CN-122011286-A - Holographic optical storage medium based on low refractive index matrix

Abstract

A holographic optical storage medium based on low refractive index matrix belongs to the technical field of holographic optics. According to the optimal mass ratio, acrylate monomers, a photoinitiator, a chain transfer agent, a matrix and a solvent are mixed to prepare the holographic polymer grating material, and the chain length of the polymer is shortened by introducing the chain transfer agent to eliminate oxygen inhibition, so that the holographic grating performance of the material is remarkably improved, and compared with the material without the chain transfer agent, the refractive index modulation degree of the holographic polymer grating material is improved by 258%. The material has higher refractive index modulation degree, simple preparation, low cost and remarkable improvement of optical performance, and has high application value in the fields of holographic optical storage and AR intelligent display equipment.

Inventors

• GUO JINXIN
• TIAN RUN

Assignees

• 北京工业大学

Dates

Publication Date

20260512

Application Date

20260129

Claims (5)

1. 1. A holographic optical storage medium based on a low refractive index matrix is characterized in that the raw material composition comprises the following components: Material type Mass fraction Acrylic ester monomer 50% Polyethylene acetate matrix 50% Photosensitizers The doping concentration is 2% of the mass of the monomer Mercaptan chain transfer agent The doping amount is 5-25% of the mass of the monomer Solvent(s) The amount of solvent is 2-5 times, preferably 3 times of that of the matrix The acrylic monomer is selected from tricyclodecanedimethanol diacrylate (A-DCP), the matrix is selected from polyethylene acetate, the photoinitiator is selected from titanium dipentahydrate (Irgacure 784), the chain transfer agent is selected from 2,2' - (1, 2-ethylenedioxy) diethyl mercaptan (DODT) the solvent is N, N-Dimethylformamide (DMF).
2. 2. A method for producing a low refractive index matrix-based holographic optical storage medium as claimed in claim 1, wherein, (1) Preparing a photoinduced holographic polymer solution doped with a chain transfer agent, mixing and stirring acrylate monomers, a matrix, a photoinitiator and the chain transfer agent in a clean brown bottle according to a proportion to be in a uniform transparent state; (2) And (3) performing double interference lithography by using coherent light with the wavelength of 532 nm, and performing photochemical reaction under exposure to generate the polymer grating film.
3. 3. The method according to claim 2, wherein the exposure intensity is 20 mW/cm 2 and the period of the interference light is 700 nm.
4. 4. The method of claim 2, wherein the photopolymer film has a refractive index modulation of up to 0.072 with a 15wt.% chain transfer agent doping level.
5. 5. The use of a photopolymer material based on chain transfer reactions according to claim 1 in holographic optical storage, holographic waveguide display materials.

Description

Holographic optical storage medium based on low refractive index matrix Technical Field The invention relates to a holographic optical storage medium based on a low refractive index matrix, and belongs to the technical field of holographic optics. Background The demands for deep learning and cloud computing for database information storage are continually being upgraded, exacerbating the demands for advanced storage technologies. Traditional hard disk storage based on semiconductor materials adopts a planar data access mode. In contrast, volume holographic storage records information by light field distribution in a three-dimensional space, has excellent storage density and reading speed, and has low preparation cost and high recording sensitivity. Both storage technologies show respective unique advantages, but the actual development of holographic storage technologies facilitates diverse advances and innovations in future data access. Compared with other holographic materials, the photosensitive polymer material has the advantages of simple preparation, no byproducts and the like, and the conventional common photopolymer system mainly comprises acrylamide, acrylic esters, mercaptan-olefin systems and the like. Wherein the acrylic ester system is widely used due to the advantages of low price, few byproducts, simple operation, high reaction speed and the like. The present study is to use acrylates as reactive monomers to prepare polymer holographic gratings. The method is characterized in that a matrix and a photoinitiator are uniformly mixed in the manufacture of the holographic grating of the photopolymer body, the recording principle of the grating is based on the photopolymerization-induced phase separation principle, and the mechanism of phase separation occurs in a driving material through photoinitiated polymerization reaction, mainly depends on the component distribution and diffusivity of the photoinitiated polymer composite material under the action of the photoinitiator, so that a structure with periodic refractive index change is formed, under the irradiation of coherent light, the medium photoinitiator of a coherent light area absorbs photons to generate initiation free radicals to initiate polymerization of the monomers and rapidly form a polymer long chain, along with the polymerization of the monomers of the coherent light area, the chemical potential of the monomers of the coherent dark area is lower than that of the light area, the monomers of the dark area diffuse to the light area, when the polymerization reaction degree deepens, the material reaches a gel point, finally, the periodic grating structure with alternately arranged polymer-rich phases and the monomer-rich phases is formed, and if the monomer conversion rate is high enough, the final refractive index difference depends on the difference between the refractive index of the polymer and the refractive index of the matrix. In order to increase the refractive index modulation degree of the volume holographic grating as much as possible, the refractive index difference between the coherent light area and the dark area is improved, the most direct method is to use a matrix with low refractive index and a monomer with high refractive index, wherein the matrix commonly used in a photopolymer system at present comprises polyvinyl alcohol, polyurethane, epoxy resin and the like, the refractive index of polyurethane commonly used in acrylate monomers is between 1.45 and 1.7, the refractive index of polyurethane synthesized by polyethylene glycol and 1, 6-hexanediol in Korean Kim is between 1.454, and polyvinyl acetate PVAC with lower refractive index is selected as the matrix of the user, and the matrix has high compatibility with ADCP. Polyethylene acetate (pvac) is a good quality adhesive with very high transmittance. Hyuk Yoon et al, 2005 produced gratings with 70% diffraction efficiency at 60 microns thickness using acrylate monomers with cellulosic binders. And Naydenove et al in 2017 prepared a volume holographic grating with modulation degree reaching 0.004 by using an acrylamide monomer and polyvinyl acetate. Polyethylene acetate has great potential in polymer systems as seen in the prior studies, so the present study selects the appropriate high refractive index acrylate to combine with polyethylene acetate. Besides the low refractive index matrix and the high refractive index monomer, the conversion rate of the monomer can also influence the quality of the grating, for a system initiated by titanium dipentaerythritol, the monomer can be rapidly polymerized to form a polymer long chain in early polymerization stage to form early gelation, the early gelation can seriously influence the diffusion and polymerization of the monomer, in order to improve the conversion rate of the monomer and prolong the gelation time, mercaptan is selected to be doped as a chain transfer agent, the chain transfer agent is doped to rapidly polymerize