Photopolymer composition

Abstract

The present invention relates to a photopolymer composition comprising: a polymer matrix or a precursor thereof including a reaction product of a polyol including a polyrotaxane compound and a compound containing at least one isocyanate group; a photoreactive monomer; and a photoinitiator. The present invention also relates to a hologram recording medium produced from the photopolymer composition, an optical element comprising the hologram recording medium, and a holographic recording method using the photopolymer composition.

Claims

1. A photopolymer composition comprising: a polymer matrix or a precursor thereof including a reaction product of a polyol and a compound containing at least two isocyanate groups, wherein the polyol includes a polyrotaxane compound comprising a cyclic compound to which a lactone-based compound is bonded, a linear molecule penetrating the cyclic compound, and a blocking group arranged at both ends of the linear molecule, and wherein the blocking group prevents the cyclic compound from escaping; a photoreactive monomer; and a photoinitiator, wherein the compound containing at least two isocyanate groups includes an aliphatic, cycloaliphatic, aromatic or aromatic-aliphatic di-isocyanate, tri-isocyanate or poly-isocyanate; or oligo-isocyanate or poly-isocyanate of diisocyanate or triisocyanate having urethane, urea, carbodiimide, acylurea, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione or iminooxadiazinedione structures, wherein the photoreactive monomer includes a polyfunctional (meth)acrylate monomer or a monofunctional (meth)acrylate monomer, and wherein the polymer matrix or the precursor thereof is present in an amount of 20% to 80% by weight, the photoreactive monomer is present in an amount of 20% to 60% by weight, and the photoinitiator is present in an amount of 0.1% to 15% by weight.

2. The photopolymer composition of claim 1, wherein the lactone-based compound includes a lactone-based compound having 3 to 12 carbon atoms or a polylactone-based compound containing a lactone-based repeating unit having 3 to 12 carbon atoms.

3. The photopolymer composition of claim 1, wherein the lactone-based compound is directly bonded to the cyclic compound, or is bonded to the cyclic compound via a linear or branched oxyalkylene group having 1 to 10 carbon atoms.

4. The photopolymer composition of claim 1, wherein the cyclic compound includes at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, wherein the linear molecule is a polyoxyalkylene-based compound or a polylactone-based compound, and wherein the blocking group includes at least one functional group selected from the group consisting of a dinitrophenyl group, a cyclodextrin group, an adamantane group, a trilyl group, a fluorescein group, and a pyrene group.

5. The photopolymer composition of claim 1, wherein the polyrotaxane compound has a weight average molecular weight of 100,000 to 800,000.

6. The photopolymer composition of claim 1, wherein the polyol including the polyrotaxane compound further includes at least one selected from the group consisting of aliphatic aromatic diols, triols or polyols having 2 to 20 carbon atoms; alicyclic diols, triols or polyols having from 4 to 30 carbon atoms and aromatic diols, triols or polyols having 6 to 30 carbon atoms.

7. The photopolymer composition of claim 1, further comprising a photosensitizing dye.

8. A hologram recording medium produced from the photopolymer composition of claim 1.

9. An optical element comprising the hologram recording medium of claim 8.

10. A holographic recording method comprising selectively polymerizing photoreactive monomers contained in the photopolymer composition of claim 1 using an electromagnetic radiation.

11. The hologram recording medium of claim 8, wherein the hologram recording medium has a refractive index modulation value (Δn) of 0.009 or more and a diffraction efficiency of 85% or more at a thickness of 5 μm to 30 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows 1H NMR data of the polyrotaxane polymer [A1000] that is used as a reactant in Examples.

(2) FIG. 2 shows a gCOSY NMR spectrum confirming the structure of caprolactone contained in the polyrotaxane polymer [A1000] that is used as a reactant in Examples.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) Hereinafter, the present invention will be described in more detail by way of the following examples.

(4) However, these examples are given for illustrative purposes only and are not intended to limit the scope of the present invention thereto.

Example and Comparative Example: Preparation of Photopolymer

(5) As shown in Table 1 below, polyrotaxane polymer [A1000, Advanced Soft Material Inc.], photoreactive monomer, Safranin O (dye, manufactured by Sigma-Aldrich), N-methyldiethanolamine (Sigma-Aldrich), [4-methylphenyl-(4-(2-methylpropyl)phenyl)]iodonium hexafluorophosphate (Irgacure 250) and methyl isobutyl ketone (MIBK) was mixed in a state of cutting off light, and stirred with a paste mixer for about 2 minutes to obtain a transparent coating solution.

(6) 1H NMR data of the polyrotaxane polymer [A1000] that was used as a reactant is shown in FIG. 1, and the structure of the caprolactone bonded to the macrocycle of polyrotaxane was confirmed through the gCOSY NMR spectrum of FIG. 2.

(7) MFA-75X (Asahi Kasei, hexafunctional isocyanate, diluted to 75 wt % in xylene) was added to the coating solution and further stirred for 1 minute. 1.1 g of DBTDL (diluted to 1% solids) as a catalyst was added thereto, stirred for about 1 minute, coated in a thickness of 20 μm onto a polycarbonate (PC) substrate (125 μm) using a Meyer bar, and cured at 40° C. for 30 minutes.

(8) Then. the sample was allowed to stand for 12 hours or more in a dark room under constant temperature and humidity conditions of about 25° C. and 50% RH.

Experimental Example: Holographic Recording

(9) (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.

(10) (2) A holographic recording was done via interference of two interference lights (reference light and object light), and the transmission-type recording was done so that the two beams were incident on the same side of the sample.

(11) The diffraction efficiencies are changed according to the incident angle of the two beams, and become non-slanted when the incident angles of the two beams are the same.

(12) In the non-slanted recording, the diffraction grating is generated vertically to the film because the incident angles of the two beams are the same on the normal basis.

(13) The recording (2θ=45°) 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.

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

(15) 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.

(16) The lossless dielectric grating of the transmission-type hologram can calculate the refractive index modulation value (Δn) from the following Equation 2.

(17) $\begin{array}{cc}\eta \left(\mathrm{DE}\right)={\sin }^2\left(\sqrt{v^2}\right)={\sin }^2\left(\frac{\mathrm{\pi \Delta }\mathrm{nd}}{\mathrm{\lambda cos\theta }}\right)& \left[\mathrm{Equation}2\right]\end{array}$

(18) in Equation 2, d is a thickness of the photopolymer layer, Δn is a refractive index modulation value, η(DE) is a diffraction efficiency, and λ is a recording wavelength.

(19) TABLE-US-00001 TABLE 1 Measurement Results of Diffraction Efficiency and Refractive Index Modulation Value (Δn) of Photopolymer Compositions of Examples and Holographic Recording Medium Prepared Therefrom Example 1 Example 2 Example 3 Example 4 Compound Poly- 10 10 10 10 used rotaxane polymer [A1000] Erythritol 0.25 0.5 Polyol 1 Polyol 2 Polyol 3 MFA-75X 4.3 5.9 6.2 8.0 HR6042 8.8 9.6 9.9 11.0 Safranine 3.1 3.4 3.5 3.8 O N- 4.9 5.4 5.5 6.2 methyl- diethanol amine Irgacure 1.4 1.5 1.5 1.7 250 MIBK 60 66 67 73 Coating thickness 20 20 20 20 Diffraction efficiency 95 92 90 87 (η, %) Δn 0.01 0.01 0.01 0.009

(20) TABLE-US-00002 TABLE 2 Measurement Results of Diffraction Efficiency and Refractive Index Modulation Value (Δn) of Photopolymer Compositions of Comparative Examples and Holographic Recording Medium Prepared Therefrom Comparative Comparative Comparative Example 1 Example 2 Example 3 Compound Polyrotaxane used polymer [A1000] Erythritol Polyol 1 10 Polyol 2 10 Polyol 3 10 MFA-75X 5.4 22.3 5.9 HR6042 9.4 17.8 9.6 Safranine O 3.3 6.2 3.4 N- 5.2 10 5.4 methyl- diethanol amine Irgacure 250 1.4 2.8 1.5 MIBK 64 119 66 Coating thickness 20 20 20 Diffraction efficiency 78 50 75 (η, %) Δn 0.008 0.006 0.008 A1000: polyrotaxane, OH equivalent weight=779 g/mol, Mw=600,000 g/mol, product available at ASMI (Advanced Softmaterial Inc.), Japan. MFA-75X: hexane diisocyanate-based polyisocyanate, NCO content=13.7%, product available at Needfill. Polyol 1: Polycaprolactone diol (bifunctional polyol), OH equivalent weight=625 g/mol. Polyol 1: PEG-diol (polyethyleneglycol diol), OH equivalent weight=150 g/mol. Polyol 3: 7341-X65 product available at Needfill, OH equivalent weight=567 g/mol. HR6042: bifunctional acrylate, product available at Miwon Specialty Chemical Co., Ltd. DBTDL: product available at Sigma-Aldrich, a urethanization catalyst. Dibutyl tin dilaurate. Irganox 250: [4-methylphenyl-(4-(2-methylpropyl)phenyl)]iodonium hexafluorophosp

(21) As shown in Tables 1 and 2 above, it was confirmed that the photopolymer compositions including the polymer matrix using a polyol including a polyrotaxane compound can provide a hologram achieving a high diffraction efficiency of about 85% or more together with a high refractive index modulation value compared to Comparative Examples.

(22) In addition, when the degree of crosslinking of the hologram is further increased by using a polyol of erythritol together with a polyrotaxane compound, it was confirmed that the cross-link point can move in the polymer matrix of the hologram, and that it the hologram has a higher refractive index modulation value and diffraction efficiency than the hologram of Comparative Examples.