Holographic recording medium, its manufacturing method and optical element including same

Abstract

The present invention relates to a holographic recording medium, a method for producing the same, and an optical element including the same. The holographic recording medium has a specific element composition ratio, and thus has excellent optical recording properties, excellent durability against heat and moisture, suitable adhesive strength to a transparent adhesive, and high transparency.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0146069 dated November 4, 2022, Korean Patent Application No. 10-2022-0146073 dated November 4, 2022, and Korean Patent Application No. 10-2023-0132803 dated October 5, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

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

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

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

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

[0006] This local photopolymerization process induces a refractive index modulation, which generates a diffraction grating. The refractive index modulation value (Δn) is affected by the thickness and diffraction efficiency (DE) of the photopolymer layer, and the angular selectivity is wider with decreasing thickness.

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

[0008] Meanwhile, when holographic recording media are used as optical elements in applications such as mobile devices and vehicle accessories (e.g., head-up displays), they are placed in high temperature / high humidity environments. In such cases, the diffraction grating may deform, distorting the image or failing to perform its intended function. Therefore, there is a need to develop a photopolymer layer and a holographic recording medium containing the same that exhibit minimal deformation of the diffraction grating and are highly reliable, despite the heat and moisture of the usage environment. Summary of the Invention [Problem to be solved by the invention]

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

[0010] According to another embodiment of the present invention, there is provided a method for manufacturing the holographic recording medium.

[0011] According to yet another embodiment of the present invention, there is provided an optical element including the holographic recording medium. [Means for solving the problem]

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

[0013] In the present specification, unless otherwise specified, the term "hologram recording medium" refers to a medium on which optical information can be recorded in the entire visible light range and ultraviolet light range (e.g., 300 nm to 1,200 nm) by an exposure process. Therefore, the hologram recording medium in the present specification may refer to a medium on which optical information is recorded, or a medium before recording in a state in which optical information can be recorded. The hologram in the present specification may include all visual holograms such as in-line (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white light transmission holograms ("rainbow holograms"), Denisyuk holograms, off-axis reflection holograms, edge-literature holograms, or holographic stereograms.

[0014] According to one embodiment of the invention, there is provided a holographic recording medium comprising a photopolymer layer containing: a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a fluorine-based compound, wherein, relative to the total amount of carbon, nitrogen, oxygen, fluorine and silicon atoms confirmed by photoelectron spectroscopy on the surface of the photopolymer layer, the elemental ratio of carbon is 50 atomic % to 70 atomic %, the elemental ratio of nitrogen is 0.01 atomic % to 2 atomic %, the elemental ratio of oxygen is 15 atomic % to 30 atomic %, the elemental ratio of fluorine is 3 atomic % to 12 atomic %, and the elemental ratio of silicon is 3 atomic % to 15 atomic %.

[0015] The holographic recording medium of the embodiment includes a photopolymer layer having a specific elemental composition ratio, and thus has excellent optical recording characteristics, which are the physical properties of a holographic recording medium, as well as excellent durability against heat and moisture, adhesion to OCA, and transparency.

[0016] Specifically, the element ratio of the photopolymer layer surface can be confirmed by using photoelectron spectroscopy called X-ray photoelectron spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA). According to the photoelectron spectroscopy described in the test example described later, after qualitative analysis of elements found on the surface of the sample to be analyzed by a survey scan, a narrow scan can be performed for each element found to measure the element ratio. The element ratio of the photopolymer layer in this specification may be understood as the element ratio of the photopolymer layer before recording or the element ratio of the photopolymer layer after recording. The element ratio of the photopolymer layer before recording and the element ratio of the photopolymer layer after recording may be the same within the experimental error range, but may be different from each other in some examples. In other words, even if the element ratio of the photopolymer layer before recording and the element ratio after recording are different from each other beyond the error range, the holographic recording medium of the embodiment can exhibit the intended effect as long as the element ratio before recording or after recording is within the above-mentioned range. The atomic ratio of carbon on the surface of the photopolymer layer contained in the holographic recording medium of the embodiment may be 50 atomic % or more, 51 atomic % or more, 52 atomic % or more, 53 atomic % or more, or 54 atomic % or more, and may be 70 atomic % or less, 69 atomic % or less, or 68 atomic % or less.

[0017] The atomic ratio of nitrogen at the surface of the photopolymer layer may be 0.01 atomic % or more, 0.05 atomic % or more, 0.10 atomic % or more, or 0.20 atomic % or more, and may be 2 atomic % or less, 1.8 atomic % or less, 1.6 atomic % or less, 1.4 atomic % or less, or 1.2 atomic % or less.

[0018] The atomic ratio of oxygen on the surface of the photopolymer layer may be 15 atomic % or more, 16 atomic % or more, or 17 atomic % or more, and may be 30 atomic % or less, 29 atomic % or less, 28 atomic % or less, 27 atomic % or less, or 26 atomic % or less.

[0019] The atomic ratio of fluorine on the surface of the photopolymer layer may be 3 atomic % or more, or 4 atomic % or more, and may be 12 atomic % or less, 11 atomic % or less, or 10 atomic % or less.

[0020] The atomic ratio of silicon in the surface of the photopolymer layer may be 3 atomic % or more, 4 atomic % or more, or 4.5 atomic % or more, and may be 15 atomic % or less.

[0021] The elemental ratios of carbon, nitrogen, oxygen, fluorine and silicon are percentages (atomic %) relative to the total amount of carbon, nitrogen, oxygen, fluorine and silicon atoms confirmed by photoelectron spectroscopy on the surface of the photopolymer layer.

[0022] The photopolymer layer exhibits the above-mentioned elemental composition ratio, and thus has excellent optical recording properties, excellent durability against heat and moisture, suitable adhesion to OCA (optically clear adhesive), and transparent optical properties. In particular, if the elemental ratio of fluorine is less than the above range, there may be problems of reduced optical recording properties, vulnerability to heat and moisture, and high haze, while if the elemental ratio of fluorine exceeds the above range, there may be problems of reduced optical recording properties and reduced adhesive strength to OCA. In addition, if the elemental ratio of silicon is less than the above range, there may be problems of vulnerability to heat and high haze, while if the elemental ratio of silicon exceeds the above range, there may be problems of significantly reduced optical recording properties.

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A holographic recording medium according to an embodiment of the present invention, a method for producing the same, and an optical element including the holographic recording medium will now be described in detail.

[0024] The holographic recording medium of the embodiment includes a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a photopolymer layer including a fluorine-based compound.

[0025] The photopolymer layer may be a pre-recorded photopolymer layer on which optical information can be recorded, or may be a photopolymer layer in which optical information has been recorded.

[0026] The photopolymer layer in which optical information is recorded can be manufactured by irradiating the photopolymer layer before recording with an object light and a reference light. When the photopolymer layer before recording is irradiated with the object light and the reference light, the photoinitiator system exists in an inactive state in the destructive interference region due to the interference length of the object light and the reference light, so photopolymerization of the photoreactive monomer does not occur, and the photoinitiator system is activated in the reinforcement interference region to photopolymerize the photoreactive monomer. In the reinforcement interference region, the photoreactive monomer is continuously consumed, so that a concentration difference occurs between the photoreactive monomer in the destructive interference region and the reinforcement interference region. As a result, the photoreactive monomer in the destructive interference region diffuses into the reinforcement interference region. At this time, the fluorine-based compound of the plasticizer moves in the opposite direction to the photoreactive monomer. Since the photoreactive monomer and the photopolymer formed therefrom have a higher refractive index than the polymer matrix and the fluorine-based compound, a spatial refractive index change occurs in the photopolymer layer, and a grating is generated due to the spatial refractive index modulation occurring in the photopolymer layer. Such a grating surface acts as a reflective surface that reflects incident light due to the difference in refractive index. After holographic recording, when light of a wavelength is incident during recording in the direction of the reference light, the Bragg condition is satisfied and the light is diffracted in the original object light direction, reproducing the holographic optical information.

[0027] Therefore, when the photopolymer layer is in a pre-recorded state, the photopolymer layer may include the photoreactive monomer, the photoinitiator system, and the fluorine-based compound randomly dispersed within the polymer matrix or a precursor thereof.

[0028] On the other hand, if optical information is recorded in the photopolymer layer, the photopolymer layer may include a photopolymer and a fluorine-based compound distributed so as to form a lattice with a polymer matrix.

[0029] The photopolymer layer is formed from a photopolymer composition including a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing silane functional groups and a (meth)acrylic polyol; a fluorine-based compound; a photoreactive monomer; and a photoinitiator system.

[0030] The polymer matrix is ​​formed by crosslinking a siloxane-based polymer containing a silane functional group (Si-H) and a (meth)acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking a (meth)acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxyl group of the (meth)acrylic polyol can form a crosslink with the silane functional group of the siloxane polymer by a hydrosilylation reaction. The hydrosilylation reaction can be rapidly carried out even at a relatively low temperature (for example, at a temperature of about 60°C) under a Pt-based catalyst. Therefore, the photopolymer composition of the embodiment can improve the manufacturing efficiency and productivity of the holographic recording medium by adopting a polymer matrix that can be rapidly crosslinked even at a relatively low temperature as a support.

[0031] The polymer matrix can increase the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer due to the flexible backbone of the siloxane-based polymer. In addition, the siloxane bond, which has excellent heat resistance and humidity and heat resistance, can easily ensure the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium including the same.

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

[0033] The photopolymer layer includes a polymer matrix formed by crosslinking the siloxane-based polymer containing the silane functional group and the (meth)acrylic polyol, and may also include a polymer matrix precursor that is not partially crosslinked. In this case, the polymer matrix precursor may refer to the siloxane-based polymer, the (meth)acrylic polyol, and the Pt-based catalyst.

[0034] The siloxane-based polymer may include, for example, a repeating unit represented by the following Chemical Formula 1 and an end group represented by the following Chemical Formula 2.

[0035] [ka]

[0036] In the above Chemical Formula 1, Multiple R 1 and R 2 are the same or different and each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms, n is an integer from 1 to 10,000.

[0037] [ka]

[0038] In the above Chemical Formula 2, Multiple R 11 ~R 13 are the same or different and each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms, At least one repeating unit of the repeating unit represented by the chemical formula 1 and one of the terminal groups of the terminal group represented by the chemical formula 2 1 , R 2 and R 11 ~R 13 At least one of is hydrogen.

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

[0040] As used herein, the term "alkyl group" may be a straight-chain, branched-chain or cyclic alkyl group. As a non-limiting example, the term "alkyl group" as used herein may be methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethyl-propyl, 1-ethyl-propyl, 1-methyl-butyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2 ... pentyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethyl-butyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), and the like.

[0041] As an example, R1 , R 2 and R 11 ~R 13 is methyl or hydrogen, and multiple R 1 , R 2 and R 11 ~R 13 At least two of R in the formula 1 may be hydrogen. 1 and R 2 are methyl and hydrogen, and R 11 ~R 13 are each independently methyl or hydrogen (e.g., polymethylhydrosiloxane having a terminal group of a trimethylsilyl group or a dimethylhydrosilyl group); 1 and R 2 are methyl and hydrogen, respectively, and the remaining R 1 and R 2 are all methyl; and R 11 ~R 13 are each independently methyl or hydrogen (e.g., polydimethylsiloxane-co-methylhydrosiloxane having a terminal group of trimethylsilyl or dimethylhydrosilyl); or R 1 and R 2 are all methyl; and R 11 ~R 13 and the remaining are each independently methyl or hydrogen (for example, polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0042] The siloxane compound may have a number average molecular weight (Mn) in the range of 200 to 4,000, for example. Specifically, the lower limit of the number average molecular weight of the siloxane 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 polymer satisfies the above range, problems such as the siloxane polymer volatilizing during the crosslinking process with the (meth)acrylic polyol performed at room temperature or higher, resulting in a decrease in the degree of matrix crosslinking, or the siloxane polymer having poor compatibility with other components of the photopolymer layer and phase separation occurring with such components, can be prevented, thereby allowing the holographic recording medium to exhibit excellent optical recording properties and wet heat resistance.

[0043] The number average molecular weight means a polystyrene-equivalent number average molecular weight (unit: g / mol) measured by the GPC method. In the process of measuring the polystyrene-equivalent number average molecular weight measured by the GPC method, a commonly known analyzer, a detector such as a refractive index detector, and an analytical column can be used, and commonly applied temperature conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30° C., a tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0044] The silane functional group (Si-H) equivalent of the siloxane-based 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-based 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 certain functional group" is abbreviated to gram equivalent (equivalent weight) expressed in units of g / equivalent, and means the value obtained by dividing the molecular weight (weight average molecular weight, number average molecular weight, etc.) of a 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-based polymer satisfies the above range, the polymer matrix has an appropriate crosslink density and fully functions as a support, and the fluidity of the components contained in the photopolymer layer is improved, so that the boundary surface of the diffraction grating formed after recording does not collapse, and the initial refractive index modulation value is maintained at an excellent level even over time, minimizing the decrease in recording characteristics for optical information.

[0047] The (meth)acrylic polyol may refer to a polymer in which one or more, specifically two or more, hydroxyl groups are bonded to the main chain or side chain of a (meth)acrylate polymer. In this specification, "(meth)acrylic (based)" refers to acrylic (based) and / or methacrylic (based) unless otherwise specified, and is a term that encompasses acrylic (based), methacrylic (based), or a mixture of acrylic (based) and methacrylic (based).

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

[0049] Examples of the (meth)acrylate monomer having a hydroxy group include hydroxyalkyl(meth)acrylate and hydroxyaryl(meth)acrylate, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms. Examples of the (meth)acrylate monomer not having a hydroxy group include alkyl(meth)acrylate and aryl(meth)acrylate monomer, where the alkyl may be an alkyl having 1 to 30 carbon atoms and the aryl may be an aryl having 6 to 30 carbon atoms.

[0050] The (meth)acrylic polyol may have a weight average molecular weight (Mw) in the range of 150,000 to 1,000,000, for example. The weight average molecular weight means a weight average molecular weight in terms of polystyrene measured by the GPC method as described above. For example, the lower limit of the weight average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, for example, 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less, or 450,000 or less. When the weight average molecular weight of the (meth)acrylic polyol satisfies the above range, the polymer matrix can fully function as a support, and the decrease in the recording properties for optical information even after the passage of time can be minimized by imparting sufficient flexibility to the polymer matrix and improving the mobility of the components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer.

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

[0052] Specifically, the hydroxyl group (-OH) equivalent of the (meth)acrylic polyol may be, for example, within the range of 500 g / equivalent to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl group (-OH) equivalent of the (meth)acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. The upper limit of the hydroxyl group (—OH) equivalent of the (meth)acrylic polyol may be 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 (meth)acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslink density and fully functions as a support, and the fluidity of the components contained in the photopolymer layer is improved, so that the boundary surface of the diffraction grating generated after recording does not collapse, and the initial refractive index modulation value is maintained at an excellent level even over time, minimizing the decrease in recording characteristics for optical information.

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

[0055] The refractive index of the (meth)acrylic polyol may be, for example, 1.40 or more and less than 1.50. Specifically, the lower limit of the refractive index of the (meth)acrylic polyol may be, for example, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more, and the upper limit may be, for example, 1.49 or less, 1.48 or less, 1.47 or less, 1.46 or less, or 1.45 or less. When the (meth)acrylic polyol has a refractive index in the above-mentioned range, it can contribute to increasing the refractive index modulation. The refractive index of the (meth)acrylic polyol is a theoretical refractive index, and can be calculated using the refractive index of the monomers used in the production of the (meth)acrylic polyol (measured at 25°C using an Abbe refractometer) and the fraction (molar ratio) of each monomer.

[0056] The (meth)acrylic polyol and the siloxane polymer may be contained such that the molar ratio (SiH / OH) of the silane functional group (Si-H) of the siloxane polymer to the hydroxy group (-OH) of the (meth)acrylic polyol is 1.5 to 4.

[0057] The molar ratio of the silane functional groups of the siloxane polymer to the hydroxyl groups of the (meth)acrylic polyol (hereinafter, simply referred to as the SiH / OH molar ratio) can be calculated from the weight of each polymer and the number of moles of the functional groups determined from the functional group equivalent of each polymer.

[0058] Specifically, the silane functional group equivalent of the 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 the (meth)acrylic polyol is the value obtained by dividing the molecular weight (e.g., weight average molecular weight) of the (meth)acrylic polyol by the number of hydroxyl functional groups per molecule. Therefore, the mole number of silane functional groups can be confirmed by dividing the weight of the siloxane polymer by the silane functional group equivalent of the siloxane polymer, and the mole number of hydroxyl groups can be confirmed by dividing the weight of the (meth)acrylic polyol by the hydroxyl group equivalent of the (meth)acrylic polyol. More specifically, taking the example of Example 3 described later, the weight (2.6 g) of the siloxane polymer used in Example 3 is divided by the silane functional group equivalent (103 g / equivalent) of the siloxane polymer used in Example 3 to calculate the number of moles of the silane functional group (0.0252 mol), and the weight (22.4 g) of the (meth)acrylic polyol used in Example 3 is divided by the hydroxyl group equivalent (1802 g / equivalent) of the (meth)acrylic polyol used in Example 3 to calculate the number of moles of the hydroxyl group (0.0124 mol). The number of moles of the silane functional group calculated in this way (0.0252 mol) is divided by the number of moles of the hydroxyl group (0.0124 mol), and it is confirmed that the molar ratio of SiH / OH is calculated to be 2.

[0059] The lower limit of the molar ratio of SiH / OH 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, and the upper limit 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 molar ratio range of SiH / OH is satisfied, the polymer matrix is ​​crosslinked at an appropriate crosslink density to improve the fluidity of the recording components (e.g., photoreactive monomer and plasticizer, etc.), thereby ensuring excellent optical recording properties, and even when placed in a high temperature / high humidity environment after recording, the migration or deformation of the components in the photopolymer layer and the penetration of moisture into the photopolymer layer are suppressed, thereby exhibiting excellent moisture and heat resistance, and transparent optical properties.

[0060] The Pt catalyst may be, for example, a Karstedt catalyst. The Pt catalyst may be included in an amount of 0.01 to 2 parts by weight relative to 100 parts by weight of the (meth)acrylic polyol. Specifically, the Pt catalyst may be included in an amount of 0.01 parts by weight or more, 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, and 1.5 parts by weight or less, 1.0 parts 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 relative to 100 parts by weight of the (meth)acrylic polyol. When the Pt catalyst is used in the above-mentioned content, the polymer matrix is ​​crosslinked at an appropriate crosslink density, and the desired optical recording characteristics can be exhibited.

[0061] For example, when the molar ratio of the silane functional groups of the siloxane polymer acting as a crosslinker is high at about 1.5 to 4 compared to the hydroxyl groups of the (meth)acrylic polyol, which is the main component forming the polymer matrix, and the content of the Pt catalyst is adjusted to 0.01 to 0.30 parts by weight per 100 parts by weight of the (meth)acrylic polyol, the polymer matrix has an appropriate crosslink density, and as a result, a photopolymer layer exhibiting transparent optical properties can be provided.

[0062] The polymer matrix precursor may further include, in addition to the Pt-based catalyst, a rhodium-based, iridium-based, rhenium-based, molybdenum-based, iron-based, nickel-based, alkali metal or alkaline earth metal-based, Lewis acid-based, or carbene-based non-metallic catalyst, if necessary.

[0063] Meanwhile, in the holographic recording medium of the embodiment, optical information can be recorded by irradiating the photopolymer layer with object light and reference light. Due to the interference length of the object light and reference light, photopolymerization of the photoreactive monomer does not occur in the destructive interference region, but occurs in the reinforcement interference region. As the photoreactive monomer is continuously consumed in the reinforcement interference region, a concentration difference occurs between the photoreactive monomer in the destructive interference region and the reinforcement interference region, and as a result, the photoreactive monomer in the destructive interference region diffuses into the reinforcement interference region. A diffraction grating is generated by the refractive index modulation generated in this way.

[0064] Therefore, the photoreactive monomer may include a compound having a higher refractive index than the polymer matrix in order to realize the above-mentioned refractive index modulation. However, it is not limited that all the photoreactive monomers have a higher refractive index than the polymer matrix, and at least some of the photoreactive monomers may have a higher refractive index than the polymer matrix in order to realize a high refractive index modulation value. As an example, the photoreactive monomer may include a monomer having a refractive index of 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or 1.60 or more and 1.70 or less.

[0065] The photoreactive monomer may include one or more monomers selected from the group consisting of monofunctional monomers having one photoreactive functional group and polyfunctional monomers having two or more photoreactive functional groups. In this case, the photoreactive functional group may be, for example, a (meth)acryloyl group, a vinyl group, or a thiol group. More specifically, the photoreactive functional group may be a (meth)acryloyl group.

[0066] The monofunctional monomer may include, for example, one or more selected from the group consisting of benzyl (meth)acrylate (Miwon's M1182 refractive index 1.5140), benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate (Miwon's M1122 refractive index 1.565), phenol (ethylene oxide) (meth)acrylate (phenol (EO) (meth)acrylate; Miwon's M140 refractive index 1.516), phenol (ethylene oxide) 2 (meth)acrylate (Miwon's M142 refractive index 1.510), O-phenylphenol (ethylene oxide) (meth)acrylate (Miwon's M1142 refractive index 1.577), phenylthioethyl (meth)acrylate (Miwon's M1162 refractive index 1.560) and biphenylmethyl (meth)acrylate.

[0067] The 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), bisfluor di(meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR60 42 refractive index 1.600), modified bisphenol fluorene di (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 the photoreactive monomer relative to 100 parts by weight of the polymer matrix. For example, the lower limit of the content of the photoreactive monomer may be 50 parts by weight or more, 70 parts by weight or more, 100 parts by weight or more, or 110 parts by weight or more, and the upper limit may be 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. When the above range is satisfied, a photopolymer layer can be provided that exhibits excellent optical recording properties, heat resistance, moist heat resistance, and high transparency, and has suitable adhesive strength to OCA.

[0069] In this specification, the content of the polymer matrix means the combined content (weight) of the (meth)acrylic polyol and the siloxane polymer forming the matrix. In other words, the content of the polymer matrix means the content including the content of the polymer matrix formed by crosslinking the (meth)acrylic polyol and the siloxane polymer, and the content of the polymer matrix precursor that is not partially crosslinked.

[0070] The photopolymer layer includes a photoinitiator system, which may mean a photoinitiator that allows polymerization to be initiated by light, or may mean a combination of a photosensitizer and a coinitiator.

[0071] The photopolymer layer may include a photoinitiator system including a photoreductant and a coinitiator.

[0072] As the photosensitizer, for example, a photosensitive dye can be used. Specifically, examples of the light-sensitive dye include silicon rhodamine compounds, sulfonium derivatives of ceramidonin, new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose bengal, thionine, basic yellow, pinacyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, Quinaldine Red, crystal violet, brilliant green, and the like. One or more selected from the group consisting of fluorescein red, astrazon orange G, darrow red, pyronin Y, basic red 29, pyrylium iodide, safranin O, cyanine, methylene blue, azure A, and BODIPY may be used.

[0073] As an example, the photosensitive dye may be a silicon rhodamine compound represented by the following formula 3:

[0074] [ka]

[0075] In the above Chemical Formula 3, R 21 ~R 29 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, d and e each independently represent an integer of 0 to 3; f is an integer from 0 to 5; An - is an anion.

[0076] In this specification, "substituted or unsubstituted" means that hydrogen or carbon is replaced with another element, and hydrogen may be replaced with a halogen, a hydroxyl group, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, and carbon (-CH-) may be replaced with -O- or -CO-.

[0077] In the above formula 3, R 21 ~R 28 may each independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. 21 ~R 28 may each independently be an alkyl group having 1 to 6 carbon atoms. More specifically, in the above Chemical Formula 3, R 21 ~R 28 may be a methyl group.

[0078] In the above Chemical Formula 3, d and e may each independently be an integer of 0 to 2, an integer of 0 to 1, or 0.

[0079] In the above Chemical Formula 3, f may be an integer of 0 to 5, an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, or an integer of 1 to 2.

[0080] In the above formula 3, R 29may be a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. 29 may be an alkoxy group having 1 to 6 carbon atoms. More specifically, in the above Chemical Formula 3, R 29 may be a methoxy group.

[0081] In the above formula 3, an anion (An - ) may be a halide anion, a cyano anion, a sulfonate anion, an alkoxy anion having 1 to 30 carbon atoms, a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0082] Specifically, in the above Chemical Formula 3, an anion (An - ) may be a substituted or unsubstituted alkylsulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

[0083] More specifically, in the above Chemical Formula 3, an anion (An - ) may be an alkylsulfonate anion having 2 to 15 carbon atoms in which one or more hydrogen atoms are substituted or unsubstituted with fluorine, an alkylsulfonate anion having 6 to 30 carbon atoms in which one or more carbon atoms are substituted or unsubstituted with -O- or -CO- (Chemical formula 4), a phenylsulfonate anion substituted or unsubstituted with methyl, or a substituted or unsubstituted tetraarylborate anion. - ) may be a dodecylsulfonate anion, a perfluorobutylsulfonate anion, a phenylsulfonate anion, a methylphenylsulfonate anion, or a tetraphenylborate anion.

[0084] [ka]

[0085] The photopolymer layer may contain the photosensitive dye in the range of 0.01 to 10 parts by weight per 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the photosensitive dye 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, and the upper limit may be, for example, 5 parts by weight or less. When the above range is satisfied, it is advantageous to ensure the desired optical recording characteristics by exhibiting an appropriate polymerization reaction speed.

[0086] The coinitiator may be an electron donor, an electron acceptor, or a mixture thereof.

[0087] For example, the photopolymer composition of the embodiment may include an electron donor as a coinitiator, for example, the electron donor may include a borate anion represented by the following formula 4:

[0088] [ka]

[0089] In the above Chemical Formula 4, X 1 ~X 4 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, and X 1 ~X 4 At least one of is not an aryl group.

[0090] When the alkyl group having 1 to 20 carbon atoms, the alkenyl group having 2 to 20 carbon atoms, the aryl group having 6 to 30 carbon atoms, the arylalkyl group having 7 to 30 carbon atoms, the alkylaryl group having 7 to 30 carbon atoms or the allyl group is substituted, it may be substituted with one or more selected from the group consisting of halogen, a vinyl group, a haloalkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms.

[0091] Specifically, X 1 ~X 3 each independently represents a phenyl, methylphenyl, naphthyl, or methylnaphthyl group, which may be substituted or unsubstituted by one or more substituents selected from the group consisting of a halogen, a vinyl group, a trifluoromethyl group, and a methoxy group; 4 may be a linear alkyl group having 1 to 12 carbon atoms.

[0092] More specifically, the borate anion represented by the chemical formula 4 may be, for example, one or more types selected from the group consisting of borate anions represented by the following chemical formulas 4-1 (chemical formula 6) and 4-2 (chemical formula 7).

[0093] [ka]

[0094] In the above Chemical Formula 4-1, R 102 are each independently methyl or halogen; R 103 are each independently hydrogen, methyl or halogen, and adjacent R 102 is a halogen when is methyl, X 4’ is a straight-chain alkyl group having 1 to 12 carbon atoms.

[0095] [ka]

[0096] In the above Chemical Formula 4-2, R 106 are each independently hydrogen, methyl or halogen; X 4” is a straight-chain alkyl group having 1 to 12 carbon atoms.

[0097] In the above Chemical Formula 4-2, R 106 are each independently hydrogen, methyl or halogen, and at least one may be halogen.

[0098] When the borate anions represented by the following chemical formulas 4-1 and 4-2 are used as the electron donor, excellent heat resistance can be ensured even before recording.

[0099] In the above formulas 4-1 and 4-2, the halogen may be fluorine or chlorine. In particular, in the case of chlorine, more excellent heat resistance can be ensured.

[0100] The cation bonded to the borate anion does not absorb light and may be one or more cations selected from the group consisting of alkali metal cations, quaternary ammonium cations, and nitrogen-containing heterocyclic cations.

[0101] The alkali metal cation may be, for example, one or more selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium.

[0102] The quaternary ammonium cation may be an ammonium cation in which the nitrogen (N) is substituted with four substituents, or a cyclic ammonium cation in which two substituents substituted on the nitrogen are linked to each other, or a mixture thereof.

[0103] Specifically, the quaternary ammonium cation may be a cation represented by the following chemical formula 4-3 (chemical formula 8).

[0104] [ka]

[0105] In the above Chemical Formula 4-3, Y 1 ~Y 4 the two substituents may or may not be linked to each other to form an aliphatic ring having 4 to 10 carbon atoms, Y does not form an aliphatic ring 1 ~Y 4 are each 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 (for example, -CH2CH2-O-CO-CH2CH2CH3, etc.), Y 1 ~Y 4 are excluded.

[0106] In the above Chemical Formula 4-3, Y 1 ~Y 4 When all of the substituents are methyl groups, or when two or more of the substituents are alkyl groups having 16 or more carbon atoms, the electron donor does not dissolve well in the photopolymer composition, and the desired optical recording properties may not be exhibited.

[0107] Specifically, Y 1 ~Y 4 The two substituents can be linked together to form a piperidine or pyrrolidine.

[0108] The above Y 1 ~Y 4 Among these, the substituents not forming an aliphatic ring may each independently be a linear alkyl group having 1 to 32 carbon atoms, a phenyl group, a benzyl group, or -CH2CH2-O-CO-CH2CH2CH3. 1 ~Y 4Among these, the substituents not forming an aliphatic ring may each independently be a methyl group, a butyl group, a hexadecyl group, a hentriacontyl group, a phenyl group, or a benzyl group.

[0109] The nitrogen-containing heterocyclic cation may be a heteroaromatic ring cation containing one or more nitrogens. Examples of such heteroaromatic ring cations include pyrrole, pyrazole, imidazole, or pyridine cations, the hydrogens of which may be substituted or unsubstituted.

[0110] As an example, the nitrogen-containing heterocyclic cation may be a cation represented by the following chemical formula 4-4 (Chemical Formula 9).

[0111] [ka]

[0112] In the above Chemical Formula 4-4, R 107 , R 109 and R 110 are each independently a hydrogen atom, 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 (for example, -CH2CH2-O-CO-CH2CH2CH3, etc.), R 108 and R 111 are each 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 (for example, -CH2CH2-O-CO-CH2CH2CH3, etc.).

[0113] Specifically, R 107 , R 109 and R 110 may each independently be hydrogen or an aryl group having 6 to 30 carbon atoms. More specifically, R 107 , R 109 and R110 may each independently be hydrogen or a phenyl group.

[0114] Specifically, the R 108 and R 111 may be a linear alkyl group having 1 to 40 carbon atoms or an arylalkyl group having 6 to 40 carbon atoms. 108 and R 111 may be a hexadecyl group or a benzyl group.

[0115] The cation bound 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.

[0116] However, the cations combined with the borate anion are not limited to the above cations, and as long as they show low solubility when contained alone but show appropriate solubility when mixed with the above cations, some of the above cations may be substituted with other cations known in the related technical field. As a non-limiting example, some of the above cations may be substituted with 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium, etc.

[0117] As an example, the photopolymer layer can include an electron acceptor as a coinitiator, which can include, for example, an onium salt, such as a sulfonium salt, an iodonium salt, or the like; a triazine compound, such as a tris(trihalomethyl)triazine, a substituted bis(trihalomethyl)triazine, or the like; or a mixture thereof.

[0118] 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. As the electron acceptor, for example, commercially available H-Nu254 (Spectra) or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (TCI) may be used.

[0119] The photopolymer layer may contain the coinitiator in the range of 0.05 parts by weight to 10 parts by weight relative to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the coinitiator may be, for example, 0.1 parts by weight or more, 0.5 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, and the upper limit may be, for example, 5 parts by weight or less. When the above range is satisfied, it is advantageous to ensure the desired optical recording characteristics by exhibiting an appropriate polymerization reaction rate.

[0120] The photoinitiator system may contain an additional photoinitiator to remove the color of the photosensitive dye and to react all of the unreacted photoreactive monomers after irradiation with light for recording. Examples of the photoinitiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, amine derivatives, diazonium salts, sulfonium salts, iodonium salts, sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-benzene)(η5-cyclopentadienyl)iron(II), benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosylphthalimide, and mixtures thereof.More specifically, the photoinitiator may be 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercapto benzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (product name: Irgacure651 / manufacturer: BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Irgacure184 / manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (product name: Irgacure369 / manufacturer: BASF), bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium (product name: Irgacure784 / manufacturer: BASF), Ebecryl P-115 (manufacturer: SK entis), Cyracure UVI-6970, Cyracure Examples include, but are not limited to, UVI-6974, Cyracure UVI-6990 (manufactured by Dow Chemical Co. in USA), Irgacure 264, Irgacure 250 (manufactured by BASF), CIT-1682 (manufactured by Nippon Soda), or mixtures thereof.

[0121] The photopolymer layer may contain the photoinitiator in a range of 0.05 parts by weight to 10 parts by weight with respect to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the photoinitiator 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, and the upper limit may be, for example, 5 parts by weight or less. When the above range is satisfied, after optical information is recorded in the photopolymer layer, the reaction of the photoreactive monomer can be effectively terminated and the color of the photosensitive dye can be decolorized to provide a transparent holographic recording medium.

[0122] The photopolymer layer includes a fluorine-based compound as a plasticizer. The plasticizer can easily realize refractive index modulation during the manufacture of the holographic recording medium. More specifically, the plasticizer lowers the glass transition temperature of the polymer matrix to improve the fluidity of the photoreactive monomer, and has a low refractive index and non-reactive properties and is uniformly distributed in the polymer matrix. When the non-photopolymerized photoreactive monomer moves, the plasticizer moves in the opposite direction to contribute to the refractive index modulation. The plasticizer can also contribute to improving the moldability of the photopolymer composition.

[0123] The fluorine-based compound may have a low refractive index of 1.45 or less in order to perform the function of the plasticizer described above. Specifically, the upper limit of the refractive index may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less, and the lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. Since a fluorine-based compound having a refractive index lower than that of the above-mentioned photoreactive monomer is used, the refractive index of the polymer matrix can be lowered, and the refractive index modulation with the photoreactive monomer can be increased.

[0124] The fluorine-based compound may contain, for example, one or more functional groups selected from the group consisting of an ether group, an ester group, and an amide group, and two or more difluoromethylene groups. More specifically, the fluorine-based compound may be, for example, a compound containing a repeating unit represented by the following chemical formula 5 (Chemical Formula 10).

[0125] [ka]

[0126] In the above Chemical Formula 5, Multiple R 31 ~R 34 are each independently hydrogen or fluorine, and at least R 31 ~R 34 is fluorine, and m is an integer of 2 to 12.

[0127] More specifically, the fluorine-based compound may be a compound containing 1 to 3 units represented by the following chemical formula 5-1 (chemical formula 11).

[0128] [ka]

[0129] In the above Chemical Formula 5-1, R 41 ~R 44 and R 53 ~R 56 are each independently hydrogen or fluorine; R 45 ~R 52 is fluorine.

[0130] As an example, in the above formula 5-1, R 41 , R 42 , R 55 and R 56 is hydrogen and R 43 ~R 54 is fluorine.

[0131] The fluorine-based compound containing the repeating units represented by Formula 5 and Formula 5-1 may be capped with an end capping agent that is widely used in the related technical field, but is not particularly limited thereto. As an example, the end of the fluorine-based compound containing the repeating units represented by Formula 5 and Formula 5-1 may be an alkyl group or an alkyl group substituted with one or more alkoxy groups. As a non-limiting example, the end of the fluorine-based compound containing the repeating units represented by Formula 5 and Formula 5-1 may be a 2-methoxyethoxymethyl group using 2-methoxyethoxymethyl chloride as an end capping agent.

[0132] The fluorine-based compound may have a weight average molecular weight of 300 or more. Specifically, the lower limit of the weight average molecular weight of the fluorine-based compound may be, for example, 350 or more, 400 or more, 450 or more, 500 or more, or 550 or more, and the upper limit may be, for example, 1000 or less, 900 or less, 800 or less, 700 or less, or 600 or less. When considering the refractive index modulation, compatibility with other components, and problems such as elution of the fluorine-based compound, it is preferable to satisfy the above weight average molecular weight range. At this time, the weight average molecular weight means the weight average molecular weight in terms of polystyrene measured by the GPC method as described above.

[0133] The photopolymer layer may contain 20 parts by weight to 200 parts by weight of the fluorine-based compound relative to 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the fluorine-based compound 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, and the upper limit 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 range is satisfied, there is no problem such as a part of the fluorine-based compound being dissolved on the surface of the photopolymer layer due to a deterioration in compatibility with the components contained in the photopolymer layer, or a deterioration in haze, and a fluorine-based compound having a sufficiently low refractive index can show a large refractive index modulation value after recording, which is advantageous for ensuring excellent optical recording characteristics.

[0134] The majority of the components of the photopolymer layer are the polymer matrix, the photoreactive monomer, and the fluorine-based compound. Therefore, the elemental composition ratio of the surface of the photopolymer layer can be controlled by the compounding ratio of the polymer matrix, the photoreactive monomer, and the fluorine-based compound. In order to satisfy the above-mentioned elemental composition ratio, the photopolymer layer can contain 17% by weight to 38% by weight of the polymer matrix, 36% by weight to 58% by weight of the photoreactive monomer, and 17% by weight to 38% by weight of the fluorine-based compound relative to the total weight of the polymer matrix, the photoreactive monomer, and the fluorine-based compound.

[0135] More specifically, the polymer matrix may be contained, for example, at 17% by weight or more, 18% by weight or more, 19% by weight or more, or 20% by weight or more, and 38% by weight or less, 37% by weight or less, or 36% by weight or less. The photoreactive monomer may be contained, for example, at 36% by weight or more, 37% by weight or more, or 38% by weight or more, and 58% by weight or less, 55% by weight or less, or 53% by weight or less. The fluorine-based compound may be contained, for example, at 17% by weight or more, 18% by weight or more, 19% by weight or more, or 20% by weight or more, and 38% by weight or less, 35% by weight or less, 33% by weight or less, or 32% by weight or less. A photopolymer layer satisfying the above-mentioned element composition ratio within such a range can be provided.

[0136] The photopolymer layer may additionally contain additives such as surfactants or antifoaming agents.

[0137] The photopolymer layer may contain, as a surfactant, a silicone-based surfactant, a fluoro-surfactant, or a mixture thereof.

[0138] Examples of the silicone surfactant that can be used 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, BYK355, BYK-356, BYK-358, BYK-361, BYK-370, BYK-371, BYK-375, BYK-380, BYK-390, and BYK-3550 manufactured by BYK Chemie. Examples of the fluorine-based surfactant include 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-485, F-486, F-487, F-488, F-489, F-490SF, F-491, F-492SF, F-493, F-494, F-495, F-497, F-498, F-499, F-480SF, F-482, F-483, F-484, F-485, F-486, F-487, F-488, F-489 ...9, F-489, F-490, 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.

[0139] If the photopolymer layer contains a surfactant, the surfactant may be 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, based on 100 parts by weight of the polymer matrix. When the above range is satisfied, the photopolymer layer is provided with excellent adhesion and releasability, and excellent optical recording properties can be maintained.

[0140] The photopolymer layer may include a silicone-based reactive additive as an antifoaming agent. As the silicone-based reactive additive, a commercially available product such as Tego Rad 2500 may be used. The content of the antifoaming agent may be appropriately adjusted to a level that does not interfere with the function of the holographic recording medium.

[0141] The photopolymer layer may be formed from a solvent-containing photopolymer composition.

[0142] The solvent may be an organic solvent, and may be, for example, one or more organic solvents selected from the group consisting of ketones, alcohols, acetates, and ethers, but is not limited thereto.Specific examples of such organic solvents include ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; and ethers such as tetrahydrofuran or propylene glycol monomethyl ether.

[0143] The organic solvent may be added when the components to be contained in the photopolymer composition are mixed, or may be added to the photopolymer composition while the components are being dispersed or mixed in the organic solvent.

[0144] The photopolymer composition may contain a solvent so that the solid content concentration is 1 wt% to 90 wt%. Specifically, the photopolymer composition may contain a solvent so that the solid content concentration is 20 wt% or more, 25 wt% or more, or 30 wt% or more, and 50 wt% or less, 45 wt% or less, or 40 wt% or less. Within such ranges, the photopolymer composition exhibits appropriate fluidity, can form a coating film without defects such as stripes, and can form a photopolymer layer that exhibits desired physical properties and surface characteristics without defects during the drying and curing process.

[0145] The holographic recording medium of the embodiment has excellent refractive index modulation, diffraction efficiency, and driving reliability despite having a thin photopolymer layer.

[0146] 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. And the upper limit of the thickness may be, for example, 35 μm or less, 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, 25 μm or less, 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, 19 μm or less, or 18 μm or less.

[0147] The holographic recording medium of the embodiment may further include a substrate on at least one surface of the photopolymer layer. The type of substrate is not particularly limited, and substrates known in the related technical field may be used. For example, substrates such as glass, polyethylene terephthalate (PET), triacetyl cellulose (TAC), polycarbonate (PC), and cycloolefin polymer (COP) may be used.

[0148] The holographic recording medium of the embodiment may have high diffraction efficiency. As an example, when a notch filter hologram is recorded in the holographic recording medium, the holographic recording medium may 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, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, or 96% or more. In this way, the holographic recording medium of the embodiment may achieve excellent diffraction efficiency even if it includes a thin photopolymer layer. The diffraction efficiency can be measured by a method described in a test example described later.

[0149] The holographic recording medium of the embodiment includes a photopolymer layer having a specific element composition ratio, and thus can exhibit heat and / or moisture resistance.

[0150] As an example, the holographic recording medium of the embodiment may have a diffraction efficiency change value (ΔDE) calculated by the following equation 2 (mathematical formula 1) of 10% or less.

[0151]

number

[0152] In the above formula 2, DE0 is the diffraction efficiency measured for a holographic recording medium on which a notch filter hologram is recorded after storing the unrecorded holographic recording medium in a darkroom under constant temperature and humidity conditions of 20°C to 25°C and 40RH% to 50RH%, and DE1 is the diffraction efficiency measured for a holographic recording medium on which a notch filter hologram is recorded after storing the unrecorded holographic recording medium in a darkroom under high temperature conditions of 60°C to 70°C and 40RH% to 50RH%.

[0153] The diffraction efficiency change value is an index capable of evaluating the durability (heat resistance) of the holographic recording medium before recording, and the higher the durability against heat, the smaller the diffraction efficiency change value (ΔDE) calculated by the formula 2 can be. For a more specific method of measuring the diffraction efficiency change value (ΔDE) calculated by the formula 2, the method described in the test example described later can be referred to. The diffraction efficiency change value may be 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2% or less.

[0154] The holographic recording medium of the embodiment can exhibit excellent durability not only against heat but also in high temperature and high humidity environments. Specifically, the holographic recording medium of the embodiment can exhibit a degree of wavelength shift (Δλ) indicating the maximum reflectance before and after being left at a temperature of 60° C. and a relative humidity of 90% of −10 nm to 10 nm.

[0155] The degree of wavelength shift (Δλ) showing the maximum reflectance is an index for evaluating the durability (humid heat resistance) of the holographic recording medium after recording, and the higher the durability against heat and humidity, the smaller the degree of wavelength shift can be. For a more specific method of measuring the degree of wavelength shift (Δλ) showing the maximum reflectance, the method described in the test example described later can be referred to. The degree of wavelength shift (Δλ) showing the maximum reflectance before and after leaving under high temperature and high humidity conditions may be -10nm to 10nm, -9nm to 9nm, -8nm to 8nm, -7nm to 7nm, -6nm to 6nm, -5nm to 5nm, -4nm to 4nm, -3nm to 3nm, or -2nm to 2nm.

[0156] The holographic recording medium of the embodiment can exhibit a suitable adhesive strength to an optically transparent adhesive (OCA). Specifically, the adhesive strength of the photopolymer layer to the OCA may be 1000 gf / 25 mm or more. The adhesive strength can be measured by referring to the method described in the test example described later. The adhesive strength of the photopolymer layer to the OCA may be 1010 gf / 25 mm or more, 1030 gf / 25 mm or more, or 1100 gf / 25 mm or more. The upper limit of the adhesive strength of the photopolymer layer to the OCA is not particularly limited, but may be 3000 gf / 25 mm or less.

[0157] On the other hand, since a holographic recording medium uses a mixture of a component having a low refractive index and a component having a high refractive index for recording optical characteristics, the holographic recording medium is likely to have opaque characteristics due to the compatibility between the components. However, the holographic recording medium of the embodiment includes a photopolymer layer having a specific element composition ratio, thereby exhibiting highly transparent optical characteristics.

[0158] As an example, the haze of the holographic recording medium may be 3% or less. The upper limit of the haze may be, for example, 2.5% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 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 example described later.

[0159] The holographic recording medium of the other embodiment is expected to provide various optical elements that can be used in environments where a lot of heat is generated or humidity is high by exhibiting excellent optical recording characteristics, resistance to moist heat, and optical characteristics of high transparency.

[0160] The holographic recording medium of the embodiment is not limited to this, but may be one in which a reflection type hologram or a transmission type hologram is recorded.

[0161] Meanwhile, according to another embodiment of the present invention, there is provided a method for producing a holographic recording medium, comprising the steps of: applying a photopolymer composition comprising a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol; a fluorine-based compound; a photoreactive monomer; and a photoinitiator system to form a photopolymer layer; and irradiating a predetermined region 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 photopolymer layer has an elemental ratio of carbon of 50 atomic % to 70 atomic %, an elemental ratio of nitrogen of 0.01 atomic % to 2 atomic %, an elemental ratio of oxygen of 15 atomic % to 30 atomic %, an elemental ratio of fluorine of 3 atomic % to 12 atomic %, and an elemental ratio of silicon of 3 atomic % to 15 atomic %, relative to the total amounts of carbon, nitrogen, oxygen, fluorine, and silicon atoms confirmed on the surface by photoelectron spectroscopy.

[0162] The photopolymer layer having the specific elemental composition ratio may be a photopolymer layer contained in the holographic recording medium of the embodiment described above, and as the photopolymer layer has been described in detail above, a detailed description thereof will be omitted here.

[0163] In the step of forming the photopolymer layer, a photopolymer composition having the above-mentioned configuration can be prepared first. When preparing the photopolymer composition, a commonly known mixer, stirrer, mixer, etc. can be used to mix the components without any restrictions. The mixing process may be performed at a temperature in the range of 0°C to 100°C, 10°C to 80°C, or 20°C to 60°C.

[0164] In the step of forming the photopolymer layer, a prepared photopolymer composition may be applied to form a coating film formed from the photopolymer composition. The coating film may be dried at a temperature of 50° C. or more, 55° C. or more, 60° C. or more, 65° C. or more, or 70° C. or more and 120° C. or less, 110° C. or less, 100° C. or less, or 90° C. or less. Through this process, a hydrosilylation reaction between the hydroxyl group of the (meth)acrylic polyol that remains unreacted and the silane functional group of the siloxane polymer is induced, thereby achieving a desired crosslink density while maintaining high transparency.

[0165] The photopolymer layer manufactured by the step of forming the photopolymer layer may have a fluorine-based compound, a photoreactive monomer, a photoinitiator system, and additives added as necessary uniformly dispersed within a crosslinked polymer matrix.

[0166] Thereafter, when a coherent laser is irradiated onto the photopolymer layer in the step of recording optical information, polymerization of the photoreactive monomer occurs in the area where constructive interference occurs, forming a photopolymer, while polymerization of the photoreactive monomer does not occur or is suppressed in the area where destructive interference occurs, resulting in the existence of photoreactive monomer. The unreacted photoreactive monomer diffuses into the photopolymer side where the concentration of the photoreactive monomer is low, causing refractive index modulation, which generates a diffraction grating. As a result, a hologram, i.e., optical information, is recorded in the photopolymer layer having the diffraction grating.

[0167] In yet another embodiment of the method for manufacturing a holographic recording medium, after the step of recording optical information, the method may further include a step of photobleaching by irradiating light onto the entire photopolymer layer on which the optical information is recorded.

[0168] In the photobleaching step, the photopolymer layer on which the optical information is recorded is irradiated with ultraviolet light to terminate the reaction of the photoreactive monomer remaining in the photopolymer layer, thereby removing the color of the photosensitive dye. For example, in the photobleaching step, ultraviolet light (UVA) in the range of 320 nm to 400 nm is irradiated to terminate the reaction of the photoreactive monomer, thereby removing the color of the photosensitive dye.

[0169] Meanwhile, according to still another embodiment of the present invention, there is provided an optical element including the holographic recording medium.

[0170] Specific examples of the optical element include smart devices such as mobile devices, parts of wearable displays, vehicle accessories (e.g., head up displays), holographic fingerprint recognition systems, holographic optical elements having the functions of optical lenses, mirrors, deflection mirrors, filters, diffusion screens, diffraction members, light guides, waveguides, projection screens and / or masks, media and light diffusion plates in optical memory systems, optical wavelength splitters, reflective and transmissive color filters, etc.

[0171] An example of an optical element including the holographic recording medium is a holographic display device, which includes a light source unit, an input unit, an optical system, and a display unit.

[0172] Specifically, the light source unit is a part that irradiates a laser beam used to provide, record and reproduce three-dimensional image information of an object in the input unit and the display unit.

[0173] The input unit is a unit that inputs 3D image information of an object to be recorded on the display unit in advance. Specifically, the input unit can input 3D information of an object such as spatial light intensity and phase to an electrically addressed liquid crystal SLM, and can use an input beam at this time.

[0174] The optical system may be composed of a mirror, a polarizer, a beam splitter, a beam shutter, a lens, etc. The optical system can distribute a laser beam emitted from a light source unit into an input beam sent to an input unit, a recording beam sent to a display unit, a reference beam, an erase beam, a read beam, etc.

[0175] The display unit receives 3D image information of an object from an input unit, records it on a hologram plate consisting of an optically addressed SLM, and reproduces a 3D image of the object. At this time, the 3D image information of the object can be recorded by interference between an input beam and a reference beam. The 3D image information of the object recorded on the hologram plate can be reproduced as a 3D image by a diffraction pattern generated by a read beam, and an erase beam can be used to quickly remove the formed diffraction pattern. Meanwhile, the hologram plate can be moved between a position for inputting a 3D image and a position for reproducing the 3D image. Effect of the Invention

[0176] A holographic recording medium according to one embodiment of the invention satisfies a specific elemental composition ratio, and thus not only has excellent optical recording characteristics, but also exhibits excellent durability against heat and moisture, suitable adhesion to transparent adhesives, and high transparency. [Brief description of the drawings]

[0177] [Figure 1] 1 is a schematic diagram showing the setup of a recording device for holographic recording. Specifically, Fig. 1 shows a process in which a laser of a predetermined wavelength is irradiated from a light source 10, and then passes through mirrors 20, 20', an iris 30, a spatial filter 40, an iris 30', a focusing lens 50, and a polarized beam splitter (PBS) 60, and is then irradiated onto a PP (holographic recording medium) 80 located on one side of a mirror 70. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0178] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, which are presented as examples of the present invention and are not intended to limit the scope of the invention in any way.

[0179] In the following Production Examples, Examples, Comparative Examples, and the like, the contents of raw materials and the like refer to the contents on a solid basis unless otherwise specified.

[0180] (Production Example 1: Production of (meth)acrylic polyol) In a 2L jacketed reactor, 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate were added and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60°C to 70°C, and stirring was continued for about 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was added and stirring was continued for about 30 minutes. Then, 0.24g of polymerization initiator AIBN was added, and polymerization was continued for more than 4 hours at the reaction temperature until the residual acrylate content was less than 1%, and a (meth)acrylate copolymer with hydroxyl groups located in the branched chain (weight average molecular weight about 300,000, OH equivalent about 1802g / equivalent) was produced.

[0181] (Production Example 2: Production of Fluorine-Based 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 placed, dissolved in 500 g of tetrahydrofuran, and 4.40 g of sodium hydroxide (60% dispersion in mineral oil) was carefully added several times while stirring at 0° C. After stirring for 20 minutes at 0° C., 12.50 mL of 2-methoxyethoxymethyl chloride was slowly added dropwise. After 1H NMR confirmed that all reactants had been consumed, work-up with dichloromethane gave 29g of liquid product with a purity of over 95% in a yield of 98%. The weight-average molecular weight of the produced fluorine-based compound was 586, and the refractive index measured by Abbe refractometer was 1.361.

[0182] (Example 1: Production of holographic recording medium) (1) Preparation of photopolymer composition Trimethylsilyl terminated poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number average molecular weight: about 390, SiH equivalent: about 103 g / equivalent) as a siloxane polymer and the (meth)acrylic polyol produced in Production Example 1 were mixed first. The content of the (meth)acrylic polyol was 17.95 g, and the siloxane polymer was added so that the molar ratio of SiH / OH was 2. In Example 1, 2.05 g of the siloxane polymer was added.

[0183] Then, 50g of HR6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.2g of a compound represented by the following formula a (Chemical Formula 12) as a photosensitive dye, 0.8g of hexadecyldimethylbenzylammonium tri(p-chlorophenyl)butylborate as a coinitiator, 0.05g of H-Nu254 (Spectra), 0.9g of Irgacure369 as a photoinitiator, 30g of the fluorine-based compound prepared in Preparation Example 2 as a plasticizer, and 206g of methyl isobutyl ketone (MIBK) as a solvent were added, and the mixture was stirred for about 30 minutes in a paste mixer while blocking light. Then, 0.014g of Karstedt (Pt-based) catalyst was added for matrix crosslinking to prepare a photopolymer composition.

[0184] [ka]

[0185] (2) Manufacturing of holographic recording media The photopolymer composition was coated to a predetermined thickness on a 60 μm thick TAC substrate using a Mayer bar and dried for 10 minutes at 80° C. After drying, the thickness of the photopolymer layer was about 15 μm.

[0186] A diffraction grating was recorded using the setup shown in Figure 1. Specifically, the manufactured photopolymer layer was laminated on a mirror, and then irradiated with a laser. A notch filter hologram with periodic refractive index modulation in the thickness direction can be recorded due to interference between the incident light L and the light L' reflected by the mirror. In this example, a notch filter hologram was recorded with an incident angle of 0° (degree). Notch filters and Bragg reflectors are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indices are repeatedly laminated periodically at a constant thickness.

[0187] (Examples 2 to 4 and Comparative Examples 1 to 5: Production of Holographic Recording Media) Holographic recording media were produced in the same manner as in Example 1, except that the component amounts of the photopolymer composition were changed as shown in Table 1 below.

[0188] [Table 1]

[0189] (1) Element ratio The element ratios on the surfaces of the samples before and after recording were analyzed by the method described below.

[0190] Specifically, the sample to be analyzed was fixed on copper foil with carbon tape, which was then placed on a sample holder and fixed with clips. Data was then obtained using an X-ray photoelectron spectrometer (ESCA, model name: K-Alpha+, Thermo Fisher Scientific Inc.) according to the K-Alpha+ standard operating method (SOP-0524-Ok), and the element ratios (atomic %) on the sample surface were analyzed using Avantage software (version 5.980).

[0191] The system specifications of the ESCA equipment used are as follows:

[0192] -Base chamber pressure:1.0×10 -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(FG03:100μA, 0.5V) For the surface of the as-received sample to be analyzed, an initial survey scan was performed under the following conditions to conduct qualitative analysis. According to the results of the qualitative analysis, quantitative analysis was carried out by narrow scan (snap) for each element. 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).

[0193] <Survey scan conditions> - Binding energy of scan range: -5 eV to 1350 eV - Step size: 1 eV - Per Point dwell time: 20 ms - Periods: 2 - Pass energy: 200 eV <narrow scan conditions> - Binding energy of scan range: 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 × 1.0 mm 2 - Mode: GCIB

[0194] (2) Diffraction efficiency (DE) The diffraction efficiency (η) was obtained by the following Equation 1 (Equation 2).

[0195]

number

[0196] In the above formula 1, η is the diffraction efficiency, P D is the power (mW / cm) of the diffracted beam from the sample after recording. 2 ), and P T is the power of the beam transmitted through the sample after recording (mW / cm 2 ).

[0197] (3) Heat resistance (ΔDE) The heat resistance was evaluated based on the degree of change in diffraction efficiency (ΔDE) before and after exposure to high temperature. Specifically, a diffraction grating was recorded on a sample before recording that was not exposed to high temperature and a sample before recording that was exposed to high temperature, and then the heat resistance was evaluated based on the degree of change in diffraction efficiency, which was calculated using the above formula 2.

[0198] In the above formula 2, DE0 is the diffraction efficiency measured for a sample on which a diffraction grating is recorded after storing the unrecorded sample in a dark room under constant temperature and humidity conditions of 20°C to 25°C and 40RH% to 50RH%, and DE1 is the diffraction efficiency measured for a sample on which a diffraction grating is recorded after storing the unrecorded sample in a dark room under high temperature conditions of 60°C to 70°C and 40RH% to 50RH%.

[0199] The diffraction grating was recorded in the manner described in Example 1, and the diffraction efficiency was calculated using Equation 1 above.

[0200] (4) Moisture and heat resistance (Δλ) The sample with the recorded diffraction grating was analyzed for the wavelength at which it exhibited maximum reflectance (i.e., minimum transmittance) under normal temperature and non-high humidity conditions. A UV-Vis spectrometer was used for the analysis, and the analysis wavelength range was 300 nm to 1,200 nm.

[0201] Thereafter, the same sample was stored for 72 hours under conditions of a temperature of 60° C. and a humidity of 90 RH%, and the wavelength showing the maximum reflectance (minimum transmittance) was analyzed in the same manner.

[0202] The humidity and heat resistance of the sample was confirmed by the degree of wavelength shift (Δλ) indicating the maximum reflectance before and after leaving it under high temperature and high humidity conditions. The smaller the absolute value of the degree of wavelength shift (Δλ) indicating the maximum reflectance, the better the humidity and heat resistance of the sample is evaluated to be.

[0203] (5)OCA adhesive strength The sample on which the diffraction grating was recorded was cut to a width of 25 mm. The photopolymer layer of the cut sample was then laminated with an optically clear adhesive (OCA), tesa (registered trademark) 61563 (thickness: 50 μm, TESA Corporation), and then bonded to the OCA using glass as a base plate.

[0204] The adhesive strength of the photopolymer layer attached to the OCA was measured using a Texture analyzer (LLOYD). The peel angle and peel speed during the adhesive strength measurement were 180° and 5 mm / sec, respectively.

[0205] (6) Hayes A 5 cm x 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 K 7136. The haze was measured three times in total, and the average value was calculated to determine the haze value of the sample.

[0206] [Table 2]

[0207] The element ratios on the surfaces of the samples before and after recording were measured, and the element ratios on the sample surfaces before and after recording were found to be the same.

[0208] Referring to Table 2, it is confirmed that when the fluorine ratio is low as in Comparative Example 1, the diffraction efficiency, moist heat resistance and haze are poor, and when the fluorine ratio is high as in Comparative Example 4, the adhesion is reduced. In addition, it is confirmed that when the silicon ratio is too high as in Comparative Example 2, the diffraction efficiency is poor, and when the silicon ratio is too low, the heat resistance and haze are poor as in Comparative Example 3, or the moist heat resistance is poor as in Comparative Example 5.

[0209] In contrast, it has been confirmed that the holographic recording medium according to one embodiment of the present invention has excellent diffraction efficiency, heat resistance, moist heat resistance, adhesive strength to OCA, and transparency by satisfying a predetermined element ratio.

Claims

1. The photopolymer layer includes a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol, or a precursor thereof, a photoreactive monomer, a photoinitiator system or a photopolymer obtained therefrom, and a fluorine-based compound; a hologram recording medium, wherein, relative to the total amount of carbon, nitrogen, oxygen, fluorine, and silicon atoms confirmed by photoelectron spectroscopy on the surface of the photopolymer layer, the elemental ratio of the carbon is 50 atomic % to 70 atomic %, the elemental ratio of the nitrogen is 0.01 atomic % to 2 atomic %, the elemental ratio of the oxygen is 15 atomic % to 30 atomic %, the elemental ratio of the fluorine is 3 atomic % to 12 atomic %, and the elemental ratio of the silicon is 3 atomic % to 15 atomic %.

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

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

4. 2. The holographic recording medium according to claim 1, wherein a molar ratio of silane functional groups of said siloxane polymer to hydroxy groups of said (meth)acrylic polyol is 1.5 to 4.

5. The photoreactive monomers include benzyl (meth)acrylate, benzyl 2-phenyl acrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, and phenol (ethylene oxide) ２ one or more monofunctional monomers selected from the group consisting of (meth)acrylate, O-phenylphenol(ethylene oxide)(meth)acrylate, phenylthioethyl(meth)acrylate, and biphenylmethyl(meth)acrylate; bisphenol A(ethylene oxide) ２～１０ 2. 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, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolac epoxy (meth)acrylate; or a mixture of two or more thereof.

6. 2. The holographic recording medium according to claim 1, wherein the photoreactive monomer is contained in an amount of 50 to 300 parts by weight with respect to 100 parts by weight of the polymer matrix.

7. The holographic recording medium of claim 1 , wherein the photoinitiator system comprises a photosensitive dye and a coinitiator.

8. The photosensitive dye includes a silicon rhodamine compound represented by the following chemical formula 3: 【Transformation 3】 In the above Chemical Formula 3, R ２１ ~R ２９ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms; d and e are each independently an integer of 0 to 3; f is an integer from 0 to 5, An － The holographic recording medium according to claim 7 , wherein is an anion.

9. The coinitiator includes a borate anion represented by the following chemical formula 4: 【Chemistry 4】 In the above formula 4, X １ ~X ４ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, and X １ ~X ４ The holographic recording medium according to claim 7 , wherein at least one of is not an aryl group.

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

11. 2. The holographic recording medium of claim 1, wherein the photopolymer layer contains 17% by weight to 38% by weight of a polymer matrix, 36% by weight to 58% by weight of a photoreactive monomer, and 17% by weight to 38% by weight of a fluorine-based compound, based on the total weight of the polymer matrix, the photoreactive monomer, and the fluorine-based compound.

12. 2. The holographic recording medium according to claim 1, wherein when a notch filter hologram is recorded, the diffraction efficiency is 80% or more.

13. The diffraction efficiency change value ΔDE calculated by the following formula 2 (Mathematical Formula 1) is 10% or less, [Equation 1] In the above formula 2, DE ０ is the diffraction efficiency measured for a hologram recording medium on which a notch filter hologram is recorded after storing the hologram recording medium before recording in a dark room under constant temperature and humidity conditions of 20°C to 25°C and 40RH% to 50RH%, and DE １ is a diffraction efficiency measured for a hologram recording medium on which a notch filter hologram is recorded, after storing the hologram recording medium before recording in a dark room under high-temperature conditions of 60°C to 70°C and 40 RH% to 50 RH%.

14. 2. The holographic recording medium according to claim 1, wherein the degree of wavelength shift showing the maximum reflectance before and after storage for 72 hours under conditions of a temperature of 60° C. and a relative humidity of 90% is −10 nm to 10 nm.

15. 2. The holographic recording medium according to claim 1, wherein the photopolymer layer has an adhesive strength of 1000 gf / 25 mm or more to an optically transparent adhesive.

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

17. forming a photopolymer layer by applying a photopolymer composition including a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic polyol, or a precursor thereof, a fluorine-based compound, a photoreactive monomer, and a photoinitiator system; a coherent laser is irradiated onto a predetermined region of the photopolymer layer to selectively polymerize a photoreactive monomer contained in the photopolymer layer, thereby recording optical information; a photopolymer layer having an elemental ratio of carbon of 50 atomic % to 70 atomic %; an elemental ratio of nitrogen of 0.01 atomic % to 2 atomic %; an elemental ratio of oxygen of 15 atomic % to 30 atomic %; an elemental ratio of fluorine of 3 atomic % to 12 atomic %; and an elemental ratio of silicon of 3 atomic % to 15 atomic % relative to the total amount of carbon, nitrogen, oxygen, fluorine, and silicon atoms confirmed on the surface by photoelectron spectroscopy.

18. 18. The method for producing a holographic recording medium according to claim 17, wherein the photopolymer composition contains a Pt-based catalyst, and the Pt-based catalyst is contained in an amount of 0.01 to 0.30 parts by weight per 100 parts by weight of the (meth)acrylic polyol.

19. 18. The method for producing a holographic recording medium according to claim 17, wherein in the step of forming the photopolymer layer, the coating film formed by applying the photopolymer composition is dried at 50°C to 120°C.

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

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