A preparation method of a touch sensor for reducing the visibility of a metal grid and the touch sensor prepared thereby

Abstract

The present invention belongs to the technical field of roll-to-roll metal grid addition process for touch sensors, and relates to a preparation method of a touch sensor for reducing the visibility of metal grids, comprising the steps of: S1. Double-sidedly coat a photoresist underlayer on a transparent substrate, and form a pattern driving layer through exposure and development; S2. Chemically deposit a layer of palladium metal for blackening on the pattern driving layer to form a first blackening layer with a thickness of 50-100 nm; S3. Deposit copper metal for conduction on the first blackening layer in step S2 to form a metal grid with a thickness of 400-1000 nm; S4. On the metal grid, replace the metal of the metal grid in S3 with palladium metal for blackening through a chemical reaction to form a second blackening layer with a thickness of 50-100 nm. The present invention simultaneously coats uniform blackening layers of the same type on both surfaces of the metal grid, so that the two surfaces of the touch sensor have the same color system visually, maintaining the consistency of visibility and greatly reducing its visibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of roll-to-roll metal grid addition process for touch sensors, and more specifically, relates to a method for preparing a touch sensor that reduces the visibility of metal grids. Background Art

[0002] With the application and gradual popularization of touch, more and more devices need to use touch functions, and at the same time, the requirements for touch sensors or touch-sensitive screens are getting higher and higher. The traditional indium tin oxide (ITO) process is gradually being replaced by the metal grid technology with high sensitivity and low impedance. In the current mainstream roll-to-roll metal grid addition process, the metal grids are mainly copper-based metal grids and silver-based metal grids. Since copper has a low cost and excellent conductivity, it has become the preferred material for the metal grid technology. However, copper metal is not only opaque but also reflects light. In a lighted environment, the metal grids in the touch sensor will reflect light, resulting in the appearance visual effect of the metal grid sensor. Therefore, it is necessary to reduce the visibility of the copper metal grid.

[0003] In the existing roll-to-roll metal grid addition process for touch sensors, such as Figure 1 , the substrate used in the copper metal grid technology is a transparent thin film material, that is, transparent substrate 1. Metal grids 2 are respectively plated on both sides of transparent substrate 1. Metal grids 2 are respectively TX - transmitting electrodes and RX - receiving electrodes, and are distributed on both sides of transparent substrate 1. When the user views the touch sensor head-on, not only can they see the metal grid 2 of the TX - transmitting electrode on one side, but also the metal grid 2 of the RX - receiving electrode on the other side, as well as the transparent pattern driving layer 5 formed by coating photoresist and catalyst on transparent substrate 1 and then exposing and developing.

[0004] In order to reduce the visibility of the metal grid 2, the prior art usually performs a blackening treatment on the surface of the copper metal grid to form a blackening layer 6. The commonly used blackening treatment method is to first plate the copper metal grid, and then oxidize and blacken or selenium blacken the surface of the copper metal grid. The surface oxidation blackening of the metal grid is to oxidize the copper surface of the copper metal grid to form black copper oxide on the surface, and rely on the black copper oxide to achieve the effect of reducing the visibility of the copper metal; the surface selenium blackening of the metal grid is to form dark blue copper selenide on the surface of the copper metal grid by soaking in a selenium-containing solution; in order to reduce the reflectivity and visibility of the metal grid 2, however, for the metal grid 2 of the TX - transmitting electrode and the metal grid 2 of the RX - receiving electrode on the back of the transparent material and the photoresist coated on the surface of the transparent material, in the existing roll - to - roll metal grid addition process, it is impossible to make the colors of the metal grids on both sides of the touch sensor exactly the same without color difference, resulting in the visibility effect of the copper metal grid screen not reaching the optimal state. Therefore, there is an urgent need to improve the roll - to - roll metal grid addition process to make the front and back have the same color system without color difference visually, so as to reduce the visibility of the metal grid 2. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide a preparation method of a touch sensor for reducing the visibility of a metal grid; this method is provided with uniform and the same metal blackening layers with a specific thickness on both the upper and lower surfaces of the metal grid, so as to overcome the problem that when observing the metal grid of the touch sensor from one side, the metal grids on both sides of the substrate have exactly the same color system without color difference, and further reduce the reflectivity and visibility of the metal grid.

[0006] Another object of the present invention is to provide a touch sensor prepared by the above method.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of a touch sensor for reducing the visibility of a metal grid includes the following steps:

[0009] S1. Double - side coat a photoresist underlayer on a transparent substrate, and form a pattern driving layer through exposure irradiation and development.

[0010] S2. Chemically deposit a layer of palladium metal for blackening on the pattern driving layer to form a first blackening layer with a thickness of 50 - 100 nm.

[0011] S3. Chemically deposit a layer of copper metal on the first blackening layer in step S2 to form a metal grid with a thickness of 400 - 1000 nm.

[0012] S4. On the metal grid, the metal surface of the metal grid in S3 is replaced by a metal for blackening through a chemical reaction to form a second blackening layer with a thickness of 50 - 100 nm.

[0013] In this preparation method, before forming the metal grid, a first blackening layer of palladium metal with a thickness of 50 - 100 nm is plated on the pattern driving layer, and after plating a metal copper with a thickness of 400 - 1000 nm, the same second blackening layer of palladium metal is formed by surface replacement again. This method improves the roll-to-roll metal grid manufacturing process, realizes reducing the brightness and visibility of the metal grid on both sides of the metal grid, greatly reduces the color difference of the blackening layer, and has a simple preparation process.

[0014] Furthermore, the first blackening layer and the second blackening layer have the same thickness.

[0015] The present invention discovers through experiments that when the thicknesses of the first blackening layer and the second blackening layer are controlled within a certain range, a better effect of reducing visibility can be achieved. If the thickness of the blackening layer is too high, the deposited blackening layer will gradually show a metallic color, and the shiny blackening layer will cause an increase in the brightness of the metal grid and a deterioration in visibility. Different thicknesses of the blackening layer will cause a color difference between the TX - transmitting electrode on one side of the touch sensor and the RX receiving electrode on the other side, resulting in the inability to achieve the effect of reducing the visibility of the metal grid.

[0016] Furthermore, for the electroless plating in step S2, the composition of the solution used and the reaction conditions are as follows:

[0017] Solution composition: 1 - 3 g / L soluble palladium salt, 4 - 6 g / L hypophosphite, 14 - 18 g / L complexing agent, 150 - 200 ml / L weak base, 0.5 - 1.0 g / L dispersant; Reaction conditions: pH value 6 - 8, temperature 55 - 60 °C.

[0018] This electroless plating of palladium utilizes a chemical redox reaction. Among them, the soluble palladium salt provides the palladium ions required for the redox reaction, and sodium hypophosphite is used as the reducing agent. Under the action of the catalyst, a redox reaction occurs, and the palladium ions are reduced to palladium metal. The complexing agent can refine the crystallization of palladium to obtain a dense palladium layer, thereby providing a stable blackening layer. The weak base provides a weakly alkaline environment for this reaction. The main factors affecting the palladium deposition rate are the concentration of palladium ions and the temperature of the plating solution. As the concentration of palladium ions increases and the temperature rises, the deposition rate gradually increases. However, in order to obtain a palladium blackening layer with fine crystallization, good bonding force, and stable performance, the palladium deposition rate needs to be controlled. This chemical reaction is: Pd 2+ +H 2 PO 2 2- →(catalyst)Pd.

[0019] In the present invention, the composition of the electroless plating solution can refer to the prior art. The soluble palladium salt can be common soluble palladium salts, such as palladium chloride, palladium sulfate, etc.; the hypophosphite can be common hypophosphites, such as sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, etc.; the complexing agent can be common complexing agents, such as ethylenediamine, disodium ethylenediaminetetraacetate, ammonium citrate, sodium citrate, etc.; the dispersant can be common dispersants, such as polyethylene glycol 200, polyethylene glycol 400, dispersant NNO, etc.; the weak base can be common ammonia water.

[0020] Furthermore, for the electroless plating in step S2, the composition of the electroless plating solution and the reaction conditions are as follows:

[0021] Solution composition: 1 - 3 g / L palladium chloride, 6 - 8 g / L ethylenediamine, 4 - 6 g / L sodium hypophosphite, 8 - 10 g / L disodium ethylenediaminetetraacetate, 150 - 200 ml / L ammonia water, 0.5 - 1.0 g / L polyethylene glycol 200; Reaction conditions: pH value 6 - 8, temperature 55 - 60 °C.

[0022] In addition, in the experiments of the present invention, it is found that the addition of the specific dispersant polyethylene glycol 200 can enable the above formula to prepare a blackening layer with more uniform distribution and chroma, thereby controlling to obtain a uniform blackening layer. However, if the addition of polyethylene glycol 200 is excessive, it will instead affect the reaction rate and further lead to a deterioration of the visualization effect.

[0023] Further, the composition of the solution used in the electroless plating in step S3 and the reaction conditions are as follows:

[0024] Solution composition: 5 - 10 g / L soluble copper salt, 15 - 20 g / L chelating agent, 6 - 10 g / L formaldehyde, 0.03 - 0.06 g / L stabilizer, 6 - 9 g / L strong base; Reaction conditions: temperature 38 - 40 °C.

[0025] In this process, electroless copper plating is through a chemical redox reaction to reduce copper ions in the solution to copper metal and deposit it on the blackened palladium surface of the circuit. Among them, the soluble copper salt mainly provides the copper ions required for the reaction. When the Cu 2+ concentration is high, the activity of the plating solution increases and the plating rate becomes faster. When the concentration is too high, the stability is very poor; when the Cu 2+ concentration is too low, the deposition rate is slow and the coating is dull. Since electroless copper plating is carried out in an alkaline solution, the chelating agent can form a stable complex with Cu, and the chelating agent plays a role in stabilizing the plating solution and refining the coating. The purpose of the stabilizer is to refine the crystals and stabilize the copper solution. The main role of the strong base is to provide the hydroxide ions required for the electroless copper plating reaction and create an alkaline environment. The chemical reaction is: Cu 2+ Complex + 2HCHO + 4OH - →Cu + 2HCOO - + 2H2 +2H 2 O + Complex, where the Pd catalyst triggers the reaction.

[0026] In the present invention, the composition of the electroless plating solution can refer to the prior art. The soluble copper salt can be a common soluble copper salt, such as copper sulfate pentahydrate, copper chloride, etc. The chelating agent can be a common chelating agent, such as Na 2 EDTA, tripotassium ethylenediaminetetraacetate, etc. The stabilizer can be a common stabilizer, such as potassium ferrocyanide, bipyridine, potassium selenocyanate, etc. The strong base can be a common strong base, such as sodium hydroxide, potassium hydroxide, etc.

[0027] Furthermore, for the electroless plating in step S3, the solution composition and reaction conditions are as follows:

[0028] Solution composition: 5 - 10 g / L copper sulfate pentahydrate, 15 - 20 g / L Na 2 EDTA, 6 - 10 g / L HCHO, 0.02 - 0.04 g / L bipyridine, 0.01 - 0.02 g / L potassium ferrocyanide, 6 - 9 g / L sodium hydroxide; Reaction conditions: temperature 38 - 40 °C.

[0029] Further, for the surface replacement in step S4, the solution composition and reaction conditions are as follows:

[0030] Solution composition: 0.5 - 2 g / L soluble palladium salt, 14 - 22 g / L complexing agent, 8 - 12 ml / L soluble organic acid, 0.1 - 0.5 g / L surfactant; Reaction conditions: pH value 5 - 6, temperature 49 - 51 °C.

[0031] This surface replacement palladium plating utilizes the fact that the standard electrode potential of copper is lower than that of palladium, and directly undergoes a surface replacement reaction between copper and palladium ions in the plating solution. Palladium chloride provides the palladium ions required for the electroless palladium plating reaction, formic acid provides the acidic environment required for the reaction, and sodium citrate and sodium acetate are complexing agents for palladium ions. Their role is to stabilize the electroless palladium plating solution system, control the speed of electroless palladium plating, refine the crystallization of the palladium layer, and obtain a dense and stable palladium blackening layer. In the experiments of the present invention, it was found that whether the second blackening layer is uniform also has a greater impact on the visibility of the metal grid. Sodium dodecyl sulfate, as a surfactant, reduces the surface tension of the solution, enabling the blackening solution to fully contact the copper grid, thereby making the blackening layer uniform; The chemical reaction is: Pd 2+ + Cu → Pd + Cu 2+ .

[0032] In the present invention, the solution composition for surface replacement in S4 can refer to the prior art. The soluble palladium salt can be a common soluble palladium salt, such as palladium chloride, palladium sulfate, etc.; the soluble organic acid can be a common organic acid, such as formic acid, acetic acid. The complexing agent can be a common complexing agent, such as ethylenediamine, disodium ethylenediaminetetraacetate, ammonium citrate, sodium citrate, etc.; the surfactant can be a common surfactant, such as sodium dodecylsulfonate, stearic acid, etc.

[0033] Furthermore, the replacement in step S4 is achieved by displacement plating with palladium, and the solution composition and reaction conditions used are as follows:

[0034] Solution composition: 0.5 - 2 g / L palladium chloride, 8 - 12 g / L sodium citrate, 6 - 10 g / L sodium acetate, 8 - 12 ml / L formic acid, 0.1 - 0.5 g / L sodium dodecylsulfonate; Reaction conditions: pH value 5 - 6, temperature 49 - 51 °C, time 180 - 300 s.

[0035] Further, the photoresist underlayer in step S1 further contains a catalyst or a catalyst is coated on the surface of the photoresist underlayer.

[0036] Furthermore, the catalyst is a palladium catalyst.

[0037] Preferably, the palladium catalyst is palladium oxide, palladium hydroxide, palladium chloride, palladium sulfate, diamminedichloropalladium, palladium metal nanoparticles.

[0038] Further, after the formation of the second blackening layer in step S4, it is necessary to perform water washing and drying.

[0039] Further, the transparent substrate is at least one of: polyethylene terephthalate, transparent polyimide, cycloolefin polymer, super retardation film, polycarbonate, polyethylene naphthalate, polymethyl methacrylate, triacetate fiber film, glass.

[0040] The present invention also claims protection for a touch sensor, comprising a transparent substrate, a pattern driving layer, a first blackening layer, a metal grid, and a second blackening layer; pattern driving layers are provided on both the upper and lower surfaces of the transparent substrate, and on the other surface of the pattern driving layer, there are successively arranged a first blackening layer, a metal grid, and a second blackening layer. The thickness of the first blackening layer is 50 - 100 nm, the thickness of the metal grid is 400 - 1000 nm, and the thickness of the second blackening layer is 50 - 100 nm.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The preparation method provided in the present invention adds a dark metal substrate with a specific thickness at the bottom of the metal grid, and at the same time uses the same type of blackening layer on the surface of the metal grid. In this way, no matter from the front or the back, visually, it is the same type of dark blackening layer, belonging to the same color system, maintaining the consistency of the grid visibility on the front and back, reducing the grid visibility, and improving the user experience; in the preparation method provided in the present invention, the thicknesses of the first blackening layer and the second blackening layer are controlled within a certain range and the thicknesses of the blackening layers are the same, which will further reduce the color difference between the TX - transmitting electrode on one side and the RX receiving electrode on the other side of the touch sensor, and reduce its visibility; in this method, disodium ethylenediaminetetraacetate and dispersant polyethylene glycol 200 are used for plating the first blackening layer, and sodium citrate and surfactant sodium dodecylsulfonate are used for the second blackening layer, which can ensure that when plating the first blackening layer and the second blackening layer, the coatings of the two blackening layers are relatively uniform, reducing the inability to reduce the visibility of the metal grid due to uneven coating; the preparation method provided in the present invention is to metallize the patterned part purposefully compared with the method of etching after full - metal sputtering; it saves more materials compared with the subtractive process. This method can be coated on both the RX and TX surfaces of the touch sensor at the same time, and has a simple preparation process, low production cost and high efficiency, and is suitable for large - area industrial production. Brief Description of the Drawings

[0043] Figure 1 FIG. is a schematic cross - sectional structure diagram of a touch sensor in the prior art.

[0044] Figure 2 FIG. is a schematic cross - sectional structure diagram of the touch sensor of the present invention.

[0045] Reference numerals in the figures: 1 is a transparent substrate; 2 is a metal grid; 3 is a first blackening layer; 4 is a second blackening layer; 5 is a pattern driving layer; 6 is a blackening layer. Detailed Embodiments

[0046] The following further illustrates the present invention with reference to the accompanying drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0047] Example 1

[0048] A preparation method of a touch sensor for reducing the visibility of a metal grid includes the following steps:

[0049] S1. A photoresist underlayer with palladium metal nanoparticles catalyst is spin - coated on both sides of the transparent substrate 1, and after ultraviolet light exposure and development, a pattern driving layer 5 is formed;

[0050] S2. On the pattern driving layer 5, electrolessly deposit a metal for blackening to form a first blackening layer 3. The metal of the first blackening layer 3 is palladium, and its thickness is 50 nm. For the electroless plating in step S2, the composition of the electroless plating solution is as follows: 1.5 g / L palladium chloride, 6 g / L ethylenediamine, 5 g / L sodium hypophosphite, 10 g / L disodium ethylenediaminetetraacetate, 150 ml / L ammonia water, 0.7 g / L polyethylene glycol 200. The reaction conditions are: pH value is 6, temperature is 60 °C, and time is 250 s.

[0051] S3. Electrolessly plate on the first blackening layer 3 in step S2 to form a copper metal grid with a thickness of 500 nm. For the electroless plating, the solution composition is: 7.5 g / L copper sulfate pentahydrate, 16 g / L Na 2 EDTA, 8 g / L HCHO, 0.03 g / L bipyridine, 0.01 g / L potassium ferrocyanide, 7 g / L sodium hydroxide. The reaction conditions are: temperature is 39 °C, and time is 90 s.

[0052] S4. On the metal grid 2, through a chemical reaction, replace the metal surface of the metal grid 2 in S3 with a metal for blackening to form a second blackening layer 4. The metal of the second blackening layer 4 is palladium, and its thickness is 50 nm. For the replacement, the solution composition is: 0.5 g / L palladium chloride, 10 g / L sodium citrate, 8 g / L sodium acetate, 10 ml / L formic acid, 0.3 g / L sodium dodecylsulfonate. The reaction conditions are: pH value is 5.5, time is 180 s, and temperature is 50 °C. Wash with water and dry to obtain Product Example 1.

[0053] The prepared touch sensor for reducing the visibility of the metal grid, such as Figure 2 , includes a transparent substrate 1, a pattern driving layer 5, a first blackening layer 3, a metal grid 2, and a second blackening layer 4. The pattern driving layer 5 is provided on both the upper and lower surfaces of the transparent substrate 1. On the other side of the pattern driving layer 5, there are sequentially arranged a first blackening layer 3, a metal grid 2, and a second blackening layer 4. The transparent substrate 1 is polyethylene terephthalate with a thickness of 50 μm. The first blackening layer 3 is made of palladium metal with a thickness of 50 nm, and the second blackening layer 4 is made of palladium metal with a thickness of 50 nm.

[0054] Example 2

[0055] A touch sensor for reducing the visibility of the metal grid, whose preparation method is the same as that of Example 1. The difference is that according to the different thicknesses of the plated metal, the plating time of the metal is changed to ensure that the thicknesses of the plated metals of the first blackening layer and the second blackening layer are both 60 nm, and Product Example 2 is obtained.

[0056] Example 3

[0057] A touch sensor for reducing the visibility of metal grids, the preparation method of which is the same as that of Example 1, except that the metal plating time is changed according to the different thicknesses of the plated metal, and the thicknesses of the plated metal of the first blackening layer and the second blackening layer are both ensured to be 80 nm, obtaining Product Example 3.

[0058] Example 4

[0059] A touch sensor for reducing the visibility of metal grids, the preparation method of which is the same as that of Example 1, except that the metal plating time is changed according to the different thicknesses of the plated metal, and the thicknesses of the plated metal of the first blackening layer and the second blackening layer are both ensured to be 100 nm, obtaining Product Example 4.

[0060] Example 5

[0061] A preparation method of a touch sensor for reducing the visibility of metal grids includes the following steps:

[0062] S1. A photoresist underlayer with palladium metal nanoparticles catalyst is double-sided coated on the transparent substrate 1, and after ultraviolet light exposure and development, a pattern driving layer 5 is formed.

[0063] S2. On the pattern driving layer 5, a metal for blackening is electrolessly plated to form a first blackening layer 3. The metal of the first blackening layer 3 is palladium, and the thickness is 70 nm. The solution composition: 2 g / L palladium chloride, 6 g / L ethylenediamine, 5 g / L sodium hypophosphite, 10 g / L disodium ethylenediaminetetraacetate, 200 ml / L ammonia water, 0.5 g / L polyethylene glycol 200; reaction conditions: pH value is 7, temperature is 60 °C, time is 241 s.

[0064] S3. On the first blackening layer 3 in step S2, copper metal for conduction is electrolessly plated to form a copper metal grid, and the thickness is 600 nm; for the electroless plating, the solution composition and reaction conditions are: 8 g / L copper sulfate pentahydrate, 16 g / L Na2EDTA, 8 g / L HCHO, 0.03 g / L bipyridine, 0.01 g / L potassium ferrocyanide, 7 g / L sodium hydroxide; reaction conditions: temperature is 39 °C, time is 95 s.

[0065] S4. On the metal grid 2, the metal surface of the metal grid 2 in S3 is replaced with a metal for blackening through a chemical reaction to form a second blackening layer 4. The metal of the second blackening layer 4 is palladium, and the thickness is 70 nm. The replacement is achieved by displacement plating with palladium, and the solution composition and reaction conditions used are as follows: 1 g / L palladium chloride, 8 g / L sodium citrate, 6 g / L sodium acetate, 10 ml / L formic acid, 0.3 g / L sodium dodecylsulfonate; reaction conditions: pH value is 5.5, time is 247 s, temperature is 49 °C. After washing and drying, Product Example 5 is obtained.

[0066] The prepared touch sensor with reduced visibility of the metal grid, such as Figure 2 , includes a transparent substrate 1, a pattern driving layer 5, a first blackening layer 3, a metal grid 2, and a second blackening layer 4; pattern driving layers 5 are provided on both the upper and lower surfaces of the transparent substrate 1, and on the other side of the pattern driving layer 5, there are successively arranged a first blackening layer 3, a metal grid 2, and a second blackening layer 4. The transparent substrate 1 is polyethylene terephthalate with a thickness of 50um. The first blackening layer 3 is made of palladium metal with a thickness of 70nm, the metal grid 2 is a copper metal grid with a thickness of 600nm when prepared, and the second blackening layer 4 is made of palladium metal with a thickness of 70nm.

[0067] Example 6

[0068] A preparation method of a touch sensor with reduced visibility of the metal grid includes the following steps:

[0069] S1. A photoresist underlayer with palladium metal nanoparticles catalyst is double-sided coated on the transparent substrate 1, and after ultraviolet light exposure and development, a pattern driving layer 5 is formed;

[0070] S2. On the pattern driving layer 5, a metal for blackening is electroless plated to form a first blackening layer 3. The metal of the first blackening layer 3 is palladium with a thickness of 80nm; its solution composition: 1.5g / L palladium chloride, 6g / L ethylenediamine, 6g / L sodium hypophosphite, 8g / L disodium ethylenediaminetetraacetate, 185ml / L ammonia water, 0.6g / L polyethylene glycol 200; reaction conditions: pH is 8, temperature is 58°C, time is 268s;

[0071] S3. On the first blackening layer 3 in step S2, a conductive metal copper is electroless plated to form a copper metal grid with a thickness of 800nm; for the electroless plating, its solution composition and reaction conditions are: 5g / L copper sulfate pentahydrate, 18g / L Na 2 EDTA, 9g / L HCHO, 0.03g / L bipyridine, 0.01g / L potassium ferrocyanide, 6g / L sodium hydroxide; reaction conditions: temperature is 39°C, time is 94s;

[0072] S4. On the metal grid 2, the metal surface of the metal grid 2 in S3 is replaced by a metal for blackening through a chemical reaction to form a second blackening layer 4. The metal of the second blackening layer 4 is palladium with a thickness of 80nm. The replacement is achieved by displacement plating with palladium, and the solution composition and reaction conditions used are as follows: 1.5g / L palladium chloride, 11g / L sodium citrate, 6g / L sodium acetate, 8ml / L formic acid, 0.5g / L sodium dodecylsulfonate; reaction conditions: pH value is 5.5, time is 246s, temperature is 48°C. After washing and drying, the product of Example 6 is obtained.

[0073] The prepared touch sensor with reduced visibility of the metal grid, such asFigure 2 , including a transparent substrate 1, a pattern driving layer 5, a first blackening layer 3, a metal grid 2, and a second blackening layer 4; pattern driving layers 5 are provided on both the upper and lower surfaces of the transparent substrate 1, and on the other side of the pattern driving layer 5, there are successively arranged a first blackening layer 3, a metal grid 2, and a second blackening layer 4. The transparent substrate 1 is polyethylene terephthalate with a thickness of 50 μm. The first blackening layer 3 is made of palladium metal with a thickness of 80 nm, the metal grid 2 is a copper metal grid with a thickness of 800 nm when prepared, and the second blackening layer 4 is made of palladium metal with a thickness of 80 nm.

[0074] Example 7

[0075] A preparation method of a touch sensor for reducing the visibility of a metal grid includes the following steps:

[0076] S1. A photoresist underlayer with palladium metal nanoparticles catalyst is coated on both sides of the transparent substrate 1, and after ultraviolet light exposure and development, a pattern driving layer 5 is formed;

[0077] S2. On the pattern driving layer 5, a metal for blackening is electrolessly plated to form a first blackening layer 3. The metal of the first blackening layer 3 is palladium with a thickness of 90 nm; the solution composition: 3 g / L palladium chloride, 7 g / L ethylenediamine, 6 g / L sodium hypophosphite, 10 g / L disodium ethylenediaminetetraacetate, 180 ml / L ammonia water, 0.7 g / L polyethylene glycol 200; reaction conditions: pH is 8, temperature is 60 °C, time is 210 s;

[0078] S3. On the first blackening layer 3 in step S2, copper metal for conduction is electrolessly plated to form a copper metal grid with a thickness of 700 nm; for the electroless plating, the solution composition and reaction conditions are: 10 g / L copper sulfate pentahydrate, 16 g / L Na 2 EDTA, 8 g / L HCHO, 0.03 g / L bipyridine, 0.01 g / L potassium ferrocyanide, 8.5 g / L sodium hydroxide; reaction conditions: temperature is 40 °C, time is 99 s;

[0079] S4. On the metal grid 2, through a chemical reaction, the metal surface of the metal grid 2 in S3 is replaced with a metal for blackening to form a second blackening layer 4. The metal of the second blackening layer 4 is palladium with a thickness of 90 nm. The replacement is achieved by displacement plating with palladium, and the solution composition and reaction conditions used are as follows: 2 g / L palladium chloride, 9 g / L sodium citrate, 8.6 g / L sodium acetate, 12 ml / L formic acid, 0.4 g / L sodium dodecylsulfonate; reaction conditions: pH value is 5, time is 272 s, temperature is 51 °C, and after washing and drying, the product of Example 7 is obtained.

[0080] The prepared touch sensor for reducing the visibility of the metal grid, such as Figure 2, including a transparent substrate 1, a pattern driving layer 5, a first blackening layer 3, a metal grid 2, and a second blackening layer 4; pattern driving layers 5 are provided on both the upper and lower surfaces of the transparent substrate 1, and on the other side of the pattern driving layer 5, there are successively arranged a first blackening layer 3, a metal grid 2, and a second blackening layer 4. The transparent substrate 1 is a transparent polyimide with a thickness of 50 μm. The first blackening layer 3 is made of palladium metal with a thickness of 90 nm, the metal grid 2 is a copper metal grid with a thickness of 1000 nm, and the second blackening layer 4 is made of palladium metal with a thickness of 90 nm.

[0081] Example 8

[0082] A touch sensor is prepared by referring to the preparation method in Example 1. The difference is that the time for plating the first blackening layer 3 is adjusted so that the first blackening layer has a thickness of 60 nm of palladium metal, and the time for plating the second blackening layer 4 is adjusted so that the second blackening layer 4 has a thickness of 90 nm of palladium metal, obtaining Product Example 8.

[0083] Example 9

[0084] A touch sensor is prepared by referring to the preparation method in Example 1. The differences are as follows:

[0085] In the electroless plating described in step S2, the disodium ethylenediaminetetraacetate in the electroless plating solution composition is 15 g / L, and the other solution compositions are the same as those in Example 1, controlling the thickness of the electroless plated first blackening layer 3 to be 50 nm; obtaining Product Example 9.

[0086] Example 10

[0087] A touch sensor is prepared by referring to the preparation method in Example 1. The differences are as follows:

[0088] In the electroless plating described in step S2, the disodium ethylenediaminetetraacetate in the electroless plating solution composition is 5 g / L, and the other solution compositions are the same as those in Example 1, controlling the thickness of the electroless plated first blackening layer 3 to be 50 nm; obtaining Product Example 10.

[0089] Example 11

[0090] A touch sensor is prepared by referring to the preparation method in Example 1. The differences are as follows:

[0091] In the electroless plating described in step S2, the electroless plating solution composition does not contain a dispersant, and the other solution compositions are the same as those in Example 1, controlling the thickness of the electroless plated first blackening layer 3 to be 50 nm; obtaining Product Example 11.

[0092] Example 12

[0093] A touch sensor is prepared by referring to the preparation method in Example 1. The differences are as follows:

[0094] In the electroless plating described in step S2, polyethylene glycol 200 in the solution composition of the electroless plating is replaced with polyethylene glycol 400 of the same concentration, and the other solution compositions are the same as those in Example 1. The thickness of the first blackening layer 3 formed by electroless plating is controlled to be 50 nm; Product Example 12 is obtained.

[0095] Example 13

[0096] A touch sensor is prepared with reference to the preparation method in Example 1, and the difference is:

[0097] In the electroless plating described in step S2, the concentration of polyethylene glycol 200 in the solution composition of the electroless plating is 2 g / L, and the other solution compositions are the same as those in Example 1. The thickness of the first blackening layer 3 formed by electroless plating is controlled to be 50 nm; Product Example 13 is obtained.

[0098] Example 14

[0099] A touch sensor is prepared with reference to the preparation method in Example 1, and the difference is:

[0100] In the electroless plating described in step S4, the concentration of sodium citrate in the solution composition of the electroless plating is 15 g / L, and the other solution compositions are the same as those in Example 1. The thickness of the second blackening layer 4 formed by electroless plating is controlled to be 50 nm; Product Example 14 is obtained.

[0101] Example 15

[0102] A touch sensor is prepared with reference to the preparation method in Example 1, and the difference is:

[0103] In the electroless plating described in step S4, the concentration of sodium citrate in the solution composition of the electroless plating is 6 g / L, and the other solution compositions are the same as those in Example 1. The thickness of the second blackening layer 4 formed by electroless plating is controlled to be 50 nm; Product Example 15 is obtained.

[0104] Example 16

[0105] A touch sensor is prepared with reference to the preparation method in Example 1, and the difference is:

[0106] In the electroless plating described in step S4, the solution composition of the electroless plating does not contain a surfactant, and the other solution compositions are the same as those in Example 1. The thickness of the second blackening layer 4 formed by controlling the electroless plating time is 50 nm; Product Example 16 is obtained.

[0107] Example 17

[0108] A touch sensor is prepared with reference to the preparation method in Example 1, and the difference is:

[0109] In the electroless plating described in step S4, sodium dodecyl sulfonate in the solution composition of the electroless plating is replaced with stearic acid of the same concentration, and the other solution compositions are the same as those in Example 1. The thickness of the second blackening layer 4 by electroless plating is controlled to be 50 nm; Product Example 17 is obtained.

[0110] Example 18

[0111] A touch sensor is prepared by referring to the preparation method in Example 1, and the difference is:

[0112] In the electroless plating described in step S4, the content of sodium dodecyl sulfonate in the solution composition of the electroless plating is 1 g / L, the other solution compositions are the same as those in Example 1, and the thickness of the second blackening layer 4 by electroless plating is controlled to be 50 nm; Product Example 18 is obtained.

[0113] Comparative Example 1

[0114] A touch sensor product has no first blackening layer 3 compared with that in Example 1, and the other parts are the same as those in Example 1; compared with the preparation method in Example 1, there is no step S2, that is, directly plating copper metal on the pattern driving layer 5 in step S1, then performing step S3, electroless plating copper, and then referring to the method in Example 1 for subsequent steps, displacing and plating palladium on the copper metal grid, washing with water and drying, to obtain Product Comparative Example 1.

[0115] Comparative Example 2

[0116] A touch sensor is prepared by referring to the preparation method in Example 1, and the difference is: there is no first blackening layer in step S2, that is, after plating copper on one side of the substrate, plating a layer of palladium metal, and then supplementing and plating a layer of palladium metal with the same thickness on the back of the copper grid line on the other side of the substrate, to obtain Product Comparative Example 2.

[0117] Comparative Example 3

[0118] A touch sensor product has no second blackening layer 4 compared with that in Example 1, and the other parts are the same as those in Example 1; compared with the preparation method in Example 1, there is no step S4, that is, washing with water and drying after electroless plating copper in step S3, and the other steps are the same as those in Example 1, to obtain Product Comparative Example 3.

[0119] Comparative Example 4

[0120] A touch sensor product has a second blackening layer of selenium blackening compared with that in Example 1, and the other parts, the first blackening layer and the electroless plating copper metal grid, are the same as those in Example 1. The formula of the selenium blackening aqueous solution is: 2 g / L selenium dioxide, 2 g / L polyethylene glycol 2000, 1 g / L phosphoric acid, 4 g / L sodium tripolyphosphate, and the process parameters are temperature 30 °C and time 50 s, to obtain Product Comparative Example 4.

[0121] Comparative Example 5

[0122] A touch sensor was prepared with reference to the preparation method in Example 1, with the difference that the time for plating the first blackening layer 3 was changed to make the thickness of palladium metal 40 nm, and the thickness of the second blackening layer 4 was 50 nm of palladium metal, to obtain Product Comparative Example 5.

[0123] Comparative Example 6

[0124] A touch sensor was prepared with reference to the preparation method in Example 1, with the difference that the time for plating the first blackening layer 3 was changed to make the thickness of palladium metal 150 nm, and the thickness of the second blackening layer 4 was 50 nm of palladium metal, to obtain Product Comparative Example 6.

[0125] Comparative Example 7

[0126] A touch sensor was prepared with reference to the preparation method in Example 1, with the difference that the thickness of the metal grid 2 was changed to a copper metal grid with a thickness of 1200 nm, to obtain Product Comparative Example 7.

[0127] Comparative Example 8

[0128] A touch sensor was prepared with reference to the preparation method in Example 1, with the difference that the thickness of the metal grid 2 was changed to a copper metal grid with a thickness of 300 nm, to obtain Product Comparative Example 8.

[0129] Performance tests of the brightness, conductivity, and visibility of the samples in Experimental Example 1

[0130] 1. Experimental method

[0131] The samples prepared in Examples 1 - 18 and Comparative Examples 1 - 8 were subjected to performance tests of brightness, conductivity, and visibility. The first test indicators were the brightness and conductivity of the copper metal grid before and after. The specific method was as follows: Under natural light conditions, a spectrophotometer CM - 5 from Konica Minolta was used to measure L*a*b to characterize the chromaticity of the copper metal grid of the test product, and a PerkinElmer spectrometer was used to measure the reflectivity of the metal grid surface. The lower the reflectivity, the less visible the grid. A multimeter was used to test the resistance of the metal grid with a fixed length of 55 mm and a line width of 5.5 μm to judge the conductivity of the metal grid. The measured resistance value was required to be within the range of 0.6 - 1.0 kΩ, and the functional touch was sensitive within this resistance value range.

[0132] Then, the visual appearance of the metal grids of the samples prepared in Examples 1-18 and Comparative Examples 1-8 was evaluated visually to assess the visibility of the metal grids. The evaluation method was as follows: When observing the visual appearance of the metal grids of the products, generally, for the same product with a fixed light source observation angle, the smaller the observation distance, the easier it is to see the grids. Therefore, different observation distances were used to distinguish the visualization effects of the metal grids of the products. Specifically, under the condition of indoor natural light, the general light intensity was 900-1550 lux (Lux), and the light intensity on the observation table in this experiment was set to 1200 lux (Lux). The long side of the above-mentioned sample of the rectangular metal wire to be observed was placed flat on the observation table at an angle of 45° in front of the observer. The distance between the observer's eyes and the sample of the rectangular metal wire was adjusted, and observations were made successively at distances of 40 cm, 35 cm, 30 cm, 25 cm, and 20 cm. The visibility of the metal wire was recorded, and the grade of the visualization effect of the metal grid was determined. Among them: The visualization effect of the metal grid was divided into five grades: S, A, B, C, and D. S means that the grid is invisible at an observation distance of 20 cm, and the effect is the best; A means that the grid is visible at an observation distance of 20 cm but invisible at an observation distance of 25 cm; B means that the grid is visible at an observation distance of 25 cm and invisible at a distance of 30 cm; C means that the grid is visible at an observation of 30 cm and invisible at a distance of 35 cm; D means that the grid is visible at 35 cm and invisible at a distance of 40 cm. When the two sides of the metal wire are different, the record with the worse effect is taken.

[0133] 2. Experimental Results

[0134] As can be seen from Table 1, the solutions of Examples 1-7 of the present invention can achieve a good blackening effect, significantly reduce the brightness of copper, and the grid is visually invisible, greatly improving the visual appearance effect (invisibility at an observation distance of 20 cm indicates a good visual appearance effect, and the closer the invisible nearest distance is as the distance increases, the worse the visual appearance effect. Among them, when the grid is visible at 35 cm and invisible at a distance of 40 cm, it can indicate a poor visual appearance effect). The visual appearance effect is A or S, and it does not affect its electrical conductivity, and the resistance value can meet the use requirements. Among them, the visual appearance effect of Example 3 is the best, which is S. The thickness of both layers of the blackened palladium layer is 80 nm, and the thickness of the copper layer is 500 nm. From the results of Example 8, it can be seen that the thickness of the first blackening layer is 60 nm, and the thickness of the second blackening layer is 90 nm. There are differences in the blackening effects on the front and back sides, resulting in a relatively poor overall visual appearance effect, reaching B.

[0135] From the results of Examples 9-10, it can be seen that if the concentration of disodium ethylenediaminetetraacetate, which mainly plays a role in complexing palladium ions in the preparation of the first blackening layer, is too high, the reaction rate will slow down, affecting the uniformity of the blackening layer; if the concentration of disodium ethylenediaminetetraacetate in the preparation of the first blackening layer is too low, the reaction rate will be too fast, resulting in a loose crystallization of the palladium layer, uneven blackening, and a poor visual appearance.

[0136] From the results of Examples 11-13, it can be seen that adding a specific dispersant polyethylene glycol 200 used in the preparation of the first blackening layer can prepare a blackening layer with more uniform distribution and chromaticity, thereby controlling the formation of a uniform blackening layer. However, adding an excessive amount of polyethylene glycol 200 or using other dispersants will affect the reaction rate, and further lead to a deterioration of the visualization effect.

[0137] From the results of Examples 14-15, it can be seen that if the concentration of sodium citrate, which plays a role in complexing palladium ions in the solution for preparing the second blackening layer, is too low, the reaction rate will be too fast, resulting in an uneven blackening layer and a poor visual appearance; if the concentration of sodium citrate in the solution for preparing the second blackening layer is too high, the reaction rate will be too slow, resulting in an uneven blackening layer and a poor visual appearance.

[0138] From the results of Examples 16-18, it can be seen that a specific surfactant sodium dodecyl sulfonate used in the preparation of the first blackening layer reduces the surface tension of the solution, enabling the blackening solution to come into full contact with the copper grid, thus making the blackening layer relatively uniform.

[0139] From the results of Comparative Example 1 and Comparative Example 3, it can be seen that without the first blackening layer or the second blackening layer, the copper wires on the reverse side or the front side will show a bright copper color, resulting in a poor visual appearance. From Comparative Example 2 and Comparative Example 4, it can be seen that if the blackening processes of the first blackening layer and the second blackening layer are different and there is a color difference in the blackening layer, it will cause a poor visual appearance. From the results of Comparative Examples 5-6, it can be seen that if the first blackening layer in the comparative example is too thin, it cannot achieve a good blackening effect; if the first blackening layer is too thick, it will more prominently show the bright white color of palladium metal, resulting in a poor visual appearance. The results of Comparative Examples 7-8 show that when the thickness of the copper layer is too thick at 1200 nm, the blackening effect is insufficient, resulting in a poor visual appearance; when the thickness of the copper layer is too thin at 300 nm, the blackening color is too bright, resulting in a poor visual appearance. In addition, insufficient copper thickness will cause the resistance to increase and cannot meet the performance requirements.

[0140] Table 1 Brightness, Resistance, and Visual Effect Ratings of Samples

[0141] Sample Number L a b Reflectivity Resistance / KΩ Visual Effect Rating Example 1 56.95 -1.02 -0.90 12.1％ 0.65 A Example 2 56.32 -1.32 -1.02 11.9％ 0.63 A Example 3 53.22 -2.48 -1.56 8.3％ 0.67 S Example 4 59.41 -0.92 -0.83 13.1％ 0.70 A Example 5 57.35 -0.94 -0.85 12.7％ 0.63 A Example 6 59.30 -0.87 -0.80 13.6％ 0.59 A Example 7 58.83 -0.85 -0.76 13.2％ 0.61 A Example 8 65.78 -0.70 -0.62 14.8％ 0.58 B Example 9 68.32 -0.56 -0.45 16.3 0.62 B Example 10 70.09 -0.60 -0.42 15.9 0.61 B Example 11 70.20 -0.52 -0.43 16.0％ 0.62 B Example 12 70.21 -0.51 -0.39 16.4％ 0.68 B Example 13 72.31 -0.48 -0.38 16.8％ 0.61 B Example 14 68.20 -0.68 -0.40 14.9％ 0.65 B Example 15 70.41 -0.50 -0.41 16.5％ 0.59 B Example 16 65.42 -0.83 -0.78 13.9％ 0.64 B Example 17 63.92 -0.86 -0.82 13.5％ 0.63 B Example 18 72.32 -0.42 -0.32 16.2％ 0.68 B Comparative Example 1 89.51 +1.05 +0.98 29.2％ 0.74 D Comparative Example 2 74.32 -0.50 -0.41 18.2％ 0.68 C Comparative Example 3 90.62 +1.32 +1.09 31.2％ 0.63 D Comparative Example 4 74.32 -0.39 -0.29 17.8％ 0.65 C Comparative Example 5 75.32 -0.36 -0.28 18.1％ 0.65 D Comparative Example 6 75.43 -0.33 -0.23 18.5％ 0.67 D Comparative Example 7 76.08 -0.23 -0.16 19.1％ 0.61 D Comparative Example 8 78.86 +0.51 +0.32 21.2％ 0.93 D

[0142] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a touch sensor for reducing the visibility of a metal grid, characterized in that, it comprises the following steps: S1. Double-sidedly coat a photoresist underlayer on a transparent substrate, and form a pattern driving layer through exposure and development; S2. Electrolessly deposit a layer of palladium metal for blackening on the pattern driving layer to form a first blackening layer with a thickness of 50 - 100 nm; S3. Electrolessly deposit a layer of copper metal on the first blackening layer in step S2 to form a metal grid with a thickness of 400 - 1000 nm; S4. On the metal grid, replace the metal surface of the metal grid in S3 with palladium metal for blackening through a chemical reaction to form a second blackening layer with a thickness of 50 - 100 nm; The first blackening layer and the second blackening layer have the same thickness; The solution composition and reaction conditions used in the electroless plating in step S2 are as follows: Solution composition: 1 - 3 g / L soluble palladium salt, 4 - 6 g / L hypophosphite, 14 - 18 g / L complexing agent, 150 - 200 ml / L weak base, 0.5 - 1.0 g / L dispersant; Reaction conditions: pH value 6 - 8, temperature 55 - 60 °C; The dispersant is polyethylene glycol 200; The surface replacement in step S4 is achieved through displacement palladium plating, and the solution composition and reaction conditions used are as follows: Solution composition: 0.5 - 2 g / L soluble palladium salt, 14 - 22 g / L complexing agent, 8 - 12 ml / L soluble organic acid, 0.1 - 0.5 g / L surfactant; Reaction conditions: pH value 5 - 6, temperature 49 - 51 °C; The surfactant is sodium dodecyl sulfonate.

2. The method for preparing a touch sensor for reducing the visibility of a metal grid according to claim 1, characterized in that, the solution composition and reaction conditions used in the electroless plating in step S3 are as follows: Solution composition: 5 - 10 g / L soluble copper salt, 15 - 20 g / L chelating agent, 6 - 10 g / L formaldehyde, 0.03 - 0.06 g / L stabilizer, 6 - 9 g / L strong base; Reaction conditions: temperature 38 - 40 °C.

3. The method for preparing a touch sensor for reducing the visibility of a metal grid according to claim 1, characterized in that, the photoresist underlayer in step S1 further contains a catalyst or a catalyst is coated on the surface of the photoresist underlayer.

4. The method for preparing a touch sensor for reducing the visibility of a metal grid according to claim 3, characterized in that, the catalyst is a palladium catalyst.

5. The method for preparing a touch sensor for reducing the visibility of a metal grid according to any one of claims 1 - 4, characterized in that, after the formation of the second blackening layer in step S4, it is also necessary to perform water washing and drying.

6. The method for preparing a touch sensor for reducing the visibility of a metal grid according to any one of claims 1 - 4, characterized in that, the transparent substrate is at least one of: polyethylene terephthalate, transparent polyimide, cycloolefin polymer, super retardation film, polycarbonate, polyethylene naphthalate, polymethyl methacrylate, triacetate fiber film, glass.

7. A touch sensor, characterized in that, It includes a transparent substrate (1), a pattern driving layer (5), a first blackening layer (3), a metal mesh (2), and a second blackening layer (4); pattern driving layers (5) are provided on both the upper and lower surfaces of the transparent substrate (1), and on the other surface of the pattern driving layer (5), there are successively arranged a first blackening layer (3), a metal mesh (2), and a second blackening layer (4). The thickness of the first blackening layer (3) is 50 - 100 nm, the thickness of the metal mesh (2) is 400 - 1000 nm, the thickness of the second blackening layer (4) is 50 - 100 nm. The first blackening layer (3) and the second blackening layer (4) have the same thickness. The touch sensor is prepared by the preparation method of the touch sensor for reducing the visibility of the metal mesh according to any one of claims 1 - 4.

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