Graphene enhanced UV conductive silver adhesive for display and preparation method thereof

Abstract

The invention discloses a graphene enhanced UV conductive silver adhesive for display and a preparation method thereof. The graphene enhanced UV conductive silver adhesive is prepared from the following raw materials in parts by weight: 6 to 10 parts of bifunctional polyurethane acrylate, 1 to 3 parts of epoxy acrylate, 8 to 12 parts of UV monomer, 0.02 to 0.04 part of defoaming agent, 0.5 to 1 part of photoinitiator, 0.02 to 0.4 part of dispersing agent, 0.5 to 1 part of modified graphene and 75 to 85 parts of silver powder. The UV conductive silver adhesive for graphene enhanced display provided by the invention does not contain a solvent, is green and environment-friendly, is suitable for conductive bonding of electronic paper, can be rapidly cured by ultraviolet light, and can prevent the electronic paper from being damaged; the cured conductive silver adhesive is moderate in viscosity and excellent in adhesive dispensing performance; and the adhesive force to an FPL film, ITO conductive glass and other substrates is strong, and the conductive performance is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electronic paper display screen module packaging and conductive connection materials, and particularly relates to a graphene-reinforced UV conductive silver adhesive for display devices such as flexible electronic paper, electronic price tags, and electronic book readers, and is particularly suitable for low-temperature and rapid conductive bonding between FPL films and ITO conductive glass in electronic paper display screens. BACKGROUND

[0002] As the core material for the conductive connection of electronic components, conductive silver adhesive is mainly composed of silver powder (a conductive functional phase), a base resin (a bonding and supporting phase), and additives (dispersion, defoaming, and other functional regulators), and its performance directly determines the conductive stability and structural reliability of electronic devices, which are indispensable in key links such as electrode lead-out and interlayer conduction of electronic paper display screens. In current electronic paper display screen production, the mainstream conductive silver adhesive is still mainly based on thermosetting epoxy systems and solvent-based acrylic systems, but both types of products have significant technical defects: Although thermosetting conductive silver adhesive has high conductivity and bonding strength, curing needs to be carried out at a high temperature for a long time. On the one hand, high temperature easily leads to the agglomeration of electrophoretic particles inside the electronic paper and the deformation of the flexible substrate, causing display residual images or device failure. On the other hand, long-time curing significantly reduces the production line rhythm, leading to an increase in unit production cost, which is difficult to adapt to the large-scale and high-efficiency production needs of electronic paper display screens. Although solvent-based conductive silver adhesive can be cured at room temperature, it needs to rely on solvent evaporation to achieve resin crosslinking, which emits VOCs and does not meet environmental protection requirements. After solvent evaporation, pores are easily formed inside the adhesive layer, leading to fluctuations in conductivity, and the adhesive strength is low, which easily causes cracking of the adhesive layer and conductive failure in the application scenarios of electronic paper display screens, significantly shortening the service life.

[0003] To solve the above problems, the industry has gradually explored the application of UV curing technology in conductive silver adhesive. UV curing technology rapidly crosslinks the resin system through ultraviolet light, has the advantages of low temperature, rapidness, and solvent-free, and can perfectly avoid the defects of thermosetting and solvent-based silver adhesives, becoming the preferred direction of conductive bonding materials for electronic paper display screens. However, existing UV conductive silver adhesives still have two technical bottlenecks: Insufficient adhesion: the interfacial adhesion between the UV-cured resin and the FPL film and ITO conductive glass is weak, and the bonding strength after curing is generally low, which cannot meet the assembly reliability requirements of electronic paper display screens; Poor conductive stability: to ensure the UV curing rate, a high proportion of active monomers needs to be introduced into the UV resin system, leading to a decrease in silver powder dispersibility (easy to form agglomerates), which reduces the conductivity and significantly fluctuates the conductivity under temperature and humidity cycling conditions, affecting the long-term conductive stability of display devices. Therefore, developing a UV conductive silver adhesive with high bonding strength, excellent electrical conductivity and reliable low-temperature rapid curing performance has become the key to breaking the bottleneck of electronic paper display screen production and promoting its application in intelligent display, Internet of Things terminal and other fields. SUMMARY

[0004] The application provides a graphene-reinforced UV conductive silver adhesive for display, and aims to achieve the following purposes: First, by scientifically regulating the formula system, the silver adhesive has the core performance suitable for the production scene of the electronic paper display screen: sufficient operable time at room temperature, meeting the process adjustment requirements in the production process; at the same time, excellent dispensing performance is ensured to avoid problems such as stringing and tailing during dispensing, and the dispensing precision is ensured; and rapid curing is realized relying on the UV curing characteristics, the production efficiency is improved, and after curing, the FPL film and the ITO conductive glass can form good adhesive performance, ensuring the assembly reliability of the electronic paper display screen. Second, modified graphene is introduced into the formula system, the quantum tunneling effect at the interface between graphene and silver particles is utilized to promote electron transition, breaking the limitation of traditional silver adhesive relying on the accumulation of silver particles for conduction, and thus the overall electrical conductivity of the silver adhesive is significantly improved, meeting the use requirements of the electronic paper display screen for stable conductive connection and low resistance.

[0005] To achieve the purposes, the application adopts the following technical solutions: A graphene-reinforced UV conductive silver adhesive for display, wherein the components contained by the adhesive are composed of the following components by weight: two-functional polyurethane acrylate 6-10 parts, epoxy acrylate 1-3 parts, UV monomer 8-12 parts, defoaming agent 0.02-0.04 parts, photoinitiator 0.5-1 part, dispersing agent 0.02-0.4 parts, modified graphene 0.5-1 part, and silver powder 75-85 parts.

[0006] Further, the two-functional polyurethane acrylate is low-viscosity two-functional aliphatic polyurethane acrylate, and the viscosity is not more than 20,000 mPa.s. The low-viscosity two-functional polyurethane acrylate can enhance the flow performance of the system after filling silver powder and graphene.

[0007] Further, the epoxy acrylate is modified bisphenol A epoxy acrylate. Adding a small amount of the component can improve the adhesion of the adhesive to the substrate.

[0008] Further, the UV monomer can be selected from monofunctional acrylate (such as isobornyl methacrylate IBOMA, 2-ethylhexyl methacrylate EHMA) or bifunctional acrylate (such as dipropylene glycol diacrylate DPGDA, 1,6-hexanediol diacrylate HDDA), and the viscosity is not greater than 100 mPa.s. The active UV monomer can participate in the curing reaction of the UV resin, and the lower viscosity can enhance the flow performance of the glue.

[0009] Further, the photoinitiator is selected from at least one of photoinitiator TPO, photoinitiator 184 and photoinitiator 1173.

[0010] Further, the defoaming agent is a silicone-based polymer, and BYK-530, BYK-535 and BYK-1796 of BYK can be selected.

[0011] Further, the dispersant can be BYK-111 of BYK.

[0012] Further, the modified graphene is silane coupling agent modified graphene, and the preparation method is as follows: according to the mass ratio of KH560, ethanol and deionized water is 1:6-10:1-2, KH560 is dissolved in the mixed solvent of ethanol and deionized water, the pH is adjusted to 4-5 with acetic acid, and the active silicon alcohol group (Si-OH) is generated after hydrolysis at room temperature for 30-60 minutes; then graphene is added, and the silicon alcohol group of KH560 reacts with the hydroxyl group (-OH) on the surface of graphene to form a covalent bond (Si-O-C) under stirring at 60-80℃ for 6-8 hours; after the reaction is completed, water and ethanol are removed by vacuum, the product is transferred and filtered, washed to neutral, and dried to obtain modified graphene. The mass ratio of KH560 to graphene is 1:4-6.

[0013] Further, the silver powder is flaky silver powder with a particle size of less than 2 microns.

[0014] The preparation method of the graphene-reinforced UV conductive silver paste for display according to the application comprises the following steps: First, the photoinitiator and the UV monomer are mixed and stirred at 50-70℃ until clear and transparent, then the temperature is adjusted to 30-40℃, the epoxy acrylate and the bifunctional polyurethane acrylate are added and stirred uniformly, then the defoaming agent, the modified graphene and the dispersant are added and stirred uniformly, the three-roll mill is used for grinding to 1-3 microns, the silver powder is added and stirred uniformly, cooled to room temperature, filtered, and packaged to obtain the graphene-reinforced UV conductive silver paste for display.

[0015] Compared with the prior art, the application has the following beneficial effects: 1. In view of the special requirements of electronic paper display screen for "low temperature, high efficiency and reliable" conductive bonding, the present application realizes the breakthrough of technical effect through the targeted design of the formula system: based on the UV curing characteristics, it can be quickly cured without high temperature, which fundamentally avoids the damage of internal components of electronic paper caused by high temperature of traditional heat-curable silver adhesive, and perfectly adapts to the thermal sensitivity material characteristics of electronic paper; at the same time, through the synergistic matching of low viscosity two-functional polyurethane acrylate and UV monomer, combined with the dispersion and regulation of dispersing agent to the filler, the silver adhesive before curing has excellent dispensing performance, and after curing, it maintains moderate viscosity, which not only meets the process requirements of continuous production, but also forms stable bonding with FPL film and ITO conductive glass, solves the application defects of existing UV conductive silver adhesive "insufficient bonding force and dispensing problems", realizes the dual goals of "process adaptation + reliable performance" of electronic paper conductive bonding. 2. The present application is not simply adding graphene, but covalently modifying graphene with silane coupling agent (KH560), so that the modified graphene can form a close interface with silver powder. On the one hand, the quantum tunneling effect of graphene and silver particle interface is used to promote electron transition, which significantly improves the overall conductivity and breaks the limitation of traditional silver adhesive relying on silver powder accumulation for conduction; on the other hand, the two-dimensional sheet structure of modified graphene can fill the gap between silver powder, which not only reduces the amount of silver powder (compared with traditional UV silver adhesive without graphene), but also ensures or even improves the conductive performance, which not only reduces the cost of raw materials, but also avoids the problems of viscosity increase and dispensing performance decline caused by excessive silver powder. 3. Compared with two types of mainstream traditional silver adhesive, the present application has the following advantages: compared with heat-curable conductive silver adhesive, it does not need high temperature and long time curing, and the curing speed is greatly improved, and through the "silver - graphene" synergistic conductive system, the contact resistance is lower, which not only improves the production efficiency, but also guarantees the conductive stability, and completely solves the defects of heat-curable silver adhesive "high temperature damaging components and low curing efficiency"; compared with solvent type conductive silver adhesive, the solvent free UV curing system is adopted, which avoids the VOCs pollution caused by solvent volatilization from the source, and is more green and environmental protection, and relying on the synergistic effect of resin matrix and modified graphene, the bonding performance is much better than that of solvent type silver adhesive (without the problems of glue layer porosity and poor bonding force caused by solvent volatilization), which can meet the long-term use requirements of electronic paper display screen, and realize the environmental protection and high performance replacement of solvent type silver adhesive. DETAILED DESCRIPTION

[0016] In order to make the above objectives, characteristics and advantages of the present application more apparent, a specific embodiment of the present application is described in detail below. The following is merely an example and illustration of the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or replace them with similar ways, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

[0017] Example 1 (reference formula) In this example, 10 g of KH560 was first dissolved in a mixed solvent of 80 g of ethanol and 10 g of deionized water, 0.5 mL of acetic acid was added to adjust the pH to 4-5, and hydrolysis was carried out at room temperature for 50 minutes; 50 g of graphene (particle size less than 10 microns) was added to the hydrolyzed KH560, and stirring was carried out at 80°C for 6 hours. After the reaction was completed, water and ethanol were removed under vacuum, the product was transferred and filtered, washed to neutral, and dried in an oven at 80°C for 12 hours to obtain modified graphene.

[0018] In this example, the graphene-reinforced UV conductive silver paste for display was prepared according to the following steps: First, 0.59 parts of photoinitiator TPO and 9.87 parts of UV monomer IBOMA (viscosity 12 mPa·s) were mixed and stirred at 60°C until clear and transparent, then the temperature was adjusted to 30°C, 1.97 parts of epoxy acrylate (Changxing 623-100) and 7.9 parts of two-functional polyurethane acrylate (Changxing 61857, viscosity 8600 mPa·s) were added and dispersed at a speed of 800 r / min for 30 minutes, 0.04 parts of silicone-based defoaming agent (BYK-530) and 0.59 parts of modified graphene were added and continued to be dispersed at a speed of 800 r / min for 30 minutes, then a three-roll mill was used to grind the liquid to about 2 µm, followed by adding 78.99 parts of silver powder (China Ship Huanggang Noble Metal, YY-35, particle size 2 µm) and stirring uniformly, the obtained material was filtered through a 200-mesh screen and then packaged, to obtain the graphene-reinforced UV conductive silver paste for display.

[0019] Example 2 (adjustment of the amount of modified graphene) In this example, the graphene-reinforced UV conductive silver paste for display was prepared according to the same method as in Example 1, except that the amount of modified graphene was adjusted to 0.8 parts.

[0020] Example 3 (adjustment of the resin compounding ratio) In this example, the graphene-reinforced UV conductive silver paste for display was prepared according to the same method as in Example 1, except that 1.97 parts of epoxy acrylate and 7.9 parts of two-functional polyurethane acrylate were replaced by 2.47 parts of epoxy acrylate and 7.4 parts of two-functional polyurethane acrylate.

[0021] Example 4 (UV monomer type adjustment) This example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that the UV monomer was replaced from monofunctional IBOMA to an equal amount of difunctional DPGDA (viscosity 14 mPa-s).

[0022] Comparative Example 1 (no modified graphene) To verify the effect of modified graphene on conductivity, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that 0 parts of modified graphene was added.

[0023] Comparative Example 2 (unmodified graphene) To verify the effect of graphene modification on viscosity, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that 0.59 parts of unmodified graphene was added.

[0024] Comparative Example 3 (excessive amount of silver powder) To verify the effect of excessive amount of silver powder on viscosity and adhesion, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that 78.99 parts of silver powder was replaced with 85 parts of silver powder.

[0025] Comparative Example 4 (single resin system, no epoxy acrylate) To verify the effect of epoxy acrylate on adhesion, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that 1.97 parts of epoxy acrylate and 7.9 parts of two- functional polyurethane acrylate were replaced with 9.87 parts of two-functional polyurethane acrylate.

[0026] Comparative Example 5 (single resin system, no two-functional polyurethane acrylate) To verify the effect of two-functional polyurethane acrylate on adhesion, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that 1.97 parts of epoxy acrylate and 7.9 parts of two-functional polyurethane acrylate were replaced with 9.87 parts of epoxy acrylate.

[0027] Comparative Example 6 (modified graphene amount below lower limit) To verify the effect of insufficient amount of modified graphene on conductivity, this comparative example prepared graphene-reinforced display UV conductive silver paste by the same method as Example 1, with the only difference being that the amount of modified graphene was adjusted to 0.3 parts.

[0028] Comparative Example 7 (modified graphene amount above upper limit) To verify the effect of excess modified graphene on the conductivity, the comparative example was prepared by the same method as in Example 1, except that the amount of modified graphene was adjusted to 1.2 parts.

[0029] Comparative Example 8 (silver powder amount below the lower limit) To verify the effect of insufficient silver powder on the conductivity, the comparative example was prepared by the same method as in Comparative Example 1, except that the amount of modified graphene was adjusted to 70 parts.

[0030] Comparative Example 9 (commercially available UV conductive silver paste) To directly compare the performance differences between the present application and existing UV paste, the comparative example used a commercially available UV conductive silver paste for electronic paper (curing conditions: 395 nm LED lamp with 6000 mj / cm 2 ). Comparative Example 10 (commercially available thermosetting conductive silver paste) To compare the efficiency of UV curing and thermal curing, and low-temperature applicability, the comparative example used a commercially available imported thermosetting epoxy conductive silver paste (curing conditions: 70°C / 1 hour / 0.5 MPa).

[0031] Comparative Example 11 (commercially available solvent-based conductive silver paste) To compare the environmental friendliness and adhesion of the solvent-free system, the sample of the comparative example was a commercially available imported solvent-based acrylic conductive silver paste (curing conditions: 70°C / 1 hour / 0.5 MPa).

[0032] The UV conductive silver pastes prepared in the above examples and comparative examples were subjected to performance verification by the following test methods.

[0033] 1. Dispensing performance test The UV conductive silver paste to be tested was loaded into a dispensing machine, the dispensing pressure was set to 0.2 MPa, and the dispensing path in the conventional production was followed. After the test was completed, the glue point and dispensing track were observed: if there was no stringing or tailing phenomenon, the dispensing performance was determined to be qualified, marked as "OK"; if there was stringing or tailing, the dispensing performance was determined to be unqualified, marked as "NG".

[0034] 2. Viscosity test The cone and plate viscometer was used to test the viscosity of the UV conductive silver paste. During the test, the viscometer speed was set to 5 r / min, and the final viscosity value was recorded after the instrument reading was stable, which reflected the flow characteristics of the UV conductive silver paste.

[0035] 3. Resistance test First, the UV conductive silver adhesive was uniformly dispensed between the FPL film and the ITO conductive glass, with the thickness of the adhesive layer controlled at 40 pm; then the UV conductive silver adhesive was irradiated and cured using a 395 nm LED lamp at an energy of 6000 mj / cm 2 After curing, the contact resistance of the FPL film and the ITO conductive glass was tested using a multimeter.

[0036] 4. Adhesion test The same sample preparation method as the resistance test was used: first, the UV conductive silver adhesive was uniformly dispensed between the FPL film and the ITO conductive glass, with the thickness of the adhesive layer controlled at 40 pm; then the UV conductive silver adhesive was irradiated and cured using a 395 nm LED lamp at an energy of 6000 mj / cm 2 After curing, the sample was fixed on the clamps of the universal testing machine, and the peeling test was carried out at the set tensile rate (100 mm / min). The maximum force value when the FPL film and the ITO conductive glass separated was recorded as the adhesion test result of the silver adhesive.

[0037] 5. Humidity aging test First, the UV conductive silver adhesive was uniformly dispensed between the FPL film and the ITO conductive glass, with the thickness of the adhesive layer controlled at 40 pm; then the UV conductive silver adhesive was irradiated and cured using a 395 nm LED lamp at an energy of 6000 mj / cm 2 After curing, the sample was placed in a humidity aging oven (60℃ / 80RH) for a total of 500 hours. Every 250 hours, the contact resistance of the FPL film and the ITO conductive glass was tested using a multimeter; the sample was fixed on the clamps of the universal testing machine, and the peeling test was carried out at the set tensile rate (100 mm / min). The maximum force value when the FPL film and the ITO conductive glass separated was recorded as the adhesion test result of the silver adhesive.

[0038] The test results of the UV conductive silver adhesives prepared in the above examples and comparative examples are shown in the following table:

[0039] From the test results, it can be seen that the graphene-reinforced UV conductive silver adhesive provided by the application has moderate viscosity and excellent dispensing performance; the contact resistance of the FPL film and the ITO conductive glass is low and the adhesive force is strong; after 500 hours of hygrothermal aging test, the FPL film and the ITO conductive glass still have good contact resistance and strong adhesive force (Examples 1, 2, 3 and 4); the UV conductive silver adhesive without graphene has high contact resistance to the FPL film and the ITO conductive glass (Comparative Example 1); the UV conductive silver adhesive with unmodified graphene has large viscosity and poor dispensing performance (Comparative Example 2). When the amount of modified graphene is large, the viscosity of the system increases, and the problem of stringing in the dispensing process is prone to occur (Comparative Example 7); when the amount of modified graphene is small, the effective conductive synergistic effect between the graphene and the silver powder cannot be formed, and the contact resistance of the UV conductive silver adhesive to the FPL film and the ITO conductive glass is high (Comparative Example 6); when the amount of silver powder is large, the viscosity increases and the content of resin in the system decreases, and the adhesive force of the UV conductive silver adhesive to the FPL film and the ITO conductive glass decreases (Comparative Example 3). When the amount of silver powder is small, the UV conductive silver adhesive cannot form a good conductive path in the system, and therefore the contact resistance of the prepared UV conductive silver adhesive is high (Comparative Example 8); when the amount of epoxy acrylate is too high, the viscosity of the UV conductive silver adhesive is large and the dispensing performance is poor (Comparative Example 5); when the amount of epoxy acrylate is insufficient, the adhesive force of the UV conductive silver adhesive to the substrate is low (Comparative Example 4); therefore, the proportion of epoxy acrylate needs to be controlled within a suitable range.

[0040] In the application, the dispersibility of graphene in resin is improved by modifying the graphene, the electron transition is promoted by quantum tunneling effect at the interface between graphene and silver particles, the overall conductivity is improved, and therefore the contact resistance of the FPL film and the ITO conductive glass is significantly reduced. On the other hand, the addition of modified graphene reduces the amount of silver powder, and avoids the problem of insufficient adhesive force caused by excessive silver powder (Comparative Example 9). Compared with the thermosetting conductive silver adhesive, the UV conductive silver adhesive provided by the application has the characteristics of fast curing speed and low contact resistance (Comparative Example 10). Compared with the solvent-based conductive silver adhesive, the UV conductive silver adhesive provided by the application is solvent-free, more environmentally friendly, and has good adhesive performance (Comparative Example 11).

[0041] The above only describes the preferred embodiments of the application, and it should be pointed out that those skilled in the art can make corresponding adjustments and improvements without departing from the principles of the application, and these adjustments and improvements should also be considered within the protection scope of the application.

Claims

1. A UV conductive silver paste for graphene enhanced display, characterized in that: The raw materials contained in the UV conductive silver paste are composed of 6-10 parts of difunctional polyurethane acrylate, 1-3 parts of epoxy acrylate, 8-12 parts of UV monomer, 0.02-0.04 parts of defoaming agent, 0.5-1 parts of photoinitiator, 0.02-0.4 parts of dispersant, 0.5-1 parts of modified graphene, and 75-85 parts of silver powder in parts by weight.

2. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The viscosity of the difunctional polyurethane acrylate is not greater than 20,000 mPa.s.

3. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The epoxy acrylate is modified bisphenol A epoxy acrylate.

4. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The UV monomer is selected from at least one of isobornyl methacrylate IBOMA, 2-ethylhexyl methacrylate EHMA, 1,6-hexanediol diacrylate HDDA and dipropylene glycol diacrylate DPGDA, and the viscosity of the UV monomer is no more than 100 mPa·s.

5. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The photoinitiator is selected from at least one of photoinitiator TPO, photoinitiator 184 and photoinitiator 1173.

6. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The dispersant is BYK-111; the defoaming agent is an organosilicon polymer.

7. The UV conductive silver paste for graphene-enhanced display according to claim 1, wherein: The modified graphene is silane coupling agent modified graphene, and the preparation method is as follows: KH560 is dissolved in a mixed solvent of ethanol and deionized water, the pH is adjusted to 4-5 with acetic acid, and hydrolyzed at room temperature for 30-60 minutes to generate active silanol groups; then graphene is added, and stirred at 60-80°C for 6-8 hours to allow the silanol groups of KH560 to undergo a condensation reaction with hydroxyl groups on the surface of the graphene to form covalent bonds; after the reaction is completed, water and ethanol are removed in vacuo, the product is transferred, filtered, washed to neutrality, and dried to obtain the modified graphene; wherein the mass ratio of KH560 to graphene is 1:4-6.

8. A method for preparing the UV conductive silver paste for graphene enhanced display according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: firstly, mixing a photoinitiator and a UV monomer at 50°C to 70°C and stirring until the mixture becomes clear and transparent; then adjusting the temperature to 30°C to 40°C; adding epoxy acrylate and difunctional polyurethane acrylate and stirring evenly; then adding a defoamer, modified graphene and a dispersant and stirring evenly; grinding the mixture to 1-3µm using a three-roll mill; adding silver powder and stirring evenly; filtering and packaging the mixture to obtain UV conductive silver paste for graphene enhanced display.

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