JPH0513097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a transparent conductive film, and particularly to an improved method for forming a transparent conductive film on a glass substrate.

[Background Art] Transparent conductive films that are transparent to visible light and have electrical conductivity have been well known, and these transparent conductive films can be used as transparent electrodes, for example, in liquid crystal displays, electrochromic displays, and electroluminescent displays. It is widely used in sense displays, etc., and is also widely used in heat ray shielding films, electromagnetic shielding films, and other applications.

For forming such transparent conductive films, vacuum evaporation, sputtering, ion plating, chemical vapor deposition (CVD), spraying, and immersion methods are well known. Today, spray methods, dipping methods, etc. are widely used.

According to this spray method, a transparent conductive film can be formed on a glass substrate by spraying, for example, an aqueous solution of tin tetrachloride in fine particles onto a glass substrate heated to a high temperature. Therefore, according to this method, a vacuum is not required for forming a transparent conductive film, and the film can be formed using a simple device, which is extremely convenient when forming a transparent conductive film over a large area.

However, this spray method uses a carrier gas to attach fine particles of tin tetrachloride aqueous solution to the surface of the glass substrate, and therefore, if the airflow of the carrier gas is disturbed, the fine particles will adhere unevenly to the glass substrate. As a result, there was a drawback that a transparent conductive film with excellent optical properties and electrical properties and a uniform thickness could not be formed. Furthermore, as mentioned above, if turbulence occurs in the airflow of the carrier gas, some of the particles carried by the carrier gas will be scattered around without adhering to the glass substrate, resulting in a low adhesion efficiency of the particles and damage to the particulate material. The drawback was that it could not be used effectively.

Furthermore, according to such a conventional spray method, during the process of depositing fine particles onto a glass substrate to form a transparent conductive film, a large amount of alkali ions contained in the glass substrate diffuse into the transparent conductive film and cause the transparent conductive film to be formed. This method had the disadvantage of causing a decrease in film transparency and conductivity.

Further, according to the immersion method, a transparent conductive film is formed on the glass substrate by immersing the glass substrate in, for example, an organic indium compound solution, pulling it up at a constant speed, and subjecting it to high-temperature heat treatment. Therefore, since this immersion method does not require a vacuum, the film forming apparatus can be simplified and is suitable for forming a large area transparent conductive film.

On the other hand, however, with this immersion method, it is difficult to form a transparent conductive film of uniform thickness with excellent optical and electrical properties on a glass substrate, and moreover, the transparent conductive film is not formed over the entire surface of the glass substrate. Therefore, there is a large amount of wastage of membrane material, and furthermore, there are disadvantages in that there are many processing steps required for film formation compared to the above-mentioned spray method.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a transparent conductive film having a uniform film thickness and excellent optical and electrical properties on a glass substrate. An object of the present invention is to provide a method for forming a transparent conductive film that can be formed efficiently.

[Structure of the Invention] In order to achieve the above object, the method of the present invention includes arranging a positive electrode for charging on the front surface of a glass substrate, arranging a negative electrode for generating electrostatic force on the back surface of the glass substrate, and disposing a transparent conductive film material. After turning the solution containing microparticles into microparticles, the microparticles are charged to a positive potential using the positive charging electrode, and the electrostatic force generated between the charged microparticles and the glass substrate causes the charged microparticles to adhere to the surface of the glass substrate. The method is characterized in that a transparent conductive film is formed on the surface.

[Example] Next, a preferred example of the method for forming a transparent conductive film according to the present invention will be described based on the drawings.

Transparent Conductive Film Forming Apparatus FIG. 1 shows a preferred embodiment of the transparent conductive film forming apparatus to which the method of the present invention is applied. A transparent conductive film is formed by finely forming a solution 100 containing the above particles and depositing the particles.

Here, the glass substrate 10 of the example is formed using soda lime, and is held vertically by a heat insulating material 12 with its surface facing outside.

In the embodiment, the heat insulating material 12 is formed using a heat insulating material such as asbestos, and a heater 14 for heating the glass substrate 10 from the back side thereof is provided inside the heat insulating material 12.

Further, in this example, a solution of a predetermined metal compound is used as the solution 100, and the solution 100 is
0 is made into atomized fine particles using the atomization device 16.

A characteristic feature of the present invention is that the particles of the solution 100 thus formed are charged to a positive potential, an electrostatic force is generated between the charged particles and the surface of the glass substrate 10, and the electrostatic force causes the particles to be charged. The purpose is to form a transparent conductive film on the surface of the glass substrate 10 by attaching fine particles to the surface of the glass substrate. By doing this, the fine particles of the solution 100 are moved to the glass substrate 10 by the electrostatic force generated between the solution 100 and the glass substrate 10.
It becomes possible to form a transparent conductive film that is uniformly adhered to the surface of 0, has a uniform thickness, and has excellent optical and electrical properties.

Therefore, in the present invention, the glass substrate 10
A positive electrode 18 for charging is arranged on the front side of the glass substrate 10, and a negative electrode 2 for generating electrostatic force is arranged on the back side of the glass substrate 10.
0, the particles of the solution 100 formed by the atomization device 16 are charged to a positive potential using the positive electrode 18, and the charged particles and the glass substrate 1 are
Electrostatic force is generated between it and the surface of 0.

In the embodiment, the positive electrode 18 is formed as a needle-shaped electrode with the tip facing toward the center of the surface of the glass substrate 10, and the negative electrode 20 is formed of Ag so as to be in contact with the entire back surface of the glass substrate 10. Alternatively, it is formed into a flat plate using a graphite film or the like. The plus side of the DC power source 22 is connected to the plus electrode 18 via a ground line, and the minus side of the DC power source 22 is connected to the minus electrode.

The atomization device 16 of the embodiment has a solution 10 inside.
0 is housed and the ejection port 24 is the positive electrode 18 for charging.
a gas cylinder 28 in which nitrogen gas, for example, is sealed as a carrier gas, and a flow meter 30 and a valve 32. , is ejected into the atomizer 26 through the nozzle outlet 34.

When the carrier gas is ejected from the tip of the nozzle 34 in this manner, the solution 100 stored in the sprayer 26 is atomized by the ejection of the carrier gas, and is charged to a positive potential by the electrode 18.
It will be ejected toward the glass substrate 10.

Method for Forming a Transparent Conductive Film The apparatus of this embodiment has the above-described configuration.
An example will be explained in which the distance to the surface of 0 is set to 10 cm.

In the example, first, as a solution 100 containing a transparent conductive film material, 10 c.c.
A solution is formed by dissolving 10 g of indium trichloride and 2 g of tin tetrachloride in a solution containing cc.
0 is stored in the atomizer 26. In parallel to this,
The glass substrate 10 is heated to about 400° C. by the heater 14 to make it easy to form a transparent conductive film, which will be described later.

Then, the negative electrode 20 is
When a voltage of minus 15 kV is applied to the glass substrate 10 , the alkali ions contained in the glass substrate 10 are positively charged and are attracted to the negative electrode 20 side, that is, the back side of the glass substrate 10 , and are attracted to the front side of the glass substrate 10 . For example, there are many negative ions such as oxygen ions, and as a result, the surface side of the glass substrate 10 is charged to a negative potential, and an unequal electric field is formed between it and the positive electrode 18. corona discharge occurs.

In this state, when the valve 32 is operated to send carrier gas of 1 atm from the gas cylinder 28 to the atomizer 26 at a rate of 3/min, the solution 100 stored in the atomizer 26 can be easily absorbed because its viscosity coefficient is as small as several cm poise. The particles are atomized into fine particles having an average particle diameter of several μm, and are ejected from the ejection port 24 toward the surface of the glass substrate 10 .

At this time, as described above, since corona discharge is occurring around the positive electrode 18, the sprayer 2
The fine particles ejected through the ejection port 24 of No. 6 are charged to a positive potential by this corona discharge. and,
The charged fine particles are attracted with electrostatic force toward the glass substrate 10 whose surface is charged to a negative potential,
It adheres to the surface of the glass substrate 10 to form a transparent conductive film.

As described above, according to the present invention, the fine particles are attached to the surface of the glass substrate 10 by the electrostatic force generated between the positive potential of the charged fine particles and the negative potential of the surface of the glass substrate 10. Surface fine particles can be attached at high density without being affected by airflow turbulence, etc., and as a result, it is possible to form a transparent conductive film with a uniform thickness on the glass substrate 10.

Furthermore, according to the present invention, when forming this transparent conductive film, the alkali ions contained in the glass substrate 10 are attracted to the back side of the substrate by the negative electrode 20, so that the alkali ions are formed on the glass substrate 10. It becomes possible to effectively prevent alkali ions from diffusing into the transparent conductive film.

Thus, according to the present invention, the glass substrate 10
It is now possible to form a transparent conductive film with a uniform thickness and no diffusion and intrusion of alkali ions.
As a result, it is possible to effectively prevent the occurrence of light absorption, scattering, etc. inside the transparent conductive film and on its surface, and to achieve high light transmittance. The space is reduced and electron traps caused by diffused alkali ions are eliminated, making it possible to significantly reduce the resistivity of the transparent conductive film itself.

Furthermore, according to the present invention, since the transparent conductive film is formed on the substrate 10 using electrostatic force, the adhesion efficiency of fine particles to the surface of the glass substrate 10 is significantly improved, and as a result, the transparent conductive film is The film forming speed increases dramatically, making it possible to improve industrial productivity.

In addition, in this example, the solution used was 10
Since the viscosity coefficient of 0 is relatively small, the diameter of the fine particles formed by the jetting of the carrier gas is also small, and as a result, even if the voltage applied between the electrodes 18 and 20 is set to a low value of about 15 KV. It is possible to form a sufficiently transparent conductive film, and as a result,
It becomes possible to reduce the cost of the entire device.

Comparison of Characteristics of Transparent Conductive Film Next, the characteristics of the transparent conductive film formed by the method of the present invention will be compared with those of the transparent conductive film formed by the conventional method.

FIG. 2 shows the visible light transmittance of the transparent conductive film according to the method of the present invention and the transparent conductive film according to the conventional method. The visible light transmittance of the conventional transparent conductive film is 20.
As is clear from the figure, the visible light transmittance of the transparent conductive film according to the present invention is approximately 70%, whereas the visible light transmittance of the transparent conductive film according to the present invention is improved to approximately 85% on average. be done.

Similarly, when comparing the specific resistance of the present invention and the conventional transparent conductive film, the conventional transparent conductive film has a specific resistance of approximately
10 ^-3 Ωcm, whereas the transparent conductive film according to the present invention has a much smaller specific resistance of 4×10 ^-4 Ωcm, and it is understood that its electrical properties are improved.

Furthermore, when comparing the adhesion efficiency of fine particles onto the glass substrate 10, according to the conventional method, the adhesion efficiency was about 30%, whereas according to the present invention, the adhesion efficiency was about 80%. As a result, the film formation speed has increased dramatically compared to the conventional 500 Å/min.
It becomes possible to improve the speed up to 2000 Å/min.

As described above, according to the present invention, it is possible to form a transparent conductive film with a uniform thickness and superior optical properties and electrical properties compared to conventional transparent conductive films, and when forming the film, the adhesion efficiency of fine particles is improved. can also be significantly improved.

Other Embodiments Note that in the embodiment, the positive electrode 18
is the ground potential, and -15KV is applied to the negative electrode 22.
However, the present invention is not limited to this. For example, it is also possible to apply a voltage of +15 KV to the positive electrode and set the negative electrode 20 to the ground potential. Alternatively, the positive electrode and the negative electrode can be respectively grounded. The same effect can be achieved even if a 15KV DC voltage is directly applied between the two without any change.

Further, in the above embodiment, acetic acid n-
Although the case where a transparent conductive film is formed in a so-called reducing atmosphere using butyl and nitrogen gas sealed in the gas cylinder 28 as a carrier gas has been described as an example, the present invention is not limited to this, and can be applied to other methods. A solution can also be used. For example, even if a transparent conductive film is formed in an oxidizing atmosphere using water as the solvent of the solution 100 and air as a carrier gas, and then subjected to a reduction heat treatment, the result will not be the same as in the case of the above embodiment. It becomes possible to obtain similar effects.

In addition, in the embodiment, the atomization device 16
Because carrier gas is used, the glass substrate 10
The adhesion of charged fine particles onto the top was carried out by the interaction of the electrostatic force and the carrier gas described above, but the present invention is not limited to this. Using an ultrasonic vibrator, the solution 1 is generated by vibration of the pendulum.
It is also possible to make 00 into atomized fine particles, and by doing so, the adhesion efficiency is improved compared to the case where a carrier gas is used, and the gas cylinder 2
8. The flow meter 30, valve 32, etc. are not required, making it possible to make the entire device extremely simple.

Further, in the embodiment, the glass substrate 10
is installed vertically, and charged particles are applied horizontally. Therefore, there is a problem that natural convection occurs on the surface of the glass substrate 10 heated by the heater 14, the substrate 10 is cooled, and some of the fine particles are carried away by this natural convection, reducing the adhesion efficiency. . Therefore, in the present invention, the glass substrate 10 is placed horizontally with its surface facing downward, and charged fine particles are attached from the bottom of the glass substrate 10 to generate natural convection on the surface of the substrate 10. This makes it possible to effectively prevent this and further improve the adhesion efficiency of fine particles.

In addition, in the embodiment, the electrodes 18, 20
Although the explanation has been given taking as an example the case where a voltage of 15KV is applied between the glass substrates 10 and 10, the present invention is not limited to this.
The applied voltage can be set to an arbitrary value depending on the distance between the positive electrode 18 and the positive electrode 18 and other conditions.

[Effects of the Invention] As explained above, according to the present invention, it is possible to form a transparent conductive film with a uniform thickness and excellent optical properties and electrical properties on the surface of a glass substrate. When forming a film, it is possible to increase the adhesion efficiency of fine particles and effectively use the film material.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a preferred embodiment of an apparatus to which the method according to the present invention is applied, and FIG. 2 is a characteristic diagram of transparent conductive films formed by the method of the present invention and the conventional method. 10... Glass substrate, 18... Positive electrode for charging,
20...Negative electrode for electrostatic force generation.

Claims (1)

[Claims] 1. A positive charging electrode is placed on the front side of the glass substrate, a negative electrode for electrostatic force generation is placed on the back side of the glass substrate, and after a solution containing a transparent conductive film material is atomized,
The fine particles are charged to a positive potential by the positive charging electrode, and the charged fine particles are attached to the surface of the glass substrate by electrostatic force generated between the charged fine particles and the glass substrate, thereby forming a transparent conductive film on the surface of the glass substrate. A method for forming a transparent conductive film characterized by: 2. A transparent conductive method according to claim 1, characterized in that the negative electrode for generating electrostatic force is disposed over the entire back surface of the glass substrate to form an electric field between the surface of the glass substrate and the positive electrode for charging. How to form a film. 3. In the method according to either claim 1 or 2, a solution containing a transparent conductive film material is ejected in the form of fine particles toward a glass substrate using a predetermined carrier gas, and a positive electrode for charging is provided in the ejection path. A method for forming a transparent conductive film, the method comprising disposing the fine particles and charging the fine particles. 4. In the method according to any one of claims 1 and 2, a solution containing a transparent conductive film material is made into fine particles using an ultrasonic vibrator, the fine particles are charged using a positive charging electrode, and the glass substrate is charged. A method for forming a transparent conductive film, the method comprising depositing it on a surface. 6. In the method according to any one of claims 1 to 4, a glass substrate is placed horizontally with the surface facing downward, and charged fine particles are attached to the transparent conductive film from the lower side of the substrate. Formation method.