R 109 and R 110 These are, independently, hydrogen, a C1-C40 alkyl group, a C6-C30 aryl group, a C6-C40 arylalkyl group, or a C2-C40 alkyl group linked via an ester bond (e.g., -CH2CH2-O-CO-CH2CH2CH3), R 108 and R 111 These are, independently, C1-C40 alkyl groups, C6-C30 aryl groups, C6-C40 arylalkyl groups, or C2-C40 alkyl groups linked via ester bonds (e.g., -CH2CH2-O-CO-CH2CH2CH3).

[0102] Specifically, R 107 , R 109 and R 110 Each of these may independently be hydrogen or an aryl group having 6 to 30 carbon atoms. More specifically, R 107 , R 109 and R110 Each of these may independently be a hydrogen atom or a phenyl group.

[0103] Specifically, the aforementioned R 108 and R 111 R may be a linear alkyl group having 1 to 40 carbon atoms or an arylalkyl group having 6 to 40 carbon atoms. More specifically, the R 108 and R 111 This may be a hexadecyl group or a benzyl group.

[0104] The cation bonded to the borate anion may include, for example, one or more selected from the group consisting of tetrabutylammonium cation, hexadecyldimethylbenzylammonium cation, hentriacontyldimethylbenzylammonium cation, hexadecylbenzylpiperidinium cation, hexadecylbenzylpyrrolidinium cation, 1-hexadecyl-3-benzylimidazolium cation, and 1,3-dihexadecyl-2-phenylimidazolium cation.

[0105] However, the cations bound to the borate anion are not limited to those described above. Even if a cation exhibits low solubility when present alone, if it can achieve appropriate solubility when mixed with the cations described above, some of the cations described above may be substituted with other cations known in the relevant art. As a non-limiting example, some of the cations described above may be substituted with 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium, for example.

[0106] As an example, the photopolymer layer may contain an electron acceptor as a co-initiator. The electron acceptor may include, for example, onium salts such as sulfonium salts and iodonium salts; triazine compounds such as tris(trihalomethyl)triazine and substituted bis(trihalomethyl)triazine; or mixtures thereof.

[0107] As an example, the electron acceptor may include (4-(octyloxy)phenyl)(phenyl)iodonium salt as an iodonium salt, or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine as a triazine compound. For example, commercially available H-Nu254 (Spectra) or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (TCI) can be used as the electron acceptor.

[0108] The photopolymer layer may contain the co-initiator in an amount ranging from 0.05 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the co-initiator content may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more. The upper limit of the co-initiator content may be, for example, 5 parts by weight or less. When the above range is satisfied, it is advantageous to exhibit an appropriate polymerization reaction rate and ensure the desired optical recording characteristics.

[0109] The photoinitiator system may include additional photoinitiators to remove the color of the photosensitive dye and to react all unreacted photoreactive monomers after light irradiation for recording. Examples of the photoinitiators include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, amine derivatives, diazonium salts, sulfonium salts, iodonium salts, sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl)iron(II), benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosylphthalimide, or mixtures thereof. More specifically, the photoinitiators include 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, and 2,2-dimethoxy-1,2-diphenylethane-1-one.2-diphenylethane-1-one (Product name: Irgacure 651 / Manufacturer: BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (Product name: Irgacure 184 / Manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1 -butanone-1) (Product name: Irgacure369 / Manufacturer: BASF), bis(η5-2,4-cyclopentadiene-1-yl)bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium) (Product name: Irgacure784 / Manufacturer: BASF), Ebecryl Examples include, but are not limited to, P-115 (manufacturer: SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (manufacturer: Dow Chemical Co. in USA), Irgacure 264, Irgacure 250 (manufacturer: BASF), CIT-1682 (manufacturer: Nippon Soda), or mixtures thereof.

[0110] The photopolymer layer may contain the photoinitiator in an amount ranging from 0.05 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the photoinitiator content may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more. The upper limit of the photoinitiator content may be, for example, 5 parts by weight or less. When the above ranges are met, after recording optical information on the photopolymer layer, the reaction of the photoreactive monomer can be effectively terminated, the color of the photosensitive dye can be decolorized, and a transparent holographic recording medium can be provided.

[0111] The photopolymer layer contains a fluorine-based compound as a plasticizer. The plasticizer allows for easier refractive index modulation during the manufacturing of the holographic recording medium.

[0112] More specifically, plasticizers lower the glass transition temperature of the polymer matrix, thereby improving the fluidity of photoreactive monomers. It has a low refractive index and non-reactive properties and is uniformly distributed within the polymer matrix. When photoreactive monomers that have not been photopolymerized move, they can move in the opposite direction and contribute to refractive index modulation.

[0113] Furthermore, plasticizers can also contribute to improving the moldability of photopolymer compositions.

[0114] The fluorine-based compound may have a low refractive index of 1.45 or less in order to exhibit the plasticizer function described above. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less. The lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. By using a fluorine-based compound having a lower refractive index than the photoreactive monomer described above, the refractive index of the polymer matrix can be made even lower, and the refractive index modulation by the photoreactive monomer can be made larger.

[0115] The fluorinated compound may, for example, include one or more functional groups selected from the group consisting of ether groups, ester groups, and amide groups, and two or more difluoromethylene groups. More specifically, the fluorinated compound may, as an example, be a compound containing a repeating unit represented by the following chemical formula 4 (Chemical Formula 8).

[0116] [ka]

[0117] In the above Chemical Formula 4, the plurality of R 31 ~R 34 are each independently hydrogen or fluorine, and at least one of R 31 ~R 34 is fluorine, and m is an integer from 2 to 12.

[0118] More specifically, the fluorine-based compound may be a compound containing 1 to 3 units represented by the following Chemical Formula 4-1 (Chemical Formula 9).

[0119]

Chemical Formula

[0120] In the above Chemical Formula 4-1, R 41 ~R 44 and R 53 ~R 56 are each independently hydrogen or fluorine, and R 45 ~R 52 is fluorine.

[0121] As an example, in the above Chemical Formula 4-1, R 41 , R 42 , R 55 and R 56 are hydrogen, and R 43 ~R 54 is fluorine.

[0122] Fluorine compounds containing the (repeating) units represented by chemical formulas 4 and 4-1 are not particularly limited, but can be capped with end capping agents widely used in the relevant art. For example, the end of a fluorine compound containing the (repeating) units represented by chemical formulas 4 and 4-1 may be an alkyl group or an alkyl group substituted with one or more alkoxys. As a non-limiting example, the end of a fluorine compound containing the (repeating) units represented by chemical formulas 4 and 4-1 may be a 2-methoxyethoxymethyl group using 2-methoxyethoxymethyl chloride as the end capping agent.

[0123] The fluorinated compound may have a weight-average molecular weight of 300 or more. Specifically, the lower limit of the weight-average molecular weight of the fluorinated compound may be, for example, 350 or more, 400 or more, 450 or more, 500 or more, or 550 or more. The upper limit of the weight-average molecular weight of the fluorinated compound may be, for example, 1000 or less, 900 or less, 800 or less, 700 or less, or 600 or less. When considering refractive index modulation, compatibility with other components, and the elution of the fluorinated compound, it is preferable to satisfy the above range of weight-average molecular weight. In this case, the weight-average molecular weight refers to the weight-average molecular weight in polystyrene terms measured by the GPC method as described above.

[0124] The photopolymer layer may contain 20 to 200 parts by weight of the fluorine-based compound per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the fluorine-based compound content may be, for example, 25 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, or 70 parts by weight or more. The upper limit of the fluorine-based compound content may be, for example, 190 parts by weight or less, 180 parts by weight or less, 170 parts by weight or less, 160 parts by weight or less, or 155 parts by weight or less. When the above range is met, it is possible to show a large refractive index modulation value after recording by a fluorine-based compound with a sufficiently low refractive index without problems such as poor compatibility with the components contained in the photopolymer layer causing some of the fluorine-based compound to dissolve onto the surface of the photopolymer layer or poor haze, which is advantageous in ensuring excellent optical recording characteristics.

[0125] The majority of the components of the photopolymer layer can be said to be a polymer matrix, a photoreactive monomer, and a fluorinated compound. Therefore, the elemental composition ratio of the surface of the photopolymer layer can be controlled by the blending ratio of the polymer matrix, the photoreactive monomer, and the fluorinated compound. In order to satisfy the elemental composition ratio described above, the photopolymer layer can contain 17% to 38% by weight of the polymer matrix, 38% to 58% by weight of the photoreactive monomer, and 17% to 38% by weight of the fluorinated compound, relative to the total weight of the polymer matrix, the photoreactive monomer, and the fluorinated compound.

[0126] More specifically, the polymer matrix may be present in, for example, 17% or more by weight, 18% or more by weight, 19% or more by weight, or 20% or more by weight. The polymer matrix may be present in, for example, 38% or less by weight, 37% or less by weight, or 36% or less by weight. The photoreactive monomer may be present in, for example, 38% or more by weight, 39% or more by weight, 40% or more by weight, 41% or more by weight, or 42% or more by weight. The photoreactive monomer may be present in, for example, 58% or less by weight, 55% or less by weight, or 53% or less by weight. The fluorine-based compound may be present in, for example, 17% or more by weight, 18% or more by weight, 19% or more by weight, or 20% or more by weight. The fluorine-based compound may be present in, for example, 38% or less by weight, 35% or less by weight, 33% or less by weight, or 32% or less by weight. A photopolymer layer satisfying the above-mentioned elemental composition ratio can be provided within such ranges.

[0127] The photopolymer layer may additionally contain additives such as surfactants or defoaming agents.

[0128] The photopolymer layer may include a silicone-based surfactant, a fluorine-based surfactant, or a mixture thereof as a surfactant.

[0129] Examples of the aforementioned silicone-based surfactants include BYK-077, BYK-085, BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-320, BYK-322, BYK-323, BYK-325, BYK-330, BYK-331, BYK-333, BYK-335, BYK-341v344, BYK-345v346, BYK-348, BYK-354, BYK-355, BYK-356, BYK-358, BYK-361, BYK-370, BYK-371, BYK-375, BYK-380, BYK-390, and BYK-3550 from BYK Chemie. The aforementioned fluorine-based surfactants include DIC (DaiNippon Ink & Chemicals) F-114, F-177, F-410, F-411, F-450, F-493, F-494, F-443, F-444, F-445, F-446, F-470, F-471, F-472SF, F-474, F-475, F-477, F-478, F-479, F-480SF, F-482, F-483, F-484, F -486, F-487, F-172D, MCF-350SF, TF-1025SF, TF-1117SF, TF-1026SF, TF-1128, TF-1127, TF1129, TF-1126, TF-1130, TF-1116SF, TF-1131, TF1132, TF1027SF, TF-1441, TF-1442, etc. can be used.

[0130] If the photopolymer layer contains a surfactant, the surfactant may be present in amounts of 0.01 parts by weight or more, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more and 5 parts by weight or less, or 3 parts by weight or less, per 100 parts by weight of the polymer matrix. When these ranges are met, the photopolymer layer can be given excellent adhesion and release properties, thereby preserving excellent optical recording characteristics.

[0131] The photopolymer layer may contain a silicone-based reactive additive as an antifoaming agent. A commercially available silicone-based reactive additive, such as Tego Rad 2500, can be used. The amount of the antifoaming agent can be appropriately adjusted to a level that does not interfere with the function of the holographic recording medium.

[0132] The aforementioned photopolymer layer may be formed from a photopolymer composition containing a solvent.

[0133] The solvent may be an organic solvent, or, as an example, one or more organic solvents selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited thereto. Specific examples of such organic solvents include ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; and one or more ethers selected from the group consisting of tetrahydrofuran or propylene glycol monomethyl ether.

[0134] The organic solvent may be added at the time when each component of the photopolymer composition is mixed, or it may be added to the photopolymer composition while each component is dispersed or mixed in the organic solvent.

[0135] The photopolymer composition may contain a solvent such that the solid content concentration is 1% to 90% by weight. Specifically, the photopolymer composition may contain a solvent such that the solid content concentration is 20% or more by weight, 25% or more by weight, or 30% or more by weight, and 50% or less by weight, 45% or less by weight, or 40% or less by weight. Within this range, the photopolymer composition can exhibit appropriate fluidity, form a coating film without defects such as stripes, and form a photopolymer layer that exhibits desired physical properties and surface characteristics without defects occurring during the drying and curing process.

[0136] The holographic recording medium of the above embodiment exhibits excellent refractive index modulation, diffraction efficiency, and driving reliability despite having a thin photopolymer layer.

[0137] The thickness of the photopolymer layer may be, for example, in the range of 5.0 μm to 40.0 μm. Specifically, the lower limit of the thickness of the photopolymer layer may be, for example, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more. The upper limit of the thickness may be, for example, 35 μm or less, 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, 25 μm or less, 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, 19 μm or less, or 18 μm or less.

[0138] The holographic recording medium of the above embodiment may further include a substrate on at least one surface of the photopolymer layer. The type of substrate is not particularly limited, and any known in the relevant art can be used. For example, substrates such as glass, PET (polyethylene terephthalate), TAC (triacetyl cellulose), PC (polycarbonate), and COP (cycloolefin polymer) can be used.

[0139] The holographic recording medium of the above embodiment can have a high diffraction efficiency. For example, when a Notch filter hologram is recorded on the holographic recording medium, it can have a diffraction efficiency of 80% or more. In this case, the thickness of the photopolymer layer may be, for example, 5 μm to 30 μm. Specifically, when a Notch filter hologram is recorded, the diffraction efficiency may be 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, or 96% or more. For example, when a red dye or a green dye is used as the photosensitive dye and a Notch filter hologram is recorded, the diffraction efficiency may be, for example, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, or 96% or more. Thus, the holographic recording medium of the above embodiment can achieve excellent diffraction efficiency even when it includes a thin photopolymer layer. The diffraction efficiency can be measured by the method described in the test examples below.

[0140] On the other hand, holographic recording media tend to have opaque properties due to the incompatibility of components that mix components with low refractive indices and components with high refractive indices in order to record optical properties. However, the holographic recording media of the above embodiment can exhibit highly transparent optical properties by controlling the elemental ratio of fluorine on the surface of the photopolymer layer to a specific range.

[0141] As an example, the haze of the hologram recording medium may be 2% or less. The upper limit of the haze may be, for example, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, or 0.9% or less. The lower limit of the haze is not particularly limited and may be 0% or more. The haze can be measured by the method described in the test examples below.

[0142] The holographic recording medium of the above embodiment is expected to provide a variety of highly visible optical elements by exhibiting excellent optical recording characteristics and high transparency.

[0143] 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.

[0144] On the other hand, according to another embodiment of the invention, a method for manufacturing a hologram recording medium is provided, comprising the steps of: applying a photopolymer composition comprising a polymer matrix or its precursor formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol; a fluorine compound; a photoreactive monomer; and a photoinitiator system to form a photopolymer layer; and irradiating a predetermined area of ​​the photopolymer layer with a coherent laser to selectively polymerize the photoreactive monomer contained in the photopolymer layer to record optical information, wherein the elemental ratio of fluorine to the total amount of carbon, oxygen, fluorine, and silicon atoms, as confirmed by photoelectron spectroscopy for chemical analysis (ESCA) on the surface of the photopolymer layer, is 0.05 atomic% to 3 atomic%.

[0145] The photopolymer layer having the specific fluorine elemental composition ratio may be the photopolymer layer included in the holographic recording medium of the above-described embodiment, and since the photopolymer layer has been explained in detail earlier, a detailed explanation will be omitted here.

[0146] In the step of forming the photopolymer layer, a photopolymer composition containing the above-described configuration can first be manufactured. When manufacturing the photopolymer composition, any commonly known mixer, stirrer, or similar device can be used for mixing the components without any limitations. Such a mixing process may be carried out at temperatures in the range of 0°C to 100°C, 10°C to 80°C, or 20°C to 60°C.

[0147] In the step of forming the photopolymer layer, the prepared photopolymer composition can be applied to form a coating film made from the photopolymer composition. The coating film can be dried at a temperature of 50°C or higher, 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and 120°C or lower, 110°C or lower, 100°C or lower, or 90°C or lower. This process induces a hydrosilylation reaction between the hydroxyl groups of the unreacted acrylic polyol and the silane functional groups of the siloxane polymer, thereby achieving the desired crosslinking density while maintaining high transparency.

[0148] The photopolymer layer produced in the step of forming the photopolymer layer may have a fluorine-based compound, a photoreactive monomer, a photoinitiator system, and additives added as needed uniformly dispersed within the crosslinked polymer matrix.

[0149] Subsequently, when the photopolymer layer is irradiated with a coherent laser during the optical information recording stage, polymerization of photoreactive monomers occurs in regions where reinforcement interference occurs, forming a photopolymer. In regions where cancellation interference occurs, polymerization of photoreactive monomers does not occur or is suppressed, resulting in the presence of photoreactive monomers. The unreacted photoreactive monomers then diffuse towards the photopolymer side where the concentration of photoreactive monomers is lower, causing refractive index modulation, which generates a diffraction grating. As a result, a hologram, i.e., optical information, is recorded on the photopolymer layer having the diffraction grating.

[0150] The method for manufacturing a hologram recording medium according to the other embodiment described above may additionally include a step of photobleaching, in which the photopolymer layer on which the optical information is recorded is irradiated with light to bleach it, after the step of recording the optical information.

[0151] In the photobleaching step, ultraviolet light is irradiated onto the photopolymer layer on which optical information is recorded to terminate the reaction of photoreactive monomers remaining in the photopolymer layer and remove the color of the photosensitive dye. For example, in the photobleaching step, ultraviolet light (UVA) in the 320nm to 400nm range is irradiated to terminate the reaction of photoreactive monomers and remove the color of the photosensitive dye.

[0152] On the other hand, according to yet another embodiment of the invention, an optical element including the holographic recording medium is provided.

[0153] Specific examples of the optical elements include smart devices such as mobile devices, components for wearable displays, vehicle accessories (e.g., head-up displays), holographic fingerprint recognition systems, optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffraction members, light guides, waveguides, projection screens and / or masks, media and light diffusion plates for optical memory systems, optical wavelength dividers, reflective and transmissive color filters, and the like.

[0154] An example of an optical element including the hologram recording medium is a hologram display device. The hologram display device includes a light source, an input unit, an optical system, and a display unit.

[0155] Specifically, the light source unit is the part that emits a laser beam used to provide, record, and reproduce three-dimensional image information of an object in the input unit and the display unit.

[0156] The aforementioned input unit is the part that pre-inputs three-dimensional image information of an object to be recorded on the display unit. Specifically, it is the part that can input three-dimensional information of an object, such as the intensity and phase of light in different spaces, to an electrically driven liquid crystal (SLM), and at this time, the input beam can be used.

[0157] The optical system may consist of mirrors, polarizers, beam splitters, beam shutters, lenses, and the like. The optical system can distribute the laser beam emitted from the light source to an input beam sent to the input unit, a recording beam sent to the display unit, a reference beam, an erase beam, a readout beam, and the like.

[0158] The display unit receives three-dimensional image information of an object from the input unit, records it on a hologram plate made of an optically addressed SLM (optically driven SLM), and can reproduce the three-dimensional image of the object. At this time, the three-dimensional image information of the object can be recorded by the interference of the input beam and the reference beam. The three-dimensional image information of the object recorded on the hologram plate can be reproduced as a three-dimensional image by the diffraction pattern generated by the readout beam, and the erase beam can be used to quickly remove the formed diffraction pattern. On the other hand, the hologram plate can move between the input position and the playback position of the three-dimensional image. [Effects of the Invention]

[0159] A holographic recording medium according to one embodiment of the invention can have excellent optical recording characteristics and low haze by controlling the elemental ratio of fluorine on the surface of the photopolymer layer to a specific range, thereby providing an optical element with excellent visibility. [Brief explanation of the drawing]

[0160] [Figure 1] This diagram schematically shows the setup of a recording device for hologram recording. Specifically, Figure 1 schematically shows the process in which a laser of a predetermined wavelength is irradiated from a light source 10, and then irradiated onto a PP (hologram recording medium) 80 located on one side of a mirror 70, after passing through a mirror 20, 20', iris 30, spatial filter 40, iris 30', collimation lens 50, and polarized beam splitter (PBS) 60. [Modes for carrying out the invention]

[0161] The following will explain the function and effects of the invention in more detail through specific embodiments. However, these are presented as examples of the invention and do not limit the scope of the invention's rights in any way.

[0162] 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.

[0163] Manufacturing Example 1: Production of Acrylic Polyols In a 2L jacketed reactor, 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate were added and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60°C to 70°C, and the mixture was stirred for 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added, and the mixture was stirred for another 30 minutes. Subsequently, 0.24g of the polymerization initiator AIBN was added, and polymerization was carried out at the reaction temperature for 4 hours or more until the residual acrylate content was less than 1%, thereby producing an acrylate copolymer (weight-average molecular weight approximately 300,000, OH equivalent approximately 1802g / equivalent) in which the hydroxyl groups were located in the branched chains.

[0164] Manufacturing Example 2: Production of fluorinated compounds In a 1000 mL flask, 20.51 g of 2,2'-(oxybis((1,1,2,2-tetrafluoroethane-2,1-diyl)oxy))bis(2,2-difluoroethan-1-ol) was added, then dissolved in 500 g of tetrahydrofuran. While stirring at 0°C, 4.40 g of sodium hydroxide (60% dispersion in mineral oil) was carefully added in several stages. After stirring at 0°C for 20 minutes, 12.50 mL of 2-methoxyethoxymethyl chloride was gradually added dropwise. 1H After confirming by NMR that all reactants had been consumed, a work-up using dichloromethane yielded 29 g of a liquid product with a purity of over 95% in 98% yield. The weight-average molecular weight of the prepared fluorinated compound was 586, and the refractive index measured with an Abbe refractometer was 1.361.

[0165] Example 1: Manufacturing of a holographic recording medium (1) Production of photopolymer compositions Trimethylsilyl-terminated poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number-average molecular weight: approximately 390, SiH equivalent: approximately 103 g / equivalent) and the acrylic polyol produced in Production Example 1 were mixed first. The acrylic polyol content was 21.5 g, and the siloxane polymer was added so that the SiH / OH molar ratio was 2. In Example 1, 2.5 g of the siloxane polymer was added.

[0166] Then, 48 g of a photoreactive monomer, a mixture of bisful orange acrylate and O-phenylphenol (ethylene oxide) (meth)acrylate (OPPEA) in a weight ratio of 68:32, 0.2 g of H-Nu640 (Spectra) red dye as a photosensitive dye, 0.8 g of hexadecyldimethylbenzylammonium tri(p-chlorophenyl)butyl borate and 0.05 g of H-Nu254 (Spectra) as co-initiators, 0.9 g of Irgacure369 as a photoinitiator, 24 g of the fluorine-based compound produced in Production Example 2 as a plasticizer, and 206 g of methyl isobutyl ketone (MIBK) as a solvent were added, and the mixture was stirred in a paste mixer for about 30 minutes while blocking out light. Subsequently, 0.014 g of Karstedt (Pt-based) catalyst was added for matrix crosslinking to produce a photopolymer composition.

[0167] (2) Manufacturing of holographic recording media The aforementioned photopolymer composition was coated to a predetermined thickness onto a 60 μm thick TAC substrate using a Mayer bar, and dried at 80°C for 10 minutes. The thickness of the photopolymer layer after drying was approximately 15 μm.

[0168] A diffraction grating was recorded using the setup shown in Figure 1. Specifically, after laminating the manufactured photopolymer layer onto a mirror, irradiating it with a laser allows for the recording of a Notch filter hologram with periodic refractive index modulation in the thickness direction due to the interference of incident light (L) and light reflected by 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 different refractive indices are periodically stacked to a constant thickness.

[0169] Examples 2-6 and Comparative Examples 1-3: Manufacturing of Holographic Recording Media A holographic recording medium was manufactured in the same manner as in Example 1, except that the types and ratios of monofunctional monomers in the photoreactive monomer and the types of photosensitive dyes were different, as shown in Table 1 below.

[0170] In other words, in Examples 2 and 3, the same monofunctional monomer as in Example 1 was used, but the ratio of the photoreactive monomer to the total content was increased as shown in Table 1 below, while the ratio of the polyfunctional monomer, bisful orange acrylate, was simultaneously decreased to produce a photopolymer composition, from which a holographic recording medium was manufactured.

[0171] In Example 4, a holographic recording medium was manufactured in the same manner as in Example 2, except that phenoxybenzyl acrylate (PBA) was used as the monofunctional monomer.

[0172] In Example 5, a holographic recording medium was manufactured in the same manner as in Example 2, except that Rhodamine 6G, a green dye, was used as the photosensitive dye instead of a red dye.

[0173] In Example 6, the hologram recording medium was manufactured in the same manner as in Example 2, except that Astrazon Orange G, a blue dye, was used as the photosensitive dye instead of a red dye.

[0174] In Comparative Example 1, a holographic recording medium was manufactured in the same manner as in Example 1, except that only bisful orange acrylate, a polyfunctional monomer, was used as the photoreactive monomer.

[0175] In Comparative Examples 2 and 3, holographic recording media were manufactured in the same manner as in Example 1, except that the ratio of monofunctional monomers to the total content of photoreactive monomers was decreased or increased as shown in Table 1 below, and the ratio of polyfunctional monomers was controlled by the same amount as the decrease or increase.

[0176] [Table 1]

[0177] Comparative Example 4: Manufacturing of Holographic Recording Media A holographic recording medium was manufactured in the same manner as in Example 1, except that 31.4 g of the acrylic polyol manufactured in Manufacturing Example 1, 3.6 g of the siloxane polymer, 35 g of HR6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.2 g of the compound represented by the following chemical formula a (Chemical Formula 10) as a photosensitive dye, and 30 g of the fluorine compound manufactured in Manufacturing Example 2 as a plasticizer were used.

[0178] [ka]

[0179] Test Example: Performance Evaluation of Holographic Recording Media (1) Element ratio The elemental ratios on the surface of the pre-recording sample were analyzed using the method described below.

[0180] Specifically, the sample to be analyzed was fixed to copper foil with carbon tape, placed on a sample holder, and secured with a clip. Then, data was obtained using a photoelectron spectrometer (ESCA, model name: K-Alpha+, Thermo Fisher Scientific Inc.) for chemical analysis according to the K-Alpha+ standard operating procedure (SOP-0524-Ok), and the elemental ratio (atomic %) of the sample surface was analyzed using Avantage software (version 5.980).

[0181] The system specifications of the ESCA equipment used are as follows:

[0182] -Base chamber pressure: 1.0 x 10 -9 mbar -X-ray source:monochromatic Al Kα(1486.6eV) -X-ray spot size: 400μm -Mode: CAE (Constant Analyzer Energy) mode -Charge compensation: Flood gun (FG03: 100 μA, 0.5 V)

[0183] For the surface of the as-received analysis target sample, an initial survey scan was performed under the following conditions to conduct qualitative analysis, and quantitative analysis was carried out by narrow scan (snap) for each element based on the results of the qualitative analysis. The elemental ratios at three locations per sample were confirmed, and the peak background smart method was applied for quantitative analysis. The binding energy correction of the core level spectrum was based on C 1s (284.8 eV).

[0184] <Survey scan conditions> -Scan range of binding energy: -5 eV ~ 1350 eV -Step size: 1 eV -Per Point dwell time: 20 ms -Periods: 2 -Pass energy: 200 eV <narrow scan conditions> -Scan range of binding energy: Approximately 20 eV -Step size: ~0.16 eV -Per Point dwell time: 1 sec -Periods: 10 ~ 30 -Pass energy: 150 eV <Etching conditions> -Source: Ar ion -Energy: 6 keV -Cluster size: 75 -Rater size: 1.6 X 1.0 mm 2 -Mode: GCIB

[0185] (2) Diffraction efficiency (DE) The diffraction efficiency (η) was determined by the following formula 1 (Equation 1).

[0186] [Equation]

[0187] In the above formula 1, η is the diffraction efficiency, and P D is the output power (mW / cm 2 ) of the diffracted beam of the sample after recording, and P T is the output power (mW / cm 2 ) of the transmitted beam of the sample after recording.

[0188] (3) Haze A 5 cm × 5 cm test piece was prepared from the sample on which the diffraction grating was recorded. The haze of the test piece was measured using a haze meter (HM-150, A light source, Murakami Co., Ltd.) in accordance with JIS K7136. The haze was measured three times in total, and the average value was calculated and defined as the haze value of the sample.

[0189] [Table 2]

[0190] Referring to Table 2 above, it is confirmed that the hologram recording medium of the above-described embodiment exhibits excellent optical recording characteristics and low haze by controlling the elemental ratio of fluorine on the surface of the photopolymer layer to 0.05 atomic % to 3 atomic %. This is considered to be the result of improving the compatibility of the photopolymer composition using a photoreactive monomer containing a monofunctional monomer having a predetermined content.

[0191] Examples 2, 5, and 6 show the test results of holographic recording media manufactured using red dye, green dye, and blue dye, respectively. In the case of blue dye, it is common to see lower optical recording characteristics compared to other photosensitive dyes. Considering this, it is confirmed that the holographic recording media of the above embodiment exhibits excellent optical recording characteristics and low haze in all red, green, and blue regions by controlling the elemental ratio of fluorine on the surface of the photopolymer layer to the aforementioned range.

[0192] In contrast, in Comparative Examples 1 and 2, monofunctional monomers were either not used or used in very small amounts, resulting in an elemental ratio of fluorine on the surface of the photopolymer layer exceeding 3 atomic percent. As a result, the holographic recording media of Comparative Examples 1 and 2 exhibited high haze.

[0193] In Comparative Example 3, an excess of monofunctional monomer was used, resulting in a fluorine content of less than 0.05 atomic percent on the surface of the photopolymer layer. As a result, the holographic recording medium in Comparative Example 3 exhibited reduced crosslinking and increased tackiness, leading to extremely poor recording characteristics.

[0194] In Comparative Example 4, the decrease in the total photoreactive monomer content led to an increase in the polymer matrix and fluorinated compound content, resulting in an elemental ratio of fluorine on the surface of the photopolymer layer exceeding 3 atomic percent. As a result, the holographic recording medium of Comparative Example 4 exhibited a good level of haze, but showed degraded recording characteristics.

Claims

1. A holographic recording medium comprising a photopolymer layer, The photopolymer layer comprises a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and an acrylic polyol, a photoreactive monomer and a photoinitiator system, or a photopolymer obtained from the photoreactive monomer, and a fluorine-based compound. A holographic recording medium wherein the elemental ratio of fluorine to the total amount of carbon, oxygen, fluorine, and silicon atoms, as confirmed by photoelectron spectroscopy for chemical analysis on the surface of the photopolymer layer, is between 0.1 atomic% and 2.7 atomic%.

2. The holographic recording medium according to claim 1, wherein the elemental ratio of carbon to the total amount of carbon, oxygen, fluorine, and silicon atoms, as confirmed by photoelectron spectroscopy for chemical analysis on the surface of the photopolymer layer, is 50 atomic% to 80 atomic%, the elemental ratio of oxygen is 15 atomic% to 40 atomic%, and the elemental ratio of silicon is 0.5 atomic% to 10 atomic%.

3. The siloxane polymer comprises a repeating unit represented by the following chemical formula 1 (Chemical Formula 1) and an end group represented by the following chemical formula 2 (Chemical Formula 2), 【Chemistry 1】 In the aforementioned chemical formula 1, Multiple R １ and R ２ These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. n is an integer between 1 and 10,000. 【Chemistry 2】 In the aforementioned chemical formula 2, Multiple R １１ ~R １３ These are either identical or different from each other, and each is independently hydrogen, a halogen, or an alkyl group having 1 to 10 carbon atoms. R of either one of the repeating units represented by chemical formula 1 and the terminal group represented by chemical formula 2 １ , R ２ and R １１ ~R １３ The holographic recording medium according to claim 1, wherein at least one of the elements is hydrogen.

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

5. The holographic recording medium according to claim 1, wherein the molar ratio of the silane functional group of the siloxane polymer to the hydroxyl group of the acrylic polyol is 1.5 to 4.

6. The holographic recording medium according to claim 1, wherein the photoreactive monomer includes monofunctional monomers and polyfunctional monomers.

7. The holographic recording medium according to claim 6, wherein the monofunctional monomer is present in an amount of 30% to 68% by weight relative to the total weight of the photoreactive monomer.

8. The photoreactive monomer includes one or more monofunctional monomers 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. The hologram recording medium according to claim 1.

9. The aforementioned photoreactive monomer is bisphenol A (ethylene oxide) ２～１０ The holographic recording medium according to claim 1, comprising one or more polyfunctional monomers selected from the group consisting of di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bis-full orange (meth)acrylate, modified bisphenol full orange (meth)acrylate, tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolac epoxy (meth)acrylate.

10. The hologram recording medium according to claim 1, wherein the photoreactive monomer is contained in an amount of 50 to 300 parts by weight per 100 parts by weight of the polymer matrix.

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

12. The aforementioned co-initiator contains a borate anion represented by the following chemical formula 3 (Chemical Formula 3), 【Transformation 3】 In the above chemical formula 3, X １ ~X ４ Each of these is independently a substituted or unsubstituted C1-C20 alkyl group, a C2-C20 alkenyl group, a C6-C30 aryl group, a C7-C30 arylalkyl group, a C7-C30 alkylaryl group, or an allyl group, and X １ ~X ４ The holographic recording medium according to claim 11, wherein at least one of the members is not an aryl group.

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

14. The hologram recording medium according to claim 1, wherein the photopolymer layer comprises 17% to 38% by weight of the polymer matrix, 38% to 58% by weight of the photoreactive monomer, and 17% to 38% by weight of the fluorine-based compound, based on the total weight of the polymer matrix, the photoreactive monomer, and the fluorine-based compound.

15. The hologram recording medium according to claim 1, wherein the diffraction efficiency is 80% or more when a Notch filter hologram is recorded.

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

17. A step of forming a photopolymer layer by applying a photopolymer composition comprising a polymer matrix or its precursor formed by crosslinking a siloxane polymer containing a silane functional group and an acrylic polyol, a fluorine compound, a photoreactive monomer, and a photoinitiator system, The process includes the step of irradiating a predetermined region of the photopolymer layer with a coherent laser to selectively polymerize the photoreactive monomers contained in the photopolymer layer and record optical information. A method for manufacturing a holographic recording medium, wherein the elemental ratio of fluorine to the total amount of carbon, oxygen, fluorine, and silicon atoms, as confirmed by photoelectron spectroscopy for chemical analysis on the surface of the photopolymer layer, is 0.1 atomic% to 2.7 atomic%.

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

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