Preparation method of anisotropic scattering sheet

Abstract

The invention belongs to the field of optics, and relates to a preparation method of an anisotropic scattering sheet, which comprises the following steps: S1, preparing a mask plate; and S2, preparing the liquid crystal box. And S3, mixing the liquid crystal and the prepolymer, and filling the mixture into a liquid crystal box to obtain a liquid crystal box sample. S4, the liquid crystal box sample is placed on the temperature adjusting assembly, the mask plate is located between the liquid crystal box sample and the beam expanding and collimating assembly, light emitted by the light source forms parallel light through the beam expanding and collimating assembly, the parallel light penetrates through the light-transmitting area of the mask plate and is emitted to the liquid crystal box sample, prepolymer in the corresponding area is subjected to photopolymerization and is separated from the liquid crystal phase, and the anisotropic scattering sheet is obtained. The preparation method disclosed by the invention is simple and easy to implement, relatively low in requirement on a preparation environment, and capable of customizing a mask plate with an array pattern in a specified geometrical shape according to different requirements and polymerizing the prepolymer through exposure to obtain the corresponding anisotropic scattering sheet, so that the requirements of different application scenes are met.

Description

Technical Field

[0001] The invention relates to the technical field of optical engineering, and in particular to a method for preparing an anisotropic scattering sheet. Background Art

[0002] Optical scattering devices play an important role in beam shaping, backlighting, and optoelectronic display. For example, scattering sheets are widely used in large-size liquid crystal displays to provide backlight sources with high uniformity and large scattering angles. In particular, anisotropic scattering sheets with different scattering angles in different directions have been widely used in the field of naked-eye three-dimensional display. In this field, researchers can use the anisotropic properties of such scattering sheets to simulate a light field close to a real object in the horizontal direction.

[0003] The prior art describes various methods for manufacturing anisotropic scattering sheets.

[0004] The patent application with publication number CN1831569A describes a method for preparing anisotropic scattering sheets by stretching, in which transparent resin materials with different melting points are uniformly mixed, wherein the crystalline resin is used as a continuous phase and the non-crystalline resin is used as a dispersed phase. Subsequently, the composition is extruded and strongly stretched in the extrusion direction, and the resin sheet thus obtained contains uniformly dispersed micron-sized particles with anisotropic shapes and a refractive index different from that of the matrix.

[0005] Patent application with publication number CN103488035A records a method for preparing anisotropic scattering sheets by holographic exposure. This method uses holographic interference exposure technology to prepare anisotropic scattering sheets, wherein a cylindrical lens is placed on the object light path, and the reference light path is plane light. A holographic dry plate is used to record interference patterns. This method can record cylindrical lens array holograms in two directions by moving the position of the holographic dry plate and rotating the direction of the holographic dry plate.

[0006] In addition, some researchers have used photopolymerization-induced phase separation to prepare polymer dispersed liquid crystal scatterers. This method uses the fine stripe-shaped light intensity distribution generated by the original anisotropic scatterer to polymerize the material, thereby replicating a scatterer with similar functions.

[0007] However, the above-mentioned method of preparing anisotropic scattering sheets by stretching requires heavy machinery and a high temperature environment of 200°C, which makes the preparation difficult. The holographic exposure method requires the use of lasers with good coherence and ultra-low environmental disturbance conditions, and the preparation conditions are relatively high. The photopolymerization-induced phase separation method requires the existing anisotropic scattering sheet to be used as a template for replication, and can only replicate the characteristics of the existing anisotropic scattering sheet, making it difficult to achieve personalized customization.

[0008] Therefore, in order to overcome the shortcomings of the existing technology, it is urgent to provide a new method for preparing anisotropic scattering sheets to simplify the preparation conditions, reduce the difficulty of preparation and achieve personalized customization. Summary of the invention

[0009] 1. Technical issues to be resolved

[0010] In order to solve the problems of high difficulty in preparing anisotropic scattering sheets, high requirements on preparation conditions and difficulty in achieving personalized customization in the preparation methods of the anisotropic scattering sheets in the prior art, the present invention provides a preparation method for anisotropic scattering sheets.

[0011] (II) Technical solution

[0012] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0013] A method for preparing an anisotropic scattering sheet comprises the following steps:

[0014] S1: Prepare a mask with an array pattern of specified geometric shape;

[0015] S2: preparing a liquid crystal cell;

[0016] S3: mixing the liquid crystal and the prepolymer to obtain a mixture, and placing the mixture into a liquid crystal box to obtain a liquid crystal box sample;

[0017] S4: placing the liquid crystal box sample and the mask in an anisotropic scattering sheet preparation device, the anisotropic scattering sheet preparation device includes a light source, a beam expander and collimator assembly and a temperature adjustment assembly arranged in sequence, the liquid crystal box sample is placed on the temperature adjustment assembly, the mask is located between the liquid crystal box sample and the beam expander and collimator assembly, the light emitted by the light source passes through the beam expander and collimator assembly to form parallel light, the parallel light passes through the light-transmitting area of ​​the mask and hits the liquid crystal box sample for exposure, so that the prepolymer in the corresponding area undergoes photopolymerization and then separates from the liquid crystal phase to obtain an anisotropic scattering sheet.

[0018] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S1, the specified geometric array pattern on the mask is a rectangular array pattern, a hexagonal array pattern, a trapezoidal array pattern or a triangular array pattern;

[0019] The specified geometric shape array pattern includes a plurality of geometric shapes, and the geometric shapes are rectangles, hexagons, trapezoids or triangles;

[0020] The geometric shapes have a specified distribution pattern and a specified size.

[0021] In the method for preparing the anisotropic scattering sheet as described above, preferably, the specified geometric shape array pattern on the mask is a rectangular array pattern, the geometric shape is a rectangle, and the length l of the rectangle in the horizontal direction, the width w of the rectangle in the vertical direction, the spacing gx between adjacent rectangles in the horizontal direction, and the spacing gy between adjacent rectangles in the vertical direction are in the range of 1-50μm.

[0022] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S1, it is assumed that a rectangular scattering spot is generated after the parallel light beam is incident on the designated anisotropic scattering sheet, and the length of the rectangular scattering spot in the horizontal direction is a and the width in the vertical direction is b;

[0023] In the rectangular array pattern on the mask, the average length of the multiple rectangles in the horizontal direction is l', and the average width of the multiple rectangles in the vertical direction is w'. l' and w' need to satisfy the following relationship:

[0024] l′ / w′=b / a.

[0025] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S2, the cleaned transparent substrate is assembled into a liquid crystal box;

[0026] The transparent substrate is a glass substrate or a plastic substrate, and a conductive layer is also arranged on the transparent substrate.

[0027] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S3, the mass proportion of the liquid crystal in the mixture is 20%-80%, the liquid crystal is a nematic phase liquid crystal, including E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal; the prepolymer includes a photocurable resin monomer and a photoinitiator, the mass proportion of the photocurable resin monomer in the prepolymer is 20%-80%, and the mass proportion of the photoinitiator in the prepolymer is 0.01%-10%.

[0028] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S3, the photocurable resin monomer is unsaturated polyester, epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, pure acrylic resin, epoxy resin or silicone oligomer; and the photoinitiator is a benzoin ether photoinitiator, a benzophenone photoinitiator or an acetophenone photoinitiator.

[0029] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S3, the prepolymer further includes a reactive diluent, and the reactive diluent is an acrylate reactive diluent, a vinyl reactive diluent, a vinyl ether reactive diluent or an epoxy reactive diluent, and its mass proportion in the prepolymer is 1%-20%.

[0030] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S4, the temperature adjustment component adjusts the temperature of the liquid crystal box sample to 20° C.-80° C., and the exposure light intensity is 1 mW / cm 2 -100mW / cm 2 The exposure time is 5min-30min.

[0031] In the method for preparing the anisotropic scattering sheet as described above, preferably, in step S4, the light source is an ultraviolet light source, and the ultraviolet light source is a mercury lamp or an ultraviolet light emitting diode.

[0032] (III) Beneficial effects

[0033] The preparation method of the present invention prepares a mask with an array pattern of specified geometric shapes, so that the light emitted by the light source passes through the light-transmitting area of ​​the mask and hits the liquid crystal box sample for patterned exposure, thereby causing the prepolymer in the corresponding area of ​​the liquid crystal box sample to be photopolymerized and separated from the liquid crystal phase, thereby obtaining an anisotropic scattering sheet with a desired structure.

[0034] The preparation method of the present invention is simple and easy to implement, does not require expensive equipment and materials, and has relatively low requirements on the preparation environment, which can reduce production costs and achieve large-scale production. The present invention can also achieve customized production of anisotropic scattering sheets, and can flexibly customize the aspect ratio of the scattering spots of the anisotropic scattering sheet as needed by adjusting the pattern size and ratio on the mask to meet the needs of different application scenarios.

[0035] The preparation method of the present invention can ensure uniform light intensity distribution of the scattering spots of the prepared anisotropic scattering sheet by precisely controlling the design of the mask and the exposure process, thereby providing a better visual effect. In addition, the anisotropic scattering sheet prepared by the present invention also has liquid crystal, and the electric field response characteristics of the liquid crystal can be used to dynamically adjust the scattering degree of the anisotropic scattering sheet, so that the scattering sheet can adapt to different lighting environments and user needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a process flow chart of a method for preparing an anisotropic scattering sheet in the present invention;

[0037] Figure 2 A plan view of a mask having an asymmetric randomly distributed pattern in the present invention;

[0038] Figure 3 It is a schematic structural diagram of a device for preparing an anisotropic scattering sheet in the present invention;

[0039] Figure 4 This is a diagram of the internal structure of the anisotropic scattering sheet prepared by the present invention;

[0040] Figure 5A partial enlarged view of the mask used in Example 1;

[0041] Figure 6 This is a micrograph of the anisotropic scattering sheet prepared in Example 1;

[0042] Figure 7 A partial enlarged view of the mask used in Example 2;

[0043] Figure 8 This is a micrograph of the anisotropic scattering sheet prepared in Example 2.

[0044] [Description of Reference Numerals]

[0045] 1: light source; 2: mask; 3: liquid crystal box sample; 31: transparent substrate; 32: mixture; 321: polymer-rich region; 322: liquid crystal-rich region; 4: temperature adjustment component; 5: rectangle. DETAILED DESCRIPTION

[0046] 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.

[0047] like Figure 1 As shown, the present invention provides a method for preparing an anisotropic scattering sheet, comprising the following steps:

[0048] S1: Prepare a mask 2 with an array pattern of a specified geometric shape.

[0049] S2: Prepare a liquid crystal box.

[0050] S3: Mix the liquid crystal and the prepolymer to obtain a mixture 32, and load the mixture 32 into a liquid crystal box to obtain a liquid crystal box sample 3.

[0051] S4: Place the liquid crystal box sample 3 and the mask 2 in an anisotropic scattering film preparation device, which includes a light source 1, a beam expander and collimator assembly and a temperature adjustment assembly 4 arranged in sequence. The liquid crystal box sample 3 is placed on the temperature adjustment assembly 4, and the mask 2 is located between the liquid crystal box sample 3 and the beam expander and collimator assembly. The light emitted by the light source 1 passes through the beam expander and collimator assembly to form parallel light, and the parallel light passes through the light-transmitting area of ​​the mask 2 and hits the liquid crystal box sample 3 for exposure, so that the prepolymer in the corresponding area undergoes photopolymerization and then separates from the liquid crystal phase to obtain an anisotropic scattering film. In addition to the parallel light passing through the mask 2, another part of the parallel light is blocked by the specified geometric shape array pattern.

[0052] It should be noted that the above step S1 can be performed before step S2 and step S3, or after step S2 and step S3, as long as step S1 is completed before step S4.

[0053] In step S1, it is necessary to design and prepare a mask having a geometric array pattern of random size and random position. The mask in the present invention can be a quartz chrome plate, a glass chrome plate or a film mask, etc. It should be noted that the random numbers with random size and random position need to be selected in a specified range according to user needs in the actual preparation process of the scattering sheet, and are not completely arbitrary settings.

[0054] Preferably, in the above step S1, the specified geometric array pattern on the mask 2 can be a rectangular array pattern, a hexagonal array pattern, a trapezoidal array pattern or a triangular array pattern, etc. These array patterns can make the prepared scattering sheet show anisotropy.

[0055] Similarly, the above-mentioned specified geometric shape array pattern includes multiple geometric shapes, which can be rectangles, hexagons, trapezoids or triangles. In order to realize customized production of different anisotropic scattering sheets according to different needs, the above-mentioned geometric shapes should have specified distribution methods and specified sizes. The specific distribution method and size of the geometric shapes can be designed according to actual needs.

[0056] More preferably, if Figure 2 As shown, the specified geometric array pattern on the mask 2 is a rectangular array pattern, so the geometric shape is a rectangle, the length of rectangle 5 in the horizontal direction is recorded as l, the width of the rectangle in the vertical direction is recorded as w, the spacing between adjacent rectangles in the horizontal direction is recorded as gx, and the spacing between adjacent rectangles in the vertical direction is recorded as gy. The value ranges of the above l, w, gx and gy are all 1-50μm. Keeping the above parameters in the range of 1-50μm can ensure that the pattern on the mask can be effectively copied to the liquid crystal / polymer material and produce an ideal scattering effect. The random spacing gx and gy of the rectangle in the horizontal and vertical directions are set to reduce the regular diffraction points caused by periodicity.

[0057] In the present invention, parameters such as the length, width and spacing of the rectangular pattern on the mask can be designed according to the shape of the scattering spot of the desired scattering sheet.

[0058] Specifically, it is assumed that a parallel light beam generates a rectangular scattering spot after being incident on a specified anisotropic scattering sheet, and the length of the rectangular scattering spot in the horizontal direction is a, and the width in the vertical direction is b. It should be noted that the specified anisotropic scattering sheet is the anisotropic scattering sheet to be obtained, and the mask is designed and prepared according to the expected anisotropic scattering sheet. By adjusting the design of the mask, anisotropic scattering sheets with different scattering spot shapes (i.e., aspect ratios) can be prepared, which enables the present invention to meet the personalized needs of different users for the performance of the scattering sheet, and has great market potential.

[0059] In the rectangular array pattern on the mask 2, the average length of the multiple rectangles in the horizontal direction is recorded as l', and the average width of the multiple rectangles in the vertical direction is recorded as w'. l' and w' need to satisfy the following relationship:

[0060] l′ / w′=b / a.

[0061] According to the principle of multi-slit interference, when a beam of parallel light is incident on a rectangular grating, a series of diffraction lattices will be generated in two orthogonal directions. If the micrometer-level rectangular array in the grating is randomly distributed, a diffraction lattice randomly distributed in two directions will be generated. The randomness of the lattice helps to make the light intensity distribution on the diffraction pattern more uniform, thereby achieving an ideal scattering and homogenizing effect. Therefore, in order to achieve a better scattering and homogenizing effect, the ratio between the average length and the average width of the rectangle in the present invention is equal to the inverse of the aspect ratio of the scattering spot.

[0062] Preferably, in the above step S2, two cleaned transparent substrates 31 can be assembled into a liquid crystal box with a certain gap, preferably 5 μm to 50 μm, and the transparent substrate 31 can be a glass substrate or a plastic substrate, wherein the plastic substrate can be polyester, polystyrene, polyolefin, cellulose derivative, etc. A conductive layer is also plated on the transparent substrate 31, and the conductive layer can be indium tin oxide, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonic acid, etc. The liquid crystal box with a conductive layer is convenient for applying voltage to the anisotropic scattering sheet in the subsequent application process, changing the arrangement state of the liquid crystal molecules, thereby realizing dynamic regulation of the scattering degree, so that the scattering sheet has a wide range of application prospects in the display field, and the display effect can be dynamically adjusted as needed.

[0063] Preferably, in step S3, the mass proportion of liquid crystal in the mixture is 20%-80%. The liquid crystal in the present invention can be a nematic phase liquid crystal, including but not limited to E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal. The mass proportion of liquid crystal in the mixture will affect the phase separation effect of liquid crystal and polymer, and thus affect the scattering degree of the prepared anisotropic scattering sheet. The prepolymer includes a photocurable resin monomer and a photoinitiator, wherein the mass proportion of the photocurable resin monomer in the prepolymer is 20%-80%, and the mass proportion of the photoinitiator in the prepolymer is 0.01%-10%, and more preferably 0.03%-1%.

[0064] Further preferably, the above-mentioned photocurable resin monomer can be unsaturated polyester, epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, pure acrylic resin, epoxy resin or silicone oligomer, such as NOA65. The photoinitiator can be a benzoin ether photoinitiator, a benzophenone photoinitiator or an acetophenone photoinitiator.

[0065] Further preferably, in step S3, the prepolymer further includes a reactive diluent, which may be an acrylate reactive diluent, a vinyl reactive diluent, a vinyl ether reactive diluent or an epoxy reactive diluent, and its mass proportion in the prepolymer is 1%-20%. The reactive diluent can participate in the photocuring reaction and dissolve, dilute, and adjust the viscosity of the photocurable resin monomer.

[0066] Preferably, in the above step S4, the mixture of liquid crystal and prepolymer is poured into the liquid crystal box at a temperature higher than the clearing point of the liquid crystal. Figure 3 As shown, in the anisotropic scattering sheet preparation device, the light source 1 is preferably an ultraviolet light source, and the ultraviolet light source can be a mercury lamp or an ultraviolet light emitting diode, etc. In order to obtain uniform and collimated light, the light emitted by the light source 1 can be homogenized, and the light can be obtained by a beam expansion and collimation component ( Figure 3 (not shown in the figure) to expand and collimate the light emitted by the light source 1. Figure 3 As shown, the mask 2 can be placed above the liquid crystal cell sample 3, and generally the mask 2 is in direct contact with the transparent substrate 31 in the liquid crystal cell sample 3. If the distance between the mask 2 and the transparent substrate 31 is too large, the replication effect will be affected, resulting in pattern distortion.

[0067] During the exposure process, the temperature of the liquid crystal box sample and the intensity of exposure are key preparation parameters. Preferably, in step S4, the temperature adjustment component 4 can adjust the liquid crystal box sample 3 to 20°C-80°C. The temperature adjustment component 4 can specifically be a temperature control table. The light intensity of exposure is 1mW / cm 2 -100mW / cm 2 , preferably 10 mW / cm 2 -30mW / cm 2 . The exposure time is 5min-30min. Further preferably, during the exposure process, the temperature regulating component 4 is used to heat the temperature of the liquid crystal to a temperature higher than the clearing point of the liquid crystal. The temperature regulating component adjusts the temperature of the liquid crystal box sample to affect the phase separation effect of the liquid crystal and the polymer, thereby affecting the scattering degree of the prepared anisotropic scattering sheet. In addition, the light intensity of the exposure will affect the curing speed of the photocurable resin monomer. If the light intensity of the exposure is too high, the photocurable resin monomer will cure too quickly, which will cause the phase separation of the liquid crystal and the polymer to be too fast, the concentration of the liquid crystal in the polymer to be too high, and the contrast will not be obvious, affecting the scattering effect of the scattering sheet.

[0068] The internal structure of the adjustable anisotropic scattering sheet prepared by the present invention is as follows: Figure 4As shown, the prepared anisotropic scattering sheet is composed of a continuous phase mainly composed of polymer and a dispersed phase mainly composed of liquid crystal. In the light-transmitting area of ​​the mask 2, the light intensity is relatively strong, causing the photocurable resin monomer here to undergo photopolymerization reaction first to form a polymer. In this process, the photocurable resin monomer is gradually consumed, so the photocurable resin monomer molecule concentration in this area is reduced, while the liquid crystal molecule concentration is relatively high. In the light-shielding area of ​​the mask 2 (i.e., the area with a specified geometric array pattern), the light intensity is relatively weak, and the photocurable resin monomer does not undergo photopolymerization reaction, so the photocurable resin monomer molecule concentration in this area is relatively high, and the liquid crystal molecule concentration is relatively low. In order to maintain the balance of molecular concentration, the liquid crystal molecules diffuse from the high light intensity area to the low light intensity area, and the photocurable resin monomer molecules diffuse from the low light intensity area to the high light intensity area. As the photopolymerization reaction proceeds, a polymer-rich area 321 and a liquid crystal-rich area 322 are finally formed in the liquid crystal box. The polymer-rich area 321 and the liquid crystal-rich area 322 have different refractive indices, and their sizes and distributions are random, so they can cause light scattering.

[0069] In addition, the orientation of the liquid crystal molecules in the anisotropic scattering sheet prepared by the present invention can also be regulated by an electric field. When a high voltage is applied to the anisotropic scattering sheet, the liquid crystal molecules are driven by the electric field force to deflect along the direction of the electric field line, thereby changing their refractive index. As a result, the refractive index difference between the liquid crystal-rich region and the polymer-rich region becomes smaller, thereby reducing the degree of scattering. Preferably, the electrical signal can be a rectangular square wave with a frequency of 1 kHz and a voltage range of 5V-150V.

[0070] After the exposure treatment is completed, in order to ensure that the prepolymer is completely cured, the liquid crystal cell sample can be cooled and then exposed to light with an intensity of 10mW / cm 2 -50mW / cm 2 The light intensity was continued to be exposed for 5 min to ensure that the prepolymer was fully polymerized.

[0071] By adjusting the irradiation intensity of the light source 1 and the temperature of the temperature regulating component, the present invention can control the polymerization degree and scattering effect of the liquid crystal / polymer material, thereby preparing an anisotropic scattering sheet with desired scattering characteristics.

[0072] 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.

[0073] Example 1

[0074] This embodiment provides a method for preparing an anisotropic scattering sheet, comprising the following steps:

[0075] S1: Take two glass substrates with a size of 5cm×5cm, of which the thickness of the upper glass substrate is 0.2mm and the thickness of the lower glass substrate is 1.1mm. Put the two glass substrates into an ultrasonic cleaning tank, and ultrasonically clean them in acetone, isopropanol and ethanol solutions for 20 minutes respectively. After cleaning, use an air gun to blow dry and dry them for use. Assemble the cleaned glass substrates into a liquid crystal box, and the thickness of the liquid crystal box is controlled at 10μm by a plastic gasket. The surface of the glass substrate is plated with an indium tin oxide conductive layer.

[0076] S2: Mix the liquid crystal and the prepolymer to obtain a mixture, and pour the mixture into the liquid crystal box prepared in step S1 at 70° C. on a temperature control table by capillary force to obtain a liquid crystal box sample. The liquid crystal in this embodiment is E7 liquid crystal, the prepolymer is photocurable material NOA65 (a type of photocurable resin monomer), and the mass ratio of liquid crystal to prepolymer is 50:50.

[0077] S3: Place the designed glass chrome plate mask on top of the liquid crystal box, with the chrome-plated side of the mask facing downward. Figure 5 As shown, the designated geometric shape array pattern on the mask is a rectangular array pattern, and the parameters of the mask are: the length l of a single rectangle is 6-21μm, the width w is 5-14μm, the spacing gx between adjacent rectangles in the horizontal direction is 6-10μm, and the spacing gy between adjacent rectangles in the vertical direction is 1-13μm. The length l, width w, spacing gx and spacing gy of the rectangle are randomly distributed within the above-mentioned limited range. In this embodiment, it is expected that a rectangular scattering spot will be generated after the parallel light beam in step S1 is incident on the designated anisotropic scattering sheet, and the length-to-width ratio of the rectangular scattering spot is a / b=2 / 3. Therefore, in the rectangular array pattern on the mask of this step, the ratio of the average length l' of multiple rectangles in the horizontal direction to the average width w' of multiple rectangles in the vertical direction is l' / w'=b / a=3:2.

[0078] S4: The temperature of the liquid crystal box sample is controlled at 50°C by a temperature control table, and then UV exposure is performed for 20 minutes. In the anisotropic scattering sheet preparation device of this embodiment, the light source is a UV light emitting diode with a central wavelength of 365nm, and the light intensity is controlled at 15mW / cm during the exposure process. 2 After the exposure, the liquid crystal box sample was slowly cooled to room temperature and then exposed to UV light for 5 minutes, with the light intensity controlled at 50mW / cm 2 , and an anisotropic scattering sheet is obtained.

[0079] The microscopic image of the anisotropic scattering sheet prepared in this example under orthogonal polarization is as follows: Figure 6 As shown, through Figure 6It can be seen that the scattering sheet contains a dispersed phase mainly composed of liquid crystal droplets and a continuous phase mainly composed of polymers. The anisotropic pattern on the mask of this embodiment is copied to the scattering sheet, so that the scattering sheet can produce anisotropic light scattering.

[0080] The substrate of this embodiment is a conductive substrate, and the scattering degree of the scattering sheet can be adjusted by applying voltage during use. Specifically, a rectangular square wave electrical signal with a frequency of 1 kHz and a voltage of 100 V is applied to the upper and lower substrates of the liquid crystal box prepared in this embodiment, and it is observed that the scattering degree of the scattering sheet is greatly reduced compared with that when no voltage is applied, and the whole sheet is in a state close to being transparent, and the intensity of the scattering spots is greatly weakened.

[0081] Example 2

[0082] This embodiment provides a method for preparing an anisotropic scattering sheet, comprising the following steps:

[0083] S1: Take two glass substrates with a size of 5cm×5cm, of which the thickness of the upper glass substrate is 0.2mm and the thickness of the lower glass substrate is 1.1mm. Put the two glass substrates into an ultrasonic cleaning tank, and ultrasonically clean them in acetone, isopropanol and ethanol solutions for 20 minutes respectively. After cleaning, use an air gun to blow dry and dry them for use. Assemble the cleaned glass substrates into a liquid crystal box, and the thickness of the liquid crystal box is controlled at 10μm by a plastic gasket. The surface of the glass substrate is plated with an indium tin oxide conductive layer.

[0084] S2: Mix the liquid crystal and the prepolymer to obtain a mixture, and pour the mixture into the liquid crystal box prepared in step S1 at 70°C on a temperature control table by capillary force to obtain a liquid crystal box sample. The liquid crystal in this embodiment is E7 liquid crystal, and the prepolymer is epoxy acrylate, benzoin ether photoinitiator, and acrylate reactive diluent, wherein the epoxy acrylate, benzoin ether photoinitiator, and acrylate reactive diluent account for 75%, 5%, and 20% of the prepolymer, respectively, and the mass ratio of the liquid crystal to the prepolymer is 30:70.

[0085] S3: Place the designed glass chrome plate mask on top of the liquid crystal box, with the chrome-plated side of the mask facing downward. Figure 7As shown, the designated geometric shape array pattern on the mask is a rectangular array pattern, and the parameters of the mask are: the length l of a single rectangle is 11-19μm, the width w is 9-11μm, the spacing gx between adjacent rectangles in the horizontal direction is 6-8μm, and the spacing gy between adjacent rectangles in the vertical direction is 3-8μm. The length l, width w, spacing gx and spacing gy of the rectangle are randomly distributed within the above-mentioned limited range. In this embodiment, it is expected that a rectangular scattering spot will be generated after the parallel light beam in step S1 is incident on the designated anisotropic scattering sheet, and the length-to-width ratio of the rectangular scattering spot is a / b=2 / 3. Therefore, in the rectangular array pattern on the mask of this step, the ratio of the average length l' of multiple rectangles in the horizontal direction to the average width w' of multiple rectangles in the vertical direction is l' / w'=b / a=3:2.

[0086] S4: The temperature of the liquid crystal box sample is controlled at 50°C by a temperature control table, and then UV exposure is performed for 20 minutes. In the anisotropic scattering sheet preparation device of this embodiment, the light source is a UV light emitting diode with a central wavelength of 365nm, and the light intensity is controlled at 30mW / cm during the exposure process. 2 After the exposure, the liquid crystal box sample was slowly cooled to room temperature and then exposed to UV light for 5 minutes, with the light intensity controlled at 50mW / cm 2 , and an anisotropic scattering sheet is obtained.

[0087] The microscopic image of the anisotropic scattering sheet prepared in this example under orthogonal polarization is as follows: Figure 8 As shown, through Figure 8 It can be seen that the scattering sheet contains a dispersed phase mainly composed of liquid crystal droplets and a continuous phase mainly composed of polymers. The anisotropic pattern on the mask of this embodiment is copied to the scattering sheet, so that the scattering sheet can produce anisotropic light scattering.

[0088] A rectangular square wave electrical signal with a frequency of 1 kHz and a voltage of 40 V was applied to the upper and lower substrates of the liquid crystal box prepared in this embodiment. It was observed that the scattering degree of the scattering plate was lower than that without applying voltage, and the whole was translucent, and the intensity of the scattering spot was weakened.

[0089] 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 an anisotropic scattering sheet, characterized in that: The steps include: S1: preparing a mask with an array pattern of a specified geometric shape (2); S2: preparing a liquid crystal cell; S3: mixing the liquid crystal and the prepolymer to obtain a mixture (32), and placing the mixture (32) into a liquid crystal box to obtain a liquid crystal box sample (3); S4: placing the liquid crystal box sample (3) and the mask (2) in an anisotropic scattering sheet preparation device, the anisotropic scattering sheet preparation device comprising a light source (1), a beam expanding and collimating component and a temperature regulating component (4) arranged in sequence, the liquid crystal box sample (3) being placed on the temperature regulating component (4), the mask (2) being located between the liquid crystal box sample (3) and the beam expanding and collimating component, the light emitted by the light source (1) passing through the beam expanding and collimating component forming parallel light, the parallel light passing through the light-transmitting area of ​​the mask (2) hitting the liquid crystal box sample (3) for exposure, causing the prepolymer in the corresponding area to be photopolymerized and then separated from the liquid crystal phase, thereby obtaining an anisotropic scattering sheet.

2. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S1, the specified geometric array pattern on the mask (2) is a rectangular array pattern, a hexagonal array pattern, a trapezoidal array pattern or a triangular array pattern; The specified geometric shape array pattern includes a plurality of geometric shapes, and the geometric shapes are rectangles, hexagons, trapezoids or triangles; The geometric shapes have a specified distribution pattern and a specified size.

3. The method for preparing an anisotropic scattering sheet according to claim 2, characterized in that: The specified geometric shape array pattern on the mask (2) is a rectangular array pattern, wherein the geometric shape is a rectangle, and the length l of the rectangle in the horizontal direction, the width w of the rectangle in the vertical direction, the spacing gx between adjacent rectangles in the horizontal direction, and the spacing gy between adjacent rectangles in the vertical direction are in the range of 1-50 μm.

4. The method for preparing an anisotropic scattering sheet according to claim 3, characterized in that: In step S1, it is assumed that a parallel light beam generates a rectangular scattering spot after being incident on a designated anisotropic scattering sheet, and the length of the rectangular scattering spot in the horizontal direction is a and the width in the vertical direction is b; In the rectangular array pattern on the mask (2), the average length of the multiple rectangles in the horizontal direction is l', and the average width of the multiple rectangles in the vertical direction is w'. l' and w' need to satisfy the following relationship: l′ / w′=b / a.

5. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S2, the cleaned transparent substrate (31) is assembled into a liquid crystal cell; The transparent substrate (31) is a glass substrate or a plastic substrate, and a conductive layer is also provided on the transparent substrate (31).

6. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S3, the mass proportion of liquid crystal in the mixture is 20%-80%, and the liquid crystal is a nematic phase liquid crystal, including E7 liquid crystal, 5CB liquid crystal and 8CB liquid crystal; the prepolymer includes a photocurable resin monomer and a photoinitiator, the mass proportion of the photocurable resin monomer in the prepolymer is 20%-80%, and the mass proportion of the photoinitiator in the prepolymer is 0.01%-10%.

7. The method for preparing an anisotropic scattering sheet according to claim 6, characterized in that: In step S3, the photocurable resin monomer is unsaturated polyester, epoxy acrylate, polyurethane acrylate, polyester acrylate, polyether acrylate, pure acrylic resin, epoxy resin or silicone oligomer; the photoinitiator is a benzoin ether photoinitiator, a benzophenone photoinitiator or an acetophenone photoinitiator.

8. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S3, the prepolymer further includes a reactive diluent, which is an acrylate reactive diluent, a vinyl reactive diluent, a vinyl ether reactive diluent or an epoxy reactive diluent, and its mass proportion in the prepolymer is 1%-20%.

9. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S4, during the exposure process, the temperature adjustment component (4) adjusts the temperature of the liquid crystal box sample (3) to 20°C-80°C, and the exposure light intensity is 1mW / cm 2 -100mW / cm 2 The exposure time is 5min-30min.

10. The method for preparing an anisotropic scattering sheet according to claim 1, characterized in that: In step S4, the light source (1) is an ultraviolet light source, and the ultraviolet light source is a mercury lamp or an ultraviolet light emitting diode.

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