Pixel orientation based multilayer liquid crystal optical memory stack structure and its information writing and reading method

Abstract

A kind of pixel orientation-based multilayer liquid crystal optical storage stack structure and its information writing and reading method, pixelated liquid crystal orientation area can be designed and prepared according to reading light, information pattern, and according to the principle of reverse design, the transparent liquid crystal optical memory is formed by stacking multiple orientation layers, and the information pattern is read by polarizing plate and microscope cooperation.The present application uses the polarization information of light to store information, and the energy loss of reading light in transmission stage is small for visible light, infrared and other wavebands.The number of stacked layers is much larger than that of traditional optical storage technology, and the space utilization is improved by orders of magnitude.The material has higher high-temperature resistance, acid and alkali resistance and other properties than ordinary optical storage optical disc, which is beneficial to long-term use.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical storage. The application sets the thickness of the liquid crystal layer, and designs and prepares the pixelated liquid crystal molecule orientation area according to the information pattern, so that the polarization direction of the light beam after exiting is related to the liquid crystal orientation angle in the pixel area, the multi-layer liquid crystal layer is stacked, and the information is read by using the microscope and the polarizer. Since the liquid crystal has no absorption to visible light and the refractive index of the material is similar, the interlayer reflection crosstalk is small, so the multi-layer information can be clearly observed. It is a large-capacity, high-space-utilization optical storage technology. At the same time, without the polarizer, the effective information cannot be observed, and the information storage has a certain security. The technology provides a solution for large data storage. BACKGROUND

[0002] In recent years, with the continuous improvement of information technology, the amount of data generated from high-tech fields such as 3D holographic display and astronomical observation to daily life fields such as social entertainment and medical archives is becoming more and more huge, but at present, humans lack effective and convenient storage means for data preservation. The effective service life of traditional hard disk, magnetic tape and other information storage devices is not more than 10 years and the energy consumption is huge, and there are great defects in the preservation of cold data. Although optical storage has a longer storage life and lower energy consumption, the number of layers of optical disc is usually only a few layers, and when the number of layers increases, the interlayer reflection scattering causes serious crosstalk, and the transmittance of the stacked multi-layer light is low, causing the contrast to decrease, making it difficult to read information, so the space utilization is not high. Liquid crystal optical storage uses the polarization characteristics of light to realize information reading in cooperation with the filtering characteristics of the polarizer. The whole process has basically no loss of light energy, and the information has no contact wear, good protection, and is compatible with epoxy resin packaging and other processes. The information protection is strong, and the liquid crystal optical storage remains transparent without a polarizer, which can be applied to the field of secure communication. SUMMARY

[0003] In order to solve the above-mentioned deficiencies of the traditional information storage method, the present application proposes a multi-layer liquid crystal optical storage stacking structure based on pixel orientation and its information writing and reading method. According to the reading light, the pixelated liquid crystal orientation area is designed and prepared according to the information pattern, and according to the principle of reverse design, the multi-layer orientation layer is stacked to form a transparent liquid crystal optical storage, and the information pattern is read by cooperating with the polarizer and microscope.

[0004] Liquid crystal is a birefringent crystal, and its phase retardation δ can be represented by the formula where Δn is the birefringence of the liquid crystal, which cannot be changed for a liquid crystal polymer film. And d is the thickness of the liquid crystal layer, which can be set by the spin coating process to the required thickness.

[0005] The parameters can be changed as needed. The following describes the change process of the light incident liquid crystal storage after a simple parameter setting is introduced

[0006] 1) Single layer information storage: The transformation of a linearly polarized monochromatic wave with polarization components E x ,E y in the X and Y directions respectively, can be described by a Jones matrix. The incident wave can be represented by the matrix After passing through the liquid crystal cell, the emergent wave can be represented by the matrix Thus, we have

[0007]

[0008] where θ is the orientation angle of the liquid crystal molecules. The orientation angle can be varied according to the information pattern, and the thickness of the liquid crystal layer can be adjusted by spin coating so that the phase retardation δ is modulated by π. Thus, the emergent wave matrix is

[0009]

[0010] If an x-polarizer and a microscope are used to read the information at this time, the different orientation angles θ will result in different light intensities, forming a gray scale pattern, which is the information needed.

[0011] 2) Multi-layer information storage: According to the calculation principle of single layer information, after the incident to the second layer with an orientation angle θ2, the emergent wave matrix is represented as

[0012]

[0013] Thus, for the incident to the nth layer, the emergent wave matrix is represented as

[0014]

[0015] Therefore, according to the reverse design principle, we can determine the orientation angle in the pixel area according to the information of each layer, and prepare the pixelated orientation of the multi-layer liquid crystal structure by light orientation, electron beam direct writing and other methods.

[0016] During reading, according to the designed orientation angle, the light is filtered by a polarizer, the stage is moved under a microscope, and each layer pattern is focused respectively, so that the information can be read.

[0017] Compared with the prior art, the present application has the advantages that: the materials used in the present application are all transparent materials, the polarization information of light is used for information storage, and the light energy loss of the reading light in the transmission stage is small for visible light, infrared and other wavebands; the polarization information needs to be read with a polarizer, and has concealment and confidentiality; the refractive indexes of the multiple layers are basically consistent, and there is no ghost image and stray light caused by back and forth reflection between layers, and the imaging clarity is high; the number of stacked layers in the present application is much larger than that of the traditional optical storage technology, and the space utilization is improved by orders of magnitude; the present application is easy to package, and the high temperature resistance, acid and alkali resistance and other performances of the materials are higher than those of the optical disc used in ordinary optical storage, which is beneficial to long-term use. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application with reference to the accompanying drawings.

[0019] Figure 1 (a) is a schematic diagram of a multi-layer liquid crystal memory.

[0020] Figure 1 (b) is a schematic diagram of the principle of reading the stored information by a microscope

[0021] Figure 2 is a double-layer liquid crystal light field simulation diagram. Figure 2 (a) is an original picture; Figure 2 (b) is an orientation angle schematic diagram; Figure 2 (c) is an optical intensity distribution without a polarizer; Figure 2 (d) is an optical intensity distribution with a polarizer. DETAILED DESCRIPTION

[0022] The present application will be described in more detail by referring to the accompanying drawings. Each part in the drawings is not drawn to scale for the sake of clarity. In addition, some parts that are well known can not be shown in the drawings.

[0023] Many specific details of the present application are described in the following in order to more clearly understand the present application, such as the structure, material, size, processing and technology of the components. But as those skilled in the art can understand, the present application can be implemented without these specific details.

[0024] Figure 1 (a) shows a schematic diagram of liquid crystal optical storage based on arbitrary orientation, and the main materials include a glass substrate, a light orientation layer, and a liquid crystal polymer film. According to the characteristics of the stored information, the liquid crystal polymer film is formed with pixelized orientation by the light orientation material, and the periodic structure of the orientation layer and the liquid crystal layer is stacked to become a multi-layer readable liquid crystal memory. Figure 1(b) shows the process of reading the multi-layer information by polarizing microscope. The information carried by each liquid crystal layer can be obtained by moving the stage under the polarizer and microscope at a certain angle.

[0025] Specifically, according to the requirement of storing and reading information, the wavelength of the light beam used for reading information, the resolution of the microscope and other information are combined to determine the thickness of the liquid crystal polymer film and the characteristic size of the pixel. According to the birefringence of the liquid crystal polymer and the wavelength of the light beam, the appropriate thickness of the liquid crystal layer film is derived by using the Jones matrix. At this thickness, the direction of the polarizer when reading information is specified, which also determines the reference of the orientation angle of the single pixel area. Combined with the resolution of the microscope and other parameters such as process conditions, the size of the smallest pixel area that can be distinguished is determined.

[0026] After the thickness of the liquid crystal layer and the size of the orientation area are determined, the thickness of the orientation layer is further determined so that the upper orientation layer does not affect the liquid crystal layer that has been oriented below. Generally, the orientation layer has little effect on the solidified liquid crystal layer, and the effects of different orientation methods also differ, but this factor still needs to be considered. In the present application, the thickness of the photo-alignment layer is in the order of hundreds of nanometers, which does not affect the liquid crystal layer below.

[0027] The orientation layer is prepared by spin coating and curing process, and the pixelated orientation of the orientation layer is carried out by optical projection exposure combined with the information pattern to be stored. After the liquid crystal polymer film is cured, a new round of preparation can be carried out according to the information pattern.

[0028] The orientation method of the present application is projection exposure orientation, but as is well known to those skilled in the art, photolithography, laser direct writing, focused ion beam / electron beam direct writing, chemical etching microstructure and other orientation methods can also be applied to pixelated orientation, so different orientation methods should not be considered as new inventions.

[0029] Figure 2 It can be seen that, according to the Figure 2 (a) The original image is designed to have an orientation angle, Figure 2 (b) The orientation angle distribution can be seen, and it is worth noting that the data is converted in different software. Without a polarizer, Figure 2 (c) It can be seen that the light field is relatively uniform in a 23*23 μm 2 area, and the information cannot be clearly known, while with a polarizer in the x-axis, Figure 2 (d) The pattern information is clearly reproduced, proving the effectiveness and concealment of the method.

[0030] Experiments show that a 1 cm 3Liquid crystal optical storage cube can store about 128-6400GB data, and is a high efficient and energy saving optical storage method with strong security, which provides a solution for large data storage.

[0031] In the foregoing detailed description, specific embodiments of the application have been described. It will be apparent, however, to one skilled in the art that many modifications and variations to the specific embodiments described herein can be made. It is intended that the application embrace all such modifications and variations as fall within the scope of the appended claims and their equivalents. Accordingly, the specification is to be regarded in an illustrative manner and not as restrictive.

Claims

1. A pixel orientation based multilayer liquid crystal optical memory stack structure comprising a transparent substrate, characterized in that, A first light orientation layer, a pixel-arranged polymer liquid crystal layer, a second light orientation layer, a pixel-arranged polymer liquid crystal layer, a pixel-arranged n-th light orientation layer and a polymer liquid crystal layer are prepared on the transparent substrate in sequence. incident light matrix then the incident light matrix of a certain pixel of the first liquid crystal layer satisfies the following formula: The second liquid crystal layer of a certain pixel of the exit light matrix satisfies the following formula: The exit light matrix of a certain pixel of the nth liquid crystal layer satisfies the following formula: where θ - θ n is the phase retardation amount, and Δn is the liquid crystal birefringence, and d is the liquid crystal layer thickness.

2. The pixel orientation based multilayer liquid crystal optical memory stack structure of claim 1, wherein, The light orientation layer is based on orientation by photodegradation, photocrosslinking or photoisomerization, or pixelated orientation by mechanical rubbing or chemical etching.

3. The pixel orientation based multilayer liquid crystal optical memory stack structure of claim 1, wherein, The working temperature range of the polymer liquid crystal layer is higher than the curing temperature of the orientation layer, and the thickness of the polymer liquid crystal layer is freely set by a spin coating process, and is generally set to be a half-wave condition of the wavelength of the light source for reading information.

4. The pixel orientation based multilayer liquid crystal optical memory stack structure of claim 1, wherein, The transparent substrate is transparent quartz, K9 glass, a transparent plastic substrate or a flexible substrate.

5. A method for information writing in a pixel-orientation-based multilayer liquid crystal optical memory, applied to a pixel-orientation-based multilayer liquid crystal optical memory stack structure as claimed in claim 1, characterized in that, The method comprises the following steps: S1, preparing a first light orientation layer on a transparent substrate: designing the orientation angle of different pixels of the layer according to the information to be stored, and preparing a pixelated orientation area, wherein the pixel size ranges from 1 μm*1 μm to 100 nm*100 nm; S2, spin coating a polymer liquid crystal layer on the first light orientation layer, wherein the thickness of the polymer liquid crystal layer is designed according to the wavelength of the light for reading information, and the phase retardation reaches π; S3, preparing a second light orientation layer on the polymer liquid crystal layer, and sequentially preparing a plurality of layers in the same manner, so as to finally form a multilayer liquid crystal optical storage stacking structure.

6. A method for writing information in a pixel orientation based multilayer liquid crystal optical memory as claimed in claim 5, wherein, The first light orientation layer is prepared on the transparent substrate by means of inclined deposition, PI solution spin coating and light orientation solution spin coating.

7. The method for writing information in a pixel orientation based multilayer liquid crystal optical memory as claimed in claim 5, wherein, The pixelated orientation area is prepared by means of projection exposure, laser direct writing or mechanical rubbing.

8. The method for writing information in a pixel orientation based multilayer liquid crystal optical memory as claimed in claim 5, wherein, According to the information pattern to be stored, the corresponding exit light field intensity is calculated by designing and controlling the thickness of the liquid crystal layer, the orientation angle of the pixel area and the angle of the polarizer, and the light field intensity is the corresponding information value.

9. A method for reading information from a pixel orientation based multilayer liquid crystal optical memory, applied to a pixel orientation based multilayer liquid crystal optical memory stack structure as claimed in claim 1, characterized in that, The method comprises the following steps: S1, according to the wavelength of the light for reading information, transmitting the light from the lower surface of the substrate of the multilayer liquid crystal optical storage stacking structure, and after the light is emitted from the outermost polymer liquid crystal layer, the light is sequentially transmitted through a polarizer and a microscope, and then is imaged on a CCD, and the gray scale image is obtained by rotating the polarizer according to the orientation angle; S2, the distance between the multilayer liquid crystal optical storage stacking structure and the microscope objective is controlled by adjusting the stage up and down, so that the surface of each polymer liquid crystal layer can be imaged, and the information of each layer is read.

10. A method of reading information from a pixel orientation based multilayer liquid crystal optical memory as claimed in claim 9, wherein, The polarization information of the read light field is corresponding to the stored information.

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