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

Abstract

The invention provides a volume holographic grating preparation method, a volume holographic grating, an optical waveguide and a display device, and the method comprises the steps: obtaining a to-be-exposed holographic material which comprises a thermosetting liquid crystal material; providing a liquid crystal box, and filling the liquid crystal box with the holographic material to be exposed; based on a preset light source, performing exposure treatment on the holographic material to be exposed in the liquid crystal box to obtain a grating to be treated; and applying a preset electric field to the to-be-processed grating and heating the to-be-processed grating to which the preset electric field is applied so as to cure the thermosetting liquid crystal molecules oriented by the preset electric field in the to-be-processed grating, thereby obtaining the volume holographic grating. According to the volume holographic grating, the arrangement state stability of the liquid crystal molecules of the volume holographic grating at a relatively high temperature can be improved, so that the diffraction efficiency of the volume holographic grating is ensured, and the optical performance degradation of the volume holographic grating in a high-temperature state is avoided.

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] Nowadays, due to the excellent optical performance of optical waveguides, more and more display devices are equipped with optical waveguides to realize display. Holographic gratings are often set in optical waveguides due to their simple preparation process and high yield; however, the free liquid crystal molecules in some holographic gratings have different arrangement directions at different temperatures. Therefore, in some high-temperature working environments, the arrangement state of the liquid crystal molecules in these holographic gratings is easily changed, resulting in a decrease in the diffraction efficiency of the holographic grating, which in turn leads to a decrease in 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 liquid crystal molecules of the volume holographic grating at high temperature, thereby maintaining the diffraction efficiency of the volume holographic grating, and further avoiding the attenuation of the optical performance of the volume holographic grating under high temperature conditions.

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

[0005] Acquiring 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, so as to obtain 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 manufacturing 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 at least includes an optical machine 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, completes the exposure treatment of the holographic material to be exposed on a substrate to obtain a processed grating, and then applies a preset electric field to the processed grating, and heats the processed grating after the electric field is applied, so as to further thermally cure the liquid crystal molecules oriented by the preset electric field in the processed grating, thereby fixing the arrangement direction of the liquid crystal molecules, so as to improve the arrangement state stability of the liquid crystal molecules of the volume holographic grating at a higher temperature, thereby ensuring the diffraction efficiency of the volume holographic grating, and further avoiding the optical performance attenuation of the volume holographic grating under high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. 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 paying any creative work.

[0014] Figure 1 A schematic diagram of a process for preparing a volume holographic grating provided in 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 a 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 purpose, 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 the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0025] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can 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 higher diffraction efficiency for p-polarized light. 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 is easily transformed from a state parallel to the grating vector to a disordered state, thereby causing the diffraction efficiency of the holographic grating to 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 still maintain a highly ordered arrangement state within a wider temperature range, thereby ensuring the diffraction efficiency of the volume holographic grating and further avoiding the attenuation of the optical performance 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 : obtaining a holographic material to be exposed, wherein the holographic material to be exposed comprises a thermosetting liquid crystal material.

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

[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 part 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 and other monomers or oligomers without the addition of organic amines, so that the liquid crystal molecules can be heated and cured after orientation.

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

[0035] In the specific implementation process, the holographic material to be exposed is obtained by mixing the thermosetting liquid crystal material and the prepolymer; specifically, the prepolymer includes but is not limited to a thermosetting accelerator, a photopolymerization monomer, a photoinitiator and a thermosetting crosslinking agent. Among them, the photopolymerization monomer is a reactant that can undergo a polymerization reaction, including but not limited to a liquid crystal monomer and a photopolymerized liquid crystal; specifically, the molecular structure of the photopolymerized liquid crystal has a liquid crystal core and has reactive functional groups at the end, and these functional groups can form a polymer network through photopolymerization reaction, thereby becoming a liquid crystal polymer. Before polymerization, the photopolymerized liquid crystal is periodically and orderly arranged along the orientation layer with the director, and then photopolymerization occurs to obtain the grating to be processed.

[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-hydroxycyclohexyl phenyl ketone, and its chemical formula is C 13 H 16 O2, structure 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, structure 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 located in photopolymerizable monomers and / or thermal curing accelerators.

[0043] It should be noted that the liquid crystal unit is a structural unit in the molecular structure that can cause the molecule to form a liquid crystal state, so as to at least cause 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 according to the provided thermosetting liquid crystal material and prepolymer comprises: mixing the thermosetting liquid crystal material and the prepolymer in a preset ratio to obtain the holographic material to be exposed.

[0045] Exemplarily, the thermosetting liquid crystal material, the photopolymerizable monomer, the photoinitiator, and the thermal curing accelerator are mixed in a certain ratio to obtain the desired holographic material to be exposed.

[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 thermal 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 cross-linking 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 box, and filling the holographic material to be exposed into the liquid crystal box.

[0050] In a specific implementation process, the liquid crystal box 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: Based on a preset light source, the holographic material to be exposed in the liquid crystal box is exposed to obtain a grating to be processed.

[0052] Exemplarily, exposing the holographic material to be exposed can cause the monomers in the holographic material to undergo photopolymerization, causing the monomers in the coherent dark area to diffuse into the coherent bright area, and the photo-inert components to 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 um, and the thermosetting liquid crystal molecules in the holographic grating to be exposed will undergo a photopolymerization reaction, thereby obtaining a grating to be processed.

[0054] It should be noted that the exposure parameters such as the illumination wavelength and exposure dose of the preset light source 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 after being oriented by the preset electric field, so as to obtain 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 in a higher temperature environment, the arrangement state of the liquid crystal molecules in the volume holographic grating will not be destroyed, 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 along the direction parallel to the grating vector. At this time, the holographic grating has a higher diffraction efficiency for p-polarized light; when the temperature of the environment in which the holographic grating is located rises to a certain level, such as exceeding the clearing point of the liquid crystal, the arrangement of the liquid crystal molecules will change 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; and 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 orderliness of the liquid crystal molecules. Fixation, so that 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 so as to orient 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 alignment of the liquid crystal molecules is completed, the electric field is maintained to be applied to the grating to be processed, and the grating to be processed under the action of the electric field is heated, so as to complete the heat curing of the grating to be processed and obtain a volume holographic grating. It should be understood that after the grating to be processed is heated and cured to obtain a volume holographic grating, even if the electric field is no longer applied, the arrangement state of the liquid crystal molecules in the volume holographic grating is fixed and can withstand a certain temperature, so as to obtain a stable volume holographic grating.

[0061] In some embodiments, the heating 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] Exemplarily, 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, so that the fragments of the liquid crystal molecules are connected 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 become 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 the liquid crystal molecules in the grating to be processed are all fixed, thereby achieving 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] Exemplarily, 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 holographic material to be exposed is obtained, wherein the holographic material to be exposed includes a thermosetting liquid crystal material; a liquid crystal box is provided, and the holographic material to be exposed is filled into the liquid crystal box; based on a preset light source, the holographic material to be exposed in the liquid crystal box is exposed to obtain a grating to be processed; 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 that are oriented by the preset electric field, thereby obtaining a volume holographic grating. By applying an electric field to the grating to be processed, the orientations of the liquid crystal molecules in the prepared volume holographic grating are made the same, and the light scattering intensity of the holographic polymer material is reduced to improve the diffraction efficiency of the volume holographic grating. In the process of applying the electric field, the grating to be processed is heated and cured, 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, so that 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 in conjunction with 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 box 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 initiate the polymerization reaction of the 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) A 3V working voltage is used 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 directors 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 ranges from 50°C to 150°C, and the heating time is between 2min and 60min, 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 the change of temperature, so that the arrangement state of the liquid crystal molecules in the volume holographic grating in a high temperature environment can be maintained, thereby ensuring the diffraction efficiency of the volume holographic grating, and thus avoiding the attenuation 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, and thus the orientation of each liquid crystal molecule micro-region in the obtained volume holographic grating is exactly the same, 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 embodiments.

[0077] Embodiment 1:

[0078] (1) Using a round-bottom bottle 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) 40 mL of dichloromethane was added as a solvent, and the container was placed in an ice bath and stirred. 0.12 g (1 mmol) of 4-dimethylaminopyridine was added as a base, and the mixture was stirred for 0.5 hour and then transferred to room temperature.

[0081] (4) The reaction was allowed to react 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 is 78%.

[0083] Embodiment 2:

[0084] (1) Using a round-bottom bottle as a container, 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 hour, then transfer to room temperature and react for 16 hours.

[0089] (6) Place the mixture back under an 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] Embodiment 3:

[0092] (1) Using a round-bottom bottle as a container, 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 no limitation is made here.

[0099] The present application also provides a volume holographic grating, wherein the volume holographic grating is made by using the method for making the volume holographic grating in any of the above embodiments. Therefore, the volume holographic grating can achieve the beneficial effects that can be achieved by the method for making the volume holographic grating provided in the embodiments of the present application, as detailed in the previous embodiments, which will not be repeated here.

[0100] The present application also provides an optical waveguide, wherein the optical waveguide at least includes 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, see the previous embodiment for details, which will not be repeated here.

[0101] The present application also provides a display device, wherein the display device at least includes 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 in the above text, 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 application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0104] It should also be understood that the term "and / or" used in the specification of this application 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 variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements 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 including the element.

[0105] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The above description is only a specific implementation mode of the present application, but the protection scope 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 the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a volume holographic grating, characterized in that: include: Acquiring a holographic material to be exposed, wherein the holographic material to be exposed comprises a thermosetting liquid crystal material; Providing a liquid crystal box, and filling the holographic material to be exposed into the liquid crystal box; 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; 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, so as to obtain a volume holographic grating.

2. The method for preparing a volume holographic grating according to claim 1, characterized in that: 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 aligned by the preset electric field.

3. The method for preparing a volume holographic grating according to claim 2, characterized in that: 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.

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

5. The method for preparing a volume holographic grating according to any one of claims 1 to 4, characterized in that: 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.

6. The method for preparing a volume holographic grating according to claim 5, characterized in that: The holographic material to be exposed includes a liquid crystal unit, and the liquid crystal unit is located in the photopolymerizable monomer or the thermal curing accelerator.

7. The method for preparing a volume holographic grating according to claim 5, characterized in that: The method of preparing the holographic material to be exposed according to 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.

8. The method for preparing a volume holographic grating according to any one of claims 1 to 4, characterized in that: The step of applying a preset electric field to the grating to be processed comprises: An electric field with a preset direction and a preset strength is applied to the grating to be processed to orient the liquid crystal molecules in the grating to be processed.

9. A volume holographic grating, characterized in that: The volume holographic grating is manufactured by the method for manufacturing a volume holographic grating according to any one of claims 1 to 8.

10. An optical waveguide, characterized in that: The optical waveguide comprises the volume holographic grating as claimed in claim 9.

11. A display device, characterized in that: The display device at least comprises an optical engine and the optical waveguide as claimed in claim 10.

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