Photopolymer film, composition for forming photopolymer film, holographic recording medium, and optical element

Abstract

The present disclosure relates to a photopolymer film, a composition for forming such a photopolymer film, and a holographic recording medium and an optical element comprising the same, the photopolymer film comprising a base film and a recording layer, and has a predetermined maximum reduction rate of the band area in a map derived from the result of photo-thermal infrared (PTIR) spectroscopic analysis in the thickness direction from one surface of the recording layer.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2022-0161773 filed on November 28, 2022, in the Korean Intellectual Property Office and Korean Patent Application No. 10-2022-0161774 filed on November 28, 2022, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety.

[0003] The present disclosure relates to a photopolymer film, a composition for forming the photopolymer film, a holographic recording medium including the photopolymer film, and an optical element. Background Art

[0004] The holographic recording medium records information by changing the refractive index of a holographic recording layer in the medium through an exposure process, reads the change in the refractive index in the medium thus recorded, and reproduces the information.

[0005] When photopolymers (photosensitive resins) are used, light interference patterns can be easily stored as holograms by photopolymerization of low molecular weight monomers. Therefore, photopolymers can be used in various fields, such as optical lenses, reflectors, deflection mirrors, filters, diffuser screens, diffraction elements, light guides, waveguides, holographic optical elements with projection screen and / or mask functions, light diffuser plates and media for optical storage systems, optical wavelength multiplexers, reflective and transmissive color filters, etc.

[0006] The photopolymer film can be produced by applying a composition comprising a low molecular weight monomer and a photoinitiator to a base film and then thermally curing the composition, and the photopolymer film produced by this method is composed of a base film and a recording layer on which recording is performed. The recording layer is irradiated with laser interference light to cause local photopolymerization of the monomer.

[0007] However, the photopolymer film produced by this method has poor adhesion between the base film and the recording layer, and thus reliability may be reduced due to the influence of the external environment. Therefore, a lot of research has been conducted to improve adhesion, but the resulting degree of improvement in physical properties is insufficient. Summary of the invention

[0008] Technical issues

[0009] An object of the present disclosure is to provide a photopolymer film having optimized recording efficiency while exhibiting excellent heat resistance and wet heat resistance reliability, and improved adhesion between a base film and a recording layer.

[0010] Another object of the present disclosure is to provide a composition for forming the photopolymer film.

[0011] Still another object of the present disclosure is to provide a holographic recording medium and an optical element including the photopolymer film.

[0012] Technical Solution

[0013] The present invention provides a photopolymer film including a base film and a recording layer, wherein a graph obtained from the results of photothermal infrared (PTIR) spectroscopy analysis in the thickness direction starting from a surface of the recording layer facing the base film satisfies the following formula 1, wherein the band area of ​​the carbonyl (C=O group) peak contained in the recording layer is plotted on the Y-axis, and the distance in the thickness direction starting from a surface of the recording layer facing the base film is plotted on the X-axis.

[0014] Also provided herein is a composition for forming a photopolymer film, comprising a coating solution, the coating solution comprising a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, and an etching solvent, wherein the content of the etching solvent is 25 wt % or more and 70 wt % or less relative to 100 wt % of the coating solution.

[0015] Also provided herein is a holographic recording medium including the photopolymer film.

[0016] Also provided herein is an optical element comprising the photopolymer film.

[0017] Now, a photopolymer film, a composition for forming the photopolymer film, a holographic recording medium and an optical element including the same according to specific embodiments of the present disclosure will be described in more detail.

[0018] The term "hologram" as used herein means a medium on which optical information is recorded via an exposure process in the entire visible light range and near ultraviolet range (e.g., 300 nm to 800 nm). Examples of holograms may include all visual holograms, such as on-axis (Gabor) holograms, off-axis holograms, full-aperture transfer holograms, white light transmission holograms ("rainbow holograms"), Denisyuk holograms, off-axis reflection holograms, edge-illuminated holograms, or holographic stereograms.

[0019] As used herein, (meth)acrylate means one or both of acrylate and methacrylate.

[0020] In addition, in this specification, weight average molecular weight (Mw) and number average molecular weight (Mn) refer to molecular weights (unit: Da (Dalton)) converted according to polystyrene measured by gel permeation chromatography (gel permeation chromatography, GPC). In the process of determining the weight average molecular weight according to polystyrene measured by GPC method, detectors such as commonly known analytical equipment and differential refractive index detectors and analytical columns can be used, and commonly used temperature, solvent and flow conditions can be used. Specific examples of measurement conditions may include a temperature of 30 ° C, a chloroform solvent and a flow rate of 1 mL / min. In a specific example of measurement conditions, a Waters PL-GPC220 instrument is used with a PLgel MIX-B column (300 mm in length) from Polymer Laboratories, an evaluation temperature of 160 ° C, 1,2,4-trichlorobenzene is used as a solvent, and a flow rate of 1 mL / min. The sample is prepared at a concentration of 10 mg / 10 mL and then supplied in an amount of 200 μL. The values ​​of Mw and Mn can be determined using calibration curves generated by polystyrene standards, respectively. Nine types of polystyrene standards having molecular weights of 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000 were used.

[0021] According to one embodiment of the present disclosure, a photopolymer film including a substrate film and a recording layer can be provided, wherein a graph obtained from the results of photothermal infrared (PTIR) spectroscopy analysis in the thickness direction starting from a surface of the recording layer facing the substrate film satisfies the following formula 1, wherein the band area of ​​the carbonyl (C=O group) peak contained in the recording layer is plotted on the Y-axis, and the distance in the thickness direction starting from a surface of the recording layer facing the substrate film is plotted on the X-axis.

[0022] [Formula 1]

[0023] 0.010μm -1 ≦Maximum reduction rate of band area ≦0.095μm -1

[0024] In formula 1,

[0025] The maximum reduction rate of the band area is the absolute value of the minimum value of the y value in the graph obtained by taking the first-order differentiation of the graph.

[0026] The present inventors have found that the following photopolymer film has excellent adhesion between a base film and a recording layer and exhibits excellent heat resistance and wet heat resistance reliability, and have completed the present disclosure: the photopolymer film includes a base film and a recording layer, wherein the maximum reduction rate of the band area according to Formula 1 is 0.010 μm -1 or larger, 0.020μm -1 or larger, 0.030μm -1 or larger, 0.040μm -1 or larger, 0.050μm -1 or larger, 0.060μm -1 or larger, or 0.062μm -1 or larger, and 0.095μm -1 or smaller, 0.090μm -1 or smaller, 0.085μm -1 or smaller, or 0.082μm -1 or smaller.

[0027] Photothermal infrared (PTIR) spectroscopy may be measured in the thickness direction of the recording layer based on one surface of the recording layer facing the base film. At this time, the measurement interval may be 0.3 μm to 5 μm, 0.5 μm to 2 μm, or 1 μm.

[0028] For example, when the measurement interval is 1 μm, one surface of the recording layer becomes a reference (0 μm), so that first, photothermal infrared spectroscopy analysis can be performed, second, photothermal infrared spectroscopy analysis can be performed for one surface of the recording layer at a position of 1 μm in the thickness direction, and third, photothermal infrared spectroscopy analysis can be performed for one surface of the recording layer at a position of 2 μm in the thickness direction. Thereafter, photothermal infrared spectroscopy analysis can be performed sequentially at 1 μm intervals in the thickness direction until one surface of the optical film facing the recording layer.

[0029] In the graph obtained by photothermal infrared spectroscopy, the X axis is the distance in the thickness direction from one surface of the recording layer facing the base film, and if the X value is 0 μm, it means one surface (one face) of the recording layer facing the optical film. In addition, the result value may appear in the graph according to the measurement interval. For example, when the measurement interval of the photothermal infrared spectroscopy is 1 μm, the result value may appear at 1 μm intervals along the X axis in the graph.

[0030] In addition, in the figure, the Y axis is the band area of ​​the carbonyl (C=O group) peak contained in the recording layer, and the carbonyl (C=O group) peak may appear at about 1720 cm -1 Up to 1725cm -1 Place.

[0031] For example, when the recording layer is subjected to photothermal infrared spectroscopy analysis in the thickness direction, the band area value of the peak of the carbonyl group contained in the recording layer can be displayed as the Y value. For example, when the photoreactive monomer contained in the recording layer contains an acrylate group, the band area of ​​the carbonyl group (C=O group) peak of the acrylate group can be displayed as the value of the Y axis. That is, the graph obtained from the result of the photothermal infrared spectroscopy analysis is a graph showing the band area value of the carbonyl group (C=O group) peak contained in the recording layer, and the band area value is the Y value corresponding to the X value (the distance in the thickness direction from one surface of the recording layer facing the base film).

[0032] on the other hand, Figure 2 A diagram schematically showing the shift of the carbonyl (C=O group) peak in the thickness direction as a result of photothermal infrared spectroscopy analysis starting from one surface of the recording layer facing the base film, it can be confirmed that the shift from the carbonyl peak contained in the red recording layer to the carbonyl peak contained in the blue base film occurs. In addition, it can be confirmed that an erosion layer is also included between the recording layer and the base film, and due to the formation of the erosion layer, a shift typically occurs between the red and blue carbonyl (C=O group) peaks.

[0033] In addition, the graph obtained from the results of the photothermal infrared spectroscopy analysis can be fitted with a Boltzmann Sigmoid function according to the following [Mathematical Formula 2].

[0034] [Mathematical formula 2]

[0035]

[0036] In mathematical formula 2,

[0037] A1: Initial y value, band area of ​​the carbonyl peak on one surface of the recording layer facing the base film

[0038] A2: Final y value, band area of ​​the carbonyl peak on one surface of the recording layer close to the base film

[0039] X0: The x value having the central y value, that is, the x value at the point where the area of ​​the carbonyl band of the recording layer is (A1+A2) / 2.

[0040] dx: time constant, i.e. the rate of decrease from A1 to A2.

[0041] After fitting the data obtained from the results of the photothermal infrared spectroscopy analysis with the Boltzmann Sigmoid function, the absolute value of the minimum value of the y value in the graph obtained by taking the first-order differential of the graph fitted with the Boltzmann Sigmoid function can be the maximum reduction rate of the spectral band area. That is, the maximum reduction rate of the spectral band area can be the absolute value of the minimum value of the slope in the graph analyzed by the photothermal infrared spectroscopy, or the absolute value of the minimum value of the slope in the graph obtained by fitting the graph analyzed by the photothermal infrared spectroscopy with the Boltzmann Sigmoid function.

[0042] The maximum reduction rate of the band area of ​​the photopolymer film according to one embodiment may be: 0.010 μm -1 or larger, 0.012μm -1 or larger, 0.014μm -1 or larger, 0.020μm -1 or larger, 0.030μm -1 or larger, 0.040μm -1 or larger, 0.050μm -1 or larger, 0.060μm -1 or larger, or 0.062μm -1 or larger, and 0.095μm -1 or smaller, 0.093μm -1 or smaller, 0.091μm -1 or smaller, 0.090μm -1 or smaller, 0.085μm -1 or smaller, or 0.082μm -1 If the maximum reduction rate of the band area is too small, the erosion layer described below is formed too thick, so that the thickness of the recording layer for actual recording becomes relatively thin, and thus low recording efficiency may be exhibited, and if the maximum reduction rate of the band area is too large, the erosion layer described below is not formed, so that the adhesion between the base film and the recording layer is reduced, and the reliability of heat resistance and moisture resistance may be reduced.

[0043] The photopolymer film according to one embodiment may further include an erosion layer between the substrate film and the recording layer. For example, the erosion layer and the recording layer may be sequentially formed on the substrate film. In addition, it may also be considered as a coating including the erosion layer and the recording layer. That is, the photopolymer film may include a coating including the erosion layer and the recording layer.

[0044] When producing a photopolymer film, the composition of the coating solution can be adjusted to form an etch layer on the substrate film. For example, the coating solution can include a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, and an etch solvent, etc., and when the coating solution is applied to the substrate film, the etch solvent can dissolve at least a portion of the substrate film so that the coating solution can penetrate.

[0045] Subsequently, during the drying process for forming the coating layer, the polymer matrix containing the siloxane-based polymer may be cured or cross-linked to form an erosion layer, wherein the erosion layer may contain a photoreactive monomer and / or a portion of the substrate. In addition, the erosion layer formed of the polymer matrix containing the siloxane-based polymer that has penetrated the substrate film may be physically bonded to the substrate film.

[0046] Therefore, the erosion layer is formed by the following method: the erosion solvent contained in the coating solution dissolves a part of the base film, the coating solution penetrates, and the polymer matrix contained in the penetrated coating solution is solidified or cross-linked. Therefore, the erosion layer can contain a part of the base film dissolved by the erosion solvent. In addition, the polymer matrix contained in the erosion layer and the base can be physically combined through a drying process.

[0047] On the other hand, a recording layer may be formed on the erosion layer, and the recording layer may contain a polymer matrix containing a siloxane-based polymer, a photoreactive monomer, and the like.

[0048] As mentioned above, since the erosion layer is formed on the base film, the adhesion between the optical film and the recording layer can be greatly improved, and by adjusting the degree of formation of the erosion layer, the reduction in the recording efficiency of the photopolymer film can be minimized while achieving excellent mechanical properties such as heat resistance and wet heat resistance reliability. The presence or absence of the erosion layer or the thickness of the erosion layer can be determined using the above-mentioned photothermal infrared spectroscopy analysis.

[0049] When producing a photopolymer film, the composition of the coating solution can be adjusted to form an erosion layer on the substrate film. For example, the coating solution can include a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, a solvent, etc., whereby the recording layer can include a polymer matrix containing a siloxane-based polymer and a photoreactive monomer.

[0050] In addition, the weight ratio between the photoreactive monomer and the polymer matrix containing the siloxane-based polymer can be controlled to form an erosion layer. For example, when the weight ratio between the photoreactive monomer and the polymer matrix containing the siloxane-based polymer is 45:55 to 90:10, 45:55 to 85:15, 45:55 to 80:20, 45:55 to 75:25, 45:55 to 72:28, 48:52 to 72:28, an erosion layer can be formed between the base film and the recording layer. If the amount of the photoreactive monomer is too small relative to the polymer matrix containing the siloxane-based polymer, the erosion layer may not be formed, and if the amount of the photoreactive monomer is too large relative to the polymer matrix containing the siloxane-based polymer, the thickness of the recording layer may become thinner, so that the recording efficiency may be reduced.

[0051] When the coating solution is applied to the substrate film, the photoreactive monomer and the solvent may dissolve and penetrate at least a portion of the substrate film. Thereafter, during a drying process for forming a coating layer, the polymer matrix containing the siloxane-based polymer and the photoreactive monomer may be cured or cross-linked to form an erosion layer. In addition, the photoreactive monomer that has penetrated the substrate film may be physically or chemically bonded to the substrate film.

[0052] Therefore, the erosion layer may include a photoreactive monomer, and the erosion layer may be physically or chemically bonded to the substrate film. For example, since the photoreactive monomer included in the erosion layer is physically bonded to the substrate film, physical bonding of the erosion layer and the substrate film may be achieved. In addition, the coating may include a polymer matrix containing a siloxane-based polymer and a photoreactive monomer.

[0053] On the other hand, a recording layer may be formed on the erosion layer, and the recording layer may contain a polymer matrix containing a siloxane-based polymer, a photoreactive monomer, and the like.

[0054] As mentioned above, the formation of the etching layer on the base film makes it possible to greatly improve the adhesion between the optical film and the recording layer, and by adjusting the degree of etching layer formation, the reduction in the recording efficiency of the photopolymer film can be minimized while achieving excellent mechanical properties such as heat resistance and wet heat resistance reliability. The presence or absence of the etching layer or the thickness of the etching layer can be determined using the above-mentioned photothermal infrared spectroscopy analysis.

[0055] The thickness of the erosion layer may be 1.0 μm or more, 1.5 μm or more, 2.0 μm or more, 2.3 μm or more, or 2.5 μm or more, and 10.0 μm or less, 9.0 μm or less, 8.0 μm or less, 7.0 μm or less, 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 base film and the recording layer may be reduced, and the heat resistance and moisture resistance reliability may be reduced. If the thickness of the erosion layer becomes too thick, the thickness of the recording layer actually performing recording may become quite thin, thereby exhibiting low recording efficiency.

[0056] The thickness of the recording layer may be 3.0 μm or more, 3.5 μm or more, or 4.0 μm or more, and 8.0 μm or less, 7.0 μm or less, 6.8 μm or less, or 6.7 μm or less. If the thickness of the recording layer is too thin, it may show low recording efficiency, and if the thickness of the above recording layer is too thick, the thickness of the erosion layer may become thinner, and thus the adhesion between the base film and the recording layer may be reduced.

[0057] The thickness of the coating may be 5.0 μm or more, 5.5 μm or more, 6.0 μm or more, and 20.0 μm or less, 15.0 μm or less, or 10.0 μm or less.

[0058] The photopolymer film may include a coating layer including an etchant layer and a recording layer, and a thickness ratio of the etchant layer to the coating layer may be 20.0% or more and 70.0% or less, for example, 21.0% or more, 22.0% or more, 23.0% or more, 24.0% or more, 25.0% or more, 30.0% or more, or 35.0% or more, and 70.0% or less, 68.0% or less, 66.0% or less, 65.0% or less, 63.0% or less, or 62.0% or less. If the thickness ratio is too small, the adhesion between the base film and the recording layer may be reduced, and the heat resistance and moisture resistance reliability may be deteriorated, and if the thickness ratio is too large, the thickness of the recording layer actually performing recording may become thinner, thereby exhibiting low recording efficiency.

[0059] The substrate film according to one embodiment is not particularly limited as long as it is a substrate film capable of forming an erosion layer, and for example, it may be a cellulose ester-based substrate film, a polyester-based substrate film, a poly(meth)acrylate-based substrate film, a polycarbonate-based substrate film, a cycloolefin (COP)-based substrate film, or an acryl-based substrate film.

[0060] In addition, the base film may be a triacetylcellulose (TAC)-based film, a polyethylene terephthalate (PET)-based base film, a polymethyl methacrylate (PMMA)-based base film, a cycloolefin (COP)-based base film, or an acryl-based base film.

[0061] The thickness of the substrate film may be 20 μm or more, 30 μm or more, 40 μm or more, and 500 μm or less, 300 μm or less, 100 μm or less, 80 μm or less, or 60 μm or less. The substrate film may satisfy the above thickness and thus exhibit excellent mechanical properties, water resistance, low moisture permeability, etc.

[0062] Photopolymer films can be used for hologram recording purposes.

[0063] According to another embodiment of the present disclosure, a composition for forming a photopolymer film may be provided, comprising a coating solution comprising a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, and an etching solvent, wherein the content of the etching solvent is 25 wt % or more and 70 wt % or less relative to 100 wt % of the coating solution.

[0064] As mentioned above, when the resin composition for forming a photopolymer film is applied to a base film, an etching solvent may dissolve and penetrate at least a portion of the base film to form an etching layer.

[0065] The coating solution may contain the etching solvent in an amount of 25 wt % or more and 70 wt % or less, 28 wt % or more and 68 wt % or less, 30 wt % or more and 65 wt % or less, or 35 wt % or more and 60 wt % or less relative to 100 wt % of the coating solution. The coating solution contains the etching solvent in the amounts mentioned above, and thus an etching layer may be formed.

[0066] In addition, the etching solvent may be at least one selected from a ketone-based solvent, an ester-based solvent, a nitrogen-based compound solvent, a halogenated hydrocarbon-based solvent, and an aromatic hydrocarbon-based solvent. The ketone-based solvent may be methyl ethyl ketone, methyl isobutyl ketone, or acetone, and the ester-based solvent may be ethyl acetate, etc.

[0067] Furthermore, the resin composition for forming a photopolymer film may further include a non-eroding solvent in addition to the above-mentioned etching solvent, and the non-eroding solvent may be isopropyl alcohol or the like.

[0068] The etching solvent may be contained in an amount of 35 wt % or more and 90 wt % or less, 40 wt % or more and 85 wt % or less, or 45 wt % or more and 80 wt % or less, relative to 100 wt % of the total solvent contained in the resin composition for forming the photopolymer film. If the amount of the etching solvent is too small, an etching layer is not formed or an excessively thin etching layer is formed, so that the adhesion between the base film and the recording layer is reduced, and the reliability of heat resistance and moisture resistance may be reduced. If the amount of the etching solvent is too large, the thickness of the recording layer actually performing recording may become quite thin, thereby exhibiting low recording efficiency.

[0069] The resin composition for forming a photopolymer film according to another embodiment may include a polymer matrix containing a siloxane-based polymer or a precursor thereof. The polymer matrix containing a siloxane-based polymer or a precursor thereof may be used as a support for a photopolymer film produced using the resin composition.

[0070] In addition, the polymer matrix containing a siloxane-based polymer or its precursor has a relatively low refractive index (e.g., n=1.40 to 1.55), and thus can play a role in enhancing the refractive index modulation of the photopolymer film. In addition, the polymer matrix is ​​a polyol-based matrix and contains a siloxane-based polymer, and when a catalyst such as a Pt-based catalyst is introduced, the matrix can be cross-linked at a high speed even at room temperature.

[0071] In addition, the siloxane-based polymer may include one or more silane functional groups (Si—H). In addition, the siloxane-based polymer may include a repeating unit of the following Chemical Formula 1 or a repeating unit of the following Chemical Formula 2.

[0072] [Chemical formula 1]

[0073]

[0074] Wherein, in each repeating unit of Chemical Formula 1, R1 to R2 may be the same as or different from each other and are hydrogen, halogen or an alkyl group having 1 to 10 carbon atoms,

[0075] n is the number of repetitions of the repeating unit, which is 1 to 10,000,

[0076] In at least one of the repeating units, R1 may be an alkyl group having 1 to 10 carbon atoms, and R2 may be hydrogen.

[0077] [Chemical formula 2]

[0078]

[0079] In each repeating unit of Chemical Formula 2, R 11 To R13 may be the same as or different from each other and are hydrogen, halogen or an alkyl group having 1 to 10 carbon atoms,

[0080] n is the number of repetitions of the repeating unit, which is 1 to 10,000,

[0081] In at least one of the repeating units, R 11 and R 13 is an alkyl group having 1 to 10 carbon atoms, and R 12 is hydrogen, or

[0082] R 11 and R 12 is an alkyl group having 1 to 10 carbon atoms, and R 13 For hydrogen.

[0083] The number average molecular weight (as measured by GPC) of the siloxane-based polymer may be from 200 to 4,000, or from 350 to 2,500.

[0084] In addition, in addition to the siloxane-based polymer containing one or more silane functional groups (Si-H), the polymer matrix can also include the (meth) acrylic polyol containing two or more hydroxyl groups (-OH). Therefore, the polymer matrix contains both silane functional groups (Si-H) and hydroxyl groups (-OH), wherein the molar ratio (SiH / OH) of the silane functional groups (Si-H) to the hydroxyl groups (OH) can be 0.80 or more and 3.5 or less, the lower limit 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. In addition, the type and content of the siloxane-based polymer and the (meth) acrylic polyol in the polymer matrix can be controlled so as to meet the molar ratio (SiH / OH).

[0085] The resin composition for forming the photopolymer film may contain a polymer matrix containing a siloxane-based polymer or a precursor thereof in an amount of 25 wt % or more and 35 wt % or less, or 28 wt % or more and 33 wt % or less relative to 100 wt % of the solid content of the resin composition. If the amount of the polymer matrix containing the siloxane-based polymer or a precursor thereof is too large, an erosion layer may not be formed or an overly thin erosion layer may be formed, thereby reducing the adhesion between the base film and the recording layer and reducing the reliability of heat resistance and moisture resistance. If the amount of the polymer matrix containing the siloxane-based polymer or a precursor thereof is too small, the thickness of the recording layer on which recording is actually performed may actually become thinner, thereby showing a low recording efficiency.

[0086] In addition, the content of the etching solvent may be 25% by weight or more and 65% by weight or less, 30% by weight or more and 60% by weight or less, or 35% by weight or more and 55% by weight or less, relative to 100% by weight of the polymer matrix containing the siloxane-based polymer or its precursor. If the content of the etching solvent is too low relative to the polymer matrix containing the siloxane-based polymer or its precursor, an etching layer may not be formed or may be formed too thinly, which may lead to a reduction in the adhesion between the base film and the recording layer and a deterioration in the reliability of heat resistance and moisture resistance. If the content of the etching solvent is too large, the thickness of the recording layer actually recorded may actually become quite thin, thereby showing a low recording efficiency.

[0087] The resin composition for forming a photopolymer film according to another embodiment may further include a photoreactive monomer.

[0088] The photoreactive monomer may include a multifunctional (meth)acrylate monomer or a monofunctional (meth)acrylate monomer.

[0089] Examples of the photoreactive monomer may include (meth)acrylate-based α,β-unsaturated carboxylic acid derivatives such as (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid, etc.; or compounds containing a vinyl group or a thiol group.

[0090] Examples of photoreactive monomers may include polyfunctional (meth)acrylate monomers having a refractive index of 1.5 or more, 1.53 or more, or 1.5 to 1.7. The polyfunctional (meth)acrylate monomers having a refractive index of 1.5 or more, 1.53 or more, or 1.5 to 1.7 may contain halogen atoms (bromine, iodine, etc.), sulfur (S), phosphorus (P), or aromatic rings.

[0091] More specific examples of the multifunctional (meth)acrylate monomer having a refractive index of 1.5 or greater include bisphenol A-modified diacrylate type, fluorene acrylate series (HR6022 manufactured by Miwon Specialty Chemical Co., Ltd., etc.), bisphenol fluorene epoxy acrylate series (HR6100, HR6060, HR6042, etc. manufactured by Miwon Specialty Chemical Co., Ltd.), and halogenated epoxy acrylate series (HR1139, HR3362, etc. manufactured by Miwon Specialty Chemical Co., Ltd.).

[0092] Another example of the photoreactive monomer may include a monofunctional (meth) acrylate monomer. The monofunctional (meth) acrylate monomer may contain an ether bond and a fluorene functional group in the molecule. Specific examples of such monofunctional (meth) acrylate monomers include phenoxybenzyl (meth) acrylate, o-phenylphenol ethylene oxide (meth) acrylate, benzyl (meth) acrylate, 2-(phenylthio) ethyl (meth) acrylate, biphenyl methyl (meth) acrylate, and the like.

[0093] Meanwhile, the weight average molecular weight of the photoreactive monomer may be 50 g / mol to 1000 g / mol, or 200 g / mol to 600 g / mol. The weight average molecular weight refers to a weight average molecular weight measured by a GPC method in terms of polystyrene conversion.

[0094] The photopolymer composition for forming the photopolymer film may contain the photoreactive monomer in an amount of 6 wt % or more and 30 wt % or less, 8 wt % or more and 25 wt % or less, or 10 wt % or more and 20 wt % or less relative to 100 wt % of the solid content of the composition. If the amount of the photoreactive monomer is too small, an erosion layer will not be formed or an overly thin erosion layer will be formed, so that the adhesion between the base film and the recording layer is reduced, and the heat resistance and moisture resistance reliability may be reduced. If the amount of the photoreactive monomer is too large, the thickness of the recording layer on which recording is actually performed may actually become thinner, thereby showing low recording efficiency.

[0095] In addition, based on 100 parts by weight of the polymer matrix containing the siloxane-based polymer, the resin composition for forming the photopolymer film may contain 50 parts by weight to 300 parts by weight of the photoreactive monomer, for example, the lower limit 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.

[0096] In addition, the content of the etching solvent may be 25 wt % or more and 65 wt % or less, 30 wt % or more and 60 wt % or less, or 35 wt % or more and 55 wt % or less relative to 100 wt % of the photoreactive monomer. If the content of the etching solvent is too small relative to the photoreactive monomer, an etching layer may not be formed or an overly thin etching layer may be formed, thereby reducing the adhesion between the base film and the recording layer and reducing the reliability of heat resistance and moisture resistance. If the content of the etching solvent is too large, the thickness of the recording layer on which recording is actually performed may actually become thinner, thereby exhibiting low recording efficiency.

[0097] The resin composition for forming a photopolymer film according to other embodiments may include a photoinitiator. The photoinitiator is a compound that is activated by light or actinic radiation and initiates polymerization of a compound containing a photoreactive functional group, such as a photoreactive monomer.

[0098] As the photoinitiator, a generally known photoinitiator may be used without particular limitation, but specific examples thereof include a photoradical polymerization initiator, a photocationic polymerization initiator, or a photoanionic polymerization initiator.

[0099] Specific examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxypyridine Salts, thioxanthone derivatives, amine derivatives, etc. More specifically, examples of the photoradical polymerization initiator include 1,3-di(tert-butyldioxycarbonyl)benzophenone, 3,3',4,4"-tetra(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isobutylene glycol, oxazolidinone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (product name: Irgacure 651 / manufacturer: BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Irgacure 184 / manufacturer: BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (product name: Irgacure 369 / manufacturer: BASF), and bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium (product name: Irgacure 784 / manufacturer: BASF), Ebecryl P-115 (manufacturer: SK entis), etc.

[0100] The photocationic polymerization initiator may include a diazonium salt, a sulfonium salt or an iodine salt. Salts, and examples thereof include sulfonates, iminosulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η6-phenyl)(η5-cyclopentadienyl)iron(II), etc. In addition, benzoin toluenesulfonate, 2,5-dinitrobenzyl toluenesulfonate, N-toluenesulfonylphthalimide, etc. can be mentioned. More specific examples of the photocationic polymerization initiator include commercially available products such as Cyracure UVI-6970, Cyracure UVI-6974, and Cyracure UVI-6990 (manufacturer: Dow Chemical Co., USA), Irgacure 264 and Irgacure 250 (manufacturer: BASF), or CIT-1682 (manufacturer: Nippon Soda).

[0101] The photoanionic polymerization initiator may be a borate such as butyryl chloride butyl triphenyl borate, etc. More specific examples of the photoanionic polymerization initiator include commercially available products such as Borate V (manufacturer: Spectra Group).

[0102] In addition, the photopolymer composition may contain a unimolecular (type I) initiator or a bimolecular (type II) initiator. The (type I) system for free radical photopolymerization may include, for example, aromatic ketone compounds such as benzophenone, alkylbenzophenone, 4,4′-bis(dimethylamino)benzophenone (Michler's ketone), anthrone and halogenated benzophenone or mixtures of these types in combination with tertiary amines. Bimolecular (type II) initiators may include benzoin and its derivatives, benzyl ketal, acylphosphine oxide (e.g., 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide), phenylglyoxylate, camphorquinone, α-aminoalkylphenone, α,α-dialkoxyacetophenone, 1-[4-(phenylthio)phenyl]octane-1,2-dione 2-(O-benzoyloxime), α-hydroxyalkylphenone, etc.

[0103] In addition, the resin composition for forming a photopolymer film according to another embodiment may also include a fluorine-based compound. Since the fluorine-based compound has stability, almost no reactivity, and has low refractive properties, when the fluorine-based compound is added to the resin composition, it can further reduce the refractive index of the polymer matrix, thereby maximizing the refractive index modulation with the monomer. The fluorine-based compound can act as a plasticizer.

[0104] The fluorine-based compound may include at least one functional group selected from an ether group, an ester group, and an amide group and at least two difluoromethylene groups. More specifically, the fluorine-based compound may have a structure represented by the following Chemical Formula 4, wherein a functional group including an ether group is bonded to both ends of a central functional group including a direct bond or an ether bond between two difluoromethylene groups.

[0105] [Chemical formula 4]

[0106]

[0107] Among them, in chemical formula 4,

[0108] R 11 and R 12 are each independently difluoromethylene, R 13 and R 16 are each independently a methylene group, R 14 and R 15 are each independently difluoromethylene, R 17 and R 18 Each is independently a polyalkylene oxide group, and m is an integer of 1 or more, or 1 to 10, or 1 to 3.

[0109] Preferably, in Chemical Formula 4, R 11 and R 12 are each independently difluoromethylene, R 13 and R 16 are each independently a methylene group, R 14 and R 15 are each independently difluoromethylene, R 17 and R 18 are each independently a 2-methoxyethoxymethoxy group, and m is an integer of 2.

[0110] The refractive index of the fluorine-based compound may be less than 1.45, or 1.3 or more and less than 1.45. As mentioned above, since the refractive index of the photoreactive monomer is 1.5 or more, the fluorine-based compound can further reduce the refractive index of the polymer matrix by a lower refractive index than the photoreactive monomer, thereby maximizing the refractive index modulation with the monomer.

[0111] In addition, the resin composition for forming the photopolymer film may contain 20 to 200 parts by weight of a fluorine-based compound relative to 100 parts by weight of a polymer matrix containing a siloxane-based polymer, for example, the lower limit may be 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 200 parts by weight or less, 190 parts by weight or less, or 180 parts by weight or less.

[0112] In addition, the content of the fluorine-based compound may be 30 to 150 parts by weight, or 50 to 110 parts by weight, relative to 100 parts by weight of the photoreactive monomer, and the refractive index of the polymer matrix may be 1.46 to 1.53. If the content of the fluorine-based compound is excessively reduced relative to 100 parts by weight of the photoreactive monomer, the refractive index modulation value after recording may decrease due to the lack of a low refractive index component, and if the content of the fluorine-based compound is excessively increased relative to 100 parts by weight of the photoreactive monomer, there is a problem in that haze occurs due to compatibility problems with other components, or some of the fluorine-based compound may flow out to the surface of the recording layer.

[0113] The weight average molecular weight (measured by GPC) of the fluorine-based compound may be 300 or more, or 300 to 1000. The specific method of measuring the weight average molecular weight is as mentioned above.

[0114] The polymer matrix containing the siloxane-based polymer or a precursor thereof may further comprise a fluorine-based compound.

[0115] On the other hand, the resin composition for forming the photopolymer film may further include a photosensitizer. The photosensitizer acts as a sensitizing pigment that sensitizes the photoinitiator. More specifically, the photosensitizer can be excited by light irradiated on the photopolymer composition, and may also act as an initiator to initiate polymerization of monomers and crosslinking monomers. Relative to 100% by weight of the resin composition, the photosensitizer may be included in an amount of 0.01% by weight to 30% by weight, or 0.05% by weight to 0.50% by weight.

[0116] Examples of photosensitizing dyes are not particularly limited, and various compounds generally known in the art can be used. Specific examples of photosensitizing dyes include sulfonium derivatives of anthracene (9,1-bc) naphtho (3,2,1-kl) acridine (ceramidonine), new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose red, thionine, basic yellow, chlorinated pinacol cyanol, rhodamine 6G, gallocyanine, ethyl violet, Victoria Blue R, lapis lazuli blue, quinaldine red, crystal violet, brilliant green, basic orange G, Darrow Red, Pyronin Y, basic red 29, pyranose, chlorinated cyanol ... Iodide, safranin O, cyanine, methylene blue, azure A, or a combination of two or more thereof.

[0117] The polymer matrix comprising the siloxane-based polymer or a precursor thereof may also contain a dye.

[0118] The resin composition for forming the photopolymer film may also include other additives, catalysts, etc. For example, the resin composition may include a commonly known catalyst for promoting the polymerization of a polymer matrix or a photoreactive monomer. Examples of catalysts include Karstedt catalysts, rhodium-based catalysts, iridium-based catalysts, rhenium-based catalysts, platinum-based catalysts, iron-based catalysts, nickel-based catalysts, alkali metals, and alkaline earth metal catalysts. As non-metallic catalysts, Lewis acid-based catalysts, carbene-based catalysts, etc. may be used.

[0119] Examples of other additives include defoamers or phosphate-based plasticizers, and the defoamer may be a silicone-based reactive additive such as Tego Rad 2500. Examples of plasticizers include phosphate compounds such as tributyl phosphate, and the plasticizer may be added with the fluorine-based compound at 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.

[0120] The components contained in the resin composition for forming a photopolymer are uniformly mixed, and then dried and cured at a temperature of 30°C or higher and 180°C or lower, 40°C or higher and 100°C or lower, or 50°C or higher and 90°C or lower to produce a photopolymer film according to one embodiment.

[0121] For example, the resin composition can be prepared by first uniformly mixing the components forming the polymer matrix or its precursor, and then crosslinking the matrix into a liquid state at room temperature using a Pt-based catalyst. A photopolymerizable monomer and an initiator can be added later to prepare a resin composition for forming a final photopolymer film.

[0122] In order to mix the components contained in the resin composition, a generally known mixing device, a stirrer, a mixer, etc. can be used without any particular limitation, and the temperature during the mixing process can be 0° C. or higher and 100° C. or lower, 10° C. or higher and 80° C. or lower, or 20° C. or higher and 60° C. or lower. The temperature of drying can be changed according to the composition of the photopolymer, and can be accelerated, for example, by heating to a temperature of 30° C. to 180° C. During drying, the resin composition can be injected into or applied onto a predetermined base film or mold.

[0123] The methods and equipment commonly used for coating resin combinations on substrate films can be used without any particular restrictions. For example, rod coating (e.g., rod coating using a Meyer rod, etc.), gravure coating, double-roll reverse coating, vacuum slot die coating, double-roll coating, etc. can be used.

[0124] According to still another embodiment of the present disclosure, a holographic recording medium including the photopolymer film may be provided.

[0125] As mentioned above, the photopolymer film has high adhesion between the recording layer and the base film, and optimizes recording efficiency while providing excellent heat resistance and moisture-heat resistance reliability. Therefore, the holographic recording medium including the photopolymer film can also optimize recording efficiency while providing excellent heat resistance and moisture-heat resistance reliability.

[0126] The polymer film can be prepared into a hologram for optical applications in the entire visible light range and near ultraviolet range (300nm to 800nm) via a predetermined exposure process.

[0127] As a method of recording a visual hologram on a holographic recording medium including the photopolymer film, a generally known method may be used without particular limitation.

[0128] For example, a visual hologram may be recorded by a method of selectively polymerizing a photoreactive monomer contained in the photopolymer film using a coherent laser.

[0129] According to another embodiment of the present disclosure, an optical element including the photopolymer film may be provided. In addition, the optical element may include a holographic recording medium including the photopolymer film.

[0130] Specific examples of optical elements include optical lenses, reflectors, deflecting mirrors, filters, diffuser screens, diffraction elements, light guides, waveguides, holographic optical elements with projection screen and / or mask functions, light diffusers and media for optical storage systems, optical wavelength multiplexers, reflective and transmissive color filters, etc.

[0131] Examples of optical elements including the photopolymer film may include a hologram display device. The hologram display device includes a light source unit, an input unit, an optical system, and a display unit. The light source unit is a portion that irradiates a laser beam for providing, recording, and reproducing three-dimensional image information of an object in the input unit and the display unit. In addition, the input unit is a portion that pre-inputs the three-dimensional image information of the object to be recorded on the display unit, specifically a portion in which the three-dimensional information of the object (such as the intensity and phase of light in each space) can be input into the electrically addressed liquid crystal SLM, where the input beam can be used. The optical system may include a reflector, a polarizer, a beam splitter, a beam gate, a lens, and the like. The optical system may be allocated to an input beam for sending a laser beam emitted from the light source unit to the input unit, a recording beam for sending a laser beam to the display unit, a reference beam, an erasing beam, a reading beam, and the like.

[0132] The display unit can receive the three-dimensional image information of the object from the input unit, record it on the hologram plate including the optically addressed SLM, and reproduce the three-dimensional image of the object. At this time, the three-dimensional image information of the object can be recorded by the interference of the input light beam and the reference light beam. The three-dimensional image information of the object recorded on the hologram plate can be reproduced as a three-dimensional image by the diffraction pattern generated by the read light beam. The erase light beam can be used to quickly remove the formed diffraction pattern. On the other hand, the hologram plate can be moved between the position of the input three-dimensional image and the position of the reproduced three-dimensional image.

[0133] Beneficial Effects

[0134] According to the present disclosure, a photopolymer film having optimized recording efficiency while exhibiting excellent heat resistance and wet heat resistance reliability and improved adhesion between a base film and a recording layer, a composition for forming the same, a holographic recording medium and an optical element including the same can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0135] Figure 1 is a schematic diagram showing a cross section of a photopolymer film.

[0136] Figure 2 Schematic diagram showing the shift of a carbonyl (C═O group) peak as a result of photothermal infrared spectroscopy analysis in the thickness direction from one surface of a recording layer of a photopolymer film.

[0137] Figure 3 It is a graph showing the results of photothermal infrared spectroscopy analysis of Examples and Comparative Examples fitted with a Boltzmann sigmoid function.

[0138] Figure 4 It is a graph showing the first-order differential of a photothermal infrared spectroscopic analysis graph.

[0139] Figure 5 This is a photograph of a cross section of the photopolymer film of Example 1 taken using a SEM.

[0140] Figure 6 This is a photograph of a cross section of the photopolymer film of Example 2 taken using a SEM.

[0141] Figure 7 This is a photograph of a cross section of the photopolymer film of Comparative Example 1 taken using a SEM.

[0142] Figure 8 The following are photographs showing the results of adhesion evaluation of Examples and Comparative Examples. DETAILED DESCRIPTION

[0143] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the following examples. However, the following examples are provided for illustrative purposes only, and the scope of the present disclosure is not intended to be limited thereby.

[0144] <Preparation Example>

[0145] Preparation Example 1: Preparation of (meth)acrylic polyol

[0146] 132g butyl acrylate, 420g ethyl acrylate and 48g hydroxybutyl acrylate are added to a 2L jacket reactor and diluted with 1200g ethyl acetate. The reaction temperature is set to 60°C to 70°C, and the mixture is stirred for about 30 minutes to 1 hour. 0.42g of n-dodecyl mercaptan (n-DDM) is further added, and further stirred for about 30 minutes. Then, 0.24g of AIBN as a polymerization initiator is added, and polymerization is carried out at the reaction temperature for 4 hours or more, and maintained until the residual acrylate content becomes less than 1%. Thus, a copolymer based on (meth) acrylate in which hydroxyl groups are located in the side chains (weight average molecular weight of about 300,000, OH equivalent of about 1802g / equivalent) is prepared.

[0147] Preparation Example 2: Preparation of fluorine-based compounds

[0148] 20.51 g of 2,2'-{oxybis[(1,1,2,2-tetrafluoroethane-2,1-diyl)oxy]}bis(2,2-difluoroethane-1-ol) was added to a 1000 mL flask and dissolved in 500 g of tetrahydrofuran, to which 4.40 g of sodium hydroxide (60% dispersion in mineral oil) was carefully added 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. When all the reactants were determined to be consumed by 1H NMR, 29 g of a liquid product with a purity of 95% or more was obtained using dichloromethane treatment, with a yield of 98%. The weight average molecular weight of the prepared fluorine-based compound was 586, and the refractive index measured with an Abbe refractometer was 1.361.

[0149] Examples and Comparative Examples: Production of Photopolymer Films

[0150] Example 1

[0151] 2.5 g of the (meth) acrylic polyol prepared in Preparation Example 1, 0.10 g of a siloxane-based polymer containing a silane (Si-H) functional group (product name: poly(methylhydrogensiloxane), manufacturer: Sigma-Aldrich, Mn=about 390), 1.00 g of the fluorine-based compound prepared in Preparation Example 2, 0.50 g of dye HNu-640 (Spectra), and 0.60 g of a photoreactive monomer (high refractive index acrylate, refractive index 1.600, HR6042, Miwon Specialty Chemical) were mixed with a solvent while shielding from light so that the solid content was 25% of 100 parts by weight of the total coating solution, and the ratio was set as shown in Table 1 below, and the mixture was stirred with a paste mixer for about 10 minutes. A Karstedt (Pt-based) catalyst for crosslinking of the substrate was added, and after crosslinking, a borate V (Spectra Group) initiator was added to the coating solution, and the mixture was further mixed for 5 minutes or more to prepare a coating solution. The coating solution was coated on a 40 μm thick triacetyl cellulose (TAC) base film to a thickness of about 8 μm using a Meyer bar, and dried at 60° C. within 10 minutes to form a coating layer.

[0152] Example 2

[0153] A photopolymer film was produced in the same manner as in Example 1, except that the solvents shown in the following Table 1 were used.

[0154] Example 3

[0155] 1.70 g (solid content 0.52 g) of the (meth) acrylic polyol prepared in Preparation Example 1, 0.09 g of a siloxane-based polymer containing a silane (Si-H) functional group (product name: poly(methylhydrogensiloxane), manufacturer: Sigma-Aldrich, Mn = about 390), 0.80 g of a fluorine-based compound prepared in Preparation Example 2, 0.40 g of dye HNu-640 (Spectra), 0.56 g of a photoreactive monomer (high refractive index acrylate, refractive index 1.600, HR6042, Miwon Specialty Chemical), 0.85 g of methyl ethyl ketone, 0.75 g of methyl isobutyl ketone, 0.18 g of ethyl acetate and 4.45 g of isopropyl alcohol as a solvent were mixed with the solvent while shielding from light, and the mixture was stirred with a paste mixer for about 10 minutes. 0.09 g of Karstedt (Pt-based) catalyst for matrix crosslinking was added, and after crosslinking, 0.15 g of borate V (Spectra Group) initiator was added to the coating solution, and the mixture was further mixed for 5 minutes or more to prepare a coating solution. The coating solution was coated on a 40 μm thick triacetyl cellulose (TAC) substrate film to a thickness of about 8 μm using a Meyer rod and dried within 10 minutes at 60° C. to form a coating. At this time, the coating solution was prepared so that the weight ratio of the photoreactive monomer and the polymer matrix was 48:52 in the total mass of the coating solution.

[0156] Meanwhile, the content of ethyl acetate in the following Table 2 corresponds to the sum of the content of the solvent (ethyl acetate) separately added to the paste mixer and the content of the solvent (ethyl acetate) contained in the “(meth)acrylic polyol prepared in Preparation Example 1”.

[0157] Examples 4 to 8

[0158] A photopolymer film was produced in the same manner as in Example 3, except that polyol, siloxane-based polymer, photoreactive monomer, fluorine-based compound, dye, initiator, catalyst, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and isopropyl alcohol were used in the contents shown in Table 2 below.

[0159] Comparative Example 1

[0160] A photopolymer film was produced in the same manner as in Example 1, except that the solvents shown in the following Table 1 were used.

[0161] Comparative Examples 2 and 3

[0162] A photopolymer film was produced in the same manner as in Example 3, except that polyol, siloxane-based polymer, photoreactive monomer, fluorine-based compound, dye, initiator, catalyst, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and isopropyl alcohol were used in the contents shown in Table 2 below.

[0163] [Table 1]

[0164]

[0165] [Table 2]

[0166]

[0167] <Evaluation>

[0168] 1. Measurement of the maximum reduction rate of the band area in the photothermal infrared (PTIR) spectrum analysis diagram

[0169] Photothermal infrared (PTIR) spectroscopy was performed at 1 μm intervals in the thickness direction starting from the recording layer surface of the photopolymer films of Examples and Comparative Examples (specifically, the surface of the recording layer facing the acrylic substrate), and the analysis conditions of the photothermal infrared spectroscopy were as follows.

[0170] <Photothermal infrared spectroscopy analysis conditions>

[0171] - Equipment: mIRage (Photothermal Spectroscopy Corp.)

[0172] - Light source: tunable pulsed mid-infrared quantum cascade laser (1800cm-1 to 800cm-1), probe laser (532nm)

[0173] - Spectral resolution: spectral resolution 1cm -1 , spatial resolution 500nm

[0174] -Microscope mode: Reflection mode

[0175] -Detector: Avalanche Photodiode Detector

[0176] Then, the photothermal infrared spectroscopy analysis results analyzed at 1 μm intervals in the thickness direction were fitted using the Boltzmann Sigmoid function according to the following [Mathematical Formula 2]. Figure 3 Graphs showing the results of photothermal infrared spectroscopy analysis using a Boltzmann Sigmoid function fit.

[0177] [Mathematical formula 2]

[0178]

[0179] In mathematical formula 2,

[0180] A1: Initial y value, band area of ​​the carbonyl peak on one surface of the recording layer facing the base film

[0181] A2: Final y value, band area of ​​the carbonyl peak on one surface of the recording layer close to the base film

[0182] X0: The x value having the central y value, that is, the x value at the point where the area of ​​the carbonyl band of the recording layer is (A1+A2) / 2.

[0183] dx: time constant, i.e. the rate of decrease from A1 to A2.

[0184] Then, the absolute value of the minimum value of the y value in the graph of the first-order differential of the graph fitted with the Boltzmann Sigmoid function (i.e., the maximum reduction rate of the band area) is shown in the following Table 3. At this time, Figure 4 It is a graph showing the first order differential of the photothermal infrared spectroscopic analysis graph. In addition, in Table 3, if the maximum reduction rate of the band area is not measured, it is represented as "-".

[0185] 2. Measurement of the thickness of the recording layer and the erosion layer

[0186] The cross sections of the photopolymer films of Examples and Comparative Examples were analyzed using a scanning electron microscope (SEM) to measure the thickness of the recording layer and the erosion layer. In addition, the ratio of the thickness of the erosion layer to the total thickness of the coating was calculated, and the results are shown in Table 3 below.

[0187] on the other hand, Figure 5 This is a photograph of a cross section of the photopolymer film of Example 1 taken using a SEM. Figure 6 This is a photograph of a cross section of the photopolymer film of Example 2 taken using a SEM. Figure 7 This is a photograph of a cross section of the photopolymer film of Comparative Example 1 taken using a SEM.

[0188] 3. Evaluation of Adhesion (Cross Cut)

[0189] After recording was performed on the recording layers of the photopolymer films of Examples and Comparative Examples using laser light having a wavelength of 660 nm, a cross cut test was performed on the recording layers.

[0190] Specifically, 100 checkerboard-shaped cuts (10 in width × 10 in height) were made on the recording layer of the photopolymer film so that the width and height were each 1 mm, and peeling was performed twice using an adhesive tape (product name: CT-24, manufacturer: Nichiban). After that, the recording layer and the base film were separated, and the state of being scratched or peeled was evaluated according to the following <Evaluation Criteria>, and the results are shown in Table 3 below.

[0191] At the same time, Figure 8 , (a) is a photograph of the cross cut evaluation result of Example 1, (b) is a photograph of the cross cut evaluation result of Example 2, and (c) is a photograph of the cross cut evaluation result of Comparative Example 1.

[0192] <Evaluation Criteria>

[0193] 5B: The amount of remaining space that has not fallen off is 100% of the total space

[0194] 4B: The amount of remaining space that has not fallen off is 95% or more but less than 100% of the total space

[0195] 3B: The amount of remaining space that has not fallen off is 85% or more but less than 95% of the total space

[0196] 2B: The amount of remaining space that has not fallen off is 65% or more but less than 85% of the total space

[0197] 1B: The amount of remaining space that has not fallen off is 35% or more but less than 65% of the total space

[0198] 0B: The amount of remaining space that is not dropped is 0% or more but less than 35% of the total space

[0199] 4. Heat resistance and moisture resistance reliability evaluation

[0200] After recording was performed on the recording layers of the photopolymer films of Examples and Comparative Examples using laser light having a wavelength of 660 nm, heat resistance and moisture resistance reliability were evaluated.

[0201] Specifically, the reflectance spectrum of the recording layer of the photopolymer film is measured using an ultraviolet-visible spectrophotometer to determine the wavelength (λ, nm) at which the reflectance peak appears.

[0202] Then, in order to evaluate the heat resistance reliability, the recording layer of the photopolymer film was attached to a glass plate with BPSA (Barrier pressure-sensitive adhesive) and left at a temperature of 95° C. for 72 hours. Thereafter, the reflectance spectrum of the recording layer of the photopolymer film was measured again using an ultraviolet-visible spectrophotometer, and the degree of shift of the reflection peak was determined as a change in wavelength (Δλ, nm), and the results are shown in Table 2 below.

[0203] In addition, in order to evaluate the wet heat reliability, the recording layer of the photopolymer film was attached to a glass plate with BPSA and left at a temperature of 85° C. and a humidity of 85% for 72 hours. Thereafter, the reflectance spectrum of the recording layer of the photopolymer film was measured again with an ultraviolet-visible spectrophotometer, the degree of shift of the reflection peak was determined as a change in wavelength (Δλ, nm), and the results are shown in Table 3 below.

[0204] 5. Evaluation of recording efficiency

[0205] After recording was performed on the recording layers of the photopolymer films of Examples and Comparative Examples using laser light having a wavelength of 660 nm, the recording efficiency was evaluated.

[0206] Specifically, the reflection spectrum of the recording layer of the photopolymer film is measured using an ultraviolet-visible spectrophotometer, and the wavelength (λ, nm) at which the reflection peak appears is determined to measure the recording efficiency.

[0207] [Table 3]

[0208]

[0209] According to Table 3, it is determined that in the embodiment, 0.010 μm is satisfied. -1 To 0.095μm -1 The maximum reduction rate of the band area forms an erosion layer of 20.0% to 70.0% relative to the coating (erosion layer + recording layer), has excellent adhesion, and is excellent in heat resistance and moisture resistance reliability and recording efficiency.

[0210] On the other hand, it was determined that in Comparative Example 1, almost no erosion layer was formed, and the adhesion and the reliability of heat resistance and moisture resistance were also poor; in Comparative Example 2, a thinner erosion layer of 13.4% compared with the coating layer was formed, and the adhesion and the reliability of heat resistance and moisture resistance were poor; and in Comparative Example 3, the erosion layer was formed too thickly with a thickness of 70.6% relative to the coating layer, and the recording efficiency was poor.

[0211] [Explanation of Reference Numerals]

[0212] 10: coating 20: recording layer

[0213] 30: Erosion layer

Claims

1. A photopolymer film comprising a base film and a recording layer, wherein a graph obtained from the results of photothermal infrared (PTIR) spectroscopy analysis in the thickness direction from one surface of the recording layer facing the base film satisfies the following formula 1, wherein the band area of ​​the carbonyl (C═O group) peak contained in the recording layer is plotted on the Y axis, and the distance in the thickness direction from one surface of the recording layer facing the base film is plotted on the X axis, [Formula 1] 0.010μm -1 ≦Maximum reduction rate of band area ≦0.095μm -1 In formula 1, The maximum reduction rate of the band area is the absolute value of the minimum value of the y value in the graph obtained by taking the first-order differentiation of the graph.

2. The photopolymer film according to claim 1, An etching layer is also included between the base film and the recording layer.

3. The photopolymer film according to claim 2, wherein: The photopolymer film comprises a coating layer, the coating layer comprising the erosion layer and the recording layer, and A thickness ratio of the erosion layer to the coating layer is 20.0% or more and 70.0% or less.

4. The photopolymer film according to claim 2, wherein: The thickness of the erosion layer is 1.0 μm or more and 10.0 μm or less.

5. The photopolymer film according to claim 1, wherein: The base film is a cellulose ester-based base film, a polyester-based base film, a poly(meth)acrylate-based base film, a polycarbonate-based base film, a cyclic olefin (COP)-based base film, or an acryl-based base film.

6. The photopolymer film of claim 1, wherein: The base film is a triacetyl cellulose (TAC) film.

7. The photopolymer film of claim 1, wherein: The recording layer includes a polymer matrix including a siloxane-based polymer, and a photoreactive monomer.

8. The photopolymer film according to claim 7, wherein: A weight ratio of the photoreactive monomer to the polymer matrix containing the siloxane-based polymer is 45:55 to 90:

10.

9. The photopolymer film of claim 2, wherein: The etching layer includes a photoreactive monomer.

10. A composition for forming a photopolymer film, comprising a coating solution comprising a polymer matrix containing a siloxane-based polymer or a precursor thereof, a photoreactive monomer, and an etching solvent, The etching solvent may be contained in an amount of 25 wt % or more and 70 wt % or less relative to 100 wt % of the coating solution.

11. The composition for forming a photopolymer film according to claim 10, wherein: The etching solvent is at least one selected from a ketone-based solvent, an ester-based solvent, a nitrogen-based compound solvent, a halogenated hydrocarbon-based solvent, and an aromatic hydrocarbon-based solvent.

12. A holographic recording medium comprising the photopolymer film according to claim 1.

13. An optical element comprising the photopolymer film according to claim 12.

Images