PHOTOPOLYMER COMPOSITION

Abstract

The present disclosure relates to a photopolymer composition including a polymer matrix or a precursor thereof having a predetermined chemical structure; a photoreactive monomer; and a photoinitiator, a hologram recording medium, an optical element and a holographic recording method using the same.

Claims

1. A photopolymer composition for forming a hologram recording medium comprising: a polymer matrix or a precursor thereof formed by crosslinking a siloxane-based polymer containing at least one silane functional group (Si—H) and a (meth)acrylic polyol; a photoreactive monomer; and a photoinitiator.

2. The photopolymer composition according to claim 1, wherein the siloxane-based polymer containing at least one silane functional groups (Si—H) includes a repeating unit represented by Chemical Formula 1 or a repeating unit represented by Chemical Formula 2: ##STR00004## wherein in each of the repeating units of Chemical Formula 1, R.sub.1 and R.sub.2 are the same as or different from each other, and are hydrogen, halogen, or an alkyl group having 1 to 10 carbon atoms, n is the number of repetitions of the repeating unit which is 1 to 10,000, and in at least one of the repeating units, R.sub.1 is an alkyl group having 1 to 10 carbon atoms and R.sub.2 is hydrogen. ##STR00005## wherein in each of the repeating units of Chemical Formula 2, R.sub.11 to R.sub.13 are the same as or different from each other, and are hydrogen, halogen or an alkyl group having 1 to 10 carbon atoms, n is the number of repetitions of the repeating unit, which is 1 to 10,000, and in at least one of the repeating units, R.sub.11 and R.sub.13 are an alkyl group having 1 to 10 carbon atoms, R.sub.12 is hydrogen, or R.sub.11 and R.sub.12 are an alkyl group having 1 to 10 carbon atoms, and R.sub.13 is hydrogen.

3. The photopolymer composition according to claim 1, wherein the siloxane-based polymer containing at least one silane functional groups (Si—H) has number average molecular weight of 200 to 4,000.

4. The photopolymer composition according to claim 1, wherein the (meth)acrylic polyol has a structure in which two or more hydroxy groups are bonded to a main chain or side chain of an (meth)acrylate-based polymer, and wherein the (meth)acrylic polyol has a weight average molecular weight of 200,000 to 1,000,000.

5. The photopolymer composition according to claim 1, wherein the (meth)acrylic polyol has a hydroxy group equivalent of 500 g/equivalent to 2,500 g/equivalent.

6. The photopolymer composition according to claim 1, wherein the polymer matrix includes a hydrosilylation reactant between the siloxane-based polymer containing at least one silane functional group (Si—H) and the (meth)acrylic polyol.

7. The photopolymer composition according to claim 1, wherein the photoreactive monomer includes a polyfunctional (meth)acrylate monomer or a monofunctional (meth)acrylate monomer.

8. The photopolymer composition according to claim 1, wherein the photoreactive monomer has a refractive index of 1.5 or more.

9. The photopolymer composition according to claim 1, comprising 1% to 80 wt. % of the polymer matrix or the precursor thereof; 1% to 80 wt. % of the photoreactive monomer; and 0.1% to 20 wt. % of the photoinitiator.

10. The photopolymer composition according to claim 1, wherein the photopolymer composition further comprises a fluorine-based compound.

11. The photopolymer composition according to claim 10, wherein the fluorine-based compound comprises at least one functional group selected from the group consisting of an ether group, an ester group and an amide group, and at least two difluoromethylene groups.

12. The photopolymer composition according to claim 10, wherein the fluorine-based compound has a refractive index of less than 1.45.

13. The photopolymer composition according to claim 1, wherein the polymer matrix has a refractive index of 1.46 to 1.53.

14. A hologram recording medium comprising the photopolymer composition of claim 1.

15. An optical element comprising the hologram recording medium of claim 14.

16. A holographic recording method comprising selectively polymerizing photoreactive monomers contained in the photopolymer composition of claim 1 using a coherent light source.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0099] Hereinafter, the present disclosure will be described in more detail by way of examples. However, these examples are given for illustrative purposes only and are not intended to limit the scope of the present disclosure thereto.

PREPARATION EXAMPLE

Preparation Example 1: Preparation of (Meth)Acrylic Polyol for Matrix

[0100] 460 g of butyl acrylate, 276 g of methyl acrylate, and 64 g of hydroxybutyl acrylate were placed in a 2 L jacketed reactor and diluted with 1200 g of ethyl acetate. The reaction temperature was set at 60° C. to 70° C., and stirring was performed for about 30 minutes to 1 hour. 0.28 g of n-dodecyl mercaptan was further added thereto, and stirring was further performed for about 30 minutes. Thereafter, 0.32 g of AIBN as a polymerization initiator was added thereto, and polymerization was performed at the reaction temperature for 4 hours or more, and maintained until the residual acrylate content became less than 1% to obtain a (meth)acrylate-based polyol (co)polymer having a hydroxyl functional group in a branched chain (the weight average molecular weight of about 600,000, the OH equivalent of 1802 g/equivalent).

Preparation Example 2: Preparation of Non-Reactive Low Refractive Material

[0101] 20.51 g of 2,2′-((oxybis(1,1,2,2-tetrafluoroethane-2,1-diyl))bis(oxy))bis(2,2-difluoroethan-1-ol was placed in a 1000 ml flask, dissolved in 500 g of tetrahydrofuran, and 4.40 g of sodium hydride (60% dispersion in mineral oil) was gently 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 all of the reactants were confirmed to be consumed by 1H NMR, the reaction solvent was completely removed under reduced pressure. The organic layer was collected by extracting three times with 300 g of dichloromethane, which was then filtered with magnesium sulfate, and all dichloromethane was removed under reduced pressure to obtain 29 g of a liquid product having a purity of 95% or more at a yield of 98%.

Examples and Comparative Examples: Preparation of Photopolymer Composition

[0102] As shown in Table 1 or Table 2 below, the (meth)acrylate-based polyol (co)polymer having a hydroxyl functional group in a branched chain of Preparation Example 1, the siloxane-based polymer containing a silane (Si—H) functional group, the non-reactive low-refractive material of Preparation Example 2, Safranin O (dye, manufactured by Sigma-Aldrich), silicone-based reactive additive (Tego Rad 2500) and methyl isobutyl ketone (MIBK) was mixed with light blocked, and stirred with a paste mixer for about 10 minutes. Karstedt's (Pt based) catalyst was added for matrix crosslinking, and liquid crosslinking was performed at room temperature for at least 30 minutes. After liquid crosslinking of the matrix, a photoreactive monomer (high refractive acrylate, refractive index 1.600, HR6022 [Miwon Specialty Chemical Co., Ltd.]) and a Borate V (Spectra Group) initiator were added to the coating solution, and further mixed for 5 minutes or more.

[0103] The coating solution was coated to a thickness of 10 to 15 μm on a TAC substrate having a thickness of 80 μm using a meyer bar, and dried at 60° C. within 10 minutes.

Experimental Examples: Holographic Recording

[0104] (1) The photopolymer-coated surfaces prepared in each of Examples and Comparative Examples were laminated on a slide glass, and fixed so that a laser first passed through the glass surface at the time of recording.

[0105] (2) Measurement of diffraction efficiency (η)

[0106] A holographic recording was done via interference of two interference lights (reference light and object light), and a transmission-type recording was done so that the two beams were incident on the opposite side of the sample. The diffraction efficiencies change with the incident angle of the two beams, and become non-slanted when the incident angles of the two beams are the same. In the non-slanted recording, the diffraction grating is generated parallel to the film because the incident angles of the two beams are equal on the normal basis.

[0107] The recording (reference light=30° and object light=40°) was done in a transmission-type non-slanted manner using a laser with a wavelength of 532 nm, and the diffraction efficiency (η) was calculated according to the following Equation 1.

[00001]$\begin{array}{cc}\eta =\frac{P_D}{P_D+P_T}& \left[\mathrm{Equation}1\right]\end{array}$

[0108] in Equation 1, η is a diffraction efficiency, P.sub.D is an output amount (mW/cm.sup.2) of the diffracted beam of a sample after recording, and P.sub.T is an output amount (mW/cm.sup.2) of the transmitted beam of the recorded sample.

TABLE-US-00001 TABLE 1 Measurement results of Experimental Examples of the photopolymer compositions (unit: g) of Examples and the hologram recording medium prepared therefrom Exam- Exam- Exam- Exam- Category ple 1 ple 2 ple 3 ple 4 (meth)acrylate- Preparation 32.6 31.3 33.3 29.7 based Example 1 copolymer Silane(SiH) Poly(methylhydro- 1.9 group- siloxane), containing trimethylsilyl siloxane- terminated based (Sigma-Aldrich, polymer Mn = 390) Poly(dimethyl- 3.2 siloxane-co- methyl- hydrosiloxane), trimethylsilyl terminated (Sigma-Aldrich, Mn = 950) Poly(methylhydro- 1.2 siloxane)(Sigma- Aldrich, Mn = 1700~3200) Poly(dimethyl- 4.8 siloxane), hydride terminated(Sigma- Aldrich, Mn = 580) Photoreactive HR6022 34.5 34.5 34.5 34.5 monomer Dye safranin O 0.2 0.2 0.2 0.2 Borate salt Borate V 0.3 0.3 0.3 0.3 Non-reactive Preparation 30 30 30 30 low refractive Example 2 material (P3) Catalyst Karstedt(Sigma- 0.003 0.003 0.003 0.003 Aldrich) Additive Tego Rad 2500 0.3 0.3 0.3 0.3 Solvent MIBK 234 234 234 234 Coating thickness (unit: μm) 15 15 15 15 Diffraction efficiency (%) 95 80 70 90

TABLE-US-00002 TABLE 2 Measurement results of Experimental Examples of the photopolymer compositions of Comparative Examples and the hologram recording medium prepared therefrom Compara- Compara- Compara- tive tive tive Category Example 1 Example 2 Example 3 Polymer Polyvinyl acetate 27.6 matrix (Sigma-Aldrich/ Mw = 50,000) Cellulose acetate 27.6 Butyrate(Sigma- Aldrich/Mw = 70,000) Cellulose acetate 27.6 propionate (Sigma- Aldrich/Mw = 75000) Photoreactive HR6022 41.4 41.4 41.4 monomer Dye safranin O 0.2 0.2 0.2 Borate salt Borate V 0.3 0.3 0.3 Non-reactive Preparation 30 30 30 low refractive Example 2 material (P3) Additive Tego Rad 2500 0.5 0.5 0.5 Solvent MIBK 200 200 200 Coating thickness (unit: μm) 15 15 15 Diffraction efficiency (%) 40 10 0

[0109] As seen from Table 1 and Table 2 above, the photopolymer composition to which the crosslinked matrix of the (meth)acrylate-based polyol (co)polymer having a hydroxyl functional group in a branched chain of Preparation Example 1 and a polymer containing a silane (S—H) group was applied showed a recording efficiency of 70% or more at a coating thickness of 15 μm.

[0110] On the contrary, the photopolymer compositions to which non-crosslinked commercial polymer products was applied as a matrix showed relatively low diffraction efficiency of 40% or less.