Holographic recording medium

Abstract

A holographic recording medium. By means of introducing sulfur atoms and aromatic ring groups having high molar refractivity, the structure of an active monomer is modified such that the refractive index of the active monomer is raised to increase the overall refractive index difference, thereby preparing a high-performance volume holographic grating.

Description

Holographic recording medium TECHNICAL FIELD

[0001] The application belongs to the technical field of recording materials of AR holographic display devices, and particularly relates to a holographic recording medium. BACKGROUND

[0002] Holographic technology refers to an optical information technology using optical coherence principle to record light wave amplitude, phase and the like, and is widely used in fields such as holographic anti-counterfeiting and data storage. In this process, as a carrier for holographic recording, a holographic recording medium is particularly crucial. The holographic recording medium mainly converts object information into differences in structures of exposed areas and non-exposed areas through a refractive index modulation difference of a material under a photopolymerization reaction, and restores the stored information through the principle of diffraction imaging. Therefore, an ideal holographic recording material should have a high refractive index modulation, a wide spectral response range, excellent photosensitivity, low haze, and in addition, should have good stability, excellent processing performance and cheap raw materials.

[0003] Current typical holographic recording media mainly include silver halide emulsion, dichromate gelatin, photodegradable polymer, photoconductive thermoplastic material, photoisomerization material, photorefractive material (including liquid crystal), metasurface material and photopolymer. The silver halide emulsion has a complex post-processing process and is easy to produce a large amount of waste liquid to pollute the environment; the dichromate gelatin, photodegradable polymer, photoconductive thermoplastic material and photoisomerization material have low photosensitivity and low refractive index modulation; the photorefractive material usually needs an additional external electric field, and the equipment is complex and has poor safety; and the metasurface material has difficulties in construction and complex process, so that these media cannot prepare a high-performance volume holographic grating. SUMMARY

[0004] The application aims at the problems existing in the prior art, and provides a holographic recording medium, which comprises a substrate film-forming substance, an active monomer and a photoinitiator.

[0005] The refractive index of the active monomer is not less than a preset value, and the active monomer has the following structural formula:

[0006] In the formula, R1 is a Cn skeleton, which can be a saturated carbon chain and an unsaturated carbon chain, or a benzene ring or other ring structure, wherein n is 1-10; R2 is H or a hydrocarbon or unsaturated acrylate structure containing one or more sulfur atoms; and R3 is H or -CH4.

[0007] As a preferred embodiment of the application, the active monomer comprises one or more of the following structural formulas:

[0008] As a preferred embodiment of the present application, the base film-forming material is at least one of a homopolymer of vinyl acetate, a styrene / butadiene block copolymer, or a polyurethane.

[0009] As a preferred embodiment of the present application, the polyurethane is prepared by reacting a polyether alcohol with a relative molecular mass of 200-4000 with isocyanate.

[0010] As a preferred embodiment of the present application, the content of sulfur atoms is 5-50%.

[0011] As a preferred embodiment of the present application, a toughening agent is further included.

[0012] As a preferred embodiment of the present application, the boiling point of the toughening agent is greater than 200 degrees Celsius.

[0013] As a preferred embodiment of the present application, the content of the base film-forming material is 10-60%; the content of the active monomer is 20-50%; the content of the initiator is 0.01-1%; and the content of the plasticizer is 2-20%.

[0014] As a preferred embodiment of the present application, the content of the base film-forming material is 20-50%; the content of the active monomer is 30-45%; the content of the initiator is 0.1-0.3%; and the content of the plasticizer is 2-8%.

[0015] As a preferred embodiment of the present application, the photoinitiator is a combination of rose Bengal, rhodamine, and n-amino glycine / ethylenediamine, or a combination of a boron-containing quaternary ammonium salt and rose Bengal.

[0016] The present application has the following beneficial effects:

[0017] The holographic recording medium provided by the present application improves the refractive index of the active monomer by introducing sulfur atoms and aromatic ring groups with a large molar refractivity to modify the structure of the active monomer, thereby improving the overall refractive index difference and preparing a high-performance volume holographic grating. DETAILED DESCRIPTION

[0018] For those skilled in the technical field, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application. In the following examples, unless otherwise specified, the specific conditions of the test methods described are generally carried out according to conventional conditions or manufacturer's recommended conditions; raw materials, reagents are commercially available or prepared using public information.

[0019] In the following examples, unless otherwise specified, the reagents and materials used are commercially available.

[0020] The applicant found that the photopolymer not only has the advantages of high photosensitivity, high resolution and good light transmittance, but also has excellent processability, and has gradually become the most potential recording medium in the field of volume holographic recording devices.

[0021] Generally, the photopolymer formula mainly includes a photoinitiating system, a film-forming resin, a recording monomer and other additives, etc. Among them, the absorption characteristics and the quantum yield of free radicals generated by the photoinitiating system determine the speed of photopolymerization reaction; the film-forming resin serves as a substrate film-forming material, which provides mechanical support for the holographic recording medium on the one hand, and forms a refractive index difference with the recording monomer on the other hand; the recording monomer provides a high refractive index; other additives include toughening agents, leveling agents, etc., which play the functions of auxiliary film-forming or shrinkage inhibition, etc. In order to prepare a high-performance volume holographic grating, a recording monomer with a higher refractive index is usually required. According to the relationship between the refractive index of the material and the molar refractivity and molar volume of the monomer revealed by the Lorentz-Lorenz relationship, it is known that introducing atoms or groups with large molar refractivity is one of the effective means to improve the refractive index of the material. The Lorentz-Lorenz formula is used to determine the refractive index of a certain substance and its change process in the medium.

[0022] In view of this, the present application modifies the structure of the active monomer by introducing sulfur atoms and aromatic ring groups with large molar refractivity, thereby improving the refractive index of the active monomer and the overall refractive index difference, so as to prepare a high-performance volume holographic grating.

[0023] The present application aims to provide a holographic recording medium with a high refractive index modulation and a display device to improve at least part of the above technical problems.

[0024] The present application provides a holographic recording medium, comprising: a substrate film-forming material, an active monomer and a photoinitiator.

[0025] The active monomer has a refractive index not less than a preset value, and a structural formula is as follows:

[0026] R1 is an alkane or an aromatic hydrocarbon, the number of carbon atoms in R1 is 1-10; R2 is a hydrogen atom or an alkane or an unsaturated acrylate structure containing one or more sulfur atoms; and R3 is H or CH4.

[0027] Further, R1 is a Cn skeleton, which can be a saturated carbon chain or an unsaturated carbon chain, a benzene ring or other cyclic structure, n is 1-10; R2 is H or a hydrocarbon or an unsaturated acrylate structure containing one or more sulfur atoms; and preferably, the content of sulfur atoms is 5%-50%.

[0028] In the embodiments of the present application, the active monomer has a refractive index not less than 1.6.

[0029] In the embodiments of the present application, the film-forming material is at least one selected from a homopolymer of vinyl acetate, a styrene / butadiene block copolymer and a polyurethane material, and in the present application, a polyurethane material having a methyl carbamate structure is preferably used as a base film-forming material. In addition, in order to ensure that the base film-forming material has certain flexibility and self-supporting property, a polyurethane base film-forming material is preferably prepared by using a polyhydric ether alcohol having a relative molecular mass of 200-4000 and isocyanate.

[0030] In the embodiments of the present application, the high-refractive active monomer can be one or more of the following structures:

[0031] In order to facilitate subsequent processing, as a preferred embodiment of the present application, a toughening agent is further included. The toughening agent is a small molecule material having a high boiling point, and preferably, the boiling point of the toughening agent is greater than 200 DEG C.

[0032] In the embodiments of the present application, the content of each material is required, and the content of the film-forming material is 10%-60%, preferably 20%-50%, the content of the active monomer is 20%-50%, preferably 30%-45%, the content of the initiator is 0.01%-1%, preferably 0.1%-0.3%, and the content of the plasticizer is 2%-20%, preferably 2%-8%, based on the total amount of the composition.

[0033] In the embodiments of the present application, the photoinitiator is a combination of rose red, rhodamine and n-amino glycine / ethylenediamine, or a combination of a boron-containing quaternary ammonium salt and rose red.

[0034] It should be noted that the photoinitiator as a sensitizing substance at a certain wavelength has a very important influence on the photosensitive sensitivity of the material in holographic technology, which is subject to the absorption of a specific wavelength. In the present application, the photoinitiator is a compound known per se and commercially available on the market. Taking a light source with a wavelength of 520 nm as an example, the photoinitiator can be selected from rose red, rhodamine and the like in combination with n-amino glycine / ethylenediamine, or a quaternary ammonium salt containing boron in combination with rose red and the like.

[0035] The preparation method of the high-activity monomer is described in detail below:

[0036] Example 1:

[0037] Preparation of high-refractive monomer 1:

[0038] The active monomer 1 is prepared according to the above chemical synthesis method, wherein the refractive index of the active monomer is 1.63; secondly, 10-35% of the polyether diol, 40% of the active monomer 1 and 0.1% of the rose red + 0.3% of the N-phenyl glycine are pre-mixed under red light protection, and then 8-12% of the triisocyanate monomer and 0.1% of the organic tin are added and mixed again to obtain a clear photosensitive solution. After that, under red light protection, a certain amount of the above photosensitive solution is sucked and siphoned into a glass box of a certain thickness (the thickness of the box is uniformly 10 μm in the present application), and finally after the siphoning is completed, the glass box is treated with tin foil to avoid light, and placed in an oven at 72°C for 1 h.

[0039] Example 2:

[0040] Preparation of high-refractive monomer 2:

[0041] The active monomer 2 is prepared according to the above chemical synthesis method, wherein the refractive index of the active monomer is 1.65; secondly, 10-35% of the polyether diol, 40% of the active monomer 1 and 0.1% of the rose red + 0.3% of the N-phenyl glycine are pre-mixed under red light protection, and then 8-12% of the triisocyanate monomer and 0.1% of the organic tin are added and mixed again to obtain a clear photosensitive solution. After that, under red light protection, a certain amount of the above photosensitive solution is sucked and siphoned into a glass box of a certain thickness (the thickness of the box is uniformly 10 μm in the present application), and finally after the siphoning is completed, the glass box is treated with tin foil to avoid light, and placed in an oven at 72°C for 1 h.

[0042] Comparative Example 1:

[0043] In the red light protection environment, first 10-35% of polyether diols, 40% of the commercially available acrylic ester monomer (2-phenyl ethyl acrylate) and 0.1% of rose red + 0.3% of N-phenyl glycine are pre-mixed, mixed uniformly, then 8-12% of triisocyanate monomer, 0.1% of organic tin is added and mixed again, to obtain a clear photosensitive solution, then in the red light protection, the photosensitive solution is taken quantitatively, siphoned into a film in a glass box of a specific thickness (the thickness of the box in the application is uniformly 10 μm), finally after the siphoning is finished, the glass box is light-protected with tin foil paper, placed in an oven at 72°C for 1 h.

[0044] Comparative Example 2:

[0045] In the red light protection environment, first 10-35% of polyether diols, 40% of the commercially available acrylic ester monomer (2-phenyl ethyl acrylate) and 0.1% of rose red + 0.3% of N-phenyl glycine are pre-mixed, mixed uniformly, then 8-12% of triisocyanate monomer, 0.1% of organic tin is added and mixed again, to obtain a clear photosensitive solution, then in the red light protection, the photosensitive solution is taken quantitatively, siphoned into a film in a glass box of a specific thickness (the thickness of the box in the application is uniformly 10 μm), finally after the siphoning is finished, the glass box is light-protected with tin foil paper, placed in an oven at 72°C for 1 h.

[0046] Table 1: Test results of Examples 1-2 and Comparative Examples 1-2

[0047] As can be seen from Table 1, the holographic recording medium in Examples 1-2 has a significant improvement in the refractive index modulation compared with Comparative Examples 1-2, because the refractive index of the active monomer in Examples 1-2 is significantly greater than that in Comparative Examples 1-2, which is of great significance for preparing high-performance volume holographic gratings.

[0048] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A holographic recording medium, characterized by, Comprise: A base film-forming material, an active monomer, and a photoinitiator; The active monomer has a refractive index not less than a preset value, and a structural formula is: Wherein R1 is a Cn skeleton, which can be a saturated carbon chain and an unsaturated carbon chain, or a benzene ring or other cyclic structure, wherein n is 1-10; R2 is H or a hydrocarbon or unsaturated acrylate structure containing one or more sulfur atoms; wherein R3 is H or -CH4.

2. A holographic recording medium as claimed in claim 1, characterized in that The reactive monomer includes one or more of the following structural formulas:

3. The holographic recording medium of claim 1, wherein, The base film-forming material is at least one of a vinyl acetate homopolymer, a styrene / butadiene block copolymer, or a polyurethane.

4. A holographic recording medium as claimed in claim 2, characterized in that The polyurethane is prepared by reacting a polyether alcohol with a relative molecular mass of 200-4000 with isocyanate.

5. The holographic recording medium of claim 1, wherein, The sulfur atom content is 5%-50%.

6. The holographic recording medium of claim 1, wherein, Also comprising a toughening agent.

7. A holographic recording medium as claimed in claim 6, characterized in that The boiling point of the toughening agent is greater than 200 degrees Celsius.

8. A holographic recording medium as claimed in claim 7, characterized in that The base film-forming material content is 10%-60%; the active monomer content is 20%-50%; the initiator content is 0.01%-1%; and the plasticizer content is 2%-20%.

9. A holographic recording medium as claimed in claim 7, characterized in that The base film-forming material content is 20%-50%; the active monomer content is 30%-45%; the initiator content is 0.1%-0.3%; and the plasticizer content is 2%-8%.

10. The holographic recording medium of claim 1, wherein, The photoinitiator is a combination of rose red, rhodamine, and n-amino glycine / ethylenediamine, or a combination of a boron-containing quaternary ammonium salt and rose red.

Images