Special halogen-free conductive silver paste for laser etching of touch screen and preparation method of special halogen-free conductive silver paste

Abstract

The invention provides halogen-free conductive silver paste special for touch screen laser etching and a preparation method of the halogen-free conductive silver paste, and relates to the technical field of electronic paste. The halogen-free conductive silver paste special for touch screen laser etching comprises the following raw materials in parts by weight: 75-85 parts of conductive silver powder, 8-12 parts of a polymer bonding substance, 4-7 parts of a solvent, 1.5-3 parts of a curing agent, 1-3 parts of an auxiliary agent and 0.1-0.3 part of a laser absorbent. Halogen-containing resin is replaced by bisphenol A epoxy resin, acrylic resin and aldehyde ketone resin, and halogen-free design is adopted; through the synergistic effect of the nano silver powder and the laser absorbent, the laser absorbent effectively absorbs laser energy and converts the laser energy into energy of other forms, the edge burr rate is obviously reduced, and the etching line width is enabled to be lt; the square resistance value fluctuation of the line after laser etching is lt; and 5%, the high-precision requirement of the touch screen is met.

Description

Technical Field

[0001] This invention relates to the field of electronic paste technology, and in particular to a halogen-free conductive silver paste for laser etching of touch screens and its preparation method. Background Technology

[0002] The touch screen industry has extremely high requirements for the precision of conductive lines. Traditional processes (such as screen printing) are difficult to meet the manufacturing needs of micron-level lines. Laser etching technology uses a high-energy laser beam to locally heat the silver paste film, achieving micron-level or even nanon-level etching, which significantly improves the precision of the lines.

[0003] Silver, as a metal with excellent electrical conductivity, is frequently used in various electronics industries. The rapid development of the electronics industry has driven the application of conductive pastes, a key basic material, making them widely used in thick-film integrated circuits, chip components, microwave devices, solar cells, and other microelectronic fields. To improve the competitiveness of electronic products, the industry requires conductive silver pastes to have high conductivity, high stability, and high efficiency.

[0004] However, traditional silver paste is prone to problems such as edge burrs and decreased conductivity during laser etching, and its halogen content can corrode laser equipment and shorten its lifespan.

[0005] Therefore, it is necessary to provide a new halogen-free conductive silver paste for laser etching of touch screens and its preparation method to solve the above-mentioned technical problems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a halogen-free conductive silver paste for laser etching of touch screens and its preparation method.

[0007] The halogen-free conductive silver paste for laser etching of touch screens provided by this invention comprises the following raw materials in parts by weight: 75-85 parts conductive silver powder, 8-12 parts polymer binder, 4-7 parts solvent, 1.5-3 parts curing agent, 1-3 parts additives, and 0.1-0.3 parts laser absorber.

[0008] Furthermore, the conductive silver powder is flake-shaped silver powder with a particle size of 0.5-5μm.

[0009] Furthermore, the polymer binder is one or more of bisphenol A type epoxy resin, acrylic resin, and aldehyde-ketone resin.

[0010] Furthermore, the solvent is selected as butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0011] Furthermore, the curing agent is phthalic anhydride.

[0012] Furthermore, the additive is one or more of the following: reactive diluent, adhesion promoter, and anti-settling agent.

[0013] A method for preparing a halogen-free conductive silver paste for laser etching of touch screens and the preparation method thereof, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 0.5-5μm; Step 2, Premixing the polymer binder: Add the polymer binder to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1, and stir at 60-80℃ for 1-2 hours until completely dissolved to form a transparent solution; Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4: Slurry mixing: The flake silver powder and the transparent solution will be mixed using a dual planetary mixer to obtain a mixed slurry; Step 5, Addition of additives and curing agents: Add the additives and laser absorbers to the mixed slurry from Step 4. Stir for 15-20 minutes after each addition of additives. Slowly add the pretreated phthalic anhydride to the mixed slurry to obtain conductive silver paste.

[0014] Furthermore, in step one, after screening the flake silver powder, the flake silver powder is placed in a vacuum drying oven at 80-100℃ and dried for 1-3 hours to remove adsorbed moisture.

[0015] Furthermore, in step four, the pretreated flake silver powder is gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture is stirred for 10 minutes at a stirring speed of 500-800 rpm. Then, the mixture is degassed under a vacuum of -0.09 MPa for 30 minutes to obtain a mixed slurry.

[0016] Furthermore, in step five, phthalic anhydride is mixed and stirred with the mixed slurry at a temperature of 25°C for 30 minutes.

[0017] Compared with related technologies, the halogen-free conductive silver paste for laser etching of touch screens and its preparation method provided by the present invention have the following beneficial effects: 1. This invention replaces halogen-containing resins with bisphenol A type epoxy resin, acrylic resin, and aldehyde-ketone resin, adopts a halogen-free design, eliminates the risk of toxic gas release, and uses compound resins with significantly better performance than single resin systems, especially in terms of adhesion and storage stability. The solvent ratio and curing agent type phthalic anhydride have a significant impact on drying time and reactivity. At the same time, the drying temperature and stirring speed must be strictly controlled within a reasonable range to avoid moisture residue or the introduction of air bubbles. Anti-settling agent is crucial for storage stability; omitting it will easily cause the slurry to settle and separate.

[0018] 2. This invention utilizes the synergistic effect of nano-silver powder and laser absorber. The laser absorber effectively absorbs laser energy and converts it into other forms of energy, significantly reducing the edge burr rate, resulting in an etched linewidth of <20μm and a line resistance fluctuation of <5% after laser etching, thus meeting the high precision requirements of touch screens. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments. Example 1

[0020] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 75 parts flake silver powder, 8 parts polymer binder, 4 parts solvent, 1.5 parts phthalic anhydride, 1 part reactive diluent, and 0.1 parts laser absorber.

[0021] It should be noted that the conductive silver powder has a particle size of 0.5 μm.

[0022] It should be noted that the polymer binder includes bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin in a weight ratio of 5:3:2.

[0023] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0024] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 0.5μm, and then place the flake silver powder in an 80℃ vacuum drying oven to dry for 1 hour to remove adsorbed moisture; Step 2, Premixing the polymer binder: Bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin are mixed to obtain a mixed resin. The mixed resin is added to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1. The mixture is stirred at 60°C for 1 hour until completely dissolved to form a transparent solution. Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 500 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agent: Add the additives and laser absorber to the mixed slurry from Step 4. After adding the additives, stir for 15 minutes. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste. Example 2

[0025] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 80 parts of flake silver powder, 10 parts of polymer binder, 5 parts of solvent, 2 parts of phthalic anhydride, 2 parts of reactive diluent, and 0.2 parts of laser absorber.

[0026] It should be noted that the conductive silver powder has a particle size of 3μm.

[0027] It should be noted that the polymer binder includes bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin in a weight ratio of 5:3:2.

[0028] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0029] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 3μm, and then place the flake silver powder in a 90℃ vacuum drying oven to dry for 2 hours to remove adsorbed moisture; Step 2, Premixing the polymer binder: Bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin are mixed to obtain a mixed resin. The mixed resin is added to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1. The mixture is stirred at 90°C for 1.5 hours until completely dissolved to form a transparent solution. Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 600 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agents: Add the additives and laser absorber to the mixed slurry from Step 4. After adding the additives, stir for 18 minutes. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste. Example 3

[0030] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 85 parts of flake silver powder, 12 parts of polymer binder, 7 parts of solvent, 3 parts of phthalic anhydride, 3 parts of reactive diluent, and 0.3 parts of laser absorber.

[0031] It should be noted that the conductive silver powder has a particle size of 5μm.

[0032] It should be noted that the polymer binder includes bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin in a weight ratio of 5:3:2.

[0033] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0034] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 5μm, and then place the flake silver powder in a vacuum drying oven at 100℃ for 3 hours to remove adsorbed moisture. Step 2, Premixing the polymer binder: Bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin are mixed to obtain a mixed resin. The mixed resin is added to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1. The mixture is stirred at 80°C for 2 hours until completely dissolved to form a transparent solution. Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 800 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agent: Add the additives and laser absorber to the mixed slurry from Step 4. After adding the additives, stir for 20 minutes. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste. Example 4

[0035] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 75 parts flake silver powder, 8 parts bisphenol A type epoxy resin, 4 parts solvent, 1.5 parts phthalic anhydride, 1 part additive, and 0.1 parts laser absorber.

[0036] It should be noted that the conductive silver powder has a particle size of 0.5 μm.

[0037] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0038] The additives include an active diluent, an adhesion promoter, and an anti-settling agent in a weight ratio of 5:3:2.

[0039] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 0.5μm, and then place the flake silver powder in an 80℃ vacuum drying oven to dry for 1 hour to remove adsorbed moisture; Step 2, Premixing the polymer binder: Add bisphenol A type epoxy resin to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1, and stir at 60°C for 1 hour until completely dissolved to form a transparent solution; Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 500 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agents: Add the additives and laser absorbers to the mixed slurry from Step 4. Stir for 15 minutes after each addition. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste. Example 5

[0040] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 80 parts of flake silver powder, 10 parts of bisphenol A type epoxy resin, 5 parts of solvent, 2 parts of phthalic anhydride, 2 parts of additives, and 0.2 parts of laser absorber.

[0041] It should be noted that the conductive silver powder has a particle size of 3μm.

[0042] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0043] The additives include an active diluent, an adhesion promoter, and an anti-settling agent in a weight ratio of 5:3:2.

[0044] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 3μm, and then place the flake silver powder in a 90℃ vacuum drying oven to dry for 2 hours to remove adsorbed moisture; Step 2, Premixing the polymer binder: Add bisphenol A epoxy resin to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1, and stir at 90°C for 1-2 hours until completely dissolved to form a transparent solution; Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 600 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agents: Add the additives and laser absorbers to the mixed slurry from Step 4. Stir for 18 minutes after each addition. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste. Example 6

[0045] In the specific implementation process, the halogen-free touch screen laser etching special conductive silver paste includes the following raw materials in parts by weight: 85 parts of flake silver powder, 12 parts of bisphenol A type epoxy resin, 7 parts of solvent, 3 parts of phthalic anhydride, 3 parts of additives, and 0.3 parts of laser absorber.

[0046] It should be noted that the conductive silver powder has a particle size of 5μm.

[0047] It should be noted that the solvents used are butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:1.

[0048] The additives include an active diluent, an adhesion promoter, and an anti-settling agent in a weight ratio of 5:3:2.

[0049] A method for preparing halogen-free conductive silver paste for laser etching of touch screens, wherein the raw materials for preparing the conductive silver paste are in parts by weight. The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 5μm, and then place the flake silver powder in a vacuum drying oven at 100℃ for 3 hours to remove adsorbed moisture. Step 2, Premixing the polymer binder: Add bisphenol A type epoxy resin to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1, and stir at 80°C for 2 hours until completely dissolved to form a transparent solution; Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4, Slurry Mixing: The flake silver powder and the transparent solution will be mixed using a double planetary mixer. The pretreated flake silver powder will be gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture will be stirred for 10 minutes at a stirring speed of 800 rpm. Then, the mixture will be degassed under a vacuum of -0.09 MPa for 30 minutes to obtain the mixed slurry. Step 5, Addition of additives and curing agents: Add the additives and laser absorbers to the mixed slurry from Step 4. Stir for 20 minutes after each addition. Slowly add the pretreated phthalic anhydride to the mixed slurry and stir for 30 minutes at 25°C to obtain conductive silver paste.

[0050] Comparative Example 1 In practical implementation, the halogen-free conductive silver paste for touch screen laser etching includes the following raw materials in parts by weight: 75 parts flake silver powder, 8 parts polymer binder, 4 parts solvent, 1.5 parts phthalic anhydride, 1 part reactive diluent, 0.1 parts laser absorber, and the conductive silver powder has a particle size of 10 μm.

[0051] Comparative Example 2 In practical implementation, the halogen-free conductive silver paste for touch screen laser etching includes the following raw materials in parts by weight: 75 parts flake silver powder, 8 parts polymer binder, 4 parts solvent, 1.5 parts phthalic anhydride, 1 part reactive diluent, 0.1 parts laser absorber, and the conductive silver powder has a particle size of 0.1 μm.

[0052] Comparative Example 3 The raw materials are the same as in Example 1. The difference is that after each addition of 10% by weight of flake silver powder, the mixture is stirred for 10 minutes at a stirring speed of 1000 rpm.

[0053] Comparative Example 4 Unlike the raw materials in Example 4, no anti-settling agent was added.

[0054] Comparative Example 5 Unlike the raw materials in Example 1, no laser absorber was added.

[0055] Experiment 1 The adhesion of the conductive silver pastes obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was measured according to GB / T 9286 "Cross-cut test of paint and varnish films". The resistivity of the conductive silver paste was calculated using a resistivity meter. The drying time was measured according to GB1728-1979 "Determination of drying time of paint film and putty film". The storage stability of the obtained conductive silver pastes was tested at an ambient temperature of 60°C. The specific test results are shown in the table below:

[0056] As shown in the table above, Comparative Example 1 suffers from increased contact resistance and poor storage stability due to excessively coarse conductive silver powder particles. Comparative Example 2 suffers from poor dispersibility and significantly increased resistivity due to excessively fine conductive silver powder particles. Comparative Example 3 suffers from poor adhesion due to air bubbles introduced by high-speed stirring. Comparative Example 4 suffers from precipitation during storage and poor storage stability. Both excessively fine and excessively coarse particle sizes significantly reduce conductivity and storage stability. The performance of the compound resin (Examples 1 to 6) is significantly better than that of the single resin system (Examples 4 to 6), especially in terms of adhesion and storage stability. The solvent ratio and the type of curing agent, phthalic anhydride, have a significant impact on drying time and reactivity. At the same time, the drying temperature and stirring speed must be strictly controlled within a reasonable range to avoid moisture residue or air bubble introduction. The anti-settling agent is crucial for storage stability; omitting it makes the slurry prone to sedimentation and stratification.

[0057] Experiment 2 For the conductive silver pastes obtained in Examples 1 to 6 and Comparative Example 1, the etching linewidth was obtained by 3D profile measurement using a white light interferometer. A profile curve was generated by linear scanning using a profilometer. The edge burr rate was measured by reading the vertical distance between the burr apex and the conductive silver paste surface. The sheet resistance fluctuation was measured using the four-probe method. The specific test results are shown in the table below:

[0058] As shown in the table above, Comparative Example 5, due to the absence of a laser absorber, resulted in a higher edge burr rate during laser etching, leading to a wider etching linewidth and greater fluctuations in the line resistance after laser etching. In contrast, Examples 1 to 6, through the synergistic effect of nano-silver powder and laser absorber, significantly reduced the edge burr rate, achieving an etching linewidth of <20μm and a line resistance fluctuation of <5% after laser etching, thus meeting the high precision requirements of touchscreens.

[0059] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention, and no markings in the claims should be construed as limiting the scope of the claims.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A halogen-free conductive silver paste for laser etching of touch screens, characterized in that, The raw materials include the following parts by weight: 75-85 parts conductive silver powder, 8-12 parts polymer binder, 4-7 parts solvent, 1.5-3 parts curing agent, 1-3 parts additives, and 0.1-0.3 parts laser absorber.

2. The halogen-free conductive silver paste for touchscreen laser etching according to claim 1, characterized in that, The conductive silver powder is in the form of flakes with a particle size of 0.5-5μm.

3. The halogen-free conductive silver paste for touchscreen laser etching according to claim 1, characterized in that, The polymer binder is one or more of bisphenol A type epoxy resin, acrylic resin and aldehyde-ketone resin.

4. The halogen-free conductive silver paste for laser etching of touch screens according to claim 1, characterized in that, The solvent is selected from butyl acetate and isopropanol, and the weight ratio of butyl acetate to isopropanol is 3:

1.

5. The halogen-free conductive silver paste for touchscreen laser etching according to claim 1, characterized in that, The curing agent is phthalic anhydride.

6. The halogen-free conductive silver paste for touchscreen laser etching according to claim 1, characterized in that, The additive is one or more of the following: reactive diluent, adhesion promoter, and anti-settling agent.

7. A method for preparing a halogen-free conductive silver paste for laser etching of touch screens, used to prepare the halogen-free conductive silver paste for laser etching of touch screens according to any one of claims 1-6, characterized in that, The raw materials for preparing the conductive silver paste are in parts by weight; The specific preparation method includes the following steps: Step 1: Pretreatment of conductive silver powder: Use a laser particle size analyzer to screen flake silver powder with a particle size of 0.5-5μm; Step 2, Premixing the polymer binder: Add the polymer binder to a solvent in which butyl acetate and isopropanol are mixed in a weight ratio of 3:1, and stir at 60-80℃ for 1-2 hours until completely dissolved to form a transparent solution; Step 3, Curing agent pretreatment: Pulverize phthalic anhydride to a particle size of less than 50μm; Step 4: Slurry mixing: The flake silver powder and the transparent solution will be mixed using a dual planetary mixer to obtain a mixed slurry; Step 5, Addition of additives and curing agents: Add the additives and laser absorbers to the mixed slurry from Step 4. Stir for 15-20 minutes after each addition of additives. Slowly add the pretreated phthalic anhydride to the mixed slurry to obtain conductive silver paste.

8. The method for preparing halogen-free conductive silver paste for laser etching of touch screens according to claim 7, characterized in that, In step one, after screening the flake silver powder, the flake silver powder is placed in a vacuum drying oven at 80-100℃ and dried for 1-3 hours to remove adsorbed moisture.

9. The method for preparing halogen-free conductive silver paste for laser etching of touch screens according to claim 7, characterized in that, In step four, the pretreated flake silver powder is gradually added to the transparent solution. After each addition of 10% by weight of flake silver powder, the mixture is stirred for 10 minutes at a stirring speed of 500-800 rpm. Then, the mixture is degassed under a vacuum of -0.09 MPa for 30 minutes to obtain a mixed slurry.

10. The method for preparing halogen-free conductive silver paste for laser etching of touch screens according to claim 7, characterized in that, In step five, phthalic anhydride and the mixed slurry are mixed and stirred at 25°C for 30 minutes.

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