Dustless pressing positioning equipment for liquid crystal display module offset sticking process

Abstract

The application discloses a dust-free pressing positioning equipment for a liquid crystal display module partial sticking process and belongs to the technical field of liquid crystal module processing. The dust-free pressing positioning equipment comprises a base layer, a gas equalizing layer, a liquid blocking and gas permeating layer and a sacrifice layer. The upper surface of the base layer is a precision ground plane, and the base layer is internally provided with a vacuum air duct. The gas equalizing layer is made of metal fiber sintered felt and is internally provided with a three-dimensional interconnected pore network. The liquid blocking and gas permeating layer is made of expanded polytetrafluoroethylene film and is detachably fixed to the upper surface of the gas equalizing layer. The sacrifice layer is made of a stainless steel porous plate and is stacked on the upper surface of the liquid blocking and gas permeating layer. The lower surface of the sacrifice layer is provided with a plurality of concave cavities, and a through hole is arranged above the concave cavities and communicates with the concave cavities. During the partial sticking process, the overflowed liquid optical adhesive flows into the concave cavities through the through hole and is solidified, and is blocked by the liquid blocking and gas permeating layer. The liquid blocking and gas permeating layer can be wiped or replaced, and after replacement, calibration is not required, and the reference precision remains unchanged. The application separates the plane reference maintenance, uniform adsorption and overflow glue isolation to different layers, and realizes dust-free management of the overflow glue.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal module processing technology, specifically a dust-free pressing and positioning device for the offset bonding process of liquid crystal display modules. Background Technology

[0002] The polarization bonding process for LCD modules is a high-precision process that involves bonding optical films such as polarizers to the surface of the LCD panel using optical adhesive. This process is carried out in a cleanroom and places extremely high demands on the flatness, uniformity of adsorption, and cleanliness of the positioning platform.

[0003] Currently, the industry commonly uses a high-flatness metal platform as a positioning reference. Several discrete vacuum adsorption holes are opened on the platform, and the LCD panel is adsorbed and fixed by negative pressure before being bonded. However, during the bonding process, optical adhesive overflows from the edge of the polarizer and flows onto the platform surface. This excess adhesive remains on the platform surface and gradually hardens and accumulates under repeated pressure during continuous production and environmental factors, forming irregular hard particles ranging from micrometers to millimeters in size. These particles can cause uneven stress on the subsequently adsorbed panel, leading to bonding bubbles, polarizer indentations, and even cracking of ultra-thin panels.

[0004] To remove these hardened adhesive residues, production must be interrupted, and operators must wipe them with solvents or scrape them with blades. This cleaning method has the following problems: blade scraping gradually damages the original precision flatness of the platform surface, causing it to gradually lose its flatness and shorten its precision lifespan; solvent residues on the platform surface after wiping may affect the uniformity of subsequent panel adsorption; and the cleaning operation itself requires machine shutdown, affecting production continuity.

[0005] To address the aforementioned issues, some solutions propose laying a flexible protective film on the metal platform, attempting to isolate adhesive residue by replacing the film layer. However, this solution has a fundamental flaw: under the negative pressure of vacuum adsorption, the flexible protective film surface is sucked into the discrete adsorption pores, forming localized depressions. This completely destroys the original precise flatness of the platform surface, rendering it incapable of serving as a positioning reference. If the adsorption negative pressure is reduced to avoid film surface depression, sufficient adsorption force cannot be provided to fix the panel, causing panel displacement during the bonding process, and the bonding accuracy cannot be guaranteed.

[0006] In addition, some solutions use a detachable rigid pad instead of a flexible membrane, with through holes machined into the pad surface to transfer vacuum. While this solution avoids membrane surface depression, the liquid adhesive can penetrate downwards along the through holes in the pad and solidify on the substrate surface, compromising the flatness of the substrate. Furthermore, the adhesive can cause blockages in the vacuum adsorption pores of the substrate, meaning that even replacing the pad cannot restore the original precision and adsorption performance of the substrate.

[0007] Therefore, it is of great significance to provide a dust-free pressing and positioning device that can stably maintain a precise planar reference in continuous production, effectively isolate overflow adhesive pollution, and not affect the uniformity of adsorption, so that pollution treatment no longer comes at the expense of platform accuracy or clean environment. Summary of the Invention

[0008] The purpose of this invention is to provide a dust-free pressing and positioning device for the offset bonding process of liquid crystal display modules. By integrating a base layer, a gas equalization layer, a liquid-blocking and breathable layer, and a sacrificial layer into the same device with a gradient microporous structure, the three functions of maintaining the planar reference, uniform adsorption and transfer, and isolation of overflow contamination are separated into different layers. Replacing the sacrificial layer or the liquid-blocking and breathable layer does not affect the reference accuracy of the lower layer. In continuous production, a precise planar reference is maintained while achieving dust-free management of overflow contamination, so that contamination treatment no longer comes at the expense of platform accuracy or a clean environment.

[0009] The objective of this invention is achieved through the following technical solution: A dust-free lamination and positioning device for the offset bonding process of liquid crystal display modules includes: The base layer has a precision-ground flat surface on its upper surface and a vacuum channel inside. The vacuum channel converges to an interface on the side or bottom of the base layer, and the interface is connected to the vacuum adsorption unit through a pipeline. The gas equalization layer, made of sintered metal fiber felt, is stacked on the upper surface of the base layer. The gas equalization layer has a three-dimensional interconnected pore network inside. The peripheral edges of the gas equalization layer are provided with a sealing structure. The liquid-blocking and gas-permeable layer is made of expanded polytetrafluoroethylene film and covers the upper surface of the gas equalization layer. The liquid-blocking and gas-permeable layer has a microporous structure. The sacrificial layer, made of a rigid porous material, is detachably stacked on the upper surface of the liquid-blocking and breathable layer. Its upper surface is used to support the liquid crystal panel. The sacrificial layer has through holes that penetrate its upper and lower surfaces. The lower surface of the sacrificial layer is provided with multiple concave cavities. The through holes are located above the concave cavities and communicate with the concave cavities. The pore diameter of the sacrificial layer is larger than the micropore diameter of the liquid-blocking and breathable layer. The vacuum channels of the base layer, the pore network of the gas equalization layer, the microporous structure of the liquid-blocking and gas-permeable layer, and the through holes of the sacrificial layer are sequentially connected to form an airflow path from the vacuum adsorption unit to the upper surface of the sacrificial layer.

[0010] Preferably, the gas equalization layer is fixed to the upper surface of the base layer by hot pressing or bonding, and the liquid-blocking and breathable layer is fixed to the upper surface of the gas equalization layer by a peripheral pressure frame, wherein the upper surface of the peripheral pressure frame is not higher than the upper surface of the liquid-blocking and breathable layer; a portion of the edge of the gas equalization layer is provided with a positioning baffle that protrudes upward and extends to the edge of the sacrificial layer.

[0011] Preferably, the sacrificial layer is made of a porous stainless steel plate with a thickness of 0.1 mm to 0.3 mm, and its surface and the inner wall of the through holes are treated with an oleophobic coating; the pore size of the sacrificial layer is 0.1 mm to 0.3 mm. The micropores of the liquid-blocking and gas-permeable layer have a pore size of 0.1 μm to 0.5 μm and a porosity greater than 85%. The thickness of the gas homogenization layer is 0.2 mm to 0.5 mm, and the porosity is 60% to 80%. The base layer is made of microporous ceramic or breathable steel, and its upper surface flatness is less than or equal to 5 μm.

[0012] Preferably, the lower surface of the sacrificial layer, excluding the concave cavity, has a diamond-like coating prepared using a low-temperature deposition process.

[0013] Preferably, the thickness of the diamond-like carbon coating does not exceed 5 μm; the deposition temperature is below 150°C; and the coefficient of friction of the diamond-like carbon coating is below 0.1.

[0014] Preferably, the metal fiber cross nodes of the gas equalization layer have a chemically plated nickel layer, which coats and bonds the cross fibers.

[0015] Preferably, the surface of the metal fiber further has a plasma nitriding layer, which covers the electroless nickel plating layer, and the thickness of the nitriding layer is 1 μm to 5 μm. Preferably, it also includes a dry gas bypass, one end of which is connected to a dry gas source and the other end is connected to the edge region of the gas homogenization layer. The dry gas bypass is opened when the vacuum adsorption unit is turned off.

[0016] Preferably, a waste gas adsorption module is provided below the base layer or on the upstream pipeline of the vacuum adsorption unit, and the waste gas adsorption module is filled with activated carbon or molecular sieve.

[0017] Preferably, the vacuum adsorption unit includes a vacuum pump, a control valve, and a vacuum gauge. The vacuum pump is connected to the interface of the base layer through a pipeline. The control valve is used to adjust the opening and closing of the negative pressure. The vacuum gauge is used to monitor the vacuum level in the pipeline.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention integrates a base layer, a gas equalization layer, a liquid-barrier and gas-permeable layer, and a sacrificial layer into a single device with a gradient microporous structure. This adapts to the continuous production requirements of precise positioning, uniform adsorption, and isolation of excess adhesive contamination in the LCD module bonding process. It improves upon the limitations of traditional platforms in terms of cleaning accuracy and the need for recalibration when replacing consumables. Specifically: The base layer provides a precise planar reference for the entire positioning platform. During use, it does not come into contact with excess adhesive or suffer from cleaning and scratching. Its flatness maintains the initial grinding accuracy, reducing the problem of the reference plane gradually being lost due to manual scraping and cleaning of adhesive residue with blades in traditional solutions.

[0019] A uniform gas distribution layer, made of sintered metal fiber felt, is fixedly stacked on the upper surface of the base layer and features a three-dimensional interconnected pore network. This layer evenly diffuses the negative pressure from the base layer across the entire plane, ensuring uniform adsorption force across the upper surface of the liquid-blocking and breathable layer, and consequently, the sacrificial layer. This reduces the problems of weak adsorption force in inter-pore areas and localized panel warping common in traditional discrete adsorption pore schemes. Simultaneously, the uniform gas distribution layer acts as a protective barrier for the base layer, preventing the precision-ground surface of the base layer from directly contacting the liquid-blocking and breathable layer and the sacrificial layer. This avoids accidental scratches or wear on the base layer surface during replacement of upper components, further ensuring long-term stability of the reference accuracy.

[0020] The liquid-blocking and breathable layer is fixedly placed on the upper surface of the gas equalization layer. Its micropores allow gas to pass through, maintaining the vacuum adsorption pathway. Liquid optical adhesive, due to its molecular cluster size being much larger than the micropore diameter, is trapped on the upper surface of the liquid-blocking and breathable layer, preventing further penetration into the gas equalization layer and the base layer. This reduces the problems of liquid adhesive seeping down through the through holes and clogging the base vacuum pores in traditional rigid pad solutions, and the inability to restore base accuracy and adsorption performance even after replacing the pad. Simultaneously, the liquid-blocking and breathable layer slows down the penetration of gaseous components volatilized from the optical adhesive, protecting the pore structure of the gas equalization layer and the base layer from long-term accumulation and blockage. The liquid-blocking and breathable layer itself is made of expanded polytetrafluoroethylene (ePTFE), which has low surface energy, resulting in weak adhesion of the cured adhesive on its surface. During routine production breaks, it can be directly wiped clean with a lint-free cloth. For long-term use with thick adhesive buildup, the surrounding pressure frame can be loosened to remove the liquid-blocking and breathable layer for cleaning or replacement, depending on the actual situation.

[0021] The lower surface of the sacrificial layer has multiple recessed cavities, with through holes located above and communicating with these cavities. During the bonding process, any liquid optical adhesive that overflows flows through the through holes into the recessed cavities under pressure and cures. The cured adhesive block is contained within the recessed cavity, not protruding from the lower surface of the sacrificial layer, thus preventing the adhesive block from forming a protrusion between the sacrificial layer and the liquid-resistant and breathable layer, which would affect the flatness of the bond. The liquid-resistant and breathable layer is made of expanded polytetrafluoroethylene (ePTFE) film, which has an oleophobic surface. A small amount of liquid adhesive that overflows from the recessed cavities and adheres to the upper surface of the liquid-resistant and breathable layer has weak adhesion after curing and can be wiped off during sacrificial layer replacements.

[0022] When excessive adhesive buildup on the surface of the sacrificial layer or blockage of the through-holes leads to a decrease in adsorption, the vacuum is turned off, and the sacrificial layer is lifted for cleaning or replacement. Because the upper surface of the sacrificial layer and the inner walls of the through-holes are treated with an oleophobic coating, the bond strength between the cured adhesive and the hole walls is low, and the cured adhesive in the concave cavity is carried away along with the sacrificial layer. After removing the sacrificial layer, if there is adhesive buildup on the surface of the liquid-blocking and breathable layer, it can be wiped clean or removed for cleaning and replacement; both can be handled separately. During the replacement process, the gas equalization layer and the base layer remain stationary, and the precise planar reference formed by the two remains unchanged. Therefore, no flatness calibration or alignment calibration is required after replacement, reducing the need for recalibration after each replacement as in traditional rigid pad solutions.

[0023] In summary, this invention assigns the three functions of maintaining the planar reference, uniform adsorption and transfer, and isolation of adhesive overflow contamination to different layers. Replacing the sacrificial layer or the liquid-blocking and breathable layer does not affect the precise planar reference formed by the gas equalization layer and the base layer. It can stably maintain the precise planar reference in continuous production, while realizing dust-free management of adhesive overflow contamination. This eliminates the need for contamination treatment at the expense of platform accuracy or clean environment, improves production continuity and product yield, and better meets the usage requirements of the LCD module bonding process. Attached Figure Description

[0024] Figure 1 : A schematic diagram of the structure of Embodiment 1 of the present invention viewed from the front; Figure 2 : Figure 1 Schematic diagram of the structure of the middle sacrificial layer from the bottom view; Figure 3 : Figure 1 A top-down structural diagram; In the diagram: 1-base layer, 2-gas equalization layer, 3-liquid barrier and gas permeable layer, 4-sacrificial layer, 5-concave cavity, 6-positioning baffle, 7-pipeline. Detailed Implementation

[0025] A dust-free lamination and positioning device for the offset bonding process of liquid crystal display modules, such as Figure 1-3 As shown, the system includes a base layer 1, a gas equalization layer 2, a liquid-blocking and gas-permeable layer 3, a sacrificial layer 4, a positioning baffle 6, pipelines 7, and a vacuum adsorption unit. The base layer 1 is installed on the equipment frame (this component is a conventional structure and is not shown in the figure). The bottom of the equipment frame is equipped with support legs (this component is a conventional structure and is not shown in the figure). The entire equipment is placed on the offset workstation in the cleanroom.

[0026] The upper surface of the base layer 1 is a precision-ground flat surface. The base layer 1 has vacuum channels inside, which converge at the interface on the side or bottom surface of the base layer 1. The interface is connected to the vacuum adsorption unit through the pipe 7. The base layer 1 is made of microporous ceramic or breathable steel, and its upper surface flatness is less than or equal to 5μm. Except for the interface, the periphery of the base layer 1 is closed to maintain the airtightness of the vacuum channels.

[0027] The gas equalization layer 2 is made of sintered metal fiber felt and is fixedly stacked on the upper surface of the base layer 1 by hot pressing or bonding. The gas equalization layer 2 has a three-dimensional interconnected pore network, a thickness of 0.2 mm to 0.5 mm, and a porosity of 60% to 80%. A sealing structure is provided at the peripheral edge of the gas equalization layer 2 to prevent lateral leakage of airflow from the edge, allowing negative pressure to concentrate inside the gas equalization layer 2 and be transmitted upwards. In practical implementation, the sealing structure can be: a ring of sealant is applied to the peripheral edge of the gas equalization layer 2, penetrating into the pores at the edge and sealing the pores after curing; or a metal or plastic sealing frame is fitted around the peripheral edge of the gas equalization layer 2, fixed to the peripheral surface of the gas equalization layer 2 by tight fitting or bonding, preventing lateral leakage of airflow from the edge. Alternatively, a dense metal sealing strip can be welded or brazed around the periphery of the gas uniform layer 2. The sealing strip covers all the pores at the edge of the gas uniform layer 2, as well as other conventional structures that can achieve sealing.

[0028] The liquid-blocking and breathable layer 3 is made of expanded polytetrafluoroethylene (ePTFE) membrane and covers the upper surface of the gas equalization layer 2. The liquid-blocking and breathable layer 3 has a microporous structure with pore sizes ranging from 0.1 μm to 0.5 μm and a porosity greater than 85%. The liquid-blocking and breathable layer 3 is fixed to the upper surface of the gas equalization layer 2 by a peripheral pressure frame (this component is a conventional structure and not shown in the figure). The upper surface of the peripheral pressure frame is not higher than the upper surface of the liquid-blocking and breathable layer 3, keeping the upper surface of the liquid-blocking and breathable layer 3 flat and not hindering the adhesion of the sacrificial layer 4. The liquid-blocking and breathable layer 3 is detachably connected to the gas equalization layer 2 by the peripheral pressure frame. During daily production breaks, if a small amount of adhesive accumulates on the upper surface of the liquid-blocking and breathable layer 3, it can be wiped clean directly with a lint-free cloth. With long-term use and a thicker layer of adhesive buildup, the peripheral pressure frame can be loosened to remove the liquid-blocking and breathable layer 3 separately for cleaning or replacement, depending on the actual situation. In practice, the peripheral pressure frame can be a one-piece rectangular metal frame, fixed to the edge of the gas equalization layer or the base layer with screws, or it can be a pressure strip divided into multiple sections, each section of which is locked with screws. It can also be a snap-on pressure frame, which uses elastic snaps to directly snap into the slots at the edge of the gas equalization layer or the base layer, or other conventional structures that can achieve the purpose.

[0029] The sacrificial layer 4 is made of a porous stainless steel plate and is detachably stacked on the upper surface of the liquid-blocking and breathable layer 3. The upper surface of the sacrificial layer 4 is used to support the liquid crystal panel. The thickness of the sacrificial layer 4 is 0.1 mm to 0.3 mm, and it has through-holes penetrating its upper and lower surfaces (this structure is conventional and not shown in the figure). The pore diameter of the sacrificial layer 4 is 0.1 mm to 0.3 mm. The upper surface of the sacrificial layer 4, the inner wall of the through-holes, and the inner wall of the recessed cavity 5 are treated with oleophobic coatings (such as existing oleophobic coatings such as perfluorooctyltrichlorosilane coatings applied by immersion or spraying). The oleophobic treatment reduces the bonding strength of the liquid optical adhesive after curing on the inner wall of the through-holes, making it easier for the cured adhesive to detach from the through-holes when replacing the sacrificial layer 4. The pore diameter of the sacrificial layer 4 is larger than the micropore diameter of the liquid-blocking and breathable layer 3. Figure 1-2 As shown, the lower surface of the sacrificial layer 4 is provided with multiple concave cavities 5. Through holes are provided above the concave cavities 5 and communicate with the concave cavities 5. The concave cavities 5 are grooves that are recessed upward into the lower surface of the sacrificial layer 4. Liquid optical adhesive flows into the concave cavities 5 after passing through the through holes and is cured. The cured adhesive block is contained inside the concave cavities 5 and does not exceed the plane of the lower surface of the sacrificial layer 4, so that there will be no gap between the lower surface of the sacrificial layer 4 and the upper surface of the liquid-resistant and breathable layer 3 due to the protrusion of the adhesive block.

[0030] like Figure 1-3 As shown, a portion of the edge of the gas equalization layer 2 is provided with a positioning baffle 6 that protrudes upward and extends to the edge of the sacrificial layer 4. The positioning baffle 6 is made of elastic material, and the inner surface of the positioning baffle 6 is an inclined surface that slopes outward from top to bottom. When the vacuum adsorption unit is turned on, the positioning baffle 6 limits the lateral displacement of the sacrificial layer 4. At the same time, the elastic material and the inclined surface design prevent the sacrificial layer 4 from being stuck when it is pressed downward under atmospheric pressure.

[0031] The vacuum channels of the base layer 1, the porous network of the gas equalization layer 2, the microporous structure of the liquid-blocking and gas-permeable layer 3, and the through-holes of the sacrificial layer 4 are sequentially connected to form an airflow path from the vacuum adsorption unit to the upper surface of the sacrificial layer 4. The vacuum adsorption unit (this structure is a conventional structure and is not shown in the figure) includes a vacuum pump, a control valve, and a vacuum gauge. The vacuum pump is connected to the interface of the base layer 1 through the pipeline 7. The control valve is used to adjust the opening and closing of the negative pressure, and the vacuum gauge is used to monitor the vacuum degree in the pipeline.

[0032] Working principle: First, the liquid-blocking and breathable layer 3 is fixed to the upper surface of the air-equalizing layer 2 by a peripheral pressure frame. The upper surface of the peripheral pressure frame is not higher than the upper surface of the liquid-blocking and breathable layer 3, so that the liquid-blocking and breathable layer 3 is flatly attached to the air-equalizing layer 2. The air-equalizing layer 2 is fixed to the upper surface of the base layer 1 by heat pressing or bonding. The sealing structure of the peripheral edge of the air-equalizing layer 2 ensures that the airflow does not leak from the edge laterally. The sacrificial layer 4 is stacked on the upper surface of the liquid-blocking and breathable layer 3, and the lateral position of the sacrificial layer 4 is restricted by the positioning baffle 6 at the edge of the air-equalizing layer 2. The inner slope of the positioning baffle 6 ensures that the sacrificial layer 4 is placed smoothly and will not be stuck when pressed downwards.

[0033] The vacuum adsorption unit is activated, and the control valve is opened. The vacuum pump extracts gas from the vacuum channels inside the base layer 1 through the interface between pipe 7 and base layer 1. The negative pressure enters the gas equalization layer 2 through the vacuum channels of base layer 1. The three-dimensional interconnected pore network inside the gas equalization layer 2 evenly diffuses the negative pressure in the planar direction, making the negative pressure evenly distributed on the entire surface of the gas equalization layer 2. The negative pressure continues to pass upward through the microporous structure of the liquid-resistant and breathable layer 3. Since the micropore diameter of the liquid-resistant and breathable layer 3 is 0.1μm to 0.5μm and the porosity is greater than 85%, the gas can pass through smoothly. At the same time, the liquid-resistant and breathable layer 3 plays a role in delaying the permeation of gaseous components volatilized from the optical adhesive, protecting the microporous structure of the gas equalization layer 2 and the base layer 1 from long-term accumulation and blockage by gaseous volatiles. The negative pressure then passes upward through the through hole of the sacrificial layer 4. When the airflow passes through the through hole, the air pressure difference is generated between the upper and lower surfaces of the sacrificial layer 4 due to the flow resistance of the through hole. The upper surface of the sacrificial layer 4 is at normal pressure and the lower surface is at negative pressure. The atmospheric pressure presses the sacrificial layer 4 downward evenly onto the upper surface of the liquid-blocking and air-permeable layer 3.

[0034] The liquid crystal panel is placed on the upper surface of the sacrificial layer 4 and fixed by negative pressure adsorption. Due to the lateral gas equalization effect of the gas equalization layer 2, the adsorption force on the liquid crystal panel is uniform throughout. Polarization bonding is then performed, with the polarizer bonded to the surface of the liquid crystal panel using optical adhesive. During bonding, the optical adhesive overflows from the edge of the polarizer and flows to the upper surface of the sacrificial layer 4. Under the pressure, the overflowing liquid optical adhesive passes through the through-holes of the sacrificial layer 4 and flows into the concave cavity 5 on the lower surface of the sacrificial layer 4. It is then blocked and cured within the cavity by the liquid-blocking and breathable layer 3, preventing further penetration to the gas equalization layer 2 and the base layer 1. After curing within the concave cavity 5, the cured adhesive block is contained within the concave cavity 5, does not protrude from the lower surface of the sacrificial layer 4, and does not form a protrusion between the sacrificial layer 4 and the liquid-blocking and breathable layer 3, thus not affecting the flatness of the bonding between the sacrificial layer 4 and the liquid-blocking and breathable layer 3.

[0035] During production, operators determine whether sacrificial layer 4 needs replacement based on the adhesion of adhesive on its surface and the decrease in vacuum adsorption force. When excessive adhesive buildup on the surface of sacrificial layer 4 affects panel flatness, or when blockage of through-holes leads to decreased adsorption force, the control valve of the vacuum adsorption unit is closed to release negative pressure, and sacrificial layer 4 is peeled off from liquid-blocking and breathable layer 3. Because the upper surface of sacrificial layer 4, the inner wall of the through-holes, and the inner wall of the concave cavity 5 are treated with oleophobic coating, the bond strength between the cured adhesive in the through-holes and the hole walls is low. The cured adhesive in the concave cavity 5 is carried away along with sacrificial layer 4, reducing residue on liquid-blocking and breathable layer 3. After replacing with a new sacrificial layer 4, the vacuum adsorption unit is restarted to resume production. Adhesive buildup on the surface of liquid-blocking and breathable layer 3 can be wiped clean with a lint-free cloth or removed for cleaning and replacement by loosening the surrounding pressure frame, as needed. During the replacement of the sacrificial layer 4 and the liquid-resistant and breathable layer 3, no flatness calibration or alignment calibration is performed on the gas equalization layer 2 and the base layer 1, and the precision plane reference formed by the gas equalization layer 2 and the base layer 1 remains unchanged.

[0036] Example 2 Based on Example 1, the lower surface of the sacrificial layer 4, excluding the concave cavity 5, has a diamond-like carbon (DLC) coating prepared using a low-temperature deposition process. The thickness of the DLC coating does not exceed 5 μm, the deposition temperature is below 150°C, and the coefficient of friction of the DLC coating is below 0.1. The DLC coating covers the planar area of ​​the lower surface of the sacrificial layer 4, and during replacement of the sacrificial layer 4, it slides in contact with the upper surface of the liquid-blocking and breathable layer 3, reducing the sliding friction between the sacrificial layer 4 and the liquid-blocking and breathable layer 3. This prevents frictional wear on the expanded polytetrafluoroethylene (ePTFE) membrane of the liquid-blocking and breathable layer 3 during repeated replacements, protecting the integrity of the liquid-blocking and breathable layer 3 and extending its service life. The use of a low-temperature deposition process to prepare the DLC coating, with a deposition temperature below 150°C, avoids thermal deformation of the stainless steel porous plate during coating preparation, maintaining the flatness of the sacrificial layer 4. The coating thickness does not exceed 5 μm, thus not affecting the breathability of the through holes or the adhesive-containing function of the concave cavity 5.

[0037] Furthermore, the metal fiber cross nodes of the gas equalization layer 2 have a chemically plated nickel layer. This nickel layer is deposited on the surface of the metal fibers using a chemical plating process before the metal fiber felt is sintered. After sintering, the nickel layer at the fiber cross nodes encapsulates and binds the two intersecting fibers together. The simultaneous deposition of the nickel layer on both the surface of the metal fibers and at the nodes enhances the connection strength of the nodes, improves their resistance to fatigue fracture due to airflow micro-vibrations, thereby extending the service life of the gas equalization layer 2 and ensuring the stability of the three-dimensional interconnected pore network during long-term use.

[0038] Furthermore, the surface of the metal fiber also has a plasma nitriding layer, which covers the electroless nickel plating layer, with a thickness of 1μm to 5μm. The plasma nitriding layer is formed on the surface of the metal fiber through a low-temperature plasma nitriding process after electroless nickel plating and before felt laying and sintering. During the long-term operation of the vacuum adsorption unit, trace amounts of water vapor in the cleanroom air continuously pass through the gas equalization layer 2 with the airflow. Water vapor molecules are physically adsorbed on the surface of the metal fiber and form an extremely thin adsorbed water film, keeping the fiber surface in a humid microenvironment for a long time. The plasma nitriding layer forms a dense, hard protective layer on the fiber surface and node surface, sealing the micropores on the surface of the electroless nickel plating layer, improving the hardness and corrosion resistance of the fiber surface, effectively blocking the contact between water molecules and the metal fiber matrix, and eliminating micro-defects on the surface of the electroless nickel plating layer, reducing the probability of fatigue crack initiation on the fiber surface. The thickness of the nitriding layer is 1μm to 5μm, which is negligible relative to the pore size inside the gas equalization layer 2, and will not block the pore network of the gas equalization layer 2, thus not affecting the air permeability. The plasma nitriding layer and the electroless nickel plating layer work together. The electroless nickel plating layer covers and combines the two fibers at the fiber cross node, strengthening the node's resistance to fatigue fracture. The plasma nitriding layer seals the micropores on the surface of the nickel plating layer, eliminates micro-defects on the fiber surface, and provides surface protection. Together, they ensure the long-term service reliability of the gas equalization layer 2 from both the node and surface levels.

[0039] Furthermore, a dry gas bypass is included. One end of the dry gas bypass is connected to the dry gas source, and the other end is connected to the edge region of the equalization layer 2. The dry gas bypass is activated when the vacuum adsorption unit is shut down. After long-term operation of the vacuum adsorption unit, the surface of the metal fibers inside the equalization layer 2 remains moist due to continuous water vapor adsorption. During the replacement of the sacrificial layer 4 or equipment shutdown for maintenance, the vacuum adsorption unit is shut down, and the dry gas bypass is activated. The dry gas enters the pore network inside the equalization layer 2 from the edge region, carrying the accumulated moisture upwards through the through-holes of the liquid-blocking and permeable layer 3 and the sacrificial layer 4, interrupting the long-term accumulation of moisture and keeping the inside of the equalization layer 2 dry. The dry gas bypass and the vacuum adsorption unit operate in a time-sharing manner, avoiding interference of the dry gas with the negative pressure of the vacuum adsorption. The dry gas bypass and the plasma nitriding layer work together for protection. The nitriding layer provides a surface corrosion-resistant barrier, and the dry gas bypass periodically removes accumulated moisture, jointly ensuring the long-term service reliability of the equalization layer 2.

[0040] Furthermore, a waste gas adsorption module is connected in series on the pipeline 7 between the interface of the base layer 1 and the vacuum pump. The waste gas adsorption module includes a shell and activated carbon or molecular sieve particles filled inside the shell. The shell is cylindrical or square, and both ends of the shell are connected to the pipeline 7. Filter screens are installed at the inlet and outlet of the shell to prevent activated carbon or molecular sieve particles from entering the pipeline 7. During the offset bonding process, the volatile organic components in the optical adhesive pass through the sacrificial layer 4, the liquid-blocking and gas-permeable layer 3, the gas equalization layer 2, and the base layer 1 in gaseous form, and enter the pipeline 7 with the airflow. When the airflow passes through the waste gas adsorption module, the activated carbon or molecular sieve physically adsorbs the volatile organic compounds, and the purified gas continues to be discharged through the vacuum pump. After the activated carbon or molecular sieve is saturated, the filler inside the shell can be replaced.

[0041] Note: The dimensions and thicknesses shown in the figure are for illustrative purposes only and do not represent the actual scale. They are only used to express the position and connection relationship of each component.

Claims

1. A dust-free pressing and positioning device for the offset bonding process of liquid crystal display modules, characterized in that, include: The base layer (1) has a precision-ground flat surface on its upper surface and a vacuum channel inside. The vacuum channel converges to the interface on the side or bottom of the base layer. The interface is connected to the vacuum adsorption unit through a pipeline. The gas equalization layer (2) is made of metal fiber sintered felt and is stacked on the upper surface of the base layer (1). The gas equalization layer (2) has a three-dimensional interconnected pore network inside. The peripheral edge of the gas equalization layer (2) is provided with a sealing structure. The liquid-blocking and breathable layer (3) is made of expanded polytetrafluoroethylene film and covers the upper surface of the gas equalization layer (2). The liquid-blocking and breathable layer (3) has a microporous structure. The sacrificial layer (4) is made of a rigid porous material and is detachably stacked on the upper surface of the liquid-blocking and breathable layer (3). Its upper surface is used to support the liquid crystal panel. The sacrificial layer (4) has through holes that penetrate its upper and lower surfaces. The lower surface of the sacrificial layer (4) is provided with a plurality of concave cavities (5). The through holes are located above the concave cavities (5) and communicate with the concave cavities (5). The pore size of the sacrificial layer (4) is larger than the micropore size of the liquid-blocking and breathable layer (3). The vacuum channels of the base layer (1), the pore network of the gas equalization layer (2), the microporous structure of the liquid-blocking and gas-permeable layer (3), and the through holes of the sacrificial layer (4) are connected in sequence to form an airflow path from the vacuum adsorption unit to the upper surface of the sacrificial layer (4).

2. The dust-free pressing and positioning equipment according to claim 1, characterized in that, The gas equalization layer (2) is fixed to the upper surface of the base layer (1) by hot pressing or bonding, and the liquid-blocking and breathable layer (3) is fixed to the upper surface of the gas equalization layer (2) by a peripheral pressure frame. The upper surface of the peripheral pressure frame is not higher than the upper surface of the liquid-blocking and breathable layer (3). A portion of the edge of the gas equalization layer (2) is provided with a positioning baffle (6) that protrudes upward and extends to the edge of the sacrificial layer (4).

3. The dust-free pressing and positioning equipment according to claim 1, characterized in that, The sacrificial layer (4) is made of stainless steel porous plate with a thickness of 0.1 mm to 0.3 mm, and its surface and the inner wall of the through hole are treated with oleophobic coating; the pore size of the sacrificial layer (4) is 0.1 mm to 0.3 mm. The micropore size of the liquid-blocking and gas-permeable layer (3) is 0.1 μm to 0.5 μm, and the porosity is greater than 85%. The thickness of the gas homogenization layer (2) is 0.2 mm to 0.5 mm, and the porosity is 60% to 80%. The base layer (1) is made of microporous ceramic or breathable steel, and its upper surface flatness is less than or equal to 5 μm.

4. The dust-free pressing and positioning equipment according to claim 1, characterized in that, The lower surface of the sacrificial layer (4), excluding the concave cavity (5), has a diamond-like coating prepared by a low-temperature deposition process.

5. The dust-free pressing and positioning equipment according to claim 4, characterized in that, The thickness of the diamond-like carbon coating does not exceed 5 μm; the deposition temperature is below 150°C; and the coefficient of friction of the diamond-like carbon coating is below 0.

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6. The dust-free pressing and positioning equipment according to claim 1, characterized in that, The metal fiber cross nodes of the gas equalization layer (2) have a chemically plated nickel layer that coats and binds the cross fibers.

7. The dust-free pressing and positioning equipment according to claim 6, characterized in that, The surface of the metal fiber also has a plasma nitriding layer, which covers the electroless nickel plating layer and has a thickness of 1 μm to 5 μm.

8. The dust-free pressing and positioning equipment according to claim 1, characterized in that, It also includes a dry gas bypass, one end of which is connected to a dry gas source and the other end is connected to the edge region of the gas equalization layer (2). The dry gas bypass is opened when the vacuum adsorption unit is closed.

9. The dust-free pressing and positioning equipment according to claim 1, characterized in that, A waste gas adsorption module is provided below the base layer (1) or on the upstream pipeline of the vacuum adsorption unit, and the waste gas adsorption module is filled with activated carbon or molecular sieve.

10. The dust-free pressing and positioning device according to claim 1, characterized in that, The vacuum adsorption unit includes a vacuum pump, a control valve, and a vacuum gauge. The vacuum pump is connected to the interface of the base layer through a pipeline (7). The control valve is used to adjust the opening and closing of the negative pressure. The vacuum gauge is used to monitor the vacuum level in the pipeline.

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