Preparation method of single-layer touch sheet

Abstract

The invention belongs to the technical field of touch screens, and particularly relates to a preparation method of a single-layer touch sheet, which comprises the following steps: providing a substrate layer; forming a conductive metal layer; performing first etching and second etching on the conductive metal layer, and respectively forming a metal bridge and a metal wire in the visible area and the non-visible area; forming an insulating layer; performing etching treatment on the insulating layer to form a first hollow gap and a second hollow gap in the visible area and the non-visible area respectively; forming a conductive layer; carrying out etching treatment on the conductive layer to form a silver paste wire for providing a touch point; attaching a glass cover plate; and connecting with the flexible circuit board to form a finished product of the single-layer touch sheet. The single-layer touch sheet prepared through the method is good in conductivity, stable in finished product and small in damage to equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of touch screens, and in particular relates to a method for preparing a single-layer touch sheet. Background Art

[0002] Touch panels are interactive devices that improve the user experience of human-computer interfaces and are widely used in various electronic products.

[0003] Compared with double-layer touch sheets, single-layer touch sheets are lighter and thinner, and therefore are more favored by electronic equipment manufacturers.

[0004] After the touch panel is used for a long time, various problems will occur, such as slow interactive response and poor conductivity. At the same time, during the production process of the touch panel, the high temperature generated by the etching process and sputtering problems will also cause damage to the equipment and affect the service life of the production equipment.

[0005] In order to reduce damage to the equipment, some existing technologies have provided an isolation film and an insulating layer between the substrate layer and the conductive layer to isolate the sputtering problem caused by high-temperature etching. However, this method is cumbersome and will increase the thickness of the finished product.

[0006] In addition, in order to extend the service life of the touch panel, some other technologies use a yellow light exposure process to expose the etched silver paste traces to yellow light to increase the performance stability of the finished product, but this does not fundamentally improve the conductive performance of the finished product. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a single-layer touch sheet with good conductivity, simple preparation and low equipment loss, so as to solve the problems of poor conductivity, poor stability and easy sputtering of products in the prior art.

[0008] In order to achieve the above object, the present invention provides the following technical solutions: A method for preparing a single-layer touch sheet comprises the following steps: Step S1: providing a substrate layer; Step S2: forming a conductive metal layer on the substrate layer; Step S3: performing first etching and second etching on the conductive metal layer using a first etching solution and a second etching solution respectively, to form a metal bridge and a metal trace in the visible area and the non-visible area respectively; Step S4: forming an insulating layer on the conductive metal layer; Step S5: etching the insulating layer to form a first hollow gap and a second hollow gap in the visible area and the non-visible area respectively; Step S6: printing a conductive silver paste on the insulating layer to form a conductive layer; Step S7: etching the conductive layer to form silver paste traces providing touch points; Among them, silver paste routing includes intermittent silver paste routing and continuous silver paste routing; The intermittent silver paste wiring is laid and formed on the visible area and the non-visible area, connected to the metal wiring through the second hollow gap, and connected to the metal bridge through the first hollow gap; Continuous silver paste wiring is laid and formed on the visible area and the non-visible area, and is connected to the metal wiring through the second hollow gap; Step S8: attaching a glass cover plate to the conductive layer by optical adhesive; Step S9: connecting the metal traces leaking out of the second hollow gap to the flexible circuit board to form a finished single-layer touch sheet.

[0009] Wherein, in step S3, the components of the first etching solution include a mixed acid, a corrosion inhibitor and a solvent water; the components of the second etching solution include a mixed acid, a corrosion inhibitor and a solvent water; Furthermore, the contents of the mixed acid and the corrosion inhibitor in the second etching solution are both less than those in the mixed acid in the first etching solution.

[0010] Wherein, in step S3, each liter of the first etching solution contains 400-600 mL of mixed acid and 50-100 g of corrosion inhibitor, and the remainder is water; Each liter of the second etching solution contains 300-500 mL of mixed acid and 30-50 g of corrosion inhibitor, and the balance is water.

[0011] Wherein, the corrosion inhibitor in the first etching solution is sodium nitrate, copper sulfate, polydimethylsiloxane or cyclohexyl nitrite; The corrosion inhibitor in the second etching solution is sodium nitrate or copper sulfate.

[0012] Wherein, in step S6, the conductive silver paste includes a mixed organic carrier, a conductive powder and a mixed solvent.

[0013] Wherein, the mixed solvent includes tetrahydrofuran, polypropylene glycol glycidyl ether and polyurethane.

[0014] Wherein, the mixed solvent also includes terpineol or butyl carbitol acetate.

[0015] Wherein, the mixed organic carrier includes epoxy resin and polyester resin.

[0016] Wherein, the epoxy resin is tripalmitin or resorcinol diglycidyl ether; and the polyester resin is polyethylene resin or PEGA resin.

[0017] Each liter of conductive silver paste contains 400-500 g of mixed organic carrier, 40-60 g of conductive powder and 500-800 mL of mixed solvent.

[0018] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. In order to avoid side etching and improve the qualified rate of products, the present invention changes the existing one-time etching process into two-time etching, and provides two etching solutions: during the first etching, the acid concentration is relatively high, and rough etching is performed; during the second etching, the acid concentration is relatively low, and more precise fine etching is performed, thereby improving the qualified rate of products.

[0019] 2. In view of the drift and flying pen phenomena existing in the existing touch sheet etching process, the present invention attempts to increase the content of mixed acid in the acidic etching solution to increase the etching intensity, ensure one-step etching for each etching position, and avoid the drift and flying pen phenomena; at the same time, in order to avoid the impact of high-intensity etching process on the substrate layer or conductive metal material, resulting in sputtering damage to production equipment, the present invention adds a corrosion inhibitor on the basis of increasing the content of mixed acid in the acidic etching solution, so as to further ensure the stability of etching on the basis of ensuring the etching intensity and avoid the occurrence of sputtering; based on this, the present invention screens from common corrosion inhibitors to verify the effect, and selects corrosion inhibitors suitable for the etching stage for the first etching solution and the second etching solution respectively.

[0020] 3. In order to improve the stability of the final product, the present invention strictly screens the solvents of the conductive silver paste, combines the characteristics of a large number of solvents, comprehensively considers many factors such as solubility, boiling point, volatility, viscosity, stability, flexibility, etc., and after preliminary screening, tetrahydrofuran, polypropylene glycol glycidyl ether and polyurethane are determined as the necessary components of the conductive silver paste mixed solvent to ensure the excellent stability of the finished product.

[0021] 4. On the basis of determining the mixed solvent, the present invention considers the conductive uniformity of the finished product with respect to the organic carrier, determines the epoxy resin and polyester resin that can evenly distribute the conductive powder in the conductive silver paste, and further attempts to prepare the organic carrier with a mixture of the two, thereby further reducing the b value and haze value of the finished product. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The various substances appearing below in the present invention come from the following sources: Resorcinol diglycidyl ether: purchased from Shenyang Southeast Chemical Research Institute, with an epoxy value of 0.76-0.89 mol / 100g; Polyethylene resin: purchased from Qilu Branch of Sinopec Corporation.

[0024] Polydimethylsiloxane: purchased from Merck official website, product number 63148-62-9; Bisphenol A epoxy resin: purchased from Merck official website, product number 31185, molecular weight 340; Graphite powder: purchased from Merck official website, product number 928046; Polypropylene glycol glycidyl ether: purchased from Merck official website, product number 26142-30-3; Polyurethane: purchased from Merck official website, product number 91367; Terpineol: purchased from Merck official website, product number 86480; Tripalmitin: purchased from Merck official website, product number T8127; Triacetin: purchased from Merck official website, product number 1.03000; Hydroxymethyl polystyrene resin: purchased from Merck official website, product number 499226; PEGA resin: purchased from Merck official website, product number 76153; Rosin: purchased from Merck official website, product number 60895.

[0025] 1. Screening of etching solution The first inventive point of the present invention is that, in view of the drift, flying pen and sputtering phenomena existing in the existing touch panel etching process, a corrosion inhibitor is added on the basis of increasing the content of mixed acid in the acidic etching solution. On the one hand, the increase in the content of mixed acid can provide a strong etching force to avoid the drift and flying pen phenomena. On the other hand, the addition of the corrosion inhibitor can ensure stable etching and avoid damage to the equipment by metal sputtering. Furthermore, two etching solutions are provided to perform two etchings respectively, the first time for rough etching, and the second time with a reduced amount of corrosion inhibitor and mixed acid added, so as to perform more precise fine etching, avoid side etching, and improve the product qualification rate.

[0026] Example 1 Step S1: providing a substrate layer. In the present invention, the substrate layer uses a quartz material as a substrate. In practical applications, different substrate layers can be selected according to the adaptability of the touch panel to the application occasion. The selection of the specific material is a conventional technical means used by those skilled in the art, and the present invention does not limit it here. Step S2: providing a conductive metal layer on the substrate layer. In this embodiment, the conductive metal layer is made of ITO. In actual implementation, any metal or metal oxide conductor material with conductive function may be selected, and the present invention is not limited thereto. Step S3: Prepare a first etching solution and a second etching solution, and the content of each component is as follows: Per liter of the first etching solution: 200 mL of hydrochloric acid, 100 mL of hydrofluoric acid, 150 mL of nitric acid, 80 g of corrosion inhibitor - sodium nitrate, and the balance is water; Per liter of the second etching solution: 150 mL of hydrochloric acid, 80 mL of hydrofluoric acid, 100 mL of nitric acid, 40 g of corrosion inhibitor - copper sulfate, and the balance is water; The conductive metal layer is subjected to first etching and second etching respectively by using the prepared first etching solution and the second etching solution to observe whether there is drift, flying pen or sputtering.

[0027] Embodiment 2-9 The difference from Example 1 is that the composition of the corrosion inhibitor is different, as shown in the following table: Table 1: Selection of corrosion inhibitor components in Examples 1-9

[0028] The phenomena observed in the two etching processes of Examples 1-9 are shown in the following table: Table 2: Observation of etching process phenomena in Examples 1-9

[0029] Combined with the contents of Table 2, it can be seen that by increasing the content of the mixed acid in the first etching solution and the second etching solution, stronger and more targeted etching can be achieved. During the entire etching process, no drift or flying pen occurs, ensuring the qualified rate of the product. Regarding the selection of corrosion inhibitors, ferrous sulfate cannot meet the needs of the first etching and the second etching, so it is abandoned. Regarding the first etching, sodium nitrate, copper sulfate, polydimethylsiloxane and cyclohexyl nitrite can all meet its needs. However, regarding the second etching, only sodium nitrate and copper sulfate can meet its needs, which may be due to the small amount of corrosion inhibitor added in the second etching solution.

[0030] Therefore, when preparing the first etching solution, sodium nitrate, copper sulfate, polydimethylsiloxane or cyclohexyl nitrite is selected as the corrosion inhibitor, and when preparing the second etching solution, sodium nitrate or copper sulfate is selected as the corrosion inhibitor. In this way, splashing can be avoided during both the first etching and the second etching processes, thereby avoiding corrosion to the equipment.

[0031] 2. Screening of Conductive Silver Paste Based on the requirements of the performance of the touch panel product, in terms of the solvent selection of the conductive silver paste, the present invention provides a mixed solvent including the following essential components: Tetrahydrofuran: provides good solubility, suitable boiling point, and inertness to react with other organic substances, which prevents the conductive silver paste from volatilizing during the laying or etching process, while ensuring the conductive silver paste has suitable viscosity, facilitating the laying and molding of the conductive silver paste; Polypropylene glycol glycidyl ether: It also provides the conductive silver paste with a suitable boiling point and stability. At the same time, polypropylene glycol glycidyl ether has excellent physical compatibility with the resin, which can ensure that the resin drives the conductive powder to be evenly distributed in the mixed solvent carrier, providing excellent conductive performance; Polyurethane: provides hydrogen bonding groups and flexibility to the conductive silver paste, so that the prepared product has better anti-interference and folding properties.

[0032] On this basis, pinene alcohol or butyl carbitol acetate can be selectively added to the mixed solvent.

[0033] Each liter of conductive silver paste contains 400-500 g of mixed organic carrier, 40-60 g of conductive powder and 500-550 mL of mixed solvent.

[0034] In the mixed solvent, the volume ratio of tetrahydrofuran, polypropylene glycol glycidyl ether and polyurethane is: (18-25): (1-3): 1; terpineol / butyl carbitol acetate is added to the conductive silver paste to a predetermined volume; The conductive powder includes graphite powder and silver powder, and the mass ratio of graphite powder to silver powder is (8-10):1; the particle size of graphite powder is 60-90 nanometers, and the particle size of silver powder is 10-20um. The silver powder can be attached to the surface of graphite powder and evenly distributed in the mixed solvent along with the organic carrier to avoid powder adhesion and agglomeration.

[0035] Example 10 Steps S1-S3 are the same as those in Example 1; Step S4: forming an insulating layer on the conductive metal layer, wherein the insulating layer material is selected from a transparent material, such as polymethyl methacrylate; Step S5: etching the insulating layer to form a first hollow gap and a second hollow gap in the visible area and the non-visible area respectively; Step S6: printing a conductive silver paste on the insulating layer to form a conductive layer; The substances and ingredients contained in each liter of conductive silver paste are as follows: 480g bisphenol A epoxy resin, 54g graphite powder (60nm particle size), 6g silver powder (15um particle size), 440mL tetrahydrofuran, 60mL polypropylene glycol glycidyl ether, 20mL polyurethane, 20mL pinene alcohol; Step S7: etching the conductive layer to form silver paste traces providing touch points; Among them, silver paste routing includes intermittent silver paste routing and continuous silver paste routing; The intermittent silver paste wiring is laid and formed on the visible area and the non-visible area, connected to the metal wiring through the second hollow gap, and connected to the metal bridge through the first hollow gap; Continuous silver paste wiring is laid and formed on the visible area and the non-visible area, and is connected to the metal wiring through the second hollow gap; Step S8: attaching a glass cover plate to the conductive layer by optical adhesive; Step S9: connecting the metal traces leaking out of the second hollow gap to the flexible circuit board to form a finished single-layer touch sheet.

[0036] Embodiment 11 The difference from Example 10 is that in the conductive silver paste, the organic carrier is resorcinol diglycidyl ether; Example 12 The difference from Example 10 is that in the conductive silver paste, the organic carrier is tripalmitin; Embodiment 13 The difference from Example 10 is that in the conductive silver paste, the organic carrier is triacetin; Embodiment 14 The difference from Example 10 is that in the conductive silver paste, the organic carrier is polyethylene resin; Embodiment 15 The difference from Example 10 is that in the conductive silver paste, the organic carrier is hydroxymethyl polystyrene resin; Example 16 The difference from Example 10 is that in the conductive silver paste, the organic carrier is poly [acryloyl-bis (aminopropyl) polyethylene glycol], hereinafter referred to as PEGA resin; Embodiment 17 The difference from Example 10 is that in the conductive silver paste, the organic carrier is rosin.

[0037] Embodiment 18 The difference from Example 10 is that in the conductive silver paste, the organic carrier is a mixture of resorcinol diglycidyl ether and polyethylene resin, and the mass ratio of the two is 1:1; Embodiment 19 The difference from Example 10 is that in the conductive silver paste, the organic carrier is a mixture of tripalmitin and polyethylene resin, and the mass ratio of the two is 1:1; Embodiment 20 The difference from Example 10 is that in the conductive silver paste, the organic carrier is a mixture of resorcinol diglycidyl ether and PEGA resin, and the mass ratio of the two is 1:1; Embodiment 21 The difference from Example 10 is that in the conductive silver paste, the organic carrier is a mixture of tripalmitin and PEGA resin, and the mass ratio of the two is 1:1.

[0038] The b value and haze value of the finished products prepared in Examples 10-20 are measured, as shown in the following table: Table 3: Performance measurement values ​​of finished products of Examples 11-21

[0039] Bisphenol A epoxy resin, resorcinol diglycidyl ether, tripalmitin and triacetin are all epoxy resins, polyethylene resin, hydroxymethyl polystyrene resin, PEGA resin and rosin are all polyester resins. The present invention selects the above four epoxy resins and polyester resins respectively, and verifies the performance of the products prepared after using them as conductive silver paste one by one. The data proves that resorcinol diglycidyl ether and tripalmitin in epoxy resin, and polyethylene resin and PEGA resin in polyester resin are used as organic carriers to promote the uniform distribution of conductive powder in the mixed solvent. Conductive silver paste is prepared using them as organic carriers. Finally, the b value and haze value of the finished monolayer film are lower than those of other organic carriers. In addition, on this basis, the present invention attempts to select epoxy resin and polyester resin to mix to provide an organic carrier, proving that the mixed organic carrier can further reduce the b value and haze value of the finished product.

[0040] 3. Effect Verification A single-layer touch sheet was prepared by using Examples 22-24, and the differences from Example 21 are shown in the following table: Table 4: Preparation parameters of Examples 21-24

[0041] Comparative Example 1: The difference from Example 21 is that the contents of the components in the first etching solution are: 100 ml of hydrochloric acid, 50 ml of hydrofluoric acid, and 80 ml of nitric acid; The contents of the components in the second etching solution are: 70 ml of hydrochloric acid, 40 ml of hydrofluoric acid, and 50 ml of nitric acid.

[0042] Comparative Example 2: The difference from Example 21 is that the conductive silver paste does not contain tetrahydrofuran and the content of pineneol is 560 mL.

[0043] Comparative Example 3: The difference from Example 21 is that the conductive silver paste does not contain polypropylene glycol glycidyl ether, and the content of pineol is 180 mL.

[0044] Comparative Example 4: The difference from Example 21 is that the conductive silver paste does not contain polyurethane and the content of pineneol is 140 mL.

[0045] Table 5: Effect verification

[0046] In Table 5, whether the performance parameters meet the requirements specifically involves: linearity test, short circuit test, open circuit test and flatness test. If all of the above tests are qualified, it is considered to meet the requirements, and if any of the above tests are unqualified, it is considered to not meet the requirements. Combining the results of Examples 21-24 and Comparative Example 1, it can be seen that in the present invention, by increasing the content of mixed acid in the etching solution during the etching process of the conductive metal layer and adding a corrosion inhibitor, the drift, flying pen and sputtering phenomena occurring during the etching process are solved. When the content of the mixed acid is insufficient, drift and flying pen phenomena will occur.

[0047] Combining the results of Examples 21-24 and Comparative Examples 2-3, it can be seen that: based on the careful screening of conductive silver paste solvents, the present invention has screened out a suitable organic carrier through experiments, which can evenly distribute the conductive powder in the conductive silver paste, so that the b value and haze value of the finished product reach the lowest. If either the solvent or the organic carrier does not meet the requirements, the lowest b value and haze value cannot be achieved; and when the necessary components in the solvent are missing, the required reaction inertness, viscosity, boiling point, flexibility, etc. cannot be given to the finished product, resulting in poor stability of the finished product.

[0048] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a single-layer touch sheet, characterized in that: The steps include: Step S1: providing a substrate layer; Step S2: forming a conductive metal layer on the substrate layer; Step S3: performing first etching and second etching on the conductive metal layer using a first etching solution and a second etching solution respectively, to form a metal bridge and a metal trace in the visible area and the non-visible area respectively; Step S4: forming an insulating layer on the conductive metal layer; Step S5: etching the insulating layer to form a first hollow gap and a second hollow gap in the visible area and the non-visible area respectively; Step S6: printing a conductive silver paste on the insulating layer to form a conductive layer; Step S7: etching the conductive layer to form silver paste traces providing touch points; Among them, silver paste routing includes intermittent silver paste routing and continuous silver paste routing; The intermittent silver paste wiring is laid and formed on the visible area and the non-visible area, connected to the metal wiring through the second hollow gap, and connected to the metal bridge through the first hollow gap; Continuous silver paste wiring is laid and formed on the visible area and the non-visible area, and is connected to the metal wiring through the second hollow gap; Step S8: attaching a glass cover plate to the conductive layer by optical adhesive; Step S9: connecting the metal traces leaking out of the second hollow gap to the flexible circuit board to form a finished single-layer touch sheet.

2. The method for preparing a single-layer touch sheet according to claim 1, characterized in that: In step S3, the first etching solution comprises a mixed acid, a corrosion inhibitor and a solvent water; the second etching solution comprises a mixed acid, a corrosion inhibitor and a solvent water; Furthermore, the contents of the mixed acid and the corrosion inhibitor in the second etching solution are both less than those in the mixed acid in the first etching solution.

3. The method for preparing a single-layer touch sheet according to claim 2, characterized in that: In step S3, each liter of the first etching solution contains 400-600 mL of mixed acid and 50-100 g of corrosion inhibitor, and the remainder is water; Each liter of the second etching solution contains 300-500 mL of mixed acid and 30-50 g of corrosion inhibitor, and the balance is water.

4. The method for preparing a single-layer touch sheet according to claim 2, characterized in that: The corrosion inhibitor in the first etching solution is sodium nitrate, copper sulfate, polydimethylsiloxane or cyclohexyl nitrite; The corrosion inhibitor in the second etching solution is sodium nitrate or copper sulfate.

5. The method for preparing a single-layer touch sheet according to claim 1, characterized in that: In the step S6, the conductive silver paste includes a mixed organic carrier, a conductive powder and a mixed solvent.

6. The method for preparing a single-layer touch sheet according to claim 5, characterized in that: The mixed solvent includes tetrahydrofuran, polypropylene glycol glycidyl ether and polyurethane.

7. The method for preparing a single-layer touch sheet according to claim 6, characterized in that: The mixed solvent also includes terpineol or butyl carbitol acetate.

8. The method for preparing a single-layer touch sheet according to claim 5, characterized in that: The mixed organic carrier includes epoxy resin and polyester resin.

9. The method for preparing a single-layer touch sheet according to claim 8, characterized in that: The epoxy resin is tripalmitin or resorcinol diglycidyl ether; the polyester resin is polyethylene resin or PEGA resin.

10. The method for preparing a single-layer touch sheet according to claim 5, characterized in that: Each liter of conductive silver paste contains 400-500 g of mixed organic carrier, 40-60 g of conductive powder and 500-800 mL of mixed solvent.

Images