Preparation method of liquid crystal orientation layer based on inorganic film

Abstract

The invention provides an inorganic film orientation technology which can realize stable and high-contrast vertical orientation and can also realize a good parallel orientation effect only on the basis of a coating mode and a single coating material system, and relates to a preparation method of orientation films in two orientation directions. Firstly, the inorganic material vertical alignment film with specific thickness and morphology can be prepared by regulating and controlling the magnetron sputtering conditions, the duration of plasma bombardment of the SiO2-like inorganic material film and the bombardment angle, and the liquid crystal device is prepared by performing different treatments on the inorganic vertical alignment film substrates with different bombardment durations; the vertical alignment effect on the liquid crystal can be realized, but few differences exist. Secondly, the substrate is coated at a specific angle by adopting a magnetron sputtering method, so that the inorganic film parallel orientation layer of the liquid crystal can be prepared; by regulating and controlling the preparation conditions, when the inclined sputtering coating angle is larger than 25 degrees, the orientation layer can achieve the parallel orientation effect on liquid crystals.

Description

Technical Field

[0001] The invention belongs to the field of liquid crystal display technology, and proposes an inorganic orientation technology based on the application of plasma bombardment and magnetron sputtering integrated equipment, using inorganic thin film materials to prepare liquid crystal orientation layers. The technology involves a preparation method of orientation films in two orientation directions. Background Art

[0002] Liquid crystal display devices, generally referred to as LCD (Liquid Crystal Display), are involved in all aspects of life, including clocks, calculators, televisions, word processors, personal computers, video phones, etc. LCD is increasingly widely used in various fields due to its low power consumption, small size, light weight, large amount of information display, and ability to display various types of information, such as characters, graphics (including Chinese characters, curves, tables, etc.), especially in portable devices, where it occupies an absolute mainstream position.

[0003] In the process production of liquid crystal display devices, the orientation of liquid crystal molecules plays an important role, and the quality of the orientation effect greatly affects the performance of liquid crystal display devices. As a product of the combination of semiconductor integrated circuits and liquid crystal displays, liquid crystal on silicon (LCoS) can effectively play the high integration advantages of integrated circuit technology and make full use of the advanced process conditions of the semiconductor industry. It provides the possibility for miniaturization, ultra-high resolution and low power consumption of light control devices, and is widely used in many fields such as display, wavefront correction, light field control, etc., 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. The friction method is widely used in industrial production because of its mature process and simple operation. However, the static electricity generated during the operation and the groove defects left by friction have brought certain limitations to the use of the friction method. There are many categories in the non-contact method, such as light control method, polyimide LB film orientation method, etc. However, these orientation methods all use polymer organic film as an orientation layer to act on liquid crystal molecules to induce the orientation of liquid crystal molecules. The characteristics of polymer organic matter cause the orientation layer to produce film performance changes when the temperature, humidity or other environmental conditions change, resulting in changes in the liquid crystal orientation ability, affecting the life of the liquid crystal device. Therefore, some methods of using inorganic substances to prepare liquid crystal orientation layers are generated, which also provides the possibility for the application of liquid crystal devices in working environments facing ultraviolet modulation and high-energy lasers, and provides a solution for the development of LCoS (Liquid Crystal on Silicon) devices.

[0005] In the 1980s, some people used vacuum deposition to deposit inorganic materials such as metals, oxides, and fluorides on a tilted substrate. This tilted evaporation orientation method also achieved the orientation effect of friction technology. Its tilted deposition at a certain angle will produce a directional arrangement for the liquid crystal molecules; this orientation method is called tilted evaporation. The oriented film obtained in this way has good light and heat stability, and the optoelectronic devices made have high contrast and good uniformity. At the same time, some people proposed the use of ion beam treatment of the surface layer of inorganic thin films to produce an orientation method for the liquid crystal orientation layer. This type of orientation method has the characteristics of resistance to repeated cleaning and baking, and is suitable for production and application in combination with vacuum deposition equipment.

[0006] In addition to the above two orientation methods, other methods involving inorganic materials in orientation include nanoparticle doping or self-assembly, diamond friction orientation, etc. However, since these methods are relatively complicated in the operation and preparation process, they have not been widely used in actual industrial applications. Summary of the invention

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

[0008] The present invention proposes an inorganic orientation technology for preparing a liquid crystal orientation layer based on an integrated device of plasma bombardment and magnetron sputtering, and the technology involves a method for preparing two orientation films in the orientation direction. The present invention can prepare an inorganic material vertical orientation film of a specific thickness and morphology by adjusting the magnetron sputtering conditions, the duration of plasma bombardment of SiO2-like inorganic material films, and the bombardment angle. Liquid crystal devices made by using inorganic vertical orientation film substrates with different bombardment durations and different treatments can achieve a vertical orientation effect on liquid crystals. Through testing means, it is known that there are slight differences in the liquid crystal orientation effects of the three vertical orientation liquid crystal devices; first, the liquid crystal device prepared by using a substrate of an inorganic vertical orientation film with a short bombardment duration will produce a phenomenon of orientation effect degradation after being placed for a certain period of time; second, the liquid crystal device prepared by soaking the substrate of an inorganic vertical orientation film with a short bombardment duration in a long alkyl chain ammonium chloride solution has a stable vertical orientation effect and a long retention time; third, the liquid crystal device prepared by using a substrate of an inorganic vertical orientation film with a long bombardment duration also has a stable vertical orientation effect and a long retention time. The present invention is based on integrated equipment of plasma bombardment and magnetron sputtering, and adopts magnetron sputtering method to coat the substrate at a specific angle, so as to prepare an inorganic film parallel orientation layer of liquid crystal; by adjusting the preparation conditions, when the thin film orientation layer substrate prepared at an inclined sputtering angle greater than 25 degrees is made into a liquid crystal device, a parallel orientation effect of liquid crystal can be achieved.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

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

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

[0012] S1, coating the substrate by sputtering to form a coating layer;

[0013] S2, bombarding the coating layer to obtain the liquid crystal alignment layer;

[0014] When the orientation of the liquid crystal alignment layer includes a parallel orientation, the preparation method includes: A. coating a substrate by sputtering at an inclined sputtering angle greater than 25° to obtain the liquid crystal alignment layer.

[0015] The present invention is based on the same inorganic film system and a single device, and can achieve the acquisition of two oriented film directions. The present invention is a brand-new preparation method that does not require replacement of equipment or film system, greatly reducing the acquisition cost of different oriented films and simplifying the acquisition process.

[0016] The present invention discloses an integrated device based on plasma bombardment and magnetron sputtering. The inorganic orientation layer preparation technology with liquid crystal orientation effect can be realized by only adjusting the duration and bombardment angle of plasma bombardment of SiO2-like inorganic material thin film. By adjusting the preparation conditions, an inorganic material thin film with a specific thickness and morphology can be prepared, and a liquid crystal device prepared using a substrate of the inorganic thin film can achieve an orientation effect on liquid crystal. Based on the device, an inorganic material thin film orientation layer based on a single film system can be prepared. By adjusting the preparation conditions, both an inorganic thin film vertical orientation layer and an inorganic thin film parallel orientation layer can be obtained.

[0017] The technology of the present invention is based on the integrated equipment of magnetron sputtering and ion beam bombardment to realize the preparation of two types of oriented thin film substrates: vertical orientation and parallel orientation. Regarding the inorganic vertical orientation film, the present invention uses a method combining magnetron sputtering and ion beam bombardment. The substrate and the target material are first placed in parallel, and a layer of inorganic thin film is formed on the substrate by magnetron sputtering. Then, an ion source is used to bombard the film layer on the substrate at a specific angle and for a specific time to obtain a vertically oriented inorganic thin film. Regarding the inorganic parallel orientation film, the present invention first places the target material and the substrate at a certain angle, and then uses the magnetron sputtering method to form a layer of inorganic thin film on the substrate. The film layer has a parallel orientation effect on the liquid crystal molecules.

[0018] By using magnetron sputtering to coat the substrate at a specific angle, an inorganic film parallel orientation layer of liquid crystal can be prepared. In the magnetron sputtering process, the inorganic film parallel orientation layer prepared by fixing the substrate position or rotating the substrate can achieve the parallel arrangement orientation effect of liquid crystal after the thin film orientation layer is made into a liquid crystal device by adjusting the preparation conditions. There is a certain angle threshold for the inorganic orientation layer to achieve parallel orientation. Only when the tilted sputtering angle is greater than 25 degrees can the effect of parallel orientation of liquid crystal be achieved. Taking 25° as the boundary, when the coating angle is less than 25°, the substrate has no obvious orientation effect, and the microscopic image obtained when changing the angle between the liquid crystal box and the polarizer does not change significantly; when the coating angle is greater than 25° and gradually increases, it is observed that the orientation effect of the liquid crystal box gradually improves. Therefore, the parallel orientation coating tilt angle is greater than 25°.

[0019] Preferably, when the orientation of the liquid crystal orientation layer includes a 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 not 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°.

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

[0021] The bombardment inclination angle is set from 0° to 60°, preferably with an angle interval of 15°, so that multi-angle bombardment is performed.

[0022] Preferably, the long alkyl chain ammonium chloride solution treatment operation 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 to 0.5% for 20 to 60 minutes, then rinsing with deionized water, drying at room temperature, and heating at 130° C. for 20 to 60 minutes after drying.

[0023] The inorganic thin film prepared by magnetron sputtering can be used to prepare a vertical orientation layer of an inorganic material thin film for liquid crystal after the inorganic thin film layer is bombarded by an ion beam for a short time. After a liquid crystal device is made using a substrate of the orientation film, the vertical orientation effect is unstable and the orientation effect will deteriorate after being left for a certain period of time.

[0024] The inorganic oriented film made by magnetron sputtering coating combined with short-time ion beam bombardment of the film layer can achieve a relatively stable vertical orientation effect of long-term ion beam bombardment of the inorganic vertical orientation film after being treated with a long alkyl chain ammonium chloride solution. The substrate of the thin film treated by this method, after being made into a liquid crystal device, has a stable vertical orientation effect of the device, and the good orientation effect is maintained for a long time.

[0025] The inorganic thin film prepared by magnetron sputtering can prepare an inorganic film vertical orientation layer after the film layer is bombarded by ion beam for a long time. After the liquid crystal device is made using the substrate of the orientation film, the vertical orientation effect is stable and maintained for a long time.

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

[0027] By using magnetron sputtering to coat the substrate in a direction of 0 degrees to the substrate normal, and then bombarding the coated layer with ion beams at a specific inclination angle and for a specific time, an inorganic film vertical orientation layer can be prepared. A liquid crystal device is made using the inorganic thin film orientation substrate, and the device can achieve the effect of vertical orientation of liquid crystals.

[0028] Liquid crystals are oriented by magnetron sputtering tilted coating. The tilted coating angle is positively correlated with the orientation performance of the liquid crystal device. Under the condition of a large coating tilt angle, an inorganic oriented film with parallel orientation is obtained. At this time, the coating tilt angle should be greater than 25°. Under the coating angle of 45°, the liquid crystal box has a more obvious change in light and dark states. When the coating angle is 60°, the orientation effect of the liquid crystal box corresponding to the substrate is the best.

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

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

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

[0032] The target material of the present invention is a Si target, and the principle is that the diffused Si reacts with the doped O in the space to form a SiO2 film on the surface of the substrate.

[0033] The working pressure of the present invention during magnetron sputtering coating is 1.1×10 -1 Pa, the working gas pressure during ion beam bombardment is 6.9×10 -2 Pa.

[0034] A liquid crystal alignment layer obtained by the above-mentioned method for preparing a liquid crystal alignment layer based on an inorganic thin film.

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

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

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

[0038] The present invention proposes an inorganic thin film orientation technology that can achieve stable, high-contrast vertical orientation and good parallel orientation effects based on only one coating method and a single coating material system. The technology involves a method for preparing two orientation direction orientation films. With respect to inorganic vertical orientation films, the present invention can prepare inorganic material vertical orientation films of specific thickness and morphology by adjusting magnetron sputtering conditions, the duration of plasma bombardment of SiO2-like inorganic material films, and the bombardment angle. Liquid crystal devices made by using inorganic vertical orientation film substrates with different bombardment durations and different treatments can achieve vertical orientation effects on liquid crystals, but there are slight differences. With respect to inorganic parallel orientation films, the present invention is based on an integrated device of plasma bombardment and magnetron sputtering, and uses magnetron sputtering to coat substrates at a specific angle to prepare an inorganic film parallel orientation layer of liquid crystals; by adjusting the preparation conditions, when the inorganic thin film parallel orientation layer substrate is prepared at an inclined sputtering angle greater than 25 degrees, after being made into a liquid crystal device, it can achieve a parallel orientation effect on liquid crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of the preparation and testing of a liquid crystal device of an inorganic vertical alignment film substrate.

[0040] Figure 2It is a schematic diagram of the preparation process of the bombardment inorganic vertical alignment film of the present invention.

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

[0042] Figure 4 It is a schematic diagram of the immersion operation of the inorganic vertical alignment film substrate of the present invention.

[0043] Figure 5 It is a schematic diagram of the spraying spacer of the inorganic alignment film substrate of the present invention.

[0044] Figure 6 The figure is a schematic diagram of a liquid crystal device made of the inorganic alignment film substrate of the present invention.

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

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

[0047] Fig. 9 The figure is a schematic diagram of the simplified structure of a polarizing microscope for photographing polarized images of a liquid crystal device according to the present invention.

[0048] Fig.10 It is a schematic diagram of the pre-tilt angle of liquid crystal molecules in the liquid crystal device of the present invention.

[0049] Fig.11 It is a schematic diagram of the optical path for pre-tilt angle testing of the liquid crystal device of the present invention.

[0050] Fig.12 This is a polarized image of a liquid crystal device prepared using the inorganic vertical alignment film substrate with a short bombardment time of the present invention.

[0051] Fig.13 The polarized image is a liquid crystal device prepared by treating the inorganic vertical alignment film substrate with a short bombardment time with a long alkyl chain ammonium chloride solution.

[0052] Fig.14 This is a polarized image of a liquid crystal device prepared using the inorganic vertical alignment film substrate with a long bombardment time of the present invention.

[0053] Fig.15 The pre-tilt angle test result of the liquid crystal device prepared by the inorganic vertical alignment film substrate of the present invention.

[0054] Fig.16 The present invention is a flow chart of the preparation and testing of the inorganic parallel alignment film substrate liquid crystal device.

[0055] Fig.17It is a schematic diagram of the preparation of the inorganic parallel oriented film of the present invention.

[0056] Fig.18 The schematic diagram of preparing a liquid crystal device using the inorganic parallel alignment film substrate of the present invention.

[0057] Fig.19 This is a diagram showing the dependence of the orientation effect of a liquid crystal device made of an inorganic parallel orientation film substrate of the present invention on the coating angle.

[0058] Fig. 20 The present invention provides a curve showing the change of the pre-tilt angle of a liquid crystal device prepared by the parallel alignment film substrate according to the present invention as a function of the coating tilt angle.

[0059] Fig.21 AFM 2D scanning images of the substrate surface. (a) The surface of an inorganic thin film without bombardment; (b) The surface of an inorganic vertically oriented thin film with a long bombardment time and a large bombardment angle.

[0060] Fig. 22 This is a comparison chart of XPS full spectrum test data of the inorganic vertical orientation layer surface.

[0061] Fig.23 This is a comparison chart of XPS fine spectrum test data of the inorganic vertical orientation layer surface.

[0062] Fig.24 AFM 2D scans of the surface of the tilted film-coated substrate. The coating tilt angle is (a) 0°; (b) 45°. DETAILED DESCRIPTION

[0063] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0064] Example 1

[0065] For the preparation and testing process of vertically aligned liquid crystal devices, please refer to Figure 1 The first method for preparing a vertically aligned liquid crystal device is as follows (refer to the specific preparation process Figure 7 ):

[0066] S1 (magnetron sputtering 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 coating instrument used is a single optical coating machine. The coating method of ITO glass substrate is as follows: Figure 2 As shown in Step 1, the vacuum pressure during coating is 3×10 -3 Pa; working pressure 1.1×10 - 1Pa; Ar volume flow rate is 300sccm, O2 volume flow rate is 200sccm; working voltage is 335±5V, magnetron sputtering target source and substrate are deposited at a normal incidence angle, and the target thickness of SiO2 film layer is set in the range of 20-200nm;

[0067] S2 (ion beam bombardment of film): using Ar + The ion source bombards the SiO2 film layer, and the SiO2 film substrate and Ar + Schematic diagram of ion source orientation Figure 2 As shown in Step 2, the oriented substrate and Ar + The source is at a certain angle, and the vacuum pressure during bombardment is 1.1×10 -3 Pa; Ar + The working pressure is 6.9×10 -2 Pa; working voltage 1350V; duty cycle 85%; Ar + The volume flow rate is 300sccm; the bombardment time is set to no longer than 300s. The bombardment inclination angle is set to an angle interval of 15° from 0° to 60°, and the bombardment direction is set to the upward direction along the inclination angle. Figure 3 ;

[0068] S3 (Processing method 1 for long substrates with short bombardment time): Place the glass substrate bombarded by the ion beam for a short time into a polytetrafluoroethylene glass cleaning rack, and then place it in deionized water. Set the cleaning temperature to 40°C, the cleaning time to 20 minutes, and perform ultrasonic cleaning. During the cleaning process, it is necessary to pay attention to the deionized water to cover the glass substrate. After the ultrasonic cleaning is completed, the water needs to be changed, and the same cleaning process is repeated three times. After cleaning, take out the cleaned substrate, blow off the water stains on the surface with a nitrogen gun, put it in a drying oven at 120°C for 2 hours, and take out the glass after the substrate is completely dry, and wait for the surface temperature of the substrate to drop to room temperature;

[0069] S4 (spraying spacers): Place the above-coated substrate on the operating table of the dry spray equipment, add spherical spacers with a diameter of 15μm into the spray hole, press and hold the spray switch for more than ten seconds, and wait for the spacers to be completely deposited. For details of the operation, see Figure 5 .

[0070] S5 (liquid crystal injection & packaging): Cover the coated surface with the substrate with spacers deposited on the surface and the cleaned substrate in an anti-parallel bombardment direction. For details, please refer to Figure 6 , and then use AB glue to seal the long sides, leaving gaps on the short sides for liquid crystal injection; after waiting for the glue to dry, an empty liquid crystal box of the inorganic orientation substrate is obtained, and negative liquid crystal is injected into it. After the liquid crystal fills the liquid crystal box under capillary action, the liquid crystal box is sealed with AB glue to complete the packaging operation of the liquid crystal box.

[0071] S6 (capturing polarized images of liquid crystal devices): polarized images of liquid crystal boxes are captured using a polarized microscope. The schematic diagram of the simple structure of the polarized microscope is shown in the figure below. Fig. 9 As shown, turn on the backlight plate, fix the polarization direction of polarizer 1 unchanged, place the liquid crystal box between polarizer 1 and polarizer 2, adjust the rotation angle of polarizer 2 to make it parallel or orthogonal to the polarization direction of polarizer 1, and take polarization images of the liquid crystal box just made and after 15 days of placement in the parallel state and the orthogonal state, respectively. After summarizing the images, the polarization images of the liquid crystal device made of the short bombardment time long vertical alignment substrate are obtained. For details, see Fig.12 It can be seen from the figure that the vertical orientation effect is good when it is just made. After 15 days, the orientation effect becomes worse, indicating that the orientation effect of the liquid crystal device deteriorates after being placed for a certain period of time. Among them, 1. The ion beam bombardment inclination angle is 45°; 2. The orientation of the liquid crystal box in Figure a is 0° to the direction of the first polarization axis, and the orientation direction of the liquid crystal box in Figure b is 45° to the polarization direction; 3. The white arrows in the figure indicate the polarizer P and the analyzer A; 4. The bottom picture is the dark state phenomenon observed under a polarizing microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed by the naked eye between the orthogonal polarizers.

[0072] S7 (measurement of the pre-tilt angle of liquid crystal molecules in liquid crystal devices): the schematic diagram of the pre-tilt angle of liquid crystal molecules can be seen Fig.10 The crystal rotation method is used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal box. The measurement optical path is as follows: Fig.11 As shown, the entire test optical route consists of a laser light source, two orthogonal polarizers that act as a polarizer and an analyzer, a detector, and a rotating table on which the test liquid crystal box is placed. The rotating table is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at a 45° angle to the polarization direction of the polarizer. The liquid crystal box rotates around an axis that is perpendicular to the orientation direction and passes through the center of the liquid crystal box. When the liquid crystal box is driven by a stepper motor to rotate, the information changes of the outgoing light generated are received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertically oriented liquid crystal device made with a short bombardment time and long substrate just prepared and the measurement data 6 months later are summarized and processed, and the results are shown as follows. Fig.15 shown.

[0073] Example 2

[0074] For the preparation and testing process of vertically aligned liquid crystal devices, please refer to Figure 1 The second method for preparing a vertically aligned liquid crystal device is as follows (refer to the specific preparation process Figure 8 ):

[0075] S1 (magnetron sputtering coating): 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 coating instrument used is a single optical coating machine. The coating method of ITO glass substrate is as follows: Figure 2 As shown in Step 1, the vacuum pressure during coating is 3×10 -3 Pa; working pressure 1.1×10 -1 Pa; Ar volume flow rate is 300sccm, O2 volume flow rate is 200sccm; working voltage is 335±5V, magnetron sputtering target source and substrate are deposited at a normal incidence angle, and the target thickness of SiO2 film layer is set in the range of 20-200nm;

[0076] S2 (ion beam bombardment of film): using Ar + The ion source bombards the SiO2 film layer, and the SiO2 film substrate and Ar + Schematic diagram of ion source orientation Figure 2 As shown in Step 2, the oriented substrate and Ar + The source is at a certain angle, and the vacuum pressure during bombardment is 1.1×10 -3 Pa; Ar + The working pressure is 6.9×10 -2 Pa; working voltage 1350V; duty cycle 85%; Ar + The volume flow rate is 300sccm; the bombardment time is set to no longer than 300s. The bombardment inclination angle is set to an angle interval of 15° from 0° to 60°, and the bombardment direction is set to the upward direction along the inclination angle. Figure 3 ;

[0077] S3 (Short bombardment time long substrate treatment method 2): Immerse the glass substrate bombarded by the ion beam for a short time in a dilute aqueous solution of long alkyl chain ammonium chloride (usually 0.1-0.5% by volume) for 20-60 minutes. The specific operation method can be referred to Figure 4 , then rinse the excess ammonium chloride with deionized water, dry it at room temperature, place the dried substrate on a heating table, and heat it at 130°C for 20-60 minutes;

[0078] S4 (spraying spacers): Place the above-coated substrate on the operating table of the dry spray equipment, add spherical spacers with a diameter of 15μm into the spray hole, press and hold the spray switch for more than ten seconds, and wait for the spacers to be completely deposited. For details of the operation, see Figure 5 .

[0079] S5 (liquid crystal injection & packaging): Cover the coated surface with the substrate with spacers deposited on the surface and the cleaned substrate in an anti-parallel bombardment direction. For details, please refer to Figure 6 , and then use AB glue to seal the long sides, leaving gaps on the short sides for liquid crystal injection; after waiting for the glue to dry, an empty liquid crystal box of the inorganic orientation substrate is obtained, and negative liquid crystal is injected into it. After the liquid crystal fills the liquid crystal box under capillary action, the liquid crystal box is sealed with AB glue to complete the packaging operation of the liquid crystal box.

[0080] S6 (capturing polarized images of liquid crystal devices): polarized images of liquid crystal boxes are captured using a polarized microscope. The schematic diagram of the simple structure of the polarized microscope is shown in the figure below. Fig. 9 As shown, the backlight panel is turned on, the polarization direction of polarizer 1 is fixed unchanged, the liquid crystal box is placed between polarizer 1 and polarizer 2, and the rotation angle of polarizer 2 is adjusted to make it parallel or orthogonal to the polarization direction of polarizer 1. In the parallel state and the orthogonal state, the polarization images of the liquid crystal box are taken when it is just made and after being placed for 6 months, respectively. After summarizing the images, the polarization images of the liquid crystal device made of the short bombardment time long vertical alignment substrate treated with long alkyl chain ammonium chloride solution are obtained. For details, see Fig.13 , it can be seen from the figure that after the long alkyl chain ammonium chloride solution was used to bombard the long film substrate, the vertical orientation effect of the device was stable after it was made into a liquid crystal device, and it could still maintain a good vertical orientation after 6 months. Among them, 1. The ion beam bombardment inclination angle is 45°; 2. The orientation of the liquid crystal box in Figure a is 0° to the direction of the first polarization axis, and the orientation direction of the liquid crystal box in Figure b is 45° to the polarization direction; 3. The white arrows in the figure indicate the polarizer P and the analyzer A; 4. The bottom picture is the dark state phenomenon observed under a polarizing microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed by the naked eye between the orthogonal polarizers.

[0081] S7 (measurement of the pre-tilt angle of liquid crystal molecules in liquid crystal devices): the schematic diagram of the pre-tilt angle of liquid crystal molecules can be seen Fig.10 The crystal rotation method is used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal box. The measurement optical path is as follows: Fig.11 As shown, the entire test optical path consists of a laser light source, two orthogonal polarizers that serve as a polarizer and an analyzer, a detector, and a rotating table on which the test liquid crystal box is placed. The rotating table is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at a 45° angle to the polarization direction of the polarizer. The liquid crystal box rotates around an axis that is perpendicular to the orientation direction and passes through the center of the liquid crystal box. When the liquid crystal box is driven by a stepper motor to rotate, the information changes of the outgoing light generated are received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertically oriented liquid crystal device made of a short bombardment time long substrate that has just been prepared and treated with a long alkyl chain ammonium chloride solution and the measurement data 6 months later are summarized and processed, and the results are shown as follows. Fig.15 shown.

[0082] Example 3

[0083] For the preparation and testing process of vertically aligned liquid crystal devices, please refer to Figure 1 The third method for preparing a vertically aligned liquid crystal device is as follows (refer to the specific preparation process Figure 7 ):

[0084] S1 (magnetron sputtering coating): 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 coating instrument used is a single optical coating machine. The coating method of ITO glass substrate is as follows: Figure 2 As shown in Step 1, the vacuum pressure during coating is 3×10 -3 Pa; working pressure 1.1×10 - 1 Pa; Ar volume flow rate is 300sccm, O2 volume flow rate is 200sccm; working voltage is 335±5V, magnetron sputtering target source and substrate are deposited at a normal incidence angle, and the target thickness of SiO2 film layer is set in the range of 20-200nm;

[0085] S2 (ion beam bombardment of film): using Ar + The ion source bombards the SiO2 film layer, and the SiO2 film substrate and Ar + Schematic diagram of ion source orientation Figure 2 As shown in Step 2, the oriented substrate and Ar + The source is at a certain angle, and the vacuum pressure during bombardment is 1.1×10 -3 Pa; Ar + The working pressure is 6.9×10 -2 Pa; working voltage 1350V; duty cycle 85%; Ar + The volume flow rate is 300sccm; the bombardment time is set to 300s-1800s. The bombardment inclination angle is set to an angle interval of 15° from 0° to 60°, and the bombardment direction is set to the upward direction along the inclination angle. Figure 3 ;

[0086] S3 (treatment of substrates with long bombardment time): put the glass substrate bombarded by the ion beam for a long time into a polytetrafluoroethylene glass cleaning rack, and then place it in deionized water, set the cleaning temperature to 40°C, the cleaning time to 20 minutes, and perform ultrasonic cleaning. During the cleaning process, it is necessary to pay attention to the deionized water to cover the glass substrate. After the ultrasonic cleaning is completed, the water needs to be changed, and the same cleaning process is repeated three times. After cleaning, take out the cleaned substrate, blow off the water stains on the surface with a nitrogen gun, put it in a drying oven at 120°C for 2 hours, and take out the glass after the substrate is completely dry, and wait for the surface temperature of the substrate to drop to room temperature;

[0087] S4 (spraying spacers): Place the above-coated substrate on the operating table of the dry spray equipment, add spherical spacers with a diameter of 15μm into the spray hole, press and hold the spray switch for more than ten seconds, and wait for the spacers to be completely deposited. For details of the operation, see Figure 5 .

[0088] S5 (liquid crystal injection & packaging): Cover the coated surface with the substrate with spacers deposited on the surface and the cleaned substrate in an anti-parallel bombardment direction. For details, please refer to Figure 6 , and then use AB glue to seal the long sides, leaving gaps on the short sides for liquid crystal injection; after waiting for the glue to dry, an empty liquid crystal box of the inorganic orientation substrate is obtained, and negative liquid crystal is injected into it. After the liquid crystal fills the liquid crystal box under capillary action, the liquid crystal box is sealed with AB glue to complete the packaging operation of the liquid crystal box.

[0089] S6 (capturing polarized images of liquid crystal devices): polarized images of liquid crystal boxes are captured using a polarized microscope. The schematic diagram of the simple structure of the polarized microscope is shown in the figure below. Fig. 9 As shown, the backlight panel is turned on, the polarization direction of polarizer 1 is fixed unchanged, the liquid crystal box is placed between polarizer 1 and polarizer 2, and the rotation angle of polarizer 2 is adjusted to make it parallel or orthogonal to the polarization direction of polarizer 1. In the parallel state and the orthogonal state, the polarization images of the liquid crystal box are taken when it is just made and after being placed for 6 months, respectively. After summarizing the images, the polarization images of the liquid crystal device made of the long vertical alignment substrate with a long bombardment time are obtained. For details, see Fig.14 It can be seen from the figure that after the film layer is bombarded by the ion beam for a long time, an inorganic film vertical alignment layer can be prepared. After the liquid crystal device is made using the substrate of the alignment film, the vertical alignment effect is stable and lasts for a long time. After 6 months, it can still maintain a good vertical alignment.

[0090] . Among them, 1. The ion beam bombardment inclination angle is 45°; 2. The orientation of the liquid crystal box in Figure a is 0° to the direction of the first polarization axis, and the orientation direction of the liquid crystal box in Figure b is 45° to the polarization direction; 3. The white arrows in the figure represent the polarizer P and the analyzer A; 4. The bottom picture is the dark state phenomenon observed under a polarizing microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed by the naked eye between orthogonal polarizers.

[0091] S7 (measurement of the pre-tilt angle of liquid crystal molecules in liquid crystal devices): the schematic diagram of the pre-tilt angle of liquid crystal molecules can be seen Fig.10 The crystal rotation method is used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal box. The measurement optical path is as follows: Fig.11As shown, the entire test optical route consists of a laser light source, two orthogonal polarizers that act as a polarizer and an analyzer, a detector, and a rotating table on which the test liquid crystal box is placed. The rotating table is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at a 45° angle to the polarization direction of the polarizer. The liquid crystal box rotates around an axis that is perpendicular to the orientation direction and passes through the center of the liquid crystal box. When the liquid crystal box is driven by a stepper motor to rotate, the information changes of the outgoing light generated are received by the detector and transmitted back to the computer for processing and calculation. The measurement data of the vertically oriented liquid crystal device made with a long substrate with a long bombardment time just prepared and the measurement data 6 months later were summarized and processed, and the results are shown as follows. Fig.15 As shown in the figure, it can be seen that the liquid crystal devices made of the short bombardment time film and the long bombardment time film substrate treated with the long alkyl chain ammonium chloride solution still maintain the pre-tilt angle of the liquid crystal molecules above 89° after being placed for 6 months, indicating that the liquid crystal devices made of the alignment films prepared by these two methods have stable alignment effects and long retention time. Among them, 1. The ion beam bombardment tilt angle is 45°; 2. The liquid crystal device made of the short bombardment time inorganic vertical alignment film substrate has no alignment effect after 15 days of production.

[0092] Example 4

[0093] Please refer to the preparation and testing process of parallel alignment liquid crystal devices Fig.16 The preparation method is as follows (refer to Fig.18 ):

[0094] S1 (magnetron sputtering coating): The parallel oriented film is prepared by tilted coating, and the coating instrument is a single optical coating machine. First, the coating substrate is processed, and a 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 coating method of the ITO glass substrate is as follows Fig.17 As shown, the vacuum pressure during coating is 3×10 -3 Pa; working pressure 1.1×10 -1 Pa; Ar + The volume flow rate is 300sccm, the O2 volume flow rate is 200sccm; the working voltage is 335±5V; during the coating process, the target film thickness is set to 20-200nm, the coating inclination angle is changed by adjusting the tooling inclination angle on the coating loading plate of the equipment, and 13 groups of angle conditions with an angle difference of 5° from 0° to 60° are set to prepare a series of thin films with inclination angles;

[0095] S2 (treatment of inorganic parallel oriented film substrate): Place the glass substrate containing the inorganic oriented film in a polytetrafluoroethylene glass cleaning rack, and then place it in deionized water, set the cleaning temperature to 40°, the cleaning time to 20 minutes, and perform ultrasonic cleaning. After this process, the water needs to be changed, and the same cleaning process is repeated three times. After cleaning, take out the cleaned substrate, use a nitrogen gun to blow off the surface water stains, put it in a drying oven at 120°C for 2 hours, take it out after the substrate is completely dry, and put it in a UV machine for ultraviolet irradiation after the surface temperature drops to room temperature. Set the time to 15 minutes, and it can be used after irradiation.

[0096] S3 (spraying spacers): Place the substrate coated with SiO2 film on the operating table of the dry spray equipment, add spherical spacers with a diameter of 15μm into the spray hole, press and hold the spray switch for more than ten seconds, and wait for the spacers to be completely deposited. For details of the operation, see Figure 5 .

[0097] S4 (liquid crystal injection & packaging): Cover the coated surface with the substrate with spacers deposited on the surface and the cleaned substrate in an anti-parallel bombardment direction. For details, please refer to Figure 6 , and then use AB glue to seal the long sides, leaving gaps on the short sides for liquid crystal injection; after waiting for the glue to dry, an empty liquid crystal box of the inorganic orientation substrate is obtained, and positive liquid crystal is injected into it. After the liquid crystal fills the liquid crystal box under capillary action, the liquid crystal box is sealed with AB glue to complete the packaging operation of the liquid crystal box.

[0098] S5 (capturing polarized images of liquid crystal devices): using a polarized microscope to capture polarized images of liquid crystal boxes. The schematic diagram of the simple structure of the polarized microscope is as follows: Fig. 9 As shown, turn on the backlight, fix the polarization direction of polarizer 1 unchanged, place the liquid crystal box between polarizer 1 and polarizer 2, adjust the rotation angle of polarizer 2 to make it parallel or orthogonal to the polarization direction of polarizer 1, and take the polarization image of the liquid crystal box just made in the parallel state and the orthogonal state. After summarizing the images, the polarization image of the liquid crystal device made of the parallel alignment substrate is obtained. For details, see Fig.19 .

[0099] from Fig.19It can be seen that, 1. With the 25° inclination angle as the boundary, when the coating angle is less than 25°, the substrate has no obvious orientation effect, and there is no obvious change in the microscopic image obtained by changing the angle between the liquid crystal box and the polarizer; when the coating angle is greater than 25° and gradually increases, it is observed that the orientation effect of the liquid crystal box gradually becomes better. Under the coating angle of 45°, the liquid crystal box has a more obvious change in light and dark states. When the coating angle is 60°, the orientation effect of the liquid crystal box corresponding to the substrate is the best. It can be concluded that the liquid crystal is oriented by magnetron sputtering oblique coating, and the oblique coating angle is positively correlated with the orientation performance of the liquid crystal device produced therefrom. Under the condition of a larger coating inclination angle, an inorganic oriented film with parallel orientation is obtained, and the coating inclination angle should be greater than 25°. ; 2. In Figures (a~d, i~l, q~t, y), the orientation direction of the liquid crystal box is 0° to the polarization direction, and in Figures (e~h, m~p, u~x, z), the orientation direction of the liquid crystal box is 45° to the polarization direction; 3. The white arrows in the figures indicate the polarizer P and the analyzer A; 4. The bottom picture is the dark state phenomenon observed under a polarizing microscope (POM), and the picture in the upper right corner is the dark state phenomenon observed with the naked eye between orthogonal polarizers.

[0100] S6 (measurement of the pre-tilt angle of liquid crystal molecules in liquid crystal devices): the schematic diagram of the pre-tilt angle of liquid crystal molecules can be seen Fig.10 The crystal rotation method is used to measure the pre-tilt angle of the liquid crystal molecules in the liquid crystal box. The measurement optical path is as follows: Fig.11 As shown, the entire test optical path consists of a laser light source, two orthogonal polarizers that serve as a polarizer and an analyzer, a detector, and a rotating table on which the test liquid crystal box is placed. The rotating table is located between the two orthogonal polarizers. The default bombardment direction is the orientation direction and is at a 45° angle to the polarization direction of the polarizer. The liquid crystal box rotates around an axis that is perpendicular to the orientation direction and passes through the center of the liquid crystal box. When the liquid crystal box is driven by a stepper motor to rotate, the information changes of the outgoing light generated are received by the detector and transmitted back to the computer for processing and calculation. When performing the pretilt angle test, the bombardment direction of the test substrate is placed along the rotation direction of the turntable, that is, the default long axis direction of the liquid crystal molecules is arranged along the bombardment direction. For the pretilt angle test of the liquid crystal box with an orientation effect, that is, the coating tilt angle condition of the test box is greater than or equal to 30°, 3 to 5 test points are selected on each liquid crystal box for testing. The experimental results show that the long axis direction of the liquid crystal molecules is arranged along the tilt direction of the substrate coating, and the relationship between the pretilt angle and the angle change is as follows Fig. 20 shown.

[0101] according to Fig. 20 The test curve of the medium pretilt angle shows that the overall test values ​​of the pretilt angle are small after the liquid crystal box has an orientation effect, and the pretilt angle suddenly decreases after the tilt angle reaches 45°. At this time, the orientation effect of the liquid crystal box is more obvious when observed under a polarizing microscope. Although a faster response time can be obtained for smaller molecular pretilt angles, this is relatively small for the pretilt angle requirement of a general parallel orientation box (about 3°~5°).

[0102] Effect Example 1

[0103] Study on the mechanism of orientation formation

[0104] Regarding vertical orientation, the present invention performs AFM (Atomic Force Microscopy) scanning on inorganic thin films without bombardment and inorganic vertically oriented thin films with long bombardment time and large bombardment angle, and finds that there is no obvious change in the film morphology on the substrate surface before and after ion beam treatment, and only granular structures can be observed in both cases. For details, see Fig.21 The present invention then introduces XPS (X-ray Photoelectron Spectroscopy) to analyze the element structure of the surface of the alignment layer. Fig. 22 , Fig.23 Experimental data show that the peak intensity of the Si element in the full spectrum decreases, and the proportion of Si-O bonds in the fine spectrum decreases, which is consistent with the experimental results reported in the literature. It can be considered that the ion beam causes changes in the bonding structure of the SiO2 film surface, affecting the van der Waals force between the film surface and the liquid crystal molecules, thereby inducing the liquid crystal to produce directional arrangement and form a vertical orientation.

[0105] Regarding parallel orientation, the present invention performs AFM (Atomic Force Microscopy) scanning on the surface morphology of the substrate under different coating angles obtained by tilted coating. Fig.24 From the scanning results, it can be seen that there are many non-directional undulating granular structures on the surface of the orientation film of the 0° coated substrate due to the lack of anisotropy source; with the increase of the inclination angle, and when the coating inclination angle reaches 45°, a friction-like striped undulating structure with a specific direction appears on the substrate surface. It can be considered that the orientation mechanism of parallel orientation is that the oblique deposition of inorganic materials causes a "groove-like" undulating morphology on the substrate surface. In order to maintain the lowest energy stable state, the liquid crystal molecules are arranged along the direction parallel to the groove direction to avoid the generation of additional elastic strain energy, thereby producing an orientation effect.

[0106] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

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 orientation layer includes one or more of a vertical orientation and a parallel orientation; When the alignment of the liquid crystal alignment layer includes a vertical alignment, the preparation method includes: S1, coating the substrate by sputtering to form a coating layer; S2, bombarding the coating layer to obtain the liquid crystal alignment layer; When the orientation of the liquid crystal alignment layer includes a parallel orientation, the preparation method includes: A. coating a 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 according to claim 1, characterized in that: When the orientation of the liquid crystal orientation layer includes a vertical orientation, in step S2, the bombardment includes one or more of a short-duration bombardment and a long-duration bombardment; the bombardment time of the short-duration bombardment is not longer than 300s; the bombardment time of the long-duration bombardment is 300s-1800s; the bombardment angle includes a multi-angle bombardment from 0° to 60°.

3. The method for preparing a liquid crystal alignment layer based on an inorganic thin film according to claim 2, characterized in that: The bombardment angle includes multi-angle bombardment with an interval of 15° at each time from 0° to 60°; when the bombardment is the short-duration bombardment, step S2 further includes: after the short-duration bombardment is completed, treating the liquid crystal alignment layer with a long alkyl chain ammonium chloride solution.

4. The method for preparing a liquid crystal alignment layer based on an inorganic thin film according to claim 3, characterized in that: The long alkyl chain ammonium chloride solution treatment operation 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 to 0.5% for 20 to 60 minutes, then rinsing with deionized water, drying at room temperature, and heating at 130° C. for 20 to 60 minutes after drying.

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

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

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

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

10. An application of the liquid crystal alignment layer as claimed in claim 9, characterized in that: Used to prepare liquid crystal display devices.

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