Low-reflection tungsten-based ceramic target material, preparation method and application thereof

Abstract

The application provides a low-reflection tungsten-based ceramic target material and a preparation method and application thereof. Compared with the prior art, a single component or a simple mixed raw material system is used in a traditional target material preparation process, and the particle size matching degree of a multi-phase material is not accurately controlled. A pressureless sintering process is used in the prior art, so that the material density is insufficient. The particle size of multiple components is synergistically controlled through stage ball milling, and a pressure-assisted sintering process is combined, so that the crystal boundary bonding state is effectively improved. Through the technical scheme of the application, the target material prepared can form a dense and uniform grain size film structure after sputtering, and the scattering loss of light at the crystal boundary is reduced. The synergistic effect of the multi-phase material system reduces the reflectivity of the film surface, so that the display device prepared can still maintain clear image contrast in a strong light environment.

Description

Technical Field

[0001] This invention belongs to the field of display device manufacturing technology, specifically relating to a low-reflection tungsten-based ceramic target, its preparation method, and its application. Background Technology

[0002] OLED screens have become widely used in small-sized high-end electronic products such as mobile phones and computers due to their advantages, including high contrast, excellent black levels from self-emissive technology, thinner and lighter design, fast response time, wide viewing angles, good color reproduction, flexible power consumption, and flexible design. Compared to traditional LCD screens, the contrast and color advantages brought by self-emissive technology are currently the most critical advantages in applications. However, OLED screens still face serious glare problems when used in strong light environments. This is mainly due to two factors: first, the reflection, refraction, and diffuse reflection of light on the screen glass surface cause the displayed content to be suppressed by ambient light; second, insufficient screen brightness makes it difficult to completely counteract strong light interference, even at the highest brightness setting.

[0003] Thin-film materials are a crucial component in the OLED screen manufacturing process, playing a key role in multiple functional layers such as the electrode layer, insulating layer, reflective layer, and encapsulation layer. Among these, the reflective layer significantly impacts light extraction efficiency and reduces internal reflection, directly affecting the screen's visual presentation. Currently, there is no effective thin-film structure solution on the market to address the glare problem in strong light environments, severely limiting the user experience of high-end display devices in outdoor and other high-light conditions.

[0004] To address this issue, display panel manufacturers are actively developing novel thin-film underlayer structures. Magnetron sputtering, a crucial method for fabricating functional thin films, relies heavily on the performance of its target material, which directly impacts the final film quality. Developing a magnetron sputtering target with low reflectivity, enabling the sputtered thin film structure to effectively reduce screen reflection, has become a pressing technical challenge in the display technology field. This type of target not only holds significant application value in OLED displays but also shows broad application prospects in other display technologies such as LCD. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a method for preparing a low-reflectivity tungsten-based ceramic target, which achieves synergistic control of multi-component particle size through staged ball milling, and effectively improves the grain boundary bonding state by combining a pressure-assisted sintering process.

[0006] The present invention also provides a low-reflection tungsten-based ceramic target.

[0007] This invention also provides the application of low-reflection tungsten-based ceramic targets in the fabrication of display devices.

[0008] The first aspect of the present invention provides a method for preparing a low-reflection tungsten-based ceramic target, comprising the following steps:

[0009] S1: Take samples of tungsten powder, yttrium oxide powder, and zinc oxide powder at a mass ratio of 68-75:12-15:16-20, add water to each sample and ball mill them for the first time to obtain tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry;

[0010] S2: The tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry are mixed and then subjected to a second ball milling to obtain a mixed slurry;

[0011] S3: After spray granulation of the mixed slurry, powder is obtained, and the powder is injected into a hot pressing sintering furnace for sintering to obtain a target material semi-finished product;

[0012] S4: The target material semi-finished product is finely processed to obtain the low-reflection tungsten-based ceramic target material.

[0013] One technical solution of the present invention relating to the preparation method of low-reflection tungsten-based ceramic target material has at least the following beneficial effects:

[0014] This invention provides a low-reflection tungsten-based ceramic target, its preparation method, and its application. By precisely controlling the proportion of tungsten-based composite materials and a staged sintering process, a dense ceramic target with low resistivity is formed. The thin film formed by magnetron sputtering of this target can effectively reduce screen reflection, solving the technical problem of severe reflection of display devices in strong light environments, and has the significant advantage of improving the outdoor visibility of display devices.

[0015] According to some embodiments of the present invention, the mass ratio of tungsten powder, yttrium oxide powder, and zinc oxide powder is 70-75:13-15:17-20.

[0016] According to some embodiments of the present invention, the particle size of the solid particles in the tungsten powder slurry is 0.3 to 0.5 micrometers.

[0017] According to some embodiments of the present invention, the particle size of the solid particles in the tungsten powder slurry is any value among 0.3 micrometers, 0.35 micrometers, 0.4 micrometers, 0.45 micrometers and 0.5 micrometers, such as 0.4 micrometers, or any range formed by both, such as 0.35 micrometers to 0.4 micrometers.

[0018] According to some embodiments of the present invention, the particle size of the solid particles in the yttrium oxide slurry is 0.12 to 0.22 micrometers.

[0019] According to some embodiments of the present invention, the particle size of the solid particles in the yttrium oxide slurry is any value among 0.12 micrometers, 0.14 micrometers, 0.16 micrometers, 0.18 micrometers, 0.2 micrometers, and 0.22 micrometers, such as 0.16 micrometers, or any range formed by both, such as 0.16 micrometers to 0.2 micrometers.

[0020] According to some embodiments of the present invention, the particle size of the solid particles in the zinc oxide slurry is 0.12 to 0.22 micrometers.

[0021] According to some embodiments of the present invention, the particle size of the solid particles in the zinc oxide slurry is any value among 0.12 micrometers, 0.14 micrometers, 0.16 micrometers, 0.18 micrometers, 0.2 micrometers, and 0.22 micrometers, such as 0.16 micrometers, or any range formed by both, such as 0.16 micrometers to 0.2 micrometers.

[0022] According to some embodiments of the present invention, the second ball milling time is 12h to 20h.

[0023] According to some embodiments of the present invention, the second ball milling time is any value of 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, such as 15h, or a range of any two, such as 14h to 18h.

[0024] According to some embodiments of the present invention, the sintering includes a first-stage sintering and a second-stage sintering. The method of the first-stage sintering includes: heating to 850°C to 1050°C at a rate of 10°C / min to 20°C / min under normal pressure and holding at that temperature for 2 hours. The method of the second-stage sintering includes: increasing the pressure from normal pressure to 25MPa at a rate of 3MPa / min and holding at that pressure for 1 hour, heating to 150°C to 1580°C at a rate of 10°C / min to 15°C / min and holding at that temperature for 10 hours.

[0025] The second aspect of the present invention provides a low-reflection tungsten-based ceramic target material, which is prepared by the method of the first aspect of the present invention.

[0026] According to some embodiments of the present invention, the low-reflection tungsten-based ceramic target has a relative density greater than 94% and a resistivity less than 6.03 × 10⁻⁶. -4 Ω·cm.

[0027] The third aspect of the present invention provides the application of the low-reflection tungsten-based ceramic target prepared by the preparation method of the first aspect of the present invention or the low-reflection tungsten-based ceramic target of the second aspect of the present invention in the preparation of display devices. Attached Figure Description

[0028] Figure 1 The image shows the microstructure of the material in Example 3.

[0029] Figure 2 The low-reflection film prepared using the target material of this invention is based on the principle of low reflection inside an OLED. Detailed Implementation

[0030] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0031] In a first aspect, some embodiments of the present invention provide a method for preparing a low-reflectivity tungsten-based ceramic target, comprising the following steps:

[0032] S1: Take samples of tungsten powder, yttrium oxide powder, and zinc oxide powder at a mass ratio of 68-75:12-15:16-20, add water to each sample and ball mill them for the first time to obtain tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry;

[0033] S2: Tungsten powder slurry, yttrium oxide powder slurry and zinc oxide powder slurry are mixed and then ball-milled a second time to obtain a mixed slurry;

[0034] S3: After spray granulation of the mixed slurry, powder is obtained. The powder is injected into a hot press sintering furnace for sintering to obtain a target material semi-finished product.

[0035] S4: The target material semi-finished product is finely processed to obtain the low-reflection tungsten-based ceramic target material of the present invention.

[0036] In existing technologies, OLED screens exhibit significant glare under strong light conditions, primarily due to light reflection from the screen surface and light scattering caused by the internal structure. Traditional reflective layer materials are ineffective at reducing light reflectivity, leading to decreased contrast in the displayed content. Current magnetron sputtering target fabrication processes suffer from insufficient control over raw material ratios and sintering processes, making it difficult to form thin film structures with low reflectivity, thus limiting their application in display devices.

[0037] To address the aforementioned issues, this study investigated the influence of target material composition uniformity and microstructure on reflectivity. Traditional single-metal targets suffer from high grain boundary reflectivity, while composite ceramic materials can improve performance, but the interfacial bonding strength of multiphase materials is insufficient. By introducing a multi-component oxide composite system, this study attempted to optimize grain size distribution and phase interface bonding. Further investigation revealed that controlling the raw material powder particle size and sintering process parameters can regulate grain growth behavior, thereby reducing light scattering from the material surface.

[0038] Therefore, this application proposes a preparation method including the following steps: taking samples of tungsten powder, yttrium oxide powder, and zinc oxide powder in a mass ratio of 68-75:12-15:16-20, adding water to each and ball milling them for the first time to obtain three slurries; mixing the slurries and ball milling them for the second time to obtain a mixed slurry; spray granulating the mixed slurry and sintering it, and finally refining it to obtain the target material.

[0039] The process involves several steps: First, ball milling, which mechanically grinds the powder to a specific fineness using a planetary ball mill with zirconia grinding balls. This process eliminates agglomeration of the raw material powder. Second, ball milling, which homogenizes a multi-component slurry using wet ball milling, creates a uniformly dispersed system of different material particles. Third, spray granulation, which atomizes the slurry into tiny droplets and then rapidly dries them using a centrifugal atomizer with a hot air drying system, produces free-flowing spherical particles. Fourth, hot-pressing sintering, which densifies the material under external pressure at high temperatures using a graphite mold loaded with powder and heated in a protective atmosphere, reduces the material's internal porosity.

[0040] Specifically, the three raw material powders are ball-milled twice to form a mixed system with controllable particle size distribution. Tungsten powder serves as the matrix, providing conductivity, while yttrium oxide and zinc oxide form a dispersed second phase during sintering. Spray granulation creates spherical particles, which facilitates a uniform grain structure during sintering. The axial pressure applied during hot-pressing promotes close contact between particles, inhibiting the formation of pores at grain boundaries. The finishing process removes the surface oxide layer through machining, ultimately obtaining a target material with a smooth surface.

[0041] Compared with existing technologies, traditional target preparation processes often employ single-component or simply mixed raw material systems, failing to precisely control the particle size matching of multiphase materials. Existing sintering processes mostly utilize pressureless sintering, resulting in insufficient material density. This method achieves synergistic control of multi-component particle size through staged ball milling, combined with pressure-assisted sintering, effectively improving the grain boundary bonding state.

[0042] Through the above technical solution, the target material prepared in this application can form a dense thin film structure with uniform grain size after sputtering, reducing light scattering loss at grain boundaries. The synergistic effect of the multiphase material system reduces the surface reflectivity of the thin film, enabling the prepared display device to maintain clear image contrast even in strong light environments.

[0043] According to some embodiments of the present invention, the mass ratio of tungsten powder, yttrium oxide powder, and zinc oxide powder is 70-75:13-15:17-20.

[0044] Among them, tungsten powder refers to metallic tungsten powder used as the matrix material, specifically spherical particles prepared by reduction method, with its mass percentage controlled at 70-75% to maintain the conductivity and mechanical strength of the target material. Yttrium oxide powder refers to rare earth oxide powder used as a grain boundary stabilizer, specifically nanoscale powder synthesized by wet process, with its mass percentage controlled at 13-15% to optimize grain size distribution. Zinc oxide powder refers to transition metal oxide powder used as a sintering aid, specifically submicron-sized powder prepared by chemical precipitation method, with its mass percentage controlled at 17-20% to adjust the amount of liquid phase generated during sintering.

[0045] Specifically, the mass ratio of tungsten powder, yttrium oxide powder, and zinc oxide powder is precisely defined as 70–75:13–15:17–20. When the tungsten powder content is below 70%, the conductivity of the target material will significantly decrease; while exceeding 75% will lead to a decrease in the dispersion uniformity of yttrium oxide and zinc oxide. Maintaining the yttrium oxide content in the range of 13–15% can effectively inhibit the abnormal growth of tungsten grains without causing grain boundary embrittlement due to excessive introduction. Controlling the zinc oxide content in the range of 17–20% ensures the formation of an appropriate amount of liquid phase during sintering to promote densification, while avoiding component segregation caused by excessive liquid phase. The synergistic ratio of the three raw materials enables the mixed slurry to achieve a more uniform dispersion state during subsequent ball milling.

[0046] Compared with existing technologies, traditional target material preparation often employs proportional mixing or random proportioning, leading to component segregation and porosity defects within the sintered body. This solution limits the specific mass ratio range, enabling each component to form a stable three-phase structure during sintering. Yttrium oxide is uniformly distributed at tungsten grain boundaries to suppress grain coarsening, while zinc oxide forms a continuous second phase at the grain boundaries, collectively improving the uniformity of the target material's microstructure.

[0047] Through the above technical solution, this application effectively solves the problem of high film reflectivity caused by improper composition ratio of traditional target materials. During magnetron sputtering, the target material with this ratio can deposit a thin film structure with uniform grain size and clear grain boundaries, significantly reducing diffuse reflection of light inside the film layer, thereby improving the visibility of display devices in strong light environments.

[0048] According to some embodiments of the present invention, the particle size of the solid particles in the tungsten powder slurry is 0.3 to 0.5 micrometers.

[0049] Tungsten powder slurry refers to a suspension formed by mixing tungsten powder with a liquid medium. Specifically, it can be achieved by dispersing the tungsten powder using a ball milling process. The particle size can be adjusted by controlling the ball milling time and speed. The particle size of the solid particles refers to the average diameter of the tungsten powder particles in the slurry, which can be measured using a laser particle size analyzer. This particle size range is selected to promote close packing of particles during sintering and reduce porosity formation.

[0050] Specifically, during the preparation process, the particle size of the tungsten powder slurry is limited to the range of 0.3 to 0.5 micrometers. This size range ensures the slurry possesses appropriate fluidity and dispersibility, facilitating uniform mixing with other component slurries. During the sintering stage, smaller particles accelerate densification through surface diffusion, while the lower particle size limit prevents agglomeration caused by excessively fine particles, thus ensuring the uniformity of the target material's internal structure after sintering. Consequently, light scattering on the target surface is reduced, and reflectivity is lowered.

[0051] Compared to existing technologies, the particle size control of tungsten powder slurry in existing technologies is usually not clearly defined or adopts a wider particle size distribution, resulting in porosity or compositional segregation inside the target material after sintering. This solution optimizes the contact area between particles and the sintering kinetics by limiting a specific particle size range, which significantly improves the density of the target material and avoids interface defects caused by excessive particle size differences.

[0052] Through the above technical solution, this application can effectively control the uniformity of the target material's microstructure and reduce diffuse reflection of light on the material surface, thereby meeting the requirements of display devices for low-reflection optical performance. The setting of this particle size range further ensures that the target material forms a dense and uniformly composed thin film layer during magnetron sputtering, making it suitable for the preparation of reflective layers in high-precision display panels.

[0053] According to some embodiments of the present invention, the particle size of the solid particles in the tungsten powder slurry is any value among 0.3 micrometers, 0.35 micrometers, 0.4 micrometers, 0.45 micrometers and 0.5 micrometers, such as 0.4 micrometers, or any range formed by both, such as 0.35 micrometers to 0.4 micrometers.

[0054] According to some embodiments of the present invention, the particle size of the solid particles in the yttrium oxide slurry is 0.12 to 0.22 micrometers.

[0055] Yttrium oxide slurry refers to a suspension formed by mixing yttrium oxide powder with water. Specifically, it can be achieved by ball milling yttrium oxide powder and water in a specific ratio. The particle size refers to the diameter range of the powder particles after grinding, which can be controlled by adjusting the ball milling time, speed, and grinding media ratio. This particle size range is selected to balance the slurry's flowability and dispersion uniformity. When the particle size is less than 0.12 micrometers, the increased van der Waals forces between particles easily lead to agglomeration; when the particle size exceeds 0.22 micrometers, the slurry settling velocity increases, affecting mixing uniformity.

[0056] Specifically, during the preparation of the mixed slurry, the particle size of the yttrium oxide powder directly affects the subsequent sintering quality. By controlling the yttrium oxide powder particles within the range of 0.12–0.22 micrometers, the yttrium oxide component can be uniformly dispersed in the mixed slurry, avoiding localized component segregation. In the spray granulation process, particles within this size range have a suitable specific surface area, which is beneficial for forming granulated powder with good sphericity. During the sintering stage, uniformly dispersed yttrium oxide particles can form a stable interface with the tungsten matrix, promoting the densification process.

[0057] Compared to existing technologies, the particle size control of yttrium oxide slurry in traditional processes is usually not clearly defined, leading to uneven dispersion of the mixed slurry. This solution improves the continuity of the target material's microstructure by defining a specific particle size range, enabling the yttrium oxide component to form a uniformly distributed grain boundary phase during sintering.

[0058] Through the above technical solution, this application effectively solves the problem of uneven film sputtering caused by the agglomeration or sedimentation of yttrium oxide particles, so that the final target material can form a uniform thin film layer with low reflectivity during the magnetron sputtering process, which significantly reduces the scattering effect of light on the screen surface.

[0059] According to some embodiments of the present invention, the particle size of the solid particles in the yttrium oxide slurry is any value among 0.12 micrometers, 0.14 micrometers, 0.16 micrometers, 0.18 micrometers, 0.2 micrometers, and 0.22 micrometers, such as 0.16 micrometers, or any range formed by both, such as 0.16 micrometers to 0.2 micrometers.

[0060] According to some embodiments of the present invention, the particle size of the solid particles in the zinc oxide slurry is 0.12 to 0.22 micrometers.

[0061] The particle size of the solid particles in the zinc oxide slurry refers to the average size range of the solid particles in the slurry after ball milling. Specifically, it can be achieved by controlling the ball milling time, ball-to-particle ratio, and rotation speed parameters using a wet ball milling process. This particle size range is selected to match the particle sizes of the tungsten powder slurry and yttrium oxide slurry, thereby promoting the uniform dispersion of different component particles during the mixing stage.

[0062] Specifically, during the preparation of the mixed slurry, the particle size of the zinc oxide slurry is limited to the range of 0.12–0.22 micrometers, creating a gradient distribution with the 0.3–0.5 micrometer particles in the tungsten slurry and the 0.12–0.22 micrometer particles in the yttrium oxide slurry. In the second ball milling stage, particles of different sizes fill each other through mechanical force, reducing agglomeration. Ultimately, during sintering, a dense ceramic structure with uniformly distributed grain boundaries is formed, thereby reducing the number of light-scattering interfaces within the material.

[0063] Compared to existing technologies, the particle size of zinc oxide slurry in traditional methods is often not precisely controlled, potentially using either coarse or excessively fine particles, leading to uneven component distribution in the slurry. Coarse particles are prone to leaving pores after sintering, while excessively fine particles may cause abnormal grain growth due to excessively high surface energy; both increase the light reflection interface within the material. This solution, by limiting the size range of zinc oxide particles, avoids both insufficient densification caused by excessively coarse particles and sintering abnormalities caused by excessively fine particles, thereby optimizing the optical properties of the film.

[0064] Through the above technical solution, this application can reduce internal defects in the reflective layer formed by target sputtering, reduce the phenomenon of multiple reflections of light inside the film layer, and thus improve the display contrast and readability of OLED screen in strong light environment.

[0065] According to some embodiments of the present invention, the particle size of the solid particles in the zinc oxide slurry is any value among 0.12 micrometers, 0.14 micrometers, 0.16 micrometers, 0.18 micrometers, 0.2 micrometers, and 0.22 micrometers, such as 0.16 micrometers, or any range formed by both, such as 0.16 micrometers to 0.2 micrometers.

[0066] According to some embodiments of the present invention, the second ball milling time is 12h to 20h.

[0067] The second ball milling process involves mechanically grinding a mixture of tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry. This can be achieved using a planetary ball mill or a drum ball mill, with the grinding intensity controlled by adjusting the milling jar speed and the ball ratio. The purpose of this step is to ensure thorough dispersion of the different component particles and achieve uniform mixing at the microscale. The time range must balance mixing efficiency with the risk of excessive particle breakage. Too short a milling time may lead to uneven component distribution, affecting subsequent sintering and densification; too long a time may cause particle agglomeration or lattice defects, reducing the conductivity of the target material.

[0068] Specifically, in the preparation process, the mixed slurry is loaded into a ball mill jar and cemented carbide grinding balls are added, with the ball-to-material ratio controlled within a specific range. The ball mill operates at a constant speed, achieving particle refinement and uniform dispersion through the collision and shearing action between the grinding balls and the slurry. During this process, the ball milling time must consider the initial particle size distribution, slurry viscosity, and target particle size requirements. After 12 hours of ball milling, the interfacial bonding force between particles increases, and the component distribution tends to be more uniform; after 20 hours, the increased particle surface energy may lead to secondary agglomeration, therefore the upper limit of the time must be controlled within 20 hours.

[0069] Compared to existing technologies, conventional processes typically involve ball milling times for the mixed slurry that are either less than 10 hours or more than 24 hours. Shorter times are insufficient to eliminate component segregation, leading to microscopic compositional differences within the target material; excessively long times increase energy consumption and cause particle morphology degradation. This application solves the problem of balancing efficiency and quality in traditional processes by limiting the ball milling window to 12-20 hours, ensuring mixing uniformity while avoiding over-grinding.

[0070] Through the above technical solution, this application achieves sufficient dispersion and optimized interfacial bonding of the components in the mixed slurry, laying the foundation for the formation of a dense structure during subsequent sintering. The uniform microstructure helps to reduce the grain boundary resistance inside the target material, improve conductivity, and reduce the defect density during sputtering film formation, ultimately enabling the prepared film to exhibit more stable low-reflection characteristics in display devices.

[0071] According to some embodiments of the present invention, the second ball milling time is any value of 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, such as 15h, or a range of any two, such as 14h to 18h.

[0072] According to some embodiments of the present invention, the sintering includes a first-stage sintering and a second-stage sintering. The method of the first-stage sintering includes: heating to 850°C to 1050°C at a rate of 10°C / min to 20°C / min under normal pressure and holding at that temperature for 2 hours. The method of the second-stage sintering includes: increasing the pressure from normal pressure to 25MPa at a rate of 3MPa / min and holding at that pressure for 1 hour, heating to 150°C to 1580°C at a rate of 10°C / min to 15°C / min and holding at that temperature for 10 hours.

[0073] The first stage of sintering refers to the initial melting and bonding of powder particles under normal pressure through rapid heating. This can be achieved using a segmented temperature control program, controlling the heating rate and holding time to prevent abnormal grain growth caused by localized overheating. The second stage of sintering refers to the densification of particles under pressure through gradient heating and holding. This can be achieved using a hydraulic system in conjunction with a temperature sensor, where the synergistic effect of pressure and temperature eliminates internal porosity and forms uniform grain boundaries.

[0074] Specifically, a high heating rate is used in the atmospheric pressure stage to form a continuous network structure on the powder surface. Subsequently, in the pressurization stage, a pressure gradient is used to eliminate residual porosity. Finally, in the high-temperature holding pressure stage, the grains are oriented and densified. This process, by controlling the thermodynamic conditions in stages, enables the formation of a uniform microstructure inside the target material, thereby reducing light scattering and reflection after sputtering.

[0075] Compared to existing technologies, conventional sintering processes typically employ single temperature or pressure conditions, resulting in uneven grain size distribution or high residual porosity. This proposed solution, however, applies different combinations of pressure and temperature in stages. After initial densification at atmospheric pressure, high pressure and high temperature are used to eliminate microscopic defects, resulting in a more uniform and dense internal structure of the target material.

[0076] Through the above technical solution, this application can prepare a target material with clear grain boundaries and low porosity, and form a thin film layer with a smooth surface during sputtering, which effectively reduces the reflection intensity of light at the thin film interface, thereby improving the visibility of the display device in a strong light environment.

[0077] According to some embodiments of the present invention, the mold used in the preparation method is a planar square mold.

[0078] According to some embodiments of the present invention, finishing includes machining and surface polishing the target semi-finished product to obtain the target finished product.

[0079] The second aspect of the present invention provides a low-reflection tungsten-based ceramic target material, which is prepared by the method of the first aspect of the present invention.

[0080] This invention further proposes a preparation method for a low-reflection tungsten-based ceramic target material, comprising the following steps: Tungsten powder, yttrium oxide powder, and zinc oxide powder are sampled at a mass ratio of 68–75:12–15:16–20, and water is added to each powder for a first ball milling to obtain tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry; the tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry are mixed and then ball milled a second time to obtain a mixed slurry; the mixed slurry is spray-granulated to obtain powder, and the powder is injected into a hot-press sintering furnace for sintering to obtain a target material semi-finished product; the target material semi-finished product is then finely processed to obtain a low-reflection tungsten-based ceramic target material.

[0081] The mass ratio refers to the proportion of tungsten powder, yttrium oxide powder, and zinc oxide powder, specifically within the range of 68-75:12-15:16-20. This ratio balances the material's electrical conductivity and optical properties. The first ball milling process disperses the raw material powder in water through mechanical grinding, achieved using a ball mill to bring the solid particles to a preset particle size range. The second ball milling process further grinds the mixed slurry, typically by extending the milling time, promoting uniform distribution of different components. Spray granulation transforms the slurry into spherical particles, achieved using centrifugal atomization combined with hot air drying, improving powder flowability and bulk density. Hot pressing sintering densifies the powder through pressure and heat, achieved through staged heating and pressure holding, forming a high-density ceramic structure. Finishing refers to dimensional trimming of the sintered target material, achieved through mechanical cutting or polishing to ensure surface flatness.

[0082] Specifically, tungsten powder, yttrium oxide powder, and zinc oxide powder are mixed in a specific mass ratio and then subjected to two ball milling processes to achieve particle refinement and uniform dispersion. The spherical powder formed by spray granulation is injected into a hot-pressing sintering furnace, where a dense ceramic body is formed under staged heating and pressurization conditions. Finally, a target material with a smooth surface is obtained through fine machining. In the microstructure of this target material, yttrium oxide and zinc oxide are uniformly distributed in the tungsten matrix, forming a composite phase with low light reflection characteristics.

[0083] Compared to existing technologies, current reflective layer materials typically employ single metals or unoptimized composite ceramics, resulting in uneven composition distribution or insufficient sintering density, leading to multiple reflections of light at the film interface. This solution, however, utilizes a staged ball milling and hot-pressing sintering process to create a uniform microstructure within the target material, reducing light scattering interfaces and thus lowering reflectivity.

[0084] Through the above technical solution, the low-reflection tungsten-based ceramic target provided in this application can effectively reduce the surface reflection of OLED screens in strong light environments after magnetron sputtering film formation, improve display contrast and readability, and at the same time meet the conductivity requirements of the electrode layer.

[0085] According to some embodiments of the present invention, the low-reflection tungsten-based ceramic target has a relative density greater than 94% and a resistivity less than 6.03 × 10⁻⁶. -4 Ω·cm.

[0086] Relative density refers to the ratio of the material's actual density to its theoretical density. It can be achieved by controlling grain growth and porosity through hot-pressing sintering. Internal porosity can be effectively eliminated through pressure and temperature gradients in a two-stage sintering process. Resistivity refers to the material's ability to impede the passage of electric current. It can be achieved by controlling the composite ratio of the tungsten matrix with yttrium oxide and zinc oxide. The high conductivity of metallic tungsten and the uniform distribution of the oxide phase form a synergistic conductive network.

[0087] Specifically, during the sintering process, the first stage of atmospheric pressure heating initially binds the raw material particles together, while the second stage of pressurized heating promotes grain boundary diffusion and densification. The addition of yttrium oxide and zinc oxide not only modulates grain boundary properties but also forms nanoscale second phases in the tungsten matrix. These second phases prevent excessive grain growth while maintaining the continuity of conductive pathways. By precisely controlling the ball milling time and sintering parameters, a composite structure with high density and low resistivity is ultimately formed.

[0088] In some specific embodiments, the spray-granulated powder can be sintered under a nitrogen protective atmosphere, for example, by loading the powder with a graphite mold, and then removing the surface oxide layer by machining after sintering. The powder mixing stage can be achieved using a planetary ball mill to achieve nanoscale dispersion, for example, by setting a ball-to-powder ratio of 5:1 and using zirconia grinding balls.

[0089] Compared to existing technologies, traditional reflective layer targets often employ single metals or simple alloy systems, with relative densities generally below 90% and high resistivity. Conventional sintering processes struggle to achieve uniform dispersion of the oxide phase in tungsten-based materials, resulting in significant grain boundary resistance within the material. This solution utilizes a multiphase composite design and a gradient sintering process to improve material density while maintaining high conductivity.

[0090] Through the above technical solution, this application effectively reduces internal light scattering and interface reflection of the sputtered thin film on the target material, enabling the formed reflective layer to maintain screen contrast even under strong light conditions. The low porosity of the dense structure reduces the diffuse reflection path of incident light, while the optimized conductive network reduces the surface potential difference caused by charge accumulation, thereby synergistically improving screen visibility under extreme lighting conditions.

[0091] The third aspect of the present invention provides the application of the low-reflection tungsten-based ceramic target prepared by the preparation method of the first aspect of the present invention or the low-reflection tungsten-based ceramic target of the second aspect of the present invention in the preparation of display devices.

[0092] The target material is prepared by a specific method, and the film structure formed by its sputtering can reduce the reflection, refraction and diffuse reflection of light on the screen surface, thereby improving the display effect in strong light environment.

[0093] Among them, low-reflection tungsten-based ceramic targets refer to targets prepared by mixing tungsten powder, yttrium oxide powder and zinc oxide powder in a certain proportion and then ball milling and sintering. Specifically, a thin film layer can be formed on the surface of the substrate by magnetron sputtering, and the light reflectivity can be reduced by controlling the material composition and microstructure.

[0094] Display devices include, but are not limited to, OLED or LCD screens, whose reflective or encapsulation layers can suppress ambient light interference through thin film structures formed by sputtering targets.

[0095] Magnetron sputtering is a technique that uses electric and magnetic fields to control the deposition of target particles. Specifically, it can use high-energy particles in a vacuum environment to bombard the surface of the target material, causing material atoms to sputter and deposit on the substrate to form a dense thin film.

[0096] Specifically, this sputtering target is used in the reflective or encapsulation layer during display device fabrication. The thin film structure formed by sputtering reduces multiple reflections of light on the screen glass surface, thereby reducing interference from ambient light on the displayed content. The low reflectivity of the tungsten-based ceramic material in the target originates from the uniformly distributed yttrium oxide and zinc oxide phases in its microstructure. These second-phase particles weaken the reflection intensity of incident light through scattering and absorption. The dense structure formed by the sintering process further reduces the porosity inside the thin film, thus reducing diffuse reflection when light passes through the film.

[0097] Compared to existing technologies, current display devices often use single metal or oxide materials for their reflective layers. The optical properties of these materials make it difficult to balance conductivity and reflectivity. For example, traditional aluminum-based reflective layers, while exhibiting good conductivity, have excessively high reflectivity, leading to a decrease in screen contrast under strong light. This solution, however, utilizes a composite ceramic material system to regulate light reflection behavior through a multiphase structure while maintaining conductivity, thus resolving the contradiction between high reflectivity and display performance in existing technologies.

[0098] Through the above technical solution, this application can significantly reduce the intensity of reflected light on the screen surface under strong light conditions, so as to maintain high contrast and readability of the displayed content, while ensuring that the thin film layer has the necessary conductivity and mechanical strength, which is suitable for the manufacturing of display panels for portable electronic devices such as mobile phones and tablets.

[0099] To verify the effectiveness of the target material, the target density, resistivity, and reflectivity of the TCO thin film after coating were tested for the specific embodiments and comparative examples.

[0100] Density testing employed Archimedes' water displacement method; target resistivity was tested using the four-point probe method; sputtering coating testing was conducted on a cleaned glass substrate with a coating power of 150W and a gas environment of H2 / O2 mixed gas, resulting in a film thickness of 80mm; and film reflectivity was tested using a reflectivity meter after sputtering.

[0101] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0102] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0103] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0104] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0105] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0106] Example 1

[0107] A low-reflection tungsten-based ceramic target was prepared, comprising the following steps:

[0108] S1: Take 70 parts of W metal powder, 13 parts of Y2O3 powder and 17 parts of ZnO powder respectively, add deionized water and ball mill them to prepare a mixed slurry;

[0109] S2: Mix the W metal powder slurry, Y2O3, and ZnO slurry and ball mill for a second time for 15 hours;

[0110] S3: Spray granulation of the ball-milled slurry;

[0111] S4: The dried powder is injected into a hot press sintering furnace for sintering;

[0112] First stage: The target temperature for heating is 950℃, the heating rate is 20℃ / min, and the holding time for the first stage is 2 hours; no pressure is applied during the first stage of heating, and the pressure is maintained at normal.

[0113] Second stage: The target temperature for heating is 1560℃, the heating rate is 1015℃ / min, and the holding time is 10h; the pressure is increased from atmospheric pressure to 25MPa, the pressure loading rate is 3MPa / min, and the holding time is 1h.

[0114] S5: Machining and surface polishing of the target material semi-finished product to obtain the target material finished product.

[0115] S6: Test the target density, resistivity, and reflectivity of the film after sputtering.

[0116] Comparative Examples 1 and 2

[0117] A tungsten-based ceramic target was prepared. Comparative Examples 1 and 2 involved adding Y₂O₃ or ZnO to W powder in specific amounts, as shown in the table below. The rest of the process was the same as in the examples.

[0118] Comparative Example 3

[0119] A tungsten-based ceramic target was prepared, and the process is as follows:

[0120] S1: Take 70 parts of W metal powder, 13 parts of Y2O3 powder and 17 parts of ZnO powder respectively, add deionized water and ball mill them to prepare a mixed slurry;

[0121] S2: Mix the W metal powder slurry, Y2O3, and ZnO slurry and ball mill for a second time for 15 hours;

[0122] S3: Spray granulation of the ball-milled slurry;

[0123] S4: The dried powder is injected into a hot press sintering furnace for sintering;

[0124] Single-stage heating: The target temperature is 1560℃, the heating rate is 1015℃ / min, and the holding time is 10h; the pressure is increased from atmospheric pressure to 25MPa, the pressure loading rate is 3MPa / min, and the holding time is 1h.

[0125] S5: Machining and surface polishing of the target material semi-finished product to obtain the target material finished product.

[0126] S6: Test the target density, resistivity, and reflectivity of the film after sputtering.

[0127] The metal W powder, Y2O3 powder and ZnO powder of each embodiment and comparative example are shown below, and the test results of the target material and thin film are also shown in Table 1.

[0128] Table 1

[0129]

[0130]

[0131] As can be seen from Table 1:

[0132] Comparing Examples 1-5 with Comparative Examples 1-2, it can be seen that neither adding Y₂O₃ nor ZnO alone can achieve dense sintering in W metal powder, mainly because W has an extremely high melting point and cannot be fully densified at 1500–1580°C. However, the density increases significantly after adding both Y₂O₃ and ZnO, primarily because Y₂O₃ can interact with ZnO to form a Y-Zn binary ceramic structure. An equal amount of ZnO promotes sintering, improves powder dispersion, and reduces apparent porosity.

[0133] Comparative analysis of the target resistivity results shows that although Comparative Example 2 has the highest proportion of metal W, it does not show a significant positive increase in resistivity. This is mainly because the target sintering is not dense enough at this point, and the pores and gaseous structures in each part affect electron movement, resulting in even lower resistivity. Comparison of density shows a positive correlation between density and resistivity. Analysis of the thin film reflectivity data reveals that, similar to resistivity and density, even with a high content of metal W, reflectivity does not show a significant increase, which is consistent with the effects of composition and density.

[0134] Figure 1 The images show the microstructure of the material in Example 3. (a) shows the microstructure of the spray-granulated powder, and (b) shows the microstructure of the finished target material.

[0135] from Figure 1 As can be seen in (a) of the figure, after the three raw materials are individually ball-milled, mixed ball-milled, and spray-granulated, the overall shape is spherical with a particle size between 3 and 5 micrometers. The metallic luster in the left figure is W powder, which is embedded on the surface of the spherical particles. This is also the reason why W metal is difficult to sinter with Y2O3 and ZnO powder under normal pressure.

[0136] from Figure 1 As shown in (b), a Y-Zn ceramic phase exists in the target material after sintering, and the W metal powder remains granular with a particle size of about 2 micrometers. It is uniformly dispersed overall, but agglomerates exist in some areas. As analyzed above, W metal is the source of reflectivity enhancement, and the improved uniformity of its dispersion also has a positive impact on the high reflectivity of the sputtered film.

[0137] Figure 2 The low-reflection film prepared using the target material of this invention is based on the low-reflection principle within an OLED. Figure 2As can be seen, when incident light travels from the outside to the outer glass layer of the screen and reaches the reflective film, the light undergoes multiple refractions and reflections within the film. The refracted portion of the light enters the device's interior; the reflected portion, upon reaching the upper surface of the reflective film, undergoes further refraction and reflection. At this point, some light passes through the glass and exits the screen, while the rest returns to the film, undergoing even more refractions and reflections. Through these multiple refractions and reflections, the intensity of the light ultimately reflected from the screen is significantly lower than the incident light, resulting in a low-reflection effect.

[0138] The W-based ceramic target material prepared by this invention has a relative density of up to 98.9% and a resistivity of 5.63 × 10⁻⁶. -4 Its reflectivity of ~75% can be applied to OLED reflective materials, solving the problem of poor screen performance under strong light.

[0139] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a low-reflection tungsten-based ceramic target, characterized in that, Includes the following steps: S1: Take samples of tungsten powder, yttrium oxide powder, and zinc oxide powder at a mass ratio of 70~75:13~15:17~20, add water to each sample and ball mill them for the first time to obtain tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry; S2: The tungsten powder slurry, yttrium oxide powder slurry, and zinc oxide powder slurry are mixed and then subjected to a second ball milling to obtain a mixed slurry; S3: After spray granulation of the mixed slurry, powder is obtained, and the powder is injected into a hot pressing sintering furnace for sintering to obtain a target material semi-finished product; S4: The target material semi-finished product is finely processed to obtain the low-reflection tungsten-based ceramic target material; The particle size of the solid particles in the tungsten powder slurry is 0.3~0.5 micrometers; The particle size of the solid particles in the yttrium oxide slurry is 0.12~0.22 micrometers; The particle size of the solid particles in the zinc oxide slurry is 0.12~0.22 micrometers; The second ball milling time is 12h~20h; The sintering includes a first-stage sintering and a second-stage sintering. The first-stage sintering method includes: heating to 850℃~1050℃ at a rate of 10℃ / min~20℃ / min under normal pressure and holding at that temperature for 2 hours. The second-stage sintering method includes: increasing the pressure from normal pressure to 25MPa at a rate of 3MPa / min and holding at that pressure for 1 hour, then heating to 1500℃~1580℃ at a rate of 10℃ / min~15℃ / min and holding at that temperature for 10 hours.

2. A low-reflection tungsten-based ceramic target, characterized in that, It is prepared by the preparation method described in claim 1.

3. The low-reflection tungsten-based ceramic target according to claim 2, characterized in that, The low-reflection tungsten-based ceramic target has a relative density greater than 94% and a resistivity less than 6.03 × 10⁻⁶. -4 Ω·cm.

4. The application of the low-reflection tungsten-based ceramic target obtained by the preparation method according to claim 1 or the low-reflection tungsten-based ceramic target according to any one of claims 2 to 3 in the preparation of display devices.

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