Preparation method of volume holographic optical waveguide

Abstract

The invention provides a preparation method of a volume holographic optical waveguide. The preparation method comprises the following steps: providing a first substrate and a second substrate; forming a holographic polymer layer on the surface of the second substrate; the first substrate is attached to the holographic polymer layer on the surface of the second substrate, and a substrate assembly is obtained; the side edge of the substrate assembly is glued; and holographic exposure is carried out on the substrate assembly after side edge gluing, and the volume holographic optical waveguide is obtained. By optimizing the preparation process, increasing side edge gluing and other operations, not only can the offset of the laminated substrate assembly in the subsequent process operations such as holographic exposure be avoided, but also the influence on the effect of the holographic exposure process due to the seepage of the dropwise added refractive index matching liquid at the joint of the first substrate and the second substrate can be avoided, and the production efficiency of the holographic exposure process is improved. And the production quality and efficiency are improved, and it is ensured that produced products have high repeatability and consistency.

Description

Technical Field

[0001] The invention belongs to the field of optical technology and relates to a method for preparing a volume holographic optical waveguide. Background Art

[0002] With the continuous innovation of science and technology, Virtual Reality (VR), Augmented Reality (AR) and Mixed Reality (MR) have gradually entered industries such as industry and education. Among them, volume holographic optical waveguide is an optical component that integrates volume holographic gratings into the surface of the waveguide, realizing multiple turns and transmissions of light, and transferring and copying optical signals. It has the advantages of lightness, thinness, high transmittance, etc., and is the core optical component in the new generation of AR field.

[0003] The manufacturing process of volume holographic optical waveguide mainly involves steps such as preparation of optical waveguide substrate, holographic polymer coating, holographic exposure and photocuring, and laminating upper glass. Preparation of optical waveguide substrate is to clean and surface treat glass or other transparent substrates to remove dust, grease, etc. on the surface, and increase the adhesion of subsequent holographic polymers to the substrate. Holographic polymer coating is to evenly coat the photocurable holographic polymer on the substrate, usually using spin coating, spraying and other methods to accurately control the thickness of the polymer coating. Holographic exposure and photocuring are to use laser for holographic exposure, set appropriate exposure parameters, including light intensity, exposure time and angle, and place the exposed substrate under ultraviolet light for photocuring, so that the polymer changes from liquid or semi-solid to solid. Laminating the upper glass is to align another glass substrate with the cured holographic optical waveguide, and use appropriate pressure and temperature to laminate the upper glass on the holographic optical waveguide to ensure its sealing and flatness.

[0004] The current production process of volume holographic waveguide technology has made some progress, but further research is still needed in terms of process optimization, cost control, and improving production efficiency and quality consistency to promote the further development and application of this technology. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a volume holographic optical waveguide, which optimizes the preparation process, adds the operation of side gluing, improves the quality and efficiency of production, and ensures that the produced products have high repeatability and consistency.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a volume holographic optical waveguide, the method comprising:

[0008] providing a first substrate and a second substrate;

[0009] forming a holographic polymer layer on a surface of the second substrate;

[0010] Laminating the surface of the first substrate to the holographic polymer layer on the surface of the second substrate to obtain a substrate assembly;

[0011] Applying glue to the side edges of the substrate assembly;

[0012] Holographic exposure is performed on the substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide.

[0013] The preparation method provided by the present invention can not only avoid the deviation of the substrate assembly after bonding during subsequent process operations such as holographic exposure by optimizing the preparation process and applying glue to the side of the substrate assembly after bonding, but also avoid the dripped refractive index matching liquid from seeping into the junction of the first substrate and the second substrate, thereby affecting the effect of the holographic exposure process. The preparation method can improve the quality and efficiency of volume holographic optical waveguide production and ensure that the produced products have high repeatability and consistency.

[0014] As a preferred technical solution of the present invention, the sizes of the first substrate and the second substrate match each other.

[0015] In the present invention, the materials of the first substrate and the second substrate are not specifically limited, and those skilled in the art may select them according to actual needs, for example, glass and / or resin may be selected.

[0016] A first substrate and a second substrate are provided, comprising:

[0017] providing an original first substrate and an original second substrate;

[0018] cleaning the original first substrate and the original second substrate;

[0019] Drying the cleaned original first substrate and the original second substrate;

[0020] Determine whether the cleanliness of the dried original first substrate and the original second substrate is qualified. If so, obtain the first substrate and the second substrate. If not, repeat the cleaning operation until the cleanliness of the original first substrate and the original second substrate is qualified.

[0021] Preferably, cleaning the original first substrate and the original second substrate comprises:

[0022] Using a cleaning agent to wipe the surfaces of the original first substrate and the original second substrate;

[0023] The surfaces of the wiped original first substrate and the original second substrate are cleaned by pure water washing or ultrasonic cleaning.

[0024] In the present invention, the cleanliness of the first substrate and the second substrate must meet the use requirements to avoid affecting the subsequent holographic exposure process and causing the optical waveguide performance to deteriorate.

[0025] As a preferred technical solution of the present invention, after providing the first substrate and before laminating the first substrate, the method further includes:

[0026] A release agent is coated on the surface of the first substrate to form a release layer.

[0027] It should be noted that the release agent is to prevent the formed polymer material from adhering to the substrate, and a type of isolation film is applied between the formed polymer material and the substrate, so that the substrate can be easily removed from the formed polymer material, while ensuring that the surface quality of the formed polymer material is intact. Therefore, the release layer provided in the present invention solves the problem that the holographic polymer layer is difficult to be separated from the upper substrate. In addition, because the refractive index of the release layer and the substrate matches, it is equivalent to only increasing the thickness of the first substrate, which will not affect the total reflection during the imaging process, and thus has no effect on the volume holographic pattern formed by the subsequent holographic exposure.

[0028] In the present invention, it is only necessary to ensure that the thickness of the release layer obtained by coating is ≥20nm. If the release layer is too thin, it cannot provide sufficient release force, resulting in difficulty in peeling, which not only affects production efficiency but also may damage the volume holographic grating structure and affect the display effect.

[0029] Preferably, the release agent includes any one of an organic silicon release agent, a silicon fluoride release agent or a polyethylene release agent.

[0030] Preferably, the coating method includes any one of dip coating, spray coating or spin coating.

[0031] Preferably, if the release agent is solvent-based, it is cured after coating.

[0032] In the present invention, if the release agent is a solvent type, it needs to be thermally cured after coating to avoid affecting the release effect and durability.

[0033] As a preferred technical solution of the present invention, the material of the holographic polymer layer includes any one of holographic polymer dispersed liquid crystal (HPDLC), photocurable holographic polymer or halide.

[0034] The holographic polymer layer is formed by any one of spin coating, spray coating or printing.

[0035] As a preferred technical solution of the present invention, the bonding specifically includes:

[0036] The release layer on the surface of the first substrate is attached to the holographic polymer layer on the surface of the second substrate.

[0037] Preferably, after the lamination, the method further comprises: confirming whether there are bubbles in the substrate assembly, and if so, defoaming the substrate assembly.

[0038] As a preferred technical solution of the present invention, applying glue on the side of the substrate assembly includes:

[0039] Using a glue coating device to apply glue at the side joint between the first substrate and the second substrate after bonding;

[0040] The substrate assembly after setting the glue is cured.

[0041] In the present invention, the glue coating area at the side junction between the first substrate and the second substrate can be determined according to actual needs, as long as it is ensured that the substrate assembly does not shift during subsequent processing and the refractive index matching liquid does not seep into the junction between the first substrate and the second substrate.

[0042] It should be noted that by setting glue at the side joint between the first substrate and the second substrate after bonding and then curing it, it is ensured that the substrate assembly does not shift during subsequent processing, and the emissivity matching liquid is prevented from seeping into the joint between the first substrate and the second substrate to avoid affecting the holographic exposure process, thereby ensuring that the produced products have high repeatability and consistency.

[0043] As a preferred technical solution of the present invention, the viscosity of the glue is 20000-500000 mPa·s, for example, it can be 20000 mPa·s, 50000 mPa·s, 80000 mPa·s, 100000 mPa·s, 150000 mPa·s, 200000 mPa·s, 250000 mPa·s, 300000 mPa·s, 350000 mPa·s, 400000 mPa·s, 450000 mPa·s or 500000 mPa·s, etc.

[0044] It should be noted that the viscosity of the glue is controlled within the range of 20000-500000 mPa·s to prevent it from penetrating downward after the glue is applied and to ensure smooth glue discharge from the hose needle.

[0045] Preferably, the glue includes any one of liquid glue, UV debonding glue or hydrosol.

[0046] As a preferred technical solution of the present invention, holographic exposure is performed on the substrate assembly after the side glue coating, including:

[0047] exposing the holographic polymer layer in the substrate assembly using a coherent light source to form a volume holographic pattern on the holographic polymer layer;

[0048] curing the exposed substrate assembly;

[0049] According to product requirements, the first substrate in the substrate assembly is retained or removed to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure.

[0050] In the present invention, a volume holographic pattern can be formed at the molecular level by using a coherent light source for holographic exposure, and then solidification is performed to transform the material from a liquid state to a solid state. Finally, according to product requirements, the first substrate is retained or removed to obtain a volume holographic optical waveguide.

[0051] As a preferred technical solution of the present invention, after removing the first substrate in the substrate assembly to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure, the following conditions are also included:

[0052] (A) providing a first substrate;

[0053] forming a second holographic polymer layer on the surface of the second substrate on which the volume holographic pattern is formed;

[0054] Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly;

[0055] Applying glue to the side edge of the second substrate assembly;

[0056] Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or

[0057] (B) providing a first substrate;

[0058] forming a second holographic polymer layer on the other surface of the second substrate where the volume holographic pattern is formed;

[0059] Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly;

[0060] Applying glue to the side edge of the second substrate assembly;

[0061] Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or

[0062] (C) repeatedly performing the steps of providing a first substrate and a second substrate to performing holographic exposure on the substrate assembly after the side glue coating, and removing the first substrate in the substrate assembly;

[0063] The volume holographic patterns in the two obtained volume holographic optical waveguides are laminated to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure.

[0064] It should be noted that the first substrate provided in the above steps can be a brand new first substrate or a first substrate removed from a substrate assembly, but operations such as cleaning are required before use to ensure that the cleanliness of the first substrate meets the use requirements to avoid affecting the subsequent holographic exposure process and causing problems such as degradation of the optical waveguide performance.

[0065] In the present invention, a volume holographic optical waveguide with a two-layer volume holographic grating structure can be produced in a variety of ways, and all of them can ensure that the produced products have high repeatability and consistency. It is further preferred to perform the above operation on the first substrate with a release layer to improve production efficiency.

[0066] As a preferred technical solution of the present invention, after removing the first substrate in the substrate assembly to obtain a volume holographic optical waveguide, the method further includes repeating step (A) several times to obtain a volume holographic optical waveguide having several layers of volume holographic grating structures.

[0067] It should be noted that, during the process of repeatedly performing step (A) for several times, the first substrate in the substrate assembly needs to be removed before forming several holographic polymer layers on the surface of the volume holographic pattern. The volume holographic optical waveguide product having several layers of volume holographic grating structure finally obtained can retain or remove the first substrate in the substrate assembly according to product requirements.

[0068] In the present invention, by repeating the above steps, a multi-layer grating structure can be prepared to improve the degree of freedom of combination.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) The preparation method provided by the present invention further controls the viscosity range of the glue by applying glue to the side of the laminated substrate assembly, thereby preventing the laminated substrate assembly from shifting during subsequent process operations such as holographic exposure, and preventing the refractive index matching liquid from seeping into the junction between the first substrate and the second substrate, thereby affecting the effect of the holographic exposure process; by optimizing the preparation process, the quality and efficiency of production are guaranteed, and the products produced are ensured to have high repeatability and consistency;

[0071] (2) In the preparation method provided by the present invention, a release layer is covered on the surface of the first substrate, so that the first substrate can be easily removed from the formed holographic polymer layer, while ensuring that the surface quality of the formed holographic polymer layer is good;

[0072] (3) The preparation method provided by the present invention can increase the multi-layer volume holographic grating structure and improve the degree of freedom of combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a schematic diagram of a first glass substrate provided in Example 2 after a release layer is formed on the surface of the first glass substrate.

[0074] Figure 2 This is a schematic diagram of the second glass substrate provided in Example 2 after a holographic polymer layer is formed on the surface thereof.

[0075] Figure 3 It is a schematic diagram of the first glass substrate and the second glass substrate provided in Example 2 after being bonded together.

[0076] Figure 4 This is a schematic diagram of applying glue on the side of a glass substrate assembly provided in Example 2.

[0077] Figure 5 It is a schematic diagram of the volume holographic optical waveguide with a two-layer volume holographic grating structure obtained in Example 6.

[0078] Among them, 1 is a first glass substrate, 2 is a second glass substrate, 3 is a release layer, 4 is a first photocurable holographic polymer layer, 5 is glue, 6 is a fourth glass substrate, 7 is a volume holographic pattern a, and 8 is a volume holographic pattern b. DETAILED DESCRIPTION

[0079] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0080] A specific embodiment of the present invention provides a method for preparing a volume holographic optical waveguide, the preparation method comprising:

[0081] (1) providing a first substrate and a second substrate;

[0082] Wherein, the sizes of the first substrate and the second substrate match each other.

[0083] Specifically, a first substrate and a second substrate are provided, including:

[0084] providing an original first substrate and an original second substrate;

[0085] cleaning the original first substrate and the original second substrate;

[0086] drying the original first substrate and the original second substrate;

[0087] It is determined whether the cleanliness of the original first substrate and the original second substrate is qualified. If so, the first substrate and the second substrate are obtained. If not, the cleaning operation is repeated until the cleanliness of the original first substrate and the original second substrate is qualified.

[0088] The qualified standard of cleanliness is that there are no stains or water marks on the surface of the substrate.

[0089] Further, cleaning the original first substrate and the original second substrate includes:

[0090] Using a cleaning agent to wipe the surfaces of the original first substrate and the original second substrate;

[0091] The surfaces of the wiped original first substrate and the original second substrate are cleaned by pure water washing or ultrasonic cleaning.

[0092] In some embodiments, the cleaning agent includes cleaning fluid or alcohol.

[0093] In some embodiments, the wiping method is: wiping with a dust-free cloth or a cotton swab in a circular motion to remove dust on the surface of the substrate.

[0094] In the present application, the cleanliness of the first substrate and the second substrate must meet the use requirements to avoid affecting the subsequent holographic exposure process and causing the performance of the optical waveguide to deteriorate.

[0095] (2) forming a holographic polymer layer on the surface of the second substrate;

[0096] Wherein, the material of the holographic polymer layer includes any one of holographic polymer dispersed liquid crystal, photocurable holographic polymer or halide.

[0097] Specifically, there is no specific limitation on the components of the photocurable holographic polymer material, and those skilled in the art may select the materials according to the actual situation, or may select the materials provided by Chinese Patent No. 202311231430X or 202311230388X.

[0098] In some embodiments, the holographic polymer layer is formed by any one of spin coating, spray coating or printing.

[0099] When preparing the holographic polymer layer, it is necessary to ensure that the working environment is dust-free to avoid bubbles and impurities on the surface of the material and the substrate.

[0100] Specifically, the spin coating method uses a coating device to drop the material on the center of the substrate surface, and rotates the substrate at a constant speed to spread the material evenly; the spray coating method uses a spraying device, such as air spraying or electrostatic spraying, to evenly spray the material on the substrate surface; the printing method uses an inkjet printing device to accurately print the material at a predetermined position on the substrate surface under computer control.

[0101] (3) laminating the first substrate to the holographic polymer layer on the surface of the second substrate to obtain a substrate assembly;

[0102] Wherein, after the lamination, the method further comprises:

[0103] Check whether there are bubbles in the substrate assembly, and if so, defoam the substrate assembly.

[0104] In the present application, a bonding device is used to bond the first substrate and the second substrate, and the composition and structure of the bonding device are not specifically limited, as long as the first substrate and the second substrate can be bonded together.

[0105] The bonding device used in the present invention is mainly composed of a sheet-placing mold and a moving module. The sheet-placing mold has two customized grooves for placing two substrates to be bonded, which is conducive to more accurate bonding and alignment; the moving module is located on the beam above the sheet-placing mold, and there are supporting frames on both sides of the beam. A telescopic arm with a lifting shaft is installed under the moving module. The moving module moves horizontally through the beam, and the telescopic arm moves vertically through the lifting shaft. In addition, a suction nozzle is set on the telescopic arm, and a vacuum adsorption method is adopted.

[0106] Furthermore, the bonding process of the present invention specifically includes: placing the solidified holographic polymer layer on the surface of the second substrate upward, moving the suction nozzle to the first substrate groove position of the sheet placement mold to suck up the first substrate, and then moving to the second substrate groove position and placing it, so that the first substrate is bonded to cover the solidified holographic polymer layer on the surface of the second substrate.

[0107] During the bonding process, on the one hand, bubbles and wrinkles must be avoided to ensure the flatness of the bonding surface; on the other hand, the precise matching of the dimensions between the first substrate and the second substrate must be ensured to avoid poor bonding due to excessive tolerance. The dimensional tolerance of the substrate itself is ±0.05mm.

[0108] In some embodiments, if bubbles appear after the first substrate and the second substrate are attached, they can be placed in a vacuum degassing machine or a high-pressure degassing machine for degassing, and appropriate parameters can be selected according to the characteristics of the materials to ensure the best degassing effect.

[0109] Specifically, the vacuum degassing machine reduces the air pressure under a vacuum environment, causing the bubbles in the material to expand and escape. Place the bonded substrate assembly in the vacuum degassing machine, seal the degassing chamber, start the vacuum pump, and gradually reduce the internal air pressure. The vacuum degree is set to 20-50 mmHg, the pressure holding time is 20-30 minutes, and the temperature is room temperature - 60 ° C. Observe whether the bubbles rise to the surface and disappear, and perform multiple degassing cycles if necessary. After the degassing is completed, slowly release the vacuum and remove the substrate assembly.

[0110] Specifically, the high-pressure degassing machine applies high pressure to make the bubbles in the material diffuse rapidly and detach from the material under the action of pressure. Place the bonded substrate assembly in the high-pressure degassing machine, start the degassing machine, and the liquid passes through the degassing chamber under the action of high pressure, and the bubbles are quickly separated. The set working pressure is 0.2-0.6MPa, the processing time is 20-30min, and the temperature is room temperature-60℃. Observe whether the bubbles are effectively removed, and adjust the relevant parameters if necessary. After the degassing is completed, turn off the degassing machine and take out the substrate assembly.

[0111] (4) applying glue to the side edges of the substrate assembly;

[0112] Wherein, applying glue on the side of the substrate assembly includes:

[0113] Using a glue coating device to apply glue at the side joint between the first substrate and the second substrate after bonding;

[0114] The substrate assembly after setting the glue is cured.

[0115] In some embodiments, the glue coating area at the side junction between the first substrate and the second substrate can be determined according to actual needs, as long as it is ensured that the substrate assembly does not shift during subsequent processing and the refractive index matching liquid does not seep into the junction between the first substrate and the second substrate.

[0116] In the present application, glue is set at the side joint between the first substrate and the second substrate after bonding and then cured to ensure that the substrate assembly does not shift during subsequent processing, and to prevent the emissivity matching liquid from seeping into the joint between the first substrate and the second substrate to avoid affecting the effect of the holographic exposure process, thereby ensuring that the produced products have high repeatability and consistency.

[0117] Specifically, the substrate assembly is placed on the substrate support column of the glue coating equipment by using a glue coating device. The substrate support column has multiple small holes, which can vacuum absorb the substrate assembly. The substrate support column rotates at a low speed manually or electrically controlled. The needle of the glue hose applies a circle of glue along the side edge of the substrate assembly. The glue covers the gap between the first substrate and the second substrate to ensure the continuity and uniformity of the glue line. After applying the glue on the side, it is cured. The curing method is determined by the type of glue.

[0118] In some embodiments, the viscosity of the glue is 20,000-500,000 mPa·s.

[0119] In this application, the viscosity of the glue needs to be controlled within the range of 20000-500000 mPa·s, which not only prevents it from penetrating downward after the glue is applied, but also ensures smooth glue discharge from the hose needle.

[0120] In some embodiments, the glue includes any one of liquid glue, UV debonding glue or hydrosol.

[0121] Specifically, different types of glue correspond to different curing and degumming methods.

[0122] Furthermore, conventional liquid glues include Loctite's UV glue 352, Gaotu's UV glue 3523 or Mitsubishi Chemical's UV-3630ID80. Conventional liquid glue curing methods include thermal curing, ultraviolet curing or moisture curing. Among them, thermal curing is to volatilize the solvent in the glue by heating, and the glue is cured. Moisture curing is to use moisture in the air to react with the glue to promote the curing of the glue. Ultraviolet curing is to induce the reaction of the photosensitizer in the glue through ultraviolet irradiation, so as to promote the rapid curing of the glue. The conventional liquid glue removal method is to use a tool such as a scraper to physically scrape off the cured glue, or use a specific chemical solvent to dissolve the glue, or soften the glue by heating for easy removal.

[0123] Furthermore, UV adhesive removers include Suzhou Jingwei's JN01, etc. The curing methods of UV adhesive removers include ultraviolet curing, dual curing or photothermal curing. Among them, ultraviolet curing is the most common curing method, which quickly cures the glue through ultraviolet irradiation. Dual curing combines ultraviolet curing and moisture curing to improve the bonding strength and stability of the glue. Photothermal curing combines light curing and heat curing, and is suitable for temperature-sensitive applications. The UV adhesive remover is removed by reducing the adhesion through appropriate amount of ultraviolet irradiation. Some water-soluble UV adhesive removers can also be removed by water dissolution when necessary.

[0124] Furthermore, hydrosols include SC9108 from Sanxia New Materials, HR-8787 from Huirui Adhesives, or G98316 from Gulebang. The curing methods of hydrosols include dry curing, thermal curing, or ultraviolet curing. Among them, dry curing is to remove moisture by natural drying or forced drying to promote the curing of the glue. Thermal curing accelerates the evaporation of water molecules by heating to promote the curing of the glue. Ultraviolet curing is that some hydrosols can also undergo a curing reaction under ultraviolet light. The way to remove the hydrosol is to soak it in clean water, allow the glue to absorb water and soften, and then remove it, or put it in an ultrasonic cleaner for ultrasonic removal.

[0125] (5) Performing holographic exposure on the substrate assembly after the side coating with glue to obtain a volume holographic optical waveguide.

[0126] The holographic exposure of the substrate assembly after the side glue coating is performed includes:

[0127] exposing the holographic polymer layer in the substrate assembly using a coherent light source to form a volume holographic pattern on the holographic polymer layer;

[0128] curing the exposed substrate assembly;

[0129] According to product requirements, the first substrate in the substrate assembly is retained or removed to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure.

[0130] In some embodiments, a light-curable volume holographic polymer film of a substrate assembly is exposed by forming interference fringes of light and dark by laser, thereby forming a volume holographic pattern at the molecular level.

[0131] Furthermore, by controlling the exposure intensity and exposure time and recording the exposure angle, the accuracy of the grating period and the grating stripe inclination angle is ensured. The exposed substrate assembly is placed under a UV curing device for light curing to transform the material from liquid to solid. The UV light needs to be irradiated evenly to ensure that the material is completely cured and to avoid the problem of partial uncuring or over-curing.

[0132] In some embodiments, the finished volume holographic optical waveguide can choose to retain or remove the first substrate according to product requirements. If the first substrate is retained, the preparation of the volume holographic optical waveguide is directly completed. If the first substrate is removed, first select a suitable degumming method according to the physical properties of the glue used for side coating. After degumming, take out the first substrate, and be careful not to scratch the volume holographic pattern on the photocurable volume holographic polymer film during the process.

[0133] The preparation method provided in the present application further includes: after step (1) providing the first substrate, and before step (3) laminating the first substrate, it also includes: forming a release layer on the surface of the first substrate.

[0134] It should be noted that the release agent selected in the present invention is to prevent the formed polymer material from adhering to the substrate. By applying a layer of isolation film between the formed polymer material and the substrate, the substrate can be easily removed from the formed polymer material while ensuring that the surface quality of the formed polymer material is intact. In addition, since the refractive index of the release layer and the substrate matches, it is equivalent to only increasing the thickness of the first substrate, which will not affect the total reflection during the imaging process, and thus has no effect on the volume holographic pattern formed by the subsequent holographic exposure.

[0135] Specifically, forming a release layer on the surface of the first substrate includes:

[0136] A release agent is coated on the surface of the first substrate.

[0137] In some embodiments, it is sufficient to ensure that the thickness of the release layer obtained by coating is ≥ 20 nm. If the release layer is too thin, it cannot provide sufficient release force, resulting in difficulty in peeling, which not only affects production efficiency but also may damage the volume holographic grating structure and affect the display effect.

[0138] Furthermore, the release agent includes any one of an organic silicon release agent, a silicon fluoride release agent or a polyethylene release agent.

[0139] In some embodiments, the release agent specifically comprises Wacker Chemical's 985CN silicone release agent, Taiwan Fluoro Technology's solvent-based TF-41F03 fluorine-based release agent or Meigu Chemical's 1228-21N water-based non-silicone release agent, etc.

[0140] In some embodiments, the coating method includes any one of dip coating, spray coating or spin coating.

[0141] Furthermore, if the release agent is solvent-based, curing is performed after coating.

[0142] In some embodiments, the curing includes placing the first substrate in an oven at a temperature of 130° C. for curing for 10 seconds to ensure that the release agent is completely cured. If the release agent is not completely cured, its release effect and durability may be affected.

[0143] Furthermore, the bonding specifically includes:

[0144] The release layer on the surface of the first substrate is attached to the holographic polymer layer on the surface of the second substrate.

[0145] In some embodiments, the laminating process specifically includes: placing the first substrate with the release layer solidified on the surface facing downward, placing the bottom surface of the first substrate facing upward, and placing the second substrate oppositely. The suction nozzle moves to the first substrate groove position of the sheet placement mold to suck up the first substrate, and then moves to the second substrate groove position and places it, so that the release layer solidified on the surface of the first substrate is laminated and covers the holographic polymer layer solidified on the surface of the second substrate.

[0146] The preparation method provided in the present application further includes: after removing the first substrate in the substrate assembly to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure, the method further includes the following:

[0147] (A) providing a first substrate;

[0148] forming a second holographic polymer layer on the surface of the second substrate on which the volume holographic pattern is formed;

[0149] Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly;

[0150] Applying glue to the side edge of the second substrate assembly;

[0151] Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or

[0152] (B) providing a first substrate;

[0153] forming a second holographic polymer layer on the other surface of the second substrate where the volume holographic pattern is formed;

[0154] Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly;

[0155] Applying glue to the side edge of the second substrate assembly;

[0156] Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or

[0157] (C) repeatedly performing the steps of providing a first substrate and a second substrate to performing holographic exposure on the substrate assembly after the side glue coating, and removing the first substrate in the substrate assembly;

[0158] The volume holographic patterns in the two obtained volume holographic optical waveguides are laminated to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure.

[0159] It should be noted that the first substrate provided in the above steps can be a brand new first substrate or a first substrate removed from a substrate assembly, but operations such as cleaning are required before use to ensure that the cleanliness of the first substrate meets the use requirements to avoid affecting the subsequent holographic exposure process and causing problems such as degradation of the optical waveguide performance.

[0160] In the present application, a volume holographic optical waveguide with a two-layer volume holographic grating structure can be produced in a variety of ways, and all of them can ensure that the produced products have high repeatability and consistency. It is further preferred to perform the above operation on the first substrate with a release layer to improve production efficiency.

[0161] Furthermore, after removing the first substrate in the substrate assembly to obtain the volume holographic optical waveguide, the method further includes repeating step (A) several times to obtain a volume holographic optical waveguide having several layers of volume holographic grating structures.

[0162] It should be noted that, during the process of repeatedly performing step (A) for several times, the first substrate in the substrate assembly needs to be removed before forming several holographic polymer layers on the surface of the volume holographic pattern. The volume holographic optical waveguide product having several layers of volume holographic grating structure finally obtained can retain or remove the first substrate in the substrate assembly according to product requirements.

[0163] In the present application, by repeating the above steps, a multilayer grating structure can be prepared to improve the degree of freedom of combination.

[0164] The following examples describe the contents disclosed in this application in more detail. The examples are only for illustrative purposes, as various modifications and variations within the scope of the disclosure of this application are obvious to those skilled in the art. Unless otherwise specified, all raw materials and instruments used in the examples are commercially available. The specific operations of providing the glass substrate in the following specific embodiments are all carried out according to the method provided in Example 1.

[0165] Example 1

[0166] This embodiment provides a method for preparing a volume holographic optical waveguide, the method comprising the following steps:

[0167] (1) Providing a first glass substrate and a second glass substrate, specifically comprising:

[0168] providing an original first glass substrate and an original second glass substrate;

[0169] cleaning the original first glass substrate and the original second glass substrate;

[0170] Drying the cleaned original first glass substrate and the original second glass substrate;

[0171] Determine whether the cleanliness of the dried original first glass substrate and the original second glass substrate is qualified, if so, obtain the first glass substrate and the second glass substrate, if not, repeat the cleaning operation until the cleanliness of the original first glass substrate and the original second glass substrate is qualified;

[0172] Wherein, cleaning the original first glass substrate and the original second glass substrate comprises:

[0173] Using a cleaning agent to wipe the surfaces of the original first glass substrate and the original second glass substrate;

[0174] The surfaces of the wiped original first glass substrate and the original second glass substrate are cleaned by pure water washing or ultrasonic cleaning.

[0175] (2) Spraying a photocurable holographic polymer material onto the surface of the second glass substrate obtained in step (1) to form a first photocurable holographic polymer layer.

[0176] (3) using a laminating device to laminate the first glass substrate obtained in step (1) onto the first photocured holographic polymer layer on the surface of the second glass substrate obtained in step (2) to obtain a glass substrate assembly;

[0177] And confirm whether there are bubbles in the glass substrate assembly. If so, use a vacuum degassing machine to degas the glass substrate assembly.

[0178] (4) using a glue coating device to apply glue to the side joints of the glass substrate assembly after bonding in step (3), and then thermally curing the glass substrate assembly after the glue is applied;

[0179] Wherein, the glue is Loctite UV glue 352 with a viscosity of 20000 mPa·s.

[0180] (5) exposing the first photocurable holographic polymer layer in the glass substrate assembly obtained in step (4) using a coherent light source to form a volume holographic pattern on the first photocurable holographic polymer layer, and then photocuring the exposed glass substrate assembly to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure.

[0181] In this embodiment, the preparation method provided is simple to produce and highly efficient, the obtained volume holographic optical waveguide product is of high quality, and the produced product has a high degree of repeatability and consistency.

[0182] Example 2

[0183] This embodiment provides a method for preparing a volume holographic optical waveguide, the method comprising the following steps:

[0184] (1) A first glass substrate 1 and a second glass substrate 2 are provided.

[0185] (2) Wacker Chemical's 985CN organic silicon release agent is sprayed on the surface of the first glass substrate 1 obtained in step (1) to form a release layer 3 with a thickness of 40nm. Figure 1 shown.

[0186] (3) Spraying the photocurable holographic polymer material onto the surface of the second glass substrate 2 obtained in step (1) to form a first photocurable holographic polymer layer 4, such as Figure 2 shown.

[0187] (4) Using a laminating device, the release layer 3 on the surface of the first glass substrate obtained in step (2) is laminated and covered on the first photocured holographic polymer layer 4 on the surface of the second glass substrate obtained in step (3) to obtain a glass substrate assembly, such as Figure 3 As shown;

[0188] And confirm whether there are bubbles in the glass substrate assembly. If so, use a vacuum degassing machine to degas the glass substrate assembly.

[0189] (5) Use a glue coating device to apply glue 5 on the side joints of the glass substrate assembly after bonding in step (4), such as Figure 4 As shown, the glass substrate assembly coated with glue is then thermally cured;

[0190] Wherein, the glue is Loctite UV glue 352 with a viscosity of 20000 mPa·s.

[0191] (6) using a coherent light source to expose the first photocurable holographic polymer layer in the glass substrate assembly obtained in step (5) to form a volume holographic pattern on the first photocurable holographic polymer layer, and then photocuring the exposed glass substrate assembly, and finally removing the side glue 5 and the first glass substrate 1 in turn to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure.

[0192] In this embodiment, the preparation method provided is simple to produce and highly efficient, the obtained volume holographic optical waveguide product is of high quality, and the produced product has a high degree of repeatability and consistency.

[0193] Example 3

[0194] This embodiment provides a method for preparing a volume holographic optical waveguide. Step (1) adopts the operation provided in Example 2, and only steps (2) to (6) are adjusted, which specifically includes:

[0195] (2) A solvent-based TF-41F03 fluorine-based release agent produced by Taiwan Fluoro Technology was dip-coated on the surface of the first glass substrate obtained in step (1), and then thermally cured to form a release layer with a thickness of 50 nm.

[0196] (3) Spraying the photocurable holographic polymer material onto the surface of the second glass substrate obtained in step (1) to form a first photocurable holographic polymer layer.

[0197] (4) using a laminating device to laminate the release layer on the surface of the first glass substrate obtained in step (2) onto the first photocured holographic polymer layer on the surface of the second glass substrate obtained in step (3) to obtain a glass substrate assembly;

[0198] And confirm whether there are bubbles in the glass substrate assembly. If so, use a high-pressure degassing machine to degas the glass substrate assembly.

[0199] (5) using a glue coating device to apply glue to the side joints of the glass substrate assembly after the bonding in step (4), and then ultraviolet light curing the glass substrate assembly after the glue is applied;

[0200] Wherein, the glue is SC9108 of Sanxia New Materials with a viscosity of 150000 mPa·s.

[0201] (6) Exposing the first photocurable holographic polymer layer in the glass substrate assembly obtained in step (5) using a coherent light source to form a volume holographic pattern on the first photocurable holographic polymer layer, and then photocuring the exposed glass substrate assembly to obtain a volume holographic optical waveguide.

[0202] In this embodiment, the preparation method provided is simple to produce and highly efficient, the obtained volume holographic optical waveguide product is of high quality, and the produced product has a high degree of repeatability and consistency.

[0203] Example 4

[0204] This embodiment provides a method for preparing a volume holographic optical waveguide, which further includes step (6) based on the preparation method provided in embodiment 1:

[0205] Removing the first glass substrate in the volume holographic optical waveguide prepared in Example 1;

[0206] providing a third glass substrate;

[0207] Spraying a photocurable holographic polymer material onto the surface of the second glass substrate on which the volume holographic pattern is formed to form a second photocurable holographic polymer layer;

[0208] Using a laminating device to laminate a third glass substrate onto the second photocured holographic polymer layer on the surface of the second glass substrate to obtain a second glass substrate assembly; and confirming whether there are bubbles in the second glass substrate assembly, and if so, using a vacuum degassing machine to degas the second glass substrate assembly;

[0209] Using a glue coating device to apply glue to the side joints of the laminated second glass substrate assembly, and then thermally curing the glued second glass substrate assembly; wherein the glue is Loctite UV glue 352 with a viscosity of 20000 mPa·s;

[0210] The second photocurable holographic polymer layer in the obtained second glass substrate assembly is exposed using a coherent light source to form a second volume holographic pattern on the second photocurable holographic polymer layer, and then the exposed second glass substrate assembly is photocured to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure.

[0211] In this embodiment, the preparation method provided can obtain a volume holographic optical waveguide product with a two-layer grating structure, thereby improving the degree of freedom of combination, and the produced product has a high degree of repeatability and consistency.

[0212] Example 5

[0213] This embodiment provides a method for preparing a volume holographic optical waveguide, which further includes step (7) based on the preparation method provided in embodiment 2:

[0214] providing a third glass substrate;

[0215] Wacker Chemical 985CN organic silicon release agent is sprayed on the surface of the obtained third glass substrate to form a release layer with a thickness of 40 nm;

[0216] Spraying a photocurable volume holographic polymer material onto the surface of the volume holographic optical waveguide formed with the volume holographic pattern obtained in Example 2 to form a second photocurable volume holographic polymer layer;

[0217] Using a laminating device to laminate the release layer on the surface of the third glass substrate to the second photocured holographic polymer layer on the surface of the second glass substrate to obtain a second glass substrate assembly; and confirming whether there are bubbles in the second glass substrate assembly, and if so, using a vacuum degassing machine to degas the second glass substrate assembly;

[0218] Using a glue coating device to apply glue to the side joints of the laminated second glass substrate assembly, and then thermally curing the glued second glass substrate assembly; wherein the glue is Loctite UV glue 352 with a viscosity of 20000 mPa·s;

[0219] The second photocurable holographic polymer layer in the obtained second glass substrate assembly is exposed using a coherent light source to form a second volume holographic pattern on the second photocurable holographic polymer layer, and then the exposed second glass substrate assembly is photocured, and finally the side glue and the third glass substrate are removed in sequence to obtain a volume holographic optical waveguide with a two-layer volume holographic grating structure.

[0220] In this embodiment, the preparation method provided can obtain a volume holographic optical waveguide product with a two-layer grating structure, thereby improving the degree of freedom of combination, and the produced product has a high degree of repeatability and consistency.

[0221] Example 6

[0222] This embodiment provides a method for preparing a volume holographic optical waveguide, which further includes step (7) based on the preparation method provided in embodiment 2:

[0223] providing a third glass substrate and a fourth glass substrate;

[0224] Wacker Chemical 985CN organic silicon release agent is sprayed on the surface of the obtained third glass substrate to form a release layer with a thickness of 60 nm;

[0225] spraying a photocurable holographic polymer material on the surface of the fourth glass substrate to form a photocurable holographic polymer layer;

[0226] Using a laminating device to laminate the release layer on the surface of the third glass substrate onto the photocured holographic polymer layer on the surface of the fourth glass substrate to obtain a second glass substrate assembly; and confirming whether there are bubbles in the second glass substrate assembly, and if so, using a vacuum degassing machine to degas the second glass substrate assembly;

[0227] A glue coating device is used to apply glue to the side joints of the laminated second glass substrate assembly, and then the glued second glass substrate assembly is thermally cured; wherein the glue is Loctite UV glue 352 with a viscosity of 20000 mPa·s.

[0228] Using a coherent light source to expose the photocurable volume holographic polymer layer in the obtained second glass substrate assembly to form a volume holographic pattern on the photocurable volume holographic polymer layer, and then photocuring the exposed second glass substrate assembly, and finally removing the side glue and the third glass substrate in sequence to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure;

[0229] Then, the volume holographic pattern (a) 7 on the surface of the volume holographic optical waveguide obtained in Example 2 is laminated and covered on the volume holographic pattern (b) 8 on the surface of the volume holographic optical waveguide obtained to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure, such as Figure 5 shown.

[0230] In this embodiment, the preparation method provided can obtain a volume holographic optical waveguide product with a two-layer grating structure, thereby improving the degree of freedom of combination, and the produced product has a high degree of repeatability and consistency.

[0231] Example 7

[0232] This embodiment provides a method for preparing a volume holographic optical waveguide. Based on the preparation method provided in Example 5, the method further comprises repeating the preparation method provided in Example 5 several times to obtain a volume holographic optical waveguide having several layers of volume holographic grating structures.

[0233] In this embodiment, the preparation method provided can obtain a volume holographic optical waveguide product with a multi-layer grating structure, thereby improving the degree of freedom of combination, and the produced product has a high degree of repeatability and consistency.

[0234] Example 8

[0235] This embodiment provides a method for preparing a volume holographic optical waveguide. Except that the viscosity of the glue in step (4) is 15000 mPa·s, other conditions are the same as those in embodiment 1.

[0236] In this embodiment, because the viscosity of the glue applied on the side is too low, it cannot effectively prevent the glass substrate assembly from shifting in the subsequent process, and there is a problem of downward penetration after the glue is applied, which in turn affects the effect of the holographic exposure process and causes a decrease in the quality of the resulting product.

[0237] Example 9

[0238] This embodiment provides a method for preparing a volume holographic optical waveguide. Except that the viscosity of the glue in step (4) is 550000 mPa·s, other conditions are the same as those in embodiment 1.

[0239] In this embodiment, because the viscosity of the glue applied on the side is too high, it is impossible to effectively ensure that the glue comes out of the needle of the hose smoothly, thereby affecting the glue coating efficiency.

[0240] Comparative Example 1

[0241] This comparative example provides a method for preparing a volume holographic optical waveguide. Except that step (4) is not performed, other conditions are the same as those in Example 1.

[0242] In this comparative example, since the side edges of the glass substrate assembly after bonding were not coated with glue, they were offset in the subsequent process, which in turn affected the holographic exposure process, resulting in a decrease in the quality of the resulting product, and it was not possible to ensure that the produced products had a high degree of repeatability and consistency.

[0243] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a volume holographic optical waveguide, characterized in that: The preparation method comprises: providing a first substrate and a second substrate; forming a holographic polymer layer on a surface of the second substrate; Laminating the first substrate to the holographic polymer layer on the surface of the second substrate to obtain a substrate assembly; Applying glue to the side edges of the substrate assembly; Holographic exposure is performed on the substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide.

2. The preparation method according to claim 1, characterized in that: The sizes of the first substrate and the second substrate match each other; A first substrate and a second substrate are provided, comprising: providing an original first substrate and an original second substrate; cleaning the original first substrate and the original second substrate; Drying the cleaned original first substrate and the original second substrate; Determine whether the cleanliness of the original first substrate and the original second substrate after drying is qualified, if so, obtain the first substrate and the second substrate, if not, repeat the cleaning operation until the cleanliness of the original first substrate and the original second substrate is qualified; Preferably, cleaning the original first substrate and the original second substrate comprises: Using a cleaning agent to wipe the surfaces of the original first substrate and the original second substrate; The surfaces of the wiped original first substrate and the original second substrate are cleaned by pure water washing or ultrasonic cleaning.

3. The preparation method according to claim 1, characterized in that: After providing the first substrate and before laminating the first substrate, the method further includes: Applying a release agent on the surface of the first substrate to form a release layer; Preferably, the release agent includes any one of an organic silicon release agent, a silicon fluoride release agent or a polyethylene release agent; Preferably, the coating method includes any one of dip coating, spray coating or spin coating; Preferably, if the release agent is solvent-based, it is cured after coating.

4. The preparation method according to claim 1, characterized in that: The material of the holographic polymer layer includes any one of holographic polymer dispersed liquid crystal, photocurable holographic polymer or halide; Preferably, the holographic polymer layer is formed by any one of spin coating, spray coating or printing.

5. The preparation method according to claim 1 or 3, characterized in that: The bonding specifically includes: Laminating the release layer on the surface of the first substrate to the holographic polymer layer on the surface of the second substrate; Preferably, after the lamination, the method further comprises: Confirm whether there are bubbles in the substrate assembly, and if so, defoam the substrate assembly.

6. The preparation method according to claim 1, characterized in that: Applying glue to the side of the substrate assembly includes: Using a glue coating device to apply glue at the side joint between the first substrate and the second substrate after bonding; The substrate assembly after setting the glue is cured.

7. The preparation method according to claim 6, characterized in that: The viscosity of the glue is 20000-500000 mPa·s; Preferably, the glue includes any one of liquid glue, UV debonding glue or hydrosol.

8. The preparation method according to claim 1 or 3, characterized in that: Holographic exposure is performed on the substrate assembly after the side glue coating, including: exposing the holographic polymer layer in the substrate assembly using a coherent light source to form a volume holographic pattern on the holographic polymer layer; curing the exposed substrate assembly; According to product requirements, the first substrate in the substrate assembly is retained or removed to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure.

9. The preparation method according to any one of claims 1 to 8, characterized in that: When the first substrate in the substrate assembly is removed to obtain a volume holographic optical waveguide having a layer of volume holographic grating structure, the following conditions are also included: (A) providing a first substrate; forming a second holographic polymer layer on the surface of the second substrate on which the volume holographic pattern is formed; Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly; Applying glue to the side edge of the second substrate assembly; Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or (B) providing a first substrate; forming a second holographic polymer layer on the other surface of the second substrate where the volume holographic pattern is formed; Laminating the first substrate onto the second holographic polymer layer on the surface of the second substrate to obtain a second substrate assembly; Applying glue to the side edge of the second substrate assembly; Performing holographic exposure on the second substrate assembly after the side edges are coated with glue to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure; or (C) repeatedly performing the steps of providing a first substrate and a second substrate to performing holographic exposure on the substrate assembly after the side glue coating, and removing the first substrate in the substrate assembly; The volume holographic patterns in the two obtained volume holographic optical waveguides are laminated to obtain a volume holographic optical waveguide having a two-layer volume holographic grating structure.

10. The preparation method according to claim 9, characterized in that: After removing the first substrate in the substrate assembly to obtain a volume holographic optical waveguide, the method further includes repeating step (A) several times to obtain a volume holographic optical waveguide having several layers of volume holographic grating structures.

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