HOLOGRAM MEDIUM AND OPTICAL ELEMENT

Abstract

The present disclosure relates to a hologram medium comprising: a polymer substrate including a polymer resin in which a silane-based functional group is located in a main chain or a branched chain, wherein a fine pattern is formed on at least one surface of the polymer substrate, and an optical element.

Claims

1. A hologram medium comprising: a polymer substrate including a polymer resin comprising a silane-based functional group in a main chain or a branched chain, the polymer substrate having a fine pattern is formed on at least one surface.

2. The hologram medium according to claim 1, wherein the fine pattern has two or more fine protrusions in which a maximum value of the height and a minimum value of the height are alternately repeated based on a cross section of the polymer substrate, and wherein a standard error of the distance in a cross-sectional direction of the polymer substrate between the maximum value of the height of one fine protrusion and the minimum value of the height of an adjacent fine protrusion is 20 nm or less.

3. The hologram medium according to claim 2, wherein the distance in the cross-sectional direction of the polymer substrate between the maximum value of the height of the one fine projection and the minimum value of the adjacent fine projection is 0.2 m to 2 m.

4. The hologram medium according to claim 2, having an amplitude of 5 to 50 nm, the amplitude being defined as a difference between the maximum value of the height of the one fine projection and the minimum value of the height of the adjacent fine projection.

5. The hologram medium according to claim 1, wherein the polymer substrate includes a cross-linked product between a polymer matrix including a (meth)acrylate-based (co)polymer having a silane-based functional group in a branched chain and a silane crosslinking agent; and a photoreactive monomer.

6. The hologram medium according to claim 5, wherein the (meth)acrylate-based (co)polymer comprises the silane-based functional group having an equivalent weight of 300 g/eq to 2000 g/eq.

7. The hologram medium according to claim 5, wherein the polymer matrix includes 10 parts by weight to 90 parts by weight of the silane crosslinking agent based on 100 parts by weight of the (meth)acrylate-based (co)polymer.

8. The hologram medium according to claim 5, wherein the silane crosslinking agent includes a linear poly ether main chain having a weight average molecular weight of 100 to 2000 and a silane functional group bonded to a terminal or branched chain of the main chain.

9. The hologram medium according to claim 8, wherein a bond between the silane-based functional group and the polyether main chain is a urethane bond.

10. The hologram medium according to claim 5, wherein the silane crosslinking agent comprises a silane-based functional group in an equivalent weight of 200 g/eq to 1000 g/eq.

11. The hologram medium according to claim 5, wherein the photoreactive monomer comprises a polyfunctional (meth)ac monomer or a monofunctional (meth)acrylate monomer.

12. The hologram medium according to claim 5, wherein the photoreactive monomer has a refractive index of at least 1.5.

13. The hologram medium according to claim 5, wherein the photopolymer composition further comprises a fluorine-based compound.

14. The hologram medium according to claim 13, wherein the fluorine-based compound includes at least one functional group selected from an ether group, an ester group and an amide group, and at least two difluoromethylene groups.

15. The hologram medium according to claim 13, wherein the fluorine-based compound has a refractive index of less than 1.45.

16. The hologram medium according to claim 5, wherein the polymer matrix has a refractive index of 1.46 to 1.53.

17. An optical element comprising the hologram medium of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] FIG. 1 is a line profile of the shape of the surface of the hologram medium of Example 1 measured using an atomic force microscope (AFM).

[0119] FIG. 2 is a line profile of the shape of the surface of the hologram medium of Example 2 measured using an atomic force microscope (AFM).

[0120] FIG. 3 is a line profile of the shape of the surface of the hologram medium of Example 3 measured using an atomic force microscope (AFM).

[0121] FIG. 4 is a line profile of the shape of the surface of the hologram medium of Example 4 measured using an atomic force microscope (AFM).

[0122] FIG. 5 is a line profile of the shape of the surface of the hologram medium of Comparative Example 1 measured using an atomic force microscope (AFM).

[0123] FIG. 6 is a line profile of the shape of the surface of the hologram medium of Comparative Example 2 measured using an atomic force microscope (AFM).

[0124] FIG. 7 is a line profile of the shape of the surface of the hologram medium of Comparative Example 3 measured using an atomic force microscope (AFM).

[0125] FIG. 8 is a line profile of the shape of the surface of the hologram medium of Comparative Example 4 measured using an atomic force microscope (AFM).

[0126] Hereinafter, the present disclosure will be described in more detail by way of the following 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 Method of a (Meth)Acrylate-Based (Co)Polymer in which a Silane-Based Functional Group is Located in a Branch Chain

[0127] 154 g of butyl acrylate and 46 g of KBM-503 methacryloxypropyltrimethoxysilane) were added to a 2 L jacket reactor and diluted with 800 g of ethyl acetate. The reaction temperature was set at 60 to 70 C., and stirring was carried out for about 30 minutes to 1 hour. 0.02 g of n-dodecyl mercaptan was further added, and stirring was further carried out for about 30 minutes. Subsequently, 0.06 g of AIBN as a polymerization initiator was added and the polymerization was carried out at the reaction temperature for 4 hours or more and maintained until the residual acrylate content became less than 1%, thereby preparing a (meth)acrylate-based (co)polymer in which a silane-based functional group was located in a branch chain (weight average molecular weight of about 500,000 to 600,000, Si(OR).sub.3 equivalent weight of 1019 g/eq).

Preparation Example 2: Preparation Method of a (Meth)Acrylate-Based (Co)Polymer in which a Silane-Based Functional Group is Located in a Branch Chain

[0128] 180 g of butyl acrylate and 120 g of KBM-503 methacryloxypropyltrimethoxysilane) were added to a 2 L jacket reactor and diluted with 700 g of ethyl acetate. The reaction temperature was set at 60 to 70 C., and stirring was carried out for about 30 minutes to 1 hour. 0.03 g of n-dodecyl mercaptan was further added, and stirring was further carried out for about 30 minutes. Subsequently, 0.09 g of AIBN as a polymerization initiator was added and the polymerization was carried out at the reaction temperature for 4 hours or more and maintained until the residual acrylate content became less than 1%, thereby preparing a (meth)acrylate-based (co)polymer in which a silane-based functional group was located in a branch chain (weight average molecular weight of about 500,000 to 600,000, Si(OR).sub.3 equivalent weight=586 g/eq).

Preparation Example 3: Preparation Method of a (Meth)Acrylate-Based (Co)Polymer in which a Silane-Based Functional Group is Located in a Branch Chain

[0129] 255 g of butyl acrylate and 45 g of KBM-503 methacryloxypropyltrimethoxysilane) were added to a 2 L jacket reactor and diluted with 700 g of ethyl acetate. The reaction temperature was set at 60 to 70 C., and stirring was carried out for about 30 minutes to 1 hour. 0.03 g of n-dodecyl mercaptan was further added, and stirring was further carried out for about 30 minutes. Subsequently, 0.09 g of AIBN as a polymerization initiator was added and the polymerization was carried out at the reaction temperature for 4 hours or more and maintained until the residual acrylate content became less than 1%, thereby preparing a (meth)acrylate-based (co)polymer in which a silane-based functional group was located in a branch chain (weight average molecular weight of about 500,000 to 600,000, Si(OR).sub.3 equivalent weight of 1562 g/eq).

Preparation Example 4: Preparation Method of Silane Crosslinking Agent

[0130] In a 1000 ml flask, 19.79 g of KBE-9007 (3-isocyanatopropyltriethoxysilane), 12.80 g of PEG-400 and 0.57 g of DBTDL were added and diluted with 300 g of tetrahydrofuran. The mixture was stirred at room temperature until it was confirmed by TLC that all the reactants were consumed, and then the reaction solvent was completely removed under reduced pressure.

[0131] 28 g of a liquid product having a purity of 95% or more was separated in a yield of 91% through column chromatography under a developing solution condition of dichloromethane:methyl alcohol=30:1, thereby obtaining the above-mentioned silane crosslinking agent.

Preparation Example 5: Preparation Method of Non-Reactive Low Refractive Index Material

[0132] In a 1000 ml flask, 20.51 g of 2,2-((oxybis(1,1,2,2-tetrafluoroethane-2,1-diyl))bis(oxy))bis(2,2-difluoroethan-1-ol) was added and then dissolved in 500 g of tetrahydrofuran. 4.40 g of sodium hydride (60% dispersion in mineral oil) was carefully added over 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 by .sup.1H NMR that all the reactants were consumed, the reaction solvent was completely removed under reduced pressure. The organic layer was collected by extracting with 300 g of dichloromethane three times, and filtered with magnesium sulfate, and then the pressure was reduced to remove all the dichloromethane to obtain 29 g of a liquid product having a purity, of 95% or more in a yield of 98%.

Example: Preparation of Photopolymer Composition and Hologram Medium

[0133] 1. Preparation of Photopolymer Composition

[0134] As shown in Table 1 or Table 2 below, the silane polymers obtained in Preparation Examples 1 to 3, photoreactive monomer (high refractive index acrylate, refractive index 1.600, MR 6022 [Miwon]), the non-reactive low refractive index material of Preparation Example 5, tributyl phosphate ([TBP], molecular weight 266.31, refractive index 1.424, manufactured by Sigma-Aldrich), Safranin O (dye, manufactured by Sigma-Aldrich), Ebecryl P-115 (SK entis), Borate V (Spectra Group), Irgacure 250 (BASE), silicone-based reactive additive (Tego Rad 2500) and methyl isobutyl ketone (MIBK) were mixed in a state cutting off the light, and stirred with a paste mixer for about 10 minutes to obtain a transparent coating solution.

[0135] The silane crosslinking agent obtained in Preparation Example 4 was added to the coating solution, and further stirred for about 10 minutes. Subsequently, 0.02 g of DBTDL as a catalyst was added to the coating solution, stirred for about 1 minute, and then coated in a thickness of 6 m onto a TAC substrate with a thickness of 80 m using a Meyer bar and dried at 40 C. for 1 hour.

[0136] Then, the sample was allowed to stand for 24 hours or more in a dark room under constant temperature and humidity conditions of about 25 C. and 50% RH.

[0137] 2. Preparation of Hologram Medium

[0138] (1.) The above-prepared photopolymer-coated surfaces were laminated on a slide glass, and fixed so that a laser first passed through the glass surface at the time of recording.

[0139] (2) Measurement of Diffraction Efficiency ()

[0140] 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. 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. 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.

[0141] The recording (2=45) was done in a transmission-type non-slanted manner using a laser with a wavelength of 532 nm, and the diffraction efficiency () was calculated according to the following general formula 1.

[00001]$\begin{array}{cc}=\frac{P_D}{P_D+P_T}& \left[\mathrm{General}.Math..Math.\mathrm{Formula}.Math..Math.1\right]\end{array}$

[0142] in the general formula 1, 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.

[0143] (3) Measurement of Refractive Index Modulation Value (n)

[0144] The lossless dielectric grating of the transmission-type hologram can calculate the refractive index modulation value (n) from the following general formula 2.

[00002]$\begin{array}{cc}\left(\mathrm{DE}\right)={\sin }^2\left(\sqrt{v^2}\right)={\sin }^2\left(\frac{n.Math..Math..Math..Math.\mathrm{nd}}{\cos .Math..Math.}\right)& \left[\mathrm{General}.Math..Math.\mathrm{Formula}.Math..Math.2\right]\end{array}$

[0145] in the general formula 2, d is a thickness of the photopolymer layer, n is a refractive index modulation value, (DE) is a diffraction efficiency, and is a recording wavelength.

[0146] (4) Measurement of the Loss Amount of Laser (I.sub.loss)

[0147] The loss amount of laser (I.sub.loss) can be calculated from the following general formula 3.

I.sub.loss=1{(P.sub.D+P.sub.T)/I.sub.O}[General Formula 3]

[0148] in the general formula 3, P.sub.D is an output amount (mW/cm.sup.3) of the diffracted beam of the sample after recording, PT is an output amount (mW/cm.sup.3) of the transmitted beam of the recorded sample, and I.sub.0 is an intensity of the recording light.

[0149] (5) Surface Observation of the Hologram Medium

[0150] The shape and size of the linear pattern formed on one surface of the hologram medium obtained in Examples were measured using an atomic force microscope (XE7) manufactured by Park Systems. Then, the distance between the adjacent minimum and maximum values was measured through a line profile from the confirmed surface shape.

[0151] At this time, in the measurement result, the minimum value means a point where the y-axis value decreases and then increases, the maximum value means a point at which the y-axis value increases and then decreases, and adjacent means the most adjacent maximum value (or minimum value) with a height difference of 5 nm or more from the minimum value or maximum value).

[0152] As for the standard error of the adjacent minimum and maximum values, the distance between the adjacent minimum and maximum values having a height difference of 5 inn or more was measured from the line profile of the surface profile measured by atomic force microscopy, and the standard error was calculated according to the following general formula 1.

SE=/{square root over (n)}[General Formula 1]

[0153] in the general formula 1, SE is a standard error, is a standard deviation, and n is a number.

[0154] FIGS. 1 to 4 are line profiles of the shapes of the surfaces of the hologram media of Examples 1 to 4 measured using an atomic force microscope.

TABLE-US-00001 TABLE 1 Experimental results of the photopolymer composition (unit: g) of Examples and the holographic recording medium prepared therefrom Category Example 1 Example 2 Example 3 Example 4 (Meth) acrylate- Preparation 23.1 23.1 based copolymer Example 1 Preparation 19.3 Example 2 Preparation 25.4 Example 3 Linear silane Preparation 8.4 8.4 12.3 6.1 crosslinking agent Example 4 Reactive monomer HR6022 31.5 31.5 31.5 31.5 Dye safranin O 0.1 0.1 0.1 0.1 Amine Ebecryl P-115 1.7 1.7 1.7 1.7 Borate salt Borate V 0.3 0.3 0.3 0.3 Onium salt Irgacure 250 0.1 0.1 0.1 0.1 Non-reactive Tributyl 0 17.2 17.2 17.2 plasticizer phosphate (TBP) Non-reactive low Preparation 34.4 17.2 17.2 17.2 refractive Example 5 material(P3) Catalyst DBTDL(dibutyltin 0.02 0.02 0.02 0.02 dilaurate) Additive Tego Rad 2500 0.3 0.3 0.3 0.3 Solvent MIBK 300 300 300 300 Coating thickness(unit: m) 6 6 6 6 I.sub.loss (%) 25 19 21 20 Standard error (SE) 5.72 nm 2.26 nm 6.72 nm 4.30 nm Diffraction efficiency () 67% 69% 80% 46% n 0.025 0.027 0.030 0.022 *Non-reactive plasticizer: Tributyl phosphate (molecular weight of 266.31, refractive index of 1.424, purchased from Sigma-Aldrich)

Comparative Example: Preparation of Hologram Media

[0155] (1) Synthesis of Polyol

[0156] 34.5 g of methyl acrylate, 57.5 g of butyl acrylate, and 8 g of 4-hydroxy butyl acrylate were added to a 2 L jacket reactor, and diluted with 150 g of ethyl acetate. Stirring was performed for about 1 hour while maintaining the temperature of the jacket reactor at 60 to 70 C. Then, 0.035 g of n-dodecyl mercaptan was further added to the reactor, and further stirring was performed for about 30 minutes. Then, 0.04 g of a polymerization initiator AIBN (2,2-azo-bisisobutyronitrile) was added thereto, and polymerized at a temperature of about 70 C. for about 4 hours, and maintained until the content of the residual acrylate monomer became 1% by weight, and thereby the polyol was synthesized. At this time, the obtained polyol had a weight average molecular weight of about 700,000 in terms of polystyrene measured by GPC method, and the OH equivalent measured using KOH titration was 1802 g/OH mol.

[0157] (2) Preparation of Photopolymer Composition

[0158] The polyol of Preparation Example 1, the photoreactive monomer (high refractive acrylate, refractive index of 1.600, HR6022 [Miwon]), safranin O (dye, manufactured by Sigma Aldrich), the non-reactive low refractive material of Preparation Example 5, tributyl phosphate [TBP], molecular weight of 266.31, refractive index of 1.424, manufactured by Sigma Aldrich), Ebecryl P-115 (SK entis), Borate V (Spectra group), Irgacure 250 (BASF), and methyl isobutyl ketone (MIBK) were mixed in a state cutting off the light, and stirred with a paste mixer for about 10 minutes to obtain a transparent coating solution.

[0159] MFA-75X (Asahi Kasei, hexa-functional isocyanate, diluted to 75% by weight in xylene) was added to the coating solution, and further stirred for about 5-10 minutes. DBTDL (dibutyltin dilaurate) as a catalyst was added thereto, stirred for about 1 minute, and then coated in a thickness of 7 m onto a TAC substrate with a thickness of 80 m using a Meyer bar and dried at 40 C. for 1 hour.

[0160] (3) Preparation of Hologram Medium

[0161] A hologram medium was prepared in the same manner as in the above Examples, and the diffraction efficiency (), the refractive index modulation value (n) and the laser loss (I.sub.loss) were measured according to the same method and the same conditions as in Examples.

[0162] (4) Surface Observation of Hologram Media

[0163] In the same manner as in Examples, the shape and size of the linear pattern formed on one surface of the hologram media obtained in Comparative Examples and the surface of the hologram media were measured and observed.

[0164] FIGS. 5 to 8 are line profiles of the shapes of the surfaces of the hologram media of Comparative Examples 1 to 4 measured using an atomic force microscope.

TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Category Example 1 Example 2 Example 3 Example 4 Polyol Preparation 40.1 26.2 26.2 26.2 Example 1 Isocyanate MFA-75X 9.8 6.4 6.4 6.4 Photoreactive HR6022 47.4 31 31 31 monomer Dye safranin O 0.1 0.1 0.1 0.1 Amine Ebecryl P-115 1.7 1.7 1.7 1.7 Borate salt Borate V 0.3 0.3 0.3 0.3 Onium salt Irgacure 250 0.1 0.1 0.1 Non-reactive Tributyl 16.9 16.9 33.8 plasticizer(TBP) phosphate Non-reactive Preparation 16.9 16.9 33.8 low refractive Example 5 material (P3) Catalyst DBTDL(dibutyltin 0.02 0.02 0.02 0.02 dilaurate) Additive Tego Rad 2500 0.5 0.5 0.5 0.5 Solvent MIBK 400 400 400 400 Coating thickness (unit: m) 7 7 7 7 Standard error(SE) 73.92 nm 187.98 nm 232.23 nm 150.50 nm n 0.012 0.010 0.011 0.013 Diffraction efficiency () 25% 19% 22% 28%

[0165] As seen from FIGS. 1 to 4, it was confirmed that in the hologram media of Examples, the standard error of the distance in the cross-sectional direction of the polymer substrate between the maximum value of the height of the one fine protrusion and the minimum value of the height of the adjacent fine protrusion is 20 nm or less. As shown in Tables 1 and 2, it was also confirmed that the hologram media of Examples have a refractive index modulation value (N) of 0.020 or more and a diffraction efficiency of 40% or more.

[0166] In contrast, as seen in FIGS. 5 to 8, it was confirmed that in the hologram media of Examples, the standard error of the distance in the cross-sectional direction of the polymer substrate between the maximum value of the height of the one fine protrusion and the minimum value of the height of the adjacent fine protrusion exceeds 20 nm, and in such hologram media, image distortion may occur or additional scattering or interference of diffracted light may occur, and diffraction efficiency may also decrease. Specifically, as shown in Tables 1 and 2, it was confirmed that the photopolymer-coated films provided by the compositions of Comparative Examples have a relatively low diffraction efficiency of 30% or less and a refractive index modulation value (n) of 0.015 or less as compared with Examples.