All-solid-state h-pdlc volume holographic grating and preparation method thereof

Abstract

The application provides a full solid H-PDLC volume holographic grating and a preparation method thereof. The full solid H-PDLC volume holographic grating comprises a plurality of periodic structures and liquid crystal polymers between adjacent periodic structures, the liquid crystal polymers are polymerized from liquid crystal polymerizable monomers, and the periodic structures are non-liquid crystal polymers polymerized from non-liquid crystal polymerizable monomers. The application replaces small molecule liquid crystals in ordinary H-PDLC with liquid crystal polymers, can prepare a full solid H-PDLC without a substrate, thereby effectively reducing the volume of the device, and avoiding the influence of the substrate on the optical properties of the device.

Description

Technical Field

[0001] This application relates to the field of grating structure technology, and in particular to an all-solid-state H-PDLC volume holographic grating and its fabrication method. Background Technology

[0002] A diffraction grating is a diffractive optical element with a periodic spatial structure or optical properties. It modulates the amplitude and phase of incident light waves, and its main function is to achieve spatial separation of polychromatic light. It has been widely used in many fields such as spectroscopic instruments, astronomy, metrology, integrated optics, information processing, optical communication, and high-power laser systems. Based on the grating's dispersive properties, it can be divided into thin gratings (surface gratings) and bulk gratings. The former has incident energy distributed across all diffraction peaks, while the latter's incident energy is mainly concentrated on the first-order diffraction peak (theoretically, the first-order diffraction efficiency can reach 100%). Therefore, bulk gratings have significant advantages and potential in scenarios requiring high diffraction efficiency. Currently, the main material systems for fabricating bulk gratings are H-PDLC (holographic polymer-dispersed liquid crystal), photopolymers, silver halides, and dichromates. However, the refractive index modulation of photopolymers, silver halides, and dichromates is relatively small (generally below 0.05), which is not conducive to improving the grating's field of view (FOV). The high refractive index modulation (up to 0.1-0.3) of H-PDLC makes it the best choice for high FOV gratings. H-PDLC is composed of alternating layers of polymer and small molecule liquid crystals. The fluidity of the small molecule liquid crystals dictates that a sealed structure must be formed using upper and lower substrates during its fabrication and use. This undoubtedly increases the size of the device and inevitably has an unnecessarily negative impact on its optical properties. Summary of the Invention

[0003] The purpose of this application is to provide an all-solid-state H-PDLC volume holographic grating and its fabrication method. By using liquid crystal polymers to replace the small-molecule liquid crystals in ordinary H-PDLCs, all-solid-state, substrate-free H-PDLCs can be fabricated, thereby effectively reducing the device size and avoiding the influence of the substrate on the device's optical properties. The specific technical solution is as follows:

[0004] The first aspect of this application provides an all-solid-state H-PDLC volume holographic grating, comprising multiple periodic structures and liquid crystal polymers located between adjacent periodic structures, wherein the liquid crystal polymers are polymerized from liquid crystal polymerizable monomers, and the periodic structures are non-liquid crystal polymers polymerized from non-liquid crystal polymerizable monomers.

[0005] In some embodiments of this application, the refractive index modulation Δn between the liquid crystal polymer and the non-liquid crystal polymer is 0.001-0.5.

[0006] In some embodiments of this application, the liquid crystal polymer is obtained by photopolymerization or thermal polymerization; the non-liquid crystal polymer is obtained by photopolymerization.

[0007] The second aspect of this application provides a method for fabricating an all-solid-state H-PDLC volume holographic grating, comprising the steps of:

[0008] A liquid crystal slurry is prepared, wherein the liquid crystal slurry comprises a liquid crystal polymerizable monomer, a non-liquid crystal polymerizable monomer, and an initiator;

[0009] The liquid crystal slurry is used to fill the containment space, and then interference exposure is performed to cause the non-liquid crystal polymerizable monomers to polymerize, forming multiple periodic structures composed of non-liquid crystal polymers.

[0010] The liquid crystal slurry containing the non-liquid crystal polymer is subjected to light irradiation or heating, causing the liquid crystal polymerizable monomer to polymerize and form liquid crystal polymers between adjacent periodic structures, thereby obtaining the all-solid-state H-PDLC bulk holographic grating.

[0011] In some embodiments of this application, the liquid crystal slurry contains: the content of the liquid crystal polymerizable monomer is 4.5wt%-95wt%, the content of the non-liquid crystal polymerizable monomer is 0.5wt%-95wt%, and the content of the initiator is 0.05wt%-10wt%.

[0012] In some embodiments of this application, the method for preparing the accommodating space includes the steps of:

[0013] Provide a first substrate and a second substrate;

[0014] A first detachable layer is formed on one surface of the first substrate;

[0015] A sealing adhesive is formed between the first removable layer and the second substrate, wherein the sealing adhesive, the first removable layer, and the second substrate define an accommodating space.

[0016] In some embodiments of this application, after the liquid crystal polymer is formed and before the all-solid-state H-PDLC bulk holographic grating is obtained, the step of: performing a dissociation process on the first dissociable layer to peel off the first dissociable layer and the first substrate.

[0017] In some embodiments of this application, the method for preparing the accommodating space includes the steps of:

[0018] Provide a first substrate and a second substrate;

[0019] A first removable layer is formed on one surface of the first substrate; a second removable layer is formed on the side of the second substrate near the first removable layer;

[0020] A sealing adhesive is formed between the first removable layer and the second removable layer, the sealing adhesive, the first removable layer, and the second removable layer defining the containment space.

[0021] In some embodiments of this application, after forming the liquid crystal polymer and before obtaining the all-solid-state H-PDLC bulk holographic grating, the following steps are further included:

[0022] The first detachable layer is subjected to a detachment process to peel off the first detachable layer from the first substrate;

[0023] The second detachable layer is subjected to a detachment process to peel off the second detachable layer and the second substrate.

[0024] In some embodiments of this application, the thickness of the first dissociable layer is 30nm-500μm; the material forming the first dissociable layer is selected from mechanically separating materials, laser de-adhesion materials, or UV de-adhesion materials.

[0025] In some embodiments of this application, the dissociation process is mechanical peeling, laser dissociation, or UV light irradiation dissociation.

[0026] In some embodiments of this application, the thickness of the second dissociable layer is 30nm-500μm; the material forming the second dissociable layer is selected from mechanically separating materials, laser de-adhesion materials, or UV de-adhesion materials.

[0027] The third aspect of this application provides an optical device, including the all-solid-state H-PDLC volume holographic grating described in the first aspect of this application or an all-solid-state H-PDLC volume holographic grating prepared using the method described in the second aspect of this application.

[0028] The beneficial effects of this application are:

[0029] This application provides an all-solid-state H-PDLC volume holographic grating, which uses liquid crystal polymers to replace the small-molecule liquid crystals in ordinary H-PDLCs. While retaining the high Δn (refractive index modulation) of ordinary H-PDLCs, it enables H-PDLCs to form an all-solid-state structure, which can be used directly without a substrate, effectively reducing the size of the device and the optical influence of the substrate on the device. This application also provides a method for preparing the H-PDLC volume holographic grating, which adds a post-polymerization step to the conventional H-PDLC preparation steps, allowing liquid crystal polymerizable monomers to polymerize into liquid crystal polymers. Subsequently, the substrate is peeled off to obtain the H-PDLC volume holographic grating. The preparation method is simple and highly operable.

[0030] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0032] Figure 1 This is a schematic diagram of a substrate-free solid-state H-PDLC bulk holographic grating according to one embodiment of this application.

[0033] Figure 2 A schematic diagram of the structure of an all-solid-state H-PDLC volume holographic grating with a substrate on only one side, as another embodiment of this application;

[0034] Figure 3 A schematic diagram of the optical path setup for interference exposure;

[0035] Figure 4 This is a schematic diagram of the fabrication process of a substrate-free all-solid-state H-PDLC bulk holographic grating according to one embodiment of this application;

[0036] Figure 5 A schematic diagram of the fabrication process of an all-solid-state H-PDLC bulk holographic grating with a substrate on only one side, as another embodiment of this application;

[0037] Figure 6 This is a schematic diagram of multiple all-solid-state H-PDLC volume holographic grating structures prepared simultaneously according to another embodiment of this application.

[0038] In the figure, 1. All-solid-state H-PDLC volume holographic grating, 11. First (glass) substrate, 12. First removable layer, 21. Second (glass) substrate, 22. Second removable layer, 31. Sealing adhesive, 41. Accommodation space, 51. Liquid crystal slurry, 61. Non-liquid crystal polymer, 71. Liquid crystal polymer, 101. CW laser, 102. Shutter, 103. Beam expander, 104. Beam splitter, 105. Mirror, 106. Sample stage. Detailed Implementation

[0039] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0040] Current H-PDLCs are composed of alternating layers of polymers and small-molecule liquid crystals. The fluidity of the small-molecule liquid crystals dictates that they must be sealed using upper and lower substrates during preparation and use. This increases the size of the device, complicates the device structure, and inevitably has an unnecessarily negative impact on the device's optical properties.

[0041] The applicant discovered in their research that a key characteristic of H-PDLCs is that their diffraction efficiency can be modulated by an electric field. In many applications, such as the coupling-in and coupling-out gratings of AR devices, only the large Δn (refractive index modulation) characteristic is required, not the electrical modulation function. Therefore, liquid crystal polymers can be considered as a substitute for small-molecule liquid crystals. Liquid crystal polymers retain the large Δn characteristic of small-molecule liquid crystals; therefore, the original large Δn characteristic of H-PDLCs will not be affected.

[0042] The first aspect of this application provides an all-solid-state H-PDLC volume holographic grating, comprising multiple periodic structures and liquid crystal polymers located between adjacent periodic structures, wherein the liquid crystal polymers are polymerized from liquid crystal polymerizable monomers, and the periodic structures are non-liquid crystal polymers polymerized from non-liquid crystal polymerizable monomers.

[0043] In one embodiment of this application, such as Figure 1 As shown, the substrate-free all-solid-state H-PDLC bulk holographic grating 1 includes: a periodic structure formed by a plurality of non-liquid crystal polymers 61 and liquid crystal polymers 71 located between adjacent periodic structures.

[0044] In one embodiment of this application, such as Figure 2 As shown, the all-solid-state H-PDLC bulk holographic grating 1 with a substrate on only one side includes: a periodic structure formed by a plurality of non-liquid crystal polymers 61, a liquid crystal polymer 71 located between adjacent periodic structures, and a substrate 21, wherein the periodic structure formed by the plurality of non-liquid crystal polymers 61 and the liquid crystal polymer 71 located between adjacent periodic structures are located on one side of the substrate 21.

[0045] In one embodiment of this application, such as Figure 2 As shown, the all-solid-state H-PDLC holographic grating 1 with a substrate on only one side also includes a sealing adhesive 31, wherein the sealing adhesive 31 is located on one side of the substrate 21, and the sealing adhesive 31 and the substrate 21 form a semi-closed space, and the periodic structure formed by multiple non-liquid crystal polymers 61 and the liquid crystal polymers 71 located between adjacent periodic structures are filled in the semi-closed space.

[0046] This application does not particularly limit the type of liquid crystal polymerizable monomer, as long as it can achieve the purpose of this application and can undergo photopolymerization or thermal polymerization. For example, it can be selected from liquid crystal epoxy resin or liquid crystal acrylate polymerizable monomer; the liquid crystal acrylate polymerizable monomer includes at least one of the compounds shown in formula (I) and formula (II).

[0047]

[0048] A4, A5, and G4 are each independently selected from C1-C 16 Alkylene, C1-C 16 alkeneoxy or C1-C 16 Siloxyalkylene;

[0049] G5 is selected from C1-C 16 Alkyl, C1-C 16 Alkoxy or C1-C 16 Siloxane;

[0050] D4, D5, E4, and E5 are each independently selected from -C(O)O-, -C≡C-, -CH2-, -N=N-, -CH2-O-CH2-, or chemical bonds;

[0051] R1, R2 and R3 are each independently selected from acrylate groups;

[0052] J4, J5, L4, L5, M4, and M5 are each independently selected from C6-C. 18 Aromatic rings, C6-C 18 Aromatic heterocycles, C3-C 18 Aliphatic heterocycles or C3-C 18 adipose ring; of which, C6-C 18 Aromatic heterocycles and C3-C 18 The heteroatoms in the aliphatic ring are each independently selected from N, O, or S;

[0053] x4, x5, y4, y5, z4, and z5 are each independently selected from any integer between 0 and 4;

[0054] Q4, Q5, R4, R5, T4, and T5 are each independently selected from halogen, cyano, methyl, or methoxy groups;

[0055] k4, k5, m4, m5, n4, and n5 are each independently selected from any integer between 0 and 4.

[0056] This application does not particularly limit the type of non-liquid crystal polymerizable monomer, as long as it can achieve the inventive objective of this application and is capable of photopolymerization. For example, it can be selected from non-liquid crystal polymerizable acrylate monomers or epoxy resins. The non-liquid crystal polymerizable acrylate monomers include at least one of unsaturated polyesters, polyurethane acrylates, polyester acrylates, polyene thiols, polyether acrylates, waterborne acrylates, and vinyl ethers. This application does not particularly limit the specific types of unsaturated polyesters, polyurethane acrylates, polyester acrylates, polyene thiols, polyether acrylates, waterborne acrylates, and vinyl ethers, as long as they can achieve the inventive objective of this application. For example, pentaerythritol tetraacrylate can be used, which can be purchased commercially.

[0057] In some embodiments of this application, the refractive index modulation Δn between the liquid crystal polymer and the non-liquid crystal polymer is 0.001-0.5. In some embodiments of this application, the refractive index modulation Δn between the liquid crystal polymer and the non-liquid crystal polymer can be 0.001, 0.005, 0.01, 0.05, 0.1, 0.2, 0.5, or a range consisting of any two values ​​within this range.

[0058] In some embodiments of this application, the liquid crystal polymer is obtained by photopolymerization or thermal polymerization; the non-liquid crystal polymer is obtained by photopolymerization.

[0059] This application selects photoinitiators or thermal polymerization initiators to initiate the polymerization of liquid crystal polymerizable monomers into liquid crystal polymers, based on the properties of the liquid crystal polymerizable monomers; and uses photoinitiators to initiate the polymerization of non-liquid crystal polymerizable monomers into liquid crystal polymers. For liquid crystal polymerizable monomers such as liquid crystal epoxy resins, anionic or cationic initiators can be selected to initiate the polymerization of liquid crystal epoxy resins into liquid crystal polymers.

[0060] The second aspect of this application provides a method for fabricating an all-solid-state H-PDLC volume holographic grating, comprising the steps of:

[0061] A liquid crystal slurry is prepared, wherein the liquid crystal slurry comprises a liquid crystal polymerizable monomer, a non-liquid crystal polymerizable monomer, and an initiator;

[0062] The liquid crystal slurry is used to fill the containment space, and then interference exposure is performed to cause the non-liquid crystal polymerizable monomers to polymerize, forming multiple periodic structures composed of non-liquid crystal polymers.

[0063] The liquid crystal slurry containing the non-liquid crystal polymer is subjected to light irradiation or heating, causing the liquid crystal polymerizable monomer to polymerize and form liquid crystal polymers between adjacent periodic structures, thereby obtaining the all-solid-state H-PDLC bulk holographic grating.

[0064] The liquid crystal slurry of this application is formed by uniformly mixing liquid crystal polymerizable monomers, non-liquid crystal polymerizable monomers and initiators.

[0065] This application selects either a photoinitiator or a thermal polymerization initiator to initiate the polymerization of liquid crystal polymerizable monomers into liquid crystal polymers, depending on the properties of the liquid crystal polymerizable monomers; and uses a photoinitiator to initiate the polymerization of non-liquid crystal polymerizable monomers into non-liquid crystal polymers. If a photoinitiator is selected, the liquid crystal slurry containing non-liquid crystal polymers is irradiated with light during the preparation process; if a thermal polymerization initiator is selected, the liquid crystal slurry containing non-liquid crystal polymers is heated during the preparation process.

[0066] If a photoinitiator is used to initiate the polymerization of liquid crystal polymerizable monomers to form liquid crystal polymers, then the photoinitiator used in this application can initiate the polymerization of liquid crystal polymerizable monomers and non-liquid crystal polymerizable monomers at the same or different wavelengths. This application does not particularly limit the specific type of photoinitiator, as long as it can achieve the purpose of this application. It may include one or more photoinitiators, such as N-phenylglycine ethyl ester and Rose Bengal (CAS NO.: 632-69-9).

[0067] If a thermal polymerization initiator is used to initiate the polymerization of liquid crystal polymerizable monomers to form a liquid crystal polymer, then the photoinitiator used in this application only needs to be able to initiate the polymerization of non-liquid crystal polymerizable monomers. This application does not have any particular restrictions on the specific types of photoinitiators and thermal polymerization initiators, as long as they can achieve the purpose of this application.

[0068] This application does not impose any particular limitation on the specific method of filling the containment space with liquid crystal slurry, as long as the purpose of this invention can be achieved. For example, liquid crystal slurry can be filled into the containment space by using VAS (Vacuum Align System), vacuum infusion process or capillary action.

[0069] The interference exposure optical path setup in this application is as follows: Figure 3As shown, it mainly consists of a CW laser 101, a shutter 102, a beam expander 103, a beam splitter 104, a reflector 105, and a sample stage 106. The angle between the interference beams is determined by the parameters of the grating to be prepared. The wavelength of the laser used for exposure is determined by the absorption wavelength range of the photoinitiator of the non-liquid crystal polymerizable monomer. Since the polymerization rate of the non-liquid crystal polymerizable monomer is faster than that of the liquid crystal polymerizable monomer, the non-liquid crystal polymerizable monomer can be polymerized by controlling the optical power density and illumination time to form a general H-PDLC, while the liquid crystal polymerizable monomer does not polymerize (or hardly polymerizes). The direction of the grating period is perpendicular to the angle bisector of the two interference beams.

[0070] After the interference exposure, the liquid crystal slurry no longer contains non-liquid-liquid polymerizable monomers, but only liquid-liquid polymerizable monomers, exhibiting a liquid state and liquid fluidity. Then, ordinary light source irradiation is used to polymerize the liquid-liquid polymerizable monomers to form liquid crystal polymers. The exposure wavelength is determined by the absorption wavelength range of the photoinitiator of the liquid-liquid polymerizable monomers (generally the same photoinitiator as the non-liquid-liquid polymerizable monomers is used); alternatively, heating is used to polymerize the liquid-liquid polymerizable monomers to form liquid crystal polymers, thus completing the preparation of all-solid-state H-PDLC.

[0071] This application does not impose any particular restrictions on the ordinary light source used for light irradiation, as long as it can cause the liquid crystal polymerizable monomers to polymerize and form liquid crystal polymers. The light source can be selected based on the type of photoinitiator; for example, ordinary fluorescent lamps can be used for irradiation for 10-60 minutes. This application also does not impose any particular restrictions on the heating temperature and time, as long as it can cause the liquid crystal polymerizable monomers to polymerize and form liquid crystal polymers. The heating temperature can be selected based on the type of thermal polymerization initiator.

[0072] In some embodiments of this application, the liquid crystal slurry contains: the content of the liquid crystal polymerizable monomer is 4.5 wt%-95 wt%, the content of the non-liquid crystal polymerizable monomer is 0.5 wt%-95 wt%, and the content of the initiator is 0.05 wt%-10 wt%. In some embodiments of this application, the mass percentage of the liquid crystal polymerizable monomer in the liquid crystal slurry can be 4.5 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or any two values ​​thereof; the mass percentage of the non-liquid crystal polymerizable monomer can be 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 10 wt%, 1 The mass percentage of the initiator can be 5 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or any two values ​​within this range; the total mass percentage of the liquid crystal polymerizable monomer, the non-liquid crystal polymerizable monomer, and the initiator is 100 wt%.

[0073] In this application, if a thermal polymerization initiator is used to initiate the polymerization of liquid crystal polymerizable monomers to form a liquid crystal polymer, the initiator includes both a photoinitiator and a thermal polymerization initiator, and the specific amounts of the photoinitiator and the thermal polymerization initiator can be selected according to actual needs; if a photoinitiator is used to initiate the polymerization of liquid crystal polymerizable monomers to form a liquid crystal polymer, the initiator only includes the photoinitiator.

[0074] In some embodiments of this application, the method for preparing the accommodating space includes the following steps:

[0075] Provide a first substrate and a second substrate;

[0076] A first detachable layer is formed on one surface of the first substrate;

[0077] A sealant is formed between the first removable layer and the second substrate, the sealant, the first removable layer and the second substrate defining an accommodating space.

[0078] In some embodiments of this application, after the liquid crystal polymer is formed and before the all-solid-state H-PDLC bulk holographic grating is obtained, the step of: performing a dissociation process on the first dissociable layer to peel off the first dissociable layer and the first substrate.

[0079] This application does not impose any particular restrictions on the materials of the first substrate and the second substrate, as long as the inventive purpose of this application can be achieved, such as using a glass substrate.

[0080] This application does not impose any particular limitation on the size relationship between the first substrate and the second substrate; they can be the same or different. For the same second substrate, multiple first removable layers can be disposed opposite to each other, forming multiple accommodating spaces with the sealant, thereby fabricating multiple all-solid-state H-PDLC volume holographic gratings (the area of ​​the second substrate is larger than that of a single H-PDLC).

[0081] This application does not impose any particular restrictions on the specific type of sealing adhesive, as long as it can achieve the purpose of this invention, such as 502, S-WB101R or SS85.

[0082] In some embodiments of this application, the method for preparing the accommodating space includes the steps of:

[0083] Provide a first substrate and a second substrate;

[0084] A first removable layer is formed on one surface of the first substrate; a second removable layer is formed on the side of the second substrate near the first removable layer;

[0085] A sealing adhesive is formed between the first removable layer and the second removable layer, the sealing adhesive, the first removable layer, and the second removable layer defining the containment space.

[0086] In some embodiments of this application, after forming the liquid crystal polymer and before obtaining the all-solid-state H-PDLC bulk holographic grating, the following steps are further included:

[0087] The first detachable layer is subjected to a detachment process to peel off the first detachable layer from the first substrate;

[0088] The second detachable layer is subjected to a detachment process to peel off the second detachable layer and the second substrate.

[0089] This application does not impose any particular limitation on the method for preparing the first and second detachable layers, as long as it can achieve the purpose of this invention. For example, coating can be performed by Spin (rotary coating) / Slit (slit coating) and Coater (coating paper coating), and the film can be formed by exposure curing, UV curing or heat curing after coating is completed.

[0090] In some embodiments of this application, the thickness of the first dissociable layer is 30 nm-500 μm.

[0091] In some embodiments of this application, the thickness of the second dissociable layer is 30 nm to 500 μm.

[0092] In some embodiments of this application, the thickness of the first detachable layer and the thickness of the second detachable layer can be 30nm, 100nm, 300nm, 500nm, 800nm, 1μm, 5μm, 10μm, 50μm, 100μm, 300μm, 500μm, or a range of any two values ​​therein.

[0093] In some embodiments of this application, the material forming the first dissociable layer is selected from mechanically dissociable materials (DBL), laser de-adhesion materials, or UV de-adhesion materials.

[0094] In some embodiments of this application, the material forming the second dissociable layer is selected from mechanically dissociable materials (DBL), laser de-adhesion materials, or UV de-adhesion materials.

[0095] In some embodiments of this application, the dissociation process is mechanical peeling, laser dissociation, or UV light irradiation dissociation.

[0096] The following is a flowchart. Figure 4 The steps involved in the fabrication method of all-solid-state H-PDLC volume holographic grating are further explained.

[0097] (1)Reference Figure 4 As shown in Figure a, a first substrate 11 is provided, and a first detachable layer 12 with a thickness of 30nm-500μm is formed on one surface of the first substrate 11; a second substrate 21 is provided, and a second detachable layer 22 with a thickness of 30nm-500μm is formed on one surface of the second substrate 21.

[0098] (2)Reference Figure 4 As shown in Figure b, the first removable layer 12 and the second removable layer 22 are placed opposite each other, and a sealing adhesive 31 is formed between the first removable layer 12 and the second removable layer 22. The sealing adhesive 31, the first removable layer 12 and the second removable layer 22 define an accommodating space 41.

[0099] (3)Reference Figure 4 As shown in Figure c, liquid crystal slurry 51 is used to fill the accommodating space 41.

[0100] (4)Reference Figure 4 As shown in d, interference exposure is performed to cause the non-liquid crystal polymerizable monomers to polymerize, forming multiple periodic structures composed of non-liquid crystal polymer 61.

[0101] (5)Reference Figure 4 As shown in Figure e, ordinary light irradiation or heating is used to polymerize liquid crystal polymerizable monomers, forming liquid crystal polymers 71 between adjacent periodic structures. The periodic structure composed of multiple non-liquid crystal polymers 61 and the liquid crystal polymers 71 between adjacent periodic structures form a grating.

[0102] (6)Reference Figure 4 As shown in Figure f, the first detachable layer 12 and the second detachable layer 22 are disassembled to peel the first detachable layer 12, the first substrate 11, the second detachable layer 22 and the second substrate 21 off from the grating, and the sealant 31 is removed to obtain a substrate-free all-solid-state H-PDLC volume holographic grating 1.

[0103] The following is a flowchart. Figure 5 The steps involved in another method for fabricating an all-solid-state H-PDLC volume holographic grating are further explained.

[0104] (1)Reference Figure 5 As shown in Figure a, a first substrate 11 is provided, and a first detachable layer 12 with a thickness of 30nm-500μm is formed on one surface of the first substrate 11; a second substrate 21 is provided.

[0105] (2)Reference Figure 5 As shown in Figure b, the first removable layer 12 and the second substrate 21 are placed opposite each other, and a sealing adhesive 31 is formed between the first removable layer 12 and the second substrate 21. The sealing adhesive 31, the first removable layer 12 and the second substrate 21 define an accommodating space 41.

[0106] (3)Reference Figure 5 As shown in Figure c, liquid crystal slurry 51 is used to fill the accommodating space 41.

[0107] (4)Reference Figure 5 As shown in d, interference exposure is performed to cause the non-liquid crystal polymerizable monomers to polymerize, forming multiple periodic structures composed of non-liquid crystal polymer 61.

[0108] (5)Reference Figure 5As shown in Figure e, ordinary light irradiation or heating is used to polymerize liquid crystal polymerizable monomers, forming liquid crystal polymers 71 between adjacent periodic structures. The periodic structure composed of multiple non-liquid crystal polymers 61 and the liquid crystal polymers 71 between adjacent periodic structures form a grating.

[0109] (6)Reference Figure 5 As shown in Figure f, the first detachable layer 12 is disassembled to peel off the first detachable layer 12 and the first substrate 11 from the grating, resulting in an all-solid-state H-PDLC volume holographic grating 1 with a substrate (second substrate 21) on only one side.

[0110] In one embodiment of this application, the above process is repeated using two polymerization systems with different initiation wavelengths. Figure 4 or Figure 5 The steps involve constructing a grating periodic structure for each polymerization system; or, a photoinitiated polymerization system can be used to prepare non-liquid crystal polymers, while a thermal polymerization system (such as liquid crystal epoxy polymerizable monomers) can be used to prepare liquid crystal polymers. In this case, since liquid crystal epoxy polymerizable monomers do not have the possibility of polymerization during interference exposure, the process requirements for interference exposure are greatly reduced.

[0111] This application addresses the problem that the liquid flow of small-molecule liquid crystals in general H-PDLCs necessitates the use of upper and lower substrates for encapsulation during application. It proposes to use liquid crystal polymers to replace the small-molecule liquid crystals in ordinary H-PDLCs to prepare all-solid-state H-PDLCs. Subsequently, a substrate peeling process is used to prepare all-solid-state, substrate-free H-PDLCs, thereby effectively reducing the size of the device and avoiding the influence of the substrate on the optical properties of the device.

[0112] In one embodiment of this application, such as Figure 6 As shown, a schematic diagram of a structure of multiple all-solid-state H-PDLC volume holographic gratings prepared simultaneously is provided, wherein the area of ​​the second substrate 21 is larger than the area of ​​a single all-solid-state H-PDLC volume holographic grating 1; there are two all-solid-state H-PDLC volume holographic gratings 1 and corresponding sealing adhesives 31 on the same second substrate 21.

[0113] Glass can serve as the waveguide structure for AR devices, allowing diffracted light from an all-solid-state H-PDLC to directly enter the waveguide and propagate in a specific direction according to the design. Multiple all-solid-state H-PDLCs can also be fabricated simultaneously on the same glass. For example, two all-solid-state H-PDLCs can be used as the input-coupled holographic grating and output-coupled holographic grating of the waveguide structure, respectively.

[0114] The third aspect of this application provides an optical device, including the all-solid-state H-PDLC volume holographic grating described in the first aspect of this application or an all-solid-state H-PDLC volume holographic grating prepared using the method described in the second aspect of this application.

[0115] The following examples illustrate the implementation of this application in more detail.

[0116] Example 1

[0117] (1) Mix 50wt% of the liquid crystal polymerizable acrylate monomer shown in formula (I), 48wt% of pentaerythritol tetraacrylate (non-liquid crystal polymerizable monomer), 1.5wt% of N-phenylglycine ethyl ester (photoinitiator) and 0.5wt% of Rose Bengal (CAS NO.:632-69-9, photoinitiator) evenly to obtain a liquid crystal slurry.

[0118] (2) Figure 4 As shown in Figure a, a mechanically detachable material (DBL) is spin-coated onto one surface of the first glass substrate 11 to form a first detachable layer 12 with a thickness of 100 μm; a mechanically detachable material (DBL) is spin-coated onto one surface of the second glass substrate 21 to form a second detachable layer 22 with a thickness of 100 μm.

[0119] (3) Figure 4 As shown in Figure b, the first removable layer 12 and the second removable layer 22 are placed opposite each other. A sealing adhesive 31 is formed between the first removable layer 12 and the second removable layer 22 using S-WB101R. The sealing adhesive 31, the first removable layer 12 and the second removable layer 22 define an accommodating space 41.

[0120] (4) Figure 4 As shown in Figure c, the liquid crystal slurry 51 prepared in step (1) is filled into the accommodating space 41 by VAS.

[0121] (5) Figure 3 The interference exposure optical path shown is mainly composed of a CW laser 101, shutter 102, beam expander 103, beam splitter 104, mirror 105, and sample stage 106; then... Figure 4 As shown in Figure d, interferometric exposure was performed using a laser wavelength of 532 nm, with an optical power density of 7 mW / cm². 2 The illumination time is 10 minutes, which causes the non-liquid crystal polymerizable monomers to polymerize and form multiple periodic structures composed of non-liquid crystal polymer 61. The periodic direction of the grating is perpendicular to the angle bisector direction of the two interference beams.

[0122] (6) Figure 4As shown in Figure e, ordinary fluorescent lamps are used for irradiation for 1 hour, which causes the liquid crystal polymerizable monomers to polymerize and form liquid crystal polymers 71 between adjacent periodic structures. The periodic structures composed of multiple non-liquid crystal polymers 61 and the liquid crystal polymers 71 between adjacent periodic structures form a grating.

[0123] (7) Figure 4 As shown in Figure f, the first detachable layer 12 and the second detachable layer 22 are separated by mechanical peeling, so that the first detachable layer 12, the first glass substrate 11, the second detachable layer 22 and the second glass substrate 21 are peeled off from the grating, and the sealant 31 is removed, resulting in a glass substrate-free all-solid-state H-PDLC volume holographic grating 1.

[0124] Example 2

[0125] (1) Mix 50wt% of the liquid crystal polymerizable acrylate monomer shown in formula (I), 48wt% of pentaerythritol tetraacrylate (non-liquid crystal polymerizable monomer), 1.5wt% of N-phenylglycine ethyl ester (photoinitiator) and 0.5wt% of Rose Bengal (CAS NO.:632-69-9, photoinitiator) evenly to obtain a liquid crystal slurry.

[0126] (2) Figure 5 As shown in Figure a, mechanically separable material (DBL) is spin-coated onto one surface of the first glass substrate 11 to form a first separable layer 12 with a thickness of 100 μm.

[0127] (3) Figure 5 As shown in Figure b, the first removable layer 12 and the second glass substrate 21 are placed opposite each other. A sealant 31 is formed between the first removable layer 12 and the second glass substrate 21 using S-WB101R. The sealant 31, the first removable layer 12 and the second glass substrate 21 define an accommodating space 41.

[0128] (4) Figure 5 As shown in Figure c, the liquid crystal slurry 51 prepared in step (1) is filled into the accommodating space 41 by VAS.

[0129] (5) Figure 3 The interference exposure optical path shown is mainly composed of a CW laser 101, shutter 102, beam expander 103, beam splitter 104, mirror 105, and sample stage 106; then... Figure 5 As shown in Figure d, the first interferometric exposure was performed using a laser wavelength of 532 nm, with an optical power density of 7 mW / cm². 2The illumination time is 10 minutes, which causes the non-liquid crystal polymerizable monomers to polymerize and form multiple periodic structures composed of non-liquid crystal polymer 61. The periodic direction of the grating is perpendicular to the angle bisector direction of the two interference beams.

[0130] (6) Figure 5 As shown in Figure e, a common light source, fluorescent lamp, is used for irradiation for 1 hour, which causes the liquid crystal polymerizable monomers to polymerize and form liquid crystal polymers 71 between adjacent periodic structures. The periodic structure composed of multiple non-liquid crystal polymers 61 and the liquid crystal polymers 71 between adjacent periodic structures form a grating.

[0131] (7) Figure 5 As shown in f, the first detachable layer 12 is disassembled by mechanical peeling, so that the first detachable layer 12 and the first glass substrate 11 are peeled off from the grating, resulting in an all-solid-state H-PDLC volume holographic grating 1 with only one side having a glass substrate (second glass substrate 21).

[0132] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a full solid-state H-PDLC volume holographic grating, comprising the steps of: preparing a liquid crystal slurry, the liquid crystal slurry comprising liquid-crystalline polymerizable monomers, non-liquid-crystalline polymerizable monomers, and an initiator; filling a containing space with the liquid crystal slurry, and then performing interference exposure, so that the non-liquid-crystalline polymerizable monomers are polymerized to form a plurality of periodic structures composed of non-liquid-crystalline polymers; and performing light irradiation or heating on the liquid crystal slurry containing the non-liquid-crystalline polymers, so that the liquid-crystalline polymerizable monomers are polymerized to form liquid crystal polymers between adjacent periodic structures, thereby obtaining the full solid-state H-PDLC volume holographic grating. In the liquid crystal slurry, the content of the liquid-crystalline polymerizable monomers is 4.5 wt%-95 wt%, the content of the non-liquid-crystalline polymerizable monomers is 0.5 wt%-95 wt%, and the content of the initiator is 0.05 wt%-10 wt%. The method for preparing the containing space comprises the steps of: providing a first substrate and a second substrate; forming a first detachable layer on one surface of the first substrate; and forming a sealant between the first detachable layer and the second substrate, the sealant, the first detachable layer, and the second substrate defining the containing space. 4.The method according to claim 3, wherein, after the liquid crystal polymers are formed and before the full solid-state H-PDLC volume holographic grating is obtained, the method further comprises the step of: performing a detachment treatment on the first detachable layer, so that the first detachable layer and the first substrate are peeled off. The method for preparing the containing space comprises the steps of: providing a first substrate and a second substrate; forming a first detachable layer on one surface of the first substrate; and forming a second detachable layer on the side of the second substrate close to the first detachable layer; and forming a sealant between the first detachable layer and the second detachable layer, the sealant, the first detachable layer, and the second detachable layer defining the containing space. 6.The method according to claim 5, wherein, after the liquid crystal polymers are formed and before the full solid-state H-PDLC volume holographic grating is obtained, the method further comprises the steps of: performing a detachment treatment on the first detachable layer, so that the first detachable layer and the first substrate are peeled off; and performing a detachment treatment on the second detachable layer, so that the second detachable layer and the second substrate are peeled off.

2. The production method according to claim 1, wherein The thickness of the first detachable layer is 30 nm-500 μm; and the material forming the first detachable layer is selected from a mechanically detachable material, a laser detackifying material, or a UV detackifying material.

3. The production method according to claim 1, wherein, 8.The method according to claim 4 or 6, wherein, the detachment treatment is mechanical peeling, laser detachment, or UV light irradiation detachment. 9.The method according to claim 5 or 6, wherein, the thickness of the second detachable layer is 30 nm-500 μm; and the material forming the second detachable layer is selected from a mechanically detachable material, a laser detackifying material, or a UV detackifying material. 10.An optical device comprising the full solid-state H-PDLC volume holographic grating prepared by the method according to any one of claims 1-9. ​ ​ ​ ​ 5. The production method according to claim 1, wherein ​ ​ ​ ​ ​ ​ ​ ​ 7. The production process according to any one of claims 3 to 6, wherein ​ ​ ​ ​ ​ ​ ​ ​

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