Light replication preparation method of dodging sheet

Abstract

The invention belongs to the field of optics, and relates to a light replication preparation method of a dodging sheet, which comprises the following steps: S1, preparing a liquid crystal box; and S2, filling the mixture of the liquid crystal and the photosensitive prepolymer into a liquid crystal box to obtain a liquid crystal box sample. And S3, placing the liquid crystal box sample in a light path of a light replication exposure device, wherein the device comprises a laser light source, a beam expanding and collimating assembly, a dodging sheet template and a second focusing lens. Light rays of the laser light source pass through the beam expanding and collimating assembly to form parallel light, the parallel light is emitted to the dodging sheet template, a light field carrying dodging sheet template information is obtained, the light field passes through the second focusing lens and then is emitted to a liquid crystal box sample for exposure, and the polymer dispersed liquid crystal dodging sheet is obtained. The light replication preparation method provided by the invention has the advantages of simple steps, simple device, low cost and mass production, can realize size customization of the polymer dispersed liquid crystal dodging sheet, obtains the dodging sheet with the micro-nano structure size of micron dimension or even hundred-nanometer dimension, and has the characteristic of high resolution.

Description

Technical Field

[0001] The invention relates to the technical field of optical engineering, and in particular to a method for preparing a light-homogenizing sheet through optical replication. Background Art

[0002] A light homogenizer, also known as a diffuser, scatters light through its surface, spreading the light evenly, so it has the function of diffusing and evenly distributing light. Light homogenizers are widely used in lighting, display, projection, laser processing and other application fields. Common light homogenizers such as frosted glass and coated diffusers can produce a light homogenization effect by constructing a concave-convex structure on the surface of the substrate or coating optical scattering particles. However, this type of light homogenizer has a high roughness and is difficult to control. It is mainly used in lighting, photography, display screens and other fields.

[0003] With the development of science and technology, some application scenarios have put forward higher requirements for light homogenizers. For example, in projection display, in addition to uniform light, light homogenizers also need to form a certain anisotropic diffusion shape and diffusion angle to meet a wide range of viewing needs. In addition, in some specific applications, it is also necessary to accurately control the diffusion angle, and at the same time, it is also necessary to keep the light within the diffusion angle uniformly close to the flat-top distribution to better improve the light efficiency of the system. In order to meet the above application requirements, microlens arrays came into being. The surface of the light homogenizer based on the microlens array is irregularly and tightly arranged with tiny lenses of different structures. After the incident light wavefront is focused by each small lens in space, the light spots are superimposed, thereby homogenizing the light and realizing beam shaping. By accurately designing the size and distribution of the microlenses, the target shape and angle of the beam can be homogenized and diffused. Microlens arrays at the micrometer level can achieve a higher precision light diffusion effect.

[0004] In the prior art, high-precision light diffusers are mainly composed of microstructures and microlens arrays, and their processing and preparation mainly rely on microstructure processing technologies such as photolithography, etching, and polishing, which have high manufacturing costs and high requirements for manufacturing processes. In addition, the size of the microstructures prepared by the existing processing technology is limited to the micron level, which is difficult to meet the requirements of higher precision at the submicron level, which limits the application of light diffusers in the field of high-resolution display and imaging.

[0005] Therefore, it is necessary to reduce the manufacturing cost of the light diffuser and reduce the size of the microstructure of the light diffuser. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In order to solve the problems in the prior art that the manufacturing cost of a high-precision light homogenizer is high, the manufacturing process is complex, and the size of the microstructure of the prepared light homogenizer can only reach the micron level, the present invention provides a method for preparing a light homogenizer by optical replication.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] A method for preparing a light-homogenizing sheet by optical replication comprises the following steps:

[0011] S1: preparing a liquid crystal cell;

[0012] S2: mixing the liquid crystal and the photosensitive prepolymer to obtain a mixture, and pouring the mixture into a liquid crystal box to obtain a liquid crystal box sample;

[0013] S3: placing the liquid crystal box sample in the light path of the optical replication exposure device, the optical replication exposure device includes a laser light source, a beam expander and collimator assembly, a homogenizer template and a second focusing lens arranged in sequence, the light emitted by the laser light source passes through the beam expander and collimator assembly to form parallel light, the parallel light hits the homogenizer template, and a light field carrying the homogenizer template information is obtained, the liquid crystal box sample is placed on the other side of the second focusing lens, the light field carrying the homogenizer template information is focused by the second focusing lens and hits the liquid crystal box sample for exposure, so that the photosensitive prepolymer is polymerized according to the homogenizer template information carried by the light field, and then separated from the liquid crystal phase, to obtain a polymer dispersed liquid crystal homogenizer.

[0014] In the above-mentioned method for preparing the light homogenizing sheet by optical replication, preferably, in step S1, the cleaned glass substrates are assembled into a liquid crystal box.

[0015] In the photoreplication preparation method of the light homogenizing sheet as described above, preferably, in step S2, the mass proportion of the liquid crystal in the mixture is 20%-80%, the photosensitive prepolymer includes an acrylate monomer and a photoinitiator, the mass proportion of the acrylate monomer in the photosensitive prepolymer is 20%-80%, and the mass proportion of the photoinitiator in the photosensitive prepolymer is 1%-10%.

[0016] In the above-mentioned method for preparing the light homogenizing sheet by optical replication, preferably, in step S2, the liquid crystal is a nematic liquid crystal, including E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal.

[0017] In the above-mentioned method for preparing the light homogenizing sheet by photoreplication, preferably, in step S2, the acrylate monomer is dipentaerythritol penta- / hexyl-acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate or tri(propylene glycol) diacrylate, and the photoinitiator is Bengal rose red, methyl blue or 2,2-dimethoxy-2-phenylacetophenone.

[0018] In the photoreplication preparation method of the light-homogenizing sheet as described above, preferably, in step S2, the photosensitive prepolymer also includes a cross-linking agent and a co-initiator, the cross-linking agent is N-vinyl pyrrolidone, and its mass proportion in the photosensitive prepolymer is 20%-80%; the co-initiator is N-phenylglycine or p-toluenesulfonic acid, and its mass proportion in the photosensitive prepolymer is 0.5%-5%.

[0019] In the above-mentioned method for preparing the light homogenizing sheet by optical replication, preferably, in step S2, the photosensitive prepolymer is a photocurable adhesive, and the photocurable adhesive is NOA65 or NOA61;

[0020] In step S2, a surfactant and high refractive index particles are also added to the mixture;

[0021] The surfactant is octanoic acid, and the high refractive index particles are titanium dioxide nanoparticles.

[0022] In the above-mentioned method for preparing the light homogenizing sheet by optical replication, preferably, in step S3, the wavelength of the laser light source is 365 nm, 488 nm, 532 nm, 633 nm or 850 nm.

[0023] In the above-mentioned method for preparing the light-homogenizing sheet by optical replication, preferably, in step S3, the exposure light intensity is 1 mW / cm 2 -100mW / cm 2 The exposure time is 30s-30min.

[0024] In the above-mentioned method for preparing the light homogenizer by optical replication, preferably, in step S3, before placing the liquid crystal box sample in the optical path of the optical replication exposure device, firstly confirm the placement position of the liquid crystal box sample in the optical path of the optical replication exposure device by using an objective lens and a CCD camera; wherein the objective lens is arranged on the CCD camera and is located on the side facing the second focusing lens;

[0025] The beam expansion and collimation assembly includes a first focusing lens, a pinhole filter and a collimating lens.

[0026] (III) Beneficial effects

[0027] The optical replication preparation method of the light homogenizer of the present invention can be based on a simple optical replication exposure device, and the replication of the existing light homogenizer template based on the microstructure or microlens array can be achieved through a single exposure. It has the advantages of simple steps, simple equipment, low cost, and mass production. Batch replication can be achieved with only one light homogenizer template, and it can replace complex micro-nano processing process flows.

[0028] The method for preparing a homogenizer by optical replication of the present invention can not only replicate the microstructure in the homogenizer template in equal proportion, but also realize the control of the replication ratio, that is, the size of the microstructure in the homogenizer template, by adjusting the different positions of the liquid crystal box sample in the light path of the optical replication exposure device to produce different replication effects, such as different diffusion shapes and diffusion angles, so as to achieve the size customization of the polymer dispersed liquid crystal homogenizer, and then obtain micron-level and submicron-level homogenizers, whose micro-nano structure size can reach the micron level to the hundred nanometer level, and has the characteristics of high resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The process flow chart of the optical replication preparation method of the light homogenizing sheet in the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the optical copy exposure device of the present invention;

[0031] Figure 3 Another structural schematic diagram of the optical duplication exposure device of the present invention (including a position detection component);

[0032] Figure 4 a is a microscopic image of the polymer dispersed liquid crystal homogenizer prepared in Example 1;

[0033] Figure 4 b is a schematic diagram of the scattering effect of the polymer dispersed liquid crystal homogenizer prepared in Example 1 on the laser spot;

[0034] Figure 5 a is a microscopic image of the polymer dispersed liquid crystal homogenizing sheet prepared in Example 2;

[0035] Figure 5 b is a schematic diagram of the scattering effect of the polymer dispersed liquid crystal homogenizer prepared in Example 2 on the laser spot.

[0036] [Description of Reference Numerals]

[0037] 1: laser light source; 2: beam expansion and collimation assembly; 21: first focusing lens; 22: pinhole filter; 23: collimating lens; 3: light homogenizer template; 4: second focusing lens; 5: liquid crystal box sample; 6: CCD camera. DETAILED DESCRIPTION

[0038] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific implementation methods.

[0039] like Figure 1-3 As shown, the present invention provides a method for preparing a light-homogenizing sheet by optical replication, comprising the following steps:

[0040] S1: preparing a liquid crystal cell.

[0041] S2: Mix the liquid crystal and the photosensitive prepolymer to obtain a mixture, and pour the mixture into a liquid crystal box to obtain a liquid crystal box sample 5.

[0042] S3: Place the liquid crystal box sample 5 in the light path of the optical replication exposure device, which includes a laser light source 1, a beam expander and collimator component 2, a homogenizer template 3 and a second focusing lens 4 arranged in sequence. The light emitted by the laser light source 1 passes through the beam expander and collimator component 2 to form parallel light, and the parallel light hits the homogenizer template 3 to obtain a light field carrying the homogenizer template information. Place the liquid crystal box sample 5 on the other side of the second focusing lens 4, and the light field carrying the homogenizer template information is focused by the second focusing lens 4 and hits the liquid crystal box sample 5 for exposure, so that the photosensitive prepolymer is polymerized according to the homogenizer template information carried by the light field, and then separated from the liquid crystal phase to obtain a polymer dispersed liquid crystal homogenizer.

[0043] The present invention places a liquid crystal box sample 5 in the optical path of the optical replication exposure device, and the light emitted by the laser light source 1 passes through the beam expansion collimation component 2 to obtain parallel light, and the parallel light hits the homogenizer template 3 to obtain a light field carrying the information of the homogenizer template 3. The light field carrying the information of the homogenizer template 3 is focused by the second focusing lens 4 and hits the liquid crystal box sample 5 for exposure, that is, the refractive light field of the microstructure on the homogenizer template 3 or the focused light field of the microlens is imaged on the liquid crystal box sample 5, and the light field has a light and dark distribution based on the information of the homogenizer template 3 in space, which can make the photosensitive prepolymer polymerize according to the distribution of the light and dark areas of the light beam, and then separate from the liquid crystal phase, and obtain a polymer dispersed liquid crystal target microstructure array in which the liquid crystal and the polymer are distributed in the micro-nano scale space, so as to realize the proportional replication or scaling of the existing homogenizer template 3. The homogenizer template 3 needs to be based on a refractive microstructure or a microlens array, and its diffusion angle and diffusion shape can be arbitrarily selected. The preparation method of the present invention is suitable for all homogenizer templates based on microstructures or microlens arrays, and has universal applicability. The selection of the second focusing lens 4 depends on the required imaging size and the resolution of the replication. The optical replication exposure device based on laser beam expansion, collimation and focusing can realize the replication of all light homogenizing sheet templates based on microstructures or microlens arrays.

[0044] The optical replication preparation method of the light homogenizer of the present invention can be based on a simple optical replication exposure device, and the replication of the existing light homogenizer template based on the microstructure or microlens array can be achieved through a single exposure. It has the advantages of simple steps, simple equipment, low cost, and mass production. Batch replication can be achieved with only one light homogenizer template, and it can replace complex micro-nano processing process flows.

[0045] In addition to being able to perform proportional replication of the microstructure in the homogenizer template, the present invention can also achieve the replication ratio, that is, control of the size of the microstructure in the homogenizer template by finely adjusting the different positions of the liquid crystal box sample in the light path of the optical replication exposure device to produce different replication effects, such as different diffusion shapes and diffusion angles, to achieve size customization of the polymer dispersed liquid crystal homogenizer, and then obtain micron-level and submicron-level homogenizers, whose micro-nano structure size can reach the micron level to the hundred nanometer level, with high resolution characteristics.

[0046] Preferably, in step S1, the cleaned glass substrates are assembled into a liquid crystal box. Specifically, two cleaned glass substrates can be assembled into a liquid crystal box with a certain thickness. The liquid crystal box can be packaged after step S3 is completed.

[0047] Preferably, in step S2, the mass proportion of liquid crystal in the mixture is 20%-80%, and the liquid crystal in the present invention can be a nematic liquid crystal, including but not limited to E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal. The photosensitive prepolymer includes an acrylate monomer and a photoinitiator, wherein the mass proportion of the acrylate monomer in the photosensitive prepolymer is 20%-80%, and the mass proportion of the photoinitiator in the photosensitive prepolymer is 1%-10%.

[0048] Under the action of exposure, the photosensitive prepolymer at the position where the light is irradiated is polymerized, the concentration of the photosensitive prepolymer decreases, and the unpolymerized photosensitive prepolymer that is not irradiated by the light can diffuse from high concentration to low concentration, thereby realizing the separation of the liquid crystal phase and the polymer phase.

[0049] The mass proportion of liquid crystal and photosensitive prepolymer in the mixture can directly affect the size of target liquid crystal droplets and polymer microstructures formed by phase separation of liquid crystal and prepolymer during exposure polymerization, thereby affecting the scattering state and resolution of the replicated uniform light sheet product.

[0050] Further preferably, the acrylate monomer can be dipentaerythritol penta- / hexylacrylate (DPPHA), pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate (PET(etra)A) and tri(propylene glycol) diacrylate (TPGDA), and the photoinitiator can be Bengal rose (RB), methyl blue or 2,2-dimethoxy-2-phenylacetophenone.

[0051] Further preferably, in addition to the acrylate monomer and the photoinitiator, a crosslinker and a coinitiator may be added to the photosensitive prepolymer. The crosslinker may be N-vinyl pyrrolidone (NVP), and its mass proportion in the photosensitive prepolymer is 20%-80%. The coinitiator may be N-phenylglycine (NPG) or p-toluenesulfonic acid, and its mass proportion in the photosensitive prepolymer is 0.5%-5%.

[0052] As a preference, in addition to the system consisting of acrylate monomers + photoinitiators, the photosensitive prepolymer in the above step S2 can also be a photocurable adhesive, and the selected photocurable adhesive includes but is not limited to NOA65 and NOA61.

[0053] In addition, in the above step S2, a surfactant or high refractive index particles may be added to the mixture. The above surfactant may be octanoic acid, and the above high refractive index particles may be titanium dioxide nanoparticles, etc. The surfactant is used to enhance the phase separation effect of the photosensitive prepolymer and the liquid crystal, and the high refractive index particles are used to enhance the scattering state of the light homogenizer.

[0054] Preferably, in step S2, the prepared mixture of liquid crystal and photosensitive prepolymer needs to be poured into the prepared liquid crystal box at a temperature higher than the clearing point of the liquid crystal.

[0055] It should be noted that after the mixture of liquid crystal and photosensitive prepolymer is poured into the prepared liquid crystal box, the liquid crystal box sample is placed in a photocopy exposure device for exposure after the mixture returns to room temperature.

[0056] Preferably, in the above step S3, the laser light source 1 can be ultraviolet light with a wavelength of 365nm, visible light with a wavelength of 488nm, 532nm or 633nm, or near-infrared light with a wavelength of 850nm, depending on the response wavelength of the photosensitive prepolymer material, that is, the corresponding wavelength is selected according to the selected photoinitiator. The beam expansion and collimation component 2 includes a first focusing lens 21, a pinhole filter 22 and a collimating lens 23. The optical copy exposure device of the present invention is based on the lens imaging principle. The light emitted by the laser light source 1 passes through the first focusing lens 21, the pinhole filter 22 and the collimating lens 23 in sequence to form parallel light. Figure 2 As shown, the first focusing lens 21 and the collimating lens 23 can be convex lenses. The selection of the beam expanding and collimating assembly 2, for example, the focal length of the first focusing lens 21 and the collimating lens 23, depends on the size and replication range of the light homogenizing sheet template to be replicated.

[0057] Preferably, in step S3, the exposure light intensity is 1 mW / cm 2 -100mW / cm 2 , more preferably 5mW / cm 2 -25mW / cm 2The exposure time is 30s-30min, and more preferably 2min-10min.

[0058] like Figure 3 As shown, in step S3, before placing the liquid crystal box sample 5 in the light path of the light copy exposure device, the placement position of the liquid crystal box sample 5 in the light path of the light copy exposure device can be confirmed by the objective lens and the CCD camera 6 to achieve the size customization of the polymer dispersed liquid crystal homogenizer, and the objective lens is preferably a high-power objective lens. Specifically, the light field carrying the homogenizer template information is imaged by the objective lens and the CCD camera to confirm the placement position of the liquid crystal box sample in the light path, so that the prepared homogenizer produces the expected resolution and homogenization effect. Specifically, the objective lens can be set on the CCD camera 6, and the objective lens is located on the side of the CCD camera 6 facing the second focusing lens 4, and the objective lens and the CCD camera 6 form a position detection component.

[0059] In addition, after obtaining the polymer dispersed liquid crystal light homogenizing sheet, the liquid crystal therein can be washed away, leaving the light homogenizing sheet composed of the polymer and having a microstructure.

[0060] In step S3, after the exposure treatment is completed, a polymer dispersed liquid crystal homogenizer is obtained. In order to ensure that the photosensitive prepolymer is completely cured, the polymer dispersed liquid crystal homogenizer can be further cured by a uniform light spot to ensure that the photosensitive prepolymer is completely polymerized and avoid washing away the unpolymerized photosensitive prepolymer during the cleaning process of the liquid crystal.

[0061] The present invention uses polymer dispersed liquid crystal as the material of the homogenizer microstructure, and based on laser light source exposure, the information of the existing homogenizer template is copied into the polymer dispersed liquid crystal by the method of optical replication. On the one hand, by designing the homogenizer template, the target scattering effect can be copied to the polymer dispersed liquid crystal homogenizer. On the other hand, by adjusting the optical replication optical path, the same homogenizer template can also produce different controllable replication effects. On the basis of proportional replication of the homogenizer template, the microstructure size of the homogenizer template can also be scaled to achieve customized homogenization effect and higher resolution.

[0062] Specifically, the placement position of the liquid crystal box sample in the optical path is crucial, and the specific position of the liquid crystal box sample needs to be adjusted according to the influence of the focal length range of the microlens array of the light homogenizer template and the resolution of the microstructure to be replicated. If the light homogenizer template is a micro-concave lens array with a focal length in the micrometer range, in order to achieve replication with a higher resolution than the light homogenizer template, the light exposed on the liquid crystal box sample needs to be focused light rather than divergent light, that is, the image formed on the liquid crystal box sample 5 by the second focusing lens 4 needs to be the focused light spot of the light homogenizer template 3, then the range in which the liquid crystal box sample 5 can be placed is generally also in the micrometer range, which is also related to the focal length of the second focusing lens 4 and its relative position to the light homogenizer template 3.

[0063] The polymer dispersed liquid crystal homogenizer of the present invention can achieve customized size, and the customization of microstructure arrays of different sizes can achieve different diffusion effects, such as different diffusion angles and diffusion shapes, to achieve specific light beam diffusion shapes and diffusion angles. The size of the microstructure is controlled by the exposure light path, and the diffusion shapes include isotropic such as circular light spots, and anisotropic such as rectangular light spots. The diffusion angle and diffusion shape can be achieved by designing the homogenizer template, and the diffusion effect of the homogenizer, including the diffusion angle and diffusion shape, as well as the size and resolution of the homogenizer can be achieved by regulating the exposure light path.

[0064] In order to further clarify the scheme of the present invention and its technical advancement, the following is a description in conjunction with specific embodiments and technical effects.

[0065] Example 1

[0066] This embodiment provides a method for preparing a light-homogenizing sheet by optical replication, comprising the following steps:

[0067] S1: First, two glass substrates with a size of 2 cm×2 cm are taken, and the two glass substrates are ultrasonically cleaned in acetone and isopropanol solutions in turn. After cleaning, the glass substrates are assembled into a liquid crystal box, and the thickness of the liquid crystal box is controlled by 20 μm microspheres.

[0068] S2: Prepare a mixture of liquid crystal and photosensitive prepolymer: Mix the liquid crystal and the photosensitive prepolymer and stir them to obtain a mixture, and pour the mixture into the liquid crystal box prepared in step S1 at 70°C by capillary action to obtain a liquid crystal box sample. In terms of mass fraction, the photosensitive prepolymer in this example includes 62% monomer TMPTA, 25% cross-linking agent NVP, 2% photoinitiator RB, 1% coinitiator NPG, and 10% octanoic acid. The liquid crystal material in this embodiment is E7 liquid crystal, and the mass ratio of photosensitive prepolymer to liquid crystal is 65:35.

[0069] S3: After the mixture in the liquid crystal box sample returns to room temperature, the liquid crystal box sample is fixed in the light path of the optical replication exposure device for exposure treatment to obtain a polymer dispersed liquid crystal homogenizer. In the optical replication exposure device of this embodiment, the laser light source is a 488nm argon ion laser, the homogenizer template is a commercial homogenizer, which can produce anisotropic rectangular diffused light spots, the second focusing lens uses a 20× objective lens, and the liquid crystal box sample is placed at a distance of 7.2mm from the objective lens. The exposure light intensity at the position of the liquid crystal box sample is 10mW / cm 2 , the exposure time is 5min.

[0070] The microscopic image of the polymer dispersed liquid crystal homogenizer obtained after the exposure process is as follows: Figure 4 As shown in a, through Figure 4It can be seen that the polymer dispersed liquid crystal light homogenizer prepared in this embodiment shows an anisotropic microstructure array. The diffusion effect of the polymer dispersed liquid crystal light homogenizer prepared in this embodiment on the laser spot was tested by a 633nm helium-neon laser at room temperature, and the result was Figure 4 b. If Figure 4 As shown in b, the polymer dispersed liquid crystal homogenizer prepared in this embodiment shows anisotropic rectangular scattered light spots. Therefore, this embodiment proves the feasibility of replicating the homogenizer using the optical replication preparation method of the present invention and designing the diffusion effect of the homogenizer.

[0071] Example 2

[0072] This embodiment provides a method for preparing a light-homogenizing sheet by optical replication, comprising the following steps:

[0073] S1: First, two glass substrates with a size of 2 cm×2 cm are taken, and the two glass substrates are ultrasonically cleaned in acetone and isopropanol solutions in turn. After cleaning, the glass substrates are assembled into a liquid crystal box, and the thickness of the liquid crystal box is controlled by 20 μm microspheres.

[0074] S2: Prepare a mixture of liquid crystal and photosensitive prepolymer: Mix the liquid crystal and the photosensitive prepolymer and stir them to obtain a mixture, and pour the mixture into the liquid crystal box prepared in step S1 at 70°C by capillary action to obtain a liquid crystal box sample. In terms of mass fraction, the photosensitive prepolymer in this example includes 62% monomer TMPTA, 25% cross-linking agent NVP, 2% photoinitiator RB, 1% coinitiator NPG, and 10% octanoic acid. The liquid crystal material in this embodiment is E7 liquid crystal, and the mass ratio of photosensitive prepolymer to liquid crystal is 65:35.

[0075] S3: After the mixture in the liquid crystal box sample returns to room temperature, the liquid crystal box sample is fixed in the light path of the optical replication exposure device for exposure treatment to obtain a polymer dispersed liquid crystal homogenizer. In the optical replication exposure device of this embodiment, the laser light source is a 488nm argon ion laser, and the homogenizer template is the same commercial homogenizer used in Example 1, which can produce anisotropic rectangular diffuse light spots. The second focusing lens uses a 20× objective lens, and the liquid crystal box sample is placed at a distance of 6.5mm from the objective lens. The exposure light intensity at the position of the liquid crystal box sample is 10mW / cm 2 , the exposure time is 5min.

[0076] The microscopic image of the polymer dispersed liquid crystal homogenizer obtained after the exposure process is as follows: Figure 5 As shown in a, through Figure 5It can be seen that the polymer dispersed liquid crystal light homogenizer prepared in this embodiment shows an isotropic microstructure array. The diffusion effect of the polymer dispersed liquid crystal light homogenizer prepared in this embodiment on the laser spot was tested at room temperature using a 633nm helium-neon laser, and the result was Figure 5 b. If Figure 5 As shown in Figure b, the polymer dispersed liquid crystal homogenizer prepared in this embodiment shows an isotropic circular scattered light spot. Therefore, this embodiment proves the feasibility of using the optical replication preparation method of the present invention to replicate the homogenizer and design the diffusion effect of the homogenizer. Figure 4 a and Figure 5 a, and Figure 4 b and Figure 5 From the comparison of Fig. 1 and Fig. 2 , it can be seen that when the liquid crystal box sample is placed at different positions in the light path of the optical replication exposure device, it can directly affect the array morphology in the prepared uniform light sheet, and further affect its diffusion effect.

[0077] Example 3

[0078] This embodiment provides a method for preparing a light-homogenizing sheet by optical replication, comprising the following steps:

[0079] S1: First, two glass substrates with a size of 2 cm×2 cm are taken, and the two glass substrates are ultrasonically cleaned in acetone and isopropanol solutions in turn. After cleaning, the glass substrates are assembled into a liquid crystal box, and the thickness of the liquid crystal box is controlled by 20 μm microspheres.

[0080] S2: Prepare a mixture of liquid crystal and photosensitive prepolymer: Mix the liquid crystal and the photosensitive prepolymer and stir them to obtain a mixture, and pour the mixture into the liquid crystal box prepared in step S1 at 70°C by capillary action to obtain a liquid crystal box sample. In terms of mass fraction, the photosensitive prepolymer in this example is UV curing glue NOA65. The liquid crystal material in this embodiment is E7 liquid crystal, and the mass ratio of the photosensitive prepolymer to the liquid crystal is 80:20.

[0081] S3: After the mixture in the liquid crystal box sample returns to room temperature, the liquid crystal box sample is fixed in the light path of the optical replication exposure device for exposure treatment to obtain a polymer dispersed liquid crystal homogenizer. In the optical replication exposure device of this embodiment, the laser light source is a 365nm argon ion laser, and the homogenizer template is the same commercial homogenizer used in Example 1, which can produce anisotropic rectangular diffuse light spots. The second focusing lens uses a 20× objective lens, and the liquid crystal box sample is placed at a distance of 7.2mm from the objective lens. The exposure light intensity at the position of the liquid crystal box sample is 10mW / cm 2 , the exposure time is 5min.

[0082] It has been verified that the polymer dispersed liquid crystal light homogenizer obtained after the exposure process in this embodiment has an anisotropic microstructure array and exhibits an anisotropic scattering effect on the incident laser.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a light-homogenizing sheet by optical replication, characterized in that: The steps include: S1: preparing a liquid crystal cell; S2: mixing the liquid crystal and the photosensitive prepolymer to obtain a mixture, and pouring the mixture into a liquid crystal box to obtain a liquid crystal box sample (5); S3: placing a liquid crystal box sample (5) in the light path of a light copying exposure device, the light copying exposure device comprising a laser light source (1), a beam expander and collimator assembly (2), a light homogenizer template (3) and a second focusing lens (4) arranged in sequence, the light emitted by the laser light source (1) passes through the beam expander and collimator assembly (2) to form parallel light, the parallel light hits the light homogenizer template (3), and a light field carrying light homogenizer template information is obtained, the liquid crystal box sample (5) is placed on the other side of the second focusing lens (4), the light field carrying light homogenizer template information is focused by the second focusing lens (4) and hits the liquid crystal box sample (5) for exposure, so that the photosensitive prepolymer is polymerized according to the light homogenizer template information carried by the light field, and then separated from the liquid crystal phase, to obtain a polymer dispersed liquid crystal homogenizer.

2. The method for preparing the light-diffusion sheet by optical replication according to claim 1, characterized in that: In step S1, the cleaned glass substrates are assembled into a liquid crystal cell.

3. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S2, the mass proportion of liquid crystal in the mixture is 20%-80%, the photosensitive prepolymer includes acrylate monomer and photoinitiator, the mass proportion of acrylate monomer in the photosensitive prepolymer is 20%-80%, and the mass proportion of photoinitiator in the photosensitive prepolymer is 1%-10%.

4. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S2, the liquid crystal is a nematic liquid crystal, including E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal.

5. The method for preparing the light-diffusion sheet by optical replication according to claim 3, characterized in that: In step S2, the acrylate monomer is dipentaerythritol penta- / hexyl-acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate or tri(propylene glycol) diacrylate, and the photoinitiator is Bengal rose red, methyl blue or 2,2-dimethoxy-2-phenylacetophenone.

6. The method for preparing the light-diffusion sheet by optical replication according to claim 3, characterized in that: In step S2, the photosensitive prepolymer also includes a crosslinker and a coinitiator. The crosslinker is N-vinyl pyrrolidone, which accounts for 20%-80% by weight in the photosensitive prepolymer; the coinitiator is N-phenylglycine or p-toluenesulfonic acid, which accounts for 0.5%-5% by weight in the photosensitive prepolymer.

7. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S2, the photosensitive prepolymer is a photocurable adhesive, and the photocurable adhesive is NOA65 or NOA61; In step S2, a surfactant and high refractive index particles are also added to the mixture; The surfactant is octanoic acid, and the high refractive index particles are titanium dioxide nanoparticles.

8. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S3, the wavelength of the laser light source (1) is 365 nm, 488 nm, 532 nm, 633 nm or 850 nm.

9. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S3, the exposure light intensity is 1mW / cm 2 -100mW / cm 2 The exposure time is 30s-30min.

10. The method for preparing the light-homogenizing sheet by optical replication according to claim 1, characterized in that: In step S3, before placing the liquid crystal cell sample (5) in the optical path of the optical duplication exposure device, firstly confirm the placement position of the liquid crystal cell sample (5) in the optical path of the optical duplication exposure device through an objective lens and a CCD camera (6); The objective lens is arranged on the CCD camera (6) and is located on a side facing the second focusing lens (4); The beam expansion and collimation assembly (2) comprises a first focusing lens (21), a pinhole filter (22) and a collimating lens (23).

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