Highly uniform holographic polymer dispersed liquid crystal grating device and preparation method thereof

Abstract

The present invention provides a highly uniform holographic polymer dispersed liquid crystal grating device and a preparation method thereof. The pressure and temperature modes are controlled in the process step of pressurizing and sealing a filled liquid crystal box so as to level and seal the liquid crystal box and at the same time achieve homogenization of the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box, thereby solving the problem that the components in the holographic polymer dispersed liquid crystal material are uneven or even phase-separated due to the difference in the effect of absorption and filling during the liquid crystal filling process. At the same time, the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is further degassed through the coordinated effect of temperature and pressure, thereby improving the filling uniformity of the holographic polymer dispersed liquid crystal material, and further improving the overall uniformity and optical performance of the grating device subsequently made by the holographic polymer dispersed liquid crystal material.

Description

Technical Field

[0001] The present invention relates to the field of holographic projection display, and more specifically, to a high-uniform holographic polymer dispersed liquid crystal grating device and a preparation method thereof. Background Art

[0002] Holographic display technology is a technology that uses the principles of interference and diffraction to record and reproduce the optical information of three-dimensional objects. It can not only present a three-dimensional image of an object, but also show the color, texture and dynamic changes of the object. The emergence of this technology has completely changed our understanding of display technology and brought a new visual experience. The core of holographic display technology lies in the production of holograms. Holograms are made by irradiating lasers onto objects and recording the optical information of objects using the principles of interference and diffraction. Then, this information can be reproduced as a three-dimensional image, allowing us to observe different sides of the object from different angles. This technology can be used to make various types of holograms, such as reflection, transmission and color holograms.

[0003] Polymer Dispersed Liquid Crystal (PDLC) is a composite material in which liquid crystal is dispersed in micron-sized droplets in an organic solid polymer matrix. This material combines the characteristics of liquid crystal and polymer and can be used to make high-definition, high-contrast display devices. By changing the electric field, the arrangement state of the liquid crystal droplets can be controlled, thereby achieving dynamic changes in the image. Specifically, since the optical axis of the droplets composed of liquid crystal molecules is in a free orientation, its refractive index does not match the refractive index of the matrix. When light passes through the matrix, it is strongly scattered by the droplets and presents an opaque milky white state or a translucent state. Applying an electric field can adjust the optical axis orientation of the liquid crystal droplets. When the refractive indices of the two match, a transparent state is presented. When the electric field is removed, the liquid crystal droplets return to their original scattered light state, thereby displaying.

[0004] Holographic Polymer Dispersed Liquid Crystal (H-PDLC) grating is the product of the combination of holographic technology and polymer dispersed liquid crystal. It is a structured optoelectronic information material and device formed by the periodic arrangement of a polymer-rich phase and a liquid crystal-rich phase. It has the characteristics of high efficiency, switchability, excellent processing performance, and excellent optical performance. It is widely used in high-tech fields such as holographic storage, display, tunable filter, modulated laser, augmented reality (AR), etc. The preparation principle is to mix the monomer, liquid crystal and photoinitiator evenly and then pour them into a liquid crystal box with a fixed box thickness, and then perform photopolymerization under the action of laser coherence. In the bright area of ​​the laser coherent stripe, the free radicals generated by the photoinitiator absorbing photons initiate the polymerization of the monomers. The change in the chemical potential of the system causes the polymer and the liquid crystal to separate, prompting the liquid crystal molecules to diffuse from the bright area of ​​the coherent stripe to the dark area. At the same time, the monomers in the dark area diffuse to the bright area of ​​the coherent stripe for further polymerization, thereby forming a grating structure with periodic distribution of components and refractive index.

[0005] In the prior art, the process of filling and encapsulating holographic polymer dispersed liquid crystal into a liquid crystal box with a fixed box thickness is based on the vacuum suction filling small screen technology of the semiconductor industry, including: first making an empty box with an opening, and placing the empty box in a filling machine to evacuate; then lowering the vacuum empty box into a container containing liquid crystal or a sponge strip soaked with liquid crystal, so that the liquid crystal liquid level is above the empty box filling port; further, nitrogen is introduced into the filling machine, and the liquid crystal is filled into the empty box by atmospheric pressure and capillary action under the condition of vacuum in the empty box, and finally sealed with glue. However, since the composition of holographic polymer dispersed liquid crystal is more complex and diverse, during the filling, the capillary force and gravity act together on different components in the holographic polymer dispersed liquid crystal, and the effects are different, which can easily lead to unevenness or even phase separation in the holographic polymer dispersed liquid crystal system, thereby greatly affecting the grating arrangement and imaging quality in the grating device made therefrom. Summary of the invention

[0006] The present invention aims to overcome at least one defect of the above-mentioned prior art and provides a highly uniform holographic polymer dispersed liquid crystal grating device and a preparation method thereof.

[0007] The object of the present invention is to provide a method for preparing a highly uniform holographic polymer dispersed liquid crystal grating device; the preparation process of the holographic polymer dispersed liquid crystal grating device comprises:

[0008] S1. preparing a liquid crystal cell and a holographic polymer dispersed liquid crystal material having a certain thickness;

[0009] S2, injecting and packaging the holographic polymer dispersed liquid crystal material into the liquid crystal box;

[0010] S3, subjecting the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein to interference exposure under coherent light to obtain the holographic polymer dispersed liquid crystal grating device;

[0011] The pouring process of the holographic polymer dispersed liquid crystal grating material comprises:

[0012] S21, pretreatment: placing the liquid crystal box to be filled and the holographic polymer dispersed liquid crystal material in a liquid crystal filling closed chamber under vacuum; leaving a filling opening on the liquid crystal box to be filled; pre-mixing the holographic polymer dispersed liquid crystal material and performing a degassing treatment;

[0013] S22, liquid crystal perfusion: immersing the perfusion opening into the holographic polymer dispersed liquid crystal material, and injecting the holographic polymer dispersed liquid crystal material into the liquid crystal box by creating an air pressure difference;

[0014] S23, pressurizing and sealing. After the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by pressure and temperature control, and the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is homogenized.

[0015] In the technical solution of the present application, since the composition of the holographic polymer dispersed liquid crystal material is complex and diverse, the pressure and temperature modes are controlled in the step of pressurizing and sealing the filled liquid crystal box so as to level and seal the liquid crystal box and at the same time achieve homogenization of the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box, thereby solving the problem that the components in the holographic polymer dispersed liquid crystal material are uneven or even phase-separated due to the difference in the absorption and filling effects during the liquid crystal filling process. At the same time, the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is further degassed through the coordinated action of temperature and pressure, thereby improving the filling uniformity of the holographic polymer dispersed liquid crystal material, thereby improving the overall uniformity and optical performance of the grating device subsequently made of the holographic polymer dispersed liquid crystal material. Specifically, by applying appropriate pressure to the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein, the liquid crystal box can be squeezed, thereby leveling the liquid crystal box, which is conducive to the uniform distribution of the holographic polymer dispersed liquid crystal material therein. At the same time, applying a certain pressure to the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is conducive to degassing and promoting the flow of the holographic polymer dispersed liquid crystal material; at the same time, under the influence of appropriate temperature, the anchoring force between different molecules in the holographic polymer dispersed liquid crystal material will be reduced, thereby reducing the obstruction of the flow between different components, promoting the flow between components with initial concentration differences, thereby improving the overall uniformity of the holographic polymer dispersed liquid crystal material; therefore, according to appropriate temperature and pressure, the holographic polymer dispersed liquid crystal material in the liquid crystal box is distributed more evenly. Preferably, the glue is UV glue or the like.

[0016] Further, in the step S23, the pressure and temperature control adopts a medium pressure and high temperature mode or a high pressure and medium temperature mode;

[0017] The medium pressure range is (0.4, 0.5] MPa, and the high pressure range is (0.5, 0.6] MPa;

[0018] The medium temperature range is (40, 50]°C, and the high temperature range is (50, 60]°C.

[0019] In the technical scheme, the liquid crystal box is leveled and sealed, and the holographic polymer dispersed liquid crystal material in the liquid crystal box is defoamed and its perfusion uniformity is improved by controlling the pressure and temperature control mode in the pressurized sealing process; the pressure and temperature complement each other and provide important influences on the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein in the pressurized sealing process. When considering the pressure factor, the pressure mainly affects the shaping of the liquid crystal box and the squeezing effect on the holographic polymer dispersed liquid crystal material. The strength of the liquid crystal box determines that the pressure it can withstand cannot be too high. In the case of excessive pressure, it will affect the life of the liquid crystal box and increase safety hazards. However, when the applied pressure is insufficient, it is not enough to level the liquid crystal box and it is difficult to affect the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box. When considering the temperature factor, the temperature mainly affects the flow effect of the holographic polymer dispersed liquid crystal material. When the temperature is too high, the holographic polymer dispersed liquid crystal material is easily deteriorated and the grating structure cannot be formed later. When the temperature is too low, it cannot provide sufficient fluidity for the holographic polymer dispersed liquid crystal material. Therefore, by adopting a dual-factor control method, the shape of the liquid crystal box and the fluidity of the holographic polymer dispersed liquid crystal material can be quickly adjusted within the tolerance limits of the liquid crystal box pressure and the temperature of the holographic polymer dispersed liquid crystal material, thereby improving the uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material therein; specifically, in step S3, the pressure and temperature control adopts a medium-pressure and high-temperature mode or a high-pressure and medium-temperature mode; wherein the medium pressure range is 0.4-0.5MPa, and the high pressure range is 0.5-0.6MPa, both of which can achieve the effect of leveling the liquid crystal box without exceeding the tolerance limit of the liquid crystal box; the medium temperature range is 40-50°C, and the high temperature range is 50-60°C, both of which can make the holographic polymer dispersed liquid crystal material fully flow without causing it to deteriorate and become ineffective.

[0020] Furthermore, in the step S23, the pressurized sealing process can be performed using various types of pressing equipment. The leveling effects of different pressing equipment result in different uniformities, mainly because the uniformity of the pressing medium itself has different effects on the uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material therein. The pressing media with the best to worst uniformity are, in order, air pressure used in automatic degassing machines, airbag pressing used in hard-to-hard laminating machines, and hard pressing used in steel plates. Therefore, preferably, in the present technical solution, the pressurized sealing process uses an automatic degassing machine for pressurization.

[0021] Furthermore, in the step S23, when the liquid crystal box is leveled and sealed in the medium pressure and high temperature mode, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are pre-pressed at medium pressure and medium temperature, and then the temperature is raised to a predetermined temperature in stages, and the heating rate of the stage heating is 0.5-2.0°C / min;

[0022] In the step S23, when the liquid crystal box is leveled and sealed in the high pressure and medium temperature mode, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are pre-pressurized at medium pressure and medium temperature, and then the pressure is increased to a predetermined pressure in stages, and the pressure increase rate of the stage pressure increase is 5-20kPa / min.

[0023] In the present technical solution, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are first pre-pressed at medium pressure and medium temperature, and then the pressure is increased or the temperature is increased in stages, and the pressure is increased and the temperature is adjusted slowly and gradually, so as to effectively control the uniformity of material distribution, the leveling effect of the liquid crystal box and the firmness of the seal; specifically, the temperature increase rate of the stage temperature increase is set to 0.5-2.0℃ / min, and the pressure increase rate of the stage pressure increase is set to 5-20kPa / min, so as to ensure that the liquid crystal inside the liquid crystal box is evenly distributed and well sealed, and the display effect and quality are guaranteed. Preferably, after the stage temperature increase or stage pressure increase reaches the required medium pressure and high temperature or high temperature and medium pressure state, the pressing time is maintained for not less than 10 minutes.

[0024] Furthermore, in the present technical solution, in order to adapt the performance of the grating device manufactured based on the liquid crystal box and holographic polymer dispersed liquid crystal material used, while ensuring the structural strength of the liquid crystal box, the thickness of the liquid crystal box used is 5-10 μm.

[0025] Furthermore, before step S23, step S230 is also included:

[0026] S230, sampling, sampling from the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the bubbles contained in the sample. Before the pressurized sealing process, the bubbles in the holographic polymer dispersed liquid crystal material filled in the liquid crystal box are identified by sampling, so as to preliminarily judge the uniformity of the holographic polymer dispersed liquid crystal material, so that the appropriate temperature and pressure control mode can be selected in the pressurized sealing process to further improve the uniformity of the holographic polymer dispersed liquid crystal material. Preferably, when the sampling in the step S230 finds that there are bubbles in the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, the pressure and temperature control in the step S3 adopts the high temperature medium pressure mode, and the fluidity of the holographic polymer dispersed liquid crystal material in the liquid crystal box is improved as much as possible by high temperature, and the holographic polymer dispersed liquid crystal material is squeezed softly by applying medium pressure to fully discharge the bubbles, so as to further defoam the holographic polymer dispersed liquid crystal material and improve the distribution uniformity of its components at the same time, thereby improving the overall uniformity and reliability of the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box.

[0027] Furthermore, in the step S21, the holographic polymer dispersed liquid crystal material is pre-mixed and deaerated by using an ultrasonic dispersion device, so as to ensure that the components of the holographic polymer dispersed liquid crystal material are dispersed evenly and without bubbles before being filled into the liquid crystal box, so as to save the homogenization time and homogenization steps in the subsequent process, improve the uniformity of the filling of the holographic polymer dispersed liquid crystal material, and improve the production efficiency. Optionally, the pre-mixing and deaeration treatment steps are: the prepared holographic polymer dispersed liquid crystal material is first shaken and mixed with a vortex oscillator for 0.5-3 minutes, and then placed in an ultrasonic instrument at 60°C for 20-40 minutes for uniform mixing to obtain a homogenized and dispersed holographic polymer dispersed liquid crystal material.

[0028] Furthermore, in step S3, after the filling is completed, the liquid crystal box and the filled and packaged holographic polymer dispersed liquid crystal material are placed in a dark room and then subjected to interference exposure under the interference light field of a double-beam light source to obtain the holographic polymer dispersed liquid crystal grating device. By slowly cooling down the liquid crystal box filled with uniform holographic polymer dispersed liquid crystal material and allowing it to stand in a dark room, the liquid crystal box and the holographic polymer dispersed liquid crystal material therein are relaxed and maintain a stable high uniformity state, thereby improving the high uniformity and high stability of the liquid crystal box and the holographic polymer dispersed liquid crystal material therein before interference exposure, thereby improving the optical performance of the prepared grating device.

[0029] Preferably, the liquid crystal box and the injected and packaged holographic polymer dispersed liquid crystal material are placed in a dark room and allowed to stand for 50-90 minutes;

[0030] The interference exposure time is 1-5 minutes, and the irradiation power is 4-6 mW / cm 2; and the angle between the dual-beam light sources is 30°-60°.

[0031] Another object of the present invention is to provide a highly uniform holographic polymer dispersed liquid crystal grating device prepared by the preparation method provided in the technical solution.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] By controlling the pressure and temperature mode in the process step of pressurizing and sealing the filled liquid crystal box, the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box can be leveled and sealed, and at the same time, the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box can be homogenized, thereby solving the problem that the components in the holographic polymer dispersed liquid crystal material are uneven or even phase-separated due to the difference in the absorption and filling effects during the liquid crystal filling process. At the same time, the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is further degassed through the coordinated effect of temperature and pressure, thereby improving the filling uniformity of the holographic polymer dispersed liquid crystal material, and further improving the overall uniformity and optical performance of the grating device subsequently manufactured using the holographic polymer dispersed liquid crystal material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of a method for preparing a highly uniform holographic polymer dispersed liquid crystal grating device.

[0035] Figure 2 This is a sampling point diagram of the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] The present invention is now further described in conjunction with specific examples. The following examples are only for explaining the present invention, but do not constitute a limitation of the present invention. The test samples and test processes used in the following examples include the following (if the specific experimental conditions are not specified in the examples, they are usually carried out according to conventional conditions or according to the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels).

[0039] In the production process, the methods for improving the uniformity of the perfusion of holographic polymer dispersed liquid crystal materials mainly include optimizing the preparation process and adopting a specific preparation method. In terms of optimizing the preparation process, the factors affecting the distribution and uniformity of the liquid crystal material, such as temperature, pressure and light conditions, can be controlled to coordinate the production process, preparation method and raw materials adopted to achieve the improvement of the uniformity of the perfusion of the holographic polymer dispersed liquid crystal material.

[0040] In the present technical scheme, the pressure and temperature modes are controlled in the process step of pressurizing and sealing the filled liquid crystal box so as to level and seal the liquid crystal box and at the same time homogenize the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box, thereby solving the problem that the components in the holographic polymer dispersed liquid crystal material are uneven or even phase-separated due to the difference in the absorption and filling effects during the liquid crystal filling process. At the same time, the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is further degassed through the coordinated effect of temperature and pressure, thereby improving the filling uniformity of the holographic polymer dispersed liquid crystal material, and further improving the overall uniformity and optical performance of the grating device subsequently made by the holographic polymer dispersed liquid crystal material. Specifically, the pressure and temperature control adopted are in a medium pressure and high temperature mode or a high pressure and medium temperature mode; wherein the medium pressure range is (0.4, 0.5]MPa, the high pressure range is (0.5, 0.6]MPa; the medium temperature range is (40, 50]°C, and the high temperature range is (50, 60]°C. Preferably, when the medium pressure and high temperature mode is adopted to level and seal the liquid crystal box, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are first pre-pressed at medium pressure and medium temperature, and then the temperature is staged to a predetermined temperature in the high temperature range. Specifically, the heating rate of the stage heating is 0.5-2.0℃ / min; when the high-pressure medium-temperature mode is used to level and seal the liquid crystal box, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are first pre-pressed at medium pressure and medium temperature, and then the pressure is increased in stages to a predetermined pressure in the high pressure range. Specifically, the pressure increase rate of the stage heating is 5-20kPa / min. Preferably, after the stage heating or stage heating reaches the required medium pressure and high temperature or high temperature and medium pressure state, the pressing time is maintained for not less than 10 minutes.

[0041] In the following examples, photoinitiator 184 was purchased from Shanghai McLean Co., Ltd., TPO was purchased from Shanghai McLean Co., Ltd., 3,3'-carbonylbis(7-diethylaminocoumarin) was purchased from Shanghai McLean Co., Ltd., N-phenylglycine was purchased from Shanghai McLean Co., Ltd., benzoyl peroxide was purchased from Shanghai McLean Co., Ltd., 4(ethoxy)bisphenol A dimethacrylate was purchased from Changxing Chemical, trimethylolpropane triacrylate was purchased from Changxing Chemical, N-vinyl pyrrolidone was purchased from Sinopharm Chemical Reagent Co., Ltd., and GXP-6003 was purchased from Yantai Xianhua Company.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a high uniformity holographic polymer dispersed liquid crystal grating device and a preparation method thereof. Specifically, the preparation method comprises the following steps:

[0044] S1. Prepare a liquid crystal box with a thickness of 5 μm and a holographic polymer dispersed liquid crystal material. The preparation method of the holographic polymer dispersed liquid crystal material is as follows:

[0045] Weigh the following raw materials from the brown sample bottle:

[0046] 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 10 parts of 2-phenoxyethyl methacrylate, 15 parts of 4(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 7 parts of N-vinyl pyrrolidone, 15 parts of GXP-6003;

[0047] The weighed raw materials are first mixed by vortex oscillator for 1 minute, and then placed in an ultrasonic instrument for 30 minutes to mix evenly, so as to obtain a uniform holographic polymer dispersed liquid crystal material.

[0048] S2. Fill and package the uniform holographic polymer dispersed liquid crystal material obtained above into a liquid crystal box:

[0049] S21, pretreatment: placing the liquid crystal box with the injection opening and the uniform holographic polymer dispersed liquid crystal material in a liquid crystal injection closed chamber under vacuum; installing the liquid crystal box on a liquid crystal injection machine;

[0050] S22, liquid crystal perfusion: immersing the perfusion opening of the liquid crystal box into the holographic polymer dispersed liquid crystal material, and introducing nitrogen into the liquid crystal perfusion closed chamber to create a pressure difference to absorb and perfuse the holographic polymer dispersed liquid crystal material into the liquid crystal box;

[0051] S230, before pressurizing and sealing, sampling the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the residual bubbles;

[0052] S23, pressurized sealing. After the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by an automatic degassing machine at 60°C and 0.4MPa for 10 minutes, and the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is further degassed and homogenized. The holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled again, and the remaining bubbles are observed.

[0053] S3. After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and allowed to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0054] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0055] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0056] Example 2

[0057] This embodiment provides a high uniformity holographic polymer dispersed liquid crystal grating device and a preparation method thereof. Specifically, the preparation method comprises the following steps:

[0058] S1. Prepare a liquid crystal box with a thickness of 5 μm and a holographic polymer dispersed liquid crystal material. The preparation method of the holographic polymer dispersed liquid crystal material is as follows:

[0059] Weigh the following raw materials from the brown sample bottle:

[0060] 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 10 parts of 2-phenoxyethyl methacrylate, 15 parts of 4(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 7 parts of N-vinyl pyrrolidone, 15 parts of GXP-6003;

[0061] The weighed raw materials are first mixed by vortex oscillator for 1 minute, and then placed in an ultrasonic instrument for 30 minutes to mix evenly, so as to obtain a uniform holographic polymer dispersed liquid crystal material.

[0062] S2. Fill and package the uniform holographic polymer dispersed liquid crystal material obtained above into a liquid crystal box:

[0063] S21, pretreatment: placing the liquid crystal box with the injection opening and the uniform holographic polymer dispersed liquid crystal material in a liquid crystal injection closed chamber under vacuum; installing the liquid crystal box on a liquid crystal injection machine;

[0064] S22, liquid crystal perfusion: immersing the perfusion opening of the liquid crystal box into the holographic polymer dispersed liquid crystal material, and introducing nitrogen into the liquid crystal perfusion closed chamber to create a pressure difference to absorb and perfuse the holographic polymer dispersed liquid crystal material into the liquid crystal box;

[0065] S230, before pressurizing and sealing, sampling the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the residual bubbles;

[0066] S23, pressurized sealing. After the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by an automatic degassing machine at 40°C and 0.6MPa for 10 minutes, while the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is further degassed and homogenized. The holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled again, and the remaining bubbles are observed.

[0067] S3. After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and allowed to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0068] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0069] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0070] Example 3

[0071] This embodiment provides a high uniformity holographic polymer dispersed liquid crystal grating device and a preparation method thereof. Specifically, the preparation method comprises the following steps:

[0072] S1. Prepare a liquid crystal box with a thickness of 5 μm and a holographic polymer dispersed liquid crystal material. The preparation method of the holographic polymer dispersed liquid crystal material is as follows:

[0073] Weigh the following raw materials from the brown sample bottle:

[0074] 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 10 parts of 2-phenoxyethyl methacrylate, 15 parts of 4(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 7 parts of N-vinyl pyrrolidone, 15 parts of GXP-6003;

[0075] The weighed raw materials are first mixed by vortex oscillator for 1 minute, and then placed in an ultrasonic instrument for 30 minutes to mix evenly, so as to obtain a uniform holographic polymer dispersed liquid crystal material.

[0076] S2. Fill and package the uniform holographic polymer dispersed liquid crystal material obtained above into a liquid crystal box:

[0077] S21, pretreatment: placing the liquid crystal box with the injection opening and the uniform holographic polymer dispersed liquid crystal material in a liquid crystal injection closed chamber under vacuum; installing the liquid crystal box on a liquid crystal injection machine;

[0078] S22, liquid crystal perfusion: immersing the perfusion opening of the liquid crystal box into the holographic polymer dispersed liquid crystal material, and introducing nitrogen into the liquid crystal perfusion closed chamber to create a pressure difference to absorb and perfuse the holographic polymer dispersed liquid crystal material into the liquid crystal box;

[0079] S230, before pressurizing and sealing, sampling the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the residual bubbles;

[0080] S23, pressurized sealing. After the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by an automatic degassing machine at 50°C and 0.6MPa for 10 minutes, while the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is further degassed and homogenized. The holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled again, and the remaining bubbles are observed.

[0081] S3. After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and allowed to stand for 90 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0082] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device was tested by a grating diffraction efficiency tester. At the same time, the haze of the obtained holographic grating device was tested by a haze meter at 23±2°C according to the method shown in GB 2410-2008 "Test method for light transmittance and haze of transparent plastics".

[0083] Example 4

[0084] This embodiment provides a high uniformity holographic polymer dispersed liquid crystal grating device and a preparation method thereof. Specifically, the preparation method comprises the following steps:

[0085] S1. Prepare a liquid crystal box with a thickness of 5 μm and a holographic polymer dispersed liquid crystal material. The preparation method of the holographic polymer dispersed liquid crystal material is as follows:

[0086] Weigh the following raw materials from the brown sample bottle:

[0087] 0.5 parts of 3,3'-carbonylbis(7-diethylaminocoumarin), 2 parts of N-phenylglycine, 10 parts of 2-phenoxyethyl methacrylate, 15 parts of 4(ethoxy)bisphenol A dimethacrylate, 10 parts of trimethylolpropane triacrylate, 7 parts of N-vinyl pyrrolidone, 15 parts of GXP-6003;

[0088] The weighed raw materials are first mixed by vortex oscillator for 1 minute, and then placed in an ultrasonic instrument for 30 minutes to mix evenly, so as to obtain a uniform holographic polymer dispersed liquid crystal material.

[0089] S2. Fill and package the uniform holographic polymer dispersed liquid crystal material obtained above into a liquid crystal box:

[0090] S21, pretreatment: placing the liquid crystal box with the injection opening and the uniform holographic polymer dispersed liquid crystal material in a liquid crystal injection closed chamber under vacuum; installing the liquid crystal box on a liquid crystal injection machine;

[0091] S22, liquid crystal perfusion: immersing the perfusion opening of the liquid crystal box into the holographic polymer dispersed liquid crystal material, and introducing nitrogen into the liquid crystal perfusion closed chamber to create a pressure difference to absorb and perfuse the holographic polymer dispersed liquid crystal material into the liquid crystal box;

[0092] S230, before pressurizing and sealing, sampling the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the residual bubbles;

[0093] S23, pressurized sealing. After the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by an automatic degassing machine at 50°C and 0.4MPa for 10 minutes, and the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is further degassed and homogenized. The holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled again, and the remaining bubbles are observed.

[0094] S3. After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and allowed to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0095] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device was tested by a grating diffraction efficiency tester. At the same time, the haze of the obtained holographic grating device was tested by a haze meter at 23±2°C according to the method shown in GB 2410-2008 "Test method for light transmittance and haze of transparent plastics".

[0096] Comparative Example 1

[0097] This comparative example also provides a holographic polymer dispersed liquid crystal grating device and a preparation method thereof, which differs from Example 1 in that: in step S23, pressurized sealing is performed, and after the filling is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are placed together in an oven at 60°C, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is pressurized for 10 minutes with a 4kg steel plate for leveling and sealing, and the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled, and the remaining bubbles are observed.

[0098] After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and left to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0099] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0100] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0101] Comparative Example 2

[0102] The present comparative example also provides a holographic polymer dispersed liquid crystal grating device and a preparation method thereof, which differs from Example 1 in that: in step S23, pressurized sealing is performed, and after the filling is completed, the filling opening on the liquid crystal box is sealed with glue, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are pressurized at 60° C. for 10 minutes by a hard-to-hard laminating machine for leveling and sealing, the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled, and the remaining bubbles are observed.

[0103] After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and left to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0104] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0105] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0106] Comparative Example 3

[0107] This comparative example also provides a holographic polymer dispersed liquid crystal grating device and a preparation method thereof, which differs from Example 1 in that: in step S23, the liquid crystal box is sealed by dispensing glue, but pressure and temperature control are not adopted for leveling and sealing, and the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled and the remaining bubbles are observed.

[0108] After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and left to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0109] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0110] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0111] Comparative Example 4

[0112] This comparative example also provides a holographic polymer dispersed liquid crystal grating device and a preparation method thereof, which differs from Example 1 in that: in step S23, an automatic degassing machine is used to pressurize the liquid crystal box at 60°C and normal pressure for 10 minutes to level and seal the liquid crystal box, and the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled and the remaining bubbles are observed.

[0113] After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and left to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0114] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device prepared by the above method is tested by a grating diffraction efficiency tester. Specifically, Figure 2 As shown, 13 points in the liquid crystal box are taken to test the diffraction efficiency, and the uniformity of the material in the liquid crystal box is evaluated by calculating the average value and standard deviation of these points.

[0115] At the same time, the haze of the obtained holographic grating device was tested using a haze meter at 23±2° C. according to the method shown in GB 2410-2008 “Test method for light transmittance and haze of transparent plastics”.

[0116] Comparative Example 5

[0117] This comparative example also provides a holographic polymer dispersed liquid crystal grating device and a preparation method thereof, which differs from Example 1 in that: in step S23, an automatic degassing machine is used to pressurize the liquid crystal box at room temperature and 0.4 MPa for 10 minutes to level and seal the liquid crystal box, and the holographic polymer dispersed liquid crystal material filled in the liquid crystal box is sampled and the remaining bubbles are observed.

[0118] After the infusion is completed, the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room and left to stand for 60 minutes; then the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein are moved to a dark room with an angle of 60° and an irradiation power of 5 mW / cm 2 The holographic polymer dispersed liquid crystal grating device was obtained by interference exposure in the interference light field of a double-beam light source for 5 minutes.

[0119] Subsequently, the diffraction efficiency of the holographic polymer dispersed liquid crystal grating device was tested by a grating diffraction efficiency tester. At the same time, the haze of the obtained holographic grating device was tested by a haze meter at 23±2°C according to the method shown in GB 2410-2008 "Test method for light transmittance and haze of transparent plastics".

[0120] The grating devices prepared by the seven methods for preparing holographic polymer dispersed liquid crystal grating devices in preferred embodiment 1, embodiment 2 and comparative examples 1 to 5, the residual degree of bubbles in the holographic polymer dispersed liquid crystal material during sampling (1-10 evaluation, the degree increases in sequence), the average value and variance of the diffraction efficiency (DE), and the haze results are shown in the following table:

[0121]

[0122] By comparing the embodiments and the comparative examples, the influence of the pressing equipment on the uniformity preparation of the grating device can be observed through the comparison between Embodiment 1 and comparative examples 1-3. Under the same other pressing conditions, the defoaming effect and uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material infused therein can be improved to a certain extent by controlling the temperature and pressure for pressing and sealing. The advantages and disadvantages of the pressing equipment in improving the defoaming effect and uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material infused therein are as follows: automatic defoaming machine, hard-to-hard laminating machine, and hard pressing of steel plates.

[0123] By comparing Example 1 and Comparative Examples 4 and 5, it can be observed that the influence of the pressure and temperature control modes on the uniformity of the preparation of the grating device, when other pressing conditions are the same, the modes of controlling the pressure alone and controlling the temperature alone are not effective in improving the defoaming effect and uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material infused therein, the control of temperature and pressure complement each other, and the appropriate temperature and pressure co-control mode can greatly improve the defoaming effect and uniformity of the liquid crystal box and the holographic polymer dispersed liquid crystal material infused therein, and improve the uniformity and optical performance of the prepared grating device.

[0124] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a highly uniform holographic polymer dispersed liquid crystal grating device, the preparation process of the holographic polymer dispersed liquid crystal grating device comprising: S1. preparing a liquid crystal cell and a holographic polymer dispersed liquid crystal material having a certain thickness; S2, injecting and packaging the holographic polymer dispersed liquid crystal material into the liquid crystal box; S3, subjecting the liquid crystal box and the holographic polymer dispersed liquid crystal material filled therein to interference exposure under coherent light to obtain the holographic polymer dispersed liquid crystal grating device; Characterized in that the perfusion process of the holographic polymer dispersed liquid crystal grating material includes: S21, pretreatment: placing the liquid crystal box to be filled and the holographic polymer dispersed liquid crystal material in a liquid crystal filling closed chamber under vacuum; leaving a filling opening on the liquid crystal box to be filled; pre-mixing the holographic polymer dispersed liquid crystal material and performing a degassing treatment; S22, liquid crystal perfusion: immersing the perfusion opening into the holographic polymer dispersed liquid crystal material, and injecting the holographic polymer dispersed liquid crystal material into the liquid crystal box by creating an air pressure difference; S23, pressurizing and sealing: after the filling is completed, the filling opening on the liquid crystal box is sealed with glue, and the liquid crystal box is leveled and sealed by pressure and temperature control, and the holographic polymer dispersed liquid crystal material encapsulated in the liquid crystal box is homogenized; In the step S23, the pressurization and sealing process uses an automatic degassing machine for pressurization; The pressure and temperature control adopts medium pressure and high temperature mode or high pressure and medium temperature mode; The medium pressure range is (0.4, 0.5] MPa, and the high pressure range is (0.5, 0.6] MPa; The medium temperature range is (40, 50]°C, and the high temperature range is (50, 60]°C; In the step S23, when the liquid crystal box is leveled and sealed in the medium pressure and high temperature mode, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are pre-pressed at medium pressure and medium temperature, and then the temperature is raised to a predetermined temperature in stages, and the heating rate of the stage heating is 0.5-2.0°C / min; In the step S23, when the liquid crystal box is leveled and sealed in the high pressure and medium temperature mode, the liquid crystal box and the holographic polymer dispersed liquid crystal material encapsulated therein are pre-pressurized at medium pressure and medium temperature, and then the pressure is increased to a predetermined pressure in stages, and the pressure increase rate of the stage pressure increase is 5-20kPa / min.

2. The preparation method according to claim 1, characterized in that: The thickness of the liquid crystal cell is 5-10 μm.

3. The preparation method according to any one of claims 1 to 2, characterized in that: Before step S23, the method further includes step S230: S230, sampling, sampling from the holographic polymer dispersed liquid crystal material filled in the liquid crystal box, and observing the bubbles contained in the sample.

4. The preparation method according to claim 3, characterized in that: When bubbles are found in the holographic polymer dispersed liquid crystal material filled in the liquid crystal box during random inspection in step S230, the pressure and temperature control in step S3 adopts a high temperature and medium pressure mode.

5. The preparation method according to any one of claims 1 to 2, characterized in that: In the step S1, ultrasonic dispersion equipment is used to pre-mix and degas the holographic polymer dispersed liquid crystal material.

6. The preparation method according to any one of claims 1-2, characterized in that: In step S3, the liquid crystal box and the injected and packaged holographic polymer dispersed liquid crystal material are placed in a dark room and left to stand still, and then interference exposure is performed under the interference light field of a double-beam light source to obtain the holographic polymer dispersed liquid crystal grating device.

7. The preparation method according to claim 6, characterized in that: The liquid crystal box and the injected and packaged holographic polymer dispersed liquid crystal material are placed in a dark room and allowed to stand for 50-90 minutes; The interference exposure time is 1-5 min, the irradiation power is 4-6 mW / cm2; and the angle between the dual-beam light sources is 30°-60°.

8. A highly uniform holographic polymer dispersed liquid crystal grating device, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

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