Composition for holographic recording medium and holographic recording medium

Abstract

The present application relates to a composition for holographic recording media and a holographic recording medium using the composition for holographic recording media. The present application designs the structure of a base film-forming material contained in the composition for holographic recording media, reduces the refractive index of the base to increase the overall refractive index difference, and thus prepares a high-performance VHG.

Description

Technical Field

[0001] The present application relates to the technical field of holograms, and more particularly to a composition for a holographic recording medium and a holographic recording medium using the composition for a holographic recording medium. Background Art

[0002] Holographic technology refers to an optical information technology that uses the principle of optical coherence to record the amplitude, phase and other optical properties of light waves. It is widely used in the fields of holographic anti-counterfeiting and data storage. In this process, as the carrier of holographic recording, the holographic recording medium is particularly critical. It mainly converts the image information into the difference in structure between the exposure area and the non-exposure area through the difference in refractive index modulation of the material under photopolymerization reaction, and restores the stored information through the principle of diffraction imaging. Therefore, the ideal holographic recording material should have high refractive index modulation, wide spectral response range, excellent photosensitivity, low haze, and also good stability, excellent processing performance and cheap raw materials.

[0003] The typical holographic recording media at present mainly include: silver halide emulsion, dichromated gelatin, photodegradable polymer, photoconductive thermoplastic material, photoisomerized material, photorefractive material (including liquid crystal), metasurface material, photopolymer, etc. Among them, the post-processing process of silver halide emulsion is complicated and it is easy to produce a large amount of waste liquid to pollute the environment; dichromated gelatin, photodegradable polymer, photoconductive thermoplastic material and photoisomerized material have the problem of low photosensitivity and refractive index modulation; photorefractive material usually requires an additional external electric field, the equipment is complex and the safety is poor; metasurface material has the problem of difficult construction and complex process. As a result, these media cannot prepare high-performance volume holographic grating (VHG). In contrast, photopolymer not only has the advantages of high photosensitivity, high resolution and good light transmittance, but also has excellent process performance, and has gradually become the most potential recording medium in the field of volume holographic recording devices.

[0004] Usually, the formulation of photopolymer mainly includes substances such as photoinitiator system, film-forming resin, recording monomer and other additives. Among them, the absorption characteristics of the photoinitiator system and the quantum yield of the generated free radicals determine the speed of the photopolymerization reaction; the film-forming resin is used as a substrate, on the one hand, it provides mechanical support for the holographic recording medium, and on the other hand, it forms a refractive index difference with the recording monomer; the recording monomer provides a high refractive index; other additives include toughening agents, leveling agents, etc., which play a role in assisting film formation or inhibiting shrinkage. In order to prepare high-performance VHG, a recording monomer with a higher refractive index is usually required. The problem brought about by this is that the solubility of the high-refractive monomer in the substrate is limited, and the improvement of the overall performance is limited.

[0005] In view of this, the present invention designs the structure of the substrate from the perspective of the difference in refractive index between the substrate and the recording monomer, and improves the overall refractive index difference by reducing the refractive index of the substrate, thereby preparing a high-performance VHG. Summary of the invention

[0006] The object of the present application is to provide a composition for a holographic recording medium and a holographic recording medium using the composition for a holographic recording medium, so as to improve at least part of the above-mentioned technical problems.

[0007] To achieve the above-mentioned purpose, as one aspect of the present invention, a composition for holographic recording media is provided, and the composition for holographic recording media comprises the following components: a substrate film-forming substance, an active monomer, a photoinitiator, and a plasticizer. In one embodiment of the present invention, the substrate film-forming substance is a compound having a group selected from an aminoester group, an amide group, a urea group, and an epoxy group, or any combination thereof. In a preferred embodiment of the present invention, the film-forming substrate substance is a compound having two or more methyl carbamate structures. In addition, in order to increase the refractive index difference with the recording monomer, a special structural design of the film-forming substrate substance is required. In the present invention, the refractive index of the substrate is regulated by introducing fluorine element, and the fluorine element content and the molecular weight of the substrate are controlled. The substrate film-forming substance has a general structure as shown below: , where R 2 C 1 -C 10 The carbon chain may be linear, cyclic, branched or heterocyclic; R 1 and R 3 Independently of each other, C 1 -C 25 The carbon chain of R 1 and R 3 At least one of the organic carbon chains is a fluorine-containing carbon chain, preferably a primary carbon chain with polyfluorine substitution; and the mass fraction of fluorine element is 5-40%; preferably 10%-30%; and the synthesis can be prepared by the reaction of isocyanate with polyol / fluorine-modified polyol. It should be noted that the functionality of the selected isocyanate should be greater than the functionality of the selected polyol, and the content of isocyanate should be excessive.

[0008] In one embodiment of the present invention, the active monomer is a C 4 -C 20 In a preferred embodiment of the present invention, the active monomer is an acrylate substance having an allophanate or urethane structure. In a preferred embodiment of the present invention, in order to expand the refractive index difference with the substrate film-forming material, the refractive index of the active monomer is ≥1.5.

[0009] As a sensitizing substance at a certain wavelength, the photoinitiator has a very important influence on the photosensitivity of the material in holographic technology, which is subject to the absorption of a specific wavelength. In one embodiment of the present invention, the photoinitiator is a compound known per se and commercially available on the market. Taking a light source with a wavelength of 520nm as an example, the photoinitiator that can be selected is a combination of substances such as rose bengal, rhodamine, and N-aminoglycine or ethylenediamine, or a combination of boron-containing quaternary ammonium salt and rose bengal.

[0010] In order to facilitate subsequent processing, some small molecules with high boiling points may be introduced as plasticizers in the present invention. In a preferred embodiment of the present invention, the plasticizer is a plasticizer with a boiling point greater than 200 degrees Celsius. In a preferred embodiment of the present invention, the plasticizer is dioctyl phthalate (DOP) or dibutyl phthalate (DBP). Without wishing to be bound by theory, it is believed that the composition for holographic recording media may also contain a catalyst for matrix reaction known to those skilled in the art.

[0011] In addition, as another aspect of the present invention, the various material components in the holographic recording medium composition have content requirements. In a preferred embodiment of the present invention, based on the total weight of the holographic recording medium composition, the content of the substrate film-forming material is 15%-60%, preferably 30%-50%; the content of the active monomer is 20%-50%, preferably 35%-40%; the content of the photoinitiator and the co-initiator is 0.01%-1%, preferably 0.1%-0.3%; the content of the plasticizer is 2%-20%, preferably 2%-8%.

[0012] The present application also relates to a holographic recording medium prepared from the composition for holographic recording medium of the present invention.

[0013] Beneficial effects of the present invention:

[0014] The present invention designs the structure of the substrate from the perspective of the difference in refractive index between the substrate and the recording monomer, which can significantly improve the refractive index modulation and is relatively easy to operate; the significance of improving the refractive index modulation is that it can significantly improve the resolution and clarity of optical waveguide components and improve the comfort of customers. The overall refractive index difference is improved by reducing the refractive index of the substrate, thereby preparing a high-performance VHG. By fluorinating and grafting the substrate film-forming material, it is found that the refractive index of the unmodified substrate film-forming material is significantly reduced, and it has a certain effect on the diffraction efficiency and refractive index modulation of the prepared holographic recording medium. The inventors also found that the fluorination modification of the substrate film-forming material is not simply linearly related to the number of fluorine atoms. Only under a specific range of fluorination modification conditions can the ideal effects of the diffraction efficiency and refractive index modulation of the prepared holographic recording medium be achieved. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are only embodiments of a part of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0016] Example 1: Under the red light protection environment, 30-35% of polyether diol (molecular weight of 2000), 40% of acrylate active monomer and 0.1% of rose bengal + 0.3% of N-phenylglycine are pre-mixed, and then plasticizer DOP is added. After mixing evenly, 8-12% of triisocyanate monomer and 0.1% of organic tin are added and mixed again to obtain a clear photosensitive liquid, and then 5-10% of modified compounds (undecylfluoro-n-hexane-1-ol) with different fluorine contents are added to modify the substrate. Then, under the red light protection, a certain amount of the above-mentioned photosensitive liquid is sucked and siphoned into a glass box of a specific thickness (the box thickness is 10 μm) to form a film. Finally, after the siphoning is completed, the glass box is protected from light with tin foil, placed in an oven, and dried at 72°C for 3 hours to obtain a holographic recording medium.

[0017] Example 2: Under the red light protection environment, 30-35% of polyether diol (molecular weight of 2000), 40% of acrylate active monomer and 0.1% of rose bengal + 0.3% of N-phenylglycine are pre-mixed, and then plasticizer DOP is added. After mixing evenly, 8-12% of triisocyanate monomer and 0.1% of organic tin are added and mixed again to obtain a clear photosensitive liquid, and then 5-10% of modified compounds with different fluorine contents (hexafluorobutanol) are added to modify the substrate. Then, under the red light protection, a certain amount of the above-mentioned photosensitive liquid is sucked and siphoned into a glass box of a specific thickness (the box thickness is 10μm) to form a film. Finally, after the siphoning is completed, the glass box is protected from light with tin foil, placed in an oven, and dried at 72°C for 3h to obtain a holographic recording medium.

[0018] Example 3: Under the red light protection environment, 30-35% of polyether diol (molecular weight of 2000), 40% of acrylate active monomer and 0.1% of rose bengal + 0.3% of N-phenylglycine are pre-mixed, and then plasticizer DOP is added. After mixing evenly, 8-12% of triisocyanate monomer and 0.1% of organic tin are added and mixed again to obtain a clear photosensitive liquid, and then 5-10% of modified compounds with different fluorine contents (2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctan-1-ol) are added to modify the substrate. Then, under the red light protection, a certain amount of the above-mentioned photosensitive liquid is sucked and siphoned into a glass box of a specific thickness (the box thickness is 10μm) to form a film. Finally, after the siphoning is completed, the glass box is protected from light with tin foil, placed in an oven, and dried at 72°C for 3h to obtain a holographic recording medium.

[0019] Comparative Example 1: Under a red light protection environment, 35-45% of polyether diol (molecular weight of 2000), 40% of acrylate active monomer and 0.1% of rose bengal + 0.3% of N-phenylglycine are pre-mixed, and then plasticizer DOP is added. After mixing evenly, 5-10% of triisocyanate monomer and 0.1% of organic tin are added thereto and mixed again to obtain a clear photosensitive liquid. Then, under red light protection, a certain amount of the above-mentioned photosensitive liquid is absorbed and siphoned into a glass box of a specific thickness (the box thickness is 10 μm) to form a film. Finally, after the siphoning is completed, the glass box is protected from light with tin foil, placed in an oven, and dried at 72° C. for 3 hours to obtain a holographic recording medium.

[0020] The diffraction efficiency was tested using a UV spectrophotometer; the refractive index was tested using an Abbe refractometer.

[0021] Test Results

[0022] Table 1: Test results of Examples 1-3 and Comparative Examples

[0023]

[0024] As can be seen from Table 1, the holographic recording media in Examples 1-3 have significantly lower refractive indices than those of the unmodified substrate film-forming materials due to the fluorination grafting modification of the substrate film-forming materials, and have certain effects on the diffraction efficiency and refractive index modulation of the prepared holographic recording media. The reason is that by reducing the refractive index of the substrate, the refractive index difference with the active monomer can be effectively enlarged. At the same time, through the comparison of Examples 1-3, it can be found that the fluorination modification of the substrate film-forming material is not simply linearly related to the number of fluorine atoms, because as the number of fluorine atoms grafted on the substrate film-forming material increases to a certain value, the compatibility of the substrate film-forming material with the active monomer polymerization reactant will be reduced, resulting in phase separation of the two phases, thereby increasing the haze of the holographic recording medium and affecting the diffraction efficiency and refractive index modulation of the medium.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A composition for a holographic recording medium, characterized in that: It contains a substrate film-forming substance, wherein the substrate film-forming substance has a general structure as shown below: Where R2 is C1-C 10 The carbon chain is linear, cyclic, branched or heterocyclic; R1 and R3 are independently C1-C 25 carbon chain, and at least one of R1 and R3 is an organic carbon chain containing fluorine atoms; at least one of R1 and R3 is a primary carbon chain with polyfluorine substitution; the mass fraction of fluorine element in the base film-forming material is 5% to 40%.

2. The composition for holographic recording media according to claim 1, wherein The substrate film-forming material is prepared by reacting isocyanate with polyol or fluorine-modified polyol.

3. The composition for holographic recording media according to claim 1, wherein It also includes: Reactive monomers; a photoinitiator; and Plasticizer.

4. The composition for holographic recording media according to claim 3, wherein The active monomer is a C4-C 20 Carbon chain; and / or The photoinitiator is a combination of Rose Bengal or rhodamine and N-aminoglycine or ethylenediamine, or a combination of a boron-containing quaternary ammonium salt and Rose Bengal; and / or The plasticizer has a boiling point greater than 200 degrees Celsius.

5. The composition for holographic recording media according to claim 3 or 4, characterized in that The active monomer is an acrylate substance having an allophanate or urethane structure; and / or The plasticizer is dioctyl phthalate or dibutyl phthalate.

6. The composition for holographic recording media according to claim 3 or 4, characterized in that The refractive index of the active monomer is ≥1.

5.

7. The composition for holographic recording media according to claim 3 or 4, characterized in that Based on the total weight of the composition for holographic recording media, the content of the substrate film-forming substance is 15%-60%; the content of the active monomer is 20%-50%; the content of the photoinitiator is 0.01%-1%; and the content of the plasticizer is 2%-20%.

8. A holographic recording medium, characterized in that: The holographic recording medium is prepared by the composition for holographic recording medium according to any one of claims 1 to 7.

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