Insulating ceramic gasket for liquid crystal display and method for manufacturing the same

Abstract

An insulating ceramic gasket for liquid crystal display and its preparation method. The gasket comprises a ceramic matrix composed of a main crystal phase, an auxiliary phase and a reinforcing phase, has a gradient density structure, low dielectric constant, small dielectric loss and high volume resistivity. The surface has a micro-nano composite texture, which gives anisotropic wetting characteristics; the inside has a directional pore structure; the reinforcing phase is distributed in a three-dimensional network, with higher edge density than the center; and the surface is covered with a gradient functional coating. The preparation method comprises high-energy ball milling to prepare powder, in-situ reaction to generate auxiliary phase, multi-layer lamination and magnetic field assisted forming, two-step atmosphere sintering, laser micro-texturing and coating deposition. The present application provides excellent electrical insulation, mechanical strength and durability, and is suitable for high-precision liquid crystal display.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic display manufacturing, in particular to an insulating ceramic gasket for liquid crystal display and a preparation method thereof. BACKGROUND

[0002] Liquid crystal display (LCD) is widely used in electronic devices, and its performance depends on the electrical insulation, mechanical strength and thermal stability of internal components. Traditional insulating gaskets are mostly made of glass or polymer materials, but these materials are prone to high dielectric loss, insufficient mechanical strength or aging under high temperature, high humidity or high electric field environment. In recent years, ceramic materials have attracted attention due to their excellent electrical insulation and high temperature resistance, but existing ceramic gaskets have problems such as many grain boundary defects, thermal stress concentration and poor surface wettability, which limit their application in high-precision liquid crystal displays. In addition, traditional ceramic preparation processes cannot achieve structural optimization, such as gradient density or directional reinforcement, resulting in insufficient durability of the gasket under complex stress environment. Therefore, there is an urgent need for a ceramic gasket with excellent electrical insulation, mechanical strength and environmental adaptability and a preparation method thereof to meet the demand for high reliability and long service life of liquid crystal display. SUMMARY

[0003] The purpose of the present application is to provide an insulating ceramic gasket for liquid crystal display and a preparation method thereof, which solves the problems of high dielectric loss, insufficient mechanical strength, thermal stress concentration and poor surface wettability of traditional insulating gaskets, and improves electrical insulation, mechanical strength and durability by optimizing ceramic matrix composition, gradient density structure, micro-nano composite texture and gradient functional coating; through high-energy ball milling in-situ reaction, multi-layer lamination, magnetic field assisted forming and two-step sintering process, structural optimization and performance enhancement are realized to meet the demand for reliability and long service life of high-precision liquid crystal display.

[0004] Specifically, the present application provides an insulating ceramic gasket for liquid crystal display, comprising:

[0005] a ceramic matrix composed of a main crystal phase and an auxiliary phase, wherein,

[0006] the main crystal phase is β-Si3N4 crystal phase, and the weight percentage is 65-85%;

[0007] the auxiliary phase includes Y2Si2O7 rare earth silicate phase and Al2O3·Y2O3 composite oxide phase, and the weight percentages are 8-15% and 5-12% respectively;

[0008] the ceramic matrix further contains nano-sized SiC whiskers as reinforcing phase, and the mass fraction is 0.5-2%, and the aspect ratio of the SiC whiskers is 10-50;

[0009] The ceramic gasket has a gradient density structure, the surface layer density is 4.2-4.8 g / cm3, and the inner layer density is 3.8-4.2 g / cm3;

[0010] The dielectric constant of the ceramic gasket is 6.5-8.2 at a frequency of 1 MHz, the dielectric loss tangent is less than 0.0005, and the volume resistivity is greater than Ω·cm.

[0011] Optionally, the surface of the ceramic matrix has a micro-nano composite texture structure, which comprises:

[0012] Micron-level pits with a depth of 0.5-2 microns and a pitch of 5-20 microns;

[0013] Nanometer-level protrusions with a height of 50-200 nanometers distributed in the micron-level pits;

[0014] The composite texture structure makes the surface of the ceramic gasket have anisotropic wetting characteristics.

[0015] Optionally, the ceramic matrix has a directional arrangement of pore structures inside, the porosity is 3-8%, the long axis of the pores is parallel to the thickness direction of the gasket, and the ratio of the long axis to the short axis is 2-5.

[0016] Optionally, the SiC whiskers are distributed in a three-dimensional network in the ceramic matrix, and the density of SiC whiskers in the edge region of the gasket is 20-40% higher than that in the center region.

[0017] Optionally, the surface of the ceramic gasket is covered with a gradient functional coating, and the coating comprises, from inside to outside:

[0018] Transition layer: Si-O-N amorphous layer with a thickness of 10-50 nm;

[0019] Functional layer: fluorine-containing polymer modified silicone layer with a thickness of 50-200 nm;

[0020] Protective layer: diamond-like carbon thin film layer with a thickness of 5-20 nm.

[0021] The application also provides a method for insulating ceramic gaskets, which comprises the following steps:

[0022] Step (1), mix β-Si3N4 powder, Y2O3 powder, Al2O3 powder, nano-SiO2 powder and SiC whiskers according to the proportion, and process them by high-energy ball milling process, the ball milling medium is silicon nitride ball, the rotation speed is 400-600 rpm, and the ball milling time is 12-20 hours;

[0023] Step (2), adopt multi-layer laminated forming technology to layer the powder with different densities into the mold, the forming pressure is 100-300 MPa, and a gradient density green body is formed.

[0024] Step (3): Under a nitrogen protective atmosphere, heat to 1750-1850℃ and hold for 4-8 hours at a heating rate of 2-4℃ / min. During the cooling process, control the cooling rate at 0.5-2℃ / min within the range of 1400-1500℃.

[0025] Step (4) uses laser micromachining technology to prepare micro-nano composite textures on the ceramic surface.

[0026] Optionally, in step (1), an in-situ reaction method is used to simultaneously carry out a chemical reaction during the ball milling process, and the reaction equation is as follows:

[0027] Y₂O₃ + 2SiO₂ → Y₂Si₂O₇

[0028] 3Y₂O₃ + 5Al₂O₃ → 2Y₃Al₅O 12

[0029] The chemical reaction is carried out under the mechanochemical action of the ball milling process, forming rare earth silicate phase and rare earth aluminate phase as auxiliary phases.

[0030] Optionally, in the gradient forming in step (2), magnetic field-assisted forming technology is used, with a magnetic field strength of 0.5-2T, so that SiC whiskers are oriented and aligned under the action of the magnetic field.

[0031] Optionally, a two-step sintering process is adopted in step (3) of the sintering process.

[0032] Step (31): Hold at 1650-1750℃ for 2-4 hours to form the main crystalline phase;

[0033] Step (32): Heat to 1750-1850℃ and hold for 4-6 hours to complete densification and form a gradient density structure.

[0034] Optionally, step (4) may be followed by a gradient coating preparation step:

[0035] Step (41): The Si-ON transition layer is prepared by plasma-enhanced chemical vapor deposition. The process parameters are: temperature 300-500℃, pressure 10-50Pa.

[0036] Step (42): The fluoropolymer-modified organosilicon functional layer is prepared by solution impregnation-heat treatment method, with a heat treatment temperature of 150-250℃;

[0037] Step (43): Prepare a diamond-like carbon protective layer by magnetron sputtering with a sputtering power of 200-500W.

[0038] This invention provides an insulating ceramic gasket for liquid crystal displays and its preparation method. Addressing the problems of high dielectric loss and insufficient mechanical strength in traditional insulating gaskets, this invention significantly reduces dielectric loss and increases volume resistivity by optimizing the composition of the main crystalline phase, auxiliary phase, and reinforcing phase of the ceramic matrix, ensuring insulation reliability under high electric field environments. To address thermal stress concentration, a gradient density structure and directional pore design are employed to effectively alleviate thermal stress and improve high-temperature stability. To address poor surface wettability, a micro-nano composite texture and gradient functional coating are introduced to impart anisotropic wetting properties and wear resistance, enhancing moisture resistance and corrosion resistance. To address the structural optimization challenges of traditional manufacturing processes, a high-energy ball milling in-situ reaction, multilayer lamination, magnetic field-assisted molding, and two-step sintering process are used to achieve directional alignment of the reinforcing phase and densification of the matrix, improving mechanical strength and durability. This invention significantly improves the overall performance of gaskets for liquid crystal displays, extends their service life, and meets the requirements of high-precision displays. Attached Figure Description

[0039] Figure 1 This is a schematic longitudinal section of the insulating ceramic gasket for a liquid crystal display screen according to the present invention;

[0040] Figure 2 A flowchart illustrating the method for producing an insulating ceramic gasket according to the present invention;

[0041] Figure 3 The data diagram of material and structural properties of the insulating ceramic gasket provided by the present invention;

[0042] Figure 4 The performance and process parameter data diagram of the insulating ceramic gasket provided by the present invention;

[0043] Figure 5 A flowchart of the sintering process method provided by the present invention;

[0044] Figure 6 A flowchart of the gradient coating preparation method provided by the present invention.

[0045] Reference numerals: 1. Insulating ceramic gasket; 2. Liquid crystal display assembly. Detailed Implementation

[0046] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this application, unless otherwise stated, "multiple" means two or more.

[0048] To more clearly illustrate the technical solution of the present invention, the present invention will be described in detail below with reference to specific embodiments, but it should not be construed as a limitation on the scope of protection of the present invention.

[0049] This embodiment provides an insulating ceramic gasket for a liquid crystal display screen, comprising: a ceramic matrix, wherein the ceramic matrix is ​​composed of a main crystalline phase and an auxiliary phase, wherein the main crystalline phase is a β-Si3N4 crystalline phase, with a weight percentage of 65-85%.

[0050] like Figure 1 As shown, Figure 1 This is a longitudinal cross-sectional schematic diagram of the insulating ceramic gasket used in a liquid crystal display screen according to the present invention. The rectangle represents the overall cross-section of the ceramic gasket. The upper light gray shaded area represents the surface high-density region, and the lower white area represents the inner low-density region, reflecting a gradient density structure. The thin, elongated lines inside the rectangle represent SiC whisker reinforcement phases, randomly distributed to form a three-dimensional network. The dot-like structures around the thin, elongated lines represent the main crystalline phase particles, occupying the main matrix; the intersecting or short line-like structures between the dots represent auxiliary phases, filling grain boundaries; the dashed frame outside the rectangle represents the liquid crystal display screen assembly.

[0051] Specifically, such as Figure 1 , Figure 3 and Figure 4 As shown, in the preparation process of this ceramic gasket, β-Si3N4 powder with a particle size of 0.5-2 micrometers is selected as the main raw material to ensure that the weight percentage of the main crystalline phase in the final ceramic matrix reaches 70%, which helps to provide good thermal stability and mechanical strength. During the sintering stage, the temperature and atmosphere are controlled to promote the growth and densification of β-Si3N4 grains, making them the main structural support for the overall insulation performance. This selection of the main crystalline phase ratio allows the gasket to maintain structural integrity in the high-temperature operating environment of the liquid crystal display, avoiding cracks caused by thermal expansion. Figure 1 As shown, the main crystal corresponds to the main region inside the rectangle, which together with the auxiliary phase forms a stable matrix structure.

[0052] Furthermore, the auxiliary phases include a Y2Si2O7 rare earth silicate phase and an Al2O3·Y2O3 composite oxide phase, with weight percentages of 8-15% and 5-12%, respectively.

[0053] Specifically, a rare-earth silicate phase, Y2Si2O7, is generated through a mechanochemical reaction by adding Y2O3 and SiO2 raw materials. The weight percentage of Y2Si2O7 is controlled at 10% to enhance the stability of the grain boundary phase and improve oxidation resistance at high temperatures. An Al2O3·Y2O3 composite oxide phase, formed through the reaction of Y2O3 and Al2O3, accounts for 8% by weight. This helps reduce the defect density at grain boundaries and improves the overall electrical insulation properties. Understandably, the introduction of these auxiliary phases reduces charge accumulation in the ceramic matrix within the electric field environment of the liquid crystal display, ensuring long-term reliable operation. Figure 1 As shown, the auxiliary filling region between the main crystalline phase particles inside the corresponding rectangle forms a continuous grain boundary interface, supporting the optimization of the electrical properties of the matrix.

[0054] Furthermore, the ceramic matrix also contains 0.5-2% by mass of nano-sized SiC whiskers as a reinforcing phase, wherein the SiC whiskers have an aspect ratio of 10-50.

[0055] Specifically, SiC whiskers with a diameter of 50-200 nanometers and an aspect ratio of 30 are selected and added to the ceramic matrix as a reinforcing phase at a mass fraction of 1%. They are uniformly dispersed to bridge grains and absorb crack propagation energy. Furthermore, high-energy ball milling is used during the mixing process to ensure that the SiC whiskers do not agglomerate, thus forming a uniform reinforcing network. Understandably, the SiC whiskers correspond to randomly distributed slender lines within a rectangle, forming a three-dimensional network structure that bridges the surface and inner layers, improving overall mechanical strength.

[0056] Furthermore, the ceramic gasket has a gradient density structure, with a surface density of 4.2-4.8 g / cm³ and an inner density of 3.8-4.2 g / cm³.

[0057] like Figure 1 As shown, the gradient density structure corresponds to the upper light gray shaded area (the surface high-density area) and the lower white area (the inner low-density area) of the rectangle, with a clear overall gradient, supporting the thermal stress relief mechanism.

[0058] Specifically, the preform is prepared using a multi-layer lamination molding technique, where the surface layer uses a powder layer with higher compaction pressure to achieve a density of 4.5 g / cm³, while the inner layer uses a powder layer with lower compaction pressure to form a density of 4.0 g / cm³. During sintering, the cooling rate is controlled to maintain this density gradient, thereby achieving a gradual structure from the surface to the interior. Understandably, this gradient density design optimizes the heat conduction path, reduces thermal stress concentration in the heat dissipation requirements of LCD displays, and improves overall durability.

[0059] Furthermore, the dielectric constant of the ceramic gasket is 6.5-8.2 at a frequency of 1MHz, the dielectric loss tangent is less than 0.0005, and the volume resistivity is greater than... Ω·cm.

[0060] Specifically, by optimizing the ratio of the main crystalline phase and auxiliary phases, as well as the dispersion of the reinforcing phase, a dielectric constant of 7.5 is ensured at a frequency of 1MHz. This minimizes the capacitive effect of the spacer in the signal transmission of the liquid crystal display. Furthermore, the dielectric loss tangent is controlled below 0.0003, achieving low energy loss by reducing grain boundary impurities and porosity. Understandably, the volume resistivity reaches... With a strength of Ω·cm or higher, the high-purity raw materials and inert atmosphere sintering process prevent the formation of conductive paths, thereby providing excellent insulation performance under high voltage conditions, making it suitable for precision electronic components of LCD displays.

[0061] This invention provides an insulating ceramic gasket for liquid crystal displays (LCDs). By optimizing the composition of the main crystalline phase, auxiliary phase, and reinforcing phase in the ceramic matrix, it significantly reduces dielectric loss, improves volume resistivity, and ensures insulation reliability under high electric field environments, effectively solving the problem of insufficient dielectric performance in traditional gaskets. Employing a gradient density structure, with a higher density on the surface layer than the inner layer, it optimizes the heat conduction path, alleviates thermal stress concentration, improves high-temperature stability, and overcomes the defect of traditional ceramic gaskets being prone to cracking due to thermal expansion. The reinforcing phase forms a network distribution, bridging cracks and significantly improving fracture toughness and mechanical strength, meeting the high-stress requirements of LCD assembly. Compared to traditional glass or polymer gaskets, the gasket of this invention exhibits superior durability and anti-aging capabilities in high-temperature and high-humidity environments, significantly extending its service life. It is particularly suitable for precision components in high-precision LCDs, improving the overall reliability and performance of the display.

[0062] In some embodiments, the ceramic substrate surface has a micro-nano-scale composite texture structure, including: micron-scale pits with a depth of 0.5-2 microns and a spacing of 5-20 microns.

[0063] Specifically, laser micromachining technology is used on the surface of a ceramic substrate to form a micron-scale array of pits with a depth of 1 micrometer and a spacing of 10 micrometers by controlling the laser pulse energy and scanning path. These pits are formed by precise laser etching to ensure a smooth surface without cracks. In addition, an ultraviolet laser with a wavelength of 355 nanometers and a pulse width of 10 nanoseconds is used during the processing to ensure the smoothness of the pit edges and the consistency of dimensions.

[0064] This micron-scale recessed structure enhances the mechanical locking capability of the surface in LCD applications, contributing to the contact stability between the gasket and other components of the display.

[0065] Furthermore, nanoscale protrusions, with a height of 50-200 nanometers, are distributed within micron-sized pits.

[0066] Specifically, nanoscale protrusions with a height of 100 nanometers are generated within micrometer-scale pits using chemical vapor deposition (CVD). Silica protrusions are formed by depositing a silicon-containing precursor (such as tetraethoxysilane) at 600°C. These protrusions are uniformly distributed on the bottom and sidewalls of the pits, with a density of approximately [missing information]. The number of protrusions per cm² was controlled. Simultaneously, the gas pressure was maintained at 50 Pa during deposition to ensure consistency in protrusion height and morphology. Understandably, these nanoscale protrusions increase the specific surface area, improving interfacial adhesion with bonding materials in the assembly environment of liquid crystal displays.

[0067] Furthermore, the composite texture structure gives the ceramic gasket surface anisotropic wetting properties.

[0068] Specifically, through a composite design of micron-level pits and nano-level protrusions, the ceramic gasket surface achieves an anisotropic wetting characteristic with a contact angle of 120° parallel to the pit array direction and 90° perpendicular to it. This wetting characteristic is achieved through surface energy modulation; the geometry of the pits and protrusions causes different diffusion behaviors of the liquid in different directions, thereby reducing liquid penetration in the humid environment of the LCD screen. Understandably, this anisotropic wetting characteristic improves the gasket's moisture resistance, ensuring that it maintains electrical insulation performance under high humidity conditions, making it suitable for the long-term stable operation of LCD screens.

[0069] In some embodiments, an insulating ceramic gasket for a liquid crystal display is described, wherein the ceramic matrix has a specific pore structure to improve thermal stress relief and mechanical stability, and is suitable for long-term operation of the liquid crystal display in high temperature and high humidity environments.

[0070] Specifically, the ceramic matrix has an internally oriented pore structure with a porosity of 3-8%.

[0071] In the preparation of the ceramic matrix, a controllable organic porosifactor (such as polymethyl methacrylate particles with a particle size of 1-5 micrometers) is introduced during the multilayer lamination stage. During sintering, the matrix is ​​heated to 1750°C at a heating rate of 2°C / min under a nitrogen atmosphere, causing the porosifactor to decompose and form pores, with the porosity controlled at 5%. Furthermore, the distribution of the porosifactor in the powder is optimized through a high-energy ball milling process, ensuring that the pores are uniformly distributed within the ceramic matrix but aligned in a specific direction. Understandably, this porosity design effectively alleviates thermal stress in the thermal cycling environment of liquid crystal displays, preventing microcracks caused by temperature changes.

[0072] Furthermore, the long axis of the pores is parallel to the thickness direction of the gasket, and the ratio of the long axis to the short axis is 2-5.

[0073] Specifically, by applying a uniaxial pressure (150 MPa) along the thickness direction of the gasket during the molding stage, combined with controlling the cooling rate during sintering (1 °C / min within the range of 1400-1500 °C), the pores form an elliptical structure with the long axis parallel to the thickness direction of the gasket after sintering, with a long axis to short axis ratio of 3. The long axis size of the pores is controlled within 10-20 micrometers, and the short axis within 3-7 micrometers. Their directional arrangement characteristics are verified using scanning electron microscopy (SEM). Understandably, this directional pore structure optimizes the heat conduction path during the heat dissipation process of the liquid crystal display, reduces the difference in thermal expansion along the thickness direction, and improves the dimensional stability of the gasket.

[0074] In some embodiments, an insulating ceramic gasket for a liquid crystal display is described, wherein the specific distribution characteristics of nanoscale SiC whiskers in the ceramic matrix enhance the gasket’s mechanical strength and edge abrasion resistance, making it suitable for the high-stress environment of the liquid crystal display during assembly and operation.

[0075] Specifically, the SiC whiskers are distributed in a three-dimensional network within the ceramic matrix. During the preparation of the ceramic matrix, SiC whiskers with a diameter of 50-200 nanometers (aspect ratio of 30) are mixed with β-Si3N4 powder and other raw materials using a high-energy ball milling process at 500 rpm for 15 hours to ensure uniform dispersion of the SiC whiskers in the powder. Furthermore, in the multilayer lamination stage, by controlling the proportion of SiC whiskers added to the powder layers, a three-dimensional network structure is formed, in which the SiC whiskers interweave within the matrix, resembling a mesh-like reinforcing framework. Understandably, this three-dimensional network distribution improves the crack propagation resistance of the ceramic matrix and enhances the overall toughness of the gasket in the mechanical vibration environment of the liquid crystal display screen.

[0076] Furthermore, the SiC whisker density in the edge region of the gasket is 20-40% higher than that in the central region. During the molding process, the mass fraction of SiC whiskers in the powder layer at the mold edge is increased (from 1% in the central region to 1.3% in the edge region), and magnetic field-assisted molding technology (magnetic field strength 1T) is used to preferentially enrich the SiC whiskers in the edge region, resulting in a 30% higher SiC whisker density in the edge region compared to the central region. In addition, the high-density SiC whisker structure in the edge region is ensured to be fixed by controlling the nitrogen atmosphere and the sintering temperature of 1750℃ during the sintering process. Understandably, this high-density edge design improves wear resistance and impact resistance during the edge fixing and cutting processes of the LCD display, extending the service life of the gasket.

[0077] In some embodiments, an insulating ceramic gasket for a liquid crystal display is described, the surface of which is covered with a specific gradient functional coating to improve abrasion resistance, chemical stability and electrical insulation properties, suitable for long-term stable operation of the liquid crystal display in high humidity and complex chemical environments.

[0078] Specifically, there is a transition layer, a 10-50 nm thick Si-ON amorphous layer. Essentially, a 30 nm thick Si-ON amorphous layer is deposited on the ceramic substrate surface using plasma-enhanced chemical vapor deposition (PECVD). Silane (SiH4), ammonia (NH3), and oxygen (O2) are used as reactant gases, with process parameters of 400°C and 30 Pa. During deposition, the gas flow ratio (SiH4:NH3:O2 = 2:1:0.5) is controlled to ensure a uniform amorphous structure of the Si-ON layer without significant grain boundary defects. This transition layer provides good adhesion and chemical stability to the ceramic substrate in the assembly and operation environment of the liquid crystal display, preventing coating peeling and enhancing the adhesion of subsequent functional layers.

[0079] Furthermore, the coating also includes a functional layer, a fluoropolymer-modified silicone layer with a thickness of 50-200 nm. Understandably, a 100 nm thick fluoropolymer-modified silicone layer is prepared on the transition layer surface via a solution impregnation-heat treatment process. The ceramic substrate is impregnated with a fluorinated polysiloxane solution (5 wt%), followed by heat treatment at 200°C for 2 hours to cure the coating. The introduction of the fluoropolymer is achieved by adding tetrafluoroethylene monomer at a mass fraction of 20% to optimize the coating's hydrophobicity and corrosion resistance. Understandably, this functional layer significantly reduces surface liquid adsorption in the high humidity environment of liquid crystal displays, protecting the ceramic substrate from moisture corrosion while maintaining low dielectric loss, making it suitable for high-frequency signal transmission.

[0080] Furthermore, a protective layer is included, consisting of a 5-20 nm thick diamond-like carbon (DLC) thin film. Specifically, a 10 nm thick DLC thin film is deposited on the surface of the functional layer using magnetron sputtering with a graphite target, a sputtering power of 300 W, a working pressure of 0.5 Pa, and argon as the carrier gas. During deposition, a -100 V bias voltage is applied to control the sp³ carbon bond ratio of the DLC layer to over 70%, ensuring high hardness and a low coefficient of friction. Understandably, this protective layer provides excellent wear resistance and scratch resistance during the assembly and operation of the liquid crystal display, protecting the underlying coating and ceramic substrate from mechanical damage and extending the lifespan of the gaskets.

[0081] This invention also includes a method for preparing an insulating ceramic gasket for a liquid crystal display screen, such as... Figure 2As shown, a gasket with excellent insulation properties and mechanical strength is prepared through specific powder preparation, molding, sintering and surface texturing processes, which is suitable for the application of liquid crystal displays in high-precision and high-temperature environments.

[0082] Step (1) is the step of preparing composite powder. β-Si3N4 powder, Y2O3 powder, Al2O3 powder, nano-SiO2 powder and SiC whiskers are mixed in proportion and processed by high-energy ball milling. The ball milling media is silicon nitride balls, the rotation speed is 400-600 rpm, and the ball milling time is 12-20 hours.

[0083] Specifically, β-Si3N4 powder (particle size 0.5-2 μm, 70% by weight), Y2O3 powder (particle size 0.1-0.5 μm, 10% by weight), Al2O3 powder (particle size 0.2-0.8 μm, 8% by weight), and SiC whiskers (diameter 50-200 nm, aspect ratio 30, 1% by mass) were weighed according to the specified ratio and placed in a high-energy ball mill. Silicon nitride balls were used as the milling medium, with a ball-to-particle ratio of 10:1, a rotation speed of 500 rpm, and a milling time of 15 hours. Furthermore, nitrogen gas was introduced during the milling process to prevent powder oxidation, and temperature was controlled by intermittent milling (stopping for 10 minutes every 2 hours) to prevent whisker breakage. Understandably, this high-energy ball milling process ensures uniform mixing and refinement of the powder, providing a foundation for the subsequent formation of a uniform ceramic matrix and reinforcing phase distribution, suitable for the high insulation and mechanical strength requirements of liquid crystal displays.

[0084] Step (2) is a gradient molding step, which uses multi-layer stacking molding technology to load powders of different densities into the mold in layers, with a molding pressure of 100-300MPa to form a gradient density green body.

[0085] Specifically, the composite powder prepared in step (1) is divided into two parts. The surface powder is pre-compressed (50 MPa) to increase its initial density, while the inner powder remains loose. These layers are then loaded into a mold, with the surface powder having a thickness of 0.5 mm and the inner powder having a thickness of 1 mm. A molding pressure of 200 MPa is applied to form a gradient density preform. Furthermore, a precision mold is used during the molding process to ensure that the surface density reaches 4.5 g / cm³, the inner layer density reaches 4.0 g / cm³, and the preform surface is smooth and crack-free. Understandably, this multi-layer lamination molding technology optimizes the heat conduction path, reduces thermal stress concentration, and improves the durability of the gasket in the thermal management of liquid crystal displays.

[0086] Step (3) is atmosphere sintering: Under a nitrogen protective atmosphere, the temperature is raised to 1750-1850℃ and held for 4-8 hours. The heating rate is 2-4℃ / min. During the cooling process, the cooling rate is controlled at 0.5-2℃ / min within the range of 1400-1500℃.

[0087] Specifically, the green body formed in step (2) is placed in a sintering furnace under a nitrogen protective atmosphere and heated to 1800℃ at a heating rate of 3℃ / min, and held for 6 hours to promote the growth of β-Si3N4 grains and the formation of auxiliary phases. Further, during the cooling stage, the cooling rate is controlled at 1℃ / min within the range of 1400-1500℃, and programmed temperature control ensures the stability of the gradient density structure and the uniform distribution of pores. Understandably, this atmosphere sintering process ensures high density and excellent electrical insulation performance of the gaskets in the manufacture of liquid crystal displays, meeting the requirements of high-temperature operating environments.

[0088] Step (4) is surface texturing: micro-nano composite textures are prepared on the ceramic surface using laser micromachining technology.

[0089] Specifically, a 355 nm ultraviolet laser with a pulse width of 10 nanoseconds and an energy density of 0.5 J / cm² was used on the surface of the sintered ceramic gasket to fabricate a micrometer-scale array of pits with a depth of 1 μm and a spacing of 10 μm. Subsequent low-energy laser scanning (0.1 J / cm²) then formed nanometer-scale protrusions with a height of 100 nm within the pits. Furthermore, the laser scanning speed was controlled at 500 mm / s during the fabrication process to ensure the regularity and repeatability of the texture structure. Understandably, this micro-nano composite texture improves the wetting control of the gasket surface in the assembly environment of a liquid crystal display, reduces moisture penetration, and enhances long-term operational reliability.

[0090] In some embodiments, a method for preparing an insulating ceramic gasket for a liquid crystal display is described, focusing on generating an auxiliary phase through an in-situ reaction method during the preparation of composite powder to improve the electrical insulation and high-temperature stability of the ceramic matrix, which is suitable for applications of liquid crystal displays in high-frequency signal transmission and high-temperature environments.

[0091] Specifically, β-Si3N4 powder, Y2O3 powder, Al2O3 powder, nano-SiO2 powder, and SiC whiskers are mixed in a specific ratio and processed using a high-energy ball milling process. The milling media is silicon nitride balls, the rotation speed is 400-600 rpm, and the milling time is 12-20 hours. An in-situ reaction method is used to simultaneously carry out chemical reactions during the ball milling process. The reaction equations are: Y2O3 + 2SiO2 → Y2Si2O7, 3 Y2O3 + 5 Al2O3 → 2 Y3Al5O 12The reaction is carried out under the mechanochemical action of ball milling, forming rare earth silicate phase and rare earth aluminate phase as auxiliary phases.

[0092] like Figure 3 As shown, β-Si3N4 powder (particle size 0.5-2 μm, purity 99.9%, weight percentage 70%), Y2O3 powder (particle size 0.1-0.5 μm, purity 99.99%, weight percentage 10%), Al2O3 powder (particle size 0.2-0.8 μm, purity 99.95%, weight percentage 8%), SiC whiskers (diameter 50-200 nm, aspect ratio 30, mass fraction 1%), and added nano-SiO2 powder (particle size 20-50 nm, purity 99.9%, weight percentage 4%) were weighed according to the specified ratio and placed in a high-energy ball mill. The ball mill used a silicon nitride-lined jar, the grinding media were silicon nitride balls with a diameter of 5 mm, the ball-to-material ratio was 10:1, the rotation speed was set to 500 rpm, and the grinding time was 15 hours. Furthermore, to promote in-situ reaction, high-purity nitrogen gas (flow rate 0.5 L / min, purity 99.999%) was introduced during ball milling to prevent oxidation, and 0.5 wt% ethanol was added as a dispersant to reduce powder agglomeration. Mechanochemical action, through high-energy collisions, initiated the reaction of Y₂O₃ with SiO₂ to form the Y₂Si₂O₇ rare earth silicate phase, while simultaneously Y₂O₃ reacted with Al₂O₃ to form Y₃Al₅O₇. 12 The reaction mixture is a rare-earth aluminate phase (YAG), in which the SiO2 is partly derived from added nano-SiO2 and partly from the natural oxide layer on the surface of β-Si3N4 powder (approximately 0.5 wt%). The reaction process was controlled to maintain the temperature inside the vessel below 80°C using intermittent ball milling (with a 10-minute shutdown every 2 hours to cool to room temperature) to prevent overheating and damage to the whisker structure. The formation of the reaction products was verified by X-ray diffraction (XRD) analysis, confirming the presence of Y2Si2O7 and Y3Al5O7. 12 The characteristic peaks appear at 2θ = 29.8° and 33.4°, respectively, with weight percentages of 10% and 8%, consistent with the requirements for auxiliary phases in the ceramic matrix. Understandably, this in-situ reaction method efficiently generates auxiliary phases through mechanochemical action, enhancing the grain boundary strength and high-temperature oxidation resistance of the ceramic matrix. This significantly reduces dielectric loss and charge accumulation in the high-frequency electric field and thermal cycling environment of liquid crystal displays, ensuring the long-term reliability of the gasket.

[0093] In some embodiments, a method for preparing an insulating ceramic gasket for a liquid crystal display is described, focusing on achieving the directional alignment of SiC whiskers through magnetic field-assisted molding technology during gradient molding to improve the mechanical strength and thermal conductivity of the ceramic matrix, which is suitable for applications of liquid crystal displays in high-stress and thermal cycling environments.

[0094] Specifically, a multi-layer lamination molding technology is used to layer powders of different densities into a mold, with a molding pressure of 100-300MPa to form a gradient density green body. In the gradient molding process, a magnetic field-assisted molding technology is used, with a magnetic field strength of 0.5-2T, so that SiC whiskers are oriented and aligned under the action of the magnetic field.

[0095] The prepared composite powder (containing β-Si3N4 powder, Y2O3 powder, Al2O3 powder, and SiC whiskers) was divided into a surface layer and an inner layer. The surface layer powder was pre-compressed (50 MPa) to increase its initial density, while the inner layer powder remained loose. The powders were then layered and placed into a mold, with the surface layer having a thickness of 0.5 mm and the inner layer a thickness of 1 mm. A pressure of 200 MPa was applied during the molding process to form a gradient density preform with a surface density of 4.5 g / cm³ and an inner layer density of 4.0 g / cm³. Further, during the molding process, the mold was placed in a uniform magnetic field with a strength of 1 T, parallel to the thickness direction of the mold. The SiC whiskers were pre-treated with surface magnetization (depositing a 0.1 wt% nickel coating on the whisker surface) to enhance their magnetic responsiveness. Under the influence of the magnetic field, the SiC whiskers preferentially oriented along the thickness direction, with the angle between their long axis and the thickness direction less than 15°. Their directional alignment was confirmed by scanning electron microscopy (SEM). Understandably, this magnetic field-assisted molding technology enables SiC whiskers to form an ordered reinforcing network in the heat conduction path of the liquid crystal display, improving the fracture toughness and thermal conductivity along the thickness direction of the gasket, making it suitable for high-temperature operation and mechanical assembly environments.

[0096] In some embodiments, a method for preparing an insulating ceramic gasket for a liquid crystal display is described, focusing on using a two-step sintering process to form a main crystalline phase and achieve a gradient density structure, thereby improving the compactness and electrical insulation performance of the ceramic gasket, which is suitable for the stable operation of the liquid crystal display under high temperature and high electric field environments.

[0097] Specifically, under a nitrogen protective atmosphere, the temperature is raised to 1750-1850℃ and held for 4-8 hours at a rate of 2-4℃ / min. During the cooling process, the cooling rate is controlled at 0.5-2℃ / min within the range of 1400-1500℃. A two-step sintering process is adopted, such as step (31), where the temperature is held at 1650-1750℃ for 2-4 hours to form the main crystalline phase; and step (32), where the temperature is raised to 1750-1850℃ and held for 4-6 hours to complete densification and form a gradient density structure.

[0098] like Figure 5As shown, the formed gradient density green body was placed in a sintering furnace under a high-purity nitrogen protective atmosphere (nitrogen purity 99.999%, flow rate 0.5 L / min) and a two-step sintering process was adopted. In step (31), the temperature was raised to 1700℃ at a heating rate of 3℃ / min and held for 3 hours to promote the grain growth and initial bonding of the β-Si3N4 main crystal phase. X-ray diffraction (XRD) analysis confirmed that the characteristic peak of β-Si3N4 was enhanced at 2θ=27.0°, indicating the formation of the main crystal phase. Further, in step (32), the temperature was raised to 1800℃ at a heating rate of 2℃ / min and held for 5 hours. By controlling the nitrogen pressure (0.1 MPa), the densification of the ceramic matrix was promoted, and the surface density reached 4.5 g / cm³, the inner density was 4.0 g / cm³, and the gradient structure was maintained. During the cooling stage, the temperature is slowly reduced at a rate of 1℃ / min within the range of 1400-1500℃, and abnormal grain growth and stress concentration are avoided through programmed temperature control. Understandably, this two-step sintering process ensures high density and excellent electrical insulation performance of the ceramic gasket in the manufacture of LCD displays, while the gradient density structure effectively alleviates thermal stress, making it suitable for high-temperature operating environments.

[0099] In some embodiments, a method for preparing an insulating ceramic gasket for a liquid crystal display is described, focusing on preparing a gradient functional coating on the ceramic surface to enhance the gasket's abrasion resistance, hydrophobicity, and electrical insulation properties, suitable for the long-term stable operation of the liquid crystal display under high humidity, high mechanical stress, and high electric field environments.

[0100] Specifically, step (4) is followed by a gradient coating preparation step: step (41) Si-ON transition layer is prepared by plasma-enhanced chemical vapor deposition with process parameters of 300-500℃ and 10-50Pa; step (42) fluoropolymer-modified organosilicon functional layer is prepared by solution impregnation-heat treatment with a heat treatment temperature of 150-250℃; step (43) diamond-like carbon protective layer is prepared by magnetron sputtering with a sputtering power of 200-500W.

[0101] like Figure 6As shown, a gradient coating was prepared on the surface of the sintered ceramic gasket. First, in step (41), a plasma-enhanced chemical vapor deposition (PECVD) process was used. At a temperature of 400℃ and a pressure of 30Pa, silane (SiH4, flow rate 20sccm), ammonia (NH3, flow rate 10sccm), and oxygen (O2, flow rate 5sccm) were used as reaction gases to deposit a Si-ON amorphous transition layer with a thickness of 30 nanometers. The deposition time was 10 minutes to ensure that the layer was uniform and free of pinholes. Further, in step (42), a fluoropolymer-modified organosilicon functional layer was coated on the surface of the transition layer by a solution impregnation-heat treatment process. A 5wt% fluorinated polysiloxane solution (containing 20wt% tetrafluoroethylene monomer) was used. After impregnation at a pull-up speed of 2mm / s, the solution was heat-treated at 200℃ for 2 hours to form a hydrophobic functional layer with a thickness of 100 nanometers. The contact angle test showed that the surface contact angle reached 110°. Further, step (43) employs magnetron sputtering to deposit a 10-nanometer-thick diamond-like carbon (DLC) protective layer on the surface of the functional layer. A graphite target is used, the sputtering power is 300W, the argon flow rate is 50sccm, the working pressure is 0.5Pa, and a -100V bias voltage is applied to increase the sp³ carbon bond ratio to 70%. Understandably, this gradient functional coating significantly improves the wear resistance, hydrophobicity, and chemical corrosion resistance of the gasket in the assembly and operation environment of the liquid crystal display, protects the ceramic substrate from moisture and mechanical damage, and ensures insulation performance and long-term reliability under high electric fields.

[0102] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An insulating ceramic gasket for a liquid crystal display screen, characterized in that, include: The ceramic matrix is ​​composed of a main crystalline phase and an auxiliary phase, wherein, The main crystalline phase is β-Si3N4, with a weight percentage of 65-85%. The auxiliary phase comprises a Y2Si2O7 rare earth silicate phase and an Al2O3·Y2O3 composite oxide phase, with weight percentages of 8-15% and 5-12%, respectively. The ceramic matrix further comprises 0.5-2% by mass of nano-sized SiC whiskers as a reinforcing phase, wherein the SiC whiskers have an aspect ratio of 10-50. The ceramic gasket is prepared through the following steps: Step (1), powder, powder, Powder, Nano The powder and SiC whiskers are mixed in a certain proportion and processed by high-energy ball milling. The ball milling media is silicon nitride balls, the rotation speed is 400-600 rpm, and the ball milling time is 12-20 hours. In step (1), an in-situ reaction method is used to simultaneously carry out a chemical reaction during the ball milling process. The reaction equation is as follows: +2 → ; 3 + 5 → 2 ； The reaction is carried out under the mechanochemical action of the ball milling process, forming rare earth silicate phase and rare earth aluminate phase as auxiliary phases; Step (2): The composite powder obtained in step (1) is divided into two parts: surface powder and inner powder. The surface powder is pre-compressed to increase its initial density, while the inner powder remains loose. Then, the surface powder and the inner powder are layered and loaded into a mold. The surface powder is 0.5 mm thick and the inner powder is 1 mm thick. The molding pressure is 100-300 MPa to form a gradient density preform. In step (3), under a nitrogen protective atmosphere, the temperature is raised to 1750-1850℃ and held for 4-8 hours at a rate of 2-4℃ / min. During the cooling process, the cooling rate is controlled at 0.5-2℃ / min within the range of 1400-1500℃. In the sintering process of step (3), a two-step sintering process is adopted. Step (31): Hold at 1650-1750℃ for 2-4 hours to form the main crystalline phase; Step (32): Heat to 1750-1850℃ and hold for 4-6 hours to complete densification and form a gradient density structure; Step (4): Micro-nano composite textures are prepared on the ceramic surface using laser micromachining technology; The ceramic gasket is prepared into a gradient density structure by means of multi-layer lamination molding technology and sintering temperature control procedure, wherein the surface layer density is 4.2-4.8 g / cm³ and the inner layer density is 3.8-4.2 g / cm³. The ceramic gasket has a dielectric constant of 6.5-8.2 at 1MHz, a dielectric loss tangent of less than 0.0005, and a volume resistivity greater than [missing value]. Ω·cm.

2. The insulating ceramic gasket according to claim 1, characterized in that, The ceramic matrix surface has a micro-nano-scale composite texture structure, including: Micrometer-scale pits, with a depth of 0.5-2 micrometers and a spacing of 5-20 micrometers; Nanoscale protrusions, 50-200 nanometers in height, are distributed within micrometer-sized pits; The composite texture structure gives the ceramic gasket surface anisotropic wetting properties.

3. The insulating ceramic gasket according to claim 1, characterized in that, The ceramic matrix has an oriented pore structure with a porosity of 3-8%. The long axis of the pores is parallel to the thickness direction of the gasket, and the ratio of the long axis to the short axis is 2-5.

4. The insulating ceramic gasket according to claim 1, characterized in that, The SiC whiskers are distributed in a three-dimensional network in the ceramic matrix, and the SiC whisker density in the edge region of the gasket is 20-40% higher than that in the central region.

5. The insulating ceramic gasket according to claim 1, characterized in that, The ceramic gasket surface is covered with a gradient functional coating, the coating consisting of, from the inside out: Transition layer: Si-ON amorphous layer with a thickness of 10-50nm; Functional layer: a fluoropolymer-modified organosilicon layer with a thickness of 50-200 nm; Protective layer: a diamond-like carbon thin film layer with a thickness of 5-20nm.

6. The insulating ceramic gasket according to claim 1, characterized in that, In the gradient forming process of step (2), magnetic field-assisted forming technology is used, with a magnetic field strength of 0.5-2T, so that SiC whiskers are oriented and aligned under the action of the magnetic field.

7. The insulating ceramic gasket according to claim 1, characterized in that, Step (4) is followed by a gradient coating preparation step: Step (41): The Si-ON transition layer is prepared by plasma-enhanced chemical vapor deposition. The process parameters are: temperature 300-500℃, pressure 10-50Pa. Step (42): The fluoropolymer-modified organosilicon functional layer is prepared by solution impregnation-heat treatment method, with a heat treatment temperature of 150-250℃; Step (43): Prepare a diamond-like carbon protective layer by magnetron sputtering with a sputtering power of 200-500W.

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