JPH08109046A - Method for stabilizing transparent electroconductive film having high resistance - Google Patents

Abstract

PURPOSE: To obtain glass with a transparent electroconductive film, suppressing change in sheet resistance by heating, having excellent stability, not increasing linearity value by a current-applying moisture resistance test, by covering the surface of a transparent electroconductive film formed on a transparent glass substrate with a thin film of silicon dioxide. CONSTITUTION: A transparent electroconductive film having 10-30nm film thickness and 200-3,000Ω/square sheet resistance is formed on a transparent glass substrate by using ITO, FTO, ATO, Al-doped ZnO, In-doped ZnO, etc., by any method of sputtering, CVD, spraying, etc. The film is overcoated with a film of silicon dioxide having 2-100nm thickness or a film of silicon dioxide doped with 0.1-20wt.% of at least one element of boron, fluorine and phosphorus by any method of sputtering, CVD or dipping to give glass with a stabilized transparent electroconductive film having a linearity value of ±2%.

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-attached glass and a method for forming a transparent conductive film, and particularly to the formation of a transparent conductive film having high resistance and excellent uniformity used as a transparent electrode of a touch panel. Membrane method.

[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 film having 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. It is required that the film has excellent uniformity.

There is a linearity test as a method for evaluating the uniformity of resistance value. In this method, low-resistance electrodes are made of silver paste or the like on two opposite sides of a transparent conductive film, and a DC voltage of 1 to 10 V is applied between the electrodes. At this time, the distance between both electrodes is D and the applied voltage is V. Let d be the distance from the negative electrode and v be the potential difference between the negative electrode and that point at any point of the transparent conductive film (d / D−v
/ V) × 100 is defined as linearity (%). The linearity value is a quantity that defines the deviation between the position and the position calculated from the detected potential difference. In a touch panel manufactured for the purpose of recognizing characters and figures, the linearity value is usually within ± 2% of the variation in resistance value. Required to be present. Further, since it is placed on the 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. However, if the film thickness is made too thin, the stability of resistance deteriorates, and if an environmental test is performed under various conditions, the linearity value increases, so it is difficult to achieve both high transmittance and resistance stability. Met.

[0004]

[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 (1.7 to 2.2), and when the film thickness of the transparent conductive film is increased, the reflection at the interface with the substrate is increased and the visible light transmittance is reduced. In order to obtain a film having a high transmittance, it is necessary to reduce the film thickness, but when it is attempted to obtain a transmittance of 85% at a wavelength of 550 nm which is sensitive to human eyes, the film thickness is 30 nm or less. Need to have a film thickness, 89%
In the case of the above transmittance, the film thickness needs to be 20 nm or less. When the film thickness is reduced to 30 nm or less, the resistance value is likely to change under the influence of temperature change and humidity change, and the in-plane resistance value uniformity is deteriorated. Therefore, when the environmental test is performed under various conditions, the linearity value increases due to the deterioration of the uniformity of the resistance value.

There are many commonly conducted environmental tests, ranging from 150 to
High temperature-short time test such as 30 to 60 minutes at 250 ° C, 8
Medium temperature-long time test such as 100 to 300 hours at 0 to 100 ° C., 100 at 50 to 80 ° C. and 90 to 100% RH
Medium temperature-high humidity-long time test such as ~ 300 hours, further applying 5-10V DC voltage, 30-80 ° C, 90-
Under energization at 100% RH for 100 to 300 hours-medium temperature-high humidity-long time test or 100 at -50 to -20 ° C.
There are low temperature-long time tests such as ~ 300 hours. Even if the resistance fluctuates by these environmental tests, if all the resistances in the plane fluctuate uniformly, the linearity value does not fluctuate and does not increase, but in the high temperature test, the carrier density of the conductive film changes due to the inflow and outflow of oxygen. Therefore, the resistance value varies greatly and the linearity value tends to increase. Further, in the high humidity test, the resistance often changes due to the adsorption of water, and the linearity value also tends to increase in this case. Under energization-medium temperature-high humidity-long-time test (referred to as energization humidity resistance test), the linearity value tends to remarkably increase because the way of resistance variation in the vicinity of the positive electrode and the negative electrode is different. That is, an oxidation reaction occurs near the plus electrode to increase the resistance of the conductive film, whereas a reduction reaction occurs near the minus electrode to decrease the resistance of the conductive film.
Therefore, the in-plane resistance of the conductive film has a high resistance portion and a low resistance portion, and as a result, the linearity value increases to ± 2% or more.

The present invention has been made in view of the above-mentioned circumstances, and provides a method for producing a stabilized transparent conductive film having a film thickness of 10 to 30 nm for a touch panel, the linearity of which does not change in various environmental tests. The purpose is to provide.

[0007]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a method in which the linearity value does not increase in an environmental test such as a resistance to humidity test. The inventors have found that a transparent conductive film having good properties can be obtained, and completed the present invention.

That is, the present invention provides: (1) a method for stabilizing a transparent conductive film, characterized in that the surface of a transparent conductive film formed on a transparent glass substrate is covered with a thin film of silicon dioxide, (2) above. (3) A sheet resistance value of the transparent conductive film is 200, wherein the silicon film contains at least one element selected from the three elements of boron, fluorine and phosphorus.
It is a touch panel characterized by using the above-mentioned methods for stabilizing a transparent conductive film having a linearity value of up to 3,000 Ω / □ and a linearity value of ± 2% or less, and a glass with a transparent conductive film produced by these methods. Hereinafter, the present invention will be described in detail.

As the transparent conductive film formed on the substrate of the present invention, ITO, FTO, ATO, Al-doped ZnO,
Although In-doped ZnO or the like is used, the scope of the present invention is not limited to this.

When an inexpensive soda lime glass (referred to as SLG) which is generally used in general is used as a substrate, a conductive film having a sheet resistance of 200 to 3000 Ω / □ and a practical film thickness of 10 to 30 nm. However, the resistance stability at this film thickness cannot be said to be good, and the resistance value fluctuates when various environmental tests are performed. The reason why the resistance value fluctuates is the exchange of oxygen on the film surface at high temperature, the adsorption of water under high humidity, the electrolytic oxidation and reduction under high electric current humidity, etc. It is considered that the resistance value fluctuates as a result of the interaction.
That is, if the conductive film is not affected by the external environment, resistance fluctuation will not occur and linearity will not change. From such a viewpoint, an antioxidant film on the conductive film,
It was thought that the purpose could be improved by overcoating the moisture prevention film, and an overcoat film that does not change the resistance of the conductive film and does not decrease the transmittance was searched and examined. As a result, they have found that a transparent conductive film having good resistance stability can be obtained even under various environmental tests by a method of overcoating a transparent conductive film with a silicon dioxide film.

The silicon dioxide film can be used by itself or as a film doped with at least one element selected from the elements of fluorine, boron and phosphorus. Silicon dioxide is known as an electrically insulating material.
If the film thickness is 0 nm or less, it exhibits conductivity, and further, a silicon dioxide film in which an organic group remains in the film using an organic silicon compound as a raw material, or micropores are generated in the firing process after the film is formed by a dip method or the like. It has been found that such a silicon dioxide film exhibits electrical conductivity even at a film thickness of 100 nm or less. That is, by overcoating such a silicon dioxide film, it is possible to eliminate the influence of the external environment without changing the sheet resistance value of the transparent conductive film.

The silicon dioxide film itself has a function of hindering the contact of oxygen and moisture on the surface of the transparent conductive film, and its effect is recognized. However, the silicon dioxide film is doped with an element such as boron, fluorine or phosphorus. Then, hydrophobicity and water repellency are given,
The humidity resistance is greatly improved. The doping amount of these elements is 0.1 to 20 wt%, and 0.5 to 10% is preferably used. If the thickness of the silicon dioxide overcoat film is too thick, it lowers the conductivity and increases the resistance, and if it is too thin, the effect of improving stability in various environmental tests is lost, so it is preferably 2 to 100 nm, preferably 5 to 100 nm. Overcoat with a film thickness of 50 nm.

The film is formed by sputtering, CVD,
It is possible to adopt a general film forming method such as a plasma CVD method, a pyrosol method, a dipping method, a spin coating method, or a printing method. As a method of adding boron, fluorine, or phosphorus, it may be added when the silicon dioxide film is formed. For example,
In the sputter method, boron, fluorine, and phosphorus compounds (B ₂ O ₃ , NH ₄ BF ₄ , NH ₄ F, NH ₄ PF ₆ , P ₂ O ₅ etc.) are added to the target, and in the CVD method, it is easy to vaporize organic substances. A boron compound, an organic fluorine compound, and an organic phosphorus compound may be added to the raw materials, and the dip method may add the compounds of these elements to the raw material solution. Examples of boron compounds include B (OCH ₃ ) ₃ , B (OC
₂ H ₅ ) ₃ , B (OC ₄ H ₉ ) ₃ , B (OC ₆ H ₅ ) ₃ , B (OC ₁₆ H ₃₃ ) ₃ , B (C ₄ H ₉ ) ₃ , B (O
H) ₃ , as a fluorine compound, NH ₄ F, CF ₃ CH ₂ OH, CF ₃ COOH, C
₆ H ₅ CF ₃ , CF ₃ C ₆ H ₄ CH ₂ OH, C ₄ F ₉ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CH ₂ ) ₂ S
_{i (OCH 3) 3, C} 4 F 9 (CH 2) 2 Si (OC 2 H 5) 3, as the phosphorus _{compound, PO (OC 2 H 5)} 3, PO (CH 3) 3, PO (C 6 H ₅ ) ₃ , P (OCH ₃ ) ₃ , P (OC
_{2 H 5) 3, P (} OC 18 H 35) 3, can be mentioned _{P (OC 6 H 5) 3} .

When the film is formed by the dip method, the spin coat method, or the printing method, the film is baked at 200 to 500 ° C.,
The higher the baking temperature is, the denser the film is and the higher the insulating property is. The lower the baking temperature is, the more organic substances are likely to remain in the film and the lower the insulating property is. Therefore, it is necessary to match the film thickness with the baking temperature. 100 to 200 when the film thickness is 50 to 100 nm
C., 200 to 300.degree. C. when the film thickness is 30 to 50 nm,
When the film thickness is 30 nm or less, it is preferable to select a firing temperature of 300 ° C. or higher.

As a method for forming the transparent conductive film, a generally known method can be adopted. That is, 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,
This is achieved by forming a predetermined material with a predetermined thickness by a dip method or the like.

[0016]

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 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 heated to 450 ° C. InCl ₃ CH ₃ O
SnCl ₄ was added to H solution (concentration: 0.25 mol / l)
2. A solution in which 10 atomic% of n is added by ultrasonic wave.
It was atomized at 5 ml / min, 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 having a film thickness of 21 nm. When the sheet resistance of this film was measured at 9 points, the average was 550Ω.
/ □, the specific resistance was 1.1 × 10 ⁻³ Ωcm. The sheet resistance uniformity was within ± 45Ω / □ on average. The transmittance was 90.0% at 550 nm. Continue to Si (C ₂
H ₅ O) ₄ in C ₂ H ₅ OH (concentration 0.5 mol /
l) was atomized by ultrasonic waves at 2.2 ml / min and introduced into a substrate to form a film for 2 minutes. The film thickness of SiO ₂ was 30 nm. When the sheet resistance and the transmittance were measured, the average sheet resistance was 580 Ω / □, and the uniformity of the sheet resistance was ± 50 Ω /
It was within □. The transmittance at 550 nm was 89.7%. A heat resistance test and an electric humidity resistance test were performed on this sample. In the heat resistance test, when a resistance change after heating at 200 ° C. for 1 hour was measured, the sheet resistance was 600 Ω / □ on average, and the uniformity of the sheet resistance was ± 53 Ω / □ on average. The electric humidity resistance test was performed as follows. First, apply a conductive silver paste to the opposite sides of this sample.
An electrode was prepared by coating with a width of mm. DC 5V is applied to these two electrodes to provide linearity in 5 rows (15 mm interval),
When measured at 10 points / row (8 mm interval), -0.2 to
The value was 0.4%. 7V, 40 ° C, 95 of this sample
When linearity was measured after standing for 240 hours under the condition of% RH, the value was −0.1 to 0.5%, and ± 1.
The change was within%.

Example 2 In the SiO ₂ film formation of Example 1, Si (C ₂ H ₅ O)
_{B in 4} C ₂ H ₅ OH solution (concentration 0.5 mol / l)
The same procedure as in Example 1 was performed except that a raw material obtained by adding 5 mol% of (OCH ₃ ) ₃ to Si was used. B
The film thickness of the doped SiO ₂ was 35 nm. When the sheet resistance and the transmittance were measured, the sheet resistance was 560 on average.
Ω / □, and the sheet resistance uniformity is ± 48Ω / average.
It was within □. The transmittance was 89.6% at 550 nm. When a heat resistance test and an electric humidity resistance test were conducted in the same manner as in Example 1, the sheet resistance after the heat resistance test was 570 Ω / average.
□, and the uniformity of the sheet resistance was within ± 50Ω / □ on average. The linearity before the electric humidity test is -0.4
The value was ˜0.1%. This sample is 7V, 40 ℃, 9
After standing for 240 hours under the condition of 5% RH, the linearity was measured under the same conditions as before the test.
The value was 2%, which was almost unchanged.

Example 3 In the SiO ₂ film formation of Example 1, Si (C ₂ H ₅ O)
₄ C ₂ H ₅ OH solution (concentration 0.5 mol / l) in C
₄ F ₉ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ with F / Si = 5
The same procedure as in Example 1 was carried out except that the raw material added in mol% was used. The thickness of F-doped SiO ₂ is 27 nm
Met. When the sheet resistance and the transmittance were measured, the sheet resistance was 530 Ω / □ on average, and the uniformity of the sheet resistance was ± 48 Ω / □ on average. Transmittance is 550
It showed 89.8% in nm. When a heat resistance test and an electric resistance / moisture resistance test were conducted in the same manner as in Example 1, the sheet resistance after the heat resistance test was 540 Ω / □ on average, and the uniformity of the sheet resistance was within ± 50 Ω / □ on average. The linearity before the electrical humidity resistance test was a value of -0.2 to 0.1%. When this sample was left for 240 hours under the conditions of 7V, 40 ° C. and 95% RH, the linearity was measured under the same conditions as before the test, and the value was −0.1 to 0.3%, showing almost no change. There wasn't.

Example 4 In the SiO ₂ film formation of Example 1, Si (C ₂ H ₅ O)
P in ₄ C ₂ H ₅ OH solution (concentration 0.5 mol / l)
The same procedure as in Example 1 was carried out except that a raw material containing P (Si) = 5 mol% of O (OCH ₃ ) ₃ was used. P
The film thickness of the doped SiO ₂ was 33 nm. When the sheet resistance and the transmittance were measured, the sheet resistance was 560 on average.
Ω / □, average sheet resistance is ± 54Ω /
It was within □. The transmittance was 89.6% at 550 nm. When a heat resistance test and an electric humidity resistance test were conducted in the same manner as in Example 1, the sheet resistance after the heat resistance test was 580 Ω / average.
□, and the sheet resistance uniformity was within ± 56 Ω / □ on average. The linearity before the electric humidity test is -0.2
It was a value of 0.4%. This sample is 7V, 40 ℃, 9
When the linearity was measured under the same conditions as before the test after standing for 240 hours under the condition of 5% RH, it was -0.1 to 0.
The value was 6%, and the change was within ± 1%.

Example 5 Instead of the ITO film in Example 1, FT was performed by the following method.
An O film was formed. The raw material was SnCl ₄ in CH ₃ OH (concentration 0.3 mol / l) and NH ₄ F in F / Sn = 5 m.
A liquid added with ol% was used. The film forming temperature was 420 ° C., and the film was atomized by ultrasonic waves at 2.0 ml / min for 2.5 minutes. The obtained film was an FTO crystal film having a film thickness of 24 nm. When the sheet resistance of this film was measured at 9 points, the average was 9
It was 50Ω / □ and the specific resistance was 2.3 × 10 ⁻³ Ωcm. The sheet resistance uniformity was within ± 88 Ω / □ on average. The transmittance was 88.7% at 550 nm. After that, a SiO ₂ film was formed in the same manner as in Example 1. When the sheet resistance and the transmittance were measured, the sheet resistance was 1 on average.
It is 060Ω / □, and the sheet resistance uniformity is ± 9 on average.
It was within 4Ω / □. Transmittance is 88.4 at 550 nm.
%showed that. When a heat resistance test and an electric humidity resistance test were conducted in the same manner as in Example 1, the sheet resistance after the heat resistance test was 10 on average.
80Ω / □, and the sheet resistance uniformity is ± 98 on average.
Within Ω / □. The linearity before the electric humidity resistance test was a value of −0.4 to 0.4%. This sample is 7V, 4
When the linearity was measured under the same conditions as before the test after standing for 240 hours under the conditions of 0 ° C. and 95% RH, it was −0.
The value was 3 to 0.6%, and the change was within ± 1%.

Comparative Example 1 An ITO film was formed in the same manner as in Example 1. When a heat resistance test and an electric humidity resistance test were performed in the same manner as in Example 1 without overcoating this film, the sheet resistance after the heat resistance test was 740 Ω / □ on average, and the uniformity of the sheet resistance was
The average was ± 145 Ω / □. The linearity before the electrical humidity resistance test was a value of -0.3 to 0.3%. After this sample was allowed to stand for 240 hours under the conditions of 7 V, 40 ° C. and 95% RH, the linearity value was measured under the same conditions as before the test, and the linearity value increased to 3.2 to 4.4%.

Comparative Example 2 An FTO film was formed in the same manner as in Example 5. When a heat resistance test and an electric humidity resistance test were conducted in the same manner as in Example 5 without overcoating this film, the sheet resistance after the heat resistance test was 1240 Ω / □ on average, and the uniformity of the sheet resistance was ± 220 Ω on average. It became / □. The linearity before the electrical humidity resistance test was a value of -0.4 to 0.5%. After this sample was left under conditions of 7 V, 40 ° C. and 95% RH for 240 hours, the linearity value was measured under the same conditions as before the test, and the linearity value increased to 2.8 to 4.2%.

The heat resistance of the film (Comparative Example 1) formed by simply depositing ITO on the glass substrate was poor, and the sheet resistance increased about 1.3 times, and the uniformity deteriorated to about ± 20%. When the overcoating according to the invention is carried out, the sheet resistance, the uniformity and the transmittance after the overcoating do not change so much,
After the heat resistance test, the sheet resistance is suppressed to 1.1 times or less, and the uniformity is maintained within ± 10%. Further, the linearity in the case of conducting the resistance to humidity test was 2% or more in the film without the overcoat (Comparative Example 1), but the linearity was within ± 1% by the overcoat of the present invention. Showed the value. Similar results were obtained for the FTO film, indicating that the effect was large.

[0025]

As described above, according to the method of the present invention, it is possible to prepare a glass with a transparent conductive film which suppresses a change in sheet resistance due to heating and which is excellent in stability such that a linearity value does not increase in a resistance to humidity test. Can be done.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Kawamura 12-8 Goi Minamikaigan, Ichihara City, Chiba Nisso Kasei Co., Ltd.

Claims (4)

[Claims] 1. A method for stabilizing a transparent conductive film, which comprises covering the surface of a transparent conductive film formed on a transparent glass substrate with a thin film of silicon dioxide. 2. The method according to claim 1, wherein the silicon dioxide film contains at least one element selected from the group consisting of boron, fluorine and phosphorus. 3. The sheet resistance value of the transparent conductive film is 200 to 3
The method for stabilizing a transparent conductive film according to claim 1, wherein the linearity value is within ± 2%. 4. A touch panel using the glass with a transparent conductive film produced by the method according to any one of claims 1, 2 and 3.