JPH07242442A - Glass with transparent conductive film and production of transparent conductive film - Google Patents

Abstract

PURPOSE:To form a transparent conductive film having high transmittance as a glass with a conductive film for a touch panel by forming a transparent conductive film having specified refractive index and film thickness with a three-layer structure. CONSTITUTION:A first layer film of multiple oxides such as TiO2, Y2O3, Sb2O3, and TeO2 is formed as a transparent film having 1.6-2.5 refractive index (n) and 0.05-0.2mum film thickness on a transparent glass substrate. Then a second layer film of multiple oxides such as SiO2, MgF2, SiO2, TiO2 as a transparent film having 0.35-1.5 n and 0.02-0.045mum film thickness is formed on the substrate, and a transparent conductive film such as ITO, FTO, ATO, Al-doped ZnO, In-doped ZnO having 1.7-2.2 n and 0.01-0.03mum film thickness is formed on the uppermost layer. These films are formed by sputtering, electron beam vapor deposition, ion plating, chemical vapor phase film forming or the like to specified thickness. The obtd. glass with transparent conductive films has 200-3000OMEGA/sq. resistance of the sheet and >89% transmittance for 550nm wavelength and is used for a touch panel.

Description

Detailed Description of the Invention

[0001]

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

[Prior art]

Indium oxide film doped with tin (IT
O), a fluorine-doped tin oxide film (referred to as FTO), an antimony-doped tin oxide film (referred to as ATO), an aluminum-doped zinc oxide film, and an indium-doped zinc oxide film are excellent. Utilizing transparency and conductivity, liquid crystal displays, electroluminescent displays, surface heating elements, touch panel electrodes,
Widely used for solar cell electrodes. 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 the pen input touch panel, which has been recently developed and is expected to grow in the market, requires high position recognition accuracy, so it is a film with high sheet resistance and excellent resistance value uniformity. In addition, since it is placed on a liquid crystal display, it is required to be a film having high transmittance. 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 than (1.7 to 2.2), the reflection at the interface between the transparent conductive film 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, in order to obtain a transmittance of 85% at a wavelength of 550 nm which is sensitive to human eyes, the film thickness is reduced. The film thickness needs to be 300 Å or less, and the film thickness needs to be 200 Å or less when the transmittance is 89%. Further, when the transmittance is 91%, the film thickness must be reduced to about 100 Å. In this case, it is difficult to control the film thickness uniformly, and the in-plane resistance value tends to be poor. . Further, if the film thickness is reduced to about 100 Å, the stability of the resistance value deteriorates, and the film is easily affected by temperature and humidity changes, and not only the in-plane resistance value uniformity but also the resistance value fluctuates. Increasing the transmittance by controlling the thickness is an undesirable method.

The resistance value of the conductive film for the pen input touch panel is required to have a high resistance value unlike that for a liquid crystal display, and since the high transmittance and the high stability are required, the film thickness is 100Å to 300Å. Become. When the film thickness of the conductive film is further increased, the transmittance at 550 nm increases to about 90% due to the interference between the reflected light on the film surface and the reflected light on the substrate interface. About 1500Å ~ 200
It becomes 0 Å, and it is difficult to adjust the resistance value to a predetermined value because it is too thick. Therefore, it can be said that the practical thickness of the conductive film for a touch panel is 100Å to 300Å. In this case, the transmittance at 550 nm 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. It is necessary to add a high refractive index film and a low refractive index film between the conductive film and the glass substrate. It is achieved by providing the. This method applies the interference effect of light between the substrate interface and the multilayer film, and the reflectance is reduced by controlling the refractive index and film thickness of the intermediate film according to the refractive index and film thickness of the outermost layer. It is possible to achieve high transmittance as a result. For example, P. Kabo, Applied Physics Selection 3 "Thin Film" (Kanehara, Fujiwara) P. 197-200 describes the theory of reflection and transmission of thin films, with a refractive index of 1.
The thin film on the substrate of No. 5 has an energy reflectance of 4 to 20% when the refractive index is 2.0 and the reflectance at a certain wavelength can be determined if the film thickness is determined. In addition, P. Reference numerals 225 to 229 show examples of the multilayer film from the viewpoint of antireflection, and it is possible to increase the transmittance by applying this method. However, when actually applying this theory, it is necessary to perform optical design of the intermediate film according to the refractive index and the film thickness of the outermost layer. That is, among the intermediate films, there are many variable factors for determining the refractive index and film thickness of the high refractive index film and the refractive index and film thickness of the low refractive index film. It was difficult to find the optimum combination among them, because there were a great many combinations.
In addition, even if the refractive index is determined, whether or not the film actually formed has such a value is related to the material selection, composition, and film formation conditions, so it is extremely difficult to achieve the transmittance as optically designed. It was a skill.

One of the methods for improving the reflectance characteristics by forming a multilayer film
Japanese Patent Laid-Open No. 4-154647 is disclosed as one example. This method has a refractive index n = 1.8 to between the transparent conductive film and the substrate.
A high refractive index film of 2.5, nd = 0.015 to 0.045
μm and a low refractive index film of n = 1.35 to 1.55 nd =
0.045-0.075 μm formed, and 0.15 on it
A method of forming a transparent conductive film having a thickness of μm or more, and a low refractive index film of n = 1.35 to 1.55 on the transparent conductive film nd =
This is a method of forming a film having a thickness of 0.08 to 0.15 μm.
According to the example, when an ITO film of 8000 Å is directly formed on a glass substrate, its spectral reflection characteristic shows a waveform having a maximum value (about 20%) and a minimum value (about 10%) depending on the wavelength, but it is transparent. By forming a two-layer undercoat film and a low-refractive-index overcoat film above and below the conductive film, the difference between the maximum and minimum can be reduced and the reflectance can be 8 to 10%.
It is supposed to be possible. From this, the effect of suppressing color unevenness is described.

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. It is known that a silicon dioxide (SiO ₂ ) film is mainly provided for the purpose of suppressing the diffusion of sodium ions from the glass substrate, and it is known that this method prolongs 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 present invention has been made in view of the above-mentioned circumstances, and is 55 as a glass with a conductive film for a touch panel.
It is an object of the present invention to provide a method for forming a transparent conductive film having a high transmittance of 89% or more at 0 nm.

[0010]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a method for forming a transparent conductive film having a high transmittance of 89% or more at 550 nm, and as a result, have a refractive index of 1.6 to 2. 5 to form a transparent film having a thickness of 0.05 to 0.2 μm, on which a transparent film having a refractive index of 1.35 to 1.5 is formed.
2 to 0.045 μm is formed. Furthermore, a refractive index of 1.
It was found that a glass with a conductive film having a high transmittance can be obtained by forming a transparent conductive film of 7 to 2.2 into a film having a three-layer structure in which 0.01 to 0.03 μm is formed, and to complete the present invention. I arrived. Hereinafter, the present invention will be described in detail.

As described above, the sheet resistance is 200 to 3
It is a conductive film with a good stability of 000Ω / □ and the practical film thickness is 1
It is 00 to 300Å, and the transmittance at this film thickness is 85 to 9
It becomes 0% (550 nm). In the present invention, by providing a high refractive index film and a low refractive index film 2 layers between a transparent conductive film and a glass substrate, the reflection at the substrate glass interface is reduced and the transmittance is increased by utilizing the interference effect of light. Is the way.

As the first layer film formed on the substrate of the present invention, the transparent film of n = 1.6 to 2.5 is TiO ₂ , Z.
rO ₂ , Ta ₂ O ₅ , Y ₂ O ₃ , Sb ₂ O ₃ , TeO ₂
Alternatively, composite oxides of TiO ₂ and SiO ₂ , ZrO ₂ and SiO ₂ , and the like can be used.

The transparent film of n = 1.35-1.5, which is the second layer film, includes SiO ₂ , MgF ₂ , SiO ₂ and TiO _2.
A film of a composite oxide of _{2 or} a composite oxide of SiO ₂ and ZrO ₂ can be used.

As the uppermost transparent conductive film, IT is used.
O, FTO, ATO, Al-doped ZnO, In-doped Z
Although nO or the like is used, the scope of the present invention is not limited to this.

Here, the present invention and one of the methods for improving the reflectance characteristics by forming a multi-layered film are disclosed in Japanese Patent Laid-Open No. 4-1546.
Differences from 47 will be described. The first difference is the thickness of the transparent conductive film. Since the main purpose of the present invention is a touch panel application, the thickness of the transparent conductive film is 100Å ~
The area is 300 Å, which is thinner than that described in JP-A-4-154647. The transparent conductive film described in the example of JP-A-4-154647 has a film thickness of 8000 Å. With such a thick film, a normal film has a sheet resistance of 100 Ω / □ or less, which cannot be used for a touch panel and becomes thick. This reduces the transmittance value. Therefore, 550 nm
Even if it shows a transmittance of 90% or more, it shows a maximum and a minimum depending on the wavelength, so that it becomes colored and becomes a problem (described in JP-A-4-154647, FIG. 10-1).
01). JP-A-4-154647, it is difficult to reduce the maximum and the minimum with only the underlayer film described in claim 1,
As shown at 81 in FIG. 8 in 154647, the reflectance is 8% to 20%, and the average reflectance in the visible light region is about 15%, and the maximum and minimum widths are certainly suppressed. However, the average reflectance has not changed. In comparison, in the case of the present invention, the conductive film has a film thickness of 100 Å to 300 Å, and the formation of the base film has a transmittance of 80% or more in the visible light region of 400 nm to 750 nm, which is 550 nm.
Transmittance increases to 89% or more.

As a second difference, Japanese Patent Laid-Open No. 1546/1991.
The main purpose of 47 is to prevent color unevenness of a thick transparent conductive film having a thickness of nd = 1500Å or more. A solution to this problem is not to control the underlying film of the conductive film, but to form a low refractive index film on the conductive film. The focus is on forming. On the other hand, the present invention intends to further increase the transmittance by forming a base film from a conductive film which originally has a high transmittance of 85% to 90%, and the purpose is different.

As described above, the present invention is disclosed in JP-A-4-15.
The invention is different from the invention described in No. 4647 in terms of objects, configurations and effects.

That is, the inventors of the present invention disclosed in Japanese Unexamined Patent Publication No. 4-154.
In the forming method described in 647, an increase in transmittance cannot be expected, and
It was found that a conductive film exhibiting a high transmittance can be obtained by combining the optimum refractive index and film thickness of the underlying film with respect to a conductive film of 0 Å or less.

Furthermore, when patterning the transparent conductive film for a touch panel, it is desirable to prevent Na ions from diffusing from the substrate. In that case, SiO ₂ is used as the low refractive index film underlying the conductive film, and the film thickness is reduced. To 200Å
It was also found that the above can suppress the diffusion of Na ions to the surface.

As a method of forming these films having different refractive indexes, 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. The object of the present invention is achieved.

[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 A 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 set to 450 ° C. Heated. Ti (C ₄ H ₉ O) ₄ C ₄ H ₉
An OH solution (concentration: 0.25 mol / l) was atomized by ultrasonic waves at 2.2 ml / min, introduced into the substrate, and a film was formed for 8 minutes. The film obtained has n = 2.10 and a T of 1000 Å.
It was an iO ₂ film (anatase crystal film). Continue to S
i (C ₂ H ₅ O) ₄ in C ₂ H ₅ OH solution (concentration: 0.5
(ml / l) was atomized by ultrasonic waves at 1.5 ml / min and introduced into the substrate, and a film was formed for 2 minutes. The resulting film has n =
It was a SiO ₂ film having a film thickness of 1.45 and a film thickness of 300 Å. Then, a solution of InCl ₃ in CH ₃ OH (concentration: 0.25 mol /
A solution obtained by adding 10 atomic% of SnCl ₄ to In in 1) was atomized by ultrasonic waves at 2.5 ml / min and introduced into the substrate to form a film for 2 minutes. After that, take it out from the film forming device,
Cooled in air. The obtained film was an ITO crystal film with n = 1.95 and a film thickness of 230Å. When the sheet resistance of this film was measured at 9 points, the average was 550 Ω / □ and the specific resistance was 1.
It was 3 × 10 ⁻³ Ωcm. Sheet resistance uniformity ± 45
Within Ω / □. Transmittance is 95.1% at 550 nm
showed that. The spectral characteristics (transmittance) of this sample are shown in FIG.
It was shown to.

(Example 2) In Example 1, Ti (C
Film formation was performed under the same conditions as in Example 1 except that the film formation time of the ₄ H ₉ O) ₄ solution in C ₄ H ₉ OH was changed to 6 minutes.
The obtained TiO ₂ had n = 2.12 and the film thickness was 790Å. The sheet resistance, the specific resistance, and the uniformity after the three-layer film formation showed the same values as those of the film of Example 1. The transmittance of this membrane is 55.
It was 93.5% at 0 nm. The spectral characteristics (transmittance) of this sample are shown in FIG.

(Example 3) In Example 1, Ti (C
Instead of a C ₄ H ₉ OH solution of ₄ H ₉ O) ₄ , Zr (C ₄
H ₉ O) ₄ in C ₄ H ₉ OH (concentration is 0.15 mol
/ L), and atomized by ultrasonic waves at 2.5 ml / min, and introduced into the substrate to form a film for 18 minutes. The resulting film has n
= 1.95 and a film thickness of 1160Å was a ZrO ₂ film. Other than that, the 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. This film has a transmittance of 550 nm of 9
It was a good film of 3.9%. The spectral characteristics (transmittance) of this sample are shown in FIGS.

Comparative Example 1 Using the pyrosol film forming apparatus shown in Example 1, only ITO film formation was carried out 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 85.4% at 550 nm. The spectral characteristics (transmittance) of this sample are shown in FIG.

Comparative Example 2 In Example 1, Ti (C
Film formation was performed under the same conditions as in Example 1 except that the film formation time of the ₄ H ₉ O) ₄ solution in C ₄ H ₉ OH was changed to 3 minutes.
The obtained TiO ₂ had n = 2.07 and a film thickness of 390Å. The sheet resistance, the specific resistance, and the uniformity after the three-layer film formation showed the same values as those of the film of Example 1. The transmittance of this membrane is 55.
It was 82.8% at 0 nm. The spectral characteristics (transmittance) of this sample are shown in FIG. 2-2.

Comparative Example 3 A film was formed under the same conditions as in Example 1 except that the ITO film forming time was changed to 10 minutes. The obtained film has n = 1.95 and a film thickness of 9
It was an 80 liter ITO crystal film. When the sheet resistance of this film was measured at 9 points, the average was 58 Ω / □ and the specific resistance was 5.7 ×.
It was 10 ⁻⁴ Ωcm. Sheet resistance uniformity is ± 5Ω / □
It was within. The transmittance was 76.5% at 550 nm. The spectral characteristics (transmittance) of this sample are shown in FIG.

From the above results, ITO is directly attached to the glass substrate.
The sample of the formed film (Comparative Example 1) has a transmittance of 85.4% at 550 nm, but by providing two layers of the undercoat film (Examples 1 to 3), a transmittance of 90% or more was obtained. The
Also, the average transmittance is increased by 5 to 10%, which shows that the effect of increasing the transmittance is great.

Further, the sample (Comparative Example 2) in which 200 Å ITO was formed on the undercoating film disclosed in JP-A-4-154647 had a transmittance at 550 nm of 82.8%.
Compared to Example 1, 2% to 450 nm to 750 nm in the region
The value was 10% lower. In addition, on the base film of Example 1, 9
When a thick ITO film of 50 Å is formed (Comparative Example 3), 7
It shows a low value of 6.5%, which shows that it is necessary to select the base film depending on the film thickness of the transparent conductive film. That is, 100Å
By applying the present invention to a transparent conductive film having a thickness of up to 300 Å, it is possible to significantly increase the transmittance at 550 nm.

[0030]

According to the present invention, the transmittance at 550 nm of a transparent conductive film having a somewhat high transmittance of 85% to 90% can be achieved without significantly reducing the transmittance in the visible light region.
It has the effect of increasing to 9% or more. In particular, it is possible to achieve the high transmittance required for glass with a transparent conductive film for touch panels. In addition, since a general material can be selected as the base film and a commonly used film forming method can be adopted, it is an excellent method in practice.

[Brief description of drawings]

FIG. 1 shows spectral characteristics (transmittance) of samples obtained in Examples 1 to 3 according to the present invention.

FIG. 2 shows the spectral characteristics (transmittance) of the samples obtained in Comparative Examples 1 to 3.

[Explanation of symbols]

In the figure, 1 is Example 1, 2 is Example 2, 3 is Example 3, 4
Indicates Comparative Examples 1 and 5, Comparative Examples 2 and 6 indicate Comparative Example 3, respectively.

Claims (6)

[Claims] 1. A transparent glass substrate having a refractive index of 1.6-2.
5, a transparent film having a thickness of 0.05 to 0.2 μm, a refractive index of 1.35 to 1.5, and a thickness of 0.02 to 0.045 μ
glass having a transparent conductive film, further comprising a transparent conductive film having a refractive index of 1.7 to 2.2 and a film thickness of 0.01 to 0.03 μm. 2. A transparent conductive film having a sheet resistance value of 200 to 3
The glass with a transparent conductive film according to claim 1, which has a resistance of 000 Ω / □. 3. The glass with a transparent conductive film according to claim 1, wherein the glass with a transparent conductive film has a transmittance at 550 nm of 89% or more. 4. The glass with a transparent conductive film according to claim 1, wherein the glass with a transparent conductive film is used for a touch panel. 5. The first layer film is silicon dioxide.
The glass with a transparent conductive film according to claim 3. 6. A transparent glass substrate having a refractive index of 1.6 to 2.5.
Transparent film of 0.05 to 0.2 μm is formed, and a transparent film having a refractive index of 1.35 to 1.5 is formed on it by 0.02 to 0.045 μm.
m. A method for forming a glass with a transparent conductive film, further comprising forming a three-layer film on which a transparent conductive film having a refractive index of 1.7 to 2.2 is formed in a range of 0.01 to 0.03 μm.