HOLOGRAM RECORDING MEDIUM AND OPTICAL ELEMENT COMPRISING THE SAME

Abstract

The present invention relates to a hologram recording medium and an optical clement comprising the same. The hologram recording medium not only has excellent optical recording properties but also can exhibit transparent optical properties and excellent reliability even in high temperature and high humidity environments.

Claims

1. A hologram recording medium comprising: a photopolymer layer which includes 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; a photoreactive monomer and a photoinitiator system or a photopolymer obtained therefrom; and a fluorinated compound, wherein a peak variation as calculated by the following Equation 3 is 3% or less, and wherein an adhesive force is at least 500 gf/2.5 cm, which is measured at a peeling angle of 180 and a peeling speed of 5 mm/sec after laminating an optically transparent adhesive layer onto the photopolymer layer, and storing under a temperature of 60 C. and a relative humidity of 90% for 72 hours, $\begin{array}{cc}\mathrm{Peak}\mathrm{variation}=\left\{.Math.1-A_1/A_0.Math.\right\}100& \left[\mathrm{Equation}3\right]\end{array}$ wherein, in the Equation 3, A.sub.0 is a wavelength of the lowest transmittance of the hologram recording medium for a wavelength range of 300 to 1,200 nm, and A.sub.1 is a wavelength of the lowest transmittance measured after exposing the hologram recording medium to a temperature of 60 C. and a relative humidity of 90% for 72 hours.

2. The hologram recording medium according to claim 1, wherein the siloxane-based polymer comprises a repeating unit represented by the following Chemical Formula 2 and a terminal end group represented by the following Chemical Formula 3: ##STR00026## wherein, in the Chemical Formula 2, a plurality of R.sup.11 and R.sup.12 are the same or different from each other, and are each independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and k is an integer of 1 to 10,000, ##STR00027## wherein, in the Chemical Formula 3, a plurality of R.sup.13 to R.sup.15 are the same or different from each other, and are each independently hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, and at least one of R.sup.11 to R.sup.15 of at least one repeating unit selected among the repeating units represented by Chemical Formula 2 and any one terminal end group selected among the terminal end groups represented by Chemical Formula 3 is hydrogen.

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

4. The hologram recording medium according to claim 1, wherein the photoreactive monomer comprises at least one monofunctional monomer selected from the group consisting of benzyl (meth)acrylate, benzyl 2-phenylacrylate, phenoxybenzyl (meth)acrylate, phenol (ethylene oxide) (meth)acrylate, phenol (ethylene oxide).sub.2 (meth)acrylate, O-phenylphenol (ethylene oxide) (meth)acrylate, phenylthioethyl (meth)acrylate and biphenylmethyl (meth)acrylate; at least one polyfunctional monomer selected from the group consisting of bisphenol A (ethylene oxide).sub.210 di(meth)acrylate, bisphenol A epoxy di(meth)acrylate, bisfluorene di(meth)acrylate, modified bisphenol fluorene di(meth)acrylate, tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, phenol novolac epoxy (meth)acrylate and cresol novolac epoxy (meth)acrylate; or a mixture of two or more thereof.

5. The hologram recording medium according to claim 1, wherein the photoinitiator system comprises a photosensitizing dye and a coinitiator.

6. The hologram recording medium according to claim 5, wherein the coinitiator comprises a borate anion represented by the following Chemical Formula 4:
BX.sup.1X.sup.2X.sup.3X.sup.4 [Chemical Formula 4] wherein, in the Chemical Formula 4, X.sup.1 to X.sup.4 are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, or an allyl group, each of which is substituted or unsubstituted, with the proviso that at least one of X.sup.1 to X.sup.4 is not an aryl group.

7. The hologram recording medium according to claim 1, wherein the fluorinated compound comprises a fluorinated compound represented by the following Chemical Formula 1: ##STR00028## wherein, in the Chemical Formula 1, Z.sup.1 and Z.sup.2 are each independently O, S, or NH, at least one of R.sup.1 to R.sup.4 is a fluorine-containing substituent, which is an alkyl group having 1 to 20 carbon atoms substituted with 2 or more fluorines, a cycloalkyl group having 3 to 30 carbon atoms substituted with 2 or more fluorines, or an aryl group having 6 to 30 carbon atoms substituted with 2 or more fluorines, when R.sup.1 to R.sup.4 are not fluorine-containing substituents, they are each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 4 to 30 carbon atoms, a cycloalkylalkyl group having 7 to 40 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 4 to 30 carbon atoms or an arylalkyl group having 7 to 40 carbon atoms, or at least one CH.sub.2 of the above substituents is a substituent substituted with O, S or NH.

8. The hologram recording medium according to claim 7, wherein R.sup.1 in the Chemical Formula 1 is the fluorine-containing substituent.

9. The hologram recording medium according to claim 7, wherein the fluorine-containing substituent is a straight chain alkyl group having 1 to 20 carbon atoms substituted with 2 or more fluorines, a cycloalkyl group having 3 to 12 carbon atoms substituted with 2 or more fluorines or an aryl group having 6 to 14 carbon atoms substituted with 2 or more fluorines.

10. The hologram recording medium according to claim 7, wherein the fluorine-containing substituent is (CH.sub.2).sub.a(CF.sub.2).sub.bCHF.sub.2, (CH.sub.2).sub.a(CF.sub.2).sub.bCF.sub.3 or decafluorocyclohexyl group, where a is an integer of 0 to 3, and b is an integer of 0 to 19.

11. The hologram recording medium according to claim 7, wherein when R.sup.1 to R.sup.4 in the Chemical Formula 1 are not fluorine-containing substituents, R.sup.1 to R.sup.4 are each independently a straight chain alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a heterocycloalkyl group having 4 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heteroaryl group having 4 to 12 carbon atoms, an arylalkyl group having 7 to 16 carbon atoms, or (R.sup.5Y.sup.1).sub.cR.sup.6, where, R.sup.5 is an alkylene group having 1 to 6 carbon atoms, R.sup.6 is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, Y.sup.1 is O or S, and c is an integer of 1 to 12, with the proviso that when c is 2 or more, R.sup.5-s are the same or different from each other.

12. The hologram recording medium according to claim 7, wherein the fluorinated compound represented by Chemical Formula 1 comprises at least one fluorinated compound selected from the group consisting of fluorinated compounds represented by the following Chemical Formulas 1-1 to 1-9: ##STR00029## wherein, in the Chemical Formula 1-1, z.sup.a1 and Z.sup.b1 are each independently O, S, or NH, R.sup.a1 and R.sup.b1 are each independently CF.sub.3 or CHF.sub.2, R.sup.c1 and R.sup.c2 are each independently an alkylene group having 1 to 6 carbon atoms, Y.sup.a1 and Y.sup.a2 are each independently CH.sub.2, O, S, or NH, R.sup.d1 and R.sup.d2 are each independently an alkylene group having 1 to 4 carbon atoms, R.sup.e1 and R.sup.e2 are each independently hydrogen, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p1 and p2 are each independently an integer of 0 to 9, and q1 and q2 are each independently an integer of 0 to 3, ##STR00030## wherein, in the Chemical Formula 1-2, Z.sup.a2 and Z.sup.b2 are each independently O, S, or NH, R.sup.a2 is CF.sub.3 or CHF.sub.2, R.sup.c3 to R.sup.c5 are each independently an alkylene group having 1 to 6 carbon atoms, Y.sup.a3 to Y.sup.a5 are each independently CH.sub.2, O, S, or NH, R.sup.d3 to R.sup.d5 are each independently an alkylene group having 1 to 4 carbon atoms, R.sup.e3 to R.sup.e5 are each independently hydrogen, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p3 is an integer of 0 to 9, and q3 to q5 are each independently an integer of 0 to 3, ##STR00031## wherein, in the Chemical Formula 1-3, Z.sup.a3 and Z.sup.b3 are each independently O, S, or NH, R.sup.a3, R.sup.b2 and R.sup.b3 are each independently CF.sub.3 or CHF.sub.2, R.sup.c6 is an alkylene group having 1 to 6 carbon atoms, Y.sup.a6 is CH.sub.2, O, S, or NH, R.sup.d6 is an alkylene group having 1 to 4 carbon atoms, R.sup.e6 is hydrogen, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, R.sup.f1 and R.sup.f2 are each independently hydrogen or fluorine, and p4 to p6 are each independently an integer of 0 to 9, and q6 is an integer of 0 to 3, ##STR00032## wherein, in the Chemical Formula 1-4, Z.sup.a4 and Z.sup.b4 are each independently O, S, or NH, R.sup.a4, R.sup.a5, R.sup.b4 and R.sup.b5 are each independently CF.sub.3 or CHF.sub.2, R.sup.f3 to R.sup.f6 are each independently hydrogen or fluorine, and p7 to p10 are each independently an integer of 0 to 9, ##STR00033## wherein, in the Chemical Formula 1-5, Z.sup.a5 and Z.sup.b5 are each independently O, S, or NH, R.sup.a6 and R.sup.a7 are each independently CF.sub.3 or CHF.sub.2, R.sup.c7 and R.sup.c8 are each independently an alkylene group having 1 to 6 carbon atoms, Y.sup.a7 and Y.sup.a8 are each independently CH.sub.2, O, S, or NH, R.sup.d7 and R.sup.d8 are each independently an alkylene group having 1 to 4 carbon atoms, R.sup.e7 and R.sup.e8 are each independently hydrogen, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p11 to p12 are each independently an integer of 0 to 9, and q7 and q8 are each independently an integer of 0 to 3, ##STR00034## wherein, in the Chemical Formula 1-6, Z.sup.a6 and Z.sup.b6 are each independently O, S, or NH, R.sup.a8 to R.sup.a10 are each independently CF.sub.3 or CHF.sub.2, R.sup.c9 is an alkylene group having 1 to 6 carbon atoms, Y.sup.a9 is CH.sub.2, O, S, or NH, R.sup.d9 is an alkylene group having 1 to 4 carbon atoms, R.sup.e9 is hydrogen, an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, or a phenyl group, p13 to p15 are each independently an integer of 0 to 9, and q9 is an integer of 0 to 3, ##STR00035## wherein, in the Chemical Formula 1-7, Z.sup.a7 and Z.sup.b7 are each independently O, S, or NH, and R.sup.b9, R.sup.c10 and R.sup.d10 are each independently a decafluorocyclohexyl group, a phenyl group, a pyridinyl group, a pyrimidinyl group or a methoxyethyl group, ##STR00036## wherein, in the Chemical Formula 1-8, Z.sup.a8 and Z.sup.b8 are each independently O, S, or NH, and R.sup.b10, R.sup.c11 and R.sup.d11 are cach independently a 2,2,3,3,4,4,5,5-octafluoro-1-pentyl group, a decafluorocyclohexyl group, a phenyl group, or a methoxyethyl group, ##STR00037## wherein, in the Chemical Formula 1-9, Z.sup.a9 and Z.sup.b9 are each independently O, S, or NH, R.sup.a11 and R.sup.b11 are each independently CF.sub.3 or CHF.sub.2, R.sup.c12 and R.sup.d12 are each independently a phenyl group or a benzyl group, and p16 and p17 are each independently an integer of 0 to 9.

13. The hologram recording medium according to claim 1, wherein an amount of the fluorinated compound is 20 to 200 parts by weight based on 100 parts by weight of the polymer matrix.

14. The hologram recording medium according to claim 1, wherein when recording a notch filter hologram, a diffraction efficiency is 70% or more.

15. The hologram recording medium according to claim 1, wherein the photopolymer layer has a thickness of 5 to 30 m and a refractive index modulation value of at least 0.020.

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

17. An optical element comprising the hologram recording medium according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0207] FIG. 1 schematically shows the recording equipment setup for hologram recording. Specifically, FIG. 1 schematically shows the process in which a laser of a predetermined wavelength is radiated from the light source 10, and irradiated onto the PP (hologram recording medium) 80 located on one surface of a mirror 70 via mirrors 20 and 20, an iris 30, a spatial filter 40, an iris 30, a collimation lens 50, and PBS (Polarized Beam Splitter) 60.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0208] Hereinafter, the action and effect of the invention will be described in more detail with reference to specific examples of the invention. However, these examples are presented for illustrative purposes only, and the scope of the invention is not limited thereby in any way.

[0209] In the following Preparation Examples, Examples, and Comparative Examples, the content of raw materials, and the like means the content based on solid content, unless otherwise specified.

PREPARATION EXAMPLE 1: PREPARATION OF (METH)ACRYLIC-BASED POLYOL

[0210] 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 the mixture was stirred for about 30 minutes to 1 hour. 0.42 g of n-dodecyl mercaptan (n-DDM) was further added, and stirring was further performed for about 30 minutes. Then, 0.24 g of AIBN as a polymerization initiator was added, polymerization was carried out at the reaction temperature for 4 hours or more, and kept until the residual acrylate content became less than 1%. Thereby, a (meth)acrylate-based copolymer (weight average molecular weight of about 300,000, OH equivalent of about 1802 g/equivalent) in which the hydroxy group is located in the branched chain was prepared.

EXAMPLE 1: PREPARATION OF PHOTOPOLYMER COMPOSITION AND HOLOGRAM RECORDING MEDIUM

(1) Preparation of Photopolymer Composition

[0211] 1.27 g of poly(methylhydrosiloxane) (Sigma-Aldrich, number average molecular weight: about 390, SiH equivalent: about 103 g/equivalent) as a siloxane-based polymer and 11.12 g of (meth)acrylic-based polyol prepared in Preparation Example 1 were first mixed (SiH/OH molar ratio=2.0).

[0212] Then, 20 g of HR 6042 (Miwon Specialty Chemical, refractive index of 1.60) as a photoreactive monomer, 0.08 g of photosensitizing dye H-Nu 640 (Spectra Group), 0.3 g of borate V as a coinitiator, 0.05 g of H-Nu 254 (Spectra), 10 g of the fluorinated compound represented by the following Chemical Formula a as a plasticizer and 26 g of methyl isobutyl ketone (MIBK) as a solvent were added, and the mixture was stirred with a paste mixer for about 30 minutes while blocking light. After that, a photopolymer composition was prepared by adding Karstedt (Pt-based) catalyst for matrix crosslinking.

##STR00014##

(2) Preparation of Hologram Recording Media

[0213] The photopolymer composition was coated to a predetermined thickness on a 60 m 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 m.

[0214] The diffraction grating was recorded using the same setup as in FIG. 1. Specifically, when the prepared photopolymer layer was laminated on a mirror and then irradiated with a laser, a notch filter hologram having periodic refractive index modulation in the thickness direction through interference between incident light L and light reflected from a mirror L can be recorded. In this example, a notch filter hologram was recorded with an incident angle of 0 (degree). A notch filter and a Bragg reflector are optical devices that reflect only light of a specific wavelength, and have a structure in which two layers with different refractive indexes are stacked periodically and repeatedly at a certain thickness.

EXAMPLES 2 TO 9 AND COMPARATIVE EXAMPLES 1 TO 3: PREPARATION OF PHOTOPOLYMER COMPOSITION AND HOLOGRAM RECORDING MEDIUM

[0215] A photopolymer composition and a hologram recording medium were prepared in the same manner as in Example 1, except that the components and contents of the photopolymer composition were different as shown in Table 1 below.

TABLE-US-00001 TABLE 1 Photosensitizing dye Red Dye (H-Nu 640) Green Dye (Safranin O) Plasticizer Recording wavelength Example 1 0.08 g [Chemical Formula a] 10 g 660 nm Example 2 0.08 g [Chemical Formula b] 10 g 660 nm Example 3 0.05 g [Chemical Formula c] 10 g 532 nm Example 4 0.08 g [Chemical Formula d] 10 g 660 nm Example 5 0.05 g [Chemical Formula e] 12 g 532 nm Example 6 0.08 g [Chemical Formula f] 8 g 660 nm Example 7 0.08 g [Chemical Formula g] 8 g 660 nm Example 8 0.08 g [Chemical Formula h] 10 g 660 nm Example 9 0.05 g [Chemical Formula i] 8 g 532 nm Comparative Example 1 0.08 g [Chemical Formula j] 10 g 660 nm Comparative Example 2 0.05 g [Chemical Formula k] 10 g 532 nm Comparative Example 3 0.08 g [Chemical Formula l] 10 g 660 nm [Chemical Formula b] [00015][Chemical Formula c] [00016][Chemical Formula d] [00017][Chemical Formula e] [00018][Chemical Formula f] [00019][Chemical Formula g] [00020][Chemical Formula h] [00021][Chemical Formula i] [00022][Chemical Formula j] [00023][Chemical Formula k] [00024][Chemical Formula l] [00025]

TEST EXAMPLE: PERFORMANCE EVALUATION OF HOLOGRAM RECORDING MEDIA

(1) Diffraction Efficiency

[0216] Diffraction efficiency () was determined through the following Equation 1.

[00003]$\begin{array}{cc}\left(\%\right)=\left\{P_D/\left(P_D+P_T\right)\right\}100& \left[\mathrm{Equation}1\right]\end{array}$ [0217] wherein, in Equation 1, is the diffraction efficiency, P.sub.D is the output amount (mW/cm.sup.2) of the diffracted beam of the sample after recording, and P.sub.T is the output amount (mW/cm.sup.2) of the transmitted beam of the sample after recording.

(2) Refractive Index Modulation Value (n)

[0218] The refractive index modulation value (n) was determined through the following Equation 2 and Bragg's equation.

[00004]$\begin{array}{cc}={\tanh }^2.Math.\frac{\mathrm{nd}}{{\left({\cos }^2-\frac{}{n}\cos \right)}^{1/2}}.Math.& \left[\mathrm{Equation}2\right]\end{array}$$\begin{array}{cc}\cos \left(-\right)=\frac{}{2n}& [\mathrm{Bragg}s\mathrm{Equation}]\end{array}$ [0219] wherein, in Equations, is the reflectance diffraction efficiency (DE), d is the thickness of the photopolymer layer, is the wavelength of incident light for recording (660 nm or 532 nm), is the angle of incidence of the incident light for recording, is the slant angle of the grating, n is the refractive index modulation value, n is the refractive index of the photopolymer, and means the diffraction grating period. In the above Examples and Comparative Examples, since holograms were recorded using the notch filter method, both (incident angle) and (slant angle of the grating) were 0.

(3) Haze

[0220] Haze was measured using a HAZE METER (Murakami Color Research Laboratory, HM-150) in accordance with JIS K 7136. The measurement light was incident on the substrate side surface of the hologram recording medium.

(4) Peak Variation

[0221] First, the specific wavelength (or wavelength band) (A.sub.0) at which the sample recorded with the diffraction grating had the highest reflectance (i.e., lowest transmittance) was analyzed (analyzed at room temperature and non-high humidity conditions). UV-Vis spectroscopy was used for the analysis, and the analysis wavelength range was 300 to 1,200 nm.

[0222] Subsequently, the same sample was stored at a temperature of 60 C. and a relative humidity of 90% for 72 hours, and the wavelength (or wavelength band) (A.sub.1) with the maximum reflectance (minimum transmittance) was recorded in a similar manner. The peak variation, which is the degree of movement of the wavelength with the lowest transmittance before and after evaluation, was measured according to the following Equation 3. At this time, it was assumed that sample deformation (e.g., shrinkage or expansion) did not affect the surface pitch and occurred only in the direction perpendicular to the sample surface.

[00005]$\begin{array}{cc}\mathrm{Peak}\mathrm{variation}=\left\{.Math.1-A_1/A_0.Math.\right\}100& \left[\mathrm{Equation}3\right]\end{array}$

(5) Adhesive Force after Aging

[0223] tesa 61563 (thickness: 50 m, TESA) as a rubber-based OCA (optically clear adhesive) was laminated onto a glass substrate to form an adhesive layer, which was then laminated so that the photopolymer layer of a sample recorded with diffraction grating was in contact with the adhesive layer. Then, the obtained sample was cut to have a width of 2.5 cm, and a sample laminated in the order of glass substrate, adhesive layer, photopolymer layer, and TAC substrate was prepared.

[0224] The prepared sample was stored at a temperature of 60 C. and a relative humidity of 90% for 72 hours, and then the adhesive force between the photopolymer layer and the adhesive layer was measured using a Texture Analyzer. The peeling angle at the time of measuring the adhesive force was 180, and the peeling speed was 5 mm/sec.

TABLE-US-00002 TABLE 2 Adhesive Refractive force after Diffraction index Peak aging efficiency modulation Haze variation (gf/2.5 (%) value (%) (%) cm) Example 1 85 0.032 0.7 1.82 1030 Example 2 87 0.038 0.8 1.67 1170 Example 3 86 0.037 0.9 1.06 860 Example 4 87 0.037 1.0 1.21 930 Example 5 75 0.031 0.8 0.76 1120 Example 6 88 0.037 1.4 1.67 670 Example 7 85 0.035 1.7 2.27 540 Example 8 87 0.038 0.8 1.06 980 Example 9 85 0.036 1.3 1.67 620 Comparative 85 0.031 2.1 6.52 80 Example 1 Comparative 57 0.019 1.9 15.7 270 Example 2 Comparative 87 0.033 0.9 5.71 130 Example 3

[0225] Referring to Table 2, it is confirmed that the hologram recording media prepared in Examples 1 to 9 not only exhibit excellent diffraction efficiency, refractive index modulation value, and low haze, but also exhibits high adhesive force with little change in the wavelength at which the maximum reflectance occurs even after exposure to high temperature/high humidity environments, and is excellent in reliability in a high temperature/high humidity environment. In contrast, the hologram recording media prepared in Comparative Example 2 is inferior in optical recording properties, haze, and reliability in high temperature/high humidity environments. And the hologram recording media prepared in Comparative Examples 1 and 3 are excellent in optical recording properties, but exhibit poor reliability in high temperature/high humidity environments.

[0226] Therefore, it is confirmed that as the holographic recording medium according to one embodiment of the invention includes a fluorinated compound having a specific structure, it has excellent optical recording properties, excellent reliability even in high temperature/high humidity environments, and exhibits high transparency.