Polarizer holographic grating, preparation method of polarizer holographic grating and exposure system

Abstract

The invention provides a polarization body holographic grating, a preparation method of the polarization body holographic grating and an exposure system. The polarization body holographic grating comprises a substrate layer, a two-dimensional orientation layer and a liquid crystal layer, the two-dimensional orientation layer is arranged on the surface of the substrate layer, and the orientation direction of the two-dimensional orientation layer periodically changes in a first preset direction and periodically changes in a second preset direction perpendicular to the first preset direction, so that the two-dimensional orientation layer forms a first equiphase line and a second equiphase line with an included angle larger than zero; the liquid crystal layer is arranged on the surface, away from the substrate layer, of the two-dimensional orientation layer, and the arrangement direction of liquid crystal molecules in the liquid crystal layer corresponds to the orientation direction of the two-dimensional orientation layer, so that the liquid crystal layer forms a first equiphase face corresponding to the first equiphase line and forms a second equiphase face corresponding to the second equiphase line. The liquid crystal layer is oriented through the two-dimensional orientation layer, so that the polarization body holographic grating has the diffraction characteristic of a two-dimensional grating, and preparation of the single-layer two-dimensional polarization body holographic grating is achieved.

Description

Technical Field

[0001] The present application relates to the field of gratings, and in particular to a polarization volume holographic grating, a method for preparing the polarization volume holographic grating, and an exposure system. Background Art

[0002] A polarization holographic grating is a polarization-selective holographic optical element. In a near-eye display scenario, the polarization holographic grating is arranged in an optical waveguide so that the signal light can be coupled into the optical waveguide through the polarization holographic grating, and after being transmitted in the optical waveguide, it is coupled out through another polarization holographic grating, thereby realizing the transmission of the signal light. However, the polarization holographic grating in the related art is limited by the preparation method, and the prepared polarization holographic grating only has an equiphase plane in one direction, that is, the prepared polarization holographic grating is a one-dimensional polarization holographic grating. Therefore, in the related art, if a two-dimensional polarization holographic grating is required, multiple one-dimensional polarization holographic gratings must be stacked to realize the diffraction effect of the two-dimensional polarization holographic grating. It can be seen that there are problems such as cumbersome preparation process and low yield of the two-dimensional polarization holographic grating in the related art, and there is no method for directly preparing the two-dimensional polarization holographic grating in the related art. Summary of the invention

[0003] The present application provides a polarization volume holographic grating, a method for preparing a polarization volume holographic grating, and an exposure system, aiming to provide a polarization volume holographic grating with at least two grating period directions, thereby realizing the preparation of a single-layer two-dimensional polarization volume holographic grating.

[0004] In a first aspect, the present application provides a polarization volume holographic grating, wherein the polarization volume holographic grating comprises:

[0005] basal layer;

[0006] A two-dimensional alignment layer, wherein the two-dimensional alignment layer is arranged on the surface of the base layer, and the alignment direction of the two-dimensional alignment layer changes periodically in a first preset direction and in a second preset direction perpendicular to the first preset direction, so that the two-dimensional alignment layer forms a first equiphase line and a second equiphase line, and the angle between the first equiphase line and the second equiphase line is greater than zero;

[0007] A liquid crystal layer, wherein the liquid crystal layer is arranged on a surface of the two-dimensional orientation layer away from the substrate layer, and the arrangement direction of the liquid crystal molecules in the liquid crystal layer corresponds to the orientation direction of the two-dimensional orientation layer, so that the liquid crystal layer forms a first isophase plane corresponding to the first isophase line and forms a second isophase plane corresponding to the second isophase line.

[0008] In a second aspect, the present application further provides a method for preparing a polarization volume holographic grating, the method for preparing the polarization volume holographic grating comprising:

[0009] Providing a base layer, and coating an alignment layer to be exposed on a surface of the base layer;

[0010] Providing a mask, and making the mask cover a portion of the alignment layer to be exposed that is away from the surface of the base layer;

[0011] irradiating the alignment layer to be exposed with an exposure light beam to expose the to-be-exposed area on the surface of the alignment layer to be exposed that is not blocked by the mask to obtain a two-dimensional alignment layer;

[0012] Wherein, during the process of the exposure light beam irradiating the alignment layer to be exposed, the mask is translated along a first preset direction and the alignment layer to be exposed reciprocates in a second preset direction, or the alignment layer to be exposed is translated along a direction opposite to the first preset direction and reciprocates in the second preset direction, so that the alignment direction of the two-dimensional alignment layer presents periodic changes in both the first preset direction and the second preset direction, so that the two-dimensional alignment layer forms a first equiphase line and a second equiphase line;

[0013] The mask is removed, and liquid crystal is coated on the surface of the two-dimensional alignment layer facing away from the substrate layer to obtain the polarizer holographic grating.

[0014] In a third aspect, the present application further provides an exposure system, the exposure system at least comprising:

[0015] An exposure light source, the exposure light source is used to provide an exposure light beam to irradiate the alignment layer to be exposed;

[0016] A clamping mechanism, wherein the clamping mechanism is used to clamp the mask and translate along a first preset direction during the process in which the exposure light source exposes the alignment layer to be exposed, and the mask is used to cover a portion of the surface of the alignment layer to be exposed;

[0017] The loading platform is used to carry the base layer and the alignment layer to be exposed on the base layer, and to carry the alignment layer to be exposed to reciprocate in a second preset direction during the exposure light source exposing the alignment layer to be exposed.

[0018] The present application provides a polarization volume holographic grating, a method for preparing a polarization volume holographic grating, and an exposure system. The liquid crystal layer in the polarization volume holographic grating of the present application forms equiphase planes in two different directions, so that the polarization volume holographic grating has a Bragg diffraction effect in the two different directions, thereby making the polarization volume grating have the diffraction characteristics of a two-dimensional grating. Furthermore, in a scene where a two-dimensional grating needs to be set up, only the polarization volume holographic grating needs to be set up to meet the use requirements of the two-dimensional grating, and there is no need to stack two one-dimensional gratings to simulate the effect of a two-dimensional grating, thereby realizing the preparation of a single-layer two-dimensional polarization volume holographic grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a schematic diagram of the orientation direction distribution of the orientation layer of the polarization volume holographic grating in the related art;

[0021] Figure 2 It is a partial schematic diagram of a polarization volume holographic grating in the related art;

[0022] Figure 3 It is a schematic diagram of the structure of a polarization volume holographic grating in the related art;

[0023] Figure 4 A schematic structural diagram of a polarization volume holographic grating provided in one embodiment of the present application;

[0024] Figure 5 A schematic diagram of a projection of a two-dimensional alignment layer along a substrate layer provided in an embodiment of the present application;

[0025] Figure 6 A flow chart of a method for preparing a polarization volume holographic grating provided in one embodiment of the present application;

[0026] Figure 7 A schematic diagram of an exposure process of an alignment layer to be exposed provided in one embodiment of the present application;

[0027] Figure 8 A schematic block diagram of the structure of an exposure system provided in one embodiment of the present application.

[0028] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0031] See also Figure 1 , Figure 2 and Figure 3 , Figure 1 is a schematic diagram of the orientation direction distribution of the orientation layer of the polarization volume holographic grating in the related art, Figure 2 is a partial schematic diagram of a polarization volume holographic grating in the related art, Figure 3 It is a schematic diagram of the structure of a polarization volume holographic grating in the related technology.

[0032] A polarization volume holographic grating is a polarization-selective holographic optical element, which records the polarization information of two interfering light beams, including right-circularly polarized (RCP) and left-circularly polarized (LCP). Specifically, in the related art, a polarization volume holographic grating is exposed to an orientation layer 121 on the polarization grating by two circularly polarized lights with opposite polarization states at the same time, so that the material molecules in the orientation layer 121 are arranged in order according to the polarization direction of the light field after the two polarized lights are superimposed at the position, so that the orientation direction of the orientation layer 121 is as follows: Figure 1 As shown, it can be seen that, limited by the preparation method, Figure 1 The orientation direction of the orientation layer 121 shown in FIG. 1 changes periodically in the X-axis direction, but does not change in the Y-axis direction. As a result, after the liquid crystal is coated on the orientation layer 121, the liquid crystal molecules are deflected under the orientation of the orientation layer 121. The deflection state is as shown in FIG. Figure 2 As shown, it should be understood that the liquid crystal molecules close to the alignment layer 121 will be arranged strictly according to the alignment direction of the alignment layer 121, but in the direction away from the alignment layer 121, the control force of the alignment layer 121 on the liquid crystal molecules is weakened, and the liquid crystal molecules will rotate, thereby forming periodicity in the Z-axis direction; the prepared polarization holographic grating is as follows Figure 3As shown, from the equiphase planes of the liquid crystal layer 13 in the polarizer holographic grating, it can be seen that the polarizer holographic grating has no periodicity in the direction parallel to the equiphase planes, and thus the polarizer holographic grating has only one grating period direction, that is, a one-dimensional polarizer holographic grating. Therefore, if the diffraction effect of a two-dimensional polarizer holographic grating is to be realized, two one-dimensional polarizer holographic gratings need to be stacked to simulate the diffraction effect of a two-dimensional grating, which results in problems such as complex preparation process, high cost and low finished product yield.

[0033] The orientation direction of the polarization holographic grating orientation layer 121 provided in the present application varies periodically in two different directions, so that the liquid crystal layer 13 in the polarization holographic grating forms equal phase planes in two different directions, thereby making the polarization holographic grating have the diffraction characteristics of a two-dimensional grating, realizing the preparation of a single-layer two-dimensional polarization holographic grating, solving the problem of needing to stack two one-dimensional polarization holographic gratings when realizing the diffraction effect of a two-dimensional grating through a polarization holographic grating, and thus solving the problems of complex process, high cost and low yield of finished products in the preparation of two-dimensional polarization holographic gratings.

[0034] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0035] Please refer to Figure 4 , Figure 4 A schematic structural diagram of a polarization volume holographic grating provided in one embodiment of the present application.

[0036] like Figure 4As shown, the polarization holographic grating includes a substrate layer 11, a two-dimensional orientation layer 122 and a liquid crystal layer 13. The two-dimensional orientation layer 122 is arranged on the surface of the substrate layer 11, and the orientation direction of the two-dimensional orientation layer 122 changes periodically in a first preset direction, and the orientation direction of the two-dimensional orientation layer 122 also changes periodically in a second preset direction, so that the two-dimensional orientation layer 122 forms a first equiphase line and a second equiphase line, and the angle between the first equiphase line and the second equiphase line is greater than zero; the liquid crystal layer 13 is arranged on the surface of the two-dimensional orientation layer 122 away from the substrate layer 11. In the preparation process of the polarization holographic grating, the liquid crystal molecules in the liquid crystal layer 13 are deflected under the orientation of the two-dimensional orientation layer 122, so that the arrangement direction of the liquid crystal molecules corresponds to the orientation direction of the two-dimensional orientation layer 122. In the specific implementation process, the arrangement direction of the liquid crystal molecules close to the two-dimensional orientation layer 122 is the same as that of the liquid crystal molecules in the two-dimensional orientation layer 122. The orientation direction is exactly the same, and along the direction away from the contact plane between the two-dimensional orientation layer 122 and the liquid crystal layer 13, the force exerted by the two-dimensional orientation layer 122 on the liquid crystal molecules gradually weakens. In this direction, due to the physical properties of the liquid crystal molecules themselves, the liquid crystal molecules will continue to rotate, thereby forming a periodicity in this direction, so that the finally formed equiphase plane is not perpendicular to the plane where the orientation layer 121 is located, and because the thickness of the liquid crystal layer 13 is greater than the thickness of the two-dimensional orientation layer 122, a first equiphase plane corresponding to the first equiphase line and a second equiphase plane corresponding to the second equiphase line can be formed in the liquid crystal layer 13 of the polarization body holographic grating. It should be understood that the angle between the first equiphase plane and the second equiphase plane is determined by the angle between the first equiphase line and the second equiphase line and the pitch of the liquid crystal molecules in the Z direction.

[0037] It should be noted that in the space of the liquid crystal layer 13, there are two first equiphase planes and second equiphase planes in different directions, so that the polarization holographic grating has Bragg diffraction effect in two different directions. Therefore, the liquid crystal layer 13 has two polarization holographic gratings in different directions, which can achieve the same diffraction effect as the two-dimensional grating. It should be understood that the equiphase plane refers to the plane formed in space by all liquid crystal molecules with exactly the same rotation angle or molecular orientation.

[0038] See also Figure 5 , Figure 5 It is a schematic diagram of the projection of the two-dimensional alignment layer 122 along the direction of the base layer 11 provided in one embodiment of the present application.

[0039] In some embodiments, in the projection of the two-dimensional alignment layer 122 along the direction of the base layer 11 , the connecting lines between the position points in the same alignment direction are in a sawtooth shape.

[0040] Exemplarily, the projection of the two-dimensional alignment layer 122 along the direction of the base layer 11 is: Figure 5The double-headed arrow in the figure indicates the polarization direction of the exposure light field or the orientation direction of the position. The connecting line between the position points with the same orientation direction is in a sawtooth shape. It should be understood that the connecting line between the position points with the same orientation direction is an equiphase line, that is, there are at least two equiphase lines with different directions, so that the connecting line between the position points with the same orientation direction is in a sawtooth shape.

[0041] In some embodiments, the first preset direction is the X-axis direction of a preset coordinate system, the second preset direction is the Y-axis direction of the preset coordinate system, and the origin of the preset coordinate system is any point on the plane where the base layer 11 is located.

[0042] Exemplarily, the origin of the preset coordinate system is at any point on the plane where the base layer 11 is located, so the XY plane of the preset coordinate system is the plane where the base layer 11 is located. Specifically, in the projection of the two-dimensional orientation layer 122 on the XY plane, the orientation direction of the two-dimensional orientation layer 122 shows periodic changes along the X-axis direction and the Y-axis direction, so that the two-dimensional orientation layer 122 can form a first equal phase line and a second equal phase line, and then the liquid crystal layer 13 on the surface of the two-dimensional orientation layer 122 can form a first equal phase plane corresponding to the first equal phase line and a second equal phase plane corresponding to the second equal phase line, so that the polarization holographic grating has the diffraction characteristics of a two-dimensional grating.

[0043] In a specific implementation process, the base layer 11 may be rectangular or circular, and the shape of the base layer is not limited herein.

[0044] In some embodiments, the base layer 11 includes resin or glass; the two-dimensional alignment layer 122 includes one of polyimide, organic azo compound and acrylate polymer; and the liquid crystal layer 13 includes cholesteric liquid crystal.

[0045] In the specific implementation process, the base layer 11 can be prepared by resin or glass, and the two-dimensional orientation layer 122 can be prepared by one of polyimide, organic azo compound and acrylate polymer, which is not limited in this application. The liquid crystal coated on the two-dimensional orientation layer 122 is a cholesteric liquid crystal, and the cholesteric liquid crystal molecules close to the two-dimensional orientation layer 122 will be arranged strictly in accordance with the orientation direction of the two-dimensional orientation layer 122, and along the direction away from the contact plane between the two-dimensional orientation layer 122 and the liquid crystal layer 13, due to the basic properties of the cholesteric liquid crystal molecules themselves, they will continue to rotate, thereby forming periodicity in this direction, resulting in the first equiphase plane and the second equiphase plane formed in the liquid crystal layer 13 are not perpendicular to the plane where the two-dimensional orientation layer 122 is located; wherein, the cholesteric liquid crystal is, for example, a chiral liquid crystal or a non-chiral liquid crystal with a chiral compound added, which is not limited in this application.

[0046] The polarization volume holographic grating provided in the above embodiment has the diffraction characteristics of a two-dimensional grating, thereby avoiding the need to simulate the diffraction effect of a two-dimensional grating by stacking two one-dimensional polarization volume holographic gratings in a scenario where a two-dimensional grating is required, thereby realizing the preparation of a single-layer two-dimensional polarization volume holographic grating.

[0047] See also Figure 6 , Figure 6 A flow chart of a method for preparing a polarization volume holographic grating provided in one embodiment of the present application.

[0048] The present application also provides a method for preparing a polarization volume holographic grating, so as to prepare the polarization volume holographic grating described in the above embodiments.

[0049] It should be understood that in the related art, due to the preparation method as described above, the polarization volume holographic grating obtained is a one-dimensional grating, which limits the use scenarios of the polarization volume holographic grating. The preparation method of the polarization volume holographic grating provided in the present application can directly prepare a polarization volume holographic grating with the diffraction characteristics of a two-dimensional grating.

[0050] like Figure 6 As shown, the method for preparing a polarization volume holographic grating includes steps S101 to S104.

[0051] Step S101 : providing a base layer, and coating an alignment layer to be exposed on the surface of the base layer.

[0052] Exemplarily, a base layer is provided, and the orientation layer to be exposed is coated on the surface of the base layer to expose the orientation layer to be exposed. The base layer provided can be prepared from resin or glass, and the present application does not limit the preparation material and preparation method of the base layer.

[0053] Step S102 , providing a mask, and making the mask cover a portion of the alignment layer to be exposed that is away from the surface of the base layer.

[0054] Illustratively, the mask is opaque, so during the exposure process, the surface area of ​​the orientation layer to be exposed that is blocked by the mask can be prevented from being exposed, so that the area to be exposed on the orientation layer to be exposed can be adjusted by controlling the area blocked by the mask.

[0055] In some embodiments, the mask is a light-impermeable plate, or a light-transmitting structure is provided on the mask, and the light-transmitting structure includes a slit or a through hole.

[0056] In the specific implementation process, the mask is a whole opaque flat plate, and the edge of the mask can be used to shield the orientation layer to be exposed. Specifically, the exposure beam irradiates the edge of the mask so that part of the exposure beam can irradiate the orientation layer to be exposed, while the remaining part of the exposure beam is blocked by the mask, thereby achieving the effect of using the edge of the mask to expose the orientation layer to be exposed; and if the mask is provided with a light-transmitting structure, the light-transmitting structure can be used to expose the orientation layer to be exposed. Specifically, the exposure beam is irradiated on the mask, and part of the exposure beam is irradiated to the orientation layer to be exposed through the light-transmitting structure on the mask, thereby realizing exposure of the orientation layer to be exposed, wherein the light-transmitting structure includes but is not limited to a slit or a through hole, and the present application does not limit the specific light-transmitting structure.

[0057] Step S103, using an exposure beam to irradiate the orientation layer to be exposed to expose the to-be-exposed area on the surface of the orientation layer to be exposed that is not blocked by the mask, so as to obtain a two-dimensional orientation layer; wherein, in the process of the exposure beam irradiating the orientation layer to be exposed, the mask is translated along a first preset direction and the orientation layer to be exposed reciprocates in a second preset direction, or the orientation layer to be exposed is translated in the opposite direction of the first preset direction and reciprocates in the second preset direction, so that the orientation direction of the two-dimensional orientation layer shows periodic changes in both the first preset direction and the second preset direction, so that the two-dimensional orientation layer forms a first equiphase line and a second equiphase line.

[0058] Exemplarily, the exposure beam and the mask are used to expose the orientation layer to be exposed to prepare a two-dimensional orientation layer. Specifically, the mask is moved to adjust the area blocked by the mask, and the exposure beam is used to complete the exposure of the orientation layer to be exposed.

[0059] See also Figure 7 , Figure 7 A schematic diagram of the exposure process of an alignment layer to be exposed provided in one embodiment of the present application.

[0060] For the convenience of description, the following embodiments are described by taking the mask as a light-proof flat plate as an example.

[0061] like Figure 7 As shown in the figure, before the exposure starts, the mask completely blocks the exposure area of ​​the alignment layer to be exposed, so that the exposure beam cannot irradiate the alignment layer to be exposed; after the exposure starts, the mask is translated along the first preset direction, that is, the X-axis direction shown in the figure at a speed of V2, so that the exposure area of ​​the alignment layer to be exposed is gradually exposed to the exposure spot corresponding to the exposure beam. At the same time, the alignment layer to be exposed is translated along the second preset direction, that is, the Y-axis direction shown in the figure at a speed of V1. This exposure process is shown in FIG. Figure 7As shown in ac in FIG, as the orientation layer to be exposed and the mask are translated, a set of oblique first equal phase lines will be formed on the surface of the orientation layer to be exposed, wherein the direction of the first equal phase lines is related to V1 and V2. Figure 7 As shown in the exposure process of df, it can be seen that at this time, the orientation layer to be exposed is translated along the -Y axis direction at a speed of V1', and the mask continues to be translated along the X axis direction. Similarly, with the translation of the exposure orientation layer and the mask, another set of second equal phase lines with different directions will be formed on the surface of the orientation layer to be exposed, and after a certain distance of displacement, the orientation layer to be exposed is translated again along the Y axis direction, and the above process is repeated until the exposure of the orientation layer to be exposed is completed. It should be understood that the orientation layer to be exposed reciprocates in the Y axis direction, and the mask is translated along the X axis direction from beginning to end, so that the first equal phase lines and the second equal phase lines with different directions can be exposed on the orientation layer to be exposed, and a two-dimensional orientation layer is obtained; it should be understood that the arrangement of the orientation directions in the two-dimensional orientation layer can refer to Figure 5 The corresponding embodiments thereof will not be described again herein.

[0062] In some embodiments, the mask translates along a first preset direction on the surface of the orientation layer to be exposed, including: the relative displacement between the mask and the orientation layer to be exposed in the second preset direction is zero, and the mask translates along the first preset direction at a uniform speed or at a variable speed.

[0063] It should be understood that during the movement of the mask and the orientation layer to be exposed, the two do not undergo relative displacement in the Y-axis direction, so that oblique equal phase lines can be exposed on the orientation layer to be exposed; and the mask is translated at a uniform speed or at a variable speed in the X-axis direction, which is not limited in this application. It should be noted that the orientation layer to be exposed is translated at a uniform speed in one direction, but the corresponding movement speeds of the orientation layer to be exposed in two directions can be different, which can be set according to actual design requirements, and is not limited in this application.

[0064] In other embodiments, the positions of the exposure light source and the mask are fixed, and the mask blocks part of the exposure beam so that the remaining exposure beam can expose the alignment layer that is not blocked by the mask. In the specific implementation process, the alignment layer moves at a uniform speed in the direction opposite to the first preset direction, and at the same time reciprocates in the second preset direction. Therefore, in the process from the alignment layer being blocked by the mask to being exposed, the alignment layer newly moved out from under the mask can be exposed by the same exposure spot, avoiding uneven exposure of the alignment layer due to uneven exposure spots, ensuring exposure consistency and orientation stability in the entire alignment layer; and there is no need to move the mask during the exposure process, making the entire exposure system more stable and with smaller exposure errors.

[0065] Step S104 , removing the mask, and coating liquid crystal on the surface of the two-dimensional alignment layer away from the substrate layer to obtain the polarization volume holographic grating.

[0066] Exemplarily, after exposure, the mask is removed, and liquid crystal is coated on the surface of the two-dimensional orientation layer facing away from the substrate layer, so that the liquid crystal is deflected under the orientation of the two-dimensional orientation layer to form a liquid crystal layer, thereby completing the preparation of a single-layer two-dimensional polarizer holographic grating.

[0067] In some embodiments, coating liquid crystal on the surface of the two-dimensional orientation layer away from the base layer to obtain the polarization holographic grating includes: after coating the liquid crystal on the surface of the two-dimensional orientation layer away from the base layer, orienting and curing the liquid crystal to form a liquid crystal layer to obtain the polarization holographic grating; wherein the arrangement direction of the liquid crystal in the liquid crystal layer corresponds to the orientation direction of the two-dimensional orientation layer, so that the liquid crystal layer forms a first equiphase plane corresponding to the first equiphase line and forms a second equiphase plane corresponding to the second equiphase line.

[0068] Exemplarily, after coating liquid crystal on the surface of the two-dimensional orientation layer facing away from the substrate layer, the liquid crystal is oriented and cured so that the coated liquid crystal forms a liquid crystal layer, thereby completing the preparation of the polarizer holographic grating; it should be understood that the arrangement direction of the liquid crystal is deflected under the action of the two-dimensional orientation layer. Specifically, the arrangement direction of the liquid crystal close to the two-dimensional orientation layer is the same as the orientation direction in the two-dimensional orientation layer. In the direction away from the two-dimensional orientation layer, although the force of the two-dimensional orientation layer on the liquid crystal gradually decreases, due to the properties of the liquid crystal itself, the arrangement direction of the liquid crystal will continue to rotate in the direction away from the two-dimensional orientation layer, so that the arrangement direction of the liquid crystal in this direction also presents periodic changes, thereby being able to form a first equal phase plane and a second equal phase plane in the liquid crystal layer, so that the prepared polarizer holographic grating has the diffraction characteristics of the two-dimensional grating, thereby realizing the preparation of a single-layer two-dimensional polarizer holographic grating.

[0069] In a specific implementation process, the coated liquid crystal is a cholesteric liquid crystal.

[0070] In some embodiments, the exposure beam includes a first exposure beam and a second exposure beam, and a polarization direction of the first exposure beam is opposite to a polarization direction of the second exposure beam.

[0071] In a specific embodiment, the first exposure beam and the second exposure beam simultaneously irradiate the area to be exposed in the orientation layer to be exposed from different directions to expose the area to be exposed, wherein the first exposure beam is left-handed circularly polarized light, the second exposure beam is right-handed circularly polarized light, and the first exposure beam and the second exposure beam are homologous beams.

[0072] The method for preparing a polarization volume holographic grating provided in the above embodiment solves the problem that the exposure method in the related art cannot prepare a two-dimensional polarization volume holographic grating.

[0073] See also Figure 8 , Figure 8 A schematic block diagram of the structure of an exposure system provided in one embodiment of the present application.

[0074] like Figure 8 As shown, the exposure system includes an exposure light source 100, a clamping mechanism 200 and a loading platform 300. The exposure light source 100 is used to provide an exposure beam to the orientation layer to be exposed, so as to expose the orientation layer to be exposed; the clamping mechanism 200 is used to clamp the mask, and in the exposure process of the orientation layer to be exposed, the clamped mask moves along a first preset direction; the loading platform 300 is used to carry the substrate layer and the orientation layer to be exposed arranged on the substrate layer, so that the exposure light provided by the exposure light source 100 can irradiate the orientation layer to be exposed placed on the loading platform 300, so as to expose the orientation layer to be exposed, and in the process of exposure, reciprocate in the second preset direction, so that the orientation layer to be exposed also reciprocates in the second preset direction, and in combination with the clamping mechanism 200 clamping the mask and moving along the first preset direction, two groups of equal phase lines with different directions can be exposed on the orientation layer to be exposed, thereby obtaining a two-dimensional orientation layer.

[0075] It should be noted that after the exposure system completes the exposure of the orientation layer to be exposed, the coating of liquid crystal and other processes can be continued through other equipment, or the coating of liquid crystal and other processes can be continued on the exposure system, which is not limited here.

[0076] In another embodiment, if the exposure process of the orientation layer to be exposed is that the orientation layer to be exposed is translated in the opposite direction of the first preset direction and reciprocated in the second preset direction, then the exposure system does not need to be equipped with a clamping mechanism, and only needs to enable the loading platform to translate in the first preset direction and reciprocate in the second preset direction. Those skilled in the art can set the exposure system according to actual exposure requirements, and this application does not limit it.

[0077] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0078] It should also be understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations. It should be noted that, in this article, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "including a..." does not exclude the presence of other identical elements in the process, method, article or system including the element.

[0079] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A polarization holographic grating, characterized in that: The polarization volume holographic grating comprises: basal layer; A two-dimensional alignment layer, wherein the two-dimensional alignment layer is arranged on the surface of the base layer, and the alignment direction of the two-dimensional alignment layer changes periodically in a first preset direction and in a second preset direction perpendicular to the first preset direction, so that the two-dimensional alignment layer forms a first equiphase line and a second equiphase line, and the angle between the first equiphase line and the second equiphase line is greater than zero; A liquid crystal layer, wherein the liquid crystal layer is arranged on a surface of the two-dimensional orientation layer away from the substrate layer, and the arrangement direction of the liquid crystal molecules in the liquid crystal layer corresponds to the orientation direction of the two-dimensional orientation layer, so that the liquid crystal layer forms a first isophase plane corresponding to the first isophase line and forms a second isophase plane corresponding to the second isophase line.

2. The polarization holographic grating according to claim 1, characterized in that: In the projection of the two-dimensional alignment layer along the direction of the base layer, the connecting lines between the position points in the same alignment direction are in a sawtooth shape.

3. The polarization holographic grating according to claim 1, characterized in that: The first preset direction is the X-axis direction of the preset coordinate system, the second preset direction is the Y-axis direction of the preset coordinate system, and the origin of the preset coordinate system is any point on the plane where the base layer is located.

4. The polarization volume holographic grating according to any one of claims 1 to 3, characterized in that: The substrate layer includes resin or glass; the two-dimensional alignment layer includes one of polyimide, organic azo compound and acrylate polymer; and the liquid crystal layer includes cholesteric liquid crystal.

5. A method for preparing a polarization holographic grating, characterized in that: The method for preparing the polarization volume holographic grating comprises: Providing a base layer, and coating an alignment layer to be exposed on a surface of the base layer; Providing a mask, and making the mask cover a portion of the alignment layer to be exposed that is away from the surface of the base layer; irradiating the alignment layer to be exposed with an exposure light beam to expose the to-be-exposed area on the surface of the alignment layer to be exposed that is not blocked by the mask to obtain a two-dimensional alignment layer; Wherein, during the process of the exposure light beam irradiating the alignment layer to be exposed, the mask is translated along a first preset direction and the alignment layer to be exposed reciprocates in a second preset direction, or the alignment layer to be exposed is translated along a direction opposite to the first preset direction and reciprocates in the second preset direction, so that the alignment direction of the two-dimensional alignment layer presents periodic changes in both the first preset direction and the second preset direction, so that the two-dimensional alignment layer forms a first equiphase line and a second equiphase line; The mask is removed, and liquid crystal is coated on the surface of the two-dimensional alignment layer facing away from the substrate layer to obtain the polarization holographic grating.

6. The method for preparing a polarization holographic grating according to claim 5, characterized in that: The mask is a light-proof plate, or a light-transmitting structure is provided on the mask, and the light-transmitting structure includes a slit or a through hole.

7. The method for preparing a polarization holographic grating according to claim 5, characterized in that: The mask is translated along a first preset direction on the surface of the alignment layer to be exposed, comprising: The relative displacement between the mask and the alignment layer to be exposed in the second preset direction is zero, and the mask is translated at a uniform speed or at a variable speed along the first preset direction.

8. The method for preparing a polarization holographic grating according to claim 5, characterized in that: The exposure beam includes a first exposure beam and a second exposure beam, and a polarization direction of the first exposure beam is opposite to a polarization direction of the second exposure beam.

9. The method for preparing a polarization volume holographic grating according to any one of claims 5 to 8, characterized in that: The method of coating liquid crystal on the surface of the two-dimensional alignment layer away from the substrate layer to obtain the polarization holographic grating comprises: After coating liquid crystal on the surface of the two-dimensional alignment layer away from the substrate layer, the liquid crystal is oriented and cured to form a liquid crystal layer, so as to obtain the polarization volume holographic grating; The arrangement direction of the liquid crystal molecules in the liquid crystal layer corresponds to the alignment direction of the two-dimensional alignment layer, so that the liquid crystal layer forms a first isophase plane corresponding to the first isophase line and a second isophase plane corresponding to the second isophase line.

10. An exposure system, characterized in that: The exposure system at least comprises: An exposure light source, the exposure light source is used to provide an exposure light beam to irradiate the alignment layer to be exposed; A clamping mechanism, wherein the clamping mechanism is used to clamp the mask and translate along a first preset direction during the process in which the exposure light source exposes the alignment layer to be exposed, and the mask is used to cover a portion of the surface of the alignment layer to be exposed; The loading platform is used to carry the base layer and the alignment layer to be exposed on the base layer, and to carry the alignment layer to be exposed to reciprocate in a second preset direction during the exposure light source exposing the alignment layer to be exposed.

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