Liquid trans-dyeing liquid crystal membrane, preparation method and display device

Abstract

The invention relates to the technical field of liquid crystal materials, in particular to a liquid trans-dyeing liquid crystal membrane, a preparation method and a display device. 1%-10% of an organic dye; 5%-20% of a gel polymer; 0.1%-5% of an additive; wherein the liquid crystal film further comprises two layers of polyimide (PI) vertical orientation conducting films, and the conducting films are formed by coating a PI vertical orientation agent on a PET substrate after magnetron sputtering of an ITO layer; the liquid crystal film is high in contrast ratio and color expressive force, light with specific wavelength can be effectively absorbed by adding specific organic dye, the contrast ratio and the color expressive force of the liquid crystal film are remarkably improved, displayed images are clearer and brighter, and the liquid crystal film is high in response speed; molecular arrangement of the liquid crystal film changes rapidly under the action of an electric field, the response speed is increased by 30%-50% compared with that of a traditional liquid crystal film, and the requirement for high-speed dynamic image display can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal materials, and in particular to a liquid reverse-dyed liquid crystal film, a preparation method and a display device. Background Art

[0002] Liquid crystal materials have been widely used in display, dimming and other fields due to their unique optical and electrical properties. Traditional liquid crystal films have certain limitations in certain performance aspects, such as low contrast, slow response speed, and limited viewing angle, making it difficult to meet the needs of some high-end application scenarios. In the display field, as demand for high-quality displays continues to rise, there's a need to develop liquid crystal films with higher contrast, faster response speeds, and wider viewing angles. In the dimming field, there's also an urgent need for liquid crystal films that offer precise dimming, excellent stability, and low energy consumption. However, existing liquid crystal film preparation processes are often complex and costly, hindering large-scale production and widespread application. To address this issue, we propose a liquid reverse-dyed liquid crystal film, preparation method, and display device. Summary of the Invention

[0003] The object of the present invention is to provide a liquid reverse-dyed liquid crystal film, a preparation method and a display device to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a liquid reverse-dyed liquid crystal film comprising the following components: Negative nematic liquid crystal: 50%-80%; Organic dyes: 1%-10%; Gel polymer: 5%-20%; Additives: 0.1%-5%; The liquid crystal film also includes two layers of polyimide (PI) vertically oriented conductive films, which are formed by magnetron sputtering an ITO layer on a PET substrate and then coating it with a PI vertical orientation agent. The contrast of the liquid crystal film under the action of an electric field is ≥1000:1 (ISO 13406-2 standard).

[0005] Furthermore, the organic dye is an azo dye, anthraquinone dye or a black azo dye, and the absorption peak wavelength is 450-600nm.

[0006] Furthermore, the gel polymer is polymethyl methacrylate (PMMA) with a molecular weight of 50,000-200,000, and the surfactant of the additive is fluorocarbon, and the plasticizer is phthalate.

[0007] Furthermore, the light resistance of the liquid crystal film satisfies the color difference of ≤5 after an accelerated aging test (500 hours, 50 kLux) (CIE 1976 standard).

[0008] A method for preparing a solid-state dyed liquid crystal film comprises the following steps: Step 1: Preparation of PI vertically oriented conductive film: magnetron sputtering of an ITO layer with a square resistance of 50-180Ω on a PET substrate, coating of a PI vertically oriented agent and forming a vertically oriented layer by photoalignment; Step 2: Prepare a mixed solution by stirring the negative nematic liquid crystal, organic dye, gel polymer and additives at 40-60°C and 200-500 rpm for 2-4 hours until homogeneous; Step 3: Coating and curing: Coat the mixed liquid on the PI vertically aligned conductive film, adhere another layer of PI vertically aligned conductive film, and cure it under 365nm ultraviolet light for 1-5 minutes to form a liquid crystal film.

[0009] Furthermore, the sheet resistance of the ITO layer in step 1 is 80-120Ω, the stirring temperature in step 2 is 50°C, and the UV intensity in step 3 is 15-25mW / cm A liquid reverse dyeing liquid crystal film display device, the response time of the display device is ≤ 10ms (τ on / τ off ), and the horizontal viewing angle ≥±80° and the vertical viewing angle ≥±75°.

[0010] Furthermore, the display device is smart dimming glass or a flexible display device, wherein the conductive substrate is a flexible polyimide (PI) film.

[0011] Furthermore, the driving voltage of the liquid crystal film is ≤8V (AC, 1kHz), and the high temperature stability satisfies that the transmittance decay is ≤3% after continuous operation at 85°C for 1000 hours.

[0012] The present invention has at least the following beneficial effects: (1) High contrast and color expression of the present invention: By adding specific organic dyes, it can effectively absorb light of specific wavelengths, significantly improving the contrast and color expression of the liquid crystal film, making the displayed image clearer and more vivid; (2) Fast response speed of the present invention: The characteristics of negative nematic liquid crystal and the optimized preparation process enable the liquid crystal film to change its molecular arrangement rapidly under the action of an electric field. The response speed is increased by 30%-50% compared with traditional liquid crystal films, which can meet the needs of high-speed dynamic image display; (3) Wide viewing angle of the present invention: The unique molecular arrangement and polymer network structure give the liquid crystal film a wider viewing angle. When viewed at different angles, the brightness and color of the image change less, improving the viewing experience; (4) The preparation process of the present invention is simple: it uses common raw materials and conventional preparation processes, such as mixing, film forming and ultraviolet light curing, which is easy to operate and control, suitable for large-scale industrial production, reduces production costs and improves production efficiency. DETAILED DESCRIPTION

[0013] The embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0014] Composition of the liquid reverse-dyed liquid crystal film: The liquid reverse-dyed liquid crystal film of the present invention comprises a PI oriented conductive film, a liquid crystal host, a dye, a polymer network, and additives. The PI oriented conductive film is a PET magnetron sputtered with ITO followed by a PI vertical alignment layer. The liquid crystal host is a negative nematic liquid crystal, comprising 50%-80% of the total mass of the liquid crystal film. It exhibits birefringence and can change its molecular orientation under the influence of an electric field, thereby modulating light. The dye is an organic dye with a specific structure, comprising 1%-10%, which absorbs light of specific wavelengths, enhancing the contrast and color expression of the liquid crystal film. The gel polymer, comprising 5%-20%, serves to stabilize the liquid crystal and dye molecules and improve the stability of the liquid crystal film. Additives, including surfactants and plasticizers, comprise a total of 0.1%-5%, and are used to improve the processing and other properties of the liquid crystal film.

[0015] Preparation method: Preparation of PI conductive oriented film: magnetron sputter an ITO conductive layer on PET with a sheet resistance of 50-180Ω, preferably 80-120Ω, then apply a layer of PI orientation agent, and finally use photo-alignment for vertical alignment to form a PI vertically oriented conductive film; Use a dispensing machine to dispense the frame sealant on the PI vertically oriented film to form the outline of the required sample; Weigh negative nematic liquid crystal, organic dye, gel polymer, and additives in proportion. The gel polymer is PMMA, and the initiator is a benzoin ether photoinitiator. Add the above raw materials into the reaction vessel and stir at 40-60°C and 200-500 r / min for 2-4 hours to fully mix them; The mixed liquid is evenly coated on the PI vertically oriented film by blade coating, spin coating or spraying, with a thickness of 5-100 μm, preferably 10-20 μm; Laminating another layer of PI vertical alignment film onto the substrate coated with the liquid reverse-dyed liquid crystal polymer; Place the coated substrate into a UV curing device and cure it under UV light with a wavelength of 365nm for 1-5 minutes to make the frame adhere to the two layers of PI vertical alignment film, thereby fixing the liquid crystal molecules and dye molecules to obtain a liquid reverse-dyed liquid crystal film.

[0016] Example 1: Optimal Ratio and Process (High Contrast Display Application) Material ratio (mass percentage): Negative nematic liquid crystal (refractive index = 0.18, Merck E7): 70%; Organic dye (azo red dye, absorption peak 550nm): 5%; Gel polymer (PMMA, molecular weight 100,000): 15%; Photoinitiator (benzoin dimethyl ether 651): 3%; Surfactant (fluorocarbon FC-4430): 1%; Plasticizer (dioctyl phthalate DOP): 1%.

[0017] Preparation steps: 1. Preparation of PI conductive oriented film: An ITO layer (square resistance 100Ω) was magnetron sputtered on a PET substrate, and a PI vertical alignment agent (JSR AL3046) was coated. After photoalignment, a vertical alignment layer was formed. 2. Preparation of mixed solution: Liquid crystal, dye, PMMA, photoinitiator, surfactant and plasticizer were added into a reactor and stirred at 300 r / min at 50° C. for 3 hours until homogeneous. 3. Coating and curing: The mixed solution was coated on the PI alignment film using a doctor blade coating method to a film thickness of 15 μm. Lay another PI oriented film on the surface of the film and apply ultraviolet light (365nm, intensity 20mW / cm 2 ) Curing for 3 minutes. Performance testing: Contrast ratio: 1500:1 (test standard ISO 13406-2); Response time: 5ms / 8ms (driving voltage 5V, 1kHz); Viewing angle range: horizontal ±85°, vertical ±80° (brightness attenuation <50%); Color gamut coverage: 92% (CIE 1931 chromaticity diagram).

[0018] Example 2: Dye Type Comparison (Enhancing Color Expression)* Material ratio: Negative liquid crystal: 65%; Organic dye (anthraquinone blue dye, absorption peak 450nm): 8%; Gel polymer (PMMA): 20%; Photoinitiator: 3%; Other additives: 4%.

[0019] Preparation steps: Same as Example 1, but the dye type is replaced by anthraquinone blue dye. Performance testing: Contrast ratio: 1300:1; Response time: 6ms / 9ms; Color gamut coverage: 95% (blue purity significantly improved); Light resistance: After accelerated aging test (500 hours, 50kLux), the color difference is <3 (better than the color difference of Example 1 = 5). Example 3: Low Dye Content Solution (Dimming Film Application) Material ratio: Negative liquid crystal: 80%; Organic dyes (black azo dyes): 1.5%; Gel polymer: 10%; Photoinitiator: 2%; Plasticizer: 1%; Surfactant: 0.5%; Preparation steps: The coating film thickness was adjusted to 10 μm, and the UV curing time was extended to 4 minutes to increase the cross-linking density. Performance testing: Transmittance adjustment range: transparent state 85%, fog state 5% (driving voltage 8V); Fog switching speed: Fully transparent → Fully foggy: 200ms (suitable for smart windows); High temperature resistance: Continuous working for 1000 hours at 85℃, light transmittance attenuation <2%.

[0020] Example 4: No dye control group (comparative analysis)** Material ratio: Negative liquid crystal: 75% Gel polymer: 20% Photoinitiator: 3% Additives: 2% Preparation steps: Same as Example 1, but without adding organic dye. Performance testing: Contrast ratio: 200:1 (significantly lower than dye-containing solutions); Color gamut coverage: 65% (inadequate color expression); Response time: 4ms / 7ms (the dye has a slight effect on molecular motion).

[0021] Example Design Description 1. Example 1: Demonstrates the optimal ratio, highlighting high contrast and wide viewing angle, suitable for high-end display devices. 2. Example 2: Verify the adjustability of color expression and improvement of light fastness by optimizing dye types. 3. Example 3: For dimming scenarios, reduce the dye content and optimize the process to achieve fast fog-through switching. 4. Example 4: Control group demonstrates the key role of dyes on contrast and color. PET / ITO substrate: provides electrical conductivity and mechanical support. PI vertical alignment layer: induces vertical alignment of liquid crystal molecules. Liquid crystal / dye / polymer layer: core functional layer, realizing electrically controlled optical modulation. UV curing glue frame: seals and fixes the membrane structure. Supplementary Notes Data reliability: All tests are conducted using industry-standard equipment. Process scalability: The coating method (blade coating, spin coating) in the embodiment can be flexibly selected according to production requirements. Claim coverage: Examples include dye content (1%-10%), gel polymer ratio (5%-20%), It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0022] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A liquid reverse-dyed liquid crystal film, characterized in that: Contains the following components: Negative nematic liquid crystal: 50%-80%; Organic dyes: 1%-10%; Gel polymer: 5%-20%; Additives: 0.1%-5%; The liquid crystal film also includes two layers of polyimide (PI) vertically oriented conductive films, which are formed by magnetron sputtering an ITO layer on a PET substrate and then coating it with a PI vertical orientation agent. The contrast of the liquid crystal film under the action of an electric field is ≥1000:1 (ISO 13406-2 standard).

2. The solid-state dyed liquid crystal film according to claim 1, characterized in that: The organic dye is an azo dye, anthraquinone dye or a black azo dye, and the absorption peak wavelength is 450-600nm.

3. The solid-state dyed liquid crystal film according to claim 1, characterized in that: The gel polymer is polymethyl methacrylate (PMMA) with a molecular weight of 50,000-200,000, and the surfactant of the additive is fluorocarbon and the plasticizer is phthalate.

4. The solid-state dyed liquid crystal film according to claim 1, characterized in that: The light resistance of the liquid crystal film meets the color difference of ≤5 after an accelerated aging test (500 hours, 50 kLux) (CIE 1976 standard).

5. The method for preparing a solid-state dyed liquid crystal film according to claim 1, wherein: The following steps are involved: Step 1: Preparation of PI vertically oriented conductive film: magnetron sputtering of an ITO layer with a square resistance of 50-180Ω on a PET substrate, coating of a PI vertically oriented agent and forming a vertically oriented layer by photoalignment; Step 2: Prepare a mixed solution by stirring the negative nematic liquid crystal, organic dye, gel polymer and additives at 40-60°C and 200-500 rpm for 2-4 hours until homogeneous; Step 3: Coating and curing: Coat the mixed liquid on the PI vertically aligned conductive film, adhere another layer of PI vertically aligned conductive film, and cure it under 365nm ultraviolet light for 1-5 minutes to form a liquid crystal film.

6. The method for preparing a solid-state dyed liquid crystal film according to claim 5, wherein: The sheet resistance of the ITO layer in step 1 is 80-120Ω, the stirring temperature in step 2 is 50°C, and the UV intensity in step 3 is 15-25mW / cm 2 The coating method is blade coating or spin coating, and the film thickness is 10-20μm.

7. The display device of a liquid reverse-dyed liquid crystal film according to claim 1, characterized in that: The response time of the display device is ≤10ms (τ on / τ off ), and the horizontal viewing angle ≥±80° and the vertical viewing angle ≥±75°.

8. The method for preparing a solid-state dyed liquid crystal film according to claim 7, wherein: The display device is smart dimming glass or a flexible display device, wherein the conductive substrate is a flexible polyimide (PI) film.

9. The method for preparing a solid-state dyed liquid crystal film according to claim 7, wherein: The driving voltage of the liquid crystal film is ≤8V (AC, 1kHz), and the high temperature stability satisfies that the transmittance decay is ≤3% after continuous operation at 85°C for 1000 hours.