Preparation method of polyurethane acrylate second-order holographic film and second-order holographic film

Abstract

The present application provides a method for preparing a second-order holographic film of polyurethane acrylate and a second-order holographic film, which uses a capping agent to cap the first-order isocyanate, passivate the activity of the isocyanate group, extend the storage time of the glue, and avoid the continuous thickening of the material viscosity during the processing process, resulting in rheological differences, process fluctuations, and increased difficulty in material preparation.

Description

Technical Field

[0001] The embodiments of the present application belong to the technical field of preparation of polyurethane acrylate second-order holographic films, and in particular, relate to a preparation method of a polyurethane acrylate second-order holographic film and a polyurethane acrylate second-order holographic film. Background Art

[0002] Holographic film is an important carrier of AR display technology. The preparation of holographic film with high diffraction efficiency is an important basis for holographic display. The current mainstream methods focus on polymer dispersed liquid crystal holographic gratings and polyurethane acrylate second-order holographic film. The polyurethane acrylate second-order holographic film is mainly made of a homogeneous mixed solution of polyurethane thermal cross-linking monomers, photosensitive monomers, thermal cross-linking catalysts, and photoinitiators. It is first formed into a low-refractive index polyurethane resin by light-proof thermal cross-linking, and then prepared by coherent laser exposure. During the exposure process, UV monomers / polymers diffuse to the coherent bright area and undergo polymerization to generate high-refractive polymers, thereby forming a periodic refractive index modulated film. However, due to the high activity and fast reaction speed of the first-order isocyanate monomer, the sample has a short storage period and the viscosity increases too quickly, which is not conducive to the subsequent process processing and operation. Summary of the invention

[0003] In order to solve or alleviate the problems in the prior art, the present application provides a method for preparing a polyurethane acrylate second-order holographic film and a polyurethane acrylate second-order holographic film, which can solve the technical problems that the first-order isocyanate monomer has high activity and fast reaction speed, resulting in short sample storage period and too fast viscosity increase, which is not conducive to subsequent process processing and operation.

[0004] In a first aspect, the present application provides a method for preparing a polyurethane acrylate second-order holographic film, comprising:

[0005] A blocking agent is selected to block the isocyanate monomer to deactivate the activity of the isocyanate group in the isocyanate monomer;

[0006] The photoinitiator, the photosensitive monomer, the polyol, the blocked isocyanate monomer, the chain extender and the thermal crosslinking catalyst are mixed according to the preset weight proportions to prepare the polyurethane acrylate second-order holographic film glue;

[0007] Coating the polyurethane acrylate second-order holographic film glue on the substrate in a light-proof manner, and then unsealing the polyurethane acrylate second-order holographic film glue at a preset temperature to obtain a substrate material disposed on the substrate;

[0008] The base material is subjected to holographic exposure to form a polyurethane acrylate second-order holographic film.

[0009] As a preferred embodiment of the present application, the isocyanate monomer is isophorone diisocyanate or toluene diisocyanate.

[0010] As a preferred embodiment of the present application, the end-capping agent is one or more of phenol, nonylphenol, methyl ethyl ketone oxime, caprolactam, amide, imidazole and pyrazole.

[0011] As a preferred embodiment of the present application, the photoinitiator includes a photosensitizer and a co-initiator, the photosensitizer is one of tetraiodofluorescein B, curcumin and anthraquinone, and the co-initiator includes a mixed initiator such as a Class II photoinitiator and a cationic one.

[0012] As a preferred embodiment of the present application, the photosensitive monomer is one or more of acrylate / modified acrylate monomers and prepolymers, methacrylate / modified methacrylate monomers and prepolymers, vinyl monomers and prepolymers, and allyl monomers and prepolymers.

[0013] As a preferred embodiment of the present application, the chain extender is propylene glycol.

[0014] As a preferred embodiment of the present application, the thermal cross-linking catalyst is an organic metal catalyst.

[0015] As a preferred embodiment of the present application, the organic metal catalyst is an organic tin, a carboxylate or a metal alkyl compound.

[0016] As a preferred embodiment of the present application, the preset weight proportions of the photoinitiator, photosensitive monomer, polyol, blocked isocyanate monomer, chain extender and thermal crosslinking catalyst are:

[0017] The photoinitiator is 2-5 parts, the photosensitive monomer is 30-60 parts, the polyol is 30-40 parts, the blocked isocyanate monomer is 4-12 parts, the chain extender is 5-13 parts, and the thermal crosslinking catalyst is 0.02-0.05 parts.

[0018] Compared with the prior art, the present application provides a method for preparing a second-order holographic film of polyurethane acrylate, which uses a capping agent to cap the first-order isocyanate, passivate the activity of the isocyanate group, extend the storage time of the glue, and avoid the continuous thickening of the material viscosity during the processing, resulting in rheological differences, process fluctuations, and increased difficulty in material preparation.

[0019] In a second aspect, the present application provides a polyurethane acrylate second-order holographic film prepared by any method described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. Some specific embodiments of the present application will be described in detail in an illustrative and non-restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings:

[0021] Figure 1 is a picture of a polyurethane acrylate second-order holographic film prepared by a control example;

[0022] Figure 2 is a picture of the polyurethane acrylate second-order holographic film prepared by Example 1;

[0023] Figure 3 This is a picture of the polyurethane acrylate second-order holographic film prepared in Example 2. DETAILED DESCRIPTION

[0024] 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 will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not 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.

[0025] In a first aspect, the present application provides a method for preparing a polyurethane acrylate second-order holographic film, comprising:

[0026] A blocking agent is selected to block the isocyanate monomer to deactivate the activity of the isocyanate group in the isocyanate monomer;

[0027] The photoinitiator, the photosensitive monomer, the polyol, the blocked isocyanate monomer, the chain extender and the thermal crosslinking catalyst are mixed according to the preset weight proportions to prepare the polyurethane acrylate second-order holographic film glue;

[0028] The polyurethane acrylate second-order holographic film glue is coated on the substrate in a light-proof manner, and then the blocked isocyanate monomers in the polyurethane acrylate second-order holographic film glue are unblocked at a preset temperature to obtain a base material disposed on the substrate;

[0029] The base material is subjected to holographic exposure to form a polyurethane acrylate second-order holographic film.

[0030] In the embodiment of the present application, the isocyanate monomer is isophorone diisocyanate or toluene diisocyanate.

[0031] In an embodiment of the present application, the end-capping agent is one or more of phenol, nonylphenol, methyl ethyl ketone oxime, caprolactam, amide, imidazole and pyrazole.

[0032] In an embodiment of the present application, the photoinitiator includes a photosensitizer and a co-initiator, the photosensitizer is one of tetraiodofluorescein B, curcumin and anthraquinone, and the co-initiator includes a mixed initiator such as a Class II photoinitiator and a cationic one.

[0033] In the embodiments of the present application, the photosensitive monomer is one or more of acrylate / modified acrylate monomers and prepolymers, methacrylate / modified methacrylate monomers and prepolymers, vinyl monomers and prepolymers, and allyl monomers and prepolymers.

[0034] In the embodiment of the present application, the chain extender is propylene glycol.

[0035] In an embodiment of the present application, the thermal cross-linking catalyst is an organic metal catalyst.

[0036] In the embodiments of the present application, the organic metal catalyst is organic tin, carboxylate, or metal alkyl compound.

[0037] In the embodiment of the present application, the preset weight proportions of the photoinitiator, the photosensitive monomer, the polyol or the blocked isocyanate monomer, the chain extender and the thermal crosslinking catalyst are:

[0038] The photoinitiator is 2-5 parts, the photosensitive monomer is 30-60 parts, the polyol is 30-40 parts, the blocked isocyanate monomer is 4-12 parts, the chain extender is 5-13 parts, and the thermal crosslinking catalyst is 0.02-0.05 parts. In the embodiment of the present application, the polyol can also be replaced by a polyamine monomer.

[0039] Compared with the prior art, the present application provides a method for preparing a second-order holographic film of polyurethane acrylate, which uses a capping agent to cap the first-order isocyanate, passivate the activity of the isocyanate group, extend the storage time of the glue, and avoid the continuous thickening of the material viscosity during the processing, resulting in rheological differences, process fluctuations, and increased difficulty in material preparation.

[0040] The polyurethane acrylate second-order holographic film is mainly composed of a mixture of polyurethane thermal cross-linking monomers (first-order monomers), photosensitive monomers (second-order monomers), thermal cross-linking catalysts (first-order initiators), photoinitiators (second-order initiators), etc. as glue, which is formed by first-order thermal cross-linking to form a polyurethane base and second-order holographic coherent exposure to form a periodically arranged acrylate polymer, wherein a refractive index modulation is formed between the periodically arranged acrylate polymer and the polyurethane base.

[0041] The polyurethane thermal cross-linking monomer is a mixture of isocyanate monomers, polyols or polyamine monomers;

[0042] The thermal crosslinking catalyst is a thermal reaction initiator for crosslinking and curing isocyanate monomers, polyols or polyamine monomers into polyurethane, and the thermal crosslinking catalyst is an organic metal catalyst such as organic tin, carboxylate, metal alkyl compound, etc.

[0043] The present application mainly selects a suitable blocking agent to block the isocyanate monomer to passivate the activity of the isocyanate, mixes a photoinitiator, a photosensitive monomer, a polyol, a blocked isocyanate monomer, a chain extender and a thermal cross-linking catalyst according to a preset weight fraction, and prepares a polyurethane acrylate second-order holographic film adhesive. Since the activity of the isocyanate monomer is reduced, the storage stability and coating processing stability of the adhesive are increased, and then the adhesive is coated on an optical glass or an optical film in a light-proof manner, and the blocking agent is unblocked above the unblocking temperature to generate a first-order reaction to form a base material, and then the material is holographically exposed to form a polyurethane acrylate second-order holographic film.

[0044] The following is a detailed description of the technical solution of the book application with specific embodiments:

[0045] Comparison Example

[0046]

[0047] The first step is the preparation of polyurethane acrylate second-order holographic film glue: adding monomers in sequence according to the reference example table, and preparing a uniform mixed solution.

[0048] In the second step, a coating machine or a scraper is used to form a film of the adhesive. The base material can be optically transparent glass or an optically transparent film. The adhesive is then placed in an oven at 75°C to decapsulate the polyurethane acrylate second-order holographic film adhesive and undergo a first-order reaction for 12 hours. The sample is then holographically exposed (532nm) to form a polyurethane acrylate second-order holographic film.

[0049] Example 1

[0050]

[0051] The first step is to prepare methyl ethyl ketone oxime-terminated isophorone diisocyanate monomer: add isophorone diisocyanate prepolymer (IPDI) with known NCO content (NCO content refers to the mass percentage of isocyanate groups in chemical materials) into the reactor, then pass N2 protection, then add the calculated amount of methyl ethyl ketone oxime capping agent, react at 50-60 ° C for 0.5 h, and then increase to 75 ° C for reaction. During the reaction, monitor the NCO content in the system. When it reaches the predetermined value, stop the reaction and detect whether it is the desired reaction product by nuclear magnetic resonance.

[0052] The second step is to prepare the polyurethane acrylate second-order holographic film glue solution: add the monomers in sequence according to the table of Example 1, and prepare them evenly to form a mixed solution.

[0053] The third step is to use a coating machine or a scraping device to form a film on the adhesive. The base material can be optically transparent glass or an optically transparent film. Then, it is placed in an oven at 75°C to deblock the polyurethane acrylate second-order holographic film adhesive and undergo a first-order reaction for 12 hours. Then, the sample is holographically exposed (532nm) to form a polyurethane acrylate second-order holographic film.

[0054] Example 2

[0055]

[0056] The first step is to prepare phenol-terminated toluene diisocyanate monomer: add stoichiometric capping agent and solvent to the prepolymer of toluene diisocyanate, with the amount of solvent being 30% to 40% of the capping agent, control the reaction temperature to be constant, react for a certain time, take samples at regular intervals, analyze the unreacted NCO content in the reaction product, stop the reaction when it reaches a predetermined value, and use nuclear magnetic resonance to detect whether it is the desired reaction product.

[0057] The second step is to prepare the polyurethane acrylate second-order holographic film glue solution: add the monomers in sequence according to the table of Example 2, and prepare them evenly to form a mixed solution.

[0058] The third step is to use a coating machine or a scraping device to form a film on the adhesive liquid. The base material is optically transparent glass. It is then placed in an oven at 110°C to deblock the polyurethane acrylate second-order holographic film adhesive for 30 minutes, and then lowered to 75°C to allow a first-order reaction to occur for 12 hours. The sample is then holographically exposed (532nm) to form a polyurethane acrylate second-order holographic film.

[0059] refer to Figure 1 , Figure 2 and Figure 3 As shown, the control example formula is the same as that of Example 1 except for the isocyanate monomer. The control example is unblocked isophorone diisocyanate, and Example 1 is methyl ethyl ketoxime blocked isophorone diisocyanate. The glue solution is configured by controlling the single factor change. Then a liquid crystal cell with a thickness of 10um is selected, and the glue solution is dripped at the opening of the liquid crystal cell to fill the liquid crystal cell by capillary diffusion. Figure 1 As shown, the control group has a large activity due to the unblocked isocyanate, and a reaction occurs during the diffusion process, the material viscosity continues to thicken, the diffusion filling is incomplete, and the exposure area is small; while in Example 1, since the isocyanate is blocked, the activity is reduced, the viscosity changes little, and the filling is relatively complete. Similarly, Example 2 is phenol-blocked toluene diisocyanate, and its effect is similar to Example 1, the filling is relatively complete, and there is a sufficient area for exposure to form a grating.

[0060] In a second aspect, the present application provides a polyurethane acrylate second-order holographic film prepared by any method described in the first aspect.

[0061] 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 method for preparing a polyurethane acrylate second-order holographic film, characterized in that: include: A blocking agent is selected to block the isocyanate monomer to deactivate the activity of the isocyanate group in the isocyanate monomer; The photoinitiator, photosensitive monomer, polyol, blocked isocyanate monomer, chain extender and thermal crosslinking catalyst are mixed according to preset weight proportions to prepare polyurethane acrylate second-order holographic film glue; the photoinitiator is 2-5 parts, the photosensitive monomer is 30-60 parts, the polyol is 30-40 parts, the blocked isocyanate monomer is 4-12 parts, the chain extender is 5-13 parts, and the thermal crosslinking catalyst is 0.02-0.05 parts; Coating the polyurethane acrylate second-order holographic film glue on the substrate in a light-proof manner, and then unsealing the polyurethane acrylate second-order holographic film glue at a preset temperature to obtain a substrate material disposed on the substrate; The base material is subjected to holographic exposure to form a polyurethane acrylate second-order holographic film.

2. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The isocyanate monomer is isophorone diisocyanate or toluene diisocyanate.

3. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The end-capping agent is one or more of phenol, nonylphenol, methyl ethyl ketone oxime, caprolactam, amide, imidazole and pyrazole.

4. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The photoinitiator comprises a photosensitizer and a co-initiator, wherein the photosensitizer is one of tetraiodofluorescein B, curcumin and anthraquinone, and the co-initiator comprises a type II photoinitiator and a cationic hybrid initiator.

5. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The photosensitive monomer is one or more of acrylate monomers, modified acrylate monomers, methacrylate monomers, modified methacrylate monomers, vinyl monomers, and allyl monomers.

6. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The chain extender is glycerol.

7. The method for preparing a polyurethane acrylate second-order holographic film according to claim 1, characterized in that: The thermal crosslinking catalyst is an organic metal catalyst.

8. The method for preparing a polyurethane acrylate second-order holographic film according to claim 7, characterized in that: The organic metal catalyst is an organic tin compound or a metal alkyl compound.

9. A polyurethane acrylate second-order holographic film, characterized in that: Prepared by the method according to any one of claims 1 to 8.

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