Liquid crystal alignment layer preparation method based on inorganic thin film

Abstract

The present invention provides an inorganic thin film alignment technique only based on one deposition mode and a single coating material system, which can achieve both stable and high-contrast vertical alignment and a good parallel alignment effect. The technique relates to preparation methods for alignment films in two alignment directions. First, in the present invention, by adjusting magnetron sputtering conditions and the duration and bombardment angle of plasma bombardment on an SiO2-based inorganic material thin film, an inorganic material vertical alignment thin film having a specific thickness and morphology can be prepared, and liquid crystal devices manufactured by performing different treatment on inorganic vertical alignment film substrates subjected to bombardment for different durations all can achieve a vertical alignment effect on liquid crystals, but there are slight differences. Second, in the present invention, a magnetron sputtering method is used to deposit a film on a substrate at a specific angle, so that an inorganic parallel alignment layer for liquid crystals can be prepared; and by adjusting preparation conditions, when an oblique sputtering angle is greater than 25°, the alignment layer can achieve a parallel alignment effect on the liquid crystals.

Description

Method for preparing liquid crystal alignment layer based on inorganic thin film TECHNICAL FIELD

[0001] The present application belongs to the technical field of liquid crystal display, and proposes an application based on integrated equipment of plasma bombardment and magnetron sputtering, inorganic alignment technology for preparing liquid crystal alignment layer by using inorganic thin film material, which relates to a preparation method of alignment film in two alignment directions. BACKGROUND

[0002] Liquid crystal display device, generally referred to as LCD (Liquid Crystal Display), is related to all aspects of life, such as watches, calculators, televisions, word processors, personal computers, video phones and so on. LCD is more and more widely used in various fields due to its low power consumption, small size, light weight, large amount of displayed information, and the ability to display various types of information such as characters, graphics (including Chinese characters, curves, tables, etc.), and is an absolute mainstream in portable devices.

[0003] In the process of producing liquid crystal display devices, the orientation of liquid crystal molecules plays an important role, and the quality of the orientation greatly affects the performance of the liquid crystal display device. As a product of the combination of semiconductor integrated circuits and liquid crystal displays, liquid crystal on silicon (LCoS) can effectively take advantage of the high integration of integrated circuit technology, fully utilize the advanced process conditions of the semiconductor industry, and provide the possibility of miniaturization, ultra-high resolution realization and low power consumption for light control devices, and is widely used in display, wavefront correction, light field control and many other fields, and has entered the stage of 4K / 8K ultra-high resolution.

[0004] There are many methods for aligning liquid crystals, which can be mainly divided into two categories: contact method and non-contact method. Friction method is widely used in industrial production due to its mature technology and simple operation, but the static electricity generated in the operation process and the groove defects left by friction limit the use of friction method. Non-contact method includes many categories, such as light control method, polyimide LB film alignment method, etc. However, these alignment methods all use high molecular organic thin film as alignment layer to induce the alignment of liquid crystal molecules, and the properties of high molecular organic matter cause the change of film performance when the alignment layer is subjected to temperature, humidity or other environmental changes, which affects the liquid crystal device life. Therefore, some inorganic materials are used to prepare liquid crystal alignment layer, which provides the possibility for the application of liquid crystal devices in ultraviolet modulation and high-energy laser working environment, and provides a solution for the development of LCoS (Liquid Crystal on Silicon) devices.

[0005] In the 1980s, people used vacuum deposition to deposit inorganic materials such as metal, oxide and fluoride on a substrate placed at an angle. This oblique evaporation orientation method also achieves the orientation effect of the rubbing technique. The deposition at a certain angle can produce a directional arrangement effect for liquid crystal molecules. This orientation method is called oblique evaporation method. The orientation film obtained by this method has good light and heat stability, and the photoelectric devices made therefrom have high contrast and good uniformity. At the same time, someone proposed an orientation method of using ion beam to treat the surface layer of inorganic thin film to produce a liquid crystal orientation layer. This type of orientation method has the characteristics of repeated cleaning and baking, and is suitable for production and application combined with vacuum deposition equipment.

[0006] In addition to the above two orientation methods, there are also nano-particle doping or self-assembly, diamond rubbing orientation and other methods for orientation of inorganic materials. However, these methods are complex in operation and preparation process, and have not been widely used in real industrial application. SUMMARY

[0007] The present application proposes an inorganic thin film orientation technology which can realize stable, high-contrast vertical orientation and good parallel orientation effect based on only one coating method and a single coating material system.

[0008] The present application proposes an inorganic orientation technology based on an integrated equipment of plasma bombardment and magnetron sputtering, which uses inorganic thin film material to prepare a liquid crystal orientation layer. The technology relates to the preparation methods of orientation films in two orientation directions. The present application can prepare inorganic material vertical orientation thin films with specific thickness and morphology by adjusting the magnetron sputtering conditions, the length of time and the angle of plasma bombardment of SiO2-like inorganic material thin films. Liquid crystal devices prepared by different treatments of inorganic vertical orientation film substrates with different bombardment lengths can all achieve the vertical orientation effect of liquid crystal. Through testing means, it is found that there are some differences in the liquid crystal orientation effect of the three types of vertical orientation liquid crystal devices. First, the liquid crystal device prepared by using an inorganic vertical orientation film substrate with a short bombardment length will produce a degradation of orientation effect after being placed for a certain period of time. Second, the liquid crystal device prepared by immersing an inorganic vertical orientation film substrate with a short bombardment length in a long alkyl chain ammonium chloride solution has stable vertical orientation effect and long retention time. Third, the liquid crystal device prepared by using an inorganic vertical orientation film substrate with a long bombardment length also has stable vertical orientation effect and long retention time. Based on the integrated equipment of plasma bombardment and magnetron sputtering, the present application can prepare inorganic film parallel orientation layers of liquid crystal by magnetron sputtering at a specific angle. By adjusting the preparation conditions, when the oblique sputtering angle is greater than 25 degrees, the thin film orientation layer substrate prepared can achieve the parallel orientation effect of liquid crystal after being made into a liquid crystal device.

[0009] To solve the above technical problems, the application adopts the following technical solutions:

[0010] A liquid crystal alignment layer preparation method based on inorganic thin film, the alignment of the liquid crystal alignment layer includes one or more of vertical alignment and parallel alignment;

[0011] When the alignment of the liquid crystal alignment layer includes vertical alignment, the preparation method includes:

[0012] S1, film plating is performed on the substrate by sputtering to form a film plating layer;

[0013] S2, the film plating layer is bombarded again to obtain the liquid crystal alignment layer;

[0014] When the alignment of the liquid crystal alignment layer includes parallel alignment, the preparation method includes: A, film plating is performed on the substrate by sputtering at an inclined sputtering angle greater than 25° to obtain the liquid crystal alignment layer.

[0015] The application is based on the same inorganic thin film system and single equipment, and can realize the obtaining of two kinds of alignment direction films. The application is a brand new preparation method without the need to replace the equipment and the thin film system, greatly reduces the acquisition cost of different alignment films and simplifies the acquisition process.

[0016] The application discloses an integrated equipment of plasma bombardment and magnetron sputtering, which can realize the preparation technology of inorganic alignment layer with liquid crystal alignment effect by only adjusting the time length and bombardment angle of plasma bombarding SiO2 inorganic material thin film. The inorganic material thin film with specific thickness and morphology can be prepared by adjusting the preparation conditions, and the liquid crystal device prepared by the substrate using the inorganic thin film can realize the alignment effect on the liquid crystal. Based on the equipment, the inorganic material thin film alignment layer based on a single film system can be prepared, and by adjusting the preparation conditions, the inorganic thin film vertical alignment layer and the inorganic thin film parallel alignment layer can be obtained.

[0017] The application is based on the integrated equipment of magnetron sputtering and ion beam bombardment to realize the preparation of vertical alignment and parallel alignment thin film substrates. For inorganic vertical alignment film, the application uses a method combining magnetron sputtering and ion beam bombardment, the substrate and the target material are placed in parallel, a layer of inorganic thin film is formed on the substrate by magnetron sputtering, and then the film layer on the substrate is bombarded by the ion source at a specific angle for a specific time to obtain a vertically aligned inorganic thin film. For inorganic parallel alignment film, the target material and the substrate are placed at a certain angle, and then a layer of inorganic thin film is formed on the substrate by magnetron sputtering, which has a parallel alignment effect on liquid crystal molecules.

[0018] The inorganic film parallel alignment layer of liquid crystal can be prepared by magnetron sputtering method at a specific angle. The inorganic film parallel alignment layer prepared by fixing the substrate position or rotating the substrate during the magnetron sputtering process can realize the parallel alignment of liquid crystal by adjusting the preparation conditions. There is a certain angle threshold for the inorganic alignment layer to realize the parallel alignment. Only when the sputtering angle is greater than 25 degrees, the parallel alignment of liquid crystal can be realized. When the sputtering angle is less than 25 degrees, the substrate has no obvious alignment effect, and the microscopic image obtained by changing the angle between the liquid crystal cell and the polarizer does not change significantly. When the sputtering angle is greater than 25 degrees and gradually increases, the alignment effect of the liquid crystal cell is gradually improved. Therefore, the sputtering angle for parallel alignment is greater than 25 degrees.

[0019] Preferably, when the alignment of the liquid crystal alignment layer includes vertical alignment, in step S2, the bombardment includes one or more of short-time bombardment and long-time bombardment; the bombardment time of the short-time bombardment is not longer than 300 seconds; the bombardment time of the long-time bombardment is 300-1800 seconds; and the angle of the bombardment includes multi-angle bombardment from 0° to 60°.

[0020] Preferably, the angle of the bombardment includes multi-angle bombardment every 15° from 0° to 60°; and when the bombardment is the short-time bombardment, step S2 further includes: after the short-time bombardment, treating the liquid crystal alignment layer with long-alkyl-chain ammonium chloride solution.

[0021] The angle of the bombardment is set from 0° to 60°, and preferably every 15° is an angle interval condition for multi-angle bombardment.

[0022] Preferably, the operation of the long-alkyl-chain ammonium chloride solution treatment includes: immersing the liquid crystal alignment layer in a dilute aqueous solution of long-alkyl-chain ammonium chloride with a volume fraction of 0.1-0.5% for 20-60 minutes, then rinsing with deionized water, drying at room temperature, and heating at 130°C for 20-60 minutes after drying.

[0023] The inorganic thin film prepared by magnetron sputtering method can be prepared into an inorganic material thin film vertical alignment layer of liquid crystal after short-time ion beam bombardment of the inorganic thin film layer. The substrate using the alignment film to make a liquid crystal device has unstable vertical alignment effect, and the alignment effect will deteriorate after a certain period of time.

[0024] The inorganic orientation film prepared by magnetron sputtering method combined with short-time ion beam bombardment of the film layer can achieve stable vertical orientation effect of the inorganic vertical orientation film after being treated by long alkyl chain ammonium chloride solution. The substrate treated by the method has stable vertical orientation effect and long time of good orientation effect after being made into liquid crystal device.

[0025] The inorganic film prepared by magnetron sputtering method can be made into inorganic vertical orientation layer after long-time ion beam bombardment of the film layer. The substrate made into liquid crystal device by using the orientation film has stable vertical orientation effect and long time.

[0026] Preferably, when the orientation of the liquid crystal orientation layer includes vertical orientation, the inclined sputtering angle of the sputtering in step S1 is 0°; when the orientation of the liquid crystal orientation layer includes parallel orientation, the inclined sputtering angle of the sputtering in step A is greater than 45°.

[0027] The inorganic film vertical orientation layer can be prepared by the method of magnetron sputtering, in which the substrate is coated at 0° direction to the normal line of the substrate, and then the coated film layer is bombarded by ion beam at a specific angle and for a specific time. The liquid crystal device made by using the inorganic thin film orientation substrate can achieve the effect of liquid crystal vertical orientation.

[0028] The liquid crystal is oriented by the method of magnetron sputtering inclined coating. The inclined coating angle is positively correlated with the orientation performance of the liquid crystal device. The inorganic orientation film with parallel orientation is obtained under the condition of large coating angle, and the coating angle should be greater than 25°. The liquid crystal cell has obvious bright-dark state change under the condition of 45° coating angle, and the orientation effect of the liquid crystal cell corresponding to the substrate is best when the coating angle is 60°.

[0029] Preferably, when the orientation of the liquid crystal orientation layer includes parallel orientation, the inclined sputtering angle in step A is 60°.

[0030] Preferably, the sputtering includes magnetron sputtering; and the bombardment includes plasma bombardment.

[0031] Preferably, the conditions of the magnetron sputtering include: the target material is Si target, the vacuum pressure is 3×10 -3 Pa, the working gas pressure is 1.1×10 -1 Pa, the Ar volume flow rate is 300 sccm, the O2 volume flow rate is 200 sccm, the working voltage is 335±5V, the SiO2 film layer is formed on the substrate, and the thickness is 20-200nm; the conditions of the plasma bombardment include: the ion source is Ar + , the vacuum pressure is 1.1×10 -3 Pa, the Ar + working gas pressure is 6.9×10-2 Pa, working voltage 1350V, duty cycle 85%, Ar + The volume flow rate is 300sccm.

[0032] The target material of the present application is a Si target, and the principle is that after the reaction of diffused Si and incorporated O in space, a SiO2 thin film is formed on the substrate surface.

[0033] The working pressure of the present application in the process of magnetron sputtering coating is 1.1x10 -1 Pa, and the working pressure in the process of ion beam bombardment is 6.9x10 -2 Pa.

[0034] A liquid crystal alignment layer prepared by the above method.

[0035] The pre-tilt angle of the liquid crystal molecules of the liquid crystal device prepared by the inorganic vertical alignment film substrate prepared by the present application is between 88-90°, and the pre-tilt angle of the liquid crystal molecules of the liquid crystal device prepared by the inorganic parallel alignment film substrate is between 0-1°.

[0036] The application of the above liquid crystal alignment layer is used for preparing a liquid crystal display device.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The present application proposes an inorganic thin film alignment technology which can realize stable, high-contrast vertical alignment and good parallel alignment effect based on only one coating method and a single coating material system, and the technology relates to the preparation methods of two kinds of alignment direction alignment films. As for the inorganic vertical alignment film, the inorganic material vertical alignment thin film with specific thickness and morphology can be prepared by adjusting the magnetron sputtering conditions, the length of time and the angle of plasma bombardment of the SiO2-like inorganic material thin film, and the liquid crystal devices prepared by using inorganic vertical alignment film substrates with different bombardment lengths after different treatments can all realize the vertical alignment effect on liquid crystals, but there are slight differences. As for the inorganic parallel alignment film, the inorganic film parallel alignment layer of liquid crystal can be prepared by using the magnetron sputtering method to coat the substrate at a specific angle based on the integrated equipment of plasma bombardment and magnetron sputtering; and by adjusting the preparation conditions, the inorganic thin film parallel alignment layer substrate prepared when the inclined sputtering angle is greater than 25 degrees can realize the parallel alignment effect on liquid crystal after being made into a liquid crystal device. BRIEF DESCRIPTION OF DRAWINGS

[0039] Fig. 1 is a preparation and test flowchart of the liquid crystal device of the inorganic vertical alignment film substrate of the present application.

[0040] Fig. 2 is a preparation flowchart of the inorganic vertical alignment film of the present application.

[0041] Figure 3 is a schematic diagram of ion beam bombardment of an inorganic vertical alignment film substrate according to the present application.

[0042] Figure 4 is a schematic diagram of the soaking operation of an inorganic vertical alignment film substrate according to the present application.

[0043] Figure 5 is a schematic diagram of the spraying spacer of an inorganic alignment film substrate according to the present application.

[0044] Figure 6 is a schematic diagram of the preparation of a liquid crystal device from an inorganic alignment film substrate according to the present application.

[0045] Figure 7 is a first preparation flow chart of a liquid crystal device from an inorganic vertical alignment film substrate according to the present application.

[0046] Figure 8 is a second preparation flow chart of a liquid crystal device from an inorganic vertical alignment film substrate according to the present application.

[0047] Figure 9 is a schematic diagram of the simple structure of a polarizing microscope for taking polarized images of a liquid crystal device according to the present application.

[0048] Figure 10 is a schematic diagram of the pre-tilt angle of liquid crystal molecules in a liquid crystal device according to the present application.

[0049] Figure 11 is a schematic diagram of the optical path for testing the pre-tilt angle of a liquid crystal device according to the present application.

[0050] Figure 12 is a polarized image of a liquid crystal device prepared from an inorganic vertical alignment film substrate with a short bombardment time according to the present application.

[0051] Figure 13 is a polarized image of a liquid crystal device prepared from an inorganic vertical alignment film substrate with a short bombardment time and treated with a long alkyl chain ammonium chloride solution according to the present application.

[0052] Figure 14 is a polarized image of a liquid crystal device prepared from an inorganic vertical alignment film substrate with a long bombardment time according to the present application.

[0053] Figure 15 is the pre-tilt angle test results of a liquid crystal device prepared from an inorganic vertical alignment film substrate according to the present application.

[0054] Figure 16 is a preparation and test flow chart of a liquid crystal device from an inorganic parallel alignment film substrate according to the present application.

[0055] Figure 17 is a schematic diagram of the preparation of an inorganic parallel alignment film according to the present application.

[0056] Figure 18 is a schematic diagram of the preparation of a liquid crystal device from an inorganic parallel alignment film substrate according to the present application.

[0057] Figure 19 is a graph of the dependence of the alignment effect of a liquid crystal device prepared from an inorganic parallel alignment film substrate on the angle of the film coating according to the present application.

[0058] Figure 20 is a graph showing the pre-tilt angle of the liquid crystal device prepared from the parallel oriented film substrate of the present application as a function of the film deposition angle.

[0059] Figure 21 is an AFM 2D scan of the surface of the substrate. In which, (a) surface of the inorganic thin film without bombardment; (b) surface of the inorganic vertical alignment thin film with long bombardment time and large bombardment angle.

[0060] Figure 22 is a comparison of the XPS full spectrum test data of the surface of the inorganic vertical alignment layer.

[0061] Figure 23 is a comparison of the XPS fine spectrum test data of the surface of the inorganic vertical alignment layer.

[0062] Figure 24 is an AFM 2D scan of the surface of the tilted film deposition substrate. In which, the film deposition angle is (a) 0°; (b) 45°. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in further detail below with reference to the drawings.

[0064] Example 1

[0065] The preparation and test process of the vertical alignment liquid crystal device is shown in Figure 1. The first preparation method of the vertical alignment liquid crystal device is as follows (the specific preparation process is shown in Figure 7):

[0066] S1 (magnetron sputtering thin film): first prepare a batch of cut ITO glass substrates (substrate size is 15*20mm, ITO thickness is 30-50nm, square resistance is 100-300Ω / □), the film deposition instrument used is a single optical film deposition machine, the film deposition mode of the ITO glass substrate is shown in Step 1 of Figure 2, the vacuum pressure during film deposition is 3x10 -3 Pa; working gas pressure is 1.1x10 -1 Pa; Ar volume flow is 300sccm, O2 volume flow is 200sccm; working voltage is 335±5V, the magnetron sputtering target source is deposited at a normal incidence angle with the substrate, and the target thickness of the SiO2 film layer is set to be in the range of 20-200nm;

[0067] S2 (ion beam bombardment thin film): bombard the above-mentioned SiO2 film layer with an Ar + ion source, and the SiO2 film layer substrate is at an angle with the Ar + ion source as shown in Step 2 of Figure 2, the orientation substrate is at an angle with the Ar + ion source, the vacuum pressure during bombardment is 1.1x10 -3 Pa; Ar + working gas pressure is 6.9x10 -2 Pa; working voltage is 1350V; duty cycle is 85%; Ar+ The volume flow rate is 300 sccm; the bombardment time is set to be no longer than 300 s. The bombardment angle is set to be from 0° to 60° at an interval of 15°, and the direction along the angle is defined as the bombardment direction. See FIG. 3 for details.

[0068] S3 (treatment of the glass substrate by short bombardment time): The glass substrate bombarded by the ion beam for a short time is placed in a polytetrafluoroethylene glass cleaning rack, and then placed in deionized water. The cleaning temperature is set to be 40°C, the cleaning time is set to be 20 minutes, and ultrasonic cleaning is performed. During the cleaning process, it is necessary to ensure that the deionized water covers the glass substrate. After the ultrasonic cleaning is completed, water replacement is performed, and the same cleaning process is repeated three times. After the cleaning is completed, the cleaned substrate is taken out, the surface water stains are blown off by a nitrogen gun, and the substrate is placed in a drying oven at 120°C for drying for 2 hours. After the substrate is completely dried, the glass is taken out, and the surface temperature of the substrate is reduced to room temperature.

[0069] S4 (spraying spacers): The substrate plated as described above is placed on the operation table of the dry spraying equipment, spherical spacers with a diameter of 15 μm are added to the spray hole, the spray switch is pressed for ten seconds, and the spacers are deposited completely. See FIG. 5 for details.

[0070] S5 (filling liquid crystal and packaging): The substrate with the deposited spacers and the cleaned substrate are overlapped in the anti-parallel direction of the bombardment direction. See FIG. 6 for details. The long side is sealed with AB glue, and the short side is left with a gap for liquid crystal filling. After the glue is dry, an inorganic alignment substrate empty liquid crystal cell is obtained. Negative liquid crystal is filled into the cell, and the cell is sealed with AB glue after the liquid crystal fills the cell under capillary action. The packaging of the liquid crystal cell is completed.

[0071] S6 (photographing polarized images of liquid crystal devices): Polarized microscope was used to photograph the polarized images of the liquid crystal cell. The schematic diagram of the simple structure of the polarized microscope is shown in FIG. 9. The back light was turned on, the polarization direction of the polarizer 1 was fixed, the liquid crystal cell was placed between the polarizer 1 and the polarizer 2, the rotation angle of the polarizer 2 was adjusted to be parallel or orthogonal to the polarization direction of the polarizer 1, the polarized images of the liquid crystal cell just prepared and after being placed for 15 days were photographed respectively, and the images were collected and processed to obtain the polarized images of the liquid crystal device prepared by the short ion bombardment time vertical alignment substrate. Details are shown in FIG. 12. It can be seen from the figure that the vertical alignment effect is good just after preparation, and the alignment effect is poor after 15 days, indicating that the liquid crystal device produces alignment degradation phenomenon after being placed for a certain period of time. In the figure, 1. the ion beam bombardment angle is 45°; 2. in FIG. a, the liquid crystal cell orientation direction is 0° to the polarized axis direction, and in FIG. b, the liquid crystal cell orientation direction is 45° to the polarization direction; 3. the white arrow in the figure represents the polarizer P and the analyzer A; 4. the bottom graph is the dark state phenomenon observed under the polarized light microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed by naked eye between the orthogonal polarizers.

[0072] S7 (measuring the pre-tilt angle of the liquid crystal molecules in the liquid crystal device): The pre-tilt angle of the liquid crystal molecules is shown in FIG. 10. The crystal rotation method was used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal cell. The measurement light path is shown in FIG. 11. The entire test light path is composed of a laser light source, two orthogonal polarizers serving as a polarizer and an analyzer respectively, a detector, and a rotating stage on which the test liquid crystal cell is placed. The rotating stage is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at an angle of 45° to the polarization direction of the polarizer. The liquid crystal cell is rotated around an axis perpendicular to the orientation direction and passing through the center of the liquid crystal cell. The information change of the outgoing light generated when the liquid crystal cell is rotated by the stepping motor is received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertical alignment liquid crystal device prepared by the short ion bombardment time substrate just after preparation and the measurement data after 6 months were collected and processed, and the results are shown in FIG. 15.

[0073] Example 2

[0074] The preparation and test process of the vertical alignment liquid crystal device is shown in FIG. 1. The second preparation method of the vertical alignment liquid crystal device is as follows (the specific preparation process is shown in FIG. 8):

[0075] S1 (magnetic control sputtering film): A batch of cut ITO glass substrates (substrate size: 15*20 mm, ITO thickness: 30-50 nm, square resistance: 100-300 Ω / D) were prepared. The film coating instrument used was a single optical film coating machine. The film coating method of the ITO glass substrate is shown in Step 1 of FIG. 2. The vacuum pressure during film coating was 3*10 -3 Pa; working air pressure: 1.1*10 -1Pa; Ar volume flow rate 300 sccm, O2 volume flow rate 200 sccm; working voltage 335±5V, magnetron sputtering target source and substrate at normal incidence angle film, set SiO2 film layer target thickness 20-200nm interval;

[0076] S2 (ion beam bombardment thin film): using Ar + ion source bombardment of the above SiO2 film layer, SiO2 film layer substrate and Ar + ion source orientation diagram as shown in Figure 2, Step 2, the orientation of the substrate and Ar + source at a certain angle, the vacuum pressure is 1.1×10 -3 Pa; Ar + working pressure 6.9×10 -2 Pa; working voltage 1350V; duty cycle 85%; Ar + volume flow rate of 300 sccm; bombardment time is set not more than 300s. In which the angle of inclination is set from 0° to 60° every 15° as an angle interval conditions, and is defined as the direction along the angle of inclination is the direction of bombardment, can be seen in Figure 3;

[0077] S3 (short bombardment time of the substrate processing method 2): the ion beam short time bombardment of glass substrate immersed in long alkyl chain ammonium chloride dilute aqueous solution (usually volume fraction of 0.1-0.5%) for 20-60 minutes, the specific operation method can refer to Figure 4, then washed with deionized water, excess ammonium chloride, dry at room temperature, the dried substrate is placed on the heating platform, heated at 130℃ for 20-60 minutes;

[0078] S4 (spray spacer): the above-mentioned after the substrate is placed on the dry spray equipment operating table, the diameter of the ball-shaped spacer is added to the spray hole, the spray switch is pressed for several seconds, and the spacer is deposited completely, and the operation details can be seen in Figure 5.

[0079] S5 (filling liquid crystal & packaging): the substrate with surface deposited spacer and clean substrate are covered together in the direction of "anti-parallel" of the bombardment direction, which can be referred to in Figure 6, and the long side is sealed with AB glue, and the short side is left with a gap for liquid crystal filling; after waiting for the glue to dry, the inorganic alignment substrate empty liquid crystal cell is obtained, the negative liquid crystal is filled into it, and the liquid crystal is filled into the liquid crystal cell under the action of capillary force, and the liquid crystal cell is sealed with AB glue, and the packaging of the liquid crystal cell is completed.

[0080] S6 (photographing polarized images of liquid crystal devices): A polarized microscope was used to photograph the polarized images of the liquid crystal cell. The schematic diagram of the simple structure of the polarized microscope is shown in FIG. 9. The backlight was turned on, the polarization direction of the polarizer 1 was fixed, the liquid crystal cell was placed between the polarizer 1 and the polarizer 2, the rotation angle of the polarizer 2 was adjusted to be parallel or orthogonal to the polarization direction of the polarizer 1, and the polarized images of the liquid crystal cell just prepared and after being placed for 6 months were photographed in the parallel state and the orthogonal state, respectively. After the images were collected and processed, the polarized images of the liquid crystal device prepared using the long alkyl chain ammonium chloride solution treated short bombardment time long vertical alignment substrate were obtained. Details are shown in FIG. 13. It can be seen from the figure that the substrate of the short bombardment time long film treated with the long alkyl chain ammonium chloride solution has stable vertical alignment effect after being prepared into a liquid crystal device, and the vertical alignment can still maintain good after 6 months. In the figure, 1. The ion beam bombardment angle is 45°; 2. In FIG. a, the orientation direction of the liquid crystal cell is 0° to the direction of one polarized axis, and in FIG. b, the orientation direction of the liquid crystal cell is 45° to the polarization direction; 3. The white arrows in the figure represent the polarizer P and the analyzer A; 4. The bottom graph shows the dark state phenomenon observed under the polarized light microscope (POM), and the upper right corner picture shows the dark state phenomenon observed by the naked eye between the orthogonal polarizers.

[0081] S7 (measuring the pre-tilt angle of the liquid crystal molecules in the liquid crystal device): The schematic diagram of the pre-tilt angle of the liquid crystal molecules is shown in FIG. 10. The crystal rotation method was used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal cell. The measurement light path is shown in FIG. 11. The entire test light path is composed of a laser light source, two orthogonal polarizers serving as a polarizer and an analyzer, a detector, and a rotating stage on which the test liquid crystal cell is placed. The rotating stage is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at an angle of 45° to the polarization direction of the polarizer. The liquid crystal cell is rotated around an axis perpendicular to the orientation direction and passing through the center of the liquid crystal cell. When the liquid crystal cell is rotated by a stepping motor, the information change of the outgoing light is received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertical alignment liquid crystal device prepared using the long alkyl chain ammonium chloride solution treated short bombardment time long substrate just prepared and after 6 months were collected and processed. The results are shown in FIG. 15.

[0082] Example 3

[0083] The preparation and test process of the vertical alignment liquid crystal device is shown in FIG. 1. The third preparation method of the vertical alignment liquid crystal device is as follows (the specific preparation process is shown in FIG. 7):

[0084] S1 (magnetic control sputtering film): A batch of cut ITO glass substrates (substrate size: 15*20 mm, ITO thickness: 30-50 nm, square resistance: 100-300 Ω / D) were prepared. A single optical film coating machine was used for film coating. The film coating method of the ITO glass substrate is shown in Step 1 of FIG. 2. The vacuum pressure during film coating was 3x10-3 Pa; working gas pressure 1.1 x 10 -1 Pa; Ar volume flow rate 300 sccm, O2 volume flow rate 200 sccm; working voltage 335 ± 5 V, magnetron sputtering target source and substrate at normal incidence angle film deposition, set SiO2 film layer target thickness 20-200 nm interval;

[0085] S2 (ion beam bombardment thin film): using Ar + ion source bombardment of the above SiO2 film layer, SiO2 film layer substrate and Ar + ion source orientation diagram as shown in Figure 2, Step 2, the orientation of the substrate and Ar + source at an angle, the vacuum pressure is 1.1 x 10 -3 Pa; Ar + working gas pressure 6.9 x 10 -2 Pa; working voltage 1350 V; duty cycle 85%; Ar + volume flow rate 300 sccm; bombardment time set to 300 s-1800 s. Wherein the inclination angle is set from 0 ° to 60 ° every 15 ° as an angle interval condition, and the direction along the inclination angle is defined as the bombardment direction, which can be seen in Figure 3;

[0086] S3 (long bombardment time of the glass substrate): the glass substrate bombarded by the ion beam for a long time is placed in a polytetrafluoroethylene glass cleaning rack, then placed in deionized water, set the cleaning temperature to 40 °C, the cleaning time to 20 minutes, and perform ultrasonic cleaning operation. During the cleaning process, it is necessary to pay attention to the deionized water covering the glass substrate. After ultrasonic cleaning, water change operation is required, and the same cleaning process is repeated three times. After cleaning, the cleaned substrate is taken out, the surface water stains are blown off with a nitrogen gun, and the substrate is placed in a drying oven at 120 °C for 2 hours. After the substrate is completely dried, the glass is taken out and the substrate surface temperature is reduced to room temperature;

[0087] S4 (spray spacer): the substrate after film deposition is placed on the operation table of the dry spraying equipment, and spherical spacers with a diameter of 15 μm are added to the spray hole. After pressing the spray switch for ten seconds, wait for the spacers to be completely deposited. The operation details can be seen in Figure 5.

[0088] S5 (liquid crystal filling & packaging): the substrate with deposited spacers and the cleaned substrate are covered together in the "anti-parallel" direction of the bombardment direction. Referring to Figure 6, the long side is sealed with AB glue, and the short side is left with a gap for liquid crystal filling. After waiting for the glue to dry, an inorganic alignment substrate empty liquid crystal cell is obtained. Negative liquid crystal is filled into the cell, and the cell is sealed with AB glue after the liquid crystal fills the cell under capillary action. The liquid crystal cell packaging operation is completed.

[0089] S6 (taking polarized images of liquid crystal devices): Polarized microscope was used to take polarized images of the liquid crystal cell. The schematic diagram of the simple structure of the polarized microscope is shown in Figure 9. The backlight was turned on, the polarization direction of the polarizer 1 was fixed, the liquid crystal cell was placed between the polarizer 1 and the polarizer 2, the rotation angle of the polarizer 2 was adjusted so that it was parallel or orthogonal to the polarization direction of the polarizer 1. In the parallel state and the orthogonal state, the polarized images of the liquid crystal cell just made and after being placed for 6 months were taken, respectively. After the images were collected and processed, the polarized images of the liquid crystal device prepared by using the long-time ion beam bombardment vertical alignment substrate were obtained. Details are shown in Figure 14. It can be seen from the figure that after the film layer is subjected to long-time ion beam bombardment, an inorganic film vertical alignment layer can be prepared. After the substrate using the alignment film is used to prepare a liquid crystal device, the vertical alignment effect is stable, and the retention time is long. After 6 months, the liquid crystal device still maintains good vertical alignment.

[0090] 1. The ion beam bombardment angle is 45°; 2. In Figure a, the alignment direction of the liquid crystal cell is 0° to the polarization direction of the polarizer, and in Figure b, the alignment direction of the liquid crystal cell is 45° to the polarization direction; 3. The white arrow in the figure represents the polarizer P and the analyzer A; 4. The bottom figure is the dark state phenomenon observed under the polarized light microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed by the naked eye between the orthogonal polarizers.

[0091] S7 (measuring the pre-tilt angle of the liquid crystal molecules in the liquid crystal device): The schematic diagram of the pre-tilt angle of the liquid crystal molecules is shown in Figure 10. The crystal rotation method was used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal cell. The measurement light path is shown in Figure 11. The entire test light path is composed of a laser light source, two orthogonal polarizers serving as a polarizer and an analyzer, a detector, and a rotating stage on which the test liquid crystal cell is placed. The rotating stage is located between the two orthogonal polarizers. The default bombardment direction is the alignment direction and is at an angle of 45° to the polarization direction of the polarizer. The liquid crystal cell is rotated around an axis perpendicular to the alignment direction and passing through the center of the liquid crystal cell. When the liquid crystal cell is rotated by a stepping motor, the information change of the outgoing light is received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertical alignment liquid crystal device prepared by using the long-time ion beam bombardment substrate just prepared and the measurement data after 6 months were collected and processed. The results are shown in Figure 15. It can be seen from the figure that the pre-tilt angle of the liquid crystal molecules in the liquid crystal device prepared by using the short-time ion beam bombardment thin film treated with long-alkyl chain ammonium chloride solution and the long-time ion beam bombardment thin film substrate is still maintained at more than 89° after being placed for 6 months. It is indicated that the alignment effect of the liquid crystal device prepared by using the alignment film prepared by using the two methods is stable, and the retention time is long. 1. The ion beam bombardment angle is 45°; 2. The liquid crystal device prepared by using the short-time ion beam bombardment inorganic vertical alignment film substrate has no alignment effect after being prepared for 15 days.

[0092] Example 4

[0093] The preparation and test process of the parallel orientation liquid crystal device please refer to FIG. 16, the preparation method is as follows (the specific preparation process refers to FIG. 18):

[0094] S1 (magnetic control sputtering film) : the parallel orientation film is prepared by tilting film coating, and the film coating instrument is a single optical film coating machine. First, the film coating substrate is processed, and the glass substrate with ITO on the surface is selected, the size is 15*20mm, the ITO thickness is 30-50nm, and the square resistance is 100-300Ω / □. The film coating mode of the ITO glass substrate is shown in FIG. 17, and the vacuum pressure is 3*10 -3 Pa during film coating; the working gas pressure is 1.1*10 -1 Pa; Ar + volume flow rate is 300sccm, O2 volume flow rate is 200sccm; the working voltage is 335±5V; during the film coating process, the target film thickness is set to 20-200nm, the film coating angle is changed by adjusting the angle of the tooling on the equipment film coating loading plate, 13 groups of angle conditions are set at an angle difference of 5° from 0° to 60°, and a series of thin films with different tilt angles are prepared;

[0095] S2 (processing of inorganic parallel orientation film substrate) : the glass substrate with inorganic orientation film is placed in a polytetrafluoroethylene glass cleaning rack, then placed in deionized water, the cleaning temperature is set to 40°, the cleaning time is 20 minutes, and ultrasonic cleaning operation is performed, after the process is completed, water needs to be changed, the same cleaning process is repeated three times. After cleaning, the cleaned substrate is taken out, the surface water stains are blown off with a nitrogen gun, and the substrate is placed in a drying oven at 120°C for 2 hours. After the substrate is completely dried, it is taken out, the surface temperature is reduced to room temperature, and then placed in a UV machine for ultraviolet irradiation. The setting time is 15 minutes, and after irradiation, it can be used.

[0096] S3 (spraying spacers) : the substrate after the SiO2 film is placed on the operation table of the dry spraying equipment, the spherical spacers with a diameter of 15μm are added to the spray hole, the spray switch is pressed for several seconds, and the spacers are deposited completely. The operation details can be seen in FIG. 5.

[0097] S4 (filling liquid crystal & packaging) : the substrate with spacers deposited on the surface is covered together with the cleaned substrate in the "anti-parallel" direction of the bombardment, which can be referred to FIG. 6, and the long side is sealed with AB glue, and the short side is left with a gap for liquid crystal filling. After waiting for the glue to dry, the inorganic orientation substrate empty liquid crystal cell is obtained, the positive liquid crystal is filled into it, the liquid crystal fills the liquid crystal cell under the action of capillary force, and the liquid crystal cell is sealed with AB glue, and the packaging of the liquid crystal cell is completed.

[0098] S5 (photographing polarized image of liquid crystal device): photographing polarized image of liquid crystal cell by polarized microscope, schematic diagram of simple structure of polarized microscope is shown in Figure 9, opening backlight, fixing polarization direction of polarizer 1, placing liquid crystal cell between polarizer 1 and polarizer 2, adjusting rotation angle of polarizer 2 to make it parallel or orthogonal to polarization direction of polarizer 1, photographing polarized image of liquid crystal cell just finished, after processing images, polarized image of liquid crystal device prepared by parallel orientation substrate is obtained, details are shown in Figure 19.

[0099] As shown in Figure 19, 1. taking 25° inclination as a boundary, when coating angle is less than 25°, the substrate has no obvious orientation effect, and the microscopic image obtained by changing the angle between liquid crystal cell and polarizer does not change obviously; when coating angle is greater than 25° and gradually increases, the orientation effect of liquid crystal cell gradually becomes good, under the condition of 45° coating angle, liquid crystal cell has obvious bright-dark state change, when coating angle is 60°, the orientation effect of liquid crystal cell corresponding to the substrate is best, it can be concluded that by means of magnetic control sputtering inclined coating, liquid crystal is oriented, the inclined coating angle is positively correlated with the orientation performance of the prepared liquid crystal device, under the condition of large coating inclination, inorganic orientation film with parallel orientation is obtained, at this time, the coating inclination should be greater than 25°. 2. in Figure (a~d, i~l, q~t, y), the orientation direction of liquid crystal cell is 0° to polarization direction, in Figure (e~h, m~p, u~x, z), the orientation direction of liquid crystal cell is 45° to polarization direction; 3. white arrow in the figure represents polarizer P and analyzer A; 4. bottom graph is dark state phenomenon observed under polarized microscope (POM), and the picture in the upper right corner is dark state phenomenon observed by naked eye between orthogonal polarizers.

[0100] S6 (measuring the pre-tilt angle of liquid crystal molecules in a liquid crystal device): The liquid crystal molecule pre-tilt angle schematic diagram can be seen in FIG. 10, and the crystal rotation method is used to measure the pre-tilt angle of liquid crystal molecules in a liquid crystal cell. The measurement light path is shown in FIG. 11, and the entire test light path is composed of a laser light source, two orthogonal polarizers serving as a polarizer and an analyzer, a detector, and a rotating stage on which the test liquid crystal cell is placed. The rotating stage is located between the two orthogonal polarizers, the default bombardment direction is the orientation direction and is at an angle of 45° with the polarization direction of the polarizer, the liquid crystal cell is rotated around an axis perpendicular to the orientation direction and passing through the center of the liquid crystal cell, and the information change of the outgoing light generated when the liquid crystal cell is rotated by a stepping motor is received by the detector and transmitted back to the computer for processing and calculation. When the pre-tilt angle is tested, the bombardment direction of the test substrate is placed along the rotating direction of the rotating stage, that is, the default long axis direction of the liquid crystal molecules is arranged along the bombardment direction. The pre-tilt angle of the liquid crystal cell with orientation effect is tested, that is, the film tilt angle of the test cell is greater than or equal to 30°, and 3-5 test points are selected on each liquid crystal cell for testing. The experimental results show that the long axis direction of the liquid crystal molecules is arranged along the inclined direction of the substrate film, and the pre-tilt angle and the angle change relationship are shown in FIG. 20.

[0101] According to the pre-tilt angle test curve in FIG. 20, the overall test value of the pre-tilt angle is smaller after the liquid crystal cell has the orientation effect, and the pre-tilt angle suddenly decreases after the tilt angle reaches 45°. At this time, the orientation effect of the liquid crystal cell is more obvious under the observation of the polarizing microscope. Although a smaller molecular pre-tilt angle can obtain a faster response time, it is too small for the pre-tilt angle requirement (about 3°-5°) of a general parallel orientation cell.

[0102] Effect example 1

[0103] Orientation forming mechanism

[0104] Regarding the vertical orientation, the present application performs AFM (Atomic Force Microscopy) scanning on the inorganic thin film without bombardment and the inorganic vertical orientation thin film with long bombardment time and large bombardment angle, and finds that there is no obvious change in the film layer morphology on the substrate surface before and after ion beam treatment, and only granular structure can be observed. Details can be seen in FIG. 21. Subsequently, the present application introduces XPS (X-ray Photoelectron Spectroscopy) to analyze the element structure on the surface of the orientation layer. As can be seen from the experimental data in FIG. 22 and FIG. 23, the peak intensity of Si element in the full spectrum decreases, and the proportion of Si-O bond in the fine spectrum decreases, which is consistent with the experimental results of the reported literature. It can be considered that the ion beam changes the bonding structure on the surface of the SiO2 thin film, affects the van der Waals force between the thin film surface and the liquid crystal molecules, and thus induces the directional arrangement of the liquid crystal to form the vertical orientation.

[0105] Regarding the parallel orientation, the surface topography of the substrate with different film deposition angles obtained by the inclined film deposition is scanned by AFM (Atomic Force Microscopy). As can be seen from the scanning result of FIG. 24, the substrate with 0° film deposition has many undirectional granular structures on the surface of the orientation film due to the absence of the introduction of anisotropy source; with the increase of the deposition angle, and when the film deposition angle reaches 45°, the substrate surface appears a friction-like strip-shaped undulatory structure with a specific directionality. It can be considered that the orientation mechanism of the parallel orientation is that the inclined deposition of the inorganic material makes the substrate surface produce a "groove-like" undulatory topography, and the liquid crystal molecules arrange along the direction of avoiding the additional elastic strain energy to maintain the stable state with the lowest energy, i.e. parallel to the groove direction, thereby producing the orientation effect.

[0106] The above only discloses preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so the equivalent changes made according to the claims of the present application still fall within the scope of the present application.

Claims

1. A method for preparing a liquid crystal alignment layer based on an inorganic thin film, characterized in that, The orientation of the liquid crystal alignment layer shown includes one or more of vertical and parallel orientations; When the orientation of the liquid crystal alignment layer includes vertical orientation, the preparation method includes: S1. A coating layer is formed by sputtering a substrate. S2. The coating layer is then bombarded to obtain the liquid crystal alignment layer; When the orientation of the liquid crystal alignment layer includes parallel orientation, the preparation method includes: A. depositing a film on the substrate by sputtering at an inclined sputtering angle greater than 25° to obtain the liquid crystal alignment layer.

2. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1, characterized in that, When the orientation of the liquid crystal alignment layer includes vertical orientation, in step S2, the bombardment includes one or more of short-duration bombardment and long-duration bombardment; the bombardment time of the short-duration bombardment is no longer than 300s; the bombardment time of the long-duration bombardment is 300s-1800s; the bombardment angle includes multi-angle bombardment from 0° to 60°.

3. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 2, characterized in that, The bombardment angles include multi-angle bombardment ranging from 0° to 60° with 15° intervals; when the bombardment is the short-duration bombardment, step S2 further includes: after the short-duration bombardment ends, the liquid crystal alignment layer is treated with a long alkyl chain ammonium chloride solution.

4. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 3, characterized in that, The operation of the long alkyl chain ammonium chloride solution treatment includes: immersing the liquid crystal alignment layer in a diluted aqueous solution of long alkyl chain ammonium chloride with a volume fraction of 0.1-0.5% for 20-60 minutes, rinsing with deionized water, air-drying at room temperature, and then heating at 130°C for 20-60 minutes.

5. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1, characterized in that, When the orientation of the liquid crystal alignment layer includes a vertical orientation, in step S1, the tilting sputtering angle is 0°; when the orientation of the liquid crystal alignment layer includes a parallel orientation, in step A, the tilting sputtering angle is greater than 45°.

6. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1, characterized in that, When the orientation of the liquid crystal alignment layer includes a parallel orientation, in step A, the tilting sputtering angle is 60°.

7. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1, characterized in that, The sputtering includes magnetron sputtering; the bombardment includes plasma bombardment.

8. The method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1, characterized in that, The conditions for magnetron sputtering include: the target material is a Si target, and the vacuum pressure is 3 × 10⁻⁶. -3 Pa, working air pressure 1.1×10 -1 Pa, Ar volumetric flow rate 300 sccm, O2 volumetric flow rate 200 sccm, operating voltage 335±5V, forming a SiO2 film layer with a thickness of 20-200 nm on the substrate; the plasma bombardment conditions include: the ion source is Ar + Vacuum pressure 1.1×10 -3 Pa,Ar + Working air pressure 6.9×10 -2 Pa, operating voltage 1350V, duty cycle 85%, Ar + Volumetric flow rate: 300 sccm.

9. A liquid crystal alignment layer obtained by the method for preparing a liquid crystal alignment layer based on an inorganic thin film as described in claim 1.

10. An application of the liquid crystal alignment layer as described in claim 9, characterized in that, Used in the manufacture of liquid crystal display devices.

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