Liquid crystal alignment film, method for producing the same, and display device

Abstract

The application discloses a liquid crystal alignment film, a preparation method thereof and a display device. The liquid crystal alignment film is prepared from a raw material containing methacrylic acid and methyl methacrylate. The surface of the liquid crystal alignment film has a large polarity, the large polarity of the surface can make liquid crystal molecules vertically stand, and then vertical alignment is completed. The carboxyl contained in the liquid crystal alignment film can form a stronger van der Waals force with a substrate, and can form a chemical bond with groups in the substrate and a liquid crystal thin film, and further enhance the binding force between the liquid crystal alignment film and the substrate and between the liquid crystal alignment film and the liquid crystal thin film.

Description

Technical Field

[0001] This application relates to the field of liquid crystal display technology, and in particular to a liquid crystal alignment film, its preparation method and display device. Background Technology

[0002] In recent years, with the development of display technology, liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) have been widely used in various electronic devices. To improve the optical performance of displays, optical films such as optical compensation films or retardation films are typically used. As optical films, anisotropic optical films composed of liquid crystal compounds have seen rapid development in recent years.

[0003] On the other hand, in recent years, the required functions of optical films have become increasingly demanding, especially in the manufacturing and lamination processes. Currently, side-chain liquid crystal polymers or side-chain compounds are commonly used in vertically aligned optical films. However, these compounds are expensive and have weak adhesion to the substrate and liquid crystal film, failing to meet the adhesion requirements of panel manufacturers. Summary of the Invention

[0004] The purpose of the embodiments in this specification is to provide a liquid crystal alignment film, its preparation method and display device, in order to solve the problems of high cost of side-chain liquid crystal polymers or side-chain compounds in current vertical alignment optical films, poor adhesion between them and the substrate and liquid crystal film, which cannot meet the adhesion requirements of panel manufacturers.

[0005] To achieve the above objectives, the embodiments in this specification adopt the following technical solutions:

[0006] In a first aspect, a liquid crystal alignment film is provided, the liquid crystal alignment film being prepared from raw materials comprising methacrylic acid and methyl methacrylate.

[0007] Optionally, the methacrylic acid accounts for 30% to 95% of the total mass of methacrylic acid and methyl methacrylate.

[0008] Optionally, the molecular weight of the methacrylic acid is 30,000 to 300,000.

[0009] Optionally, the molecular weight of the methyl methacrylate is 30,000 to 300,000.

[0010] Optionally, the surface energy of the liquid crystal alignment film is 40mN / m-75mN / m.

[0011] Optionally, the surface energy of the liquid crystal alignment film is 48mN / m-70mN / m.

[0012] Optionally, the water droplet angle of the liquid crystal alignment film is 0°-45°.

[0013] Optionally, the ratio of the polar component to the dispersive component of the surface energy of the liquid crystal alignment film is 0.5-1.8.

[0014] Optionally, the ratio of the polar component to the dispersive component of the surface energy of the liquid crystal alignment film is 0.8-1.4.

[0015] Optionally, the raw materials for preparing the liquid crystal alignment film further include a crosslinking agent and a solvent, wherein the crosslinking agent accounts for 5-20% of the total mass of the raw materials for preparing the liquid crystal alignment film, and the solvent accounts for 80-95% of the total mass of the raw materials for preparing the liquid crystal alignment film.

[0016] Optionally, the crosslinking agent is a water-soluble crosslinking agent.

[0017] Optionally, the crosslinking agent is an auxiliary agent that reacts with carboxyl groups, or a functional group that reacts with carboxyl groups; the crosslinking agent is a water-soluble crosslinking agent.

[0018] Optionally, the crosslinking agent is one or a combination of amino resins, isocyanate curing agents, metal ion crosslinking agents, carboimide crosslinking agents, aziridine crosslinking agents, and epoxy silane crosslinking agents.

[0019] According to another embodiment of this application, a method for preparing a liquid crystal alignment film is provided, comprising the following steps:

[0020] (1) Polymerize methacrylic acid and methyl methacrylate to form a polymer solution, and dilute the polymer solution in a solvent;

[0021] (2) Add crosslinking agent to solvent and stir evenly to obtain the prepared mixed solution;

[0022] (3) Apply the prepared mixed solution to the surface of the substrate;

[0023] (4) Dry the coated substrate to obtain a liquid crystal alignment film.

[0024] Thirdly, a display device is provided, the display device comprising the liquid crystal alignment film provided in the first aspect of this application or the liquid crystal alignment film prepared in the second aspect of this application.

[0025] The at least one technical solution adopted in the embodiments of this application can achieve the following beneficial effects: This specification provides a liquid crystal alignment film, its preparation method, and a display device. The surface of the liquid crystal alignment film has a large polarity, which allows the liquid crystal molecules to stand vertically, thereby completing vertical alignment. The carboxyl groups contained in the liquid crystal alignment film can form stronger van der Waals forces with the substrate, and can also form chemical bonds with groups in the substrate and the liquid crystal film, further enhancing the bonding force between the liquid crystal alignment film and the substrate, and between the liquid crystal alignment film and the liquid crystal film. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0027] Figure 1 A schematic diagram of the structure of the optical compensation film provided in Embodiment 43 of this specification;

[0028] Figure 2 This is a schematic diagram of the structure of the LCD optical compensation film provided in Embodiment 44 of this specification;

[0029] Figure 3 This is a schematic diagram of the structure of the OLED optical compensation film provided in Example 45 of this specification.

[0030] Explanation of reference numerals in the attached figures: 1-Anisotropic layer, 2-Liquid crystal alignment film, 3-Substrate, 401-First polarizer layer, 501-First adhesive layer, 102-Second phase retardation film layer, 502-Adhesive layer, 101-First phase retardation film layer, 301-First substrate layer, 503-Third adhesive layer, 6-OLED layer, 402-Second polarizer layer, 504-Fourth adhesive layer, 302-Second substrate layer, 103-Third phase retardation film layer, 505-Fifth adhesive layer, 7-IPS layer, 506-Sixth adhesive layer, 403-Third polarizer layer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] According to one embodiment of this application, a liquid crystal alignment film is provided, the liquid crystal alignment film being prepared from raw materials comprising: methacrylic acid and methyl methacrylate.

[0033] The methacrylic acid comprises 30% to 95% of the total mass of methacrylic acid and methyl methacrylate, with the remainder being the mass fraction of methyl methacrylate. Specifically, the sum of the mass fractions of methacrylic acid and methyl methacrylate in the total mass of methacrylic acid and methyl methacrylate is 100%. Preferably, the methacrylic acid comprises 50% to 95% of the total mass of methacrylic acid and methyl methacrylate.

[0034] The molecular weight of the methacrylic acid is 30,000 to 300,000; and / or, the molecular weight of the methyl methacrylate is 30,000 to 300,000. The molecular weight of the methacrylic acid is 30,000 to 300,000, while the molecular weight of the methyl methacrylate is not limited. Alternatively, both the molecular weight of the methacrylic acid and the molecular weight of the methyl methacrylate can be limited to 30,000 to 300,000.

[0035] The liquid crystal alignment film can be used for vertical alignment of liquid crystals. Its surface energy, water droplet angle, polar component, and dispersion component are determined by measuring the water droplet angle. Specifically, the surface energy of the liquid crystal alignment film is 40 mN / m-75 mN / m. Limiting the surface energy within this range helps the liquid crystal alignment film solution to form a better film on the liquid crystal alignment film. The surface energy of the liquid crystal alignment film can be 40 N / m, 45 N / m, 50 N / m, 60 N / m, 70 N / m, 75 N / m, or any value between them. Preferably, the surface energy of the liquid crystal alignment film is 48 mN / m-70 mN / m. The water droplet angle of the liquid crystal alignment film is 0°-45°. Limiting the water droplet angle within this range facilitates better coating of the liquid crystal alignment film on the substrate. The water droplet angle of the liquid crystal alignment film can be 0°, 1°, 5°, 10°, 20°, 35°, 40°, 45°, or any value between them. The ratio of the polar component to the dispersion component of the surface energy of the liquid crystal alignment film is 0.5-1.8. Limiting this ratio within this range allows for good alignment of the C film. The ratio of the polar component to the dispersion component of the surface energy of the liquid crystal alignment film can be 0.5, 0.6, 0.9, 1.0, 1.2, 1.4, or any value between them. Preferably, the ratio of the polar component to the dispersion component of the surface energy of the liquid crystal alignment film is 0.8-1.4.

[0036] The raw materials for preparing the liquid crystal alignment film also include a crosslinking agent and a solvent, wherein the crosslinking agent accounts for 5-20% of the total mass of the raw materials for preparing the liquid crystal alignment film, and the solvent accounts for 80-95% of the total mass of the raw materials for preparing the liquid crystal alignment film. The raw materials for preparing the liquid crystal alignment film may also include a leveling agent, which can improve the effect; the function can be achieved without the liquid crystal alignment film.

[0037] The crosslinking agent is an auxiliary agent that can react with carboxyl groups, or a functional group that can react with carboxyl groups under catalytic conditions. The crosslinking agent is water-soluble and does not react rapidly with water. The crosslinking agent allows the already polymerized film-forming material molecules methacrylic acid and methyl methacrylate to further polymerize.

[0038] The crosslinking agent may specifically include any one or more of the following crosslinking agents:

[0039] (1) Amino resin

[0040] The role of amino resins in liquid crystal alignment film raw materials is to crosslink the film-forming material molecules methacrylic acid and methyl methacrylate through a chemical reaction into a larger molecular weight compound structure. This network structure is obtained through the reaction of amino resin molecules with the functional groups on the film-forming material molecules, and simultaneously through a condensation reaction with other amino resin molecules. Amino resins readily react with polymers containing primary and secondary hydroxyl groups, carboxyl groups, and amide groups. This invention utilizes the rapid crosslinking ability of amino resins with carboxyl groups to crosslink resin molecules containing methacrylic acid and methyl methacrylate, forming macromolecules and improving the solvent resistance and high-temperature resistance of the alignment layer. Specifically, the amino resin can be one or a combination of melamine-formaldehyde, benzo-melamine-formaldehyde, or urea-formaldehyde (urea-formaldehyde) resin.

[0041] (2) Isocyanate curing agents

[0042] Isocyanate curing agents contain highly reactive isocyanate groups. Isocyanate can react with active hydrogen-containing groups such as carboxyl, hydroxyl, amino, urea, and urethane to achieve cross-linking and form a network structure polymer. However, because isocyanate reacts rapidly with water, it is generally not used in aqueous phase reactions. To address this issue, end-capped isocyanates have been developed. These isocyanates undergo hydrophilic modification and are simultaneously blocked by steric hindrance. As the aqueous solvent evaporates, the molecular structure deforms, releasing the isocyanate, which then cross-links with the active hydrogen in the resin. The isocyanate group, after end-capping treatment, has significantly reduced activity in water and can even exist in a single-component form. Preferably, the isocyanate curing agent is an end-capped isocyanate curing agent.

[0043] (3) Metal ion crosslinking agents

[0044] Metal ion crosslinking agents are room-temperature crosslinking agents. They achieve crosslinking by reacting metal ions with carboxyl groups on the molecular chain. Metal ion crosslinking agents usually exist in the form of ammonium complex ions. During film formation, as ammonia volatilizes, metal ions are released from the complex and react with carboxyl groups on the resin to form insoluble salts or complexes, thereby achieving coating crosslinking.

[0045] (4) Carboimide crosslinking agents

[0046] Carboimides contain cumulative double bonds, enabling them to react with hydroxyl and carboxyl groups (mainly carboxyl groups) in resins. Compared to monomeric carboimides, polycarboimide polymers offer advantages such as high efficiency and low toxicity. At room temperature, monomeric carboimides react faster than polycarboimide polymers. The choice between monomeric and polycarboimide polymers can be made based on specific needs.

[0047] (5) Aziridine crosslinking agents

[0048] Aziridine crosslinking agents contain two or more aziridine rings. Compounds with carboxyl groups can react with aziridine rings at room temperature to achieve crosslinking and curing.

[0049] (6) Epoxy silane crosslinking agents

[0050] Epoxy silanes are generally used as coupling agents in small quantities, but they exhibit outstanding performance as carboxyl crosslinking agents. Coatings crosslinked with epoxy silane crosslinking agents possess excellent gloss retention, weather resistance, solvent resistance, abrasion resistance, and high hardness. The reaction mechanism involves the silanol bonds generated by the hydrolysis of silane groups, which can crosslink and solidify to form a macromolecular structure. Simultaneously, the epoxy bonds in the epoxy silane react with the carboxyl groups to form chemical bonds.

[0051] According to another embodiment of this application, a method for preparing a liquid crystal alignment film is provided, comprising the following steps:

[0052] (1) Polymerize methacrylic acid and methyl methacrylate to form a polymer solution, and dilute the polymer solution in a solvent to the required solid content;

[0053] Methacrylic acid and methyl methacrylate are added to a reaction vessel in a specific ratio. A free radical initiator, comprising 1% to 3% of the total mass of the methacrylic acid and methyl methacrylate, is then added. The reaction temperature is controlled within the range of 60°C to 85°C. Nitrogen gas is introduced to replace the air, and the mixture is stirred for 15 hours to obtain a polymer solution. The raw materials for preparing the liquid crystal alignment film may also include a free radical initiator, which can polymerize methacrylic acid and methyl methacrylate to form a polymer solution.

[0054] From the perspective of solution solubility and stability, the solvent is preferably a solvent that can evaporate and dry below 100°C, and can be a mixture of water and alcohol or an alcohol. More preferably, the solvent can be one or more of methanol, ethanol, isopropanol, and water. The amount of solvent added is not particularly limited as long as it does not significantly damage the coating state. In step (1), the polymer is dissolved in the solvent, and the mass percentage content of the solvent is 80% to 95%, more preferably 85% to 95%, and particularly preferably 90%.

[0055] When dissolving polymers in a solvent, heating and stirring are preferred to ensure uniform dissolution. The heating and stirring temperature can be adjusted according to the polymer's solubility in the solvent. From a production efficiency perspective, 15°C to 110°C is preferred, 25°C to 105°C is more preferred, 35°C to 100°C is even more preferred, and 40°C to 70°C is particularly preferred.

[0056] (2) Add crosslinking agent to solvent and stir evenly to obtain the prepared mixed solution;

[0057] A leveling agent can be added to the solvent along with a crosslinking agent.

[0058] (3) The prepared mixed solution is coated onto the surface of the substrate using a coating machine;

[0059] The substrate can be used to hold the prepared solution. The substrate is made of a heat-resistant material, so that the performance of the substrate will not be affected when the prepared solution coated on its surface is heated and dried.

[0060] The substrate can be an organic material such as a glass substrate, metal substrate, ceramic substrate, or plastic substrate. When the substrate is an organic material, it can be a cellulose derivative, polyolefin, polyester, polycarbonate, polyacrylate, acrylic resin, polyarylate, polyethersulfone, polyimide, polyphenylene sulfide, polyphenylene ether, nylon, or polystyrene. Preferably, polyester, polystyrene, polyacrylate, polyolefin, cellulose derivative, polyarylate, or polycarbonate are plastic substrates; more preferably, metal, polyethylene terephthalate (PET), or cellulose derivative substrates are preferred. The substrate shape can be curved, in addition to being flat. Depending on the actual needs, the substrate can also have functional layers such as an electrode layer, anti-reflective layer, or reflective layer.

[0061] The prepared solution can be applied to the substrate surface using various coating methods, such as applicator coating, rod coating, spin coating, roller coating, direct gravure coating, reverse gravure coating, flexo coating, inkjet coating, die coating, cap coating, dip coating, and slot coating.

[0062] (4) Place the coated substrate in a forced-air drying oven at 70℃~120℃ and dry for 60s~80s to obtain a liquid crystal alignment film that can be vertically aligned.

[0063] Based on the liquid crystal alignment film preparation method provided in the above embodiments of this application, this application also provides another method for preparing a phase retardation film, which may include the following steps:

[0064] Step 1: Apply the prepared mixed solution provided in the above embodiment to the substrate to obtain a non-peelable coating;

[0065] Step 2: Coat the non-peelable coating with a polymerizable phase retardation film composition solution and dry it to obtain a polymerizable phase retardation film composition resin layer.

[0066] Step 3: Irradiate the polymerizable phase retardation film composition resin layer to obtain a phase retardation film.

[0067] According to another embodiment of this application, a display device is provided, the display device comprising a liquid crystal alignment film provided in one embodiment of this application or a liquid crystal alignment film prepared in another embodiment of this application. Specifically, it may be a liquid crystal alignment film obtained by peeling off a substrate.

[0068] The display device can be a display element or a display. The display device can be an active display device or a passive matrix display device. Further, the display device can be a liquid crystal display device or an OLED display device.

[0069] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0070] In the following embodiments, unless otherwise specified, all raw materials used are available from publicly available commercial sources. Percentages refer to mass percentages, temperatures are in degrees Celsius (°C), and the specific meanings of other symbols and test conditions are as follows:

[0071] Rth represents the optical retardation in the vertical direction of the thin film, that is, the retardation perpendicular to the surface of the retardation film. The testing device is AxoScan. Specifically, by inputting the average refractive index ((nx+ny+nz) / 3) and the film thickness (d(μm)) into AxoScan, Rth(λ) = (nz-(nx+ny) / 2)×d.

[0072] Adhesion performance was tested using the cross-cut adhesion test with SM600 tape. Pre-tilt angle and twist angle tests were conducted using an AxoScan instrument. Bending resistance was tested using a flexural strength tester.

[0073] The raw materials used in the examples include: (1) Liquid crystal alignment film raw materials: methacrylic acid, methyl methacrylate, azobisisobutyronitrile (AIBN); (2) Solvents: ethanol, toluene, cyclohexanone; (3) Vertically aligned polymerizable liquid crystal: polymerizable liquid crystal composition (Merck 2296); (4) Substrate: polyethylene terephthalate (PET), cellulose triacetate film (TAC), cyclic olefin polymer film (COP).

[0074] Examples 1-12:

[0075] The polymer raw materials for preparing liquid crystal alignment films are prepared according to the composition and content in Table 1 below and the methods described below.

[0076] The preparation method of the polymer raw material for the liquid crystal alignment film is as follows:

[0077] Prepare a mixture of monomers according to the proportions in the table and add it to a three-necked flask. Purge the air with nitrogen and then begin heating. Maintain the temperature at 95°C and react for 20 hours. After the reaction is complete, cool to room temperature and then add dropwise to another container with cyclohexane as a stirring solvent, stirring for 20 minutes. Filter and wash three times with cyclohexane, then place in an oven and dry under vacuum at 40°C.

[0078] Table 1. Composition and content of polymer raw materials for liquid crystal alignment films ( / g)

[0079]

[0080]

[0081] Table 2 Polymer Molecular Weight Distribution

[0082] Example 1 240000 120000 220000 1.8 Example 2 200000 90000 185000 2.1 Example 3 177000 65000 157000 2.4 Example 4 230000 110000 210000 1.8 Example 5 210000 85000 19000 2.0 Example 6 180000 60000 167000 2.3 Example 7 220000 109000 200000 2.0 Example 8 190000 70000 16000 2.2 Example 9 160000 55000 147000 2.3 Example 10 250000 130000 230000 1.7 Example 11 210000 85000 195000 2.2 Example 12 180000 70000 150000 2.6

[0083] Examples 13-24:

[0084] The preparation method is as follows:

[0085] (1) Dissolve the polymers obtained in Examples 1-12 in ethanol and heat;

[0086] (2) After the polymer in step one is completely dissolved, cool it to room temperature, add 5% SC-A03 (commercially available) amino resin, stir evenly, and obtain the prepared solution.

[0087] (3) Apply the prepared solution to the surface of the substrate;

[0088] (4) Dry the coated substrate to obtain a liquid crystal alignment film.

[0089] Table 3 Material Proportioning Table for Each Embodiment

[0090]

[0091]

[0092] The surface properties of the liquid crystal alignment films obtained in Examples 12-24 are shown in Table 4 after testing.

[0093] Table 4. Surface performance data of the liquid crystal alignment films obtained in Examples 12-24

[0094]

[0095] Method for preparing vertically oriented polymerizable liquid crystal thin films:

[0096] Step 1: Take 10g of commercially available polymerizable liquid crystal composition 2296 (provided by Merck) and add 54g of toluene and 36g of cyclohexanone to it.

[0097] Step 2: Place the above mixed solution in a magnetically stirred water bath at a temperature of 45°C, turn on the stirrer, set the speed to 100 rpm, and stir for 1 hour.

[0098] Step 3: Using a malt bar (15#, representing the bar number, used to control the thickness), scrape the above-mixed solution onto the liquid crystal alignment film prepared in Examples 13-24.

[0099] Step 4: Place the film prepared in step 3 into an oven with a controlled temperature of 70°C and keep it there for 60 seconds.

[0100] Step 5: Place the aligned liquid crystal film from Step 4 under a UV (365nm main wavelength) lamp, introduce nitrogen gas, and when the nitrogen concentration exceeds 99.95%, irradiate with UV with a UV energy of 500mJ.

[0101] The pretilt angle and Rth value of the vertically aligned liquid crystal film were tested using the AxoScan device. The test results are shown in Table 5.

[0102] Table 5 Optical data of vertically aligned films obtained from alignment films in each embodiment.

[0103] Example 13 103.2 90.2 Example 14 118.7 90.1 Example 15 89.6 89.7 Example 16 92.7 90.1 Example 17 113.7 90.2 Example 18 76.2 89.5 Example 19 102.1 90.0 Example 20 121.7 90.1 Example 21 94.2 90.2 Example 22 89.4 90.2 Example 23 102.8 89.9 Example 24 99.1 90.0

[0104] As can be seen from Table 5, when a polymer with a mass fraction of less than 50% methyl methacrylate is used as a liquid crystal alignment film, the polymerizable liquid crystal composition can form a vertical orientation on it, and the optical and Rth properties are normal.

[0105] Peel strength tests were performed on polymer films formed on different substrates using the cross-cut adhesion test, and the results are shown in Table 6.

[0106] Table 6 Optical data of vertical alignment films obtained from liquid crystal alignment films in Examples 12-24.

[0107] Example 13 No drops No drops ＜3％ Example 14 No drops No drops ＜3％ Example 15 No drops No drops ＜3％ Example 16 No drops No drops ＜3％ Example 17 No drops No drops ＜3％ Example 18 No drops No drops ＜3％ Example 19 No drops No drops ＜3％ Example 20 No drops No drops ＜3％ Example 21 No drops No drops ＜3％ Example 22 No drops ＜3％ ＜3％ Example 23 No drops ＜3％ ＜3％ Example 24 No drops ＜3％ ＜3％

[0108] As can be seen from Table 6, using methyl methacrylate and methacrylic polymer as liquid crystal alignment films, the adhesion to PET and COP substrates is the best, with no peeling in the cross-cut adhesion test. The adhesion to TAC substrates decreases when the methacrylic acid content decreases.

[0109] Examples 25-33

[0110] The polymer raw materials for preparing liquid crystal alignment films are prepared according to the composition and content in Table 7 below and the methods described below.

[0111] The preparation method of the polymer raw material for the liquid crystal alignment film is as follows: The monomers in the table are mixed according to the specified proportions and added to a three-necked flask. After purging the air with nitrogen, the temperature is raised. The temperature is controlled at 95℃, and the reaction is carried out for 20 hours. After the reaction is complete, the mixture is cooled to room temperature and then added dropwise to another container with cyclohexane being stirred for 20 minutes. The mixture is filtered, washed three times with cyclohexane, and then placed in an oven for vacuum drying at 40℃.

[0112] Table 7. Polymer composition and content ( / g) of liquid crystal alignment film

[0113] Example 25 0 10 40 0.05 Example 26 0 10 40 0.10 Example 27 0 1 40 0.30 Example 28 1 9 40 0.05 Example 29 1 9 40 0.10 Example 30 1 9 40 0.30 Example 31 3 7 40 0.05 Example 32 3 7 40 0.10 Example 33 3 7 40 0.30

[0114] Table 8 Polymer Molecular Weight Distribution

[0115] Example 25 230000 110000 200000 1.8 Example 26 210000 92000 180000 2.1 Example 27 180000 70000 160000 2.4 Example 28 210000 100000 200000 1.8 Example 29 190000 80000 170000 2.0 Example 30 180000 66000 165000 2.3 Example 31 220000 110000 200000 2.0 Example 32 170000 70000 160000 2.2 Example 33 150000 55000 130000 2.8

[0116] Examples 34-42 and Comparative Examples 1-4:

[0117] The preparation method is as follows:

[0118] (1) Dissolve the polymers obtained in Examples 25-33, Comparative Examples 1-2, and Comparative Examples 3-4 in ethanol and heat them;

[0119] (2) After the polymer in step one is completely dissolved, cool it to room temperature, add 5% SC-A03 (commercially available) amino resin, stir evenly, and obtain the prepared solution.

[0120] (3) Apply the prepared solution to the surface of the substrate;

[0121] (4) Dry the coated substrate to obtain a liquid crystal alignment film.

[0122] Table 9 Material Proportioning Table for Examples 34-24 and Comparative Examples 1-4

[0123] Example 34 Example 25 5 0.25 120 Example 35 Example 26 5 0.25 120 Example 36 Example 27 5 0.25 120 Example 37 Example 28 5 0.25 120 Example 38 Example 29 5 0.25 120 Example 39 Example 30 5 0.25 120 Example 40 Example 31 5 0.25 120 Example 41 Example 32 5 0.25 120 Example 42 Example 33 5 0.25 120 PVA resin PVA resin mass (g) SC-A03(g) Water (g) Comparative Example 1 PVA203 5 0.25 120 Comparative Example 2 PVA203 5 120 Silane coupling agents Mass of silane coupling agent (g) SC-A03(g) Water (g) Comparative Example 3 Triethoxysiloxane 5 0.25 120 Comparative Example 4 Triethoxysiloxane 5 120

[0124] The surface properties of the liquid crystal alignment films obtained in Examples 34-24 and Comparative Examples 1-4 were tested and are shown in Table 10.

[0125] Table 10 Surface performance data of liquid crystal alignment films obtained in Examples 34-24 and Comparative Examples 1-4

[0126]

[0127]

[0128] Method for preparing vertically oriented polymerizable liquid crystal thin films:

[0129] Step 1: Take 10g of polymerizable liquid crystal composition 2296 (provided by Merck) and add 54g of toluene and 36g of cyclohexanone to it.

[0130] Step 2: Place the above mixed solution in a magnetically stirred water bath at a temperature of 45°C, turn on the stirrer, set the speed to 100 rpm, and stir for 1 hour.

[0131] Step 3: Using a malt stick (15#), scrape the above-mixed solution onto the liquid crystal alignment films prepared in Examples 34-24 and Comparative Examples 1-4.

[0132] Step 4: Place the film prepared in step 3 into an oven with a controlled temperature of 70°C and keep it there for 60 seconds.

[0133] Step 5: Place the aligned liquid crystal film from Step 4 under a UV (365nm main wavelength) lamp, introduce nitrogen gas, and when the nitrogen concentration exceeds 99.95%, irradiate with UV with a UV energy of 500mJ.

[0134] The pretilt angle and Rth value of the vertically aligned liquid crystal film were tested using the AxoScan equipment. The test results are shown in Table 11.

[0135] Table 11 Optical data of vertically aligned films obtained from alignment films of Examples 34-24 and Comparative Examples 1-4

[0136]

[0137]

[0138] As can be seen from Table 11, when a polymer with a mass fraction of methyl methacrylate greater than 70% is used as the alignment film, the vertically aligned liquid crystal film has no alignment ability and becomes foggy.

[0139] The peel strength of polymer films formed on different substrates was tested using the cross-cut adhesion test, and the test results are shown in Table 12.

[0140] Table 12 Optical data of vertically aligned films obtained from alignment films of Examples 34-24 and Comparative Examples 1-4

[0141]

[0142]

[0143] As shown in Table 12, methyl methacrylate and methacrylic acid polymers, used as alignment films, exhibit the best adhesion to PET substrates (no peeling in the cross-cut adhesion test), slightly weaker adhesion to TAC substrates (occurring occasional peeling), and poor adhesion to COP substrates (peach peeling greater than 3% but less than 10%). PVA, as an alignment film, shows poor adhesion to substrates (100% peeling in the cross-cut adhesion test). Silane coupling agents, used as alignment films, show poor adhesion to vertically aligned liquid crystal films (100% peeling in the cross-cut adhesion test).

[0144] Example 43:

[0145] A display device is provided, comprising a liquid crystal alignment film or a prepared liquid crystal alignment film. The display device is an optical compensation film; please refer to [reference needed]. Figure 1 The optical film includes an anisotropic layer 1, a liquid crystal alignment film 2, and a substrate 3, which are sequentially disposed together. The anisotropic layer 1 can be a vertically oriented liquid crystal polymer, and the substrate 3 can be COP or TAC. The anisotropic layer 1 can be used together with the substrate 3, or it can be used by stacking other anisotropic layers to improve display performance.

[0146] Example 44:

[0147] A display device is provided, comprising a liquid crystal alignment film or a fabricated liquid crystal alignment film. The display device is a structure of an LCD optical compensation film used as a compensation film in an OLED display; please refer to [link / details]. Figure 2The display device sequentially comprises a first polarizer layer 401, a first adhesive layer 501, a second phase retardation film layer 102, an alignment film layer 2, a first substrate layer 301, a third adhesive layer 503, and an OLED layer 6. The first polarizer layer 401 may be polyvinyl alcohol (PVA). The first adhesive layer 501, second adhesive layer 502, and third adhesive layer 503 may be PSA adhesive or UV adhesive, etc. The phase retardation film layer 102 may be a horizontally aligned liquid crystal type or a stretched phase retardation film, acting as a quarter-wave plate. The phase retardation film layer 101 may be a vertically aligned liquid crystal phase retardation film. The first substrate layer 301 may be made of TAC material. The OLED layer 6 may use an organic light-emitting device for display. A circular polarizer is formed by combining the polarizer, phase retardation film, adhesive layer, etc., and is used as an anti-reflection compensation film for OLED displays.

[0148] Example 45:

[0149] A display device is provided, comprising a liquid crystal alignment film or a fabricated liquid crystal alignment film. The display device is a structure used as a compensation film for OLED optical compensation films in IPS LCD displays; please refer to [link to details]. Figure 3 The display device sequentially comprises a second polarizer layer 402, a fourth adhesive layer 504, a second substrate layer 302, a liquid crystal alignment film 2, a third phase retardation film layer 103, a fifth adhesive layer 505, an IPS layer 7, a sixth adhesive layer 506, and the third polarizer layer 403. The second polarizer layer 402 and the third polarizer layer 403 can be polyvinyl alcohol (PVA) type. The fourth adhesive layer 504, the fifth adhesive layer 505, and the sixth adhesive layer 506 can be PSA adhesive or UV adhesive, etc. The second substrate layer 302 can be a uniaxially stretched or biaxially stretched COP material with in-plane phase retardation value, and can be used as a phase retardation film. The third phase retardation film layer 103 can be a vertically aligned liquid crystal type phase retardation film. The IPS layer 7 can be a commonly used IPS LCD cell. The IPS compensation film, composed of polarizers, phase retardation films, adhesive layers, etc., is used for side viewing angle light leakage and color shift compensation in IPS LCDs.

[0150] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0151] The above descriptions are merely embodiments of this application and are not intended to limit this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention; at the same time, for those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application. In summary, the content of this specification should not be construed as a limitation of the present invention, and any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid crystal alignment film, characterized in that, The liquid crystal alignment film is prepared from the following raw materials: methacrylic acid, methyl methacrylate, crosslinking agent, free radical initiator and solvent; The methacrylic acid accounts for 30% to 95% of the total mass of methacrylic acid and methyl methacrylate. The molecular weight of the methacrylic acid is 30,000 to 300,000; the molecular weight of the methyl methacrylate is 30,000 to 300,000. The surface energy of the liquid crystal alignment film is 40mN / m-75mN / m; The water droplet angle of the liquid crystal alignment film is 0°-45°; The ratio of the polar component to the dispersive component of the surface energy of the liquid crystal alignment film is 0.5-1.

8. The free radical initiator accounts for 1% to 3% of the total mass of methacrylic acid and methyl methacrylate.

2. The liquid crystal alignment film according to claim 1, characterized in that, The surface energy of the liquid crystal alignment film is 48 mN / m-70 mN / m, and the ratio of the polar component to the dispersive component of the surface energy of the liquid crystal alignment film is 0.8-1.

4.

3. The liquid crystal alignment film according to claim 1, characterized in that, The crosslinking agent accounts for 5-20% of the total mass of the raw materials for preparing the liquid crystal alignment film, and the solvent accounts for 80-95% of the total mass of the raw materials for preparing the liquid crystal alignment film.

4. The liquid crystal alignment film according to claim 1, characterized in that, The crosslinking agent is a water-soluble crosslinking agent; or The crosslinking agent is a water-soluble crosslinking agent, and the crosslinking agent is an auxiliary agent that reacts with carboxyl groups, or a functional group that reacts with carboxyl groups.

5. The liquid crystal alignment film according to claim 4, characterized in that, The crosslinking agent is one or a combination of amino resins, isocyanate curing agents, metal ion crosslinking agents, carboimide crosslinking agents, aziridine crosslinking agents, and epoxy silane crosslinking agents.

6. The liquid crystal alignment film according to any one of claims 1-5, characterized in that, The method for preparing the liquid crystal alignment film includes the following steps: (1) Polymerize methacrylic acid and methyl methacrylate to form a polymer solution, and dilute the polymer solution and free radical initiator in a solvent; (2) Add a crosslinking agent to the solvent and stir until homogeneous to obtain a prepared mixed solution; (3) Apply the prepared mixed solution to the surface of the substrate; (4) Dry the coated substrate to obtain a liquid crystal alignment film.

7. A display device, characterized in that, The display device includes the liquid crystal alignment film provided in any one of claims 1-5 or the liquid crystal alignment film prepared in claim 6.

Images