Preparation process of cover plate direct writing grid lines

Abstract

The invention discloses a preparation process of a cover plate direct writing grid line. The preparation process comprises the following steps: S1, arranging a composite embedded line composed of a core layer and a peelable outer layer on the surface of a cover plate base material; s2, carrying out calibration and pattern compensation on the position of the pre-embedded line by adopting a laser positioning system; s3, depositing a metal conductive layer; s4, removing the outer layer of the pre-embedded wire in a thermal decomposition mode to separate the core layer from the metal layer; s5, laser finishing and forming; s6, annealing treatment is conducted on the grid lines, and transparent passivation layers are deposited on the surfaces of the grid lines; through the steps of pre-embedded line structure compounding, laser positioning calibration, metal deposition and selective removal, laser finishing, post-treatment and the like, high-precision, high-efficiency, low-cost and environment-friendly grid line preparation is realized; the problems of complex flow, high material waste, serious environmental pollution and insufficient silk-screen printing precision of the traditional photoetching etching process are effectively solved.

Description

Technical Field

[0001] This invention relates to the technical field of display device manufacturing, specifically to a process for preparing cover glass direct-write grid lines. Background Technology

[0002] With the widespread application of touch screens in consumer electronics, automotive displays, and industrial control, the market has placed higher demands on the performance of touch screens, especially towards high resolution, low power consumption, flexibility, and low-cost manufacturing. As one of the core components of a touch screen, the performance of the conductive metal mesh pattern on its surface directly determines the sensitivity of the touch sensor and the visual effect of the display module.

[0003] Currently, traditional processes for fabricating grid lines on touchscreen cover plates mainly rely on photolithography, etching, or screen printing. These methods have the following drawbacks: they involve multiple pattern transfer and chemical processing steps, resulting in long production cycles and high equipment investment and maintenance costs; during etching, over 90% of precious metals are dissolved and discarded from the substrate, leading to extremely low material utilization; the entire process requires large amounts of developing solutions, etching solutions, and stripping solutions, generating numerous difficult-to-treat chemical wastes and imposing a heavy burden on the environment; and due to factors such as screen tension, latex thickness, and paste rheology, the edges of printed lines are prone to jaggedness, failing to meet the requirements of modern high-resolution display devices for finer and more concealed grid lines. Summary of the Invention

[0004] The purpose of this invention is to provide a fabrication process for direct-write mesh lines on a cover plate, which aims to solve the problems of complex process, high material waste, serious environmental pollution and insufficient screen printing accuracy of traditional photolithography etching processes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a process for fabricating cover plate direct-write grid lines, the process comprising the following steps: S1: A composite embedded line consisting of a core layer and a peelable outer layer is set on the surface of the cover plate substrate, arranged according to a preset grid pattern. The core layer is a rigid support material and the outer layer is a thermally decomposable material. S2: A laser positioning system is used to calibrate the position of the pre-embedded line and compensate for the pattern. S3: Deposit a conductive metal layer on the surface of the cover plate substrate to cover the embedded wire and its surrounding area; S4: Remove the outer layer of the pre-embedded wire through thermal decomposition to separate the core layer from the metal layer; S5: After removing the pre-embedded wire, the edge of the metal wire is micro-processed using laser trimming technology to form a neat cut edge and grid pattern; S6: Anneal the grid lines and deposit a transparent passivation layer on the grid line surface.

[0006] Preferably, the core layer of the composite pre-embedded wire is polyimide, the outer layer is polylactic acid, and the outer layer thickness is 0.5–5 μm.

[0007] Preferably, the laser positioning system uses a visual recognition and CCD positioning module to calibrate the position of the pre-embedded line in real time and compensate for substrate deformation and pattern deviation.

[0008] Preferably, the conductive metal layer is made of copper, silver, or aluminum and is deposited by magnetron sputtering, with the substrate rotating during the deposition process to achieve uniform coverage.

[0009] Preferably, the laser trimming process uses an ultraviolet laser, and the scanning path is performed along the original position of the pre-embedded line.

[0010] Preferably, the annealing treatment is carried out under a nitrogen protective atmosphere at a temperature of 180–250°C for 20–40 min.

[0011] Preferably, the transparent passivation layer is SiO2, deposited by plasma chemical vapor deposition, and has a thickness of 20–100 nm.

[0012] Preferably, the cover plate substrate is a flexible transparent polyester, and is pre-tensioned and surface activated before the metal layer is deposited.

[0013] Preferably, before depositing the metal layer, a metallic pattern layer is provided in the areas on both sides of the pre-embedded line to guide the metal to be preferentially deposited in the pre-embedded line area.

[0014] Preferably, the metallic pattern layer is a self-assembled monolayer, and the pattern width is wider than the diameter of the embedded line.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention removes the composite pre-embedded wire through thermal decomposition. The metal conductive layer is precisely removed only in the area in contact with the pre-embedded wire, while the metal layer in other areas of the substrate is retained, directly forming a grid pattern. This avoids the problem of more than 90% of precious metals being dissolved and discarded in traditional etching processes, greatly improving the utilization rate of metal materials. At the same time, it uses low-cost metals to replace silver, further reducing the cost of raw materials.

[0016] 2. The entire process of this invention does not require the use of traditional chemical reagents such as developing solutions, etching solutions, or stripping solutions. The outer layer of the pre-embedded line is removed through thermal decomposition and vaporization, generating only small gas molecules. There is no discharge of difficult-to-treat chemical waste liquid, which fundamentally reduces the burden on the environment and meets the requirements of green manufacturing. The direct-write graphic method avoids multiple graphic transfers and complex chemical processing steps. The process is compact and efficient. The laser positioning and calibration, deposition and removal are integrated into one design, reducing production links, shortening processing time, and improving production efficiency.

[0017] 3. This invention uses a laser positioning system to compensate for substrate deformation errors in real time, ensuring that the grid pattern is highly consistent with the design. The subsequent ultraviolet laser trimming process removes edge burrs and residues, forming neat and smooth metal line cut edges. The line width is precisely controlled, eliminating the jaggedness problem of traditional screen printing, and meeting the requirements of high-resolution displays for finer and more concealed grid lines.

[0018] 4. This invention employs magnetron sputtering for metal deposition to ensure a dense and uniform film; post-treatment annealing, under nitrogen protection, repairs lattice defects, reduces resistivity, and improves conductivity; a transparent passivation layer is deposited to protect the grid lines from oxidation and corrosion, enhancing long-term stability and adhesion; substrate pre-tensioning treatment offsets heat treatment deformation, and surface activation treatment improves metal adhesion, making the process applicable to materials such as flexible transparent polyester, meeting the application requirements of flexible displays and touch screens; in addition, self-assembled monolayers are set on both sides of the pre-embedded lines to further optimize the edge steepness and conductive continuity of the metal deposition. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the composite pre-embedded wire of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure for arranging the metal wires according to the present invention.

[0021] Figure 3 This is a schematic diagram of the structure for removing the outer layer of the pre-embedded wire in this invention through thermal decomposition. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a technical solution: An embodiment of this invention provides a process for fabricating cover plate direct-write grid lines, the process comprising the following steps: S1: Installation of composite pre-embedded wire The manufacturing process provided in this embodiment of the invention also includes a composite pre-embedded line disposed on the surface of the cover plate substrate. The composite pre-embedded line includes a core layer and a peelable outer layer. The core layer is made of polyimide, and its function is to provide rigid support for the entire pre-embedded line, ensuring that it maintains the preset grid shape in subsequent processes and preventing deformation due to substrate treatment or deposition stress. Figure 1 As shown.

[0024] The outer layer is polylactic acid with a thickness of 0.5–5 μm. As a typical thermally decomposable material, its function is to create conditions for the precise stripping of the metal layer by thermally decomposing and vaporizing in subsequent processes. By adopting this composite structure, the embedded wire provides a stable template during the deposition stage, and at the same time, it can achieve clean and thorough separation through the selective decomposition of the outer layer during the removal stage.

[0025] S2: Laser Positioning and Pattern Calibration The embodiments of the present invention also include using a laser positioning system to calibrate the position of the pre-embedded line. The laser positioning system uses a visual recognition and CCD charge-coupled device positioning module to capture the actual position image of the pre-embedded line on the substrate through a CCD camera, compare it with a preset digital pattern, calculate the position deviation, and then drive the laser to perform real-time compensation on the scanning path of the deposition area based on the deviation data. The function of this technical feature is to actively offset the pattern distortion caused by the deformation of the flexible substrate or the laying error, and ensure that the final metal mesh is highly consistent with the design drawings, laying the foundation for achieving high-precision line width control.

[0026] S3: Deposition of the metallic conductive layer The embodiments of the present invention also include depositing a metal conductive layer on the surface of a substrate. The metal conductive layer is copper, silver or aluminum. Copper is preferred as the deposited metal conductive layer. Copper has excellent conductivity, has a cost that is much lower than that of silver, and its thin film properties are highly compatible with subsequent laser finishing and annealing processes.

[0027] Magnetron sputtering deposition works by bombarding a metal target with ions in a vacuum environment. This sputtering causes the target atoms to be sputtered and deposited onto the substrate surface, forming a dense and uniform thin film. During deposition, the substrate rotates to ensure that metal atoms uniformly cover the embedded lines and the surrounding substrate from all angles, avoiding deposition dead zones or uneven thickness. This ensures the consistency of conductivity in the subsequently formed mesh lines. Figure 2 As shown.

[0028] S4: Thermal decomposition removal of the outer layer of the pre-embedded wire This invention also includes removing the outer layer of the pre-embedded wire through thermal decomposition, separating the core layer from the metal layer. The substrate with completed metal deposition is placed in a controlled heat treatment environment. When the temperature reaches the thermal decomposition threshold of polylactic acid (PLA), the outer PLA layer rapidly decomposes into small gaseous molecules, such as lactic acid monomers and oligomers, which then volatilize. This process causes the metal layer originally attached to the outer layer of the pre-embedded wire to separate from the core layer and detach due to loss of support. Precise removal of the metal layer is achieved only in the pre-embedded wire area, while retaining the metal layer in other areas of the substrate, thereby directly forming a mesh pattern. This improves the utilization rate of metal materials and fundamentally solves the problem of serious material waste in traditional etching processes. Figure 3 As shown.

[0029] S5: Laser finishing and shaping The embodiments of the present invention also include micro-processing the edges of the metal wires using a laser trimming process after removing the pre-embedded wires, forming neat cut edges and grid patterns. The laser trimming process uses an ultraviolet laser, and its working principle is to use the extremely high energy density and extremely small heat-affected zone of the ultraviolet laser beam to perform ultra-fine processing on the metal.

[0030] The laser scanning path strictly follows the original position left after the thermal decomposition of the pre-embedded line. Its function is to remove edge burrs, residues, or transition areas that may be generated during the metal deposition and pre-embedded line removal process, thereby forming a neat and smooth metal line cut edge. This step directly determines the final line width and edge quality of the grid line, ensuring high precision and consistency of the graphics and meeting the requirement of more concealed grid lines for high-resolution displays.

[0031] S6: Post-processing and performance enhancement The embodiments of the present invention also include annealing the grid lines and depositing a transparent passivation layer on their surface. The annealing is carried out under a nitrogen protective atmosphere at a temperature of 180–250°C for 20–40 minutes. Under nitrogen protection, heating allows the metal lattice atoms to gain energy for rearrangement and migration, thereby repairing lattice defects, increasing grain size, significantly reducing the resistivity of the grid lines, improving their conductivity, and enhancing the adhesion between the metal layer and the substrate.

[0032] The transparent passivation layer is SiO2, deposited by plasma chemical vapor deposition, with a thickness of 20–100 nm. Plasma-activated reactive gases, such as silane and nitrous oxide, are used to grow a dense SiO2 film on the surface of the grid lines at low temperature. This protects the metal grid lines from corrosion by moisture and oxygen in the environment, prevents oxidation, and improves their long-term reliability and stability. At the same time, the SiO2 layer has excellent light transmittance and will not affect the overall transparency of the cover plate.

[0033] In this embodiment of the invention, the cover plate substrate is a flexible transparent polyester, and it undergoes pre-tensioning and surface activation treatment before depositing the metal layer. The pre-tensioning treatment is to give the flexible substrate a reverse prestress during the deposition process to counteract the shrinkage and deformation that may be caused by subsequent heat treatment. The surface activation treatment is to remove organic contaminants from the substrate surface and increase its surface energy, thereby enhancing the adhesion between the metal layer and the substrate.

[0034] In addition, before depositing the metal layer, a metallic pattern layer is set on both sides of the pre-embedded line. The metallic pattern layer is a self-assembled monolayer with a pattern width slightly wider than the diameter of the pre-embedded line. One end of the self-assembled monolayer is firmly bonded to the substrate by chemical bonds, while the other end has metal affinity, which can significantly reduce the nucleation energy barrier of metal atoms in this area. This guides metal atoms to preferentially and more densely deposit in and around the pre-embedded line area during the sputtering deposition process, thereby further optimizing the edge steepness and conductivity continuity of the grid lines and achieving higher quality patterning.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for fabricating cover plate direct-write grid lines, characterized in that: The preparation process includes the following steps: S1: A composite embedded line consisting of a core layer and a peelable outer layer is set on the surface of the cover plate substrate, arranged according to a preset grid pattern. The core layer is a rigid support material and the outer layer is a thermally decomposable material. S2: A laser positioning system is used to calibrate the position of the pre-embedded line and compensate for the pattern. S3: Deposit a conductive metal layer on the surface of the cover plate substrate to cover the embedded wire and its surrounding area; S4: Remove the outer layer of the pre-embedded wire through thermal decomposition to separate the core layer from the metal layer; S5: After removing the pre-embedded wire, the edge of the metal wire is micro-processed using laser trimming technology to form a neat cut edge and grid pattern; S6: Anneal the grid lines and deposit a transparent passivation layer on the grid line surface.

2. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The core layer of the composite pre-embedded wire is polyimide, and the outer layer is polylactic acid, with an outer layer thickness of 0.5–5 μm.

3. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The laser positioning system uses a visual recognition and CCD positioning module to calibrate the position of the pre-embedded line in real time, compensating for substrate deformation and pattern deviation.

4. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The conductive metal layer is made of copper, silver, or aluminum and is deposited by magnetron sputtering. During the deposition process, the substrate is kept rotating to achieve uniform coverage.

5. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The laser trimming process uses ultraviolet laser, and the scanning path follows the original position of the pre-embedded line.

6. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The annealing process is carried out under a nitrogen protective atmosphere at a temperature of 180–250°C for 20–40 minutes.

7. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The transparent passivation layer is SiO2, deposited by plasma chemical vapor deposition, and has a thickness of 20–100 nm.

8. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: The cover plate substrate is a flexible transparent polyester, and it undergoes pre-tensioning and surface activation treatment before the metal layer is deposited.

9. The fabrication process of a cover plate direct-write grid line according to claim 1, characterized in that: Before depositing the metal layer, a metallic pattern layer is set in the area on both sides of the pre-embedded line to guide the metal to be deposited preferentially in the area of ​​the pre-embedded line.

10. The fabrication process of a cover plate direct-write grid line according to claim 9, characterized in that: The metallic patterned layer is a self-assembled monolayer, and the pattern width is wider than the diameter of the embedded line.

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