Preparation method of volume holographic grating, volume holographic grating, optical waveguide and display device

Abstract

The present application provides a method for preparing a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device. The method comprises: obtaining a holographic material to be exposed, wherein the holographic material to be exposed comprises a thermosetting liquid crystal material; providing a liquid crystal cell and filling the liquid crystal cell with the holographic material to be exposed; exposing the holographic material to be exposed in the liquid crystal cell using a preset light source to obtain a processed grating; applying a preset electric field to the processed grating and heating the processed grating after the application of the preset electric field to solidify the thermosetting liquid crystal molecules in the processed grating that have been oriented by the preset electric field, thereby producing a volume holographic grating. The present application can improve the stability of the arrangement state of the liquid crystal molecules in the volume holographic grating at higher temperatures, thereby ensuring the diffraction efficiency of the volume holographic grating and avoiding the degradation of the optical performance of the volume holographic grating at high temperatures.

Description

Technical Field

[0001] The present application relates to the technical field of grating preparation, and in particular to a method for preparing a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device. Background Art

[0002] Today, due to the excellent optical performance of waveguides, more and more display devices are equipped with them to achieve display. Holographic gratings are often installed in waveguides due to their simple preparation process and high yield. However, the free liquid crystal molecules in some holographic gratings have different alignment directions at different temperatures. Therefore, in some high-temperature working environments, the alignment of the liquid crystal molecules in these holographic gratings is easily changed, resulting in a decrease in the diffraction efficiency of the holographic grating, and thus a degradation of the optical performance of the holographic grating. Summary of the Invention

[0003] The present application provides a method for preparing a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device, aiming to improve the stability of the arrangement state of the liquid crystal molecules of the volume holographic grating at high temperatures, thereby maintaining the diffraction efficiency of the volume holographic grating and avoiding the optical performance degradation of the volume holographic grating at high temperatures.

[0004] In a first aspect, the present application provides a method for preparing a volume holographic grating, the method comprising the following steps:

[0005] Obtaining a holographic material to be exposed, wherein the holographic material to be exposed comprises a thermosetting liquid crystal material;

[0006] Providing a substrate, and coating the holographic material to be exposed on the substrate;

[0007] Based on a preset light source, the holographic material to be exposed coated on the substrate is exposed to obtain a grating to be processed;

[0008] A preset electric field is applied to the grating to be processed and the grating to be processed after the preset electric field is applied is heated to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field, thereby producing a volume holographic grating.

[0009] In a second aspect, the present application further provides a volume holographic grating, which is manufactured by the method for preparing the volume holographic grating provided in the first aspect.

[0010] In a third aspect, the present application further provides an optical waveguide, which comprises at least the volume holographic grating provided in the second aspect.

[0011] In a fourth aspect, the present application further provides a display device, which includes at least an optical engine and an optical waveguide as provided in the third aspect.

[0012] The present application provides a method for preparing a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device. The present application adds a thermosetting liquid crystal material to a holographic material to be exposed, thereby completing an exposure process of the holographic material to be exposed on a substrate to obtain a processed grating. A preset electric field is then applied to the processed grating, and the processed grating after the electric field is applied is heated to further thermally cure the liquid crystal molecules in the processed grating that are oriented by the preset electric field, thereby fixing the arrangement direction of the liquid crystal molecules. This improves the stability of the arrangement state of the liquid crystal molecules in the volume holographic grating at higher temperatures, thereby ensuring the diffraction efficiency of the volume holographic grating and avoiding the degradation of the optical performance of the volume holographic grating at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0014] Figure 1 A schematic flow chart of a method for preparing a volume holographic grating according to an embodiment of the present application;

[0015] Figure 2 A schematic diagram of the molecular structure of the photoinitiator 1173 provided in one embodiment of the present application;

[0016] Figure 3 A schematic diagram of the molecular structure of the photoinitiator TPO provided in another embodiment of the present application;

[0017] Figure 4 A schematic diagram of the molecular structure of a photoinitiator 184 provided in yet another embodiment of the present application;

[0018] Figure 5 A schematic diagram of the molecular structure of a photoinitiator 907 provided in yet another embodiment of the present application;

[0019] Figure 6 A schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in one embodiment of the present application;

[0020] Figure 7 A schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in another embodiment of the present application;

[0021] Figure 8 A schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in yet another embodiment of the present application.

[0022] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, combined, or partially merged, so the actual execution order may vary depending on the actual situation.

[0025] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0026] It should be noted that the liquid crystal molecules in the holographic grating provided in the related art are mostly arranged in a direction parallel to the grating vector. In this state, the holographic grating has a high diffraction efficiency for p-polarized light. However, when the ambient temperature of the environment in which the holographic grating is located or the temperature of the holographic grating itself rises to a certain level, the arrangement of the liquid crystal molecules in the holographic grating easily changes from a state parallel to the grating vector to a disordered state, thereby causing the diffraction efficiency of the holographic grating for p-polarized light to decrease.

[0027] The volume holographic grating preparation method provided in the present application can stabilize the arrangement state of liquid crystal molecules in the volume holographic grating, so that the liquid crystal molecules in the prepared volume holographic grating can maintain a highly ordered arrangement state within a wide temperature range, thereby ensuring the diffraction efficiency of the volume holographic grating and avoiding the optical performance degradation of the volume holographic grating under high temperature conditions.

[0028] Please refer to Figure 1 , Figure 1 A schematic flow chart of a method for preparing a volume holographic grating provided in an embodiment of the present application.

[0029] like Figure 1 As shown, the method for preparing the volume holographic grating includes steps S101 to S104.

[0030] Step S101: Obtain a holographic material to be exposed, wherein the holographic material to be exposed includes a thermosetting liquid crystal material.

[0031] Exemplarily, the holographic material to be exposed is used to prepare a holographic surface with diffraction properties, thereby realizing the preparation of a volume holographic grating. Specifically, the holographic material to be exposed includes a thermosetting liquid crystal material. The thermosetting liquid crystal material can form a structure with a certain stability at a certain temperature, thereby maintaining the stability of the liquid crystal molecular arrangement.

[0032] In some embodiments, the thermosetting liquid crystal material includes epoxy-organic amine.

[0033] In the specific implementation process, the epoxy-organic amine component is prepared by adding a portion of organic amines with different functions to the components of the epoxy liquid crystal monomer to achieve the effect of promoting the crosslinking density in the reaction. It should be understood that the thermosetting liquid crystal material also includes epoxy liquid crystal monomers without organic amines and other monomers or oligomers, so that the liquid crystal molecules can be heated and cured after orientation.

[0034] In some embodiments, obtaining the holographic material to be exposed includes: preparing the holographic material to be exposed based on provided thermosetting liquid crystal material and prepolymer, wherein the prepolymer includes a thermal curing accelerator, a photopolymerizable monomer, and a photoinitiator.

[0035] In a specific implementation, a thermosetting liquid crystal material is mixed with a prepolymer to obtain the holographic material to be exposed. Specifically, the prepolymer includes, but is not limited to, a thermal curing accelerator, a photopolymerization monomer, a photoinitiator, and a thermal curing crosslinker. The photopolymerization monomer is a reactant capable of undergoing a polymerization reaction, including but not limited to liquid crystal monomers and photopolymerizable liquid crystals. Specifically, the molecular structure of the photopolymerizable liquid crystal has a liquid crystal core and reactive functional groups at the ends. These functional groups can form a polymer network through photopolymerization, thereby becoming a liquid crystal polymer. Before polymerization, the photopolymerizable liquid crystal undergoes a periodic and orderly arrangement of directors along the alignment layer. Subsequently, photopolymerization occurs to obtain the processed grating.

[0036] For example, the photoinitiator includes but is not limited to photoinitiator 1173, photoinitiator TPO, photoinitiator 184, photoinitiator 907, etc.

[0037] Among them, the chemical name of photoinitiator 1173 is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and its chemical formula is C6H5COC(CH3)2OH, and its structure is as follows: Figure 2 shown.

[0038] The chemical name of the photoinitiator TPO is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and its chemical formula is C 22 H 21 O2P, structure as Figure 3 shown.

[0039] The chemical name of photoinitiator 184 is 1-hydroxycyclohexylphenyl ketone, and its chemical formula is C 13 H 16 O2, structure as Figure 4 shown.

[0040] The chemical name of photoinitiator 907 is 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and its chemical formula is C 13 H 17 NO2S, the structure is Figure 5 shown

[0041] In other implementations, the prepolymer also includes an inert liquid crystal material, so that the thermosetting liquid crystal material, the inert liquid crystal material, and the photopolymerizable monomer can be polymerized under the action of a photoinitiator to form a polymer, and the formed polymer can be further cured under the action of a thermal curing accelerator.

[0042] In some embodiments, the holographic material to be exposed includes liquid crystal units in a photopolymerizable monomer and / or a thermal curing accelerator.

[0043] It should be noted that the liquid crystal unit is a structural unit in the molecular structure that can promote the formation of a liquid crystal state, so as to at least enable the thermosetting liquid crystal material to form a liquid crystal state during the reaction process.

[0044] In some embodiments, the step of preparing the holographic material to be exposed based on the provided thermosetting liquid crystal material and prepolymer includes: mixing the thermosetting liquid crystal material and the prepolymer in a preset ratio to obtain the holographic material to be exposed.

[0045] For example, the desired holographic material to be exposed is obtained by mixing a thermosetting liquid crystal material, a photopolymerizable monomer, a photoinitiator, and a thermal curing accelerator in a certain ratio.

[0046] It should be understood that the above-mentioned holographic material to be exposed can also be adjusted according to actual needs. For example, inert liquid crystal material and heat curing cross-linking agent can be added to the holographic material to be exposed according to actual needs, which is not limited here.

[0047] In the specific implementation process, taking the thermosetting liquid crystal material including epoxy liquid crystal monomer and non-liquid crystal multifunctional epoxy monomer as an example, the epoxy liquid crystal monomer, non-liquid crystal multifunctional epoxy monomer, inert liquid crystal material, photopolymerization monomer, photoinitiator, thermal curing accelerator and thermal curing crosslinking agent are mixed according to a preset ratio to obtain the holographic material to be exposed.

[0048] It should be noted that the preset ratio can be flexibly set according to actual conditions. For example, the preset ratio is set to 1:1 for each component. Of course, the preset ratio can also be set to other values. This application does not limit the specific value of the preset ratio.

[0049] Step S102: providing a liquid crystal cell, and filling the holographic material to be exposed into the liquid crystal cell.

[0050] In a specific implementation process, the liquid crystal cell can control the arrangement of liquid crystal molecules based on a driving voltage (applied electric field), thereby changing the optical properties of the liquid crystal.

[0051] Step S103: performing exposure processing on the holographic material to be exposed in the liquid crystal cell based on a preset light source to obtain a grating to be processed.

[0052] Exemplarily, exposure processing is performed on the holographic material to be exposed, which can cause the monomers in the holographic material to undergo photopolymerization reaction, so that the monomers in the coherent dark area diffuse into the coherent bright area, and the photo-inert components diffuse into the coherent dark area, thereby forming a holographic grating structure to obtain the grating to be processed.

[0053] For example, exposure is performed under a polarized interference light field with a period of 1 μm. At this time, the thermosetting liquid crystal molecules in the holographic grating to be exposed will undergo a photopolymerization reaction, thereby obtaining the grating to be processed.

[0054] It should be noted that the exposure parameters such as the wavelength of the light source and the exposure dose can be set according to actual conditions to obtain the grating to be processed.

[0055] Step S104 : applying a preset electric field to the grating to be processed and heating the grating to be processed after the preset electric field is applied, so as to solidify the thermosetting liquid crystal molecules in the grating to be processed that have been aligned by the preset electric field, thereby producing a volume holographic grating.

[0056] Exemplarily, after obtaining the grating to be processed, an electric field of preset intensity and direction is applied to the grating to be processed, so that the liquid crystal molecules in the grating to be processed are arranged in a certain order under the action of the electric field, thereby reducing the light scattering of the prepared volume holographic grating and improving the diffraction efficiency; after the liquid crystal molecules are arranged in an orderly manner, the grating to be processed is heated and cured, so that the liquid crystal molecules in the grating to be processed form a liquid crystal network with a certain orientation structure, thereby achieving the order fixation of the liquid crystal molecules and improving the stability of the prepared volume holographic grating, so that the arrangement state of the liquid crystal molecules in the volume holographic grating will not be destroyed in a high temperature environment, thereby ensuring the stability of the volume holographic grating in a high temperature environment.

[0057] In the holographic grating provided by the related art, at room temperature, the liquid crystal molecules in the holographic grating are arranged in a direction parallel to the grating vector. At this time, the holographic grating has a high diffraction efficiency for p-polarized light. However, when the temperature of the environment in which the holographic grating is located rises to a certain level, such as exceeding the liquid crystal clearing point, the arrangement of the liquid crystal molecules will change from a state parallel to the grating vector to a disordered state, resulting in a decrease in the diffraction efficiency of the holographic grating for p-polarized light. However, the volume holographic grating prepared in the present application, due to the thermal curing treatment, causes the liquid crystal molecules to polymerize or be bound by the formed intermolecular covalent cross-linking network, forming a liquid crystal network with a certain orientation structure, thereby achieving the fixed order of the liquid crystal molecules. Therefore, in a high-temperature environment, the liquid crystal molecules in the volume holographic grating can still maintain their original state, so that the volume holographic grating still has high stability in a high-temperature environment.

[0058] In some embodiments, applying a preset electric field to the grating to be processed includes: applying an electric field with a preset direction and a preset intensity to the grating to be processed to align liquid crystal molecules in the grating to be processed.

[0059] Exemplarily, an electric field is applied to the grating to be processed. At this time, the liquid crystal molecules in the grating to be processed are driven by a voltage in a specific direction, and the directors are arranged along the voltage direction, thereby promoting the orderly arrangement of the liquid crystal molecules and completing the orientation of the liquid crystal molecules.

[0060] After the liquid crystal molecules are aligned, the electric field is maintained and the grating to be processed is heated while being subjected to the electric field, thereby completing the heat curing of the grating to be processed and producing a volume holographic grating. It should be understood that after the grating to be processed is heat-cured to produce the volume holographic grating, even if the electric field is no longer applied, the alignment of the liquid crystal molecules in the volume holographic grating is fixed and can withstand a certain temperature, thereby producing a stable volume holographic grating.

[0061] In some embodiments, the heat treatment of the grating to be processed after the preset electric field is applied includes: heating the grating to be processed after the preset electric field is applied to a first temperature within a preset time to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field.

[0062] Illustratively, within a preset time, the grating to be processed is heated to a first temperature after a preset electric field is applied, so that the thermosetting liquid crystal molecules in the grating to be processed react, thereby connecting the fragments of the liquid crystal molecules into polymers, thereby completing the solidification of the liquid crystal molecules.

[0063] In a specific implementation process, the grating to be processed also includes inert liquid crystal molecules. During the heating process, the thermosetting liquid crystal molecules can react to form polymers, and the inert liquid crystal molecules will be affected by the thermosetting liquid crystal molecules. Under the interaction between molecules, the inert liquid crystal molecules can also be fixed, so that all the liquid crystal molecules in the grating to be processed are fixed, realizing the solidification of the liquid crystal molecules.

[0064] In some embodiments, the first temperature is higher than a second temperature, and the second temperature is the temperature of the holographic material to be exposed when the holographic material to be exposed is subjected to the exposure process.

[0065] Illustratively, the first temperature for heating the grating to be processed is much higher than the second temperature for exposing the holographic material to be exposed, so as to ensure the ordered phase separation of the liquid crystal phase and the photopolymer during the exposure process, thereby achieving the solidification of the liquid crystal and the photopolymer.

[0066] In a specific embodiment, the first temperature is greater than or equal to 50°C and less than or equal to 150°C.

[0067] In the above embodiment, a volume holographic grating is produced by obtaining a holographic material to be exposed, wherein the holographic material to be exposed includes a thermosetting liquid crystal material; providing a liquid crystal cell, and filling the liquid crystal cell with the holographic material to be exposed; exposing the holographic material to be exposed in the liquid crystal cell based on a preset light source to obtain a grating to be processed; applying a preset electric field to the grating to be processed and heating the grating to be processed after the preset electric field is applied to solidify the thermosetting liquid crystal molecules in the grating to be processed that have been oriented by the preset electric field. By applying an electric field to the grating to be processed, the orientation of each liquid crystal molecule in the prepared volume holographic grating is made the same, the light scattering intensity of the holographic polymer material is reduced, and the diffraction efficiency of the volume holographic grating is improved. In addition, the grating to be processed is heat-cured during the application of the electric field, so that the arrangement state of the liquid crystal molecules in the prepared volume holographic grating will not be destroyed in a high temperature environment, thereby improving the thermal stability of the volume holographic grating. The volume holographic grating can maintain a high light diffraction efficiency in a high temperature environment (higher than the clearing point of the liquid crystal monomer), thereby avoiding the optical performance degradation of the volume holographic grating in a high temperature environment.

[0068] The method for preparing the volume holographic grating of the present application is described below with reference to specific embodiments.

[0069] (1) Obtain epoxy liquid crystal monomer, non-liquid crystal multifunctional epoxy monomer, inert liquid crystal, thermal curing accelerator, photopolymerization monomer and photoinitiator to obtain a holographic material to be exposed.

[0070] (2) Add the above materials into the provided liquid crystal box.

[0071] (3) Expose the holographic material to be exposed in the liquid crystal cell under a polarized interference light field with a period of 1 μm, with a wavelength of 457 nm and an exposure dose of 0.5 J / cm 2 At this time, the photoinitiator absorbs photon energy to generate free radicals, which in turn trigger the polymerization reaction of monomers to generate polymers. The monomers in the coherent dark area diffuse toward the coherent bright area. At the same time, the photoinert components (liquid crystal, thermal curing accelerator, etc.) diffuse toward the coherent dark area to form a grating structure to obtain the grating to be processed.

[0072] (4) Use a 3V working voltage to drive the liquid crystal box to apply an electric field of a certain intensity to the grating to be processed. When the voltage drives the liquid crystal box, the liquid crystal molecules in the grating to be processed are driven by the voltage in a specific direction, and the director vectors are arranged along the voltage direction.

[0073] (5) Maintaining the voltage to drive the liquid crystal box, and using a hot plate to heat the liquid crystal box, thereby heating the grating to be processed to solidify the liquid crystal molecules arranged in the grating to be processed, wherein the heating temperature range is 50°C-150°C, and the heating time is between 2 minutes and 60 minutes, so that the liquid crystal molecules in the grating to be processed form polymers and / or form a cross-linked network to achieve fixation.

[0074] (6) After the heating treatment is completed, the applied voltage is removed to obtain a volume holographic grating.

[0075] It should be understood that since the liquid crystal molecules in the obtained volume holographic grating are solidified and no longer have the ability to move, the director vector will no longer change with changes in temperature, thereby being able to maintain the arrangement state of the liquid crystal molecules in the volume holographic grating in a high-temperature environment, thereby ensuring the diffraction efficiency of the volume holographic grating and thus avoiding the degradation of the optical performance of the volume holographic grating in a high-temperature environment. At the same time, since the heating is carried out under the action of an electric field, the orientation of the liquid crystal molecules is the same during the heating process, thereby making the orientation of each liquid crystal molecule microregion in the obtained volume holographic grating completely identical, thereby improving the diffraction efficiency of the volume holographic grating.

[0076] As shown in the figure, the preparation process and structure of the epoxy liquid crystal monomer in this application are described below in combination with specific examples.

[0077] Example 1:

[0078] (1) Using a round-bottom flask as a container, add 2.1 g of N,N'-dicyclohexylcarbodiimide (10.17 mmol) into the container.

[0079] (2) 0.62 g (5 mmol) of methylhydroquinone and 2.8 g (10 mmol) of 4-(3-((3-methyloxetanyl)methoxypropoxy)benzoic acid were also added to the container.

[0080] (3) Add 40 mL of dichloromethane as a solvent, place the container in an ice bath and stir, and add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base. After stirring for 0.5 hours, transfer to room temperature.

[0081] (4) The reaction was carried out at room temperature for 16 hours, and a white solid RM1 was obtained by column chromatography.

[0082] It should be noted that the white solid RM1 prepared in Example 1 is an epoxy liquid crystal monomer, and its molecular structure is as follows: Figure 6 As shown, the yield of RM1 prepared by the above method was 78%.

[0083] Example 2:

[0084] (1) Use a round-bottom flask as a container and add 2.1 g of N,N'-dicyclohexylcarbodiimide (10.17 mmol) into the container.

[0085] (2) 0.62 g (5 mmol) of methylhydroquinone was also added to the container.

[0086] (3) Add 40 mL of dichloromethane as a solvent, and place the container in an ice bath and stir.

[0087] (4) Add 0.69 g (5 mmol) of 4-hydroxybenzoic acid dropwise for 12 hours.

[0088] (5) Add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base, place in an ice bath and stir for 0.5 hours, then transfer to room temperature and react for 16 hours.

[0089] (6) Place the mixture back under ice bath, add dropwise 1.4 g (5 mmol) of a mixed solution of 4-(3-((3-methyloxetanyl)methoxypropoxy)benzoic acid and dichloromethane (10 mL), return to room temperature and continue the reaction for 16 hours, and separate by column chromatography to obtain a white solid.

[0090] It should be understood that the white solid prepared in Example 2 is an epoxy liquid crystal monomer, and its molecular structure is as follows: Figure 7 As shown, the yield of RM2 prepared by the above method was 59%.

[0091] Example 3:

[0092] (1) Use a round-bottom flask as a container and add 2.1 g of N,N'-dicyclohexylcarbodiimide (10.17 mmol) into the container.

[0093] (2) 0.67 g (5 mmol) of 2,5-dihydroxybenzonitrile and 2.8 g (10 mmol) of 4-(3-((3-methyloxetanyl)methoxypropoxy)benzoic acid were also added to the container.

[0094] (3) Add 40 mL of dichloromethane as a solvent, and place the container in an ice bath and stir.

[0095] (4) Add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base, keep stirring in an ice bath for 0.5 hour, and then transfer to room temperature.

[0096] (5) The mixture was reacted at room temperature for 16 hours and a white solid was obtained by column chromatography.

[0097] It should be understood that the white solid RM3 prepared in Example 3 is an epoxy liquid crystal monomer, and its molecular structure is as follows: Figure 8 As shown, the yield of RM3 prepared by the above method is 83%.

[0098] It should be noted that those skilled in the art can prepare the corresponding epoxy liquid crystal monomer according to the preparation method provided in any of the above embodiments, and this is not limited here.

[0099] The present application also provides a volume holographic grating, wherein the volume holographic grating is produced using the method for producing a volume holographic grating in any of the aforementioned embodiments. Therefore, the volume holographic grating can achieve the beneficial effects achieved by the method for producing a volume holographic grating provided in the embodiments of the present application. For details, refer to the preceding embodiments and will not be repeated here.

[0100] The present application also provides an optical waveguide, wherein the optical waveguide includes at least a waveguide substrate and a diffraction microstructure, the waveguide substrate includes but is not limited to resin and glass, and the diffraction microstructure can be the volume holographic grating in the above-mentioned embodiment; therefore, the optical waveguide can achieve the beneficial effects that can be achieved by the preparation method of the volume holographic grating provided in the embodiment of the present application. Please refer to the previous embodiment for details and will not be repeated here.

[0101] The present application also provides a display device, wherein the display device includes at least an optical machine and the optical waveguide provided in the above-mentioned embodiment; therefore, the display device can also achieve the beneficial effects that can be achieved by the volume holographic grating preparation method provided in the embodiment of the present application, as detailed above, which will not be repeated here.

[0102] In the specific implementation process, the display devices include but are not limited to AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, AR helmets and VR helmets and other near-eye display devices, as well as HUD (head-up display) and the like.

[0103] It should be understood that the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0104] It should also be understood that the term "and / or" used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations. It should be noted that, in this article, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "including a..." does not exclude the presence of other identical elements in the process, method, article or system that includes the element.

[0105] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments. The above description is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a volume holographic grating, characterized in that: include: Obtaining a holographic material to be exposed, wherein the holographic material to be exposed comprises a thermosetting liquid crystal material; Providing a liquid crystal cell, and filling the holographic material to be exposed into the liquid crystal cell; Based on a preset light source, the holographic material to be exposed in the liquid crystal cell is exposed to obtain a grating to be processed; Applying a preset electric field to the grating to be processed and heating the grating to be processed after the preset electric field is applied, so as to solidify the thermosetting liquid crystal molecules in the grating to be processed that have been aligned by the preset electric field, thereby producing a volume holographic grating; The step of heating the grating to be processed after the preset electric field is applied comprises: The grating to be processed after the preset electric field is applied is heated to a first temperature within a preset time to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field; and the first temperature is higher than a second temperature, and the second temperature is the temperature of the holographic material to be exposed when the holographic material to be exposed is subjected to the exposure process.

2. The method for preparing a volume holographic grating according to claim 1, wherein: The thermosetting liquid crystal material includes epoxy-organic amine.

3. The method for preparing a volume holographic grating according to claim 1 or 2, wherein: The step of obtaining the holographic material to be exposed comprises: The holographic material to be exposed is prepared according to the provided thermosetting liquid crystal material and prepolymer, wherein the prepolymer comprises a thermal curing accelerator, a photopolymerizable monomer and a photoinitiator.

4. The method for preparing a volume holographic grating according to claim 3, wherein: The holographic material to be exposed includes liquid crystal units, and the liquid crystal units are located in the photopolymerizable monomer or the thermal curing accelerator.

5. The method for preparing a volume holographic grating according to claim 3, wherein: The method of preparing the holographic material to be exposed based on the provided thermosetting liquid crystal material and prepolymer comprises: The thermosetting liquid crystal material and the prepolymer are mixed in a preset ratio to obtain the holographic material to be exposed.

6. The method for preparing a volume holographic grating according to claim 1 or 2, wherein: The applying a preset electric field to the grating to be processed comprises: An electric field with a preset direction and a preset intensity is applied to the grating to be processed to align the liquid crystal molecules in the grating to be processed.

7. A volume holographic grating, characterized in that: The volume holographic grating is manufactured by the method for preparing the volume holographic grating according to any one of claims 1 to 6.

8. An optical waveguide, characterized in that The optical waveguide includes the volume holographic grating according to claim 7.

9. A display device, characterized in that: The display device at least includes an optical engine and the optical waveguide according to claim 8.

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