Touch screen SCA optical adhesive bonding process and sunglass line elimination method

Abstract

This invention discloses a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like defects, belonging to the field of touchscreen manufacturing technology. The method includes pre-bonding treatment, bonding process, debubbling process, curing process, and testing and verification. By selecting an SCA optical adhesive with stronger deformation resistance and combining optimized bonding, debubbling, and curing process parameters, such as stepped pressure bonding, low-temperature and low-pressure debubbling, stepped UV curing, and slow cooling, this invention effectively solves the problem of sunglasses-like optical defects caused by the microscopic deformation of the SCA optical adhesive during touchscreen bonding. This method significantly reduces the defect rate of sunglasses-like defects, improves the display effect and user experience of the touchscreen when wearing polarized sunglasses, and is suitable for the mass production of high-quality touchscreens.

Description

Technical Field

[0001] This invention relates to a touch screen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, belonging to the field of touch screen manufacturing technology. Background Technology

[0002] Touchscreens are widely used in daily life, and the bonding of optical adhesives is a crucial step in their manufacturing process, determining the display effect. Solid Optically Clear Adhesive (SCA), a hot-melt optical adhesive, is widely used for bonding touchscreen cover plates to functional sheets or display modules due to its excellent filling and adhesion properties. However, in actual production, especially after bonding glass-to-glass (GG) structure touchscreens, circular or striped marks resembling "sunglasses patterns" often appear on the screen when viewed under a white interface while wearing polarized sunglasses, severely affecting visual effects and product quality. Analysis reveals that the root cause of this phenomenon lies in the material properties of SCA optical adhesive. During vacuum hot-press bonding, uneven heating or pressure can cause microscopic deformation of the SCA adhesive layer, forming stress lines. When these microscopic deformations interact with the polarizer of the display screen itself and the polarization direction of the polarized sunglasses worn by the user, light is concentrated, refracted, or interfered with, resulting in visible marks at specific angles. In existing technologies, simple optimizations are usually made by adjusting the bonding pressure or temperature, but it is difficult to fundamentally eliminate this problem. Especially for high-end display products with stringent requirements, the defect rate of tinted screen patterns remains high, becoming a bottleneck restricting the improvement of touch screen quality. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, comprising the following steps: Pre-lamination treatment: Plasma cleaning is performed on the lamination surfaces of the cover plate, functional sheets and display modules to reduce their surface energy; Bonding process: The anti-deformation SCA optical adhesive is placed between the cover plate and the functional sheet, and machine bonding is used, with stepped pressure applied to make the adhesive layer melt evenly. Degassing process: Vacuum degassing is performed at a temperature lower than the degassing temperature of ordinary SCA optical adhesive and at a pressure lower than the degassing pressure of ordinary SCA optical adhesive. Curing process: Stepped UV curing is adopted, first low-energy pre-curing, then high-energy full curing, and then slow cooling after curing.

[0004] Preferably, the deformation-resistant SCA optical adhesive is a single-layer structure colloid; or a double-layer structure colloid, including a molecular weight layer and a high molecular weight layer; or a triple-layer structure colloid, including a first low molecular weight layer, a high molecular weight layer and a second low molecular weight layer stacked sequentially; the low molecular weight layer is used to absorb and buffer deformation, and the high molecular weight layer is used to provide structural support and resist deformation.

[0005] Preferably, the single-layer structure colloid is selected from the Gaoren SCA-AH series optical adhesive or the TOCA series low-temperature flow optical adhesive, or other optical adhesives with low hardness and high elongation, with a Shore A hardness of 5-15 degrees and an elongation of 300%-500%.

[0006] Preferably, the deformation-resistant SCA optical adhesive of the two-layer or three-layer structure colloid can be a commercially available product that meets the requirements, or it can be made in-house. For example: The preparation method of the double-layer structure anti-deformation SCA optical adhesive includes the following steps: a. Preparation of low molecular weight adhesive: Dissolve acrylate prepolymer with a molecular weight of 5000-15000, photoinitiator, and leveling agent in ethyl acetate and stir until homogeneous; b. Preparation of high molecular weight adhesive: Dissolve acrylate prepolymer with a molecular weight of 50,000-150,000, photoinitiator, and leveling agent in ethyl acetate and stir until homogeneous; c. Using a multilayer co-extrusion coating method, the adhesive solutions prepared in steps a and b are sequentially coated onto the release film to form a double-layer structure; d. Baking to form a gel film; e. Cover the adhesive film with another release film to obtain the finished product.

[0007] The preparation method of the three-layer deformation-resistant SCA optical adhesive includes the following steps: a. Preparation of the first low molecular weight adhesive layer: Dissolve an acrylate prepolymer with a molecular weight of 5000-15000, a photoinitiator, and a leveling agent in ethyl acetate and stir until homogeneous; b. Preparation of high molecular weight adhesive: Dissolve acrylate prepolymer with a molecular weight of 50,000-150,000, photoinitiator, and leveling agent in ethyl acetate and stir until homogeneous; c. Preparation of the second low molecular weight layer adhesive: its formulation is the same as in step a; d. Using a multilayer co-extrusion coating method, the adhesive solutions prepared in steps a, b, and c are sequentially coated onto the release film to form a three-layer structure; e. Baking to form a film; f. Cover the adhesive film with another release film to obtain the finished product.

[0008] Preferably, the preparation method of the three-layer deformation-resistant SCA optical adhesive specifically includes the following steps: a. Preparation of the first low molecular weight layer adhesive: by weight, dissolve 100 parts of acrylate prepolymer with a molecular weight of 5000-15000, 0.5-1.5 parts of photoinitiator, and 0.1-0.5 parts of leveling agent in 50-80 parts of ethyl acetate and stir until homogeneous; b. Preparation of high molecular weight adhesive: By weight, dissolve 100 parts of acrylate prepolymer with a molecular weight of 50,000-150,000, 0.5-1.5 parts of photoinitiator, and 0.1-0.5 parts of leveling agent in 50-80 parts of ethyl acetate and stir until homogeneous; c. Preparation of the second low molecular weight layer adhesive: its formulation is the same as in step a; d. Using a multilayer co-extrusion coating method, the adhesive solutions prepared in steps a, b, and c are sequentially coated onto the release film to form a three-layer structure; e. Bake at 60-80℃ for 5-10 minutes to remove the solvent and form a film with a thickness of 150-200μm, wherein the thickness of the first low molecular weight layer and the second low molecular weight layer are each 30-50μm, and the thickness of the high molecular weight layer is 90-120μm. f. Cover the adhesive film with another release film to obtain the finished product.

[0009] Preferably, the acrylate prepolymers in steps a and c are selected from one or more copolymers of butyl acrylate, isooctyl acrylate, and hydroxyethyl acrylate; the acrylate prepolymers in step b are selected from one or more copolymers of methyl acrylate, methyl methacrylate, and isobornyl acrylate; and the photoinitiator is selected from one or more of 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0010] Preferably, in the pre-bonding treatment step, the plasma cleaning time is 30-60 seconds, and the surface energy of the bonding surface is reduced to below 22 dynes / cm after cleaning.

[0011] Preferably, in the bonding process, the stepped pressure application specifically includes: first applying a pressure of 50 psi for 10-15 seconds; then applying a pressure of 150 psi for 20-30 seconds; and finally applying a pressure of 300 psi for 30-45 seconds; the vacuum degree during machine bonding is not lower than -0.095 MPa; and the preheating temperature for uniformly melting the adhesive layer is 70-75°C.

[0012] Preferably, in the degassing process, the degassing temperature is 70-73℃ and the pressure is 0.8-1.0 kg / cm².2 The duration is 50-70 minutes.

[0013] Preferably, in the curing process, the stepped UV curing specifically includes: first, using 100-200 mJ / cm²... 2 Pre-curing is performed using energy; then 500-800 mJ / cm 2 The energy is used for complete solidification.

[0014] Preferably, in the curing process step, the cooling rate of the slow cooling does not exceed 5°C / minute.

[0015] Preferably, the method further includes an environmental control step: the cleanliness of the environment being fitted is not lower than Class 1000.

[0016] Preferably, the method further includes a positioning accuracy control step: using a visual positioning system to ensure that the fitting deviation of the cover plate, functional piece and display module is less than ±0.02 mm.

[0017] Preferably, the method further includes a bubble control step: ensuring that the SCA optical adhesive is wrinkle-free before bonding and that the release film is peeled off at an angle of less than 30°; and immediately inspecting after pressing and melting, and reworking immediately if bubbles are found.

[0018] Preferably, the method further includes a detection and verification step, which involves performing polarized sunglasses detection on the finished product to ensure that there are no visible sunglasses patterns. The specific steps include: First article inspection: Sunglasses are inspected before each batch of production. Mass production can only begin after confirming that there are no abnormalities. Sampling inspection during the process: hourly sampling inspections are conducted while wearing polarized sunglasses and rotating at 45°, 90°, and 135° angles. Finished product full inspection: A sunglasses inspection station is set up to conduct 100% full inspection on each finished product.

[0019] Preferably, the test conditions for the detection and verification step are: D65 standard light source, illuminance ≥500 lux, observation distance 30 cm, viewing angle ±15°, polarized sunglasses rotated 360°, and the judgment criteria are no visible circular or striped marks and no local brightness abnormalities.

[0020] The beneficial effects of this invention are: Compared with existing technologies, the touchscreen SCA optical adhesive bonding process and sunglasses-like texture elimination method provided by this invention, through a systematic solution combining material upgrades and process optimization, has the following significant advantages: First, at the material level, the use of SCA-AH series optical adhesives with stronger deformation resistance, low hardness and high elongation, or three-layer structures reduces the possibility of microscopic deformation of the adhesive layer during hot pressing, enhancing the adhesive layer's resistance to stress. Second, at the process level, the bonding process employs stepped pressure and machine bonding, ensuring pressure uniformity and avoiding localized stress concentration; the degassing process innovatively uses low temperature, low pressure, and long-term processing, effectively reducing the additional deformation risk caused by high temperature and high pressure; the curing process introduces stepped UV curing and slow cooling, fully releasing the internal stress of the adhesive layer and preventing uneven shrinkage. Third, in terms of process control, plasma cleaning reduces substrate surface energy, a visual positioning system ensures bonding accuracy, and strict cleanliness control and bubble management further improve the uniformity of the adhesive layer and the quality of interface bonding. Ultimately, a comprehensive inspection process for sunglasses, including first-article inspection, in-process sampling, and final product inspection, ensured 100% product qualification. This invention significantly reduces the defect rate of sunglasses patterns from 10-30% in existing technologies to below 1%, or even eliminates it entirely, enabling the production of sunglasses-friendly touchscreens and significantly improving product display quality, user satisfaction, and market competitiveness. Attached Figure Description

[0021] Figure 1 This invention relates to a schematic diagram of the existing touchscreen bonding structure and light propagation. Detailed Implementation

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

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used in the following examples are all purchased from commercial channels.

[0025] like Figure 1As shown in the figure, the layering relationship of the glass cover, SCA optical adhesive layer, functional sheet and display module is clearly shown in the cross-sectional view. The propagation path of light is shown in the figure. In particular, the refraction changes that occur at the micro-deformation of the adhesive layer intuitively show the cause of the sunglasses texture.

[0026] Preparation example: Preparation of a three-layer structure anti-deformation SCA optical adhesive The preparation of a three-layer anti-deformation SCA optical adhesive, which is used in the bonding process of subsequent embodiments of the present invention, is merely illustrative and does not imply that other formulations / structures of optical adhesives within the scope of protection of the claims of the present invention cannot achieve the effects described in the present invention. The specific steps include: Adhesive preparation: First low molecular weight adhesive layer (A glue): In a reactor, add 100 parts by weight of butyl acrylate-isooctyl acrylate copolymer (molar ratio 7:3) with a molecular weight of approximately 10,000, 1.0 part of photoinitiator 1-hydroxycyclohexylphenyl ketone, 0.3 parts of leveling agent BYK-333, and 65 parts of ethyl acetate. Stir at 500 rpm for 2 hours until completely dissolved, then filter for later use.

[0027] High molecular weight adhesive (B-type adhesive): In another reactor, add 100 parts by weight of methyl methacrylate-isoborneol acrylate copolymer (molar ratio 6:4), 1.0 part of photoinitiator 1-hydroxycyclohexylphenyl ketone, 0.3 parts of leveling agent BYK-333, and 65 parts of ethyl acetate. Stir at 500 rpm for 2 hours until completely dissolved, then filter for later use.

[0028] The second low molecular weight adhesive layer (C adhesive) has the same formulation and preparation method as the A adhesive.

[0029] Multilayer co-extrusion coating: A three-layer co-extrusion die is used to simultaneously extrude adhesives A, B, and C in sequence and coat them onto a 50μm thick PET release film. The coating thickness is controlled by adjusting the feed rate of each layer.

[0030] Drying and shaping: The coated film is placed in an oven and baked at 70°C for 8 minutes to remove the solvent. The total thickness of the film after drying is 175 μm, of which the first low molecular weight layer is 40 μm thick, the high molecular weight layer is 95 μm thick, and the second low molecular weight layer is 40 μm thick.

[0031] Lamination and winding: Cover the dried adhesive film with another 50μm PET release film, and then wind it up to obtain the finished three-layer structure anti-deformation SCA optical adhesive.

[0032] Example 1

[0033] This embodiment provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, using a three-layer anti-deformation SCA optical adhesive prepared in the preparation example. The specific steps are as follows: Material preparation: The three-layer anti-deformation SCA optical adhesive prepared by the preparation example has a total thickness of 175 μm. The structure is as follows: first low molecular weight layer (40 μm, molecular weight 10000 butyl acrylate-isooctyl acrylate copolymer) - high molecular weight layer (95 μm, molecular weight 100000 methyl methacrylate-isobornyl acrylate copolymer) - second low molecular weight layer (40 μm, molecular weight 10000 butyl acrylate-isooctyl acrylate copolymer), and both sides are covered with 50 μm PET release film.

[0034] Pre-bonding treatment: Place the glass cover and the functional film (ITO Film) with the bonding surfaces facing up in a plasma cleaner, set the power to 300W, and introduce a mixture of oxygen and argon gas (volume ratio 1:1) for 45 seconds. Immediately after cleaning, test the surface energy with a dyne pen to confirm a reduction to 20 dynes / cm.

[0035] Bonding Process: In a Class 1000 cleanroom, peel off the release film from one side of the SCA optical adhesive, align the adhesive layer with the bonding surface of the cover plate, and bond using a fully automated vacuum bonding machine. Bonding Parameter Settings: Vacuum degree -0.098 MPa, preheating temperature 73℃, preheating time 30 seconds. Bonding pressure is applied in a stepped manner: first stage: 50 psi pressure, held for 12 seconds; second stage: 150 psi pressure, held for 25 seconds; third stage: 300 psi pressure, held for 40 seconds. After bonding, remove the semi-finished product and carefully inspect the entire adhesive layer area under a high-intensity light stage with an illuminance of at least 1000 lux using a 10x magnifying glass to confirm the absence of any air bubbles ≥0.1mm in size.

[0036] Degassing process: The laminated semi-finished product is placed in a high-pressure degassing machine, and the degassing temperature is set to 72℃ and the pressure to 0.9 kg / cm². 2 The processing time is 60 minutes. After degassing is complete, allow the pressure to release naturally before removing the product.

[0037] Curing process: The degassed semi-finished product is placed in a UV curing oven and cured in a stepped manner: first at 150 mJ / cm 2 Pre-curing is performed using energy, with an irradiation time of approximately 15 seconds; then, at 650 mJ / cm², [the process continues]. 2 The device is subjected to full curing with energy, with an irradiation time of approximately 60 seconds. After curing, it is slowly cooled to room temperature at a rate of 4°C / minute.

[0038] Testing and verification: Under a D65 standard light source, the illuminance of the light source was calibrated to 550 lux using a lux meter. The finished product was placed 30 cm away from the screen. Polarized sunglasses (polarization direction of 45°) were worn and the screen was slowly rotated 360°. The screen was observed at 45°, 90° and 135° angles to confirm that there were no circular, striped or localized abnormal brightness marks on the white interface of the screen (255 gray levels, highest brightness).

[0039] Example 2

[0040] This embodiment provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, using a three-layer anti-deformation SCA optical adhesive prepared in the preparation example. The specific steps are as follows: Material preparation: The three-layer anti-deformation SCA optical adhesive prepared by the preparation example was used.

[0041] Pre-bonding treatment: Place the glass cover and the functional film (ITO Film) with the bonding surfaces facing up in a plasma cleaner, set the power to 300W, and introduce a mixture of oxygen and argon gas (volume ratio 1:1) for 30 seconds. Immediately after cleaning, test the surface energy with a dyne pen to confirm a reduction to 21 dynes / cm.

[0042] Bonding Process: In a Class 1000 cleanroom, peel off the release film from one side of the SCA optical adhesive, align the adhesive layer with the bonding surface of the cover plate, and bond using a fully automated vacuum bonding machine. Bonding Parameter Settings: Vacuum degree -0.095 MPa, preheating temperature 70℃, preheating time 30 seconds. Bonding pressure is applied in a stepped manner: first stage: apply 50 psi pressure, hold for 15 seconds; second stage: apply 150 psi pressure, hold for 20 seconds; third stage: apply 300 psi pressure, hold for 30 seconds. After bonding, remove the semi-finished product and carefully inspect the entire adhesive layer area under a high-intensity light stage with an illuminance of at least 1000 lux using a 10x magnifying glass to confirm the absence of any air bubbles ≥0.1mm in size.

[0043] Degassing process: The laminated semi-finished product is placed in a high-pressure degassing machine, and the degassing temperature is set to 70℃ and the pressure to 0.8kg / cm². 2 The processing time is 70 minutes. After degassing is complete, allow the pressure to release naturally before removing the product.

[0044] Curing process: The degassed semi-finished product is placed in a UV curing oven and cured in a stepped manner: first at 100 mJ / cm 2 Pre-curing is performed using energy for approximately 10 seconds; then, 500 mJ / cm² is applied. 2 The device is subjected to full curing with energy for approximately 50 seconds. After curing, it is slowly cooled to room temperature at a rate of 5°C / minute.

[0045] Testing and verification: Under a D65 standard light source, the illuminance of the light source was calibrated to 550 lux using a lux meter. The finished product was placed 30 cm away from the screen. Polarized sunglasses (polarization direction of 45°) were worn and the screen was slowly rotated 360°. The screen was observed at 45°, 90° and 135° angles to confirm that there were no circular, striped or localized abnormal brightness marks on the white interface of the screen (255 gray levels, highest brightness).

[0046] Example 3

[0047] This embodiment provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, using a three-layer anti-deformation SCA optical adhesive prepared in the preparation example. The specific steps are as follows: Material preparation: The three-layer anti-deformation SCA optical adhesive prepared by the preparation example was used.

[0048] Pre-bonding treatment: Place the glass cover and the functional film (ITO Film) with the bonding surfaces facing up in a plasma cleaner, set the power to 300W, and introduce a mixture of oxygen and argon gas (volume ratio 1:1) for 60 seconds. Immediately after cleaning, test the surface energy with a dyne pen to confirm a reduction to 19 dynes / cm.

[0049] Bonding Process: In a Class 1000 cleanroom, peel off the release film from one side of the SCA optical adhesive, align the adhesive layer with the bonding surface of the cover plate, and bond using a fully automated vacuum bonding machine. Bonding Parameter Settings: Vacuum degree -0.099 MPa, preheating temperature 75℃, preheating time 30 seconds. Bonding pressure is applied in a stepped manner: first stage: apply 50 psi pressure, hold for 10 seconds; second stage: apply 150 psi pressure, hold for 30 seconds; third stage: apply 300 psi pressure, hold for 45 seconds. After bonding, remove the semi-finished product and carefully inspect the entire adhesive layer area under a high-intensity light stage with an illuminance of at least 1000 lux using a 10x magnifying glass to confirm the absence of any air bubbles ≥0.1mm in size.

[0050] Degassing process: The laminated semi-finished product is placed in a high-pressure degassing machine, and the degassing temperature is set to 73℃ and the pressure to 1.0 kg / cm². 2 Processing time: 50 minutes. After degassing is complete, allow the pressure to release naturally before removing the product.

[0051] Curing process: The degassed semi-finished product is placed in a UV curing oven and cured in a stepped manner: first at 200 mJ / cm 2 Pre-curing is performed using energy, with an irradiation time of approximately 20 seconds; then, 800 mJ / cm² is applied. 2 The device is subjected to full curing with energy for approximately 80 seconds. After curing, it is slowly cooled to room temperature at a rate of 3°C / minute.

[0052] Testing and verification: Under a D65 standard light source, the illuminance of the light source was calibrated to 550 lux using a lux meter. The finished product was placed 30 cm away from the screen. Polarized sunglasses (polarization direction of 45°) were worn and the screen was slowly rotated 360°. The screen was observed at 45°, 90° and 135° angles to confirm that there were no circular, striped or localized abnormal brightness marks on the white interface of the screen (255 gray levels, highest brightness).

[0053] Example 4

[0054] This embodiment provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, replacing the three-layer structural adhesive with a commercially available SCA-AH series single-layer optical adhesive. The specific steps are as follows: Material Preparation: A commercially available single-layer, deformation-resistant SCA optical adhesive specifically designed to resist sunglasses scratches was selected (its performance parameters meet the following requirements: Shore A hardness of 5-15 degrees and elongation of 300%-500%). As an example, this embodiment uses a solid film-like SCA optical adhesive that meets the above parameter range, with a total thickness of 150 μm and double-sided 50 μm PET release film. Testing showed that its hardness is Shore A hardness of 10 degrees and its elongation of 350%.

[0055] Pre-bonding treatment: Place the glass cover and the functional film (ITO Film) with the bonding surfaces facing up in a plasma cleaner, set the power to 300W, and introduce a mixture of oxygen and argon gas (volume ratio 1:1) for 45 seconds. Immediately after cleaning, test the surface energy with a dyne pen to confirm a reduction to 20 dynes / cm.

[0056] Bonding Process: In a Class 1000 cleanroom, peel off the release film from one side of the SCA optical adhesive, align the adhesive layer with the bonding surface of the cover plate, and bond using a fully automated vacuum bonding machine. Bonding Parameter Settings: Vacuum degree -0.098 MPa, preheating temperature 73℃, preheating time 30 seconds. Bonding pressure is applied in a stepped manner: first stage: 50 psi pressure, held for 12 seconds; second stage: 150 psi pressure, held for 25 seconds; third stage: 300 psi pressure, held for 40 seconds. After bonding, remove the semi-finished product and carefully inspect the entire adhesive layer area under a high-intensity light stage with an illuminance of at least 1000 lux using a 10x magnifying glass to confirm the absence of any air bubbles ≥0.1mm in size.

[0057] Degassing process: The laminated semi-finished product is placed in a high-pressure degassing machine, and the degassing temperature is set to 72℃ and the pressure to 0.9 kg / cm². 2 The processing time is 60 minutes. After degassing is complete, allow the pressure to release naturally before removing the product.

[0058] Curing process: The degassed semi-finished product is placed in a UV curing oven and cured in a stepped manner: first at 150 mJ / cm2 Pre-curing is performed using energy, with an irradiation time of approximately 15 seconds; then, at 650 mJ / cm², [the process continues]. 2 The device is subjected to full curing with energy, with an irradiation time of approximately 60 seconds. After curing, it is slowly cooled to room temperature at a rate of 4°C / minute.

[0059] Testing and verification: Under a D65 standard light source, the illuminance of the light source was calibrated to 550 lux using a lux meter. The finished product was placed 30 cm away from the screen. Polarized sunglasses (polarization direction of 45°) were worn and the screen was slowly rotated 360°. The screen was observed at 45°, 90° and 135° angles to confirm that there were no circular, striped or localized abnormal brightness marks on the white interface of the screen (255 gray levels, highest brightness).

[0060] Example 5

[0061] This embodiment provides a touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like textures. The three-layer structural adhesive is replaced with TOCA series low-temperature flow optical adhesive. This product is liquid and needs to be pre-formed into a film. The specific steps are as follows: Material Preparation: A commercially available liquid optically transparent adhesive (LOCA) meeting the requirements of low hardness and high elongation was selected as the raw material for film preparation. This liquid optical adhesive meets the following criteria: Shore A hardness of 5-15 and elongation of 300%-500%. As an example, this embodiment uses a liquid optical adhesive that meets the above parameter range. First, it was prepared into a film: 100 parts by weight of liquid optical adhesive were taken, and 0.8 parts of photoinitiator (such as 2-hydroxy-2-methyl-1-phenylpropanone) were added. After stirring evenly, the mixture was coated onto a 50μm PET release film using a doctor blade coating method, controlling the doctor blade gap to be 150μm. It was then pre-baked in an 80℃ oven for 5 minutes to form a semi-solid adhesive film. Another 50μm PET release film was then applied, resulting in an SCA optical adhesive film with a thickness of approximately 120μm.

[0062] Pre-bonding treatment: Place the glass cover and the functional film (ITO Film) with the bonding surfaces facing up in a plasma cleaner, set the power to 300W, and introduce a mixture of oxygen and argon gas (volume ratio 1:1) for 45 seconds. Immediately after cleaning, test the surface energy with a dyne pen to confirm a reduction to 20 dynes / cm.

[0063] Bonding Process: In a Class 1000 cleanroom, peel off the release film from one side of the SCA optical adhesive, align the adhesive layer with the bonding surface of the cover plate, and bond using a fully automated vacuum bonding machine. Bonding Parameter Settings: Vacuum degree -0.098 MPa, preheating temperature 73℃, preheating time 30 seconds. Bonding pressure is applied in a stepped manner: first stage: 50 psi pressure, held for 12 seconds; second stage: 150 psi pressure, held for 25 seconds; third stage: 300 psi pressure, held for 40 seconds. After bonding, remove the semi-finished product and carefully inspect the entire adhesive layer area under a high-intensity light stage with an illuminance of at least 1000 lux using a 10x magnifying glass to confirm the absence of any air bubbles ≥0.1mm in size.

[0064] Degassing process: The laminated semi-finished product is placed in a high-pressure degassing machine, and the degassing temperature is set to 72℃ and the pressure to 0.9 kg / cm². 2 The processing time is 60 minutes. After degassing is complete, allow the pressure to release naturally before removing the product.

[0065] Curing process: The degassed semi-finished product is placed in a UV curing oven and cured in a stepped manner: first at 150 mJ / cm 2 Pre-curing is performed using energy, with an irradiation time of approximately 15 seconds; then, at 650 mJ / cm², [the process continues]. 2 The device is subjected to full curing with energy, with an irradiation time of approximately 60 seconds. After curing, it is slowly cooled to room temperature at a rate of 4°C / minute.

[0066] Testing and verification: Under a D65 standard light source, the illuminance of the light source was calibrated to 550 lux using a lux meter. The finished product was placed 30 cm away from the screen. Polarized sunglasses (polarization direction of 45°) were worn and the screen was slowly rotated 360°. The screen was observed at 45°, 90° and 135° angles to confirm that there were no circular, striped or localized abnormal brightness marks on the white interface of the screen (255 gray levels, highest brightness).

[0067] Comparative Example 1 This comparative example uses the traditional SCA optical adhesive bonding process without using any of the optimization techniques of this invention. The specific steps are as follows: Material preparation: A common commercial solid SCA optical adhesive with a thickness of 125μm and no special anti-deformation design was selected (its performance parameters range: Shore A hardness >20 degrees, elongation <200%). As a control, a common SCA optical adhesive with a total thickness of 125μm and release film on both sides was selected for this comparative example.

[0068] Pre-bonding treatment: No plasma cleaning step is required. Simply wipe the bonding surface with a lint-free cloth dampened with anhydrous alcohol and let it air dry at room temperature for 30 seconds.

[0069] Bonding process: A semi-automatic bonding machine is used, with a vacuum degree of -0.09 MPa, a preheating temperature of 85℃, and a preheating time of 30 seconds. The bonding pressure is applied in one go at 250 psi and held for 45 seconds, with no step pressure application.

[0070] Degassing process: Degassing temperature 85℃, pressure 1.5 kg / cm² 2 Processing time: 40 minutes.

[0071] Curing process: One-time high-energy curing, energy 600 mJ / cm 2 The irradiation time is about 60 seconds, and after curing, it cools naturally to room temperature without any temperature control measures.

[0072] Detection and verification: Same as in Example 1.

[0073] Comparative Example 2 This comparative example uses the anti-deformation material (three-layer structural adhesive) of the present invention, but follows the traditional process parameters. The specific steps are as follows: Material preparation: Same as in Example 1, using the three-layer anti-deformation SCA optical adhesive prepared in the preparation example.

[0074] Pre-bonding treatment: No plasma cleaning step is required. Simply wipe the bonding surface with a lint-free cloth dampened with anhydrous alcohol and let it air dry at room temperature for 30 seconds.

[0075] Bonding process: A semi-automatic bonding machine is used, with a vacuum degree of -0.09 MPa, a preheating temperature of 85℃, and a preheating time of 30 seconds. The bonding pressure is applied in one go at 250 psi and held for 45 seconds, with no step pressure application.

[0076] Degassing process: Degassing temperature 85℃, pressure 1.5 kg / cm² 2 Processing time: 40 minutes.

[0077] Curing process: One-time high-energy curing, energy 600 mJ / cm 2 The irradiation time is about 60 seconds, and after curing, it is allowed to cool naturally to room temperature.

[0078] Detection and verification: Same as in Example 1.

[0079] Comparative Example 3 This comparative example uses the anti-deformation material (three-layer structural adhesive) of the present invention, but the degassing process uses traditional high temperature and high pressure parameters. Other processes are the same as in Example 1. The specific steps are as follows: Material preparation: Same as in Example 1, using the three-layer anti-deformation SCA optical adhesive prepared in the preparation example.

[0080] Pre-bonding treatment: Same as in Example 1, plasma cleaning time 45 seconds, surface energy reduced to 20 dynes / cm.

[0081] Bonding process: Same as Example 1, cleanliness Class 1000, vacuum degree -0.098 MPa, preheating temperature 73℃, stepped pressurization: 50 psi / 12 seconds, 150 psi / 25 seconds, 300 psi / 40 seconds.

[0082] Degassing process: Degassing temperature 85℃, pressure 1.5 kg / cm² 2 Processing time: 40 minutes.

[0083] Curing process: Same as Example 1, stepped curing: 150 mJ / cm 2 Pre-cured, 650 mJ / cm 2 Full curing, cooling rate 4℃ / minute.

[0084] Detection and verification: Same as in Example 1.

[0085] Comparative Example 4 This comparative example uses the anti-deformation material (three-layer structural adhesive) of the present invention, but the curing process adopts a one-time high-energy curing method without step-by-step curing. Other processes are the same as in Example 1. The specific steps are as follows: Material preparation: Same as in Example 1, using the three-layer anti-deformation SCA optical adhesive prepared in the preparation example.

[0086] Pre-bonding treatment: Same as in Example 1, plasma cleaning time 45 seconds, surface energy reduced to 20 dynes / cm.

[0087] Bonding process: Same as Example 1, cleanliness Class 1000, vacuum degree -0.098 MPa, preheating temperature 73℃, stepped pressurization: 50 psi / 12 seconds, 150 psi / 25 seconds, 300 psi / 40 seconds.

[0088] Degassing process: Same as in Example 1, degassing temperature 72℃, pressure 0.9 kg / cm². 2 The time is 60 minutes.

[0089] Curing process: One-time high-energy curing, energy 600 mJ / cm 2 The irradiation time is about 60 seconds, and after curing, it is allowed to cool naturally to room temperature.

[0090] Detection and verification: Same as in Example 1.

[0091] Comparative Example 5 This comparative example uses the anti-deformation material (three-layer structural adhesive) of the present invention, but plasma cleaning was not performed before bonding. Other processes are the same as in Example 1, and the specific steps are as follows: Material preparation: Same as in Example 1, using the three-layer anti-deformation SCA optical adhesive prepared in the preparation example.

[0092] Pre-bonding treatment: No plasma cleaning step is required. Simply wipe the bonding surface with a lint-free cloth dampened with anhydrous alcohol and let it air dry at room temperature for 30 seconds.

[0093] Bonding process: Same as Example 1, cleanliness Class 1000, vacuum degree -0.098 MPa, preheating temperature 73℃, stepped pressurization: 50 psi / 12 seconds, 150 psi / 25 seconds, 300 psi / 40 seconds.

[0094] Degassing process: Same as in Example 1, degassing temperature 72℃, pressure 0.9 kg / cm². 2 The time is 60 minutes.

[0095] Curing process: Same as Example 1, stepped curing: 150 mJ / cm 2 Pre-cured, 650 mJ / cm 2 Full curing, cooling rate 4℃ / minute.

[0096] Detection and verification: Same as in Example 1.

[0097] The following methods were used to test all embodiments and comparative examples: Data detection methods 1. Method for detecting defect rate of sunglasses pattern The testing environment consisted of a D65 standard light source stage set up in a darkroom, with the light source illuminance calibrated to above 500 lux using a lux meter. One hundred finished touchscreens were used for each embodiment and comparative example, and after being lit up, set to a full white screen (255 gray levels) with maximum brightness. The inspector, wearing standard polarized sunglasses (45° polarization), observed the screen from a distance of 30 cm at a direct viewing angle (±15°). Keeping the head still, the inspector slowly rotated the polarized sunglasses from 0° to 360°, focusing on the 45°, 90°, and 135° angles. If any area of ​​the screen showed visible circular, striped, or localized abnormal brightness marks, it was considered a defective product. The number of defective products was counted, and the sunglasses pattern defect rate was calculated as (number of defective products / 100) × 100%.

[0098] 2. Method for detecting bubble rate after bonding The semi-finished product, after lamination and before degassing, was placed under a high-intensity light stage with an illumination of no less than 1000 lux, and the entire adhesive layer area was carefully inspected using a 10x high-magnification magnifying glass. The number of samples containing any air bubbles ≥ 0.1 mm in size was recorded. 100 pieces were taken from each example and comparative example for testing, and the air bubble rate after lamination was calculated as (number of samples containing air bubbles / 100) × 100%.

[0099] 3. Adhesive adhesion test method The test was conducted according to GB / T 9286-1998, "Cross-cut Test for Paint and Varnish Films". On the cured touchscreen, select the edge area of ​​the adhesive layer and use a cross-cut tester to draw 10×10 1mm×1mm squares on the adhesive surface. The scratches must penetrate the adhesive layer to the substrate. Apply 3M 600 tape to the marked area, press it firmly with a rubber roller, and then quickly peel it off at a 60° angle within 0.5-1 second. Observe the adhesive peeling under a 10x magnifying glass and rate the peeling area: Grade 0: Completely smooth cut edge, no squares peeled off; Grade 1: Peeling area no more than 5%; Grade 2: Peeling area 5%-15%; Grade 3: Peeling area 15%-35%; Grade 4: Peeling area 35%-65%; Grade 5: Peeling area greater than 65%.

[0100] As can be seen, all embodiments of the present invention exhibit excellent performance in the core indicator of sunglasses-like texture defect rate. Examples 1 and 3 achieved a 0% defect rate, while Examples 2, 4, and 5 achieved only 1%, significantly lower than all comparative examples. Comparative Example 1, using traditional materials and processes, had a defect rate as high as 28%, verifying the deficiencies of existing technologies. Although Comparative Example 2 used the three-layer anti-deformation material of the present invention, it still had a defect rate as high as 16% using traditional process parameters, indicating that material upgrades alone cannot completely solve the problem; they must be combined with process optimization. Comparative Example 3, by changing the degassing process to traditional high-temperature and high-pressure parameters, saw its defect rate rise to 9%; Comparative Example 4, by changing the curing process to one-time high-energy curing, saw its defect rate rise to 7%; and Comparative Example 5, by omitting plasma cleaning, had a defect rate of 5%. The defect rates of these three comparative examples were all higher than those of the embodiments, proving that the low-temperature degassing, stepped curing, and plasma cleaning processes of the present invention each make independent and significant contributions to eliminating sunglasses-like texture.

[0101] Regarding the bubble rate after lamination, Examples 1-5 were all controlled at 2-3%, which is better than Comparative Example 1's 15% and Comparative Example 2's 14%, indicating that the stepped pressure lamination process of the present invention has good degassing capability. The bubble rates of Comparative Examples 3-5 were 4%, 2%, and 3%, respectively, further confirming that the lamination process is the key to controlling bubbles.

[0102] Regarding adhesive adhesion, Examples 1-3 and 5 all achieved an optimal grade of 0, while Example 4 achieved a grade of 1, indicating that the plasma cleaning treatment of the present invention significantly improved the interfacial bonding strength. Comparative Example 1 (no plasma cleaning, ordinary material) achieved a grade of 3, Comparative Example 2 (no plasma cleaning, deformation-resistant material) achieved a grade of 2, and Comparative Example 5 (no plasma cleaning) achieved a grade of 3, fully demonstrating the necessity and effectiveness of the plasma cleaning step.

[0103] In summary, this invention, through a systematic approach involving material upgrades (three-layer anti-deformation adhesive), process optimization (stepped pressure bonding, low-temperature and low-pressure degassing, stepped UV curing, and slow cooling), and process control (plasma cleaning, cleanliness control, and alignment accuracy control), achieves a significant improvement in reducing the defect rate of sunglass patterns from 10-30% to below 1% or even 0%.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0105] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A touchscreen SCA optical adhesive bonding process and a method for eliminating sunglasses-like patterns, characterized in that, Includes the following steps: Pre-lamination treatment: Plasma cleaning is performed on the lamination surfaces of the cover plate, functional sheets and display modules to reduce their surface energy; Bonding process: The deformation-resistant SCA optical adhesive is placed between the cover plate and the functional sheet, and then bonded by machine with stepped pressure to ensure uniform melting of the adhesive layer. Degassing process: Vacuum degassing is performed at a temperature lower than the degassing temperature of ordinary SCA optical adhesive and at a pressure lower than the degassing pressure of ordinary SCA optical adhesive. Curing process: Stepped UV curing is adopted, first low-energy pre-curing, then high-energy full curing, and then slow cooling after curing.

2. The method according to claim 1, characterized in that, The deformation-resistant SCA optical adhesive is a single-layer structure colloid; or a double-layer structure colloid, including a molecular weight layer and a high molecular weight layer; or a triple-layer structure colloid, including a first low molecular weight layer, a high molecular weight layer and a second low molecular weight layer stacked sequentially.

3. The method according to claim 1, characterized in that, In the pre-bonding treatment step, the plasma cleaning time is 30-60 seconds, and the surface energy of the bonding surface is reduced to below 22 dynes / cm after cleaning.

4. The method according to claim 1, characterized in that, In the bonding process, the stepped pressure application specifically includes: first applying a pressure of 50 psi for 10-15 seconds; then applying a pressure of 150 psi for 20-30 seconds; and finally applying a pressure of 300 psi for 30-45 seconds.

5. The method according to claim 1, characterized in that, In the bonding process, the vacuum degree during machine bonding is not lower than -0.095 MPa; the preheating temperature for uniformly melting the adhesive layer is 70-75℃.

6. The method according to claim 1, characterized in that, In the degassing process, the degassing temperature is 70-73℃ and the pressure is 0.8-1.0 kg / cm². 2 The duration is 50-70 minutes.

7. The method according to claim 1, characterized in that, In the curing process steps, the stepped UV curing specifically includes: first, using 100-200 mJ / cm²... 2 Pre-curing is performed using energy; then 500-800 mJ / cm 2 The energy is used for complete solidification.

8. The method according to claim 1, characterized in that, In the curing process, the cooling rate of the slow cooling does not exceed 5°C / minute.

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