KR20240064974A - Hologram recording medium, preparation method thereof and optical element comprising the same - Google Patents

Abstract

The present invention relates to a hologram recording medium, a manufacturing method thereof, and an optical element containing the same. The holographic recording medium exhibits excellent stability over time at high temperatures before recording optical information, and exhibits the originally intended optical recording characteristics even when stored for a long time at room temperature or high temperature. It also has excellent physical properties such as diffraction efficiency, which are fundamentally required for holographic recording media. represents.

Description

Hologram recording medium, manufacturing method thereof, and optical element comprising the same {HOLOGRAM RECORDING MEDIUM, PREPARATION METHOD THEREOF AND OPTICAL ELEMENT COMPRISING THE SAME}

The present invention relates to a hologram recording medium, a manufacturing method thereof, and an optical element containing the same.

A hologram recording medium records information by changing the refractive index in the holographic recording layer through an exposure process, and reads the difference in the recorded refractive index to reproduce the information.

In this regard, photopolymer compositions can be used for hologram production. Photopolymers can easily store optical interference patterns as holograms by photopolymerization of photoreactive monomers. Therefore, photopolymers are used in smart devices such as mobile devices, parts of wearable displays, automotive products (e.g., head up display), holographic fingerprint recognition systems, optical lenses, mirrors, deflecting mirrors, filters, diffusion screens, diffraction members, and light guides. It can be used in a variety of fields, including holographic optical elements that function as a screen, waveguide, projection screen, and/or mask, media and light diffusion plates in optical memory systems, optical wavelength splitters, and reflective and transmissive color filters.

Specifically, the photopolymer composition for producing a hologram includes a polymer matrix, a photoreactive monomer, and a photoinitiator system. Then, laser interference light is irradiated to the photopolymer layer prepared from this composition to induce local photopolymerization of the monomer.

Through this local photopolymerization process, refractive index modulation occurs, and a diffraction grating is created through this refractive index modulation. The refractive index modulation value (△n) is affected by the thickness of the photopolymer layer and the diffraction efficiency (DE), and the angular selectivity becomes wider as the thickness becomes thinner.

Recently, there has been a growing demand for the development of materials that can maintain high diffraction efficiency and stable holograms, and various attempts have been made to manufacture hologram recording media that have a small thickness but have high diffraction efficiency and a high refractive index modulation value.

Meanwhile, the holographic recording medium needs to exhibit excellent stability over time even before recording optical information, thereby exhibiting the originally intended optical recording characteristics. However, holographic recording media have limitations in that they do not exhibit originally intended optical recording characteristics as the photoinitiator system reacts during storage.

According to one embodiment of the present invention, a hologram recording medium is provided.

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

According to another embodiment of the present invention, an optical element including the hologram recording medium is provided.

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

In this specification, “hologram recording medium” refers to a medium (medium) capable of recording optical information in the entire visible light range and ultraviolet range (e.g., 300 to 1,200 nm) through an exposure process, unless specifically stated otherwise. or media). Accordingly, the hologram recording medium of this specification may refer to a medium on which optical information is recorded, or may refer to a pre-recording medium capable of recording optical information. Holograms herein include in-line (Gabor) holograms, off-axis holograms, full-aperture holograms, white light transmission holograms (“rainbow holograms”), and Denisyuk. ) All visual holograms such as holograms, biaxial reflection holograms, edge-literature holograms, or holographic stereograms may be included.

According to one embodiment of the invention, a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol; and a photopolymer layer containing a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom, and the change in minimum transmittance calculated by the following equation 1 is 20% or less.

[Equation 1]

△T(%) = {(│T _{1 -} T ₀ │)/ T ₀ }

In Equation 1, T ₀ is 300 to 300 using a UV-Vis spectrometer for the sample on which the notch filter hologram was recorded after storing the hologram recording medium before recording in a dark room at a temperature of 20 to 25 ℃ and relative humidity of 40 to 50%. The lowest transmittance measured in the wavelength range of 1,200 nm,

T ₁ is the lowest transmittance measured as above for the sample on which the notch filter hologram was recorded after the hologram recording medium was stored for 100 hours in a dark room at a temperature of 60 ° C. and a relative humidity of 40 to 50% before recording.

Hereinafter, a hologram recording medium and a manufacturing method thereof according to an embodiment of the present invention, and an optical element including the hologram recording medium will be described in detail.

The hologram recording medium of one embodiment includes a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol; and a photopolymer layer containing a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom.

The photopolymer layer may be a photopolymer layer in a pre-recording state capable of recording optical information, or may be a photopolymer layer in a state in which optical information is recorded.

A photopolymer layer with optical information recorded can be manufactured by irradiating object light and reference light to the photopolymer layer before recording. When object light and reference light are irradiated to the photopolymer layer before recording, the photoinitiator system is in an inactive state in the destructive interference area due to the interference field of the object light and reference light, so photopolymerization of the photoreactive monomer does not occur, and the activated photoinitiator system does not occur in the constructive interference area. This causes photopolymerization of the photoreactive monomer. As the photoreactive monomer is continuously consumed in the constructive interference area, a concentration difference occurs between the photoreactive monomer in the destructive interference area and the constructive interference area. As a result, the photoreactive monomer in the destructive interference region diffuses into the constructive interference region. Since the photoreactive monomer and the photopolymer formed therefrom have a high refractive index compared to the polymer matrix, spatial changes in refractive index occur in the photopolymer layer, and a grid is created due to the spatial refractive index modulation occurring in the photopolymer layer. This grating surface serves as a reflective surface that reflects incident light by the difference in refractive index, and when light of the same wavelength is incident when recording in the direction of the reference light after recording the hologram, the Bragg condition is satisfied and the light diffracts in the direction of the original object light. Holographic optical information can be reproduced.

Therefore, if the photopolymer layer is in a state before recording, the photopolymer layer may include photoreactive monomers and a photoinitiator system in a randomly dispersed form within the polymer matrix.

On the other hand, if optical information is recorded in the photopolymer layer, the photopolymer layer may include a photopolymer distributed to form a polymer matrix and a lattice.

The change in minimum transmittance calculated by Equation 1 is an indicator for evaluating the temporal stability of the holographic recording medium before recording, especially at high temperature (60° C.). The holographic recording medium of the embodiment is left at high temperature for 100 hours before recording. Even so, the optical recording characteristics can be displayed at the originally intended level.

Specifically, the hologram recording medium of the embodiment has a change in minimum transmittance (△T) calculated by Equation 1 of 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less It may be less than or less than 1%. The lower limit of the change in minimum transmittance (ΔT) calculated using Equation 1 is not particularly limited and may be 0% or more.

The photopolymer layer includes a polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol; Photoreactive monomer; and a photoinitiator system.

The polymer matrix is formed by crosslinking a siloxane-based polymer containing a silane functional group (Si-H) and a (meth)acrylic-based polyol. Specifically, the polymer matrix is crosslinked (meth)acrylic polyol with a siloxane-based polymer containing a silane functional group. More specifically, the hydroxy group of the (meth)acrylic polyol can form a crosslink with the silane functional group of the siloxane-based polymer through a hydrosilylation reaction. The hydrosilylation reaction can proceed rapidly even at relatively low temperatures (for example, around 60°C) under a Pt-based catalyst. Therefore, the photopolymer layer can improve the manufacturing efficiency and productivity of the hologram recording medium by employing a polymer matrix that can be quickly crosslinked even at a relatively low temperature as a support.

The polymer matrix can increase the mobility of components (eg, photoreactive monomers or plasticizers) included in the photopolymer layer due to the flexible main chain of the siloxane-based polymer. In addition, siloxane bonding with excellent heat and moisture resistance properties can facilitate securing the reliability of the photopolymer layer on which optical information is recorded and the hologram recording medium containing the same.

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

The photopolymer layer includes a polymer matrix formed by cross-linking the siloxane-based polymer containing the above-described silane functional group and (meth)acrylic-based polyol, but may include a polymer matrix precursor that is not partially cross-linked. At this time, the polymer matrix precursor may mean a siloxane-based polymer, (meth)acrylic-based polyol, and Pt-based catalyst.

For example, the siloxane-based polymer may include a repeating unit represented by Formula 1 below and a terminal group represented by Formula 2 below.

[Formula 1]

In Formula 1,

A plurality of R ¹ and R ² are the same or different from each other and are each independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,

n is an integer from 1 to 10,000,

[Formula 2]

In Formula 2,

A plurality of R ¹¹ to R ¹³ are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,

At least one of R ¹ , R ² , and R ¹¹ to R ¹³ of at least one of the repeating units represented by Formula 1 and the terminal group represented by Formula 2 is hydrogen.

In Formula 2, -(O)- is bonded through oxygen (O) or directly without oxygen (O) when Si of the terminal group represented by Formula 2 is bonded to the repeating unit represented by Formula 1. It means to do.

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

As an example, R ¹ , R ² and R ¹¹ to R ¹³ in Formulas 1 and 2 may be methyl or hydrogen, and at least two of R ¹ , R ² and R ¹¹ to R ¹³ may be hydrogen. More specifically, the siloxane-based polymer includes compounds in which R ¹ and R ² of Formula 1 are methyl and hydrogen, respectively, and R ¹¹ to R ¹³ of Formula 2 are each independently methyl or hydrogen (for example, a terminal group is trimethyl polymethylhydrosiloxane, which is a silyl group or dimethylhydrosilyl group); Parts of R ¹ and R ² of Formula 1 are methyl and hydrogen, respectively, the remaining R ¹ and R ² are both methyl, and R ¹¹ to R ¹³ of Formula 2 are each independently methyl or hydrogen (e.g., a terminal compound poly(dimethylsiloxane-co-methylhydrosiloxane) wherein the group is a trimethylsilyl group or a dimethylhydrosilyl group, or R ¹ and R ² of the formula 1 are both methyl, and at least one of R ¹¹ to R ¹³ of the formula 2 is hydrogen; and the remainder are each independently methyl or hydrogen (for example, polydimethylsiloxane in which either or both of the terminal groups are dimethylhydrosilyl groups).

For example, the siloxane-based compound may have a number average molecular weight (Mn) in the range of 200 to 4,000. Specifically, the lower limit of the number average molecular weight of the siloxane-based polymer may be, for example, 200 or more, 250 or more, 300 or more, or 350 or more, and the upper limit may be, for example, 3,500 or less, 3,000 or less, 2,500 or less, 2,000 or less, It may be 1,500 or less or 1,000 or less. When the number average molecular weight of the siloxane-based polymer satisfies the above range, the siloxane-based polymer volatilizes during the crosslinking process with (meth)acrylic polyol at room temperature or higher, thereby lowering the degree of matrix crosslinking, or the siloxane-based polymer By preventing problems such as phase separation due to poor compatibility with components of other photopolymer layers, the hologram recording medium can exhibit excellent optical recording characteristics and thermal stability.

The number average molecular weight refers to the number average molecular weight (unit: g/mol) in terms of polystyrene measured by GPC method. In the process of measuring the number average molecular weight of polystyrene equivalent measured by the GPC method, commonly known analysis devices, detectors such as differential refractive index detectors, and analytical columns can be used, and the commonly applied temperature Conditions, solvent, and flow rate 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.

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

In this specification, “equivalent of a certain functional group” briefly refers to the number of g equivalents (equivalent weight, also called equivalent weight) expressed in units of g/equivalent, and refers to the molecular weight (weight average) of a molecule or polymer containing the functional group in question. It refers to the value divided by the number of functional groups (molecular weight, number average molecular weight, etc.). Therefore, the smaller the equivalent value, the higher the density of the functional group, and the larger the equivalent value, the smaller the density of the functional group.

When the silane functional group equivalent of the siloxane-based polymer satisfies the above range, the polymer matrix has an appropriate crosslinking density and sufficiently performs the role of a support, and the fluidity of the components included in the photopolymer layer is improved, so that the diffraction gratings generated after recording are improved. Even as time passes without the problem of the boundary collapsing, the initial refractive index modulation value is maintained at an excellent level, thereby minimizing the decrease in recording characteristics for optical information.

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, “(meth)acrylic (based)” refers to acrylic (based) and/or methacrylic (based), unless specifically stated otherwise, such as acrylic (based), methacrylic (based), or It is a term that encompasses both acrylic (based) and methacrylic (based) mixture.

The (meth)acrylic polyol is 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 (meth)acrylate monomer having a hydroxy group. It may be a copolymer of a monomer and a (meth)acrylate-based monomer that does not have a hydroxy group. In this specification, “copolymer” is a term that encompasses random copolymers, block copolymers, and graft copolymers, unless otherwise specified.

Examples of the (meth)acrylate-based monomer having the hydroxy group include hydroxyalkyl (meth)acrylate or hydroxyaryl (meth)acrylate, and the alkyl is an alkyl having 1 to 30 carbon atoms. , and the aryl may be an aryl having 6 to 30 carbon atoms. In addition, examples of the (meth)acrylate-based monomer that does not have the hydroxy group include alkyl (meth)acrylate-based monomers or aryl (meth)acrylate-based monomers, and the alkyl has 1 to 1 carbon atoms. It is an alkyl of 30, and the aryl may be an aryl of 6 to 30 carbon atoms.

For example, the (meth)acrylic polyol may have a weight average molecular weight (Mw) in the range of 150,000 to 1,000,000. The weight average molecular weight means the weight average molecular weight in terms of polystyrene measured by the GPC method as described above. For example, the lower limit of the weight average molecular weight may be 150,000 or more, 200,000 or more, or 250,000 or more, and the upper limit may be, for example, 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, 650,000 or less, Below, It can be less than 550,000, less than 500,000, or less than 450,000. When the weight average molecular weight of the (meth)acrylic polyol satisfies the above range, the polymer matrix sufficiently functions as a support, so there is little decrease in the recording characteristics of optical information even with the passage of time, and sufficient flexibility is provided to the polymer matrix. As a result, the mobility of components (eg, photoreactive monomers or plasticizers, etc.) included in the photopolymer layer can be improved to minimize the decrease in recording characteristics of optical information.

In order to adjust the crosslinking density of the (meth)acrylic polyol by the siloxane-based polymer to a level advantageous for securing the function of a hologram recording medium, the hydroxyl equivalent weight of the (meth)acrylic polyol may be adjusted to an appropriate level.

Specifically, the hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol may be, for example, in the range of 500 to 3,000 g/equivalent. More specifically, the lower limit of the hydroxyl (-OH) equivalent weight of the (meth)acrylic polyol is 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. It may be more than g/equivalent, more than 1200 g/equivalent, more than 1300 g/equivalent, more than 1400 g/equivalent, more than 1500 g/equivalent, more than 1600 g/equivalent, more than 1700 g/equivalent, or more than 1750 g/equivalent. And, the upper limit of the hydroxyl group (-OH) equivalent weight of the (meth)acrylic polyol is 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/ It may be 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.

When the hydroxyl (-OH) equivalent of the (meth)acrylic polyol satisfies the above range, the polymer matrix has an appropriate crosslinking density and sufficiently performs the role of a support, and the fluidity of the components included in the photopolymer layer is improved, so that the polymer matrix can be used after recording. The initial refractive index modulation value can be maintained at an excellent level even as time passes without the problem of the interface between the generated diffraction gratings collapsing, thereby minimizing the decrease in recording characteristics for optical information.

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

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, It may be 1.47 or less, 1.46 or less, or 1.45 or less. When the (meth)acrylic polyol has a refractive index in the above-mentioned range, it can contribute to increasing the refractive index modulation. The refractive index of the (meth)acrylic polyol is a theoretical refractive index, using the refractive index of the monomer used to produce (meth)acrylic polyol (value measured using an Abbe refractometer at 25 ℃) and the fraction (molar ratio) of each monomer. It can be calculated as:

The (meth)acrylic polyol and the siloxane polymer are included so that the molar ratio (SiH/OH) of the silane functional group (Si-H) of the siloxane polymer to the hydroxyl group (-OH) of the (meth)acrylic polyol is 1.5 to 4. You can.

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

Specifically, the silane functional group equivalent of the siloxane-based polymer is the molecular weight (e.g., number average molecular weight) of the siloxane-based polymer divided by the number of silane functional groups per molecule, and the hydroxyl equivalent of the (meth)acrylic polyol is the (meth) It is a value obtained by dividing the molecular weight (e.g., weight average molecular weight) of the acrylic polyol by the number of hydroxy functional groups per molecule. Therefore, the number of moles of silane functional groups can be confirmed by dividing the weight of the siloxane-based polymer by the equivalent weight of the silane functional group of the siloxane-based polymer, and by dividing the weight of the (meth)acrylic polyol by the equivalent weight of the hydroxyl group of the (meth)acrylic polyol, the number of moles of hydroxy groups can be determined. You can check it. More specifically, taking Example 1 described below as an example, dividing the weight (2.6 g) of the siloxane-based polymer used in Example 1 by the silane functional group equivalent of the siloxane-based polymer used in Example 1 (103 g/equivanlent) The number of moles of the silane functional group (0.0252 mol) is calculated, and the weight (22.4 g) of the (meth)acrylic polyol used in Example 1 is calculated as the hydroxyl equivalent of the (meth)acrylic polyol used in Example 1 (1802 g/equivanlent). ) to calculate the number of moles of hydroxyl group (0.0124 mol). By dividing the calculated number of moles of silane functional group (0.0252 mol) by the number of moles of hydroxy group (0.0124 mol), it is confirmed that the SiH/OH molar ratio is calculated as 2.

The lower limit of the SiH/OH molar ratio may be, for example, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, or 2.0 or more, and the upper limit may be, for example, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, or 3.5 or less. You can. When the above SiH/OH molar ratio range is satisfied, the polymer matrix is crosslinked at an appropriate crosslinking density to improve the fluidity of recording components (e.g., photoreactive monomers and plasticizers, etc.) to ensure excellent optical recording characteristics, Even if placed in a high temperature and/or high humidity environment before and after recording, the components in the photopolymer layer can be prevented from moving or deforming or moisture from penetrating into the photopolymer layer, thereby showing excellent heat resistance or moisture heat resistance.

The Pt-based catalyst may be, for example, Karstedt's catalyst. The Pt-based catalyst may be included in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the (meth)acrylic polyol. Specifically, the Pt-based catalyst is, for example, 0.02 part by weight, 0.03 part by weight, 0.04 part by weight, 0.05 part by weight, or 0.06 part by weight, based on 100 parts by weight of the (meth)acrylic polyol, It may be included in 1.5 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, 0.15 parts by weight or less, 0.14 parts by weight or less, 0.13 parts by weight or less, or 0.12 parts by weight or less. When the Pt-based catalyst is used in the above-mentioned amount, the polymer matrix can be crosslinked at an appropriate crosslinking density to exhibit desired optical recording characteristics.

The polymer matrix precursor may, if necessary, be a Rhodium-based, Iridium-based, Rhenium-based, Molybdenum-based, Iron-based, Nickel-based, alkali metal or alkaline earth metal-based, Lewis acids-based or Carbene-based non-metallic catalyst in addition to the Pt-based catalyst. etc. may be additionally included.

Meanwhile, optical information can be recorded in the hologram recording medium of one embodiment by irradiating object light and reference light to the photopolymer layer. Due to the interference field between the object light and the reference light, photopolymerization of the photoreactive monomer does not occur in the destructive interference area, but photopolymerization of the photoreactive monomer occurs in the constructive interference area. As the photoreactive monomer is continuously consumed in the constructive interference area, a concentration difference occurs between the photoreactive monomers in the destructive interference area and the constructive interference area, and as a result, the photoreactive monomer in the destructive interference area diffuses into the constructive interference area. A diffraction grating is created by the refractive index modulation that occurs in this way.

Accordingly, the photoreactive monomer may include a compound having a higher refractive index than the polymer matrix in order to implement the above-described refractive index modulation. However, all photoreactive monomers are not limited to having 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 so that a high refractive index modulation value can be realized. As an example, the photoreactive monomer may include a monomer with a refractive index of 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or 1.60 or more and 1.70 or less. there is.

The photoreactive monomer may include one or more monomers selected from the group consisting of monofunctional monomers having one photoreactive functional group and polyfunctional monomers having two or more photoreactive functional groups. At this time, 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.

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

The multifunctional monomer is, for example, bisphenol A (ethylene oxide) _2-10 di(meth)acrylate (bisphenol A (EO) _2-10 (meth)acrylate; Miwon's M240 refractive index 1.537, M241 refractive index 1.529, M244 refractive index 1.545, M245 refractive index 1.537, M249 refractive index 1.542, M2100 refractive index 1.516, M2101 refractive index 1.512), Bisphenol A epoxy di(meth)acrylate (Miwon's PE210 refractive index 1.557, PE2120A refractive index 1.5 33, PE2120B refractive index 1.534, PE2020C refractive index 1.539, PE2120S refractive index 1.556), bisfluorene di(meth)acrylate (Miwon's HR6022 refractive index 1.600, HR6040 refractive index 1.600, HR6042 refractive index 1.600), modified bisphenol fluorene di(meth)acrylate (Miwon's HR 6060 refractive index 1.584) , HR6100 refractive index 1.562, HR6200 refractive index 1.530), tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate (Miwon's M370 refractive index 1.508), phenol novolak epoxy (meth)acrylate (Miwon's) It may include one or more selected from the group consisting of SC6300 refractive index 1.525) and cresol novolak epoxy (meth)acrylate (Miwon's SC6400 refractive index 1.522, SC6400C refractive index 1.522).

The photopolymer layer may include 50 to 300 parts by weight of a photoreactive monomer based on 100 parts by weight of the polymer matrix. For example, the lower limit of the content of the photoreactive monomer may be 50 parts by weight or more, 70 parts by weight or more, 100 parts by weight or more, or 120 parts by weight or more, and the upper limit is 300 parts by weight or less, 270 parts by weight or less, and 250 parts by weight or less. It may be less than or equal to 220 parts by weight. At this time, the content of the polymer matrix, which is the standard, means the content (weight) of the (meth)acrylic polyol and siloxane-based polymer forming the matrix. When the above range is satisfied, excellent optical recording characteristics can be exhibited.

The photopolymer layer may further include a plasticizer. When a plasticizer is added to the photopolymer layer, refractive index modulation can be more easily implemented when recording a hologram. More specifically, the plasticizer improves the fluidity of the photoreactive monomer by lowering the glass transition temperature of the polymer matrix, and has a low refractive index and non-reactive properties, so it is uniformly distributed within the polymer matrix and then moves when the unphotoreactive monomer moves. It can contribute to refractive index modulation by moving in the opposite direction. Additionally, plasticizers can contribute to improving the moldability of photopolymer compositions.

The photopolymer layer may contain a fluorine-based compound as a plasticizer.

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

The fluorine-based compound may include, for example, one or more functional groups selected from the group consisting of an ether group, an ester group, and an amide group, and two or more difluoromethylene groups. More specifically, the fluorine-based compound may be, for example, a compound containing a repeating unit represented by the following formula (3).

[Formula 3]

In Formula 3 above,

A plurality of R ³¹ to R ³⁴ are each independently hydrogen or fluorine, at least one of R ³¹ to R ³⁴ is fluorine, and m is an integer of 2 to 12.

More specifically, the fluorine-based compound may be a compound containing 1 to 3 units represented by the following Chemical Formula 3-1.

[Formula 3-1]

In Formula 3-1,

R ⁴¹ to R ⁴⁴ and R ⁵³ to R ⁵⁶ are each independently hydrogen or fluorine, and R ⁴⁵ to R ⁵² are fluorine.

For example, in Formula 3-1, R ⁴¹ , R ⁴² , R ⁵⁵ and R ⁵⁶ are hydrogen, and R ⁴³ to R ⁵⁴ are fluorine.

Fluorine-based compounds containing (repeating) units represented by Formulas 3 and 3-1 are not particularly limited, but may be capped with an end capping agent widely used in the related technical field. As an example, the terminal of the fluorine-based compound containing the (repeating) unit represented by Formulas 3 and 3-1 may be an alkyl group or an alkyl group substituted with one or more alkoxy. As a non-limiting example, using 2-methoxyethoxymethyl chloride as an end capping agent, the terminal of the fluorine-based compound containing the (repeating) unit represented by Formulas 3 and 3-1 is a 2-methoxyethoxymethyl group. You can.

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

The photopolymer layer may include 20 to 200 parts by weight of the fluorine-based compound based on 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the fluorine-based compound may be, for example, 25 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, or 80 parts by weight or more. , the upper limit may be, for example, 190 parts by weight or less, 180 parts by weight or less, 170 parts by weight or less, 160 parts by weight or less, or 150 parts by weight or less. When the above range is satisfied, the fluorine-based compound has a sufficiently low refractive index without problems such as poor compatibility with the components included in the photopolymer layer, causing some fluorine-based compounds to elute to the surface of the photopolymer layer or worsen haze after recording. It can exhibit a large refractive index modulation value, which is advantageous in securing excellent optical recording characteristics.

When the photopolymer layer contains a fluorine-based compound and the elemental composition measured on the surface of the photopolymer layer satisfies a certain ratio, it can exhibit excellent optical recording characteristics and excellent stability over time even at high temperatures.

Specifically, using photoelectron spectroscopy, called X-ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA), the element ratio on the surface of the photopolymer layer can be confirmed. According to the photoelectron spectroscopy method described in the test example described later, the elements found on the surface of the sample to be analyzed can be qualitatively analyzed through a survey scan, and then the element ratio can be measured by performing a narrow scan for each element found. The element ratio of the photopolymer layer in the present specification may be understood as the element ratio of the photopolymer layer before recording or the element ratio of the photopolymer layer after recording. The element ratio of the photopolymer layer before recording and the element ratio of the photopolymer layer after recording may be the same within an experimental error range, but may differ from each other in some embodiments. That is, even if the element ratio before recording and the element ratio after recording of the photopolymer layer are different from each other beyond the error range, the desired effect of the hologram recording medium of one embodiment can be achieved if the element ratio before or after recording is within the above-mentioned range. there is.

The carbon element ratio on the surface of the photopolymer layer included in the hologram recording medium of one embodiment is 50 atomic% or more, 51 atomic% or more, 52 atomic% or more, 53 atomic% or more, or 54 atomic% or more, and 70 atomic% or less, It may be 69 atomic% or less or 68 atomic% or less.

The nitrogen element ratio on the surface of the photopolymer layer is 0.01 atomic % or more, 0.05 atomic % or more, 0.10 atomic % or more, or 0.20 atomic % or more, and 2 atomic % or less, 1.8 atomic % or less, 1.6 atomic % or less, 1.4 atomic % or less. Or it may be 1.2 atomic% or less.

The oxygen element ratio on the surface of the photopolymer layer is 15 atomic% or more, 16 atomic% or more, or 17 atomic% or more, and 30 atomic% or less, 29 atomic% or less, 28 atomic% or less, 27 atomic% or less, or 26 atomic% or less. You can.

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

The silicon element ratio on the surface of the photopolymer layer may be 3 atomic% or more, 4 atomic% or more, 4.5 atomic% or more, and 15 atomic% or less.

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

As the photopolymer layer exhibits the above-described elemental composition ratio, it can exhibit excellent optical recording properties and excellent stability over time at high temperatures. In particular, if the fluorine element ratio is less than the above range, the optical recording characteristics may deteriorate, and if the fluorine element ratio exceeds the above range, there may be a problem of deterioration of stability over time due to vulnerability to moisture. In addition, if the silicon element ratio is less than the above range, there may be a problem of vulnerability to heat and increased haze, and if the silicon element ratio exceeds the above range, there may be a problem that optical recording characteristics are greatly reduced.

Most of the components of the photopolymer layer can be said to be a polymer matrix, a photoreactive monomer, and a fluorine-based compound that is a plasticizer added as needed. Therefore, the elemental composition of the surface of the photopolymer layer can be controlled through the mixing ratio of the polymer matrix, photoreactive monomer, and fluorine-based compound. In order to satisfy the above-described elemental composition, the photopolymer layer contains 17 to 38% by weight of the polymer matrix, 33 to 58% by weight of the photoreactive monomer, and a fluorine-based compound, based on the total weight of the polymer matrix, photoreactive monomer, and fluorine-based compound. It may contain 17 to 38 weight%.

More specifically, the polymer matrix may include, for example, 17 wt% or more, 18 wt% or more, 19 wt% or more, or 20 wt% or more and 38 wt% or less, 37 wt% or less, or 36 wt% or less. there is. For example, the photoreactive monomer may be included in 33 wt% or more, 35 wt% or more, or 38 wt% or more and 58 wt% or less, 55 wt% or less, or 53 wt% or less. For example, the fluorine-based compound may be included in an amount of 17 wt% or more, 18 wt% or more, 19 wt% or more, or 20 wt% or more and 38 wt% or less, 35 wt% or less, 33 wt% or less, or 32 wt% or less. You can. Within this range, it is possible to provide a photopolymer layer that satisfies the above-described elemental composition ratio.

The photopolymer layer includes a photoinitiator system. The photoinitiator system may refer to a combination of a photoinitiator or a photosensitizer and a coinitiator that allows polymerization to be initiated by light.

The photopolymer layer may include a photosensitizer and a coinitiator as a photoinitiator system.

As the photosensitizer, for example, a photosensitivity dye may be used. Specifically, the photosensitive dyes include, for example, silicon rhodamine compounds, sulfonium derivatives of ceramidonin, new methylene blue, thioerythrosine triethylammonium, 6-acetylamino-2-methylceramidonin, eosin, erythrosine, rose bengal, thionine, basic yellow ), Pinacyanol chloride, rhodamine 6G, gallocyanine, ethyl violet, Victoria blue R, Celestine blue, Quinaldine Red, crystal violet, brilliant green, Astrazon orange G, darrow red, pyronin Y, basic red 29 (basic red 29), pyrylium iodide, Safranin O, cyanine, methylene blue, Azure A and BODIPY. You can use it.

As an example, a silicon rhodamine compound represented by the following formula (4) may be used as the photosensitive dye.

[Formula 4]

In Formula 4 above,

R ²¹ to R ²⁹ are each independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or It is a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms,

d and e are each independently integers from 0 to 3,

f is an integer from 0 to 5,

An ^- is an anion.

In the above, “substituted or unsubstituted” means that hydrogen or carbon is substituted with another element. Hydrogen may be substituted with a halogen, a hydroxy group, an alkyl group with 1 to 10 carbon atoms, or an alkoxy group with 1 to 10 carbon atoms, and carbon (- CH ₂ -) may be substituted with -O- or -CO-.

In Formula 4, R ²¹ to R ²⁸ may each independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Specifically, in Formula 4, R ²¹ to R ²⁸ may each independently be an alkyl group having 1 to 6 carbon atoms. More specifically, in Formula 4, R ²¹ to R ²⁸ may be a methyl group.

In Formula 4, d and e may each independently be an integer of 0 to 2, an integer of 0 to 1, or 0.

In Formula 4, f may be an integer of 0 to 5, an integer of 0 to 4, an integer of 0 to 3, an integer of 0 to 2, or an integer of 1 to 2.

In Formula 4, R ²⁹ may be a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. Specifically, in Formula 4, R ²⁹ may be an alkoxy group having 1 to 6 carbon atoms. More specifically, in Formula 4, R ²⁹ may be a methoxy group.

In Formula 4, the anion (An ^- ) is a halide anion, a cyano anion, a sulfonate anion, an alkoxy anion having 1 to 30 carbon atoms, a substituted or unsubstituted alkyl sulfonate anion having 1 to 30 carbon atoms, or a substituted or unsubstituted carbon number. It may be an aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic borate anion having 6 to 30 carbon atoms.

Specifically, in Formula 4, the anion (An ^- ) is a substituted or unsubstituted alkyl sulfonate anion having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic sulfonate anion having 6 to 30 carbon atoms, or a substituted or unsubstituted carbon number. It may be 6 to 30 aromatic borate anions.

또는 테트라페닐보레이트 음이온일 수 있다. More specifically, in Formula 4, the anion (An ^- ) is an alkyl sulfonate anion having 2 to 15 carbon atoms in which at least one hydrogen is substituted or unsubstituted with fluorine, and at least one carbon is substituted or unsubstituted with -O- or -CO-. It may be a ringed alkyl sulfonate anion having 6 to 30 carbon atoms, a methyl-substituted or unsubstituted phenyl sulfonate anion, or a substituted or unsubstituted tetraaryl borate anion. For example, in Formula 4, the anion (An ^- ) is a dodecyl sulfonate anion, a perfluorobutyl sulfonate anion, a phenyl sulfonate anion, a methylphenyl sulfonate anion,

Or it may be a tetraphenylborate anion.

The photopolymer layer may include the photosensitive dye in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the photosensitive dye may be, for example, 0.02 parts by weight or more, 0.03 parts by weight or more, or 0.05 parts by weight or more, and the upper limit may be, for example, 5 parts by weight or less. When the above range is satisfied, it is advantageous to secure the desired optical recording characteristics by showing an appropriate polymerization reaction rate.

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

As an example, the photopolymer layer may include an electron donor as a coinitiator. In particular, the photopolymer layer uses the above-described photosensitive dye as an electron donor and a material exhibiting a specific reaction energy to enable the hologram recording medium of one embodiment to have excellent stability over time.

Specifically, the electron donor participates in the photopolymerization initiation reaction by reacting with the photosensitive dye excited to a triplet state by light irradiation as shown in Scheme 1 below.

[Scheme 1]

At this time, if an electron donor with a reaction energy of -25 to 0 kJ/mol with a photosensitive dye excited in a triplet state is used, the reaction does not start even at room temperature or high temperature before light irradiation, showing excellent stability over time and when light is irradiated. A sensitive photo-initiated reaction occurs, resulting in excellent optical recording properties.

More specifically, the electron donor has a reaction energy with a photosensitive dye excited in a triplet state of -25 kJ/mol or more, -20 kJ/mol or more, -15 kJ/mol or more, -14 kJ/mol or more, - 13 kJ/mol or more, - 12 kJ/mol or more, - 11 kJ/mol or more, - 10 kJ/mol or more, - 9 kJ/mol or more, or - 8.5 kJ/mol or more and 0 kJ/mol or less, - 3 kJ/mol or less or -5 kJ/mol or less can be used. For the method of measuring the reaction energy, refer to the measurement method described in detail in the test example described later.

The photopolymer layer may further include an electron acceptor as needed along with an electron donor, as will be described later. The electron acceptor receives electrons during the redox reaction of the photoinitiator system, and when an electron acceptor is included, the total energy E2 of the photoinitiator system reaction increases toward a negative value. However, as a result of the present inventors' research, even if the total energy of the photoinitiator system reaction changes due to the inclusion of the electron acceptor, excellent stability over time can be secured only when the reaction energy of the photosensitive dye and the electron donor is within the above-mentioned range.

The electron donor may include, for example, a borate anion represented by the following formula (5).

[Formula 5]

^{BX 1 ​ ​}

In Formula ⁵ , X ¹ to arylalkyl) group, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, but at least one of X ¹ to X ⁴ is not an aryl group.

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

Specifically, X ^{1 to} X ⁴ may be a straight-chain alkyl group having 1 to 12 carbon atoms.

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

For example, the alkali metal cation may be one or more selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium.

The quaternary ammonium cation may be an ammonium cation in which nitrogen (N) is substituted with four substituents, a cyclic ammonium cation in which two substituents substituted for nitrogen are connected to each other, or a mixture thereof.

The nitrogen-containing heterocyclic cation may be a heteroaromatic ring cation containing one or more nitrogen. Examples of such heteroaromatic ring cations include cations of pyrrole, pyrazole, imidazole, or pyridine, and the hydrogen thereof may be substituted or unsubstituted.

For example, when using the above-described silicon rhodamine compound as a photosensitive dye, the electron donor may include at least one selected from the group consisting of borate anions represented by the following formulas 5-1 and 5-2. . The combination of this photosensitive dye and borate anion exhibits a reaction energy in the above-mentioned range, ensuring excellent stability over time, and at the same time exhibiting excellent sensitivity, improving the diffraction efficiency, refractive index modulation value, image reproducibility, and angle selectivity, which are all properties of the holographic recording medium. It can display excellent characteristics.

[Formula 5-1]

In Formula 5-1,

R ¹⁰² is each independently methyl or halogen,

R ¹⁰³ is each independently hydrogen, methyl or halogen, but when the adjacent R ¹⁰² is methyl, it is halogen,

X ^4' is a straight-chain alkyl group having 1 to 12 carbon atoms.

[Formula 5-2]

In Formula 5-2,

R ¹⁰⁶ is each independently hydrogen, methyl or halogen,

X ^4" is a straight-chain alkyl group having 1 to 12 carbon atoms.

In Formula 5-2, R ¹⁰⁶ is each independently hydrogen, methyl, or halogen, and at least one of them may be halogen.

In Formulas 5-1 and 5-2, halogen may be fluorine or chlorine. Among these, when the halogen is chlorine, it has superior heat resistance and can ensure excellent stability over time not only at room temperature but also at high temperatures.

In addition, when using the above-described silicon rhodamine compound as the photosensitive dye, the cation combined with the borate anion includes a cation (quaternary ammonium cation) represented by the following formula 5-3 and a cation represented by the following formula 5-4 It may include one or more species selected from the group consisting of (nitrogen-containing heterocyclic cations). The combination of this photosensitive dye with borate anions and cations exhibits reaction energy in the above-mentioned range, ensuring excellent stability over time and at the same time exhibiting excellent sensitivity, which is essential for diffraction efficiency, refractive index modulation value, image reproducibility, and angle selectivity, which are all physical properties of holographic recording media. These can show excellent characteristics.

[Formula 5-3]

NY ¹ Y ² Y ³ Y ⁴

In Formula 5-3, two substituents of Y ¹ to Y ⁴ may or may not be connected to each other to form an aliphatic ring having 4 to 10 carbon atoms,

Y ¹ to Y ⁴ that do not form an aliphatic ring are each independently an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an alkyl group with 2 to 40 carbon atoms linked through an ester bond. (For example, -CH ₂ CH ₂ -O-CO-CH ₂ CH ₂ CH ₃ , etc.),

It is excluded that Y ¹ to Y ⁴ are all methyl groups or that two or more substituents are alkyl groups having 16 or more carbon atoms.

In the above formula 5-3, when Y ¹ to Y ⁴ are all methyl groups, or when two or more substituents are alkyl groups having 16 or more carbon atoms, the electron donor may not dissolve well in the photopolymer composition and may not exhibit the desired optical recording characteristics.

Specifically, two of the substituents Y ¹ to Y ⁴ may be connected to each other to form piperidine or pyrrolidine.

Among Y ¹ to Y ⁴ , the substituents that do not form an aliphatic ring may each independently be a straight-chain alkyl group having 1 to 32 carbon atoms, a phenyl group, a benzyl group, or -CH ₂ CH ₂ -O-CO-CH ₂ CH ₂ CH ₃ . More specifically, the substituents that do not form an aliphatic ring among Y ¹ to Y ⁴ may each independently be a methyl group, butyl group, hexadecyl group, hentriacontyl group, phenyl group, or benzyl group.

[Formula 5-4]

In Formula 5-4, R ¹⁰⁷ , R ¹⁰⁹ and R ¹¹⁰ are each independently hydrogen, an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an ester bond. It is an alkyl group having 2 to 40 carbon atoms (for example, -CH ₂ CH ₂ -O-CO-CH ₂ CH ₂ CH ₃ , etc.),

R ¹⁰⁸ and R ¹¹¹ are each independently an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an alkyl group with 2 to 40 carbon atoms linked through an ester bond (for example, -CH ₂ CH ₂ -O-CO-CH ₂ CH ₂ CH ₃ etc.).

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

Specifically, R ¹⁰⁸ and R ¹¹¹ may be a straight-chain alkyl group having 1 to 40 carbon atoms or an arylalkyl group having 6 to 40 carbon atoms. More specifically, R ¹⁰⁸ and R ¹¹¹ may be a hexadecyl group or a benzyl group.

The cation bound to the borate anion is a cation represented by the formulas 5-3 and 5-4, for example, tetrabutyl ammonium cation, hexadecyl dimethyl benzyl ammonium cation, hentriacontyl dimethyl benzyl ammonium cation, hexadecyl dimethyl benzyl ammonium cation, Decyl benzyl piperidinium cation, hexadecyl benzyl pyrrolidinium cation, 1-hexadecyl-3-benzylimidazolium cation and 1,3-dihexadecyl-2-phenylimida. It may include one or more species selected from the group consisting of zolium cations.

However, the cations combined with the borate anion are not limited to the above-mentioned cations, and even if they show poor solubility when included alone, if they can show appropriate solubility when mixed with the above-mentioned cations, some of the above-mentioned cations may be used according to the related art. Other cations known in the art may be substituted. As a non-limiting example, some of the above-mentioned cations may be substituted with 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium, etc.

As an example, the photopolymer layer may include an electron acceptor as a coinitiator. The electron acceptor includes, for example, onium salts such as sulfonium salts and iodonium salts; triazine compounds such as tris(trihalomethyl)triazine, substituted bis(trihalomethyl)triazine, etc.; Or it may include a mixture thereof.

Specifically, the electron acceptor includes (4-(octyloxy)phenyl)(phenyl)iodonium salt as an iodonium salt, or 2-(4-methoxyphenyl)-4,6-bis as a triazine compound. It may include (trichloromethyl)-1,3,5-triazine. Examples of the electron acceptor include commercially available H-Nu 254 (Spectra) or 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3, 5-Triazine (TCI) can be used.

Among these, a triazine compound can be used as the electron acceptor. When a triazine compound is used as an electron acceptor, the stability over time at high temperatures of the hologram recording medium before recording can be further improved.

The photopolymer layer may include the co-initiator in the range of 0.05 to 10 parts by weight based on 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the disclosure agent may be, for example, 0.1 part by weight or more, 0.5 part by weight or more, 1 part by weight or more, 1.5 part by weight or more, or 2 parts by weight or more, and the upper limit is, for example, 5 parts by weight. It may be less than 100%. When the above range is satisfied, it is advantageous to secure the desired optical recording characteristics by showing an appropriate polymerization reaction rate.

The photoinitiator system may include an additional photoinitiator to remove the color of the photosensitive dye and react all unreacted photoreactive monomers after irradiation with light for recording. Examples of the photoinitiator include imidazole derivatives, bisimidazole derivatives, N-aryl glycine derivatives, organic azide compounds, titanocene, aluminate complexes, organic peroxides, N-alkoxy pyridinium salts, and thioxanthone derivatives. , amine derivatives, diazonium salt, sulfonium salt, iodonium salt, sulfonic acid ester, imide sulfonate, dialkyl-4-hydroxy sulfonium salt, aryl sulfonic acid- p-nitro benzyl ester, silanol-aluminum complex, (η6-benzene) (η5-cyclopentadienyl)iron(II), benzoin tosylate, 2,5-dinitro benzyl tosylate, N-tosylphthalate or mixtures thereof may be used. More specifically, the photoinitiator includes 1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4''-tetrakis(t-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercapto benzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (Product name: 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), 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 P-115 (Manufacturer: SK entis), Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990 (manufacturer: Dow Chemical Co. in USA), Irgacure 264, Irgacure 250 (manufacturer: BASF), CIT-1682 (manufacturer: Nippon Soda) or mixtures thereof, etc. Examples include, but are not limited to these.

The photopolymer layer may include the photoinitiator in the range of 0.05 to 10 parts by weight based on 100 parts by weight of the polymer matrix. Specifically, the lower limit of the content of the photoinitiator may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more, and the upper limit is, for example, 5 parts by weight. It may be below. When the above range is satisfied, a transparent hologram recording medium can be provided by recording optical information on the photopolymer layer, effectively terminating the reaction of the photoreactive monomer, and discoloring the photosensitive dye.

The photopolymer layer may further include additives such as surfactants or antifoaming agents.

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

The silicone-based surfactant includes, for example, BYK-077, BYK-085, BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-320 manufactured by BYK Chemie, BYK-322, BYK-323, BYK-325, BYK-330, BYK-331, BYK-333, BYK-335, BYK-341v344, BYK-345v346, BYK-348, BYK-354, BYK355, BYK-356, BYK-358, BYK-361, BYK-370, BYK-371, BYK-375, BYK-380, BYK-390, BYK-3550, etc. are available. The fluorine-based surfactant includes F-114, F-177, F-410, F-411, F-450, F-493, F-494, F-443, F-444 manufactured by DIC (DaiNippon Ink & Chemicals). F-445, F-446, F-470, F-471, F-472SF, F-474, F-475, F-477, F-478, F-479, F-480SF, F-482, F- 483, F-484, F-486, F-487, F-172D, MCF-350SF, TF-1025SF, TF-1117SF, TF-1026SF, TF-1128, TF-1127, TF1129, TF-1126, TF- 1130, TF-1116SF, TF-1131, TF1132, TF1027SF, TF-1441, TF-1442, etc. are available.

If the photopolymer layer includes a surfactant, the surfactant may be used in an amount of 0.01 parts by weight or more, 0.02 parts by weight, 0.03 parts by weight or more, or 0.05 parts by weight or more and 5 parts by weight or less or 3 parts by weight, based on 100 parts by weight of the polymer matrix. It may include the following. When the above range is satisfied, excellent optical recording properties can be preserved by providing excellent adhesiveness and release properties to the photopolymer layer.

The photopolymer layer may include a silicone-based reactive additive as an antifoaming agent. As the silicone-based reactive additive, for example, commercial products such as Tego Rad 2500 can be used. The content of the antifoaming agent can be appropriately adjusted to a level that does not interfere with the function of the hologram recording medium.

The photopolymer layer may be formed from a photopolymer composition containing a solvent.

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

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

The photopolymer composition may include a solvent so that the solid content concentration is 1 to 90% by weight. Specifically, the photopolymer composition may contain a solvent so that the solid concentration is 20% by weight or more, 25% by weight or more, or 30% by weight or less, and 50% by weight or less, 45% by weight or less, or 40% by weight or less. . Within this range, the photopolymer composition exhibits appropriate flowability and can form a coating film without defects such as streaks, and no defects occur during the drying and curing process, allowing the formation of a photopolymer layer exhibiting desired physical and surface properties. there is.

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

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

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

The hologram recording medium of the above embodiment may have high diffraction efficiency. As an example, the hologram recording medium may have a diffraction efficiency of 80% or more when recording a notch filter hologram. At this time, the thickness of the photopolymer layer may be, for example, 5 to 30 ㎛. Specifically, the diffraction efficiency when recording the notch filter hologram is 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, It may be at least 94%, at least 95%, at least 96%, at least 97%, or at least 98%. As such, the hologram recording medium of the embodiment can achieve excellent diffraction efficiency even if it includes a thin photopolymer layer. The diffraction efficiency can be measured by the method described in the test example described later.

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

Meanwhile, according to another embodiment of the invention, a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol; Photoreactive monomer; and applying and drying a photopolymer composition containing a photoinitiator system to form a photopolymer layer, thereby manufacturing a hologram recording medium before recording with a change in minimum transmittance of 20% or less as calculated by Equation 1 below; and recording optical information by selectively polymerizing photoreactive monomers included in the photopolymer layer by irradiating a coherent laser to a predetermined area of the photopolymer layer.

[Equation 1]

△T(%) = {(│T _{1 -} T ₀ │)/ T ₀ }

In Equation 1, T ₀ is 300 to 300 using a UV-Vis spectrometer for the sample on which the notch filter hologram was recorded after storing the hologram recording medium before recording in a dark room at a temperature of 20 to 25 ℃ and relative humidity of 40 to 50%. The lowest transmittance measured in the wavelength range of 1,200 nm,

T ₁ is the lowest transmittance measured as above for the sample on which the notch filter hologram was recorded after the hologram recording medium was stored for 100 hours in a dark room at a temperature of 60 ° C. and a relative humidity of 40 to 50% before recording.

Since the hologram recording medium and the photopolymer layer included therein, which have a change in minimum transmittance calculated by Equation 1 above of 20% or less, have been described in detail previously, detailed descriptions will be omitted here.

In the step of forming the photopolymer layer, a photopolymer composition containing the above-described structure can first be prepared. When manufacturing the photopolymer composition, a commonly known mixer, stirrer, or mixer can be used to mix each component without any restrictions. And, this mixing process may be performed at a temperature ranging from 0°C to 100°C, a temperature ranging from 10°C to 80°C, or a temperature ranging from 20°C to 60°C.

In the step of forming the photopolymer layer, the prepared photopolymer composition may be applied to form a coating film formed from the photopolymer composition. The coating film may be dried at a temperature of 50 ℃ or higher, 55 ℃ or higher, 60 ℃ or higher, 65 ℃ or higher or 70 ℃ or lower and 120 ℃ or lower, 110 ℃ or lower, 100 ℃ or lower or 90 ℃ or lower. Through this process, the desired crosslinking density can be achieved by inducing a hydrosilylation reaction between the hydroxy group of the (meth)acrylic polyol that remains unreacted and the silane functional group of the siloxane polymer.

In the photopolymer layer prepared through the step of forming the photopolymer layer, photoreactive monomers, a photoinitiator system, and additives added as necessary may be uniformly dispersed within the crosslinked polymer matrix.

Then, in the step of recording optical information, when the photopolymer layer is irradiated with a coherent laser, polymerization of the photoreactive monomer occurs in the area where constructive interference occurs to form a photopolymer, and in the area where destructive interference occurs, the photoreactive monomer is formed. Polymerization does not occur or is suppressed, resulting in the presence of a photoreactive monomer. In addition, the unreacted photoreactive monomer diffuses toward the photopolymer with a lower concentration of the photoreactive monomer, causing refractive index modulation, and a diffraction grating is created by the refractive index modulation. Accordingly, holograms, i.e. optical information, are recorded on the photopolymer layer with the diffraction grating.

The method of manufacturing a hologram recording medium according to another embodiment may further include the step of photobleaching the photopolymer layer on which the optical information is recorded by irradiating light as a whole after the step of recording the optical information.

In the photobleaching step, ultraviolet rays are irradiated to the photopolymer layer on which optical information is recorded to terminate the reaction of the photoreactive monomer remaining in the photopolymer layer, and the color of the photosensitive dye can be removed. For example, in the photobleaching step, ultraviolet rays (UVA) in the range of 320 to 400 nm are irradiated to terminate the reaction of the photoreactive monomer and remove the color of the photosensitive dye.

Meanwhile, according to another embodiment of the invention, an optical element including the hologram recording medium is provided.

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

An example of an optical element including the hologram recording medium may be a hologram display device. The holographic display device includes a light source unit, an input unit, an optical system, and a display unit.

Specifically, the light source unit is a part that 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 is a part that pre-inputs the 3D image information of the object to be recorded on the display unit. Specifically, the 3D information of the object, such as the intensity and phase of light in each space, is input to an electrically driven liquid crystal SLM (electrically addressed liquid crystal SLM). Input is possible, and this is the part where the input beam can be used.

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

The display unit can receive 3D image information of an object from an input unit, record it on a hologram plate made of an optically driven SLM (optically addressed SLM), and reproduce the 3D image of the object. At this time, 3D image information of the object can be recorded through interference between the input beam and the 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 the readout beam, and an erase beam can be used to quickly remove the formed diffraction pattern. Meanwhile, the hologram plate can be moved between a position where a 3D image is input and a position where it is played.

The holographic recording medium according to one embodiment of the invention exhibits excellent stability over time at high temperatures before recording optical information, and exhibits the originally intended optical recording characteristics even when stored for a long time at room temperature or high temperature, and has diffraction efficiency, etc., which are fundamentally required for a holographic recording medium. The physical properties also show very excellent characteristics.

Figure 1 schematically shows the recording equipment setup for hologram recording. Specifically, Figure 1 shows that a laser of a predetermined wavelength is irradiated from a light source 10, followed by a mirror (20, 20'), an iris (30), a spatial filter (40), Through the iris (30'), the collimation lens (50), and the polarized beam splitter (PBS) (60), the PP (hologram recording medium) (80) located on one side of the mirror (70) This is a schematic illustration of the investigation process.

Hereinafter, the operation and effects of the invention will be described in more detail through specific examples of the invention. However, this is presented as an example of the invention, and the scope of the invention is not limited by this in any way.

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

Preparation Example 1: Preparation of (meth)acrylic polyol

132 g of butyl acrylate, 420 g of ethyl acrylate, and 48 g of hydroxybutyl acrylate were added to a 2 L jacketed reactor, and diluted with 1200 g of ethyl acetate. . The reaction temperature was set to 60-70°C, and stirring was performed for about 30 minutes to 1 hour. An additional 0.42 g of n-dodecyl mercaptan (n-DDM) was added, and stirring was continued for another 30 minutes. Afterwards, 0.24 g of AIBN, a polymerization initiator, was added, polymerization was carried out at the reaction temperature for more than 4 hours, and the residual acrylate content was maintained at less than 1%, resulting in a (meth)acrylate-based copolymer in which the hydroxyl group is located in the branched chain. (Weight average molecular weight approximately 300,000, OH equivalent weight approximately 1802 g/equivalent) was prepared.

Preparation Example 2: Preparation of fluorine-based compound

After adding 20.51 g of 2,2'-{oxybis[(1,1,2,2-tetrafluoroethane-2,1-diyl)oxy]}bis(2,2-difluoroethan-1-ol) to a 1000 mL flask. , was dissolved in 500 g of tetrahydrofuran and 4.40 g of sodium hydride (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 dropped. When it was confirmed that all the reactants were consumed by 1H NMR, 29 g of a liquid product with a purity of 95% or more was obtained with a yield of 98% through work-up using dichloromethane. 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.

Example 1: Preparation of holographic recording medium

(1) Preparation of photopolymer composition

As a siloxane polymer, trimethylsilyl terminated poly(methylhydrosiloxane) (manufactured by Sigma-Aldrich, number average molecular weight: about 390, SiH equivalent about 103 g/equivalent) and (meth)acrylic polyol prepared in Preparation Example 1 were first mixed. The content of the (meth)acrylic polyol was 22.4 g, and the siloxane-based polymer was added so that the SiH/OH molar ratio was 2. In Example 1, 2.6 g of siloxane-based polymer was added.

In addition, 52 g of HR 6042 (Miwon, refractive index 1.60) as a photoreactive monomer, 0.2 g of a compound represented by the following formula (a) as a photosensitive dye, and hexadecyl dimethyl benzyl ammonium tri(m-chloro-p-methylphenyl) as a co-initiator. 0.8 g of butyl borate, 0.05 g of 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (TCI), 0.9 g of Irgacure 369 as a photoinitiator, and 0.9 g of Irgacure 369 as a plasticizer. 23 g of the fluorine-based compound prepared in Preparation Example 2 and 190 g of methyl isobutyl ketone (MIBK) as a solvent were added, and stirred for about 30 minutes with a paste mixer while blocking light. Afterwards, 0.014 g of Karstedt (Pt-based) catalyst was added for matrix crosslinking to prepare a photopolymer composition.

[Formula a]

(2) Manufacturing of holographic recording media

The photopolymer composition was coated to a predetermined thickness on a 60 ㎛ thick TAC substrate using a Mayer bar and dried at 80°C for 10 minutes. The thickness of the photopolymer layer after drying was about 15 μm.

Examples 2 to 10 and Comparative Examples 1 to 3: Preparation of hologram recording medium

A hologram recording medium was manufactured in the same manner as Example 1, except that the open tense was changed as shown in Table 1 below.

electron donor electron acceptor Example 1 Hexadecyl dimethyl benzyl ammonium tri(m-chloro-p-methylphenyl)butyl borate 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine Example 2 Hexadecyl dimethyl benzyl ammonium tri(m-chloro-p-methylphenyl)butyl borate - Example 3 Hexadecyl dimethyl benzyl ammonium tri(p-chlorophenyl)butyl borate 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine Example 4 Hexadecyl dimethyl benzyl ammonium tri(p-chlorophenyl)butyl borate - Example 5 Tetrabutyl ammonium tri(6-chloro-2-naphthyl)butyl borate 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine Example 6 Tetrabutyl ammonium tri(6-chloro-2-naphthyl)butyl borate - Example 7 Tetrabutyl ammonium tri(m-chloro-p-methylphenyl)butyl borate 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine Example 8 Tetrabutyl ammonium tri(m-chloro-p-methylphenyl)butyl borate - Example 9 Tetrabutyl ammonium tri(2-naphthyl)butyl borate - Example 10 Hexadecyl Benzyl Pyrrolidinium Tri(p-Chlorophenyl)Butyl Borate Comparative Example 1 WPBG-300 (1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium tri(phenyl)butyl borate) 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine Comparative Example 2 WPBG-300 Comparative Example 3 Tetrabutyl ammonium tri(o-methylphenyl)hexyl borate -

Test Example 1: Analysis of hologram recording medium

(1) Element ratio

The elemental ratios of the surfaces were analyzed for the pre-recording and post-recording samples by the method described below.

Specifically, the sample to be analyzed was fixed on a copper foil with carbon tape, placed on a sample holder and fixed using a clip. Then, data were acquired using an The element ratio (atomic %) of the sample surface was analyzed.

The system specifications of the ESCA device used are as follows.

- Base chamber pressure: ^1.0

- X-ray source: monochromatic Al Kα (1486.6 eV)

- X-ray spot size: 400 ㎛

- Mode: CAE (Constant Analyzer Energy) mode

- Charge compensation: Flood gun (FG03: 100 ㎂, 0.5 V)

Qualitative analysis was performed by conducting an initial survey scan on the surface of the sample subject to analysis in the as-received state under the following conditions, and quantitative analysis was performed through narrow scan (snap) for each element according to the results of the qualitative analysis. The element ratios of three locations were confirmed for each sample, and the peak background smart method was applied for quantitative analysis. The binding energy correction of the core level spectrum was based on C 1s (284.8 eV).

<Survey scan conditions>

- Scan section binding energy: -5 ~ 1350 eV

- Step size: 1 eV

- Per Point dwell time: 20 ms

-Periods: 2

- Pass energy: 200 eV

<narrow scan conditions>

- Scan section binding energy: about 20 eV

- Step size: ~ 0.16 eV

- Per Point dwell time: 1 sec

- Periods: 10~30

- Pass energy: 150 eV

<Etching conditions>

- Source: Ar ion

- Energy: 6 keV

- Cluster size: 75

-Rater size: ^1.6

-Mode: GCIB

All photopolymer compositions prepared in the Examples and Comparative Examples included the polymer matrix, photoreactive monomer, and fluorine-based compound, which accounted for the largest proportion of their solid content, at 25 g, 52 g, and 23 g, respectively, resulting in polymer matrix:photoreactive monomer. :The weight ratio of the fluorine-based compounds was all 25:52:23.

As a result, the element ratios of all samples prepared in the examples and comparative examples were 62.1 atomic% for carbon, 0.9 atomic% for nitrogen, 21.0 atomic% for oxygen, 6.2 atomic% for fluorine, and 9.8 atomic% for silicon.

In addition, as a result of measuring the element ratios on the surface of the sample before and after recording, the element ratios on the surface of the sample before and after recording were measured to be the same.

(2) Calculation of reaction energy

To calculate the reaction energy E2 in Scheme 1 below, the lowest singlet ^excitation energy ( ^S1 ) of the borate anion ( ^{BX 1} The lowest triplet excitation energy (T1) of the photosensitive dye (Dye) was determined. Using density functional theory (DFT), S1 and T1 were calculated for the optimized structure using B3LYP as the functional and 6-31G ^* as the basis function.

Since the photosensitive dye undergoes an electron reduction reaction, T1 is written as a negative value, and since the electron donor undergoes an electron oxidation reaction, S1 is written as a positive value, and the total reaction energy E2 is calculated by adding these.

[Scheme 1]

T1 of photosensitive dye Types of Electron Donors S1 of electron donor Reaction energy (E2) Example 1 -465.4 kJ/mol Hexadecyl dimethyl benzyl ammonium tri(m-chloro-p-methylphenyl)butyl borate +454.9 kJ/mol -10.5 kJ/mol Example 2 Hexadecyl dimethyl benzyl ammonium tri(m-chloro-p-methylphenyl)butyl borate +454.9 kJ/mol -10.5 kJ/mol Example 3 Hexadecyl dimethyl benzyl ammonium tri(p-chlorophenyl)butyl borate +456.9 kJ/mol -8.5 kJ/mol Example 4 Hexadecyl dimethyl benzyl ammonium tri(p-chlorophenyl)butyl borate +456.9 kJ/mol -8.5 kJ/mol Example 5 Tetrabutyl ammonium tri(6-chloro-2-naphthyl)butyl borate +456.9 kJ/mol -8.5 kJ/mol Example 6 Tetrabutyl ammonium tri(6-chloro-2-naphthyl)butyl borate +456.9 kJ/mol -8.5 kJ/mol Example 7 Tetrabutyl ammonium tri(m-chloro-p-methylphenyl)butyl borate +454.9 kJ/mol -10.5 kJ/mol Example 8 Tetrabutyl ammonium tri(m-chloro-p-methylphenyl)butyl borate +454.9 kJ/mol -10.5 kJ/mol Example 9 Tetrabutyl ammonium tri(2-naphthyl)butyl borate +443.8 kJ/mol -21.6 kJ/mol Example 10 Hexadecyl Benzyl Pyrrolidinium Tri(p-Chlorophenyl)Butyl Borate +456.9 kJ/mol -8.5 kJ/mol Comparative Example 1 WPBG-300 +435.3 kJ/mol -30.1 kJ/mol Comparative Example 2 WPBG-300 +435.3 kJ/mol -30.1 kJ/mol Comparative Example 3 Tetrabutyl ammonium tri(o-methylphenyl)hexyl borate +399.1 kJ/mol -66.3 kJ/mol

Test Example 2: Performance evaluation of hologram recording medium

(1) Thermal stability (△T)

Thermal stability was evaluated as the lowest transmittance change (△T) before and after exposure to high temperature. Specifically, the thermal stability was evaluated based on the lowest transmittance change after recording the diffraction grating on the pre-recording sample that was not exposed to high temperature and the pre-recording sample exposed to high temperature, and the lowest transmittance change was obtained through Equation 1 below.

[Equation 1]

△T(%) = {(│T _{1 -} T ₀ │)/ T ₀ }

In Equation 1, T ₀ is stored in a dark room under conditions of constant temperature (20 to 25 ℃) and constant humidity (relative humidity of 40 to 50%) before recording, and then a UV-Vis spectrometer is used for the sample on which the notch filter hologram was recorded. This is the lowest transmittance measured in the wavelength range of 300 to 1,200 nm, and T ₁ is the method described above for the sample on which the notch filter hologram was recorded after storing the sample for 100 hours in a dark room at 60 ℃ and 40 to 50% relative humidity conditions before recording. This is the lowest transmittance measured the same as .

The notch filter hologram was recorded using the same setup as shown in Figure 1. Specifically, when the manufactured 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 generated through interference between incident light (L) and light reflected from the mirror (L'). This can be recorded. In this example, the notch filter hologram was recorded with an incident angle of 0 ° (degree). Notch filters and Bragg reflectors are optical elements that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indices are stacked periodically and repeatedly at a certain thickness.

(2) Diffraction efficiency (DE)

Diffraction efficiency (η) was obtained through Equation 2 below for the sample on which the notch filter hologram was recorded in the above-described manner.

[Equation 2]

η(%) = {P _D / (P _D + P _T )}

In Equation 2, η is the diffraction efficiency, P _D is the output amount of the diffracted beam of the sample after recording (mW/cm2), and P _T is the output amount of the transmitted beam of the sample after recording (mW/cm2).

Reaction energy (E2) Thermal stability (△T, %) Diffraction efficiency (DE, %) Example 1 -10.5 kJ/mol 3.2 97.0 Example 2 -10.5 kJ/mol 5.8 89.2 Example 3 -8.5 kJ/mol 0.8 98.0 Example 4 -8.5 kJ/mol 1.2 92.7 Example 5 -8.5 kJ/mol 2.1 91.2 Example 6 -8.5 kJ/mol 4.2 87.8 Example 7 -10.5 kJ/mol 7.8 90.2 Example 8 -10.5 kJ/mol 11.2 88.5 Example 9 -21.6 kJ/mol 15.3 87.9 Example 10 -8.5 kJ/mol 2.2 91.5 Comparative Example 1 -30.1 kJ/mol 78 92.1 Comparative Example 2 -30.1 kJ/mol 92.8 89.2 Comparative Example 3 -66.3 kJ/mol 100 96.4

Referring to Table 3, the hologram recording medium according to one embodiment of the invention adopts an electron donor with a reaction energy of -25 to 0 kJ/mol with a photosensitive dye excited in a triplet state, so that it is recorded at a high temperature before recording. It is confirmed that the stability over time is very excellent, and the diffraction efficiency, which is a general physical property of the hologram recording medium, is also confirmed to be very excellent.

In addition, it was confirmed that Examples 1, 3, 5, 7 and Comparative Example 1, which additionally included an electron acceptor, exhibited superior high temperature stability over time compared to Examples 2, 4, 6, 8 and Comparative Example 2 which did not contain the electron acceptor. .

Claims (19)

A polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol; And a photopolymer layer containing a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom,
A holographic recording medium with a change in lowest transmittance of 20% or less, calculated by Equation 1 below:
[Equation 1]
△T(%) = {(│T _{1 -} T ₀ │)/ T ₀ }
In Equation 1, T ₀ is 300 to 300 using a UV-Vis spectrometer for the sample on which the notch filter hologram was recorded after storing the hologram recording medium before recording in a dark room at a temperature of 20 to 25 ℃ and relative humidity of 40 to 50%. The lowest transmittance measured in the wavelength range of 1,200 nm,
T ₁ is the lowest transmittance measured as above for the sample on which the notch filter hologram was recorded after the hologram recording medium was stored for 100 hours in a dark room at a temperature of 60 ° C. and a relative humidity of 40 to 50% before recording.
The holographic recording medium of claim 1, wherein the siloxane-based polymer includes a repeating unit represented by the following formula (1) and a terminal group represented by the following formula (2):
[Formula 1]

In Formula 1,
A plurality of R ¹ and R ² are the same or different from each other and are each independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,
n is an integer from 1 to 10,000,
[Formula 2]

In Formula 2,
A plurality of R ¹¹ to R ¹³ are the same or different from each other, and each independently represents hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms,
At least one of R ¹ , R ² , and R ¹¹ to R ¹³ of at least one of the repeating units represented by Formula 1 and the terminal group represented by Formula 2 is hydrogen.
The hologram recording medium according to claim 1, wherein the (meth)acrylic polyol is a polymer having a structure in which a hydroxy group is bonded to the main chain or side chain of a (meth)acrylate polymer.
The hologram recording medium according to claim 1, wherein the molar ratio of the silane functional group of the siloxane-based polymer to the hydroxyl group of the (meth)acrylic polyol is 1.5 to 4.
The method of claim 1, wherein the photoreactive monomer is benzyl (meth)acrylate, benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, phenol (ethylene oxide). ₂ (meth)acrylate, O -phenylphenol (ethylene oxide) (meth)acrylate, phenylthioethyl (meth)acrylate, and biphenylmethyl (meth)acrylate, at least one monofunctional monomer selected from the group consisting of; Bisphenol A (ethylene oxide) _2~10 di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris( At least one polyfunctional monomer selected from the group consisting of 2-hydroxyethyl)isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate, and cresol novolak epoxy (meth)acrylate; or a holographic recording medium containing a mixture of two or more of these.
The hologram recording medium of claim 1, wherein the photoreactive monomer is contained in an amount of 50 to 300 parts by weight based on 100 parts by weight of the polymer matrix.
The holographic recording medium of claim 1, wherein the photopolymer layer further comprises a fluorine-based compound.
The method of claim 7, wherein, with respect to the total amount of carbon, nitrogen, oxygen, fluorine and silicon atoms confirmed by photoelectron spectroscopy on the surface of the photopolymer layer, the elemental ratio of carbon is 50 to 70 atomic%, and the elemental ratio of nitrogen is 0.01 to 0.01. 2 atomic%, the elemental ratio of oxygen is 15 to 30 atomic%, the elemental ratio of fluorine is 3 to 12 atomic%, and the elemental ratio of silicon is 3 to 15 atomic%.
The method of claim 7, wherein the photopolymer layer contains 17 to 38% by weight of the polymer matrix, 33 to 58% by weight of the photoreactive monomer, and 17 to 38% by weight of the fluorine-based compound, based on the total weight of the polymer matrix, photoreactive monomer, and fluorine-based compound. Holographic recording media, comprising weight percent.
The holographic recording medium of claim 1, wherein the photoinitiator system includes a photosensitive dye and a coinitiator.
The holographic recording medium of claim 10, wherein the photosensitive dye includes a silicon rhodamine compound represented by the following formula (4):
[Formula 4]

In Formula 4 above,
R ²¹ to R ²⁹ are each independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or It is a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms,
d and e are each independently integers from 0 to 3,
f is an integer from 0 to 5,
An ^- is an anion.
The hologram recording medium according to claim 10, wherein the co-initiator includes an electron donor, and the reaction energy of the electron donor with the photosensitive dye excited in a triplet state is -25 to 0 kJ/mol.
13. The holographic recording medium of claim 12, wherein the electron donor includes a borate anion represented by the following formula (5):
[Formula 5]
^{BX 1 ​ ​}
In Formula ⁵ , X ¹ to It is an alkylaryl group or an allyl group having 7 to 30 carbon atoms, but at least one of X ¹ to X ⁴ is not an aryl group.
The hologram recording medium of claim 12, wherein the electron donor includes at least one borate anion selected from the group consisting of borate anions represented by the following formulas 5-1 and 5-2:
[Formula 5-1]

In Formula 5-1,
R ¹⁰² is each independently methyl or halogen,
R ¹⁰³ is each independently hydrogen, methyl or halogen, but when the adjacent R ¹⁰² is methyl, it is halogen,
X ^4' is a straight-chain alkyl group having 1 to 12 carbon atoms,
[Formula 5-2]

In Formula 5-2,
R ¹⁰⁶ is each independently hydrogen, methyl or halogen,
X ^4" is a straight-chain alkyl group having 1 to 12 carbon atoms.
The holographic recording medium of claim 12, wherein the electron donor includes at least one member selected from the group consisting of a cation represented by the following formula 5-3 and a cation represented by the following formula 5-4:
[Formula 5-3]
NY ¹ Y ² Y ³ Y ⁴
In Formula 5-3, two substituents of Y ¹ to Y ⁴ may or may not be connected to each other to form an aliphatic ring having 4 to 10 carbon atoms,
Y ¹ to Y ⁴ that do not form an aliphatic ring are each independently an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an alkyl group with 2 to 40 carbon atoms linked through an ester bond. become,
It is excluded that Y ¹ to Y ⁴ are all methyl groups, or two or more substituents are alkyl groups having 16 or more carbon atoms,
[Formula 5-4]

In Formula 5-4, R ¹⁰⁷ , R ¹⁰⁹ and R ¹¹⁰ are each independently hydrogen, an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an ester bond. It is an alkyl group having 2 to 40 carbon atoms,
R ¹⁰⁸ and R ¹¹¹ are each independently an alkyl group with 1 to 40 carbon atoms, an aryl group with 6 to 30 carbon atoms, an arylalkyl group with 6 to 40 carbon atoms, or an alkyl group with 2 to 40 carbon atoms linked through an ester bond.
11. The holographic recording medium of claim 10, wherein the coinitiator includes an electron acceptor, and the electron acceptor includes a triazine compound.
The hologram recording medium according to claim 1, wherein the diffraction efficiency is 80% or more when recording a notch filter hologram.
A polymer matrix formed by crosslinking a siloxane-based polymer containing a silane functional group and a (meth)acrylic-based polyol, or a precursor thereof; Photoreactive monomer; and applying and drying a photopolymer composition containing a photoinitiator system to form a photopolymer layer, thereby manufacturing a hologram recording medium before recording with a change in minimum transmittance of 20% or less as calculated by Equation 1 below; and
A method of producing a hologram recording medium, comprising the step of recording optical information by irradiating a coherent laser to a predetermined area of the photopolymer layer to selectively polymerize photoreactive monomers included in the photopolymer layer:
[Equation 1]
△T(%) = {(│T _{1 -} T ₀ │)/ T ₀ }
In Equation 1, T ₀ is 300 to 300 using a UV-Vis spectrometer for the sample on which the notch filter hologram was recorded after storing the hologram recording medium before recording in a dark room at a temperature of 20 to 25 ℃ and relative humidity of 40 to 50%. The lowest transmittance measured in the wavelength range of 1,200 nm,
T ₁ is the lowest transmittance measured as above for the sample on which the notch filter hologram was recorded after the hologram recording medium was stored for 100 hours in a dark room at a temperature of 60 ° C. and a relative humidity of 40 to 50% before recording.
An optical device comprising the hologram recording medium of claim 1.