LCM liquid crystal panel and backlight module bonding process

Abstract

The present application belongs to the technical field of liquid crystal display panel bonding, in particular to a LCM liquid crystal panel and backlight module bonding process, which comprises the following steps: S1, completing optical stack assembly of the backlight module, and using a reactive gas source to perform low-temperature plasma modification pretreatment on the light emitting surface of the backlight module; S2, preparing a double-layer heterogeneous adhesive layer on the backlight light emitting surface: first, coating high-modulus UV curing adhesive on the edge non-display area of the backlight light emitting surface, and forming a closed sealing adhesive blocking frame after semi-curing treatment; by preparing a low-modulus center buffer adhesive layer on the backlight light emitting surface, and cooperating with the gradual pressing process from the center to the four sides, the adhesive layer is pre-soaked and filled in the gap between the optical microstructure such as the prism sheet, and the bonding pressure is uniformly transmitted through the adhesive layer, solving the problem that in the traditional bonding process, the pressure directly acts on the optical microstructure, which is easy to cause the microstructure to be pressed and deformed, resulting in the decrease of module brightness uniformity and the bright and dark spot defects.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal display panel bonding technology, specifically a bonding process between an LCM liquid crystal panel and a backlight module. Background Technology

[0002] Liquid crystal display (LCM) modules are the core display and interaction carriers of electronic terminal devices, widely covering diverse application scenarios such as consumer electronics, automotive displays, industrial control, and medical terminals. The bonding and assembly of the LCD panel and backlight module is the core process in LCM manufacturing. The technical level of the bonding process directly determines the module's optical display effect, structural reliability, environmental tolerance, and mass production yield, making it a key factor affecting the overall performance and manufacturing cost of LCM products. Currently, the mainstream bonding processes in the industry can be divided into two main routes: frame bonding with an air gap and full bonding without an air gap, respectively adapting to the manufacturing needs of display products of different sizes and positioning.

[0003] The frame-mount process uses double-sided adhesive strips on the edges to bond and fix the backlight module to the LCD panel, leaving an air gap in the middle. It has the advantages of simple process, low material cost and strong module maintainability. It is widely used in large-size TVs, low-end industrial control displays and other scenarios where the requirements for optical performance are not high. However, the air layer will cause interface light reflection loss, resulting in low light transmittance and contrast of the module, poor dust and moisture resistance, and defects such as dust ingress and light leakage at the edges.

[0004] However, in actual mass production and application, existing bonding technologies still have several technical pain points that are difficult to address in a coordinated manner: First, during the bonding pressurization process, the pressure directly acts on the optical microstructures such as the prisms on the backlight light-emitting surface, which can easily cause pressure damage and deformation of the microstructures, leading to defects such as decreased brightness uniformity and bright / dark spots in the module, thus limiting the improvement of product yield; Second, the backlight optical film has a low surface energy, resulting in insufficient adhesion between the adhesive layer and the film interface. Under complex environments such as high and low temperature cycling and damp heat shock, reliability failures such as adhesive layer desorption and warping are prone to occur, making it difficult to meet the performance requirements of demanding application scenarios such as automotive and industrial control; Third, liquid adhesives... The bonding process is prone to edge glue overflow, which can corrode the backlight FPC circuit and film edges. Solid adhesive bonding is also prone to leaving micro-bubbles, requiring an additional high-pressure defoaming process. This not only lengthens the process flow and reduces production efficiency, but the high-pressure environment also further increases the risk of prism sheet damage. Fourth, existing technology improvements are mostly single-point optimizations, which cannot simultaneously solve the multiple problems mentioned above, such as damage, glue overflow, bubbles, and insufficient reliability. Moreover, the backlight module assembly and bonding processes are disconnected from each other. The adhesive layer structure and bonding process are not adapted and designed from the backlight end, making it difficult to achieve a synergistic improvement in optical performance, production yield, structural reliability, and manufacturing efficiency.

[0005] Therefore, the present invention provides a bonding process for an LCM liquid crystal panel and a backlight module. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a bonding process for an LCM liquid crystal panel and a backlight module, the bonding process comprising the following steps: S1. Complete the optical stacking assembly of the backlight module, and use a reactive gas source to perform low-temperature plasma modification pretreatment on the light-emitting surface of the backlight module. S2. Pre-fabricate a double-layer heterogeneous adhesive layer on the backlight emitting surface: First, apply a high-modulus UV-curable adhesive to the non-display area at the edge of the backlight emitting surface, and form a closed sealing frame after semi-curing; then apply a low-modulus liquid optical adhesive to the effective display area enclosed by the sealing frame to form a central buffer adhesive layer that adapts to the optical microstructure of the backlight emitting surface. S3. The backlight module with the pre-made heterogeneous adhesive layer and the LCD panel are placed together in a vacuum environment. After precise visual alignment, rollers are used to gradually press them from the center of the bonding area to the four sides to complete the pre-bonding. S4. Adhesive layer curing is completed using a partitioned gradient curing process: First, the edge sealing frame is completely cured by ultraviolet light irradiation to achieve relative positioning and edge sealing between the backlight module and the LCD panel; then, the central buffer adhesive layer is cross-linked and cured using a stepped heating curing process, and after curing, the adhesive layer is slowly cooled to release internal stress. S5. Perform post-processing and performance testing on the laminated modules.

[0008] Preferably, in the low-temperature plasma modification pretreatment in S1, a mixture of inert gas and oxygen is used as the reaction gas source. After treatment, a micro-nano-scale rough anchoring structure is formed on the surface of the optical film on the backlight output surface, while eliminating static electricity on the film surface.

[0009] Preferably, in S2, the sealing adhesive frame is continuously closed along the edge of the backlight emitting surface, and a safe distance is left between the inner side of the adhesive frame and the edge of the effective display area; the sealing adhesive frame has shape-fixing strength after semi-curing treatment, and its elastic modulus after complete curing is higher than that of the central buffer adhesive layer after curing.

[0010] Preferably, the sealing adhesive frame and the central buffer adhesive layer are bonded together at adjacent interfaces to form an integral adhesive layer structure. The interfacial adhesion of the two adhesive layers is matched, and there is no risk of delamination or peeling after curing.

[0011] Preferably, in S2, the height of the adhesive surface of the central buffer adhesive layer is lower than the height of the top surface of the sealing adhesive frame; the central buffer adhesive layer has low modulus and high flow wettability before curing, and can spontaneously wet and fill the gaps in the optical microstructure of the backlight emitting surface; after curing, the refractive index matches the refractive index of the optical film of the backlight emitting surface.

[0012] Preferably, in S3, the vacuum environment maintains a stable high vacuum level; the visual precision alignment uses the alignment marks on the backlight module and the LCD panel as a reference to achieve precise alignment in the horizontal, vertical and angular directions; during the roller progressive pressing process, the adhesive layer spreads evenly from the center to the surrounding area as the pressing process progresses, and the gas between the interfaces is discharged simultaneously.

[0013] Preferably, in step S4, the curing of the edge sealing frame uses an ultraviolet LED light source, which exposes only the edge frame area in a directional manner. After exposure, the sealing frame is completely cross-linked and cured, forming a rigid support frame and a sealing barrier, which restricts the outward flow of the central buffer adhesive layer.

[0014] Preferably, the stepped temperature curing process of the central buffer adhesive layer in S4 is divided into a preliminary cross-linking stage and a deep curing stage. During the curing process, the temperature is gradually increased so that the adhesive layer slowly completes the cross-linking reaction. After the curing is completed, the curing stress inside the adhesive layer is released by gradually cooling down to avoid stress concentration that could cause the adhesive layer to warp or desorb.

[0015] Preferably, the progressive pressing process of S3 is coordinated with the flow and wettability of the central buffer adhesive layer, and the gas between the interfaces is discharged simultaneously during the pressing process, and the entire bonding process does not include a high-pressure defoaming step.

[0016] Preferably, the post-processing in S5 includes module edge cleaning and appearance inspection, and the performance testing includes optical performance testing and structural reliability testing.

[0017] The beneficial effects of this invention are as follows: 1. The LCM liquid crystal panel and backlight module bonding process described in this invention pre-fabricates a low-modulus central buffer adhesive layer on the backlight light-emitting surface, and combines it with a progressive pressing process from the center to the four sides. This allows the adhesive layer to pre-wet and fill the gaps in optical microstructures such as prisms, and the bonding pressure is uniformly transmitted through the adhesive layer. This solves the problems in traditional bonding processes where pressure is directly applied to optical microstructures, easily causing pressure damage and deformation of microstructures, resulting in decreased brightness uniformity and poor brightness / dark spot performance of the module.

[0018] 2. The LCM liquid crystal panel and backlight module bonding process described in this invention involves performing low-temperature plasma modification pretreatment on the backlight light-emitting surface to form a micro-nano-level rough anchoring structure and active groups on the film surface. Combined with a step-heating curing and slow cooling to release internal stress process, the interfacial adhesion between the adhesive layer and the optical film is improved, and the internal stress of the adhesive layer during curing is reduced. This solves the problems of insufficient interfacial adhesion between the adhesive layer and the film in traditional processes, the easy occurrence of adhesive layer desorption and warping under complex environments such as high and low temperature cycling, and the inability of the module reliability to meet the requirements of harsh scenarios.

[0019] 3. The LCM liquid crystal panel and backlight module bonding process described in this invention, by prefabricating a high-modulus closed sealing adhesive frame at the edge of the backlight light-emitting surface, structurally restricts the outward flow and overflow of the central adhesive layer. Combined with the synergistic effect of progressive pressing under vacuum and self-venting of the adhesive layer, residual bubbles at the interface can be eliminated without an additional high-pressure defoaming process. This solves the problems of traditional liquid adhesive bonding, which is prone to edge overflow and corrosion of circuits; solid adhesive bonding, which is prone to residual micro-bubbles requiring an additional high-pressure defoaming process; and long process flow, and high-pressure environment, which can aggravate prism sheet damage.

[0020] 4. The LCM liquid crystal panel and backlight module bonding process described in this invention integrates the adhesive layer preparation process into the backlight module assembly process. It adopts a heterogeneous adhesive layer structure of "high modulus edge baffle frame + low modulus center buffer adhesive" and an integrated process design of partitioned gradient curing. This achieves a deep fit between the backlight optical structure and the bonding process, solving the problems of existing technologies that can only carry out single-point optimization, the backlight assembly and bonding processes are separated, and it is difficult to simultaneously take into account optical performance, production yield, structural reliability and manufacturing efficiency, making it difficult to achieve multi-dimensional performance synergy improvement. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 This is the overall flow chart of the LCM bonding process in this invention; Figure 2 This is a flowchart of the pretreatment and heterogeneous adhesive layer prefabrication process in this invention; Figure 3 This is a flowchart of the vacuum alignment and progressive pressing process in this invention; Figure 4 This is a flowchart of the partitioned gradient curing process in this invention; Figure 5 This is a flowchart illustrating the anti-pressure damage and self-venting function of the heterogeneous adhesive layer in this invention; Figure 6 This is a flowchart of the finished product post-processing and performance testing process in this invention. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0024] like Figures 1 to 6 As shown in the embodiment of the present invention, a bonding process for an LCM liquid crystal panel and a backlight module includes the following steps: S1. Complete the optical stacking assembly of the backlight module, and use a reactive gas source to perform low-temperature plasma modification pretreatment on the light-emitting surface of the backlight module. The optical stacking assembly of the aforementioned backlight module completes the assembly of each functional film and the backplate in the order of optical hierarchy. During the assembly process, a high-precision positioning fixture is used to constrain the relative position of each film to avoid abnormal light output caused by film displacement. The low-temperature plasma modification pretreatment is carried out in a clean environment. By bombarding the surface of the optical film of the backlight light-emitting surface with plasma, the film surface is micro-etched and active groups are introduced without damaging the optical structure and performance of the film, thereby improving the bonding and adhesion between the subsequent adhesive layer and the film surface. S2. Pre-fabricate a double-layer heterogeneous adhesive layer on the backlight emitting surface: First, apply a high-modulus UV-curable adhesive to the non-display area at the edge of the backlight emitting surface, and form a closed sealing frame after semi-curing; then apply a low-modulus liquid optical adhesive to the effective display area enclosed by the sealing frame to form a central buffer adhesive layer that adapts to the optical microstructure of the backlight emitting surface. The prefabrication process of the aforementioned double-layer heterogeneous adhesive is integrated at the end of the backlight module assembly line. The adhesive layer is prefabricated directly after the backlight module has been assembled and tested, without the need to transfer it to the bonding line for adhesive layer preparation. The high-modulus UV-curable adhesive is continuously applied along the edge non-display area using screen printing or dispensing. After application, it is semi-cured by low-energy ultraviolet light irradiation, giving the adhesive frame a fixed shape and initial support strength, preventing deformation and collapse when the central adhesive layer is applied later. The low-modulus liquid optical adhesive is uniformly applied to fill the area enclosed by the sealed adhesive frame, spreading naturally due to its own fluidity, while simultaneously wetting the microstructure gaps of the prism sheet on the backlight light-emitting surface, avoiding microstructure damage caused by hard contact. S3. The backlight module with the pre-made heterogeneous adhesive layer and the LCD panel are placed together in a vacuum environment. After precise visual alignment, rollers are used to gradually press them from the center of the bonding area to the four sides to complete the pre-bonding. The aforementioned vacuum environment is provided by the vacuum bonding chamber. The pre-bonding process is carried out entirely under vacuum conditions to prevent air from the environment from being trapped inside the adhesive layer and forming air bubbles. Visual alignment uses a CCD visual recognition system to capture alignment mark images on the backlight module and the LCD panel respectively. The relative positions of the two are adjusted by a motion platform to achieve precise alignment in the planar direction and rotation angle. Roller progressive pressing uses flexible rollers to start contacting the bonding surface from the center and gradually roll it radially towards the edge. Under pressure, the adhesive layer is evenly spread from the center to the surrounding area, and at the same time, the gas between the adhesive layer and the panel and backlight is discharged from the edge, eliminating the need for subsequent additional venting processes. S4. Adhesive layer curing is completed using a partitioned gradient curing process: First, the edge sealing frame is completely cured by ultraviolet light irradiation to achieve relative positioning and edge sealing between the backlight module and the LCD panel; then, the central buffer adhesive layer is cross-linked and cured using a stepped heating curing process, and after curing, the adhesive layer is slowly cooled to release internal stress. The aforementioned zoned gradient curing process employs differentiated curing methods and sequences for the two adhesive layers with different properties. The edge sealing frame uses ultraviolet light curing, which is fast and can reach high modulus strength in a short time, quickly locking the relative position of the backlight and the panel to prevent displacement during the subsequent curing of the central adhesive layer. The central buffer adhesive layer uses thermosetting, controlling the rate of crosslinking reaction through step-by-step temperature increase to avoid stress concentration caused by rapid curing. After curing, the adhesive layer shrinks gradually by slow cooling, releasing the internal stress generated during curing and avoiding problems such as adhesive layer warping, desorption, and panel deformation under pressure caused by stress concentration. S5. Perform post-processing and performance testing on the laminated modules; The above post-processing and performance testing procedures are carried out in a normal temperature and clean environment. Post-processing is used to clean up any trace residual impurities that may be generated during the bonding process to ensure that the module has a clean appearance. Performance testing is used to screen out defective products with appearance defects or substandard optical performance to ensure the quality consistency of the modules leaving the factory.

[0025] like Figures 1 to 6 As shown, the low-temperature plasma modification pretreatment in S1 above uses a mixture of inert gas and oxygen as the reaction gas source. After treatment, a micro-nano-scale rough anchoring structure is formed on the surface of the optical film on the backlight output surface, while eliminating static electricity on the film surface. The aforementioned sealing frame is continuously installed around the perimeter of the backlight-emitting surface, forming a closed ring structure without breaks, ensuring uniform sealing performance and support strength at the edges. A safety gap is reserved between the inner side of the frame and the edge of the effective display area to prevent the frame from obstructing the effective display area, while also providing buffer space for the spreading of the central adhesive layer, preventing it from overflowing during the pressing process. After semi-curing, the sealing frame is self-supporting, maintaining its preset cross-sectional shape and height without flow deformation. After complete curing, it forms a high-hardness rigid frame, providing structural support for the entire module and buffering external impacts. It also acts as a sealing barrier to prevent moisture and dust from intruding from the edges, improving the module's environmental reliability. Its elastic modulus is higher than that of the central adhesive layer, forming a "rigid edge, flexible inner" stress-buffering structure. External stress is absorbed by the high-modulus frame at the edges, while the low-modulus adhesive layer at the center absorbs minor deformations, protecting the optical microstructure and panel.

[0026] like Figures 1 to 6 As shown, the sealing baffle frame in S2 is continuously closed along the edge of the backlight emitting surface, and a safe distance is left between the inner side of the baffle frame and the edge of the effective display area; the sealing baffle frame has shape strength after semi-curing treatment, and its elastic modulus is higher than that of the central buffer adhesive layer after curing after complete curing. The aforementioned sealing frame is continuously installed around the perimeter of the backlight-emitting surface, forming a closed ring structure without breaks, ensuring uniform sealing performance and support strength at the edges. A safety gap is reserved between the inner side of the frame and the edge of the effective display area to prevent the frame from obstructing the effective display area, while also providing buffer space for the spreading of the central adhesive layer, preventing it from overflowing during the pressing process. After semi-curing, the sealing frame is self-supporting, maintaining its preset cross-sectional shape and height without flow deformation. After complete curing, it forms a high-hardness rigid frame, providing structural support for the entire module and buffering external impacts. It also acts as a sealing barrier to prevent moisture and dust from intruding from the edges, improving the module's environmental reliability. Its elastic modulus is higher than that of the central adhesive layer, forming a "rigid edge, flexible inner" stress-buffering structure. External stress is absorbed by the high-modulus frame at the edges, while the low-modulus adhesive layer at the center absorbs minor deformations, protecting the optical microstructure and panel.

[0027] like Figures 1 to 6 As shown, the sealing and sealing frame and the central buffer adhesive layer are combined at the adjacent interface to form an integral adhesive layer structure. The interfacial adhesion of the two adhesive layers is matched, and there is no risk of delamination or peeling after curing. The aforementioned sealing and sealing frame and the central buffer adhesive layer form a tightly bonded whole at adjacent contact interfaces through molecular diffusion and chemical bonding, without any obvious delamination interface. The materials of the two adhesive layers are designed for compatibility, ensuring that the interfacial adhesion between them is no less than the adhesion between any adhesive layer and its corresponding substrate, preventing the interface between the two adhesive layers from cracking and falling off first under temperature change cycles or external forces. The overall adhesive layer structure ensures that stress is uniformly transmitted within the adhesive layer, avoiding local stress concentration and improving the overall structural reliability of the adhesive layer.

[0028] like Figures 1 to 6 As shown, the height of the adhesive surface of the central buffer adhesive layer in S2 is lower than the height of the top surface of the sealing adhesive frame; the central buffer adhesive layer has low modulus and high flow wettability before curing, and can spontaneously wet and fill the gaps in the optical microstructure of the backlight emitting surface. After curing, the refractive index matches the refractive index of the optical film of the backlight emitting surface. The adhesive surface height of the aforementioned central buffer adhesive layer is lower than the top surface of the sealing frame, providing space for the adhesive layer during the pressing process and preventing it from overflowing the frame area under pressure, thus structurally eliminating adhesive overflow defects. The low modulus characteristics before curing give the adhesive layer good deformation ability and fluidity, allowing it to flow fully under the slight pressure of bonding and pressing, wetting into the micron-level microstructure gaps of the backlight prism sheet, encapsulating the microstructure of the prism sheet inside the adhesive layer, and preventing the bonding pressure from directly acting on the top of the microstructure, causing pressure damage or deformation. After curing, the refractive index of the adhesive layer matches the refractive index of the optical film, eliminating the air interface between the adhesive layer and the film, reducing light loss caused by interface reflection, improving the overall light transmittance and contrast of the module, and eliminating edge light leakage problems caused by total internal reflection at the interface.

[0029] like Figures 1 to 6 As shown, the vacuum environment in S3 maintains a stable high vacuum level; the above-mentioned visual precision alignment uses the alignment marks on the backlight module and the LCD panel as a reference to achieve precise alignment in the horizontal, vertical and angular directions; during the above-mentioned roller progressive pressing process, the adhesive layer spreads evenly from the center to the surrounding area as the pressing process progresses, and the gas between the interfaces is discharged simultaneously. The aforementioned vacuum environment maintains a stable high vacuum state throughout the pressing process, preventing external air from entering the bonding cavity and ensuring that air is not trapped inside the adhesive layer to form bubbles. Alignment marks are pre-made on the edges of the backlight module's backplate and the LCD panel's glass substrate. These are dedicated alignment marks for non-display areas and will not affect the display effect. The visual alignment system can simultaneously identify two or more sets of alignment marks. After calculating the positional deviation through an algorithm, it drives a high-precision motion platform to compensate and adjust, ensuring that the positional deviation and rotation angle deviation in the X and Y axes are controlled within the allowable range. The roller progressive pressing method ensures that the adhesive layer spreads in an orderly manner. The spreading direction from the center to the edge can completely drive the gas between the interfaces to the edge and expel it, preventing the retention of closed bubbles inside the adhesive layer. Therefore, a subsequent high-pressure defoaming process is not required.

[0030] like Figures 1 to 6 As shown, the curing of the edge sealing frame in S4 above uses an ultraviolet LED light source, which only exposes the edge frame area in a directional manner. After exposure, the sealing frame is completely cross-linked and cured, forming a rigid support frame and sealing barrier, which restricts the outward flow of the central buffer adhesive layer. The irradiation range of the aforementioned ultraviolet LED linear light source precisely corresponds to the position of the edge sealing frame, irradiating only the edge frame area and avoiding irradiation of the central liquid optical adhesive, thus preventing premature curing of the central adhesive layer and its impact on performance. Using a linear light source allows for scanning exposure to cure the entire frame, with uniform and controllable exposure energy, ensuring consistent curing levels across the frame. The fully cured sealing frame possesses high structural strength, precisely locking the relative positions of the backlight module and the LCD panel, preventing relative displacement during the subsequent curing of the central adhesive layer. Simultaneously, the formed sealing barrier confines the central buffer adhesive layer within the effective display area, preventing flow and overflow during curing, while also blocking external moisture and dust from entering the bonding interface from the edges.

[0031] like Figures 1 to 6 As shown, the stepped temperature curing process of the central buffer adhesive layer in S4 is divided into a preliminary cross-linking stage and a deep curing stage. During the curing process, the temperature is gradually increased so that the adhesive layer slowly completes the cross-linking reaction. After the curing is completed, the curing stress inside the adhesive layer is released by gradually cooling down to avoid stress concentration that could cause the adhesive layer to warp or desorb. The initial cross-linking stage described above is carried out at a lower temperature, allowing the adhesive molecules to slowly undergo a cross-linking reaction, forming a preliminary three-dimensional network structure. The adhesive layer then possesses preliminary shape-stabilizing strength and will not flow. The deep curing stage is carried out at a higher temperature, allowing the cross-linking reaction of the adhesive layer to proceed fully, achieving the final mechanical and optical properties. The stepped heating method controls the rate of the cross-linking reaction, avoiding rapid heating that could lead to violent reactions in the adhesive layer and the generation of a large amount of internal stress. The gradual cooling process after curing allows the thermal shrinkage of the adhesive layer to proceed smoothly. Combined with the slow stress relaxation of the adhesive layer, this gradually releases the internal stress accumulated during the curing process, preventing stress concentration that could cause desorption between the adhesive layer and the backlight / panel interface, or warping and deformation of the adhesive layer itself. It also prevents uneven display caused by internal stress acting on the LCD panel.

[0032] like Figures 1 to 6 As shown, the progressive pressing process of S3 above is coordinated with the flow and wettability of the central buffer adhesive layer to simultaneously expel the gas between the interfaces during the pressing process. The entire bonding process does not include a high-pressure defoaming step. The pressing speed of the aforementioned progressive pressing is adapted to the flow characteristics of the central buffer adhesive layer, and the pressing speed is matched with the spreading speed of the adhesive layer, ensuring that the adhesive layer is always spread evenly during the pressing process and preventing air entrainment caused by untimely spreading of the adhesive layer. The synergistic effect of the vacuum environment, the progressive pressing from the center to the four sides, and the high fluidity of the adhesive layer itself can completely remove all the gas between the adhesive layer and the backlight and panel interfaces during the pre-lamination process. No micron-sized or larger air bubbles will remain inside the adhesive layer. Therefore, the entire lamination process does not require a high-pressure autoclave defoaming step, which can shorten the process flow, improve production efficiency, and avoid problems such as prism damage and panel deformation caused by excessive pressure during high-pressure defoaming.

[0033] like Figures 1 to 6 As shown, the post-processing in S5 includes module edge cleaning and appearance inspection, and the performance testing includes optical performance testing and structural reliability testing. The module edge cleaning process involves using a lint-free cloth and cleaning solvent to wipe away any trace amounts of adhesive residue and dust that may be present on the module edges, ensuring a clean appearance. Visual inspection is performed manually or using AOI (Automated Optical Inspection) equipment to check for defects such as foreign objects, bubbles, and scratches on the bonding surface. Optical performance testing includes core optical parameter tests such as transmittance, brightness, brightness uniformity, and contrast to verify whether the optical effect after bonding meets design requirements. Structural reliability testing includes reliability tests such as peel strength testing, high and low temperature cycling testing, and impact and vibration testing to verify the bonding reliability of the adhesive layer and the module's environmental tolerance, ensuring that the module will not experience failures such as delamination or warping during use.

[0034] Example 1: Lamination of 10.1-inch automotive display LCM module Application scenario: In-vehicle central control display screen, side-lit backlight module, requiring high reliability over a wide temperature range, no risk of adhesive overflow and corrosion, and excellent optical performance; Specific implementation steps: S1. Complete the optical stacking assembly of the 10.1-inch side-lit backlight module, and assemble the reflector, light guide plate, lower diffuser, lower prism sheet, upper prism sheet, and upper diffuser sheet in sequence. Fix the relative positions of each film with a positioning fixture. Use a mixture of argon and oxygen as the reaction gas source to perform low-temperature plasma modification pretreatment on the backlight light-emitting surface. After treatment, a micro-nano-scale rough anchoring structure is formed on the film surface, and the static electricity on the film surface is eliminated at the same time. S2. Pre-fabricate a double-layer heterogeneous adhesive layer on the backlight emitting surface: Apply a high-modulus acrylic UV-curable adhesive to the non-display area at the edge using screen printing, and then perform a low-energy UV semi-curing treatment to form a continuous closed sealing adhesive frame; then uniformly apply a low-modulus modified siloxane liquid optical adhesive to the effective display area enclosed by the sealing adhesive frame to form a central buffer adhesive layer. The adhesive surface naturally spreads and wets the microstructure gaps of the prism sheet, and the height of the adhesive surface is lower than the top surface of the sealing adhesive frame. S3. The backlight module with the pre-formed heterogeneous adhesive layer and the LCD panel are sent into the vacuum bonding cavity together to maintain a stable high vacuum environment. The alignment marks on the edges of the two are identified by the CCD vision system, and the motion platform is adjusted to complete the precise alignment in the horizontal, vertical and angular directions. Flexible rollers are used to roll from the center of the bonding area to the four sides to spread the adhesive layer evenly and expel the interface gas at the same time to complete the pre-bonding. S4. Adopting a zoned gradient curing process: Using ultraviolet LED light sources to directionally expose the edge sealing frame, so that the frame is fully cross-linked and cured, locking the relative position of the backlight and the panel and forming an edge sealing barrier; then the module is sent into a constant temperature oven to perform step-by-step temperature-curing of the central buffer adhesive layer. Initial cross-linking is completed at a low temperature, and then the temperature is raised to the curing temperature for deep curing. After curing, the temperature is gradually lowered to room temperature to slowly release the internal stress of the adhesive layer. S5. Remove the module, clean the edges and perform an appearance inspection, then conduct optical performance tests and structural reliability tests in sequence, and select qualified products.

[0035] Example 2: Lamination of 27-inch Industrial-Grade Display LCM Module Application scenarios: Industrial control displays, direct-lit backlight modules, requiring large-size high bonding yield, no bubble residue, and good impact resistance; Specific implementation steps: S1. Complete the optical stacking assembly of the 27-inch direct-lit backlight module, and assemble the reflector, LED light board, diffuser plate, lower diffuser, prism sheet, and upper diffuser in sequence. Fix each optical component with positioning posts and adhesive backing. Use a mixture of argon and oxygen as the reaction gas source to perform low-temperature plasma modification pretreatment on the backlight light-emitting surface to improve the adhesion of the film surface and eliminate static electricity. S2. Pre-fabricate a double-layer heterogeneous adhesive layer on the backlight emitting surface: Apply high-modulus UV-curable adhesive along the edge of the non-display area using a high-precision dispensing method, and semi-cur and shape it using low-energy ultraviolet light to form a closed and sealed adhesive frame; then uniformly apply low-modulus liquid optical adhesive in the effective display area enclosed by the adhesive frame using a slit coating method to form a central buffer adhesive layer. The adhesive layer fully wets the microstructure of the film surface, and the height of the adhesive surface is lower than the top surface of the adhesive frame. S3. The backlight module and the LCD panel are sent into a large-size vacuum bonding cavity to maintain a high vacuum environment; the four corner alignment marks are identified by multiple CCD vision systems to complete high-precision alignment; multi-segment flexible rollers are used to gradually press from the center to the four sides to make the adhesive layer spread evenly and simultaneously expel the interface gas to complete the pre-bonding. S4. Gradient curing in zones: A scanning ultraviolet LED light source is used to expose and cure the entire sealing frame, so that the frame is completely cross-linked to form a rigid support frame. Then the module is sent into a stepped temperature change oven to perform stepped heating curing and slow cooling stress relief treatment on the central buffer adhesive layer to complete the curing of the overall adhesive layer. S5. Perform edge cleaning, full appearance inspection, and optical and reliability testing on the module to obtain the finished module.

[0036] Example 3: Lamination of 12.3-inch MiniLED Backlight LCM Module Application scenario: MiniLED display screen for vehicle instrument panel, with zoned backlight structure, requiring low bonding stress, no LED chip damage, and strong interface adhesion; Specific implementation steps: S1. Complete the assembly of the 12.3-inch MiniLED backlight module, assembling the optical structure such as the driver backplate, MiniLED beads, quantum dot film, diffuser sheet, and prism sheet; use low-power argon-oxygen mixed plasma to perform mild modification pretreatment on the backlight light-emitting surface, improving the adhesion of the film surface and eliminating static electricity without damaging the MiniLED optical structure. S2. Pre-fabricated heterogeneous adhesive layer: High modulus UV curable adhesive is screen-printed in the non-display area at the edge, and semi-cured to form a sealed adhesive frame; Low modulus high toughness liquid optical adhesive is coated in the effective display area as a central buffer adhesive layer. The adhesive layer has excellent stress buffering ability, and the adhesive surface height is lower than the top surface of the adhesive frame to avoid adhesive overflow during the pressing process and corrosion of the LED and circuit. S3. In a vacuum environment, the backlight and panel are aligned with high precision through a CCD vision system. Low-pressure flexible rollers are used to press the backlight from the center to the four sides. The pressure is evenly transmitted by the fluidity of the adhesive layer to avoid excessive local pressure that could damage the MiniLED beads. At the same time, the interface gas is discharged to complete the pre-bonding. S4. Gradient curing in zones: First, the edge adhesive frame is completely cured and positioned by ultraviolet light. Then, the central adhesive layer is cured by step heating and slow cooling to control the curing shrinkage rate of the adhesive layer and reduce the impact of curing internal stress on the MiniLED beads and circuits. S5. After post-processing and performance testing, the finished module is obtained.

[0037] Comparative Example 1: Conventional OCA dry adhesive vacuum full lamination process Compared to existing technologies: the most mainstream full lamination solution for small and medium-sized LCMs currently uses solid OCA optical adhesive for bonding; Specific implementation steps: S1. Complete the backlight module assembly and surface cleaning without plasma pretreatment; S2. Apply a single layer of solid OCA optical adhesive film to the backlight light-emitting surface and remove air bubbles between the adhesive film and the backlight by pre-pressing with rollers. S3. Peel off the upper release film of the OCA adhesive film, send the backlight and LCD panel into the vacuum bonding cavity, and perform overall vacuum pressing after visual alignment. S4. The laminated module is sent into a high-pressure defoaming kettle and defoamed under high temperature and high pressure to eliminate residual microbubbles. S5. Remove the module for post-processing and testing.

[0038] Comparative Example 2: Conventional LOCA liquid adhesive full lamination process Compared to existing technologies: liquid adhesive bonding solutions commonly used in large-size LCMs, with frameless prefabricated adhesive barrier structures; Specific implementation steps: S1. Complete the backlight module assembly and surface cleaning without plasma pretreatment; S2. A single layer of liquid optical adhesive is applied to the backlight light-emitting surface by dispensing, without a pre-made adhesive-blocking structure. S3. Under vacuum conditions, the LCD panel is aligned and placed on top of the adhesive layer, and the adhesive is spread and filled to the entire bonding surface by pressing the flat plate together. S4. Use overall ultraviolet exposure to completely cure the liquid adhesive; S5. Clean up any excess glue from the edges and perform post-processing and inspection.

[0039] Comparative Example 3: Bonding process using single-layer liquid adhesive + edge foam adhesive strip Compared with existing technology: an improved solution that adds a barrier structure but does not have a heterogeneous adhesive layer and a zoned curing design; Specific implementation steps: S1. Complete the backlight module assembly and surface cleaning without plasma pretreatment; S2. Attach foam double-sided tape to the edge of the backlight output surface as a sealant structure, and apply a single layer of liquid optical adhesive to the middle area. S3. The LCD panel is aligned and pressed under vacuum, relying on foam strips to prevent excess adhesive. S4. The liquid adhesive is cured by heating, and the foam strips also serve to bond and fix the adhesive. S5. Perform post-processing and testing.

[0040] Performance comparison test and results All samples were tested under the same conditions. The test items and results are shown in the table below: Results Analysis Optical performance: The transmittance and brightness uniformity of the embodiments of the present invention are significantly better than those of all comparative examples. This is because the plasma pretreatment and the refractive index matching central adhesive layer eliminate interfacial air reflection, while the low modulus adhesive layer protects the microstructure of the prism from pressure damage, thus ensuring light output uniformity.

[0041] Yield performance: The embodiments of the present invention completely solve the problem of glue overflow, and the defects of pressure damage and bubbles are reduced by an order of magnitude compared with the prior art. The core lies in the sealing and limiting effect of the prefabricated high modulus glue baffle frame, and the synergistic effect of vacuum progressive pressing + glue layer self-venting.

[0042] Reliability: The debonding rate after high and low temperature cycling is much lower than that of the comparative example. This is due to the plasma anchoring structure which improves the interfacial adhesion, and the stepped curing stress relief design which reduces the internal stress of the adhesive layer and avoids interfacial debonding under temperature change cycling.

[0043] Production efficiency: By eliminating the high-pressure defoaming process, the processing time for a single module is significantly shortened compared to the conventional OCA process, resulting in a significant improvement in production efficiency.

[0044] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A bonding process between an LCM liquid crystal panel and a backlight module, characterized in that: The bonding process includes the following steps: S1. Complete the optical stacking assembly of the backlight module, and use a reactive gas source to perform low-temperature plasma modification pretreatment on the light-emitting surface of the backlight module. S2. Pre-fabricate a double-layer heterogeneous adhesive layer on the backlight emitting surface: First, apply a high-modulus UV-curable adhesive to the non-display area at the edge of the backlight emitting surface, and form a closed sealing frame after semi-curing; then apply a low-modulus liquid optical adhesive to the effective display area enclosed by the sealing frame to form a central buffer adhesive layer. S3. The backlight module with the pre-made heterogeneous adhesive layer and the LCD panel are placed together in a vacuum environment. After visual alignment, rollers are used to gradually press them from the center of the bonding area to the four sides to complete the pre-bonding. S4. Adhesive layer curing is completed using a zoned gradient curing process: First, the edge sealing frame is completely cured by ultraviolet light irradiation to achieve relative positioning and edge sealing between the backlight module and the LCD panel; then, the central buffer adhesive layer is cross-linked and cured using a stepped temperature curing process, and the internal stress of the adhesive layer is released by cooling after curing. S5. Perform post-processing and performance testing on the laminated modules.

2. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The low-temperature plasma modification pretreatment in S1 uses a mixture of inert gas and oxygen as the reaction gas source. After treatment, a micro-nano-scale rough anchoring structure is formed on the surface of the optical film on the backlight output surface, while eliminating static electricity on the film surface.

3. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The sealing baffle frame in S2 is continuously closed along the edge of the backlight emitting surface, and a safe distance is left between the inner side of the baffle frame and the edge of the effective display area; the sealing baffle frame has shape strength after semi-curing treatment, and its elastic modulus is higher than that of the central buffer adhesive layer after curing after complete curing.

4. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 3, characterized in that: The sealing and sealing frame and the central buffer adhesive layer are bonded together at adjacent interfaces to form an integral adhesive layer structure. The interfacial adhesion of the two adhesive layers is matched, and there is no risk of delamination or peeling after curing.

5. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The height of the adhesive surface of the central buffer adhesive layer in S2 is lower than the height of the top surface of the sealing adhesive frame; the central buffer adhesive layer has low modulus and high flow wettability before curing, and can spontaneously wet and fill the gaps in the optical microstructure of the backlight emitting surface. After curing, the refractive index matches the refractive index of the optical film of the backlight emitting surface.

6. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The vacuum environment in S3 maintains a stable high vacuum level; the visual precision alignment uses the alignment marks on the backlight module and the LCD panel as a reference to achieve precise alignment in the horizontal, vertical and angular directions; during the roller progressive pressing process, the adhesive layer spreads evenly from the center to the surrounding area as the pressing process progresses, and the gas between the interfaces is discharged simultaneously.

7. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The curing of the edge sealing frame in S4 uses an ultraviolet LED light source, which exposes only the edge frame area in a directional manner. After exposure, the sealing frame is completely cross-linked and cured, forming a rigid support frame and sealing barrier, which restricts the outward flow of the central buffer adhesive layer.

8. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The stepped temperature curing process of the central buffer adhesive layer in S4 is divided into a preliminary cross-linking stage and a deep curing stage. During the curing process, the temperature is gradually increased so that the adhesive layer slowly completes the cross-linking reaction. After the curing is completed, the curing stress inside the adhesive layer is released by gradually cooling down to avoid stress concentration that could cause the adhesive layer to warp or desorb.

9. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 6, characterized in that: The progressive pressing process of S3 is coordinated with the flow and wettability of the central buffer adhesive layer to simultaneously discharge the gas between the interfaces during the pressing process.

10. The bonding process between an LCM liquid crystal panel and a backlight module according to claim 1, characterized in that: The post-processing in S5 includes module edge cleaning and appearance inspection, and the performance testing includes optical performance testing and structural reliability testing.

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