JPH07257944A - Formation of transparent electrically conductive film - Google Patents

Abstract

PURPOSE:To obtain a transparent electrically conductive film having high resistance, high uniformity and high transmissivity and being useful as a transparent electrode of a touch panel by forming a transparent film and a transparent electrically conductive film each having a specified refractive index in a specified thickness each on a transparent glass substrate. CONSTITUTION:A transparent film having a refractive index of 1.6-1.9 is formed in 0.1-0.18mum thickness on a transparent glass substrate and a transparent electrically conductive film having a refractive index of 1.9-2.1 is formed in 0.01-0.03mum thickness on the transparent film. The transparent film can be made of MgO, Al2O3, GeO2, SiO2-TiO2 multiple oxide or SiO2-ZrO2 multiple oxide. The transparent electrically conductive film can be made of ITO, FTO, ATO, Al doped ZnO or In doped ZnO. By this film forming method, a glass with the objective transparent electrically conductive film for a touch panel having high transmissivity of >=89% at 0.55mum is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a transparent conductive film, and in particular, a method for forming a transparent conductive film having high resistance and excellent uniformity, which is used as a transparent electrode of a touch panel. Regarding

[0002]

2. Description of the Related Art Tin-doped indium oxide film (I
Fluorine-doped tin oxide film (FTO)
, And a tin oxide film doped with antimony (ATO
The aluminum oxide-doped zinc oxide film and the indium-doped zinc oxide film make use of their excellent transparency and conductivity to make use of liquid crystal displays, electroluminescent displays, surface heating elements, touch panel electrodes, and solar cells. It is widely used for electrodes and the like. When used in such a wide field, various resistance values and transparency are required depending on the purpose of use. That is, a transparent conductive film for a flat panel display is required to have a low resistance and a high transmittance, whereas a transparent conductive film for a touch panel is required to have a high resistance and a high transmittance. In particular, the conductive film for a pen input touch panel, which has been recently developed and is expected to grow in the market, needs to have high position recognition accuracy, and thus has a high sheet resistance of 200 to 3000 Ω / □ and a high resistance value. A film with excellent uniformity, and
Since it is placed on a liquid crystal display, it is required to be a film with high transmittance. In particular, the structure of the touch panel is such that glass with a transparent conductive film and a film with a transparent conductive film are faced to each other via a spacer and the periphery thereof is bonded, and the transmittance of the touch panel is a value obtained by multiplying the transmittance of the glass and the film. 80% transmittance as a touch panel
If you try to do more than 90
It is necessary to have a transmittance of not less than%, and even a transmittance of 1% is required. Usually, the method of achieving high transmittance was to reduce the film thickness.

[0003]

[Problems to be Solved by the Invention] ITO, FTO, AT
All of the transparent conductive film materials such as O and zinc oxide film have the refractive index of the substrate glass (1.5 for soda lime glass).
2) higher (1.9 to 2.1), the reflection at the interface between the transparent conductive film surface and the substrate glass increases, and the visible light transmittance decreases.

In order to obtain a film having a high transmittance, it is necessary to reduce the film thickness. However, if an attempt is made to obtain a transmittance of 85% at a wavelength of 0.55 μm, which is sensitive to human eyes, the film will be thin. The thickness must be 0.03 μm or less, 89%
In the case of the above transmittance, the film thickness needs to be 0.02 μm or less. Further, when the transmittance is 90%, the film thickness must be reduced to about 0.01 μm. In this case, it is difficult to control the film thickness uniformly, and the uniformity of the in-plane resistance value tends to deteriorate. It is in. In addition, the film thickness is 0.01
When the thickness is reduced to about μm, the stability of the resistance value deteriorates, and the resistance value fluctuates not only because of the in-plane uniformity of the resistance value, but also because the resistance value is easily affected by temperature and humidity changes. Indexing is an undesirable method.

The resistance value of the conductive film for a pen input touch panel is different from that for a liquid crystal display, and it is required to have a high resistance value, and a high transmittance and a high stability are required. It becomes 0.03 μm. When the film thickness of the conductive film is further increased, the transmittance at 0.55 μm becomes 9 due to the interference between the reflected light on the film surface and the reflected light on the substrate interface.
Although it increases to about 0%, the film thickness in this case is about 0.15 to
Since the thickness is 0.2 μm, which is too thick, the resistance value is 200Ω / □ or less, which is too low for a touch panel. Therefore, the thickness of the conductive film for a touch panel is 0.01 to
It can be said that 0.03 μm is a practical range. In this case, the transmittance of 0.55 μm is 90% to 85%.

A multilayer film is known as a method of increasing the transmittance without changing the film thickness of the conductive film, which is achieved by newly providing a film having a low refractive index between the conductive film and the glass substrate. It This method reduces the reflectance due to the interference effect of the reflected light at the interface between the substrate and the low refractive index film, the reflected light at the interface between the low refractive index film and the conductive film, and the reflected light at the conductive film surface, This is a method of increasing the transmittance, and the base film having a low refractive index serves to prevent reflection at the interface between the substrate and the conductive film. In this case, the reflectance can be reduced by controlling the refractive index and the film thickness of the base film according to the refractive index and the film thickness of the conductive film, and as a result, the high transmittance can be achieved.
For example, P. Kabo, Applied Physics Selection 3 "Thin Film" (Kanehara, Fujiwara) P. 197 to 200 describes the theory of reflection and transmission of a thin film, and a thin film on a substrate having a refractive index of 1.5 has an energy reflectance of 4 to 20% when the refractive index is 2.0. Is determined, the reflectance at a certain wavelength can be determined.

In addition, the above-mentioned P. Nos. 225 to 229 show a two-layer film as an example from the viewpoint of antireflection, and by applying this method, the transmittance can be increased. To actually apply this theory to reduce the reflectance, the refractive index of the substrate is about 1.5 and the refractive index of the conductive film is about 2.
By analogy with 0, it is desirable to form the base film with a material of 1.5 or less.

However, when this theory is actually applied, it is necessary to determine how to set the refractive index and the film thickness of the underlying low refractive index film according to the refractive index and the film thickness of the conductive film. However, it is difficult to find an optimal combination because there are many variables and many combinations are possible. Moreover, even if the refractive index is decided, whether or not the film actually formed has such a value depends on the selection of material and composition,
Since it is also related to the film forming conditions, it was very difficult to obtain the transmittance as optically designed.

As a conventional technique, when a transparent conductive film for liquid crystal display is formed on a soda lime glass substrate, particularly when an ITO film, an ATO film or an FTO film is formed, a soda lime glass substrate is provided between the substrate and the conductive film. Mainly for the purpose of suppressing the diffusion of sodium ions from silicon dioxide (S
It is known that an iO ₂ ) film is provided, and this method is known to extend the life of the liquid crystal display. Inexpensive soda lime glass is mainly used also for the touch panel substrate, and when the conductive film is patterned and used, it is necessary to prevent Na ions from diffusing from the etched part of the conductive film. The thickness of the SiO ₂ film for the purpose of suppressing the diffusion of Na ions increases as the thickness increases, so the thickness is generally 0.07 μm or more.

The optimum thickness of the SiO ₂ film is related to the firing temperature of the alignment film when assembling the liquid crystal panel. In this step, since the diffusion of Na ions to the surface is the largest,
The required film thickness is determined according to the processing temperature and time. Of course, if the firing temperature is low and the firing time is short, the SiO ₂ film thickness may be thin.

In order to obtain the reliability of the liquid crystal panel, it is a common method to make the film thickness of the SiO ₂ film than 0.07μm and for safety, the film thickness of the SiO ₂ film is 0.07μ
If it is more than m, the transmittance tends to decrease as the film thickness increases, which is not desirable from the viewpoint of increasing the transmittance.

The present invention has been made in view of the above circumstances, and provides a glass with a transparent conductive film for a touch panel having a high transmittance of 89% or more at 0.55 μm, and a method for forming the transparent conductive film. The purpose is to

[0013]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a method of forming a transparent conductive film having a high transmittance of 89% or more at 0.55 μm, and as a result, have a refractive index of 1.6 to 10 on a transparent glass substrate. A transparent film having a refractive index of 1.9 to 2.1 is formed on the transparent film of 0.1 to 0.18 μm.
It was found that a glass with a conductive film having a high transmittance can be obtained by using a film having a two-layer structure formed with a thickness of 01 to 0.03 μm. Hereinafter, the present invention will be described in detail.

According to the optical theory, as described above, the refractive index of the substrate is about 1.5 and the refractive index of the conductive film is about 2.0. It is inferred that it is possible to achieve a reduction in reflectance.

The present inventors have found that the underlying film has a refractive index of 1.
Even if the material is 6 to 1.9, the reflectance at 0.55 μm can be reduced by defining the film thickness.
As a result, they have found that the transmittance can be increased.

As described above, the sheet resistance is 200 to 3
The conductive film having a good stability of 000Ω / □ has a practical film thickness of 0.01 to 0.03 μm, and the transmittance at this film thickness is 85 to 90% (0.55 μm). According to the present invention, by providing an intermediate refractive index film between the transparent conductive film and the glass substrate, the reflection effect at the substrate-glass interface is reduced and the transmittance is increased by utilizing the interference effect of light. To do.

First layer film n = formed on the substrate of the present invention
As the transparent film of 1.6 to 1.9, MgO, Al
₂ O ₃ , GeO ₂ , a composite oxide of SiO ₂ and TiO ₂ ,
A film such as a composite oxide of SiO ₂ and ZrO ₂ can be used.

As a conventional technique, when a transparent conductive film for liquid crystal display is formed on a soda lime glass substrate, particularly when an ITO film, an ATO film or an FTO film is formed, soda lime is formed between the substrate and the conductive film. Si is mainly used to suppress the diffusion of sodium ions from the glass substrate.
Although it has been described that the O ₂ film is provided, if the transparent conductive film for a touch panel does not require patterning, no particular problem occurs even if Na ions from the substrate diffuse to the film surface. Therefore, any type of transparent film having a refractive index of 1.6 to 1.9 can be used as the base film, but when patterning is required, it is desirable to prevent diffusion of Na ions from the substrate. The purpose can be achieved by using a film having a composite composition containing SiO ₂ as a base film of the conductive film. The touch panel assembly process is different from the liquid crystal display assembly process at 200 ℃
For processing in the following temperature conditions, the diffusion of Na ions is low, SiO ₂ underlying film is to suppress the
Content is 30 mol% or more, and film thickness is 0.8 μm
The present invention has been completed by finding that the above is sufficient.

In the present invention, the transparent conductive film is I
TO, FTO, ATO, Al-doped ZnO, In-doped ZnO and the like are used, but the scope of the present invention is not limited to this.

As a method for forming a refractive index film with n = 1.6 to 1.9, a generally known method can be adopted.
That is, a predetermined material having a predetermined thickness is laminated and formed by a sputtering method, an electron beam evaporation method, an ion plating method, a chemical vapor deposition method (CVD method), a pyrosol method, a spray method, a dip method, or the like. Is achieved in.

[0021]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these.

Example 1 Soda lime glass (n = 1.52) having a thickness of 1 mm and a size of 10 cm was set in an atmospheric pressure CVD (pyrosol film forming) film forming apparatus by ultrasonic atomization, and 450 ° C. Heated to. Si C ₂ of (C ₂ H ₅ O) ₄
H ₅ OH solution (concentration 0.5 mol / l) and Ti (C ₄
H ₉ O) ₄ in C ₄ H ₉ OH (concentration is 0.5 mol
/ L) was mixed in an equimolar amount to 2.2 ml by ultrasonication.
/ Min, atomized, introduced into the substrate, and deposited for 12 minutes. The obtained film is SiO _{2 with} n = 1.65 and a film thickness of 0.13 μm.
It was a TiO ₂ composite film.

Subsequently, a solution of InCl ₃ in CH ₃ OH (concentration: 0.25 mol / l) containing SnCl ₄ in an amount of 10 atom% with respect to In was ultrasonically added to 2.5 ml / m 2.
It was atomized in, introduced into the substrate, and formed into a film for 2 minutes. Then, it was taken out from the film forming apparatus and cooled in air. The obtained film was an ITO crystal film with n = 1.95 and a film thickness of 0.022 μm. When the sheet resistance of this film was measured at 9 points, the average was 550 Ω / □ and the specific resistance was 1.2 × 10 ⁻³ Ωcm. The sheet resistance uniformity was within ± 45 Ω / □. The transmittance was 0.55 μm, which was 91.1%.

Example 2 In Example 1, Si (C
₂ H ₅ O) ₄ in C ₂ H ₅ OH solution and Ti (C ₄ H ₉ O)
Changing the mixing ratio of the C ₄ H ₉ OH solution _4, Si / Ti
Film formation was performed under the same conditions as in Example 1 except that the mixed solution having a molar ratio of 7/3 was used and the film formation time was changed to 10 minutes. The obtained SiO ₂ —TiO ₂ composite film has n = 1.5.
9, the film thickness was 0.11 μm. The sheet resistance, specific resistance, and uniformity after forming the ITO film showed exactly the same values as those of the film of Example 1. The transmittance of this film was 90.9% at 0.55 μm.

(Embodiment 3) The underlying film is formed by Al (C ₅ H
₇ O ₂ ) ₃ C ₅ H ₇ O ₂ solution (concentration 0.2 mol /
Film formation was carried out under the same conditions as in Example 1 except that l) was atomized by ultrasonic waves at 2.0 ml / min and introduced into the substrate and film formation was carried out for 15 minutes. The obtained base film has n = 1.7.
5, an amorphous Al ₂ O ₃ film having a film thickness of 0.14 μm. The sheet resistance, specific resistance, and uniformity after forming the ITO film showed exactly the same values as those of the film of Example 1. The transmittance of this membrane is 0.
It was 90.8% at 55 μm.

(Comparative Example 1) Using the pyrosol film forming apparatus shown in Example 1, only ITO film formation was performed under the same conditions as in Example 1. The sheet resistance, the specific resistance and the uniformity of the obtained film showed exactly the same values as those of the film of Example 1. The transmittance of this film was 87.8% at 0.55 μm.

Comparative Example 2 In Example 1, Si (C
Film formation was performed under the same conditions as in Example 1 except that the film formation was performed using a C ₂ H ₅ OH solution of ₂ H ₅ O) ₄ and the film formation time was changed to 8 minutes. The obtained SiO ₂ had n = 1.47 and a film thickness of 0.11 μm. The sheet resistance, specific resistance, and uniformity after forming the ITO film showed exactly the same values as those of the film of Example 1. The transmittance of this film was 88.6% at 0.55 μm.

The sample of the ITO film directly formed on the glass substrate (Comparative Example 1) has a transmittance of 87.8% at 0.55 μm.
However, it can be seen that by providing a base film having an intermediate refractive index between glass and a conductive film (Examples 1 to 3), a transmittance of 90% or more is obtained, and the effect of increasing the transmittance is large. This value is less than that of a SiO ₂ film having a lower refractive index than the substrate as an underlayer.
The transmittance is obviously higher than that in the case of forming a film of 11 μm (Comparative Example 2).

[0027]

According to the present invention, a transparent film having a refractive index of 1.6 to 1.9 of 0.1 to 0.18 μm is formed on a transparent glass substrate, and a transparent film having a refractive index of 1.9 to 2.1 is formed thereon. The transparent conductive film is set to 0.
It is a glass with a transparent conductive film having a thickness of 01 to 0.03 μm. By using such a transparent conductive film, it becomes possible to manufacture a glass having a transparent conductive film, which has an initial desired transmittance of 89% or more at 0.55 μm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuko Sakamoto 12-54 Goi Minamikaigan, Ichihara City, Chiba Pref.

Claims (6)

[Claims] 1. A refractive index of 1.6 to 1.9 on a transparent glass substrate.
Of 0.1 to 0.18 μm, and a transparent conductive film of refractive index of 1.9 to 2.1 of 0.01 to 0.03 μm.
Glass formed with a transparent conductive film. 2. The sheet resistance value of the transparent conductive film is 200 to 30.
The glass with a transparent conductive film according to claim 1, which has a resistance of 00 Ω / □. 3. A visible light wavelength of glass with a transparent conductive film is 0.55.
The glass with a transparent conductive film according to claim 1, which has a transmittance of 89% or more in μm. 4. The glass with a transparent conductive film according to claim 1, wherein the first layer film is a composite film made of silicon dioxide and titanium dioxide or a composite film made of silicon dioxide and zirconium dioxide. . 5. A refractive index of 1.6 to 1.9 on a transparent glass substrate.
Of 0.1 to 0.18 μm, and a transparent conductive film of refractive index of 1.9 to 2.1 of 0.01 to 0.03 μm.
A method for forming a transparent conductive film, which comprises forming a transparent conductive film. 6. A touch panel using the glass with a transparent conductive film according to claim 1.