Photopolymer composition, photopolymer film, holographic recording medium, optical element, and holographic recording method

Abstract

The present invention relates to a photopolymer composition for forming a hologram, and a photopolymer film, a holographic recording medium, a holographic recording method, and an optical element using the same. The photopolymer composition contains a monofunctional monomer having a low molecular weight, and can provide a photopolymer film, a holographic recording medium, and an optical element including the same, which achieves diffraction efficiency and high refractive index modulation even at a thin thickness, has excellent recording efficiency, exhibits excellent durability in high-temperature and high-humidity environments, and has excellent haze, adhesion, and bonding properties.

Description

[Technical Field]

[0001] [Cross-Citation of Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0151484 dated November 14, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a photopolymer composition for forming a hologram, a photopolymer film, a holographic recording medium, an optical element, and a holographic recording method. [Background technology]

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

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

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

[0006] This local photopolymerization process generates refractive index modulation, which then generates a diffraction grating. The refractive index modulation value (Δn) affects the thickness of the photopolymer film and the diffraction efficiency (DE), and the thinner the thickness, the wider the angular selectivity.

[0007] In recent years, there has been an increasing demand for the development of materials that can achieve high diffraction efficiency and stable hologram maintenance, and various attempts have been made to manufacture photopolymer films that have high diffraction efficiency and refractive index modulation values ​​despite their thin thickness.

[0008] On the other hand, when a holographic recording medium is used as an optical element in applications such as mobile devices and vehicle accessories (e.g., head-up displays), it is placed in a high-temperature / high-humidity environment, in which case the diffraction grating of the holographic recording medium may be deformed by the external environment, resulting in a decrease in clarity and visibility.

[0009] That is, the high heat resistance and humidity resistance reliability of the photopolymer film contained in holographic optical elements (HOEs) play an important role in preventing changes in recording wavelength due to high temperature and humidity environments in products to which the film is applied. Furthermore, the haze characteristics of the photopolymer film after recording improve clarity and visibility when viewing the outside through the film when the film is commercialized. Furthermore, the adhesiveness and adhesion properties of the photopolymer film also prevent deformation of the photopolymer film due to the external environment.

[0010] However, currently used holographic recording media do not exhibit heat resistance and humidity / heat resistance reliability that can prevent deformation due to high temperature / high humidity environments.

[0011] Therefore, there is a need to develop a photopolymer film that minimizes deformation of the film even in various surrounding environments and has excellent recording efficiency and reliability, as well as a holographic recording medium including the same. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention provides a photopolymer composition for forming a hologram, which can realize a higher refractive index modulation value even in a thin thickness range by adjusting the content ratio of a monofunctional monomer having a low molecular weight among recording monomers, and at the same time can efficiently provide a photopolymer layer having high recording efficiency (diffraction efficiency), excellent heat resistance, moist heat resistance reliability, haze, adhesive strength, and adhesion properties.

[0013] The present invention also provides a photopolymer film and a holographic recording medium including the same, which include a photopolymer layer using the photopolymer composition, which has high recording efficiency (diffraction efficiency), excellent heat resistance, excellent humidity and heat resistance reliability, haze, adhesive strength, and adhesion properties, and which can prevent deformation of the outer shape due to the external environment.

[0014] The present invention also provides a recording method for the holographic recording medium.

[0015] The present invention also provides an optical element including a holographic recording medium. [Means for solving the problem]

[0016] As used herein, the present invention relates to 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 including a monofunctional monomer and a polyfunctional monomer; and a photoinitiator; The photopolymer composition for forming a holographic recording medium contains 42 to 55 parts by weight of a monofunctional monomer based on 100 parts by weight of the photoreactive monomer.

[0017] Also provided herein is a photopolymer film comprising: a substrate film; and a coating layer comprising the photopolymer composition.

[0018] The present specification also provides a holographic recording medium including the photopolymer film.

[0019] The present specification also provides an optical element including the holographic recording medium.

[0020] Also provided herein is a holographic recording method, which includes the step of selectively polymerizing a photoreactive monomer and a monofunctional monomer contained in the photopolymer composition by a coherent laser.

[0021] Hereinafter, a photopolymer composition, a photopolymer film, a holographic recording medium, a method for producing the same, and an optical element including the same according to specific embodiments of the present invention will be described.

[0022] As used herein, (meth)acrylate means methacrylate or acrylate.

[0023] In this specification, the (co)polymer means a homopolymer or a copolymer (including a random copolymer, a block copolymer, and a graft copolymer).

[0024] In this specification, the term "hologram" refers to a recording medium in which optical information is recorded in the entire visible and near-ultraviolet ranges (300-800 nm) through an exposure process, and includes all visual holograms, such as in-line (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white-light transmission holograms ("rainbow holograms"), Denisyuk holograms, biaxial reflection holograms, edge-literature holograms, and holographic stereograms.

[0025] In this specification, the alkyl group may be linear or branched, and the number of carbon atoms is not particularly limited, but preferably is 1 to 40. According to one embodiment, the alkyl group has 1 to 20 carbon atoms. According to another embodiment, the alkyl group has 1 to 10 carbon atoms. According to yet another embodiment, the alkyl group has 1 to 6 carbon atoms. Specific examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methylbutyl, 1-ethylbutyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethylpropyl, 1,1-dimethylpropyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, and the like.

[0026] In this specification, the alkylene group refers to a divalent functional group derived from an alkane, and is, for example, linear, branched, or cyclic, and examples thereof include a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, and a hexylene group.

[0027] As used herein, the term "substituted or unsubstituted" refers to a group selected from the group consisting of deuterium, halogen, cyano, nitro, hydroxy, carbonyl, ester, imide, amido, primary amino, carboxy, sulfonic acid, sulfonamido, phosphine oxide, alkoxy, aryloxy, alkylthioxy, arylthioxy, alkylsulfoxy, arylsulfoxy, silyl, boron, alkyl, haloalkyl, cycloalkyl, alkenyl, aryl, aralkyl, aralkenyl, alkylaryl, alkoxysilylalkyl, arylphosphine, or heterocyclic groups containing one or more N, O, and S atoms, or a group in which two or more of the above-listed substituents are linked together. For example, a "substituent having two or more linked substituents" may be a biphenyl group. That is, a biphenyl group may be an aryl group or may be interpreted as a substituent in which two phenyl groups are linked together. Preferably, a halogen group can be used as the substituent, and an example of the halogen group can be a fluoro group.

[0028] Unless otherwise specified, the term "hologram" as used herein refers to a recording medium in which optical information is recorded in the entire visible and ultraviolet ranges (e.g., 300-1,200 nm) through an exposure process. For example, the term "hologram" as used herein may include visual holograms such as in-line (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white-light transmission holograms ("rainbow holograms"), Denisyuk holograms, biaxial reflection holograms, edge-literature holograms, and holographic stereograms.

[0029] In this specification, in relation to the environmental conditions in which a holographic recording medium or an element including the same is placed, the term "high temperature" can refer to a temperature of 60°C or higher. For example, the high temperature can refer to a temperature of 65°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, 85°C or higher, or 90°C or higher. The upper limit of the temperature is not particularly limited, and can be, for example, 110°C or lower, 105°C or lower, 100°C or lower, 95°C or lower, 90°C or lower, 85°C or lower, or 80°C or lower. When temperature affects the characteristics of a substance, object, or each component, unless temperature is specifically mentioned, the temperature conditions under which the characteristics are measured or described can refer to room temperature (e.g., a temperature in the range of about 15 to 30°C, where no particular heating or cooling is performed).

[0030] Furthermore, in this specification, the term "high humidity" in relation to the environmental conditions in which a holographic recording medium or an element including the same is placed can refer to a relative humidity of 80% or higher. For example, a high humidity condition can refer to a condition satisfying a relative humidity of 85% or higher, 90% or higher, or 95% or higher. When humidity affects the characteristics of a substance, object, or each component, unless otherwise specified, the humidity condition under which the characteristics are measured or described can be a relative humidity condition lower than the high humidity condition, for example, a relative humidity condition in the range of 15% or higher to less than 80%. Specifically, the humidity condition can refer to a relative humidity condition having a lower limit of 20% or higher, 25% or higher, 30% or higher, 35% or higher, or 40% or higher and an upper limit of 75% or lower, 70% or lower, 65% or lower, or 60% or lower.

[0031] In addition, in this specification, the high temperature / high humidity conditions may refer to environmental conditions that satisfy at least one of the high temperature conditions and the high humidity conditions described above.

[0032] In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) refer to the molecular weight (unit: Da (Dalton)) measured in terms of polystyrene by gel permeation chromatography (GPC). The measurement of the weight-average molecular weight measured in terms of polystyrene by GPC can be performed using a commonly known analytical device, a detector such as a refractive index detector, and an analytical column, and can be performed under commonly used temperature conditions, solvents, and flow rates. Specific examples of the measurement conditions include a temperature of 30°C, a chloroform solvent, and a flow rate of 1 mL / min. Specific examples of the measurement conditions include using a Polymer Laboratories PLgel MIX-B 300 mm column and a Waters PL-GPC220 instrument, with an evaluation temperature of 160°C, 1,2,4-trichlorobenzene as the solvent, a flow rate of 1 mL / min, and a sample prepared at a concentration of 10 mg / 10 mL and supplied in a volume of 200 μL. Mw and Mn values ​​can be determined using a calibration curve formed using polystyrene standards. Nine molecular weights of polystyrene standards were used: 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

[0033] According to one embodiment of the present invention, there is provided a photopolymer composition for forming a holographic recording medium, comprising: 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 including a monofunctional monomer and a polyfunctional monomer; and a photoinitiator; wherein the monofunctional monomer is contained in an amount of 42 to 55 parts by weight based on 100 parts by weight of the photoreactive monomer.

[0034] The present inventors have confirmed that by using a low molecular weight acrylate compound and a monofunctional monomer together with a photoreactive monomer as the recording material of a holographic recording medium and adjusting the ratio of their use, the recording efficiency of the photopolymer layer of the holographic recording medium is superior to conventional methods, and that deformation of the photopolymer film due to high temperature / high humidity external environments can be prevented by improving heat resistance, humidity and heat resistance reliability, haze, adhesion and adhesion properties. This has led to the completion of the present invention.

[0035] That is, the present invention provides a photopolymer composition in which the ratio of the monofunctional monomer in the recording monomer is adjusted within a specific range, thereby achieving high heat resistance and high humidity and heat resistance reliability of the photopolymer film contained in a holographic optical element (HOE). Therefore, the present invention can prevent changes in recording wavelength even in high temperature / high humidity environments of film-applied products using the photopolymer composition, and exhibit excellent haze characteristics, adhesion, and bonding properties. As a result, the present invention can provide a holographic recording medium with excellent clarity and visibility, and an optical element including the same with excellent performance.

[0036] Here, the adhesiveness refers to the degree of adhesion between the photopolymer film and the OCA (Optical Clear Adhesive) film, and the adhesion refers to the degree of adhesion between the photopolymer layer using the photopolymer composition and the substrate when manufacturing the photopolymer film.

[0037] Hereinafter, a photopolymer composition according to one embodiment of the present invention, a photopolymer film formed from the photopolymer composition, a holographic recording medium, a holographic recording method, and an optical element including the holographic recording medium will be described in more detail.

[0038] The photopolymer composition of one embodiment includes a polymeric matrix, or a precursor thereof, that acts as a support for the photopolymer layer that will be formed therefrom.

[0039] The polymer matrix is ​​formed by crosslinking a siloxane-based polymer containing one or more silane functional groups (Si-H) with a (meth)acrylic polyol. Specifically, the polymer matrix is ​​formed by crosslinking a (meth)acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxyl groups of the (meth)acrylic polyol can form crosslinks with the silane functional groups of the siloxane-based polymer through a hydrosilylation reaction. The hydrosilylation reaction can proceed rapidly in the presence of a Pt catalyst even at room temperature (e.g., a temperature in the range of about 15 to 30°C, i.e., a temperature in an unheated or unheated state). Therefore, the photopolymer composition of the embodiment employs a polymer matrix that can be rapidly crosslinked even at room temperature as a support, thereby improving the manufacturing efficiency and productivity of holographic recording media.

[0040] The polymer matrix can enhance the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer layer due to the flexible main chain of the siloxane-based polymer. In addition, the siloxane bond, which has excellent heat resistance and humidity resistance, can easily ensure the reliability of the photopolymer layer on which optical information is recorded and the holographic recording medium including the same.

[0041] The polymer matrix may also have a relatively low refractive index, thereby enhancing the refractive index modulation of the photopolymer film. For example, the upper limit of the refractive index of the polymer matrix may be 1.53 or less, 1.52 or less, 1.51 or less, 1.50 or less, or 1.49 or less. The lower limit of the refractive index of the polymer matrix may be, for example, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more. In this specification, the "refractive index" may be a value measured using an Abbe refractometer at 25°C.

[0042] The photopolymer composition of the present invention may include the crosslinked polymer matrix or a precursor thereof. When the photopolymer composition includes a precursor of the polymer matrix, the precursor may include a siloxane-based polymer, a (meth)acrylic polyol, and a Pt-based catalyst.

[0043] As a specific example, the siloxane-based polymer may include a repeating unit represented by the following Chemical Formula 1 and a terminal group represented by the following Chemical Formula 2:

[0044] [ka]

[0045] 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,

[0046] [ka]

[0047] 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 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 these is hydrogen.

[0048] In Chemical Formula 2, -(O)- means that when Si of the terminal group represented by Chemical Formula 2 is bonded to the repeating unit represented by Chemical Formula 1, the bond is via oxygen (O) or directly without oxygen (O).

[0049] As used herein, the term "alkyl group" may be a straight-chain, branched-chain, or cyclic alkyl group. Non-limiting examples of the term "alkyl group" include methyl, ethyl, propyl (e.g., n-propyl, isopropyl, etc.), butyl (e.g., n-butyl, isobutyl, tert-butyl, sec-butyl, cyclobutyl, etc.), pentyl (e.g., n-pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, cyclopentyl, etc.), hexyl (e.g., n-hexyl, 1-methylpentyl, 2-methylpentyl, etc.), and the like. butyl, 4-methylpentyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, cyclopentylmethyl, cyclohexyl, etc.), heptyl (e.g., n-heptyl, 1-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclohexylmethyl, etc.), octyl (e.g., n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, etc.), nonyl (e.g., n-nonyl, 2,2-dimethylheptyl, etc.), and the like.

[0050] For example, R in Formulas 1 and 2 1 , 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 the R in Formula 1 may be hydrogen. 1 and R 2 are methyl and hydrogen, respectively, and R 11 ~R 13are each independently methyl or hydrogen (e.g., polymethylhydrosiloxane having a terminal trimethylsilyl group or dimethylhydrosilyl group); 1 and R 2 are methyl and hydrogen, respectively, and the remaining R 1 and R 2 are all methyl, and R in the above Chemical Formula 2 11 ~R 13 are each independently methyl or hydrogen (e.g., poly(dimethylsiloxane-co-methylhydrosiloxane) having a terminal trimethylsilyl group or a dimethylhydrosilyl group); or R 1 and R 2 are all methyl, and R in the above Chemical Formula 2 11 ~R 13 and the remaining groups are each independently methyl or hydrogen (for example, polydimethylsiloxane in which one or all of the terminal groups are dimethylhydrosilyl groups).

[0051] The siloxane-based compound may have a number-average molecular weight (Mn) ranging from 200 to 4,000. Specifically, the lower limit of the number-average molecular weight of the siloxane-based polymer may be, for example, 200 or more, 250 or more, 300 or more, or 350 or more, and the upper limit may be, for example, 3,500 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less. When the number-average molecular weight of the siloxane-based polymer satisfies the above range, problems such as volatilization of the siloxane-based polymer during crosslinking with a (meth)acrylic polyol at room temperature or higher, resulting in a reduced degree of matrix crosslinking, or poor compatibility of the siloxane-based polymer with other components of the photopolymer composition, resulting in phase separation from these components, can be prevented. This allows holographic recording media formed from the photopolymer composition to exhibit excellent optical recording properties and excellent durability under high-temperature / high-humidity conditions.

[0052] The number average molecular weight refers to the number average molecular weight (unit: g / mol) measured in terms of polystyrene by GPC. The process of measuring the number average molecular weight measured in terms of polystyrene by GPC can use a commonly known analytical device, a detector such as a refractive index detector, and an analytical column, and commonly used temperature conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30°C, tetrahydrofuran solvent, and a flow rate of 1 mL / min.

[0053] The (meth)acrylic polyol may refer to a polymer in which one or more, specifically two or more, hydroxy groups are bonded to the main chain or side chain of a (meth)acrylate polymer. In this specification, unless otherwise specified, "(meth)acrylic (based)" refers to acrylic (based) and / or methacrylic (based), and is a term that includes all of acrylic (based), methacrylic (based), and a mixture of acrylic (based) and methacrylic (based).

[0054] The (meth)acrylic polyol may be a homopolymer of a (meth)acrylate monomer having a hydroxy group, a copolymer of two or more (meth)acrylate monomers having a hydroxy group, or a copolymer of a (meth)acrylate monomer having a hydroxy group and a (meth)acrylate monomer not having a hydroxy group. In this specification, the term "copolymer" includes all of random copolymers, block copolymers, and graft copolymers, unless otherwise specified.

[0055] 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 monomer 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.

[0056] The (meth)acrylic polyol may have a weight-average molecular weight (Mw) of, for example, 150,000 to 1,000,000. The weight-average molecular weight refers to a weight-average molecular weight in terms of polystyrene measured by the aforementioned GPC method. For example, the lower limit of the weight-average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, for example, 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less, or 450,000 or less. When the weight-average molecular weight of the (meth)acrylic polyol satisfies the above range, the polymer matrix can fully function as a support, and the deterioration of the optical information recording properties is small even after use. Furthermore, the polymer matrix can be given sufficient flexibility to improve the mobility of components (e.g., photoreactive monomers or plasticizers) contained in the photopolymer composition, thereby minimizing the deterioration of the optical information recording properties.

[0057] In order to adjust the crosslink density of the (meth)acrylic polyol with the siloxane polymer to a level advantageous for ensuring the functionality of the holographic recording medium, the hydroxyl equivalent of the (meth)acrylic polyol can be adjusted to an appropriate level.

[0058] Specifically, the hydroxyl (—OH) equivalent of the (meth)acrylic polyol may be, for example, within a range of 500 to 3,000 g / equivalent. More specifically, the lower limit of the hydroxyl (—OH) equivalent of the (meth)acrylic polyol may be 600 g / equivalent or more, 700 g / equivalent or more, 800 g / equivalent or more, 900 g / equivalent or more, 1000 g / equivalent or more, 1100 g / equivalent or more, 1200 g / equivalent or more, 1300 g / equivalent or more, 1400 g / equivalent or more, 1500 g / equivalent or more, 1600 g / equivalent or more, 1700 g / equivalent or more, or 1750 g / equivalent or more. The upper limit of the hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol may be 2900 g / equivalent or less, 2800 g / equivalent or less, 2700 g / equivalent or less, 2600 g / equivalent or less, 2500 g / equivalent or less, 2400 g / equivalent or less, 2300 g / equivalent or less, 2200 g / equivalent or less, 2100 g / equivalent or less, 2000 g / equivalent or less, or 1900 g / equivalent or less. The hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol is the equivalent weight (g / equivalent) per hydroxy functional group, and is calculated by dividing the weight-average molecular weight of the (meth)acrylic polyol by the number of hydroxy functional groups per molecule. The smaller the equivalent weight value, the higher the functional group density, and the larger the equivalent weight value, the lower the functional group density. When the equivalent weight of the hydroxyl group (—OH) of the (meth)acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslink density, fully functions as a support, the fluidity of the components contained in the layer formed from the photopolymer composition is improved, there is no problem of the boundary surface of the diffraction grating formed after recording collapsing, the initial refractive index modulation value is maintained at an excellent level even over time, and the deterioration of the recording characteristics for optical information can be minimized.

[0059] The (meth)acrylic polyol may have a glass transition temperature (Tg) in the range of, for example, −60 to −10°C. Specifically, the lower limit of the glass transition temperature may be, for example, −55°C or higher, −50°C or higher, −45°C or higher, −40°C or higher, −35°C or higher, −30°C or higher, or −25°C or higher, and the upper limit may be, for example, −15°C or lower, −20°C or lower, −25°C or lower, −30°C or lower, or −35°C or lower. When the glass transition temperature falls within the above range, the glass transition temperature can be lowered without significantly reducing the modulus of the polymer matrix, thereby increasing the mobility (fluidity) of other components in the photopolymer composition and improving the moldability of the photopolymer composition. The glass transition temperature is measured using a known method, such as DSC (Differential Scanning Calorimetry) or DMA (Dynamic Mechanical Analysis).

[0060] The refractive index of the (meth)acrylic polyol may be, for example, 1.40 or more and less than 1.50. Specifically, the lower limit of the refractive index of the (meth)acrylic polyol may be, for example, 1.41 or more, 1.42 or more, 1.43 or more, 1.44 or more, 1.45 or more, or 1.46 or more, and the upper limit may be, for example, 1.49 or less, 1.48 or less, 1.47 or less, 1.46 or less, or 1.45 or less. When the (meth)acrylic polyol has a refractive index within the above range, it can contribute to enhancing refractive index modulation. The refractive index of the (meth)acrylic polyol is a theoretical refractive index and can be calculated using the refractive index of the monomers used in producing the (meth)acrylic polyol (measured at 25°C using an Abbe refractometer) and the fraction (molar ratio) of each monomer.

[0061] The (meth)acrylic polyol and siloxane polymer can be used so that the molar ratio (SiH / OH) of the silane functional groups (Si-H) of the siloxane polymer to the hydroxy groups (-OH) of the (meth)acrylic polyol is 0.80 to 3.5. That is, the types and contents of the siloxane polymer and the (meth)acrylic polyol can be selected so as to satisfy this molar ratio when forming the polymer matrix. The lower limit of the molar ratio (SiH / OH) can be, for example, 0.81 or more, 0.85 or more, 0.90 or more, 0.95 or more, 1.00 or more, or 1.05 or more, and the upper limit can be, for example, 3.4 or less, 3.3 or less, 3.2 or less, 3.2 or less, 3.05 or less, or 3.0 or less. When the molar ratio (SiH / OH) satisfies this range, the polymer matrix is ​​crosslinked at an appropriate crosslink density, improving reliability under high-temperature / high-humidity conditions and achieving a sufficient refractive index modulation value.

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

[0063] Meanwhile, the photopolymer composition of the embodiment has a feature that when a photoreactive monomer is constituted as a recording monomer, the thickness of the erosion layer is controlled by adjusting the content of a monofunctional monomer such as a low molecular weight acrylate to a specific amount.

[0064] According to the present specification, the term "erosion layer" refers to a holographic recording medium including a photopolymer film in which a coating layer (coating layer including a hologram recording layer) containing a photopolymer composition is formed on a substrate, and the addition of a monofunctional monomer among recording monomers for hologram recording causes the monofunctional monomer to invade the substrate layer, resulting in an erosion phenomenon in the film membrane.

[0065] Therefore, the photopolymer film according to the embodiment may include a substrate film and a coating layer including a photopolymer composition, and may further include an erosion layer between the substrate film and the recording layer.

[0066] Specifically, a hologram recording medium can be manufactured by irradiating an object beam and a reference beam onto a photopolymer layer formed from the photopolymer composition. The interference between the object beam and the reference beam inhibits or prevents photopolymerization of the photoreactive monomer in the destructive interference region, while photopolymerization of the photoreactive monomer occurs in the constructive interference region. As the photoreactive monomer is continuously consumed in the constructive interference region, a difference in concentration of the photoreactive monomer occurs between the destructive interference region and the constructive interference region, resulting in the photoreactive monomer in the destructive interference region diffusing into the constructive interference region. The resulting refractive index modulation generates a diffraction grating.

[0067] Therefore, the photoreactive monomer may include a compound having a higher refractive index than the polymer matrix in order to achieve the above-mentioned refractive index modulation. However, it is not limited that all of the photoreactive monomers included in the photopolymer composition of the embodiment 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 achieve a high refractive index modulation value.

[0068] The photoreactive monomer includes a monofunctional monomer and a polyfunctional monomer, and the polyfunctional monomer may be at least one selected from the group consisting of a bifunctional monomer and a trifunctional monomer.

[0069] Generally, if the proportion of polyfunctional monomers in the photopolymer composition liquid is too high, the recording efficiency will decrease, the haze will increase due to miscibility, and the adhesive strength and adhesion strength will decrease, which may result in poor heat resistance and humidity and heat resistance reliability due to external environmental factors. On the other hand, if the proportion of monofunctional monomers is too high, there will be a problem of low recording efficiency.

[0070] By adjusting the ratio of the low molecular weight acrylate used as the monofunctional monomer, it can have a high refractive index, contribute to refractive index modulation through photoreaction, and easily infiltrate into the substrate layer, thereby inducing an erosion layer in a coating layer containing the photopolymer composition of a holographic recording medium, thereby contributing to high heat resistance and humidity and heat resistance reliability. Therefore, in the present invention, by adjusting the content of the monofunctional monomer in the recording monomer, the degree of induction of the erosion layer can be controlled, thereby achieving excellent recording efficiency and excellent effects on all photopolymer properties such as heat resistance, humidity and heat resistance reliability, haze, adhesive strength, and adhesion strength.

[0071] Specifically, by adjusting the content of the monofunctional monomer, the thickness of the erosion layer in the film including the coating layer can be 10% to 50% of the total thickness of the film including the coating layer.

[0072] In other words, the photopolymer film is characterized in that the thickness ratio of the eroded layer to the coating layer satisfies the condition of the following formula 1.

[0073] [Formula 1] 10%≦(thickness of the eroded layer of the photopolymer film coating layer / total thickness of the photopolymer film coating layer)×100≦50%

[0074] In addition, by including the monofunctional monomer in a specific ratio among the photoreactive monomers, the formed holographic recording medium can have a diffraction efficiency of 90% or more even at a thin thickness, heat resistance and humidity and heat resistance reliability of 10 nm or less, haze of 1.5% or less, adhesive strength (180° Peel test) of 1000 g / 25 mm or more, and adhesion strength of 4B or more.

[0075] In this case, the monofunctional monomer may be included in an amount of 42 to 55 parts by weight, or 43 to 53 parts by weight, or 43 to 52 parts by weight, based on 100 parts by weight of the photoreactive monomer. If the content of the monofunctional monomer is 40 parts by weight or less, problems with recording efficiency, heat resistance, moist heat resistance reliability, and adhesive strength and adhesion may occur, while if it is 55 parts by weight or more, problems with low recording efficiency may occur. More specifically, based on 100 parts by weight of the total weight of the photoreactive monomer, the content of the monofunctional monomer in the total photoreactive monomer may be adjusted to a range of 42 to 55 parts by weight by mixing the monofunctional monomer with the polyfunctional monomer and adjusting the ratio.

[0076] The monofunctional monomer may be a monofunctional (meth)acrylate monomer. Specifically, the monofunctional monomer may have a weight average molecular weight of 50 g / mol to 400 g / mol, or 200 g / mol to 300 g / mol. The weight average molecular weight refers to a weight average molecular weight measured by GPC in terms of polystyrene.

[0077] More specifically, the monofunctional monomer may include one or more monofunctional (meth)acrylate monomers selected from the group consisting of phenoxybenzyl (meth)acrylate, o-phenylphenol ethylene oxide (meth)acrylate, benzyl (meth)acrylate, 2-(phenylthio)ethyl (meth)acrylate, and biphenyl methyl (meth)acrylate. The monofunctional monomer may exhibit the weight average molecular weight range by adjusting the chain length through a combination of the one or more monofunctional monomers.

[0078] More specifically, the monofunctional monomer may include at least one selected from the group consisting of benzyl (meth)acrylate (Miwon Corporation, M1182, refractive index 1.5140), phenoxybenzyl (meth)acrylate (Miwon Corporation, M1122, refractive index 1.565), O-phenylphenol (EO) (meth)acrylate (Miwon Corporation, M1142, refractive index 1.577), and 2-(phenylthio)ethyl (meth)acrylate (Miwon Corporation, M1162, refractive index 1.560).

[0079] Furthermore, the polyfunctional monomer used as the recording monomer may include a polyfunctional (meth)acrylate monomer.

[0080] Specifically, the polyfunctional monomer may include one or more selected from the group consisting of bifunctional and trifunctional monomers having two to three 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.

[0081] The polyfunctional monomer may be, for example, a polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more, or 1.53 or more, or 1.5 to 1.7. Such a polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more, or 1.53 or more, or 1.5 to 1.7 may contain a halogen atom (such as bromine or iodine), sulfur (S), phosphorus (P), or an aromatic ring.

[0082] More specific examples of the polyfunctional (meth)acrylate monomer having a refractive index of 1.5 or more include one or more selected from bisphenol A modified diacrylates, fluorene acrylates (HR6022, etc., Miwon), bisphenol fluorene epoxy acrylates (HR6100, HR6060, HR6042, etc., Miwon), and halogenated epoxy acrylates (HR1139, HR3362, etc., Miwon).

[0083] More specifically, the polyfunctional monomer is 9,9-bis[4-(2-acryloyloxyethyloxy)phenyl]fluorene, bisphenol A (ethylene oxide), 2~10 Di(meth)acrylate (bisphenol A (EO) 2~10 (meth)acrylate; Miwon's M240 refractive index 1.537, M241 refractive index 1.529, M244 refractive index 1.545, M245 refractive index 1.537, M249 refractive index 1.542, M2100 refractive index 1.516, M2101 refractive index 1.512), bisphenol A epoxy di(meth)acrylate (Miwon's PE210 refractive index 1.557, PE2120A refractive index 1.533, PE2120B refractive index 1.534, PE2020C refractive index 1.539, PE2120S refractive index 1.556), bisfluorene di(meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR6042 The refractive index may be one or more selected from the group consisting of bisphenol A fluorene di (meth)acrylate (HR6060 refractive index 1.584, HR6100 refractive index 1.562, HR6200 refractive index 1.530, manufactured by Miwon).

[0084] Meanwhile, the polyfunctional monomer may have a weight average molecular weight of 200 g / mol to 1000 g / mol, or 400 g / mol to 600 g / mol. The weight average molecular weight means a weight average molecular weight in terms of polystyrene measured by a GPC method.

[0085] In one embodiment, the photopolymer composition may include 50 to 300 parts by weight of the photoreactive monomer relative to 100 parts by weight of the polymer matrix or its precursor. For example, the lower limit of the content of the photoreactive monomer may be 50 parts by weight or more, 55 parts by weight or more, or 60 parts by weight or more, and the upper limit may be 300 parts by weight or less, 290 parts by weight or less, 285 parts by weight or less, or 280 parts by weight or less. In this case, the reference content of the polymer matrix refers to the combined content (by weight) of the (meth)acrylic polyol and siloxane polymer that form the matrix. Meeting this range is advantageous in ensuring excellent optical recording properties and durability in high-temperature / high-humidity environments.

[0086] The photopolymer composition of the embodiment includes a photoinitiator, which is a compound that is activated by light or actinic radiation to initiate polymerization of compounds that contain photoreactive functional groups, such as the photoreactive monomers.

[0087] As the photoinitiator, any commonly known photoinitiator can be used without any significant limitation, and specific examples thereof include a photoradical polymerization initiator, a photocationic polymerization initiator, or a photoanionic polymerization initiator.

[0088] Specific examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, and amine derivatives. More specifically, examples of the photoradical polymerization initiator include 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, and 2,2-dimethoxy-1,2-diphenylethane-1-one (product name: Irgacure651 / BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Irgacure 184 / manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (product name: Irgacure 369 / manufacturer: BASF), and bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium (product name: Irgacure 784 / manufacturer: BASF), Ebecryl Examples include the P-115 (manufacturer: SK entis).

[0089] Examples of the cationic photopolymerization initiator include diazonium salts, sulfonium salts, and iodonium salts, such as sulfonic acid esters, imidosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, and (η-benzene)(η-cyclopentadienyl)iron(II). Other examples include benzoin tosylate, 2,5-dinitrobenzyl tosylate, and N-tosylphthalimide. Specific examples of the cationic photopolymerization initiator include commercially available products such as Cyracure UVI-6970, Cyracure UVI-6974, and Cyracure UVI-6990 (manufacturer: Dow Chemical Co., Inc., USA), Irgacure 264 and Irgacure 250 (manufacturer: BASF), and CIT-1682 (manufacturer: Nippon Soda).

[0090] Examples of the photoanionic polymerization initiator include borate salts, such as butylyl chlorine butyltriphenylborate. More specific examples of the photoanionic polymerization initiator include commercially available products such as Borate V (manufacturer: Spectra Group).

[0091] The photopolymer compositions of the present invention can also use unimolecular (Type I) or bimolecular (Type II) initiators. (Type I) systems for free radical photopolymerization include, for example, aromatic ketone compounds combined with tertiary amines, such as benzophenone, alkylbenzophenones, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), anthrone, and halogenated benzophenones, or mixtures of these types. (Type II) bimolecular initiators include benzoin and its derivatives, benzil ketals, acylphosphine oxides, such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, phenylglyoxyl esters, camphorquinone, alpha-aminoalkylphenones, alpha-, alpha-dialkoxyacetophenones, 1-[4-(phenylthio)phenyl]octane-1,2-dione 2-(O-benzoyloxime), and alpha-hydroxyalkylphenones.

[0092] The photopolymer composition may contain 0.1 to 10.0 parts by weight of the initiator, based on 100 parts by weight of the polymer matrix component. Specifically, the lower limit of the initiator content may be, for example, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, or 0.9 parts by weight or more, and the upper limit may be, for example, 5.0 parts by weight or less. Satisfying this range is advantageous for ensuring optical recording properties and high-temperature / high-humidity durability.

[0093] The photopolymer composition may further include a fluorine-based compound, which is a non-reactive compound and can be used as a plasticizer.

[0094] Specifically, the fluorine-based compound may contain 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.

[0095] The photopolymer composition may further include a fluorine-based compound represented by the following Formula 3:

[0096] [ka]

[0097] In the above Chemical Formula 3, R 11 and R 12 are each independently a difluoromethylene group, R 13 and R 16 are each independently a methylene group, R 14 and R 15 are each independently a difluoromethylene group, k is an integer from 1 to 10, R 17 and R 18 are each independently a linear or branched alkyl group having 1 to 10 carbon atoms or a functional group of the above chemical formula 4,

[0098] [ka]

[0099] In the above Chemical Formula 4, R 21 , R 22 and R 23 are each independently a linear or branched alkylene group having 1 to 10 carbon atoms, R 24 is a linear or branched alkyl group having 1 to 10 carbon atoms, l is an integer from 1 to 30.

[0100] More specifically, R in Formula 3 11 and R 12 are each independently a difluoromethylene group, and R 13 and R 16 are each independently a methylene group, and R14 and R 15 are each independently a difluoromethylene group, and R 17 and R 18 are each independently a 2-methoxyethoxymethoxy group, and k is an integer of 2.

[0101] The fluorine-based compound may have a lower refractive index than the photoreactive monomer, which can reduce the refractive index of the polymer matrix and increase the refractive index modulation.

[0102] The refractive index of the fluorine-based compound may be as low as 1.45 or less. Specifically, the upper limit of the refractive index of the fluorine-based compound may be, for example, 1.44 or less, 1.43 or less, 1.42 or less, 1.41 or less, 1.40 or less, 1.40 or less, 1.39 or less, 1.38 or less, or 1.37 or less, and the lower limit of the refractive index may be, for example, 1.30 or more, 1.31 or more, 1.32 or more, 1.33 or more, 1.34 or more, or 1.35 or more. By using a fluorine-based compound having a refractive index lower than that of the photoreactive monomer, the refractive index of the polymer matrix can be lowered and the refractive index modulation with the photoreactive monomer can be increased.

[0103] The fluorine-based compound may be included in an amount of 20 to 200 parts by weight based on 100 parts by weight of the polymer matrix or its precursor. Specifically, the lower limit of the content of the fluorine-based compound may be, for example, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, or 40 parts by weight or more, and the upper limit may be, for example, 200 parts by weight or less, 190 parts by weight or less, or 180 parts by weight or less. Satisfying this range is advantageous for ensuring excellent optical recording properties. If the content of the fluorine-based compound is less than this range, the refractive index modulation value after recording may be low due to a lack of low-refractive-index components. On the other hand, if the content of the fluorine-based compound exceeds this range, compatibility issues between the components contained in the coating layer may cause haze or problems such as some of the fluorine-based compound eluting onto the surface of the coating layer.

[0104] 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, 550 or more, or 600 or more, and the upper limit may be, for example, 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, or 500 or less. In consideration of refractive index modulation, compatibility with other components, and elution issues of the fluorine-based compound, it is preferable that the weight-average molecular weight be within the above range. Here, the weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene measured by the GPC method described above.

[0105] The photopolymer composition may further include one or more selected from the group consisting of a dye, a catalyst, an antifoaming agent, and a plasticizer.

[0106] Specifically, the photopolymer composition may further include a photosensitive dye. The photosensitive dye functions as a sensitizing dye that sensitizes the photoinitiator. More specifically, the photosensitive dye may also function as an initiator that initiates polymerization of the monomer and crosslinking monomer when stimulated by light irradiated onto the photopolymer composition. The photopolymer composition may include 0.01 wt % to 30 wt %, or 0.05 wt % to 20 wt % of the photosensitive dye.

[0107] The photosensitive dye is not particularly limited, and various commonly known compounds can be used. Specific examples of the photosensitive dye include sulfonium derivatives of ceramidonin, new methylene blue, thioerythrosin etriethylammonium, 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 Astrazon orange G. Examples of suitable dyes include: orange G, darrow red, pyronin Y, basic red 29, pyrylium iodide, safranin O, cyanine, methylene blue, azure A, or a combination of two or more thereof.

[0108] The photopolymer composition may contain a commonly known catalyst to promote polymerization of the polymer matrix or the photoreactive monomer. Examples of such catalysts include platinum-based catalysts such as Karstedt catalysts, rhodium-based catalysts, iridium-based catalysts, rhenium-based catalysts, molybdenum-based catalysts, iron-based catalysts, and nickel-based catalysts, as well as alkali metal and alkaline earth metal catalysts. Examples of non-metal catalysts include Lewis acids and carbene-based catalysts.

[0109] The photopolymer composition may further include other additives.

[0110] Examples of the other additives include antifoaming agents and phosphate-based plasticizers. Examples of the antifoaming agent include silicon-based reactive additives, such as Tego Rad 2500. Examples of the plasticizer include phosphate compounds such as tributyl phosphate. The plasticizer can be added together with the fluorine-based compound in a weight ratio of 1:5 to 5:1. The plasticizer may have a refractive index of less than 1.5 and a molecular weight of 700 or less.

[0111] The photopolymer composition may further comprise an organic solvent, non-limiting examples of which include ketones, alcohols, acetates, and ethers, or a mixture of two or more thereof.

[0112] Specific examples of such organic solvents include ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and isobutyl ketone; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, and t-butanol; acetates such as ethyl acetate, i-propyl acetate, and polyethylene glycol monomethyl ether acetate; ethers such as tetrahydrofuran and propylene glycol monomethyl ether; and mixtures of two or more of these.

[0113] The organic solvent can be added when mixing the components of the photopolymer composition, or the components can be dispersed or mixed in the organic solvent and added to the photopolymer composition. If the organic solvent content in the photopolymer composition is too low, the flowability of the photopolymer composition can be reduced, resulting in defects such as stripes in the final film. Furthermore, if the organic solvent is added in excess, the solids content can be reduced, preventing sufficient coating and film formation, resulting in reduced film physical properties and surface characteristics, and defects during drying and curing. Therefore, the photopolymer composition can contain an organic solvent such that the total solids concentration of the components contained therein is 1 wt% to 70 wt%, or 2 wt% to 50 wt%.

[0114] Specifically, the photopolymer composition may contain a solvent such that the solids concentration of all components contained in the composition is 1 to 70 wt%. Specifically, the solvent may be contained such that the solids concentration of all components contained in the composition is 2 wt% or more, 5 wt% or more, 10 wt% or more, or 20 wt% or more, and 65 wt% or less, 60 wt% or less, 55 wt% or less, or 50 wt% or less. If the solvent content in the composition is too low, the flowability of the composition may be reduced, resulting in defects such as streaks in the final film. Furthermore, if excessive solvent is added, the solids content may be low, which may result in insufficient coating and film formation, degrading the physical properties and surface characteristics of the photopolymer film and causing defects during the drying and curing processes.

[0115] The photopolymer composition can be used in holographic recording applications.

[0116] Meanwhile, according to another embodiment of the present invention, there is provided a photopolymer film comprising: a substrate film; and a coating layer comprising the photopolymer composition.

[0117] The coating layer may include an erosion layer and a recording layer.

[0118] As described above, the photopolymer film according to the embodiment may further include a corrosion layer between the substrate film and the recording layer. For example, the corrosion layer and the recording layer may be sequentially formed on the substrate film. The corrosion layer and the recording layer may be collectively referred to as a coating layer. The coating layer may also be a photopolymer layer formed from a photopolymer composition.

[0119] The composition of the photopolymer composition used in the coating solution for manufacturing the photopolymer film can be adjusted to form an erosion layer on the substrate film. For example, the photopolymer composition can include a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, and a solvent, so that the recording layer can include a polymer matrix containing a siloxane-based polymer and a photoreactive monomer.

[0120] Furthermore, when using the photopolymer composition of the present invention, the thickness ratio of the erosion layer in the coating layer of the photopolymer film can be adjusted to 10% to 50% by adjusting the content of the monofunctional monomer contained in the recording monomer, thereby preventing deformation and achieving excellent durability without being affected by high temperature / high humidity external environments. Therefore, the holographic recording medium can achieve a recording efficiency of 90% or more, excellent heat resistance, humidity resistance, haze resistance, adhesive strength, and cohesive strength. In particular, the excellent heat, humidity, and heat resistance properties under high temperature and humidity conditions result in excellent long-term storage stability and optimized recording characteristics of the holographic recording medium.

[0121] Furthermore, the use of the hologram medium makes it possible to provide a hologram that has a thinner thickness yet more effectively achieves significantly improved refractive index modulation values ​​and high diffraction efficiency compared to previously known holograms.

[0122] The coating layer of the photopolymer film includes a crosslinked matrix. For example, the photopolymer film may include or be formed from a composition including at least a crosslinked matrix or a precursor thereof. In a specific example of the present application, the coating layer may include or be formed from a composition including a crosslinked matrix or a precursor thereof, a photoreactive monomer, and a photoinitiator.

[0123] In the photopolymer film, the coating layer includes an erosion layer and a recording layer, and the thickness ratio of the erosion layer to the coating layer satisfies the condition of the following formula 1.

[0124] [Formula 1] 10%≦(thickness of the eroded layer of the photopolymer film coating layer / total thickness of the photopolymer film coating layer)×100≦50%

[0125] If the thickness ratio of the erosion layer is less than 10%, there are problems with poor heat resistance, humidity and heat resistance reliability, and poor adhesive strength and adhesion, while if it is more than 50%, the thickness of the recording layer that is actually recorded becomes too thin, resulting in poor recording efficiency.

[0126] The coating layer (i.e., photopolymer layer) of the photopolymer film may have a thickness of 5.0 to 40.0 μm as a holographic recording layer. Specifically, the thickness of the coating layer may be, for example, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, or 15 μm or more. The upper limit of the thickness may be, for example, 35 μm or less or 30 μm or less, specifically 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. The holographic recording medium of the present invention exhibits excellent refractive index modulation, diffraction efficiency, and driving reliability even when it has a small thickness within the above-mentioned range.

[0127] The photopolymer film is prepared as follows.

[0128] When the photopolymer composition is applied to the substrate film, the photoreactive monomer and solvent may dissolve and penetrate at least a portion of the substrate film. Then, when a drying process to form a coating layer is performed, the polymer matrix including the siloxane-based polymer and the photoreactive monomer may harden or crosslink to form an erosion layer. Furthermore, the photoreactive monomer that has penetrated the substrate film may physically or chemically bond to the substrate film.

[0129] Therefore, the erosion layer may contain a photoreactive monomer, and the erosion layer may be physically or chemically bonded to the base film. For example, the physical bond between the erosion layer and the base film is achieved by the photoreactive monomer contained in the erosion layer being physically bonded to the base film.

[0130] Meanwhile, a recording layer may be formed on the erosion layer, and the recording layer may include a polymer matrix including a siloxane-based polymer and a photoreactive monomer.

[0131] As described above, the formation of an inter-layer erosion on the substrate film can significantly improve adhesion between the optical film and the recording layer, minimize a decrease in recording efficiency of the photopolymer film, and exhibit excellent mechanical properties such as heat resistance and humidity / heat resistance reliability. The presence or absence of the inter-layer erosion can be confirmed by photothermal infrared spectroscopy as described above, and the thickness of the inter-layer erosion can be analyzed by scanning electron microscopy.

[0132] The thickness of the erosion layer may be 1.0 μm or more, 2.0 μm or more, or 2.5 μm or more, or 6.0 μm or less, 5.5 μm or less, 5.0 μm or less, or 4.5 μm or less. If the thickness of the erosion layer is too thin, the adhesion between the substrate film and the recording layer will be reduced, and the heat resistance and moist heat resistance reliability will be reduced. If the thickness of the erosion layer is too thick, the thickness of the recording layer that is actually recorded will be too thin, and the recording efficiency will be low.

[0133] The recording layer may have a thickness of 3.0 μm or more, 3.5 μm or more, or 4.0 μm or more, or 8.0 μm or less, 7.0 μm or less, 6.8 μm or less, or 6.7 μm or less. If the recording layer is too thin, low recording efficiency will be exhibited, and if the recording layer is too thick, the thickness of the erosion layer will be thin, which may result in poor adhesion between the substrate film and the recording layer.

[0134] The coating layer may have a thickness of 5.0 μm or more, 5.5 μm or more, or 6.0 μm or more, and may have a thickness of 20.0 μm or less, 15.0 μm or less, or 10.0 μm or less.

[0135] The substrate film included in the photopolymer film according to the embodiment is not particularly limited in type, as long as it is capable of forming the corrosion layer, and any substrate film known in the related art can be used. For example, cellulose ester-based substrate films, polyester-based substrate films, poly(meth)acrylate-based substrate films, polycarbonate-based substrate films, cycloolefin (COP)-based substrate films, glass, acrylic-based substrate films, etc. can be used. Specifically, substrates such as PET (polyethylene terephthalate), TAC (triacetyl cellulose), PC (polycarbonate), COP (cycloolefin polymer), and polymethyl methacrylate (PMMA) can be used.

[0136] The thickness of the substrate film may be 20 μm or more, 30 μm or more, or 40 μm or more, or may be 500 μm or less, 300 μm or less, 100 μm or less, 80 μm or less, or 60 μm or less. By satisfying the above-mentioned thickness, the substrate film can exhibit properties such as excellent mechanical properties, water resistance, and low moisture permeability.

[0137] The photopolymer film can be used for holographic recording applications.

[0138] Meanwhile, according to still another embodiment of the present invention, there is provided a holographic recording medium including the photopolymer film.

[0139] As described above, the photopolymer film has improved heat resistance, humidity resistance, haze resistance, adhesion, and adhesion properties, thereby preventing deformation of the photopolymer film due to high temperature / humidity external environments and optimizing recording efficiency. Therefore, a holographic recording medium including the same also has excellent heat resistance, humidity resistance, and heat resistance, optimizing recording efficiency.

[0140] The photopolymer film can be fabricated into holograms for optical applications in the entire visible and near-ultraviolet range (300-800 nm) through a specific exposure process.

[0141] As a method for recording a visual hologram in the holographic recording medium including the photopolymer film, any commonly known method can be used without any particular limitation.

[0142] For example, a visual hologram can be recorded by selectively polymerizing a photoreactive monomer contained in the photopolymer film using a coherent laser.

[0143] The holographic recording medium of the another embodiment can achieve a refractive index modulation value (Δn) of 0.020 or more, 0.021 or more, 0.022 or more, 0.023 or more, 0.024 or more, 0.025 or more, 0.026 or more, 0.027 or more, 0.028 or more, 0.029 or more, or 0.030 or more, even when the photopolymer layer is as thin as 5 to 30 μm. The upper limit of the refractive index modulation value is not particularly limited, but may be, for example, 0.035 or less.

[0144] In addition, the photopolymer film and the holographic recording medium including the same can have a diffraction efficiency of 90% or more, a heat resistance and a humidity resistance reliability of -10 nm to 10 nm, a haze of 1.5% or less, an adhesive strength (180° Peel test) of 1000 g / 25 mm or more, and an adhesive strength of 4B or more.

[0145] Specifically, the photopolymer film of the other embodiment and the holographic recording medium including the same can have a diffraction efficiency of 90% or more. Specifically, the photopolymer film and the holographic recording medium including the same can achieve a diffraction efficiency of 90% or more, 91% or more, 92% or more, or 94% or more at a thickness of 5 μm to 30 μm. Thus, the photopolymer film of the other embodiment and the holographic recording medium including the same can achieve excellent diffraction efficiency even when including a thin photopolymer layer.

[0146] Furthermore, the photopolymer film and the holographic recording medium including the same may have an absorption wavelength modulation value (Δλ) of about -10 nm or more and 10 nm or less when heat resistance and moist heat resistance reliability are measured under high temperature and high humidity conditions of 65°C, RH 90%, and 72 hours by adjusting the content ratio of the monofunctional monomer among the recording monomers within a specific range. Specifically, the heat resistance reliability may be about -10 nm or more, -9 nm or more, or -8 nm or more, and about 10 nm or less, 8 nm or less, or 6 nm or less. Furthermore, the moist heat resistance reliability may be about -10 nm or more, -8 nm or more, -6 nm or more, or -4 nm or more, and about 10 nm or less, 8 nm or less, 6 nm or less, 4 nm or less, 3 nm or less, or 2 nm or less.

[0147] In addition, the photopolymer film and the holographic recording medium including the same may have a haze of 1.5% or less, an adhesive strength (180° Peel test) of 1000 g / 25 mm or more, and an adhesive strength of 4B or more.

[0148] The diffraction efficiency, heat resistance and moist heat resistance reliability, haze, adhesive strength and adhesion can be measured by the methods described in the test examples below.

[0149] The holographic recording medium of the other embodiment may be one in which a reflection hologram or a transmission hologram is recorded, although the invention is not limited thereto.

[0150] The application of the holographic recording medium according to the other embodiment is not particularly limited. As a non-limiting example, the holographic recording medium may be used in applications that are likely to be exposed to high temperature / high humidity environments, specifically, smart devices such as mobile devices, components of wearable displays, or automotive components (e.g., head-up displays).

[0151] Meanwhile, according to yet another embodiment of the present invention, there is provided a holographic recording method including the step of selectively polymerizing a photoreactive monomer contained in the photopolymer composition using a coherent laser.

[0152] As described above, a medium without a visual hologram recorded thereon can be produced through the process of mixing and curing the photopolymer composition, and a visual hologram can be recorded on the medium through a predetermined exposure process.

[0153] A visual hologram can be recorded in the medium provided by the process of mixing and curing the photopolymer composition using known equipment and methods under commonly known conditions.

[0154] For example, the method for manufacturing the holographic recording medium may include the steps of: applying a photopolymer composition to a substrate to form a photopolymer film; and irradiating a predetermined region of the photopolymer film with a coherent laser to selectively polymerize the photoreactive monomer and monofunctional monomer contained in the photopolymer film, thereby recording optical information.

[0155] The photopolymer composition may be the photopolymer composition of one embodiment described above, and as the photopolymer composition has been described in detail above, a detailed description thereof will be omitted here.

[0156] In the step of forming the photopolymer film, a photopolymer composition having the above-described structure can be first prepared. When preparing the photopolymer composition, a commonly known mixer, stirrer, or mixer can be used to mix the components without any particular limitation. This mixing process can be carried out at a temperature ranging from 0°C to 100°C, from 10°C to 80°C, or from 20°C to 60°C.

[0157] In the step of forming the photopolymer film, the prepared photopolymer composition may be applied to a substrate to form a coating film formed from the photopolymer composition. The coating film may be dried naturally at room temperature or at a temperature ranging from 30 to 80°C. Through this process, a hydrosilylation reaction may be induced between the remaining unreacted hydroxyl groups of the (meth)acrylic polyol and the silane functional groups of the siloxane polymer.

[0158] Meanwhile, according to still another embodiment of the present invention, an optical element including a holographic recording medium can be provided.

[0159] Specific examples of the optical element include an optical lens, a mirror, a deflection mirror, a filter, a diffusion screen, a diffraction element, a light guide, a wave guide, a holographic optical element having the function of a projection screen and / or a mask, a medium and a light diffusion plate of an optical memory system, an optical wavelength splitter, a reflective or transmissive color filter, etc.

[0160] An example of an optical element including the holographic recording medium is a holographic display device.

[0161] The hologram display device includes a light source unit, an input unit, an optical system, and a display unit. The light source unit emits a laser beam used to provide, record, and reproduce 3D image information of an object in the input unit and display unit. The input unit pre-inputs 3D image information of the object to be recorded in the display unit. For example, the input unit can input 3D information of the object, such as spatial light intensity and phase, to an electrically addressed liquid crystal SLM (SLM), using an input beam. The optical system can be composed of mirrors, polarizers, beam splitters, beam shutters, lenses, etc., and can split the laser beam emitted from the light source unit into an input beam to be sent to the input unit, and a recording beam, reference beam, erase beam, read beam, etc. to be sent to the display unit.

[0162] The display unit receives 3D image information of an object from the input unit, records it on a hologram plate consisting of an optically addressed SLM (SLM), and reproduces the 3D image of the object. 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 where the 3D image is input and a position where it is reproduced. [Effects of the Invention]

[0163] The photopolymer composition according to one embodiment of the invention not only has excellent recording efficiency, but also can more easily and efficiently provide a photopolymer layer that can achieve higher refractive index modulation values ​​even in a thin thickness range and exhibit excellent durability, reliability, haze, adhesion and adhesion properties.

[0164] Therefore, according to the present invention, it is possible to provide a photopolymer film that achieves a higher refractive index modulation value even in a thin thickness range, is prevented from deformation due to the external environment even in high temperature and high humidity environments, and has excellent heat resistance, humidity and heat resistance reliability, haze, adhesion and bonding properties, as well as a hologram recording medium, optical element, and holographic recording method including the same. [Brief explanation of the drawings]

[0165] [Figure 1] 1 is a schematic diagram of a recording equipment setup for recording holograms according to one embodiment. [Figure 2] 10 illustrates a spectrum for measuring the diffraction efficiency of a holographic recording medium according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0166] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, but these are presented as examples of the present invention and do not limit the scope of the invention in any way.

[0167] [Manufacturing example] Production Example 1: Production of (meth)acrylic polyol A 2L jacketed reactor was charged with 132g of butyl acrylate, 420g of ethyl acrylate, and 48g of hydroxybutyl acrylate, and diluted with 1200g of ethyl acetate. The reaction temperature was set to 60-70°C, and the mixture was stirred for 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) was then added, and the mixture was stirred for another 30 minutes. 0.24g of the polymerization initiator AIBN was then added, and the mixture was polymerized at the reaction temperature for at least 4 hours, maintaining the temperature until the residual acrylate content was less than 1%. This produced a (meth)acrylate copolymer with hydroxyl groups located in branched chains (weight average molecular weight approximately 300,000, OH equivalent approximately 1802g / equivalent).

[0168] Production Example 2: Production of Fluorine-Based Compounds A 1000 mL flask was charged with 20.51 g of 2,2'-{oxybis[(1,1,2,2-tetrafluoroethane-2,1-diyl)oxy]}bis(2,2-difluoroethan-1-ol) and dissolved in 500 g of tetrahydrofuran. 4.40 g of sodium hydride (60% dispersion in mineral oil) was carefully added over several times while stirring at 0°C. After stirring at 0°C for 20 minutes, 12.50 mL of 2-methoxyethoxymethyl chloride was slowly added dropwise. After confirming that all reactants had been consumed by 1H NMR, work-up using dichloromethane yielded 29g of a liquid product with a purity of over 95% in 98% yield. The weight-average molecular weight of the produced fluorine-based compound was 586, and the refractive index measured with an Abbe refractometer was 1.361.

[0169] [Examples and Comparative Examples: Production of Photopolymer Compositions, Photopolymer Films, and Holographic Media] Example 1: Production of photopolymer composition, photopolymer film, and holographic recording medium

[0170] (1) Preparation of photopolymer composition (prepared under darkroom conditions) A mixture was prepared by first mixing 0.6 g of a siloxane polymer, trimethylsilyl-terminated poly(methylhydrosiloxane) (Sigma-Aldrich, number average molecular weight: approximately 390), and 33.3 g of the (meth)acrylic polyol prepared in Preparation Example 1 (SiH / OH molar ratio = 1.0).

[0171] Then, 14.5 g of the fluorine-based compound prepared in Preparation Example 2, 0.1 g of photosensitive dye HNu-640 (manufactured by Spectra), 0.3 g of silicon-based reactive additive (Tego Rad 2500), and methyl ethyl ketone (MEK) as a solvent were added to the mixture, and the mixture was mixed in the dark and stirred for about 10 minutes using a Paste mixer.

[0172] Then, for matrix crosslinking, a Karstedt (Pt-based) catalyst (0.01 g) was added and crosslinking was carried out at room temperature for 30 minutes or more. 22.6 g of a high refractive index photoreactive monomer HR 6042 (Miwon, refractive index 1.60), a monofunctional monomer low molecular weight acrylate, a bifunctional monomer, and 3.0 g of a photoinitiator Borate V were added to the reaction solution (transparent coating solution), and mixed at room temperature for 5 minutes or more to produce a photopolymer composition with a solid content of 25 wt%.

[0173] At this time, the ratio of the monofunctional monomer is as shown in Table 1. Based on 100 parts by weight of the photoreactive monomer, the ratio was adjusted by further adding the monofunctional monomer OPPE (A2-Phenylphenoxyethylacrylate) so that the content of the monofunctional monomer became 43 parts by weight.

[0174] (2) Manufacturing of photopolymer films and holographic recording media The photopolymer composition was coated onto a 40 μm thick TAC substrate to a thickness of 8 μm using a Meyer bar and dried at 60°C for 10 minutes to produce a photopolymer film (thickness: 15 μm).The sample was then left in a dark room under constant temperature and humidity conditions of approximately 25°C and 50% RH for 24 hours or more.

[0175] The photopolymer film thus prepared was laminated onto a 0.70 mm thick glass slide so that the photopolymer layer was in contact with it and fixed so that the laser passed through the glass surface first during recording. Lasers of 660 nm and 532 nm were used for recording, with a reference beam to object beam ratio of 1. The recording setup was as shown in Figure 1, with recording performed using a reflective slanted method (reference beam = 30°, object beam = 40°).

[0176] The hologram recording medium, on which a reflective diffraction grating was recorded using a laser, was attached to glass and placed in a UV irradiator (Dymax model 2000 flood) at 105 mW / cm 2 The photobleaching process was carried out by irradiating the sample with UVA at an intensity of 1000 uV for about 1 minute to remove the color of the photosensitive dye and complete the reaction of the photoreactive monomer.

[0177] [Examples 2 to 4 and Comparative Examples 1 to 4: Production of photopolymer compositions, photopolymer films, and holographic recording media] Photopolymer compositions and photopolymer films and holographic recording media were prepared using the same method as in Example 1, except that the composition and content of the monofunctional or difunctional monomers among the recording monomers were as shown in Table 1 below.

[0178] [Table 1]

[0179] [Experimental example: Holographic recording] The physical properties of the examples and comparative examples were measured by the following methods, and the results are shown in Table 2.

[0180] (1) Recording method The hologram recording method was performed using a hologram recording device as shown in Figure 1.

[0181] Figure 1 is a schematic diagram of a recording device setup for hologram recording according to one embodiment. Specifically, Figure 1 shows a process in which a laser of a predetermined wavelength is emitted from a light source (laser) 1, and then passes through mirror 1 (mirror 1) 2, mirror 2 (mirror 2) 3, objective lens (object) 4, pinhole 5, collimation lens 6, and iris 7, before being irradiated onto photopolymer 8, a hologram recording medium, located on mirror 3 (mirror 3) 9.

[0182] More specifically, when a film containing the prepared photopolymer layer is laminated on a mirror and then irradiated with a laser, a notch filter hologram with periodic refractive index modulation in the thickness direction is recorded due to interference between incident light (L) and light (L') reflected by the mirror. In this example, the notch filter hologram was recorded with an incident angle of 0°. Notch filters and Bragg reflectors are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indices are repeatedly stacked at a constant thickness.

[0183] The hologram recording medium, on which a reflective diffraction grating was recorded using a laser, was attached to the glass and placed in a UV irradiator (Dymax model 2000 flood) at 105 mW / cm 2The photobleaching process was carried out by irradiating the sample with UVA at an intensity of 1000 uV for about 1 minute to remove the color of the photosensitive dye and complete the reaction of the photoreactive monomer.

[0184] (2) Percentage of eroded layer in photopolymer film (%) The thickness of the eroded layer in the photopolymer film was measured using a scanning electron microscope (SEM, 9000x magnification), and then the thickness ratio of the eroded layer to the entire photopolymer film was calculated according to the following equation 1-1.

[0185] [Formula 1-1] Thickness ratio of the eroded layer in the photopolymer film (%) = (thickness of the eroded layer of the photopolymer film coating layer / total thickness of the photopolymer film coating layer) x 100

[0186] (3) Diffractive Efficiency (DE) (unit: %) (recording efficiency) For a sample of a holographic recording medium using the photopolymer composition, the reflection spectrum of the recorded photopolymer was measured using a UV-VIS spectrophotometer (Shimadzu Corporation, SolidSpec-3700), and the diffraction efficiency (i.e., recording efficiency) was measured by confirming the reflection peak. Figure 2 shows the spectrum used to measure the diffraction efficiency of a holographic recording medium of one embodiment.

[0187] That is, the transmittance was measured in the wavelength region of 500-780 nm, which includes the recording wavelength, and the diffraction efficiency was calculated using the following formula 2.

[0188] [Formula 2] DE(%)=(T0-T m ) / T0×100

[0189] In the formula 2, T0 is the average transmittance at the recording wavelength where the recording peak of the holographic recording medium sample in Figure 2 does not appear, T m is the minimum transmittance of the photopolymer film at the recording peak of the sample holographic recording medium of FIG.

[0190] (3) Post-recording reliability For reliability evaluation, the photopolymer film was left with BPSA attached for 72 hours under heat-resistant and humid heat-resistant conditions (a dark room under constant temperature and humidity conditions of 65°C and 90 RH%).

[0191] Thereafter, the spectrum was measured to confirm the shift of the reflection peak (Δλ), and the reliability of heat resistance and humidity and heat resistance was evaluated. That is, the transmittance of the sample of the holographic recording medium according to the wavelength was measured using the spectrophotometer, and the peak value (λ) at which the transmittance reached its maximum value was determined. max ) and then measured λ before leaving it for 72 hours. max The reliability was evaluated by calculating the difference (Δλ) between the

[0192] (4) Hayes The haze of the recorded portion of the photopolymer was measured in accordance with JIS K7136: 2000 using a HAZEMETER (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.) with the measurement light incident on the substrate side of the holographic recording medium.

[0193] (5) Adhesion evaluation A sample of the holographic recording medium was prepared with a width of 25 mm and a length of 80 mm, and attached to the OCA adhesive surface of a 100 mm x 100 mm glass plate with an OCA film. A 180° peel test was performed using a Texture Analyzer device, and the load applied to the 25 mm width was measured to evaluate the adhesiveness.

[0194] (6) Adhesion evaluation A cross-cut test was carried out, and a checkerboard pattern of 10 squares horizontally and 10 squares vertically was drawn on the photopolymer film using a blade, and the film was peeled off twice using tape. The state of the recording layer being separated from the substrate surface and the grooves and peeling were evaluated to evaluate adhesion.

[0195] [Table 2]

[0196] Referring to Table 2, it was confirmed that the holographic recording medium (photopolymer coating film) manufactured from the photopolymer composition of the example according to one embodiment of the present invention has a ratio of the erosion layer of the photopolymer film of 10% to 50% by adjusting the ratio of the monofunctional monomer (low molecular weight acrylate) among the recording monomers within a specific range. As a result, it was confirmed that the recording efficiency (diffraction efficiency) is 90% or more, and the heat resistance, humidity and heat resistance reliability, haze, adhesiveness and adhesion are all superior to those of the comparative example.

[0197] In contrast, the photopolymer coating films provided by the compositions of the comparative examples showed relatively low diffraction efficiency and poor heat resistance and humidity / heat resistance reliability compared to the examples because only a bifunctional monomer was used as the recording monomer or the content of a monofunctional monomer was too low or too high. Furthermore, the comparative examples were found to have poor results in terms of haze, adhesive strength, and adhesion strength compared to the examples.

[0198] At this time, the higher the proportion of monofunctional monomers (low molecular weight acrylates) in the recording monomers, the easier it is for the monofunctional monomers to invade the substrate layer, resulting in a thicker erosion layer of the photopolymer. However, if the content is too high, problems may arise such as a decrease in recording efficiency and a decrease in the reliability of heat resistance and humidity and heat resistance. Therefore, it is important to appropriately adjust the range of the content of monofunctional monomers in the recording monomers.

[0199] That is, in Comparative Example 1, only a bifunctional monomer was included in the recording monomer, and the recording efficiency was very low, and the overall physical properties, including heat resistance, humidity and heat resistance reliability, haze, adhesive strength, and adhesion, were all poor. Also, in Comparative Example 2, the content of the monofunctional monomer was 30 parts by weight, which was lower than that of the Examples, and it was confirmed that all physical properties were also very poor. Furthermore, when the content of the monofunctional monomer was excessively high, at 60 parts by weight, as in Comparative Example 3, it was found that the recording efficiency and heat resistance, humidity and heat resistance reliability were poor.

[0200] Although Comparative Example 4 had a corrosion layer ratio of 10% to 50%, it used a monofunctional monomer different from that of the present invention, resulting in a very low diffraction efficiency of 47.3% and poorer overall physical properties such as heat resistance, humidity and heat resistance reliability, and haze compared to the Examples. Comparative Example 5 used the same type of monofunctional monomer as the present invention and had a corrosion layer ratio of 10% to 50%, but used triethylene glycol diacrylate as the bifunctional monomer, resulting in a diffraction efficiency of 24.2%, which was even lower than Comparative Example 4, and poorer heat resistance and humidity and heat resistance reliability.

Claims

1. The present invention comprises 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 including a monofunctional monomer and a polyfunctional monomer; and a photoinitiator; The photopolymer composition for forming a holographic recording medium comprises 42 to 55 parts by weight of a monofunctional monomer based on 100 parts by weight of the photoreactive monomer.

2. 2. The photopolymer composition for forming a holographic recording medium according to claim 1, wherein the monofunctional monomer is a monofunctional (meth)acrylate monomer.

3. 2. The photopolymer composition for forming a holographic recording medium according to claim 1, wherein the monofunctional monomer comprises one or more monofunctional (meth)acrylate monomers selected from the group consisting of phenoxybenzyl (meth)acrylate, o-phenylphenol ethylene oxide (meth)acrylate, benzyl (meth)acrylate, 2-(phenylthio)ethyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

4. 2. The photopolymer composition for forming a holographic recording medium according to claim 1, wherein the siloxane-based polymer is PMHS (polymethylhydrosiloxane), and the (meth)acrylic polyol is a polyalkyl(meth)acrylate having a hydroxy group.

5. 2. The photopolymer composition of claim 1, wherein the siloxane-based polymer comprises a repeating unit represented by the following Chemical Formula 1 and an end group represented by the following Chemical Formula 2: 【Chemical 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 at least one repeating unit of the repeating unit represented by Chemical Formula 1 and one of the terminal groups of the terminal group represented by Chemical Formula 2 １ , R ２ and R １１ ~R １３ At least one of these is hydrogen.

6. 2. The photopolymer composition according to claim 1, wherein the (meth)acrylic polyol has a structure in which two or more hydroxy groups are bonded to a (meth)acrylate polymer main chain or side chain, and has a weight average molecular weight of 150,000 to 1,000,000.

7. The photopolymer composition of claim 1 , wherein the photoreactive monomer comprises a multifunctional monomer having a refractive index of 1.5 or greater.

8. 8. The photopolymer composition of claim 7, wherein the polyfunctional monomer comprises at least one selected from the group consisting of bisphenol A-modified diacrylates, fluorene acrylates, bisphenol fluorene epoxy acrylates, and halogenated epoxy acrylate compounds.

9. 2. The photopolymer composition of claim 1, wherein the photoreactive monomer is contained in an amount of 70 to 130 parts by weight based on 100 parts by weight of the polymer matrix or its precursor.

10. The photopolymer composition of claim 1, further comprising a fluorine-based compound having a repeating unit represented by the following chemical formula 3: 【Chemistry 3】 In the above Chemical Formula 3, R １１ and R １２ are each independently a difluoromethylene group, R １３ and R １６ are each independently a methylene group, R １４ and R １５ are each independently a difluoromethylene group, k is an integer from 1 to 10, R １７ and R １８ are each independently a linear or branched alkyl group having 1 to 10 carbon atoms or a functional group of the above formula 4, 【Chemistry 4】 In the above Chemical Formula 4, R ２１ , R ２２ and R ２３ are each independently a linear or branched alkylene group having 1 to 10 carbon atoms, R ２４ is a linear or branched alkyl group having 1 to 10 carbon atoms, l is an integer from 1 to 30.

11. A photopolymer film comprising: a substrate film; and a coating layer comprising the photopolymer composition of claim 1.

12. the coating layer includes an erosion layer and a recording layer; 12. The photopolymer film of claim 11, wherein the thickness ratio of the erosion layer to the coating layer satisfies the following formula 1: [Formula 1] 10%≦(thickness of the eroded layer in the coating layer of the photopolymer film / total thickness of the coating layer of the photopolymer film)×100≦50%

13. A holographic recording medium comprising the photopolymer film of claim 11.

14. An optical element comprising the holographic recording medium according to claim 13.

15. A holographic recording method comprising the step of selectively polymerizing a photoreactive monomer and a monofunctional monomer contained in the photopolymer composition of claim 1 with a coherent laser.

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