TW201716599A - Method of blackening silver wire and display device wherein a touch panel with good visibility is provided and the variation of the color and the resistance value of the silver wire can be prevented - Google Patents

Abstract

To provide a method of blackening a grid-like silver wire which is formed on a substrate to be used on a glass substrate or the like of a touch panel or the like. The method comprises a step of performing a first plasma treatment with high output and a second plasma treatment with low output on the surface of a substrate on which the silver wire has been formed, by which high purity and uniform silver oxide film can be formed on the surface of the silver wire, so as to blacken the silver wire. Furthermore, after the two plasma treatments are performed, heating is performed in the air, whereby the variation of the color and the resistance value of the silver wire can be prevented. Thus, it is possible to provide a touch panel with good visibility.

Description

Black line method and display device for silver line

The present invention relates to a method of blackening the surface of a silver line.

In the line portion of the touch panel display device (hereinafter referred to as a touch panel), the liquid crystal alignment electrode of the LCD, or the electrode for the organic electroluminescence display device, the transparent conductive oxide is indium tin oxide ( ITO) is used as an electrode line. However, since indium is a rare metal, there is a problem that it is insufficient in supply stability, and it is not suitable for application to a large area, and the price is high and the price fluctuates greatly. Further, since the resistivity of ITO is high, in a large touch panel, the response speed τ (resistance × electrostatic capacity) becomes sluggish, the detection sensitivity is lowered, and it is difficult to make the touch panel operate normally. Moreover, if the thickness of the ITO film is increased in order to reduce the electric resistance, there is a problem that the transmittance is remarkably degraded and the manufacturing cost is greatly increased.

Therefore, in recent years, in order to cope with the increase in the area of the display area, the manufacturing cost, and the like, a circuit material having low resistance and high visible light transmittance has been sought in place of ITO. In response to such a request, the following techniques have been attracting attention: low-resistance metals such as Cu, Ag, Al, and Mo are used as materials, and photolithography is used to form a grid-like fine metal line, so that not only low resistance but also light is improved. Transmittance. For example, by patterning a fine metal line having a width of 1 to 15 μm at a pitch of 50 to 500 μm, the line interval can be made wider than the width of the metal line, so that the light transmittance can be improved.

However, in the case of using a metal wiring, there is a case where the metal surface reflects external light and the visibility of the touch panel is deteriorated. In order to ensure better visibility, an anti-reflection layer must be formed on the surface of the metal wiring.

As the metal element used for the metal wiring, silver having the smallest electric resistance is preferably used, and as the antireflection layer of the silver wiring, the treatment of blackening the surface of the silver is being studied. Patent Document 1 discloses a technique in which a black silver oxide film is formed by a blackening treatment of a silver surface by wet oxidation performed by using a hydrochloric acid solution in which niobium is dissolved.

As another method of forming an antireflection layer of such a metal wiring, Patent Document 2 discloses a technique of forming a metal oxide using a reactive sputtering method.

[Prior Art Document] (Patent Document) Patent Document 1: JP-A-2011-82211 Patent Document 2: JP-A-2015-64756

[Problem to be Solved by the Invention] However, in the case of the oxidation method of silver which is carried out using a chemical, silver oxide contains a chlorine compound or a cerium (Te) compound, and color or line resistance occurs with time after blackening treatment. The problem of change (changes over time). Moreover, it is difficult to form a dense oxide film due to impurities or defects in the film, and it is difficult to control the film thickness of the oxide. Therefore, there is a problem that silver is excessively oxidized, line resistance is increased or broken, and the sensitivity of the touch panel is adversely affected, or the peel strength of the line on the surface of the substrate is lowered. Further, because of the use of pharmaceuticals, environmental problems have to be taken into consideration, and equipment and labor must be available.

On the other hand, in the case of using the reactive sputtering method, although a high-purity metal oxide film can be obtained, it is necessary to provide a high-priced high-vacuum device, and the cycle time is increased (time-consuming) due to vacuuming, and it is not stable. The production of the oxidized metal film on the side of the wiring pattern further increases the price of the target used for film formation, and the larger the area of the object to be formed, the more the manufacturing cost increases remarkably. Further, in the patterning manufacturing process for forming a wiring, in order to etch a laminated structure of a metal film and an oxidized metal film, it is necessary to have a technique of controlling the etching rate of both the metal film and the oxidized metal film. Further, there is a problem that this method cannot be applied to a metal wiring pattern formed by a printing method, and the application range is limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a main object thereof is to provide a technique for blackening a surface and a side surface of a silver wiring which forms a stable black silver oxide which does not change with time along the surface of the silver wiring.

[Technical means for solving the problem] Regarding the blackening method of the silver wiring of the present invention, the surface of the silver wiring patterned on the substrate is oxidized, characterized in that the blackening method of the silver wiring includes the following steps: a step of exposing the silver line to activated oxygen; and, the step of heating the silver line.

Further, the step of exposing the silver line to the activated oxygen is a step of irradiating the oxygen plasma to the silver line, characterized by comprising the steps of: irradiating the first oxygen plasma in the first plasma treatment And, in the second plasma treatment, the step of irradiating the second oxygen plasma.

The output of the plasma generated in the second plasma treatment is lower than the output of the first plasma treatment; the first plasma treatment is an Ag-O bond of the natural oxide of silver. Cut off the output.

Further, the gas used in the first plasma treatment has an oxygen concentration of 95 to 100%, and the gas used in the second plasma treatment has an oxygen concentration of 5 to 30%.

A high-purity silver oxide containing no impurities can be formed by a dry process in which the surface of the silver wiring is oxidized by using activated oxygen. Activated oxygen can be produced by introducing oxygen gas into a plasma processing apparatus and using oxygen plasma as desired under conditions. Further, by the first plasma treatment and the second plasma treatment, the surface of the silver is activated stepwise and the reaction is controlled, so that the entire surface of the line is uniformly oxidized, so that the surface of the silver line can be blackened in a controlled manner. Further, the plasma treatment can be handled in a reduced pressure atmosphere, and of course, it can be treated at normal pressure.

Further, in the first plasma treatment, the Ag-O bond of the natural oxide on the surface of the silver and the Ag-Ag bond on the silver surface are cleaved to make the surface of the silver active and oxidize the surface of the silver; In the two plasma treatment, a uniform silver oxide film can be formed with good controllability by providing a low plasma output compared to the first plasma treatment and by setting the plasma to a lower oxygen concentration.

The step of heating the silver line in an atmospheric pressure atmosphere is characterized in that it is heated in a normal pressure air at a temperature ranging from 80 degrees Celsius to 180 degrees Celsius.

After the surface of the silver oxide line is oxidized by the plasma treatment, the activity of the surface of the silver oxide film is stabilized by heating in an atmospheric pressure atmosphere, and the silver line resistance and the color of the line surface can be prevented from changing with time.

[Effects of the Invention] According to the blackening method of the silver wiring of the present invention, it is possible to obtain a low-resistance silver wiring which does not change with time and has a blackened surface even under atmospheric pressure. As a result, even in a large-area display device, a silver line that does not impair the visibility of the display screen can be provided at low cost.

The sequence of steps of the blackening process of the silver line according to the present invention is shown in Fig. 1. As shown in Fig. 1, on a substrate (1) made of a thin film or a glass substrate such as a transparent resin, a conventional patterning technique (for example, a combination of photolithography and etching, or high precision) is employed. Printing technology, etc.) The silver line (2) is formed into a grid shape, and the silver line (2) is subjected to the first plasma treatment (Fig. 1(a)) and the second plasma treatment (1st ( b) The two-stage plasma treatment consisting of Fig. 2, followed by heat treatment (Fig. 1(c)).

Further, the substrate (1) forming the silver wiring is not necessarily transparent, and for example, a substrate after applying an arbitrary color may be used.

Hereinafter, the blackening processing method of the following silver line will be described in detail with reference to Fig. 1 .

<Electrostatic treatment> The plasma treatment is to introduce a predetermined gas between the opposing electrodes, for example, at a normal pressure (atmospheric pressure), and apply a high-frequency voltage between the electrodes at a predetermined output (power) to generate a plasma. And the generated plasma is guided to the surface of the object to process the surface of the object. This treatment is a cleaning application or the like used for removing an organic substance on the surface of an object, and a normal piezoelectric slurry processing apparatus for this purpose is commercially available. In the present invention, the normal piezoelectric slurry processing apparatus can be utilized. Further, the plasma may be produced under reduced pressure as described above, or a reduced pressure plasma processing apparatus may be used. However, since the normal piezoelectric slurry processing apparatus does not require a vacuum apparatus and the apparatus price or the operation cost is low, there is an advantage that not only the manufacturing cost can be reduced, but also the processing capability is high.

<First plasma treatment> As shown in Fig. 1(a), in the first plasma treatment, the first oxygen plasma (3) generated at a high output is irradiated (sprayed) from the discharge nozzle (4) to Silver line surface.

In the first plasma treatment, as a high-output condition for performing oxygen plasma irradiation with high oxidizing ability, for example, it is set to 60 to 150 W/cm ² , and the gas introduced into the plasma processing apparatus has an oxygen concentration of 95 ～. In order to control the plasma gas temperature and the ozone concentration, the gas flow rate can be set to 10 to 40 L/min. In the case of a gas having an oxygen concentration of less than 100%, an inert gas such as nitrogen (inert gas) can be used as the mixed gas other than oxygen.

In the first plasma treatment, the following reaction occurs on the surface of the silver line. First, the Ag-O bond (Formula 1), (Formula 2), and Ag-Ag bond (Formula 3) of the natural oxide film on the surface of the silver line are cut, and the silver surface is all abruptly activated. 2Ag ₂ O → 4Ag + 2O ₂ (Formula 1) 2AgO → 2Ag + O ₂ (Formula 2) Ag → Ag ⁺ +e ^- (Formula 3)

Silver oxide is formed on the surface of the activated silver circuit by ozone (formula 4), (formula 5) and active oxygen (superoxide anion radical) (formula 6) and (formula 7) generated in this step. The substance (5), the silver oxide (5) becomes a crystal nucleus in which a silver oxide film grows. 2Ag+ O ₃ → Ag ₂ O + 2O ₂ (Formula 4) 3Ag+ O ₃ → AgO + O ₂ (Formula 5) 4Ag ⁺ + O ₂ ^- → 2Ag ₂ O (Formula 6) Ag + O ₂ → AgO (Formula 7)

That is, since the output (power) of the high-frequency voltage of the first plasma treatment is a high output, not only the silver is oxidized by silver but also the bond of the natural oxide film (Ag-O) of the silver is cut. effect. Such a processing condition can be found in the following manner: for example, by applying a plasma treatment to the silver oxide film prepared in advance to various changes, and confirming the film thickness of the silver oxide film before and after the plasma treatment, The film thickness of the silver oxide film begins to decrease. Further, since it is only necessary to cut the bond of the natural oxide film of silver, it is possible to finely adjust the output to be lower than the output set by the method.

Further, the object to be treated is the substrate (1), and the uniformity of the above reaction can be enhanced by maintaining a constant temperature between 25 and 100 degrees Celsius.

In addition, an important purpose of the first plasma treatment is to set the surface of the silver to an activated state, and it is not necessary to form a uniform silver oxide film.

<Second plasma treatment> Then, as shown in FIG. 1(b), in the second plasma treatment, the second oxygen plasma (6) generated by the output lower than the first plasma treatment is The silver line (2) is irradiated from the discharge nozzle (7).

The second plasma treatment is a treatment of oxidizing the surface of the active silver line which is not oxidized by the first plasma treatment, and the activation state of the surface of the silver line is leveled by being exposed to the oxygen plasma generated by the low output. (leveling), to prevent uneven oxidation, and to form a uniform silver oxide film (8) on the entire silver line.

The output of such second plasma treatment can be set to, for example, 10 to 60 W/cm ² .

Further, it is preferable that the introduced gas has a lower partial pressure of oxygen than the first plasma treatment, and a mixed gas of an inert gas such as nitrogen and oxygen is preferably used. A mixed gas having an oxygen concentration of 5 to 30% is introduced.

As described above, since the output of the second plasma treatment is a low output, the bond of the silver oxide is not cut, and a dense silver oxide film is formed with high purity. The dense silver oxide film suppresses the oxidation reaction of unreacted silver at the lower layer of the silver oxide film by preventing diffusion of oxygen. As a result, as the oxidation reaction of silver progresses, the thickness of the silver oxide film increases, and the oxidation rate of silver becomes sluggish, and the silver oxide film formed has a uniformity of about several tens of nanometers by the so-called self-limiting effect. thickness. That is, it is possible to form a thin silver oxide film which is uniformly and well controlled. Further, compared with the top surface of the silver line, the amount of plasma supplied to the side surface portion is lowered, and although a thin silver oxide film is formed, there is no problem in visibility.

Therefore, according to the blackening method of the oxidation of the silver line by the plasma treatment of the present invention, the resistance of the silver line due to the excessive oxidation reaction can be increased or the variation can be reduced.

Further, the second plasma treatment may also use a plasma processing apparatus used in the first plasma treatment, or a different plasma processing apparatus may be used. It is possible to use a device suitable for the constitution of each processing step.

For example, as a device configuration suitable for the second plasma treatment, in order to uniformly irradiate the oxygen plasma on the surface of the silver line, the shape of the discharge nozzle (6) can be set so that the plasma can be irradiated on a wide range of surfaces. For the discharge nozzle, a slit type nozzle is preferably used. Further, it is possible to provide a combination of a moving device capable of scanning the surface of the substrate 1 to 4 times.

<Heating Step> The black line after the blackening treatment is performed by the first plasma treatment and the second plasma treatment, and if placed in the atmosphere, color change or line resistance increases as time passes. . As a cause of such a change over time, it is considered that a part of silver remains in an activated state on the surface of the silver oxide film, and chemical reaction with oxygen, water, sulfur dioxide, or the like existing in the air is uneven, and silver containing impurities or defects is grown. The reason for the oxide film.

As a countermeasure against the change in the resistance of such a silver line, the inventors have made efforts to find out that an effective method is to heat in air under normal pressure. That is, after the first plasma treatment and the second plasma treatment are performed, the substrate having the silver wiring is heated in an atmospheric pressure atmosphere, whereby resistance change can be prevented.

Figure 1(c) is a cross-sectional view showing the heating step. As shown in the figure, the substrate (1) having the silver line (2) whose surface is oxidized by the first plasma treatment and the second plasma treatment is placed in the atmospheric pressure atmosphere by the heater (9) Heating is performed on the heated platform (10).

In the heating step, since the reduction reaction of silver oxide occurs when the heating temperature is 200 degrees Celsius or more, the heat treatment is performed at a temperature of 80 to 180 degrees Celsius.

Fig. 2 is a cross-sectional scanning electron microscope (SEM) photograph of a silver line after carrying out the blackening method of the present invention. It is understood that a silver oxide film having a thickness of 10 nm is uniformly formed. In addition, the change in the resistance value of the silver line after the blackening method of the present invention was carried out was examined. As a result, it was confirmed that the silver line resistance was maintained without change with time by the heat treatment.

The reason why the change in resistance can be prevented by the heating step is considered to be that the oxidation reaction on the surface of the silver which is activated by the plasma treatment is terminated and the surface is stabilized by heating in an atmospheric pressure atmosphere. As a result, variations in the resistance of the silver line can be prevented.

Further, the heating method in the heating step is not limited to the method of heating from the back surface of the substrate (1) as shown in Fig. 1(c), and may be heated from a top surface by a heater or the like. The heated air is supplied to the surface of the substrate having the silver wiring. It is only required to be heated under an atmospheric pressure atmosphere containing oxygen.

Further, although the atmospheric pressure atmosphere can reduce the manufacturing cost by using inexpensive air, an inert gas containing oxygen (for example, nitrogen or argon containing 20% of oxygen) can also be used.

In addition, since the first plasma treatment, the second plasma treatment, and the heat treatment are carried out in successive steps, it is of course possible to connect the devices for performing these treatments in order, and to connect the devices by the transfer device. A device is constructed that integrates a transparent substrate having a silver line.

By using the blackening method of the present invention, a silver line having silver oxide formed on the surface thereof is used as an electrode line, whereby a touch panel in which detection sensitivity is not deteriorated and visibility is good can be obtained, and further, by the present invention The silver line formed by the blackening method is not limited to the touch panel, and may be used as a low-resistance electrode line of a display device such as a liquid crystal panel, an organic electroluminescence display panel, or a plasma display panel (PDP). A display device with good visibility can be provided at low cost. Moreover, it can also be applied to a line such as a light-emitting diode.

1‧‧‧Substrate
2‧‧‧Silver lines
3‧‧‧Oxygen plasma
4‧‧‧Spray nozzle
5‧‧‧ Silver oxide
6‧‧‧Oxygen plasma
7‧‧‧Spray nozzle
8‧‧‧Silver oxide film
9‧‧‧heater
10‧‧‧ platform

Fig. 1 is a cross-sectional view showing a manufacturing procedure of a blackening method for a silver line according to the present invention. Fig. 2 is a cross-sectional scanning electron micrograph of a silver line after the blackening method of the present invention is carried out.

Domestic deposit information (please note according to the order of the depository, date, number)

Foreign deposit information (please note in the order of country, organization, date, number)

(Please change the page separately) No

1‧‧‧Substrate

2‧‧‧Silver lines

3‧‧‧Oxygen plasma

4‧‧‧Spray nozzle

5‧‧‧ Silver oxide

6‧‧‧Oxygen plasma

7‧‧‧Spray nozzle

8‧‧‧Silver oxide film

9‧‧‧heater

10‧‧‧ platform

Claims (8)

A method of blackening a silver line for blackening a surface of a silver line patterned on a substrate, characterized in that the blackening method of the silver line comprises the steps of: exposing the silver line to an activated a step in the oxygen; and a step of heating the silver line in an atmospheric atmosphere. The blackening method of the silver line according to claim 1, wherein the step of exposing the silver line to the activated oxygen is a step of irradiating the oxygen plasma to the silver line. The method for blackening a silver line according to claim 2, wherein the step of irradiating the oxygen plasma to the silver line comprises the steps of: irradiating the first oxygen plasma in the first plasma treatment; And, in the second plasma treatment, the step of irradiating the second oxygen plasma. The blackening method of the silver line according to claim 3, wherein the output of the plasma generated in the second plasma treatment is lower than the output generated by the plasma in the first plasma treatment. The method of blackening a silver line according to claim 4, wherein the first plasma treatment is an output capable of cutting Ag-O bonds of a natural oxide of silver. The method for blackening a silver line according to any one of claims 3 to 5, wherein the gas used in the first plasma treatment has an oxygen concentration of 95 to 100%, and the second plasma treatment The gas used in the gas has an oxygen concentration of 5 to 30%. The method of blackening a silver line according to any one of the preceding claims, wherein the step of heating the silver line in an atmospheric atmosphere is from 80 degrees Celsius to 180 degrees Celsius in air. The temperature range is heated. A display device in which a patterned silver line is formed on a substrate, wherein silver oxide is formed on a surface of the silver line, and the silver oxide does not contain any one of a chlorine compound and a ruthenium compound.