A method for adjusting the thickness consistency of a grating structure region and a non-structure region

Abstract

The application provides a method for adjusting the thickness consistency of a grating structure region and a non-structure region. Through cooperation of multiple process steps, a first anti-sticking layer with low surface energy characteristics is preferentially constructed on the surface of the non-structure region, so as to inhibit the aggregation of the material in the subsequent first filling layer in the non-structure region. Then, the first filling layer is preferentially filled in the grating groove of the grating structure, and a first filling layer is formed. Finally, a second filling layer is arranged on the surface of the entire waveguide. Through twice filling, the material of the first filling layer is located in the grating groove, the first filling layer is pre-solidified, and the second filling layer is only arranged on the flat surface structure. The problem of thickness inconsistency between the grating structure region and the non-structure region is solved through "two-step filling + selective anti-sticking layer", so that the thickness of different regions is as consistent as possible, thereby effectively inhibiting optical display defects such as rainbow stripes, dispersion offset and diffraction efficiency reduction caused by thickness inconsistency.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a method for adjusting the thickness consistency between the structured and unstructured regions of a grating. Background Technology

[0002] Augmented reality (AR) display technology seamlessly integrates virtual optical display information with real-world environmental information. Diffractive waveguides, as a crucial core optical component in near-eye AR display devices, play a vital role in transmitting, coupling, and projecting virtual light signals. On one hand, ensuring the optical display quality of diffractive waveguides to allow users to clearly observe the real world is paramount. On the other hand, improving the drop resistance of diffractive waveguides under various conditions for long-term use to meet diverse application scenarios is also a critical technical challenge that urgently needs to be addressed by those skilled in the art.

[0003] In existing technologies, the conventional process involves placing a filler layer on one side of the grating structure region in a diffractive waveguide to improve its impact resistance while maintaining optical display performance. Specifically, a filler layer is placed in both the structural and unstructured regions of the grating. The applicant has found that while this method can improve optical display performance and impact resistance to some extent, differences in factors such as material shrinkage rate, coefficient of thermal expansion, adhesive viscosity, and grating gaps lead to different thicknesses between the structural and unstructured regions. This thickness deviation in the two regions is particularly problematic. The filler layer in the structural region is prone to "collapse," resulting in a reduced thickness and an uneven filler layer, which in turn causes optical display defects. Furthermore, the surface of the filler layer in the structural region, away from the grating, is uneven, and the thickness of the filler layer in the structural region differs significantly from that in the unstructured region. This significant difference in thickness affects the overall performance of the diffractive waveguide, which is unacceptable to those skilled in the art.

[0004] Therefore, improving the thickness consistency between the grating structure region and the unstructure region of the diffractive waveguide after the filling layer is set, especially ensuring that the overall thickness of the two regions is as equal as possible, in order to eliminate optical display problems caused by uneven thickness, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method for adjusting the thickness consistency between the grating structure region and the unstructured region, especially to prevent the formation of uneven planes after setting a filling layer on the grating structure region, while making the thickness of the grating structure region and the unstructured region in the diffractive waveguide as consistent as possible, thereby achieving the same or similar thickness between the grating structure region and the unstructured region, and improving the optical display effect.

[0006] This invention provides a method for adjusting the thickness consistency between the structured and unstructured regions of a grating, comprising the following steps:

[0007] S1: A substrate is provided, and a grating structure layer is formed on one side of the substrate. The grating structure layer includes a grating structure region and a non-structure region. The grating structure region includes a plurality of grating ridges and grating grooves.

[0008] S2: A first material layer is disposed on the surface of the grating structure region and the unstructure region, and the first material layer covers the entire surface of the grating structure layer;

[0009] S3: Pattern the first material layer, remove the first material layer located on the surface of the non-structured region, and retain the first material layer covering the grating structure region;

[0010] S4: A first anti-adhesion layer is provided on the surfaces of the grating structure region and the unstructure region; the surface energy of the unstructure region surface is improved based on the first anti-adhesion layer;

[0011] S5: Remove the first material layer and the first anti-adhesion layer covering the grating structure region, and retain the first anti-adhesion layer on the surface of the non-structure region;

[0012] S6: A first filling layer is provided in the grating structure region; the first filling layer fills the grating groove;

[0013] S7: Remove the first anti-adhesive layer covering the surface of the unstructured area to fully expose the surfaces of the unstructured area and the grating structure area;

[0014] S8: A second filling layer is provided on the exposed unstructured area and the grating structure area surface, so that the second filling layer covers the entire surface and performs surface planarization treatment.

[0015] S9: Solidify the second filling layer to obtain a diffractive waveguide.

[0016] Furthermore, in step S1, the grating structure layer is formed by nanoimprinting or etching.

[0017] Furthermore, the refractive index of the first filling layer is less than the refractive index of the substrate, and the refractive index of the second filling layer is equal to the refractive index of the first filling layer.

[0018] In some other embodiments, the refractive index of the second filling layer is greater than that of the first filling layer.

[0019] Furthermore, in step S6, the first filling layer is cured, and the next step is performed after curing; and the height of the first filling layer after curing in the grating groove is not greater than the height of the grating structure.

[0020] Furthermore, the viscosity of the first filler layer is greater than that of the second filler layer; the curing shrinkage rate of the first filler layer is less than that of the second filler layer.

[0021] In some other embodiments, the height of the first filler layer is greater than or equal to the height of the second filler layer.

[0022] In some other embodiments, in step S6, when the first filling layer is set, its height before curing is greater than the height of the grating structure, and when the first filling layer is in a liquid state before curing, the height difference between the first filling layer and the top of the grating structure is... , Limited to:

[0023] ;

[0024] in, The height difference between the first filling layer and the top of the grating structure before the first filling layer is cured; The height of the grating structure; The curing shrinkage rate of the first filler layer is denoted as .

[0025] The ratio of the height of the first filling layer after curing to the height of the grating structure is controlled between 0.85 and 1.

[0026] Furthermore, based on the above embodiments, in step S6, the volume of the first filling layer is set. ;

[0027] in, This represents the volume of the first filling layer; Indicates the duty cycle of the grating; The curing shrinkage rate of the first filler layer; The height of the grating structure is given.

[0028] Of course, furthermore, in step S8, the height of the spin-coated second filler layer... It meets the following conditions:

[0029]

[0030] in, Indicates the height of the second filler layer spin-coated; This indicates the curing shrinkage rate of the second filler layer; This indicates the height difference between the unstructured region and the top of the grating structure.

[0031] Meanwhile, this invention claims protection for a diffractive optical waveguide, which is prepared based on the method for adjusting the thickness consistency between the grating structure region and the unstructure region described in any of the foregoing embodiments;

[0032] Meanwhile, the present invention provides an augmented reality display device comprising the diffractive waveguide as described above.

[0033] In this application, through the coordination of multiple process steps, a first anti-adhesion layer with low surface energy characteristics is preferentially constructed on the surface of the unstructured area, thereby inhibiting the accumulation of material in the subsequent first filling layer in the unstructured area. Secondly, the first filling layer is preferentially filled into the grating groove of the grating structure to form the first filling layer. Then, the first anti-adhesion layer located in the unstructured area is removed, and finally, a second filling layer is applied to the entire surface of the waveguide. Through this two-stage filling method, the material of the first filling layer is located in the grating groove, preventing depressions caused by differences in factors such as large-area material shrinkage, thermal expansion, adhesive viscosity, and grating gaps. The grating grooves between the grating structures are pre-filled by pre-curing the first filling layer. The second filling layer is only applied to the surface structure located on the flat surface, including both the grating structure area and the unstructured area, and covers the entire surface. This application adjusts the large-area filling of the prior art to a two-stage filling method (large-area filling refers to simultaneously filling the grating groove and the entire surface of the grating structure at once). The first filling of the grating groove is followed by pre-curing, and the first anti-adhesion layer is removed before the second filling. After curing, the entire surface is filled a second time. This process, which combines surface energy regulation, selective filling, and structural pre-embedding, achieves consistent thickness control across regions. This avoids the large-area filling of grating grooves and unstructured areas in existing technologies. Compared to existing technologies, the "two-step filling + selective anti-sticking layer" approach solves the problem of inconsistent thickness between grating structure and unstructured areas. It significantly improves the unevenness of the grating structure area after the filling layer is applied, as well as the thickness deviation between the grating structure and unstructured areas. This ensures that the thickness of different areas is kept as consistent as possible, thereby effectively suppressing optical display defects such as rainbow patterns, dispersion shift, and reduced diffraction efficiency caused by uneven thickness.

[0034] Furthermore, through the process steps of this invention, the consistency of the filling layer thickness at different locations within the grating structure region can be ensured as much as possible, making the filling layer thickness at different locations within the grating structure region as equal as possible, or controlling the filling layer thickness deviation at different locations within the grating structure region within a certain threshold, thereby improving the uniformity and stability of the overall optical performance of the diffractive waveguide; compared with the prior art, it has unexpected technical effects. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of an ideal structure in the prior art where a filling layer is set on a grating structure;

[0037] Figure 2 This is a schematic diagram illustrating the actual structure of setting a filling layer on a grating structure in the prior art;

[0038] Figure 3 for Figure 1 and Figure 2 Enlarged view of the local structure corresponding to the structure in the image;

[0039] Figure 4 A flowchart illustrating the method provided by the present invention;

[0040] Figure 5 for Figure 4 Enlarged view of the local structure in step S6;

[0041] Figure 6 This is a schematic diagram of another structure of a diffraction grating obtained by the method of the present invention. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] like Figure 1 The diagram illustrates a method employed by those skilled in the art to improve the optical display effect of a diffraction grating while simultaneously enhancing the impact resistance of a diffraction waveguide. The diffraction waveguide includes a substrate, a grating structure layer sequentially stacked on the substrate, and a filling layer disposed on the grating structure layer. In the prior art, as an idealized filling layer structure, the surface of the filling layer away from the grating structure layer is assumed to be a plane of uniform thickness, with equal thickness in both the grating structure region and the non-structure region. Figure 1The upper surface of the filler layer is shown. However, analysis of the structural area where the filler layer is located revealed that there are actually "recesses" between adjacent grating grooves in the grating structure area, forming an uneven filler layer, such as... Figure 2 As shown.

[0044] further, Figure 3 for Figure 1 and Figure 2 Enlarged cross-sectional view of a local area, such as Figure 3 The upper figure shows an idealized filler layer structure in the prior art. The filler layer thickness in the non-structured region is H1, and the filler layer thickness in the grating structure region, from the top of the grating structure to the surface furthest from the grating structure, is H2. In the default filler process, the prior art assumes H1=H2, meaning the filler layer thickness is equal in different regions. However, the applicant discovered that during the actual filler layer filling process, characterization revealed that... Figure 2 As shown, the actual thickness of the filling layer differs significantly between the grating structure region and the unstructured region. Combined with... Figure 3 As shown in the lower middle figure ( Figure 3 The thickness variation in the lower part of the image is for illustrative purposes only. Figure 2 The enlarged view of a local area structure shows that the fill layer thickness in the non-structured region is H1, and the fill layer thickness in the grating structure region, from the top of the grating structure to the surface away from the grating structure, is H2. In actual filling processes, H2 is not equal to H1, and is usually represented by H2.

[0045] Figures 1-3 The thickness and thickness variation of the filling layer are for illustrative purposes only and do not represent the actual thickness of the filling layer or the thickness variation within the grating structure region. This application's appendix... Figures 1-3 This is intended to illustrate the situation where existing technologies exist.

[0046] Therefore, in order to solve the above-mentioned technical problems, the present invention proposes a method for adjusting the thickness consistency between the grating structure region and the unstructure region, including adjusting the filling layer height between adjacent grating structure grooves in the grating structure region of the diffractive waveguide, as well as the thickness consistency between the grating structure region and the unstructure region, thereby achieving thickness uniformity within the grating structure region and having the same or similar thickness as the unstructure region, improving the imaging effect of the diffractive waveguide, and preventing optical defects.

[0047] ​In detail, such as Figure 4 As shown, a method for adjusting the thickness consistency between the structured and unstructured regions of a grating includes the following steps:

[0048] S1: A substrate is provided, and a grating structure layer is formed on one side of the substrate. The grating structure layer includes a grating structure region and a non-structure region. The grating structure region includes a plurality of grating ridges and grating grooves.

[0049] S2: A first material layer is disposed on the surface of the grating structure region and the unstructure region, and the first material layer covers the entire surface of the grating structure layer;

[0050] S3: Pattern the first material layer, remove the first material layer located on the surface of the non-structured region, and retain the first material layer covering the grating structure region;

[0051] S4: A first anti-adhesion layer is provided on the surfaces of the grating structure region and the unstructure region; the surface energy of the unstructure region surface is improved based on the first anti-adhesion layer;

[0052] S5: Remove the first material layer and the first anti-adhesion layer covering the grating structure region, and retain the first anti-adhesion layer on the surface of the non-structure region;

[0053] S6: A first filling layer is provided in the grating structure region; the first filling layer fills the grating groove;

[0054] S7: Remove the first anti-adhesive layer covering the surface of the unstructured area to fully expose the surfaces of the unstructured area and the grating structure area;

[0055] S8: A second filling layer is provided on the exposed unstructured area and the grating structure area surface, so that the second filling layer covers the entire surface and performs surface planarization treatment.

[0056] S9: Solidify the second filling layer to obtain a diffractive waveguide.

[0057] In this application, through the coordination of multiple process steps, a first anti-adhesion layer with low surface energy characteristics is preferentially constructed on the surface of the unstructured region, thereby suppressing the accumulation of material in the subsequent first filling layer in the unstructured region. Secondly, the first filling layer is preferentially filled in the grating groove of the grating structure to form the first filling layer. Then, the first anti-adhesion layer located in the unstructured region is removed, and finally, a second filling layer is set on the surface of the entire waveguide. By employing a two-stage filling method, the material of the first filling layer is located within the grating groove, preventing depressions caused by differences in factors such as large-area material shrinkage, thermal expansion, adhesive viscosity, and grating gaps. The grating grooves between the grating structures are pre-filled by pre-curing the first filling layer. The second filling layer is only applied to the surface structure, including both the grating structure area and the non-structure area, covering the entire surface. This application adjusts the large-area filling of the prior art to a two-stage filling method (large-area filling refers to simultaneously filling the grating groove and its entire grating structure surface). The first filling of the grating groove is followed by pre-curing. Before the second filling, the first anti-stick layer is removed, and then the entire surface is filled a second time. This achieves cross-regional thickness consistency control through "surface energy regulation + selective filling + structural pre-embedding," avoiding the one-time large-area filling of the grating groove and non-structure areas in the prior art. Compared to the prior art, this "two-step filling +..." approach significantly improves the overall quality and efficiency. The "selective anti-adhesion layer" solves the problem of inconsistent thickness between the grating structure region and the unstructured region. It can significantly improve the unevenness of the plane after the filling layer is applied to the grating structure region, as well as the thickness deviation between the grating structure region and the unstructured region. It makes H2 and H1 as equal as possible, or reduces the absolute value of the difference between them |H2−H1| within a certain threshold range, thereby effectively suppressing optical display defects such as rainbow patterns, dispersion shift, and decreased diffraction efficiency caused by uneven thickness. Furthermore, through the process steps of this invention, the consistency of the filling layer thickness at different positions in the grating structure region can also be ensured as much as possible, making the filling layer thickness at different positions in the grating structure region as equal as possible, or controlling the filling layer thickness deviation at different positions in the grating structure region within a certain threshold, such as ±5 nm or ±3 nm, etc. The optimal performance is used as the control threshold, thereby improving the uniformity and stability of the overall optical performance of the diffractive waveguide. From a design perspective, this is easy to determine.

[0058] More in detail, and in combination Figure 4 In step S1 of this application, a substrate is provided, such as a glass substrate, resin substrate, SiC substrate, or other diffractive waveguide substrates commonly used in the art. A grating structure layer is formed on one side of the substrate. The grating structure layer includes a grating structure region and a non-structure region. The grating structure includes several grating ridges and grating grooves.

[0059] Furthermore, the grating structure region refers to the region that includes several grating structures; the unstructured region refers to the region other than the grating structure region.

[0060] In this step, the grating structure layer can be formed on the surface of the substrate using a nanoimprint lithography or etching process. In one embodiment, the nanoimprint lithography process uses a high-precision mold to imprint a nanoscale periodic pattern onto the photosensitive resin layer, which is then cured under ultraviolet light to form a stable grating structure. Alternatively, the etching process uses a patterned structure and a photoresist mask to anisotropically etch the substrate material to form the grating structure layer. Figure 4 The illustration includes forming the grating structure layer by nanoimprinting, forming the grating structure layer on the surface of the substrate by nanoimprinting, and the grating structure layer being located on the substrate;

[0061] As in another embodiment, and further combined Figure 6 It can be seen that the grating structure is formed through etching, combined with Figure 4 Other process steps ( Figure 6 Other process steps are omitted in the text, but the same steps in the above process can be referred to (both processes use the same process steps). Schematic, simply summarized as follows: after forming a grating structure layer in the substrate through etching, a first material layer is set in the grating groove and patterned to form a first anti-adhesion layer. The first material layer in the grating groove is removed, and a first filling layer is set. Subsequently, the first anti-adhesion layer is removed, and a second filling layer is applied, covering the entire surface. That is, through two filling processes and one anti-adhesion layer, the thickness modulation of the diffraction grating, including through etching, is achieved, thereby constructing a highly consistent surface morphology between the grating groove and the unstructured area.

[0062] Of course, the above embodiments provide a method of forming a diffraction grating using two different process methods: nanoimprint technology and etching technology. These are two commonly used methods in the field. Then, the first filling layer and the second filling layer are set using the same process method.

[0063] In this invention, the two-step filling strategy not only precisely controls the thickness of each region, but also uses the first anti-adhesive layer to locally block the first filling layer, thereby achieving selective filling and thickness control and ensuring that the height of each region on the top of the grating is consistent with the height of the unstructured region.

[0064] Of course, the thickness consistency referred to in this invention means that the thickness difference of the filling layer between different regions is as small as possible, such as the difference between the two is less than 5% or less than 3%; or, the thickness of the filling layer in different regions is as equal as possible or the difference meets a certain threshold range, such as within ±5 nm, etc.; or further, the thickness difference of the filling layer between different regions is as close as possible to 0, or the thickness difference is within a few nanometers, all of which are requirements of thickness consistency referred to in this application.

[0065] The steps described above are logically related, providing an unparalleled connection for achieving the objectives of this invention. Compared to existing technologies, the "two-step filling + selective anti-adhesion layer" method addresses the issue of inconsistent thickness between the grating structure region and the unstructured region. This significantly improves the unevenness of the plane after the filling layer is applied to the grating structure region and resolves the thickness deviation problem between the grating structure region and the unstructured region, thereby improving the optical display effect of the waveguide.

[0066] In step S1, the grating structure layer is formed using nanoimprinting or etching processes, both of which are conventional techniques in the field and will not be described in detail here; of course, Figure 4 and Figure 5 The grating structure and parameters shown are for illustrative purposes only and do not constitute a limitation on the grating structure and its parameters. For example, it also includes multi-dimensional grating contour designs such as helical teeth, blazed, and trapezoidal structures, as well as grating structures with varying or uniform depths. All of these are within the scope of the grating structure indicated in this application. The structure of the accompanying drawings does not constitute a limitation on the scope of protection of this application. The focus of this application is on the aforementioned process method.

[0067] Next, proceed to step S2: A first material layer is deposited on the surface of the grating structure region and the unstructured region, covering the entire surface of the grating structure layer. In this step, the first material layer can be photoresist or other masking adhesive layers, etc., for the purpose of subsequent patterning processing. The first material layer covers the entire surface of the substrate, forming a continuous first material layer on both the surface of the grating structure region and the unstructured region.

[0068] Furthermore, in step S3, the first material layer is patterned to remove the first material layer located on the surface of the unstructured area, while retaining the first material layer covering the grating structure area. In this step, in order to prevent the influence in subsequent steps, the first material layer is preferentially set and patterned windowing is performed so that the grating structure area is selectively covered by the first material layer, while the unstructured area is completely exposed.

[0069] exist Figure 4 The diagram shows three grating structure regions, namely, an input grating structure region, a transition grating structure region, and an output grating structure region. Figure 4 The number of grating structure regions shown is not limited and can be set according to the requirements of those skilled in the art, or may include four, five, etc., but at least two grating structure regions as coupling-in and coupling-out grating structure regions.

[0070] In step S4, a first anti-adhesion layer is formed on the surfaces of the grating structure region and the unstructure region. The surface energy of the unstructure region is improved based on the first anti-adhesion layer. It is understood that the introduction of the first anti-adhesion layer is not a simple covering, but rather a microscopic selective adsorption barrier is constructed between the grating structure region and the unstructure region by regulating the surface energy of the unstructure region. This results in the unstructure region exhibiting low surface energy characteristics, while the grating structure region, being covered by the first material layer, maintains a relatively high surface energy. This guides the material to preferentially adsorb onto the grating structure region during the subsequent filling layer deposition process, suppressing unintended film formation in the unstructure region and ensuring that the filling layer accurately fills only the target area.

[0071] The first anti-stick layer can be made of low surface energy materials such as fluorosilanes, perfluoropolyethers, or self-assembled monolayers, and can be achieved through vapor deposition or spin coating processes.

[0072] In step S5, the first material layer and the first anti-adhesion layer covering the grating structure region are removed, while the first anti-adhesion layer on the surface of the non-structure region is retained. The first anti-adhesion layer located within the grating structure region can be removed using removal processes commonly used in the art. Care should be taken in this step to avoid damaging the low surface energy characteristics already formed in the non-structure region.

[0073] In step S6, a first filling layer is provided in the grating structure region; the first filling layer fills the grating groove, and the first filling layer is planarized; in this step, the refractive index of the first filling layer is less than the refractive index of the substrate.

[0074] Furthermore, in this step, in one embodiment, the first filling layer is set such that the height of the first filling layer after curing in the grating groove is not greater than the height of the grating structure.

[0075] Alternatively, in another embodiment, the height of the first filling layer after curing in the grating groove is less than the height of the grating structure.

[0076] Alternatively, in another embodiment, the height of the first filling layer after curing in the grating groove is equal to the height of the grating structure.

[0077] Step S6 also includes curing the first filling layer to solidify the first filling layer material in the grating groove; the height of the first filling layer after curing is not greater than the height of the grating structure, and the next step is carried out after curing.

[0078] Step S6 further includes planarizing the first filler layer before curing. Planarization includes methods commonly used in the art, such as high-speed rotation. This is not the focus of this invention; only the use of commonly used spin coating techniques is required.

[0079] To better achieve the technical effect of the present invention, in step S6, the height of the first filling layer before curing is greater than the height of the grating structure, and when the first filling layer is in a liquid state before curing, the height difference between the first filling layer and the top of the grating structure is... , Limited to:

[0080] ;

[0081] in, The height difference between the first filling layer and the top of the grating structure before the first filling layer is cured; The height of the grating structure; The curing shrinkage rate of the first filler layer is denoted as .

[0082] and The height of the grating structure can be determined during design or by characterizing the grating structure. The curing shrinkage rate refers to the volume shrinkage rate of the material after it changes from a liquid to a solid state, and is determined by the material properties.

[0083] In the actual filling process, it should be ensured that... The goal is to meet the height requirement of the first filling layer filling the grating groove, while minimizing the amount of material remaining in the first filling layer at the top of the grating structure. It should not be too large, so as to reduce the impact on the filling of the second filling layer.

[0084] Furthermore, based on the above embodiments, in step S6, the volume of the first filling layer is set. ,in: ;

[0085] in, This represents the volume of the first filling layer; Indicates the duty cycle of the grating; The curing shrinkage rate of the first filler layer; The height of the grating structure is given.

[0086] This represents the duty cycle of the grating. In one case, the average value of the grating duty cycle can be chosen as the calculation value.

[0087] In this step, to ensure that the height of the first filling layer after curing in the grating groove is not greater than the height of the grating structure, it is necessary to ensure that the first filling layer is located at the top of the grating structure when it is set, and that the height of the first filling layer has a certain height difference relative to the height of the grating structure. .like Figure 5 The image shown is an enlarged view of a local area of ​​step S6, illustrating that the first filling layer is located above the grating structure and has a height difference relative to the top of the grating structure. The curing properties of the material are considered to ensure that the height after curing meets the design requirements of this invention.

[0088] In step S7, the first anti-adhesive layer covering the surface of the unstructured region is removed to fully expose the surfaces of the unstructured region and the grating structure region. At this time, the unstructured region returns to its original surface state, while the grating structure region has been fully embedded and planarized by the first filler layer, laying the foundation for the uniform spreading of the subsequent second filler layer. At this time, the substrate surface exhibits clear regional functional differentiation: the grating structure region is firmly supported by the first filler layer, while the unstructured region is exposed as a clean substrate surface, providing an ideal interface for the precise deposition of the second filler layer.

[0089] In step S8, a second filling layer is provided on the exposed unstructured area and the grating structure area surface, so that the second filling layer covers the entire surface and performs surface planarization treatment.

[0090] In detail, a second filling layer is formed on the surface of the unstructured region and the grating structure region using common techniques in the art, and the surface of the second filling layer is planarized. The refractive index of the second filling layer is not equal to the refractive index of the substrate, but is equal to the refractive index of the first filling layer; or in some other embodiments, the refractive index of the second filling layer is greater than that of the first filling layer. When the refractive index of the second filling layer is greater than that of the first filling layer, it provides those skilled in the art with more options for refractive index, avoiding the use of only one material with the same refractive index in the grating groove and unstructured region in the prior art, and has a better degree of freedom of choice. This refractive index matching design can effectively control the phase delay and reflection characteristics of light at the multilayer interface, so that the incident light, after being modulated by the grating structure and the filling layer, meets the momentum matching condition of the target diffraction order. At the same time, the uniform coverage and precise planarization of the second filling layer ensure the nanoscale morphological integrity of the overall optical surface, which is essential for achieving high diffraction efficiency and low stray light.

[0091] Furthermore, in step S8, the height of the spin-coated second filler layer... It meets the following conditions:

[0092]

[0093] in, Indicates the height of the second filler layer spin-coated; This indicates the curing shrinkage rate of the second filler layer; This indicates the height difference between the unstructured region and the top of the grating structure.

[0094] Step S9 includes solidifying the second filling layer to obtain a diffractive optical waveguide. (Combined) Figure 4 As shown in S8-S9, after the second filling layer is applied to the surfaces of the non-structured region and the grating structured region, during the curing process in step S9, the second filling layer in the non-structured region contains more material, resulting in more solvent in that region. Heating and curing causes significant volume shrinkage and solvent evaporation in that region. Conversely, the second filling layer in the grating structured region contains less material, resulting in less solvent evaporation and less shrinkage of the second filling layer material in the grating structured region. Thus, based on step S8, the graphic structure shown in S9 is formed. The difference in shrinkage between the two locations makes the thicknesses of the different regions as equal or similar as possible.

[0095] In steps S6 and S9 of the present invention, when the first filling layer is cured, the first filling layer fills the grating groove and forms a support structure with a certain strength after curing. Its curing shrinkage is completed under the structural constraints of the existing grating groove. In step S9, the curing of the second filling layer is carried out on the entire surface. It is a separate process from the curing of the first filling layer. The second curing process, rather than the curing process that directly acts on the bottom of the grating groove, can reduce the influence of the second filling layer on the first filling layer during the curing deformation process, thereby reducing the uneven structure generated in the grating groove.

[0096] In this invention, as shown in the figure in S9, the first filling of the grating groove and the pre-curing can prevent uneven changes in the filling layer in the grating groove between different grating structures. It can significantly improve the unevenness of the plane after the filling layer is set on the grating structure area, as well as the thickness deviation between the grating structure area and the non-structure area, so that H2 and H1 are as equal as possible, and reduce the impact of existing processes on the structure.

[0097] Based on the above embodiments, further, in step S6, the ratio of the height of the first filling layer after curing to the height of the grating structure is controlled between 0.85 and 1.

[0098] Based on the above embodiments, in other alternative embodiments, to better achieve the technical effects of the present invention, the viscosity of the first filler layer is limited to be greater than that of the second filler layer; the curing shrinkage rate of the first filler layer is less than that of the second filler layer; by limiting the relative relationship between the second filler layer and the first filler layer, the height of the second filler layer at different positions is made as equal as possible or the difference is small as possible due to its high shrinkage and low viscosity properties, thereby reducing the impact of the material during the curing process. This can be achieved by controlling different curing temperatures during the curing process.

[0099] Furthermore, the height of the first filling layer is greater than or equal to the height of the second filling layer. For example, during the experiment, while adhering to the aforementioned formula for calculating the height difference between the first filling layer and the grating structure, the applicant can schematically set the height of the first filling layer to 50nm and the height of the second filling layer to 30nm; or set the height of the first filling layer to 40nm and the height of the second filling layer to 40nm; etc. All of these methods can yield optical structures with good thickness consistency. Test results show that this improves the display effect of the diffractive waveguide and reduces optical defects in optical displays, such as rainbow patterns and ghosting.

[0100] Furthermore, the height of the first filling layer in its liquid state is greater than the height of the grating structure, and after pre-curing, the upper surface of the first filling layer is coplanar with the upper surface of the grating ridge, so as to facilitate the setting of the second filling layer.

[0101] Based on the above embodiments, the present invention provides a diffractive optical waveguide, which is fabricated based on any of the foregoing embodiments. Based on the technical effects of the foregoing embodiments, this diffractive optical waveguide has corresponding technical effects.

[0102] Of course, the present invention also provides an augmented reality display device comprising the diffractive waveguide as described above.

[0103] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for adjusting the thickness consistency between the structured and unstructured regions of a grating, characterized in that, Includes the following steps: S1: A substrate is provided, and a grating structure layer is formed on one side of the substrate. The grating structure layer includes a grating structure region and a non-structure region. The grating structure region includes a plurality of grating ridges and grating grooves. S2: A first material layer is disposed on the surface of the grating structure region and the unstructure region, and the first material layer covers the entire surface of the grating structure layer; S3: Pattern the first material layer, remove the first material layer located on the surface of the non-structured region, and retain the first material layer covering the grating structure region; S4: A first anti-sticking layer is provided on the surfaces of the grating structure region and the non-structure region; The surface energy of the unstructured region is improved by the first anti-adhesion layer; S5: Remove the first material layer and the first anti-adhesion layer covering the grating structure region, and retain the first anti-adhesion layer on the surface of the non-structure region; S6: A first filling layer is provided in the grating structure region; the first filling layer fills the grating groove; S7: Remove the first anti-adhesive layer covering the surface of the unstructured area to fully expose the surfaces of the unstructured area and the grating structure area; S8: A second filling layer is provided on the exposed unstructured area and the grating structure area surface, so that the second filling layer covers the entire surface and performs surface planarization treatment. S9: Solidify the second filling layer to obtain a diffractive waveguide.

2. The method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 1, characterized in that, In step S1, the grating structure layer is formed by nanoimprinting or etching.

3. A method for adjusting the thickness consistency between the structured and unstructured regions of a grating according to any one of claims 1 to 2, characterized in that, The refractive index of the first filling layer is less than that of the substrate, and the refractive index of the second filling layer is equal to that of the first filling layer.

4. A method for adjusting the thickness consistency between the structured and unstructured regions of a grating according to any one of claims 1 to 2, characterized in that, The refractive index of the second filling layer is greater than that of the first filling layer.

5. A method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 1 or 2, characterized in that, In step S6, the first filling layer is cured, and the next step is performed after curing; and the height of the first filling layer after curing in the grating groove is not greater than the height of the grating structure.

6. The method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 5, characterized in that, The viscosity of the first filler layer is greater than that of the second filler layer; the curing shrinkage rate of the first filler layer is less than that of the second filler layer.

7. The method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 5, characterized in that, The height of the first filler layer is greater than or equal to the height of the second filler layer; Furthermore, in step S8, the height of the spin-coated second filler layer... It meets the following conditions: in, Indicates the height of the second filler layer spin-coated; This indicates the curing shrinkage rate of the second filler layer; This indicates the height difference between the unstructured region and the top of the grating structure.

8. The method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 5, characterized in that, In step S6, when the height of the first filling layer before curing is greater than the height of the grating structure, and when the first filling layer is in a liquid state before curing, the height difference between the first filling layer and the top of the grating structure is... , Limited to: ； in, The height difference between the first filling layer and the top of the grating structure before the first filling layer is cured; The height of the grating structure; The curing shrinkage rate of the first filler layer is denoted as .

9. The method for adjusting the thickness consistency between the grating structure region and the unstructure region according to claim 8, characterized in that, In step S6, the volume of the first filling layer is set. ,in, ； in, This represents the volume of the first filling layer; Indicates the duty cycle of the grating; The curing shrinkage rate of the first filler layer; The height of the grating structure is given.

10. A diffractive optical waveguide, characterized in that, It was prepared based on the method for adjusting the thickness consistency between the structural and unstructured regions of the grating as described in any one of claims 1 to 9.

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