JPH08132554A - Transparent conductive film - Google Patents

Abstract

PURPOSE: To obtain a transparent conductive film enhanced in abrasion resistance and capable of being suitably used in a touch panel electrode by forming a silicon oxide layer with specific thickness and a layer composed of a transparent conductive film on a transparent polymeric film. CONSTITUTION: A transparent conductive film is obtained by successively forming at least a first silicon oxide layer 20 with a thickness of 60-500nm and a second layer 30 composed of a transparent conductive film on one main surface of a transparent polymeric film 10. The center line average roughness of the transparent polymeric film is pref. 0.01-1μm. As the base material of the film used herein, polyethylene terephthalate, polyether sulfone, polyether ether ketone and polycarbonate are designated. The thickness of the film is usually about 10-250μm. The silicon oxide layer is formed by a vacuum vapor deposition method, a sputtering method or a CVD method.

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 having improved wear resistance, and more particularly to a transparent conductive film having excellent wear resistance which can be suitably used for a touch panel electrode.

[0002]

2. Description of the Related Art Conventionally, transparent conductive films have been used for electrodes of display elements such as liquid crystal displays, electroluminescent displays and electrochromic displays,
It is used as a window electrode of a photoelectric conversion element such as a solar cell, an electromagnetic wave shielding film of an electromagnetic wave shield, or an electrode of an input device such as a transparent touch panel.

Conventionally known transparent conductive layers include noble metal thin films such as gold, silver, platinum and palladium, indium oxide,
Oxide semiconductor thin films such as stannic oxide and zinc oxide are known. The former noble metal thin film having a low resistance value can be easily obtained, but the transparency is poor. The latter oxide semiconductor thin film has a resistance value slightly inferior to that of a noble metal thin film, but is widely used because of its excellent transparency. Among them, indium oxide thin films containing tin oxide are widely used because they have low resistance and excellent transparency. The resistivity of the tin-doped indium oxide thin film is usually 5 × 10 ⁻⁵ to 1 × 10 ⁻³ Ω · c.
m, the transmittance is generally 80 to 90%.

When a transparent conductive film is used for an input device such as a touch panel, the required characteristics differ depending on the structure of the touch panel, but the analog type method has a sheet resistance of 200 to 1000 in terms of power consumption.
Ω / □ is preferably used, and further, sheet resistance uniformity is desired from the viewpoint of position detection accuracy. In addition, the transparent touch panel is required to have transparency because it is used by being overlapped with a display device such as a liquid crystal display, and it is also desired to have both mechanical strength and environmental durability.

[0005]

However, when a transparent conductive film is used in an analog type touch panel, a pair of transparent conductive films facing each other via a spacer are in strong contact with each other. Was deteriorated, its electric resistance increased, and the touch panel did not operate normally. Practically, in a wear resistance test in which gauze is used as a wear material, a load of 500 g weight / cm ² is applied, and the transparent conductive layer side is abraded 200 times (100 reciprocations), the rate of increase in surface electrical resistance is 2 Unless otherwise, it cannot be used as a transparent electrode of a touch panel. In the case of the transparent electroconductive film having a single-layer structure in which the transparent electroconductive layer is directly formed on one main surface of the transparent polymer film, the surface electrical resistance increase rate in the above abrasion resistance test was 2 or more. The present invention, in view of the above conventional circumstances,
It is intended to provide a transparent conductive film having excellent abrasion resistance.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have surprisingly formed a layer having excellent wear resistance directly on the wear surface. Instead of forming a silicon oxide layer having a thickness of at least 60 to 500 nm on one main surface of the transparent polymer film,
By further forming a transparent conductive layer thereon, it was found that the wear resistance of the transparent conductive layer is significantly improved even though the wear surface is the transparent conductive layer, and the present invention is completed. Came to.

That is, the present invention will be described with reference to FIG. 1, in which a first layer (20) made of silicon oxide having a thickness of at least 60 to 500 nm is provided on one main surface of the transparent polymer film (10). , A second layer (3
0) and a transparent conductive film that are sequentially formed, that is, a first layer (B) made of a silicon oxide having a thickness of at least 60 to 500 nm on one main surface of the transparent polymer film (A). ) And a second layer (C) comprising a transparent conductive film.
And a transparent conductive film having a structure of ABC, and the transparent polymer film having a center line average roughness of 0.01 to 1 μm. .

These are transparent conductive films that can be suitably used for touch panel electrodes. As the film substrate used in the present invention, a transparent plastic film can be used, and specifically, a polyethylene terephthalate film, a polyether sulfone film,
Examples thereof include polyether ether ketone film, polycarbonate film, polypropylene film, polyimide film and the like. The thickness of these films is usually about 10 to 250 μm. If the thickness of the film is too thin, the mechanical strength as the base material is insufficient, and conversely if it is too thick, the flexibility is insufficient. It is not preferable because a large load is required for the misalignment. Among the above-mentioned transparent polymer films, the polyethylene terephthalate film is excellent in transparency and processability, and thus can be more preferably used. Further, since the polyether sulfone film is excellent in heat resistance, when heat treatment is required after producing the transparent conductive film, or when heat treatment is required when assembling a touch panel using the transparent conductive film. It can be used more suitably.

The center line average roughness (Ra) of this transparent polymer film is preferably 0.01 to 1 μm, more preferably 0.02 to 0.2 μm. The center line average roughness referred to here is the Japanese Industrial Standard JIS-B-O6O.
It is defined in 1. The centerline average roughness is 0.
If it is less than 01 μm, the effect of improving wear resistance cannot be obtained even if a silicon oxide layer is formed on a transparent polymer film and a transparent conductive layer is further formed thereon. Further, if the center line average roughness exceeds 1 μm, even if a transparent conductive film is produced using the transparent polymer film, it is not possible to obtain a haze value that is sufficiently low.

The surface of this transparent polymer film is subjected to an etching treatment such as a sputtering treatment, a corona treatment, a flame treatment, an ultraviolet ray irradiation, an electron beam irradiation or the like in advance, or an undercoating treatment, and the silicon oxide formed on the surface and the above You may perform the process which improves the adhesiveness with respect to a film. Also,
Before forming the silicon oxide film, if necessary, a dustproof treatment such as solvent cleaning or ultrasonic cleaning may be performed.

In the present invention, a silicon oxide layer is formed on one main surface of such a transparent polymer film substrate. As a method for forming the silicon oxide layer, conventionally known thin film forming methods such as vacuum vapor deposition, sputtering, physical vapor deposition such as ion plating, and chemical vapor deposition such as plasma CVD can be used. In addition, a coating method in which the silazane polymer is coated and then dried by heating can be used.

In the plasma CVD method, 1, 1, 3,
3-Tetramethyldisiloxane (liquid at room temperature) is vaporized by bubbling with an inert gas such as helium gas and introduced into a vacuum chamber, where oxygen gas is mixed and plasma is generated to generate silicon oxide. A desired silicon oxide layer can be obtained by precipitating. Plasma CV
The method D is preferably used because it has a high film formation rate and can form a silicon oxide layer at a high speed.

In the sputtering method, the RF magnetron sputtering method using silicon dioxide as a target and an inert gas such as argon as a sputtering gas is preferably used. As will be described later, since the sputtering method is preferably used for forming the transparent conductive layer that is the second layer in the two-layer structure of the present invention, the same vacuum as that for forming the silicon oxide layer that is the first layer is used. Since the film can be continuously formed in the room, this can also be suitably used.

The coating method is a simple step of coating the silazane polymer in the air and heating and drying at 150 to 500 ° C. for 0.5 to 5 hours. Further, unlike the above film forming method, a vacuum device is used. This is also preferably used since the desired silicon oxide layer can be obtained with a simple device because it is not necessary. As the silazane polymer used in the coating method, for example, polysilazane (manufactured by Tonen Corporation) can be used.

The thickness of the silicon oxide layer is 60 to 500 nm,
It is more preferably 70 to 400 nm, and even more preferably 100 to 300. If the silicon oxide layer is too thin, the abrasion resistance will not be improved even if a transparent conductive film is produced by forming a transparent conductive layer as a second layer on the silicon oxide layer. If the thickness of the silicon oxide layer exceeds this, the silicon oxide layer will be cracked when the film is rolled up. It is of course possible to set the thickness to a larger value, but a practically sufficient abrasion resistance can be obtained with a silicon oxide layer having a thickness of 500 nm, so that it takes no time to form the film and the silicon oxide layer is meaninglessly thickened. Is not preferable.

It will be easily understood by those skilled in the art that the term "silicon oxide" as used herein is a generic term for oxidized silicon and does not necessarily have to be stoichiometric. That is, more specifically, the atomic ratio of oxygen to silicon is in the range of 1.5 to 2,1. Also,
Needless to say, even if impurities such as nitrogen and hydrogen are contained, they are included in the range of silicon oxide.

In the present invention, after the silicon oxide layer is formed as described above, the transparent conductive layer is further formed thereon. For this transparent conductive film, an oxide semiconductor such as indium oxide (ITO) containing tin oxide, stannic oxide, or zinc oxide can be used. Among them, indium oxide containing tin oxide is more preferably used because it is excellent in transparency and electric conductivity.

As a film forming method of the transparent conductive layer, any of conventionally known physical vapor deposition methods such as a vacuum vapor deposition method, a sputtering method and an ion plating method can be adopted.

In the sputtering method, a direct current (DC) or radio frequency (RF) magnetron sputtering method using indium oxide containing 2 to 50% by weight of tin oxide as a target and an inert gas such as argon as a sputtering gas is used. it can. In addition, in order to increase the transparency and conductivity of the transparent conductive layer, 0.1 to 20% in the sputtering gas.
Oxygen gas may be mixed to some extent. Further, a direct current or high frequency reactive sputtering method using a tin-indium (tin mixing ratio: 2 to 50% by weight) alloy as a target, an inert gas such as argon as a sputtering gas, and an oxygen gas as a reactive gas is also suitable. Available for In this method, the transmittance and conductivity of the transparent conductive layer are very sensitively affected by the partial pressure of the oxygen gas which is a reactive gas, and therefore it is necessary to strictly control them. For example, if the oxygen / argon fraction is 0.
Any of the above-mentioned sputtering methods of about 1 to 0.2 can be suitably used because a transparent conductive layer excellent in transparency and conductivity can be easily obtained.

The thickness of the transparent conductive layer is preferably 20 to 100 nm. If a transparent conductive layer having a film thickness in this range is formed, its surface electric resistance is 200 to 10
It becomes 00Ω / □, and a transparent conductive film that can be suitably used as an electrode of a touch panel is obtained. When a touch panel is formed by using a transparent conductive film having a surface electric resistance of less than 200Ω / □, power consumption increases, which is not preferable. Also, the surface electric resistance is 1
When a touch panel is formed by using a transparent conductive film having a thickness of more than 000Ω / □, it is not preferable to use it as an electrode of the touch panel in terms of position detection accuracy.

The transparent conductive film obtained by the above method may be subjected to heat treatment (annealing) in order to improve the environmental resistance. The heat treatment temperature is usually 100 to
It is about 200 ° C.

The atomic composition of the silicon oxide layer and the transparent conductive layer formed by the above method is determined by Auger electron spectroscopy (A
ES), inductively coupled plasma method (ICP), Rutherford backscattering method (RBS) and the like. Further, these film thicknesses can be measured by observation in the depth direction of Auger electron spectroscopy, cross-section observation by a transmission electron microscope, or the like.

[0023]

EXAMPLES Next, the present invention will be specifically described with reference to Examples.

The center line average roughness (Ra) of the polymer film used was measured with a surface roughness measuring instrument SE-30D manufactured by Kosaka Laboratory Ltd.

Example 1 Polysilazane was applied to one surface of a polyethylene terephthalate film (thickness 100 μm) having a center line average roughness of 0.05 μm, and dried at 170 ° C. to form a 400 nm silicon oxide layer. Formed. On top of that, a tin-indium (weight ratio 5:95) alloy target,
Argon gas was used as the sputtering gas and oxygen gas (flow ratio, argon: oxygen = 10: 6) was used as the reactive gas.
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron reactive sputtering method under an atmosphere of 3 mTorr to obtain a transparent conductive film.

Example 2 On one surface of a polyethylene terephthalate film (thickness 188 μm) having a center line average roughness of 0.05 μm, 1,
A 200 nm silicon oxide layer was formed by a plasma CVD method using 1,3,3-tetramethyldisiloxane gas and oxygen gas as raw materials. A tin-indium (weight ratio 5:95) alloy target was used on top of that, an argon gas was used as the sputtering gas, and an oxygen gas (flow ratio, argon: oxygen = 10: 6) was used as the reactive gas under an atmosphere of 3 mTorr. Then, a transparent conductive layer having a thickness of 40 nm was formed by the DC magnetron reactive sputtering method to obtain a transparent conductive film.

Example 3 Polysilazane was applied to one surface of a polyethylene terephthalate film (thickness: 50 μm) having a center line average roughness of 0.10 μm and dried at 170 ° C.
A 200 nm silicon oxide layer was formed. A transparent conductive layer having a thickness of 40 nm was formed thereon by a DC magnetron sputtering method using an indium oxide target containing 5 wt% of tin oxide and under an atmosphere of 3 mTorr of argon gas containing 1% of oxygen. To obtain a film.

Example 4 Polysilazane was applied to one side of a polyethylene terephthalate film (thickness: 100 μm) having a center line average roughness of 0.05 μm and dried at 170 ° C. to form a 450 nm silicon oxide layer. Formed. Using an indium oxide target containing tin oxide of 5 wt% thereon, an argon gas containing 1% of oxygen 3 mTorr
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron sputtering method in an atmosphere of r to obtain a transparent conductive film.

Example 5 Polysilazane was applied to one surface of a polyether sulfone film (thickness: 100 μm) having a center line average roughness of 0.05 μm and dried at 170 ° C. to give 3
A 00 nm silicon oxide layer was formed. A tin / indium (weight ratio 5:95) alloy target was used thereon, an argon gas was used as a sputtering gas, and an oxygen gas (flow rate ratio, argon: oxygen = 10: 6) was used as a reactive gas.
A 40 nm-thick transparent conductive layer was formed by a DC magnetron reactive sputtering method in an atmosphere of Torr to obtain a transparent conductive film.

Example 6 A polyethylene terephthalate film (thickness 188 μm) having a center line average roughness of 0.50 μm was provided with 1,
A 65 nm silicon oxide layer was formed by a plasma CVD method using 1,3,3-tetramethyldisiloxane gas and oxygen gas as raw materials. A tin-indium (weight ratio 5:95) alloy target was used on top of that, an argon gas was used as the sputtering gas, and an oxygen gas (flow ratio, argon: oxygen = 10: 6) was used as the reactive gas under an atmosphere of 3 mTorr. Then, a transparent conductive layer having a thickness of 40 nm was formed by the DC magnetron reactive sputtering method to obtain a transparent conductive film.

Example 7 Polysilazane was applied to one surface of a polyether sulfone film (thickness 50 μm) having a center line average roughness of 0.80 μm, and dried at 170 ° C. to give 20.
A 0 nm silicon oxide layer was formed. Using an indium oxide target containing tin oxide of 5 wt% on it,
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron sputtering method in an atmosphere of 3 mTorr of argon gas containing 1% of oxygen to obtain a transparent conductive film.

Example 8 Polysilazane was applied to one surface of a polyether sulfone film (thickness 100 μm) having a center line average roughness of 0.015 μm and dried at 170 ° C.
A 200 nm silicon oxide layer was formed. A transparent conductive layer having a thickness of 40 nm is formed thereon by a DC magnetron sputtering method using an indium oxide target containing 5 wt% of tin oxide in an atmosphere of argon gas containing 1% of oxygen and 3 mTorr. A conductive film was obtained.

Comparative Example 1 A polyethylene terephthalate film (thickness 188 μm) having a center line average roughness of 0.50 μm was directly formed on one surface thereof without forming a silicon oxide layer, and tin / indium (weight ratio 5:95) was used. ) An alloy target is used as a sputtering gas for argon gas and a reactive gas for oxygen gas (flow ratio,
Using argon: oxygen = 10: 6), a transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron reactive sputtering method in an atmosphere of 3 mTorr to obtain a transparent conductive film.

COMPARATIVE EXAMPLE 2 A polyethylene terephthalate film (thickness 188 μm) having a center line average roughness of 0.50 μm was provided with 1,
A 50 nm silicon oxide layer was formed by plasma CVD using 1,3,3-tetramethyldisiloxane gas and oxygen gas as raw materials. A tin-indium (weight ratio 5:95) alloy target was used on top of that, an argon gas was used as the sputtering gas, and an oxygen gas (flow ratio, argon: oxygen = 10: 6) was used as the reactive gas under an atmosphere of 3 mTorr. Then, a transparent conductive layer having a thickness of 40 nm was formed by the DC magnetron reactive sputtering method to obtain a transparent conductive film.

Comparative Example 3 Polysilazane was applied to one surface of a polyethylene terephthalate film (thickness 100 μm) having a center line average roughness of 0.05 μm, and dried at 170 ° C. to form a 600 nm silicon oxide layer. Formed. Using an indium oxide target containing tin oxide of 5 wt% thereon, an argon gas containing 1% of oxygen 3 mTorr
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron sputtering method in an atmosphere of r to obtain a transparent conductive film.

Comparative Example 4 Polysilazane was applied to one surface of a polyethylene terephthalate film (thickness 100 μm) having a center line average roughness of 0.008 μm and dried at 170 ° C. to form a 200 nm silicon oxide layer. Formed. Using an indium oxide target containing tin oxide of 5 wt% thereon, an argon gas containing 1% of oxygen 3 mTorr
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron sputtering method in an atmosphere of r to obtain a transparent conductive film.

Comparative Example 5 Polysilazane was applied to one surface of a polyether sulfone film (thickness 50 μm) having a center line average roughness of 1.15 μm and dried at 170 ° C. to give 20.
A 0 nm silicon oxide layer was formed. Using an indium oxide target containing tin oxide of 5 wt% on it,
A transparent conductive layer having a thickness of 40 nm was formed by a DC magnetron sputtering method in an atmosphere of 3 mTorr of argon gas containing 1% of oxygen to obtain a transparent conductive film.

Next, the abrasion resistance of the transparent conductive films of Examples 1 to 8 and Comparative Examples 1 to 5 described above was measured and evaluated in the following manner. <Abrasion resistance> Using a rubbing tester manufactured by Taihei Rika Kogyo Co., Ltd., abrasion material: gauze (Japanese Pharmacopoeia type I), load: 500 g weight / cm ² , abrasion speed: 40 times under conditions of 40 cm / sec (100 (Reciprocating) After abrasion of the transparent conductive film, the surface electric resistance (R _s ) of the film is measured,
The rate of change with respect to surface resistivity of the initial film (R ₀₎ was evaluated seeking (R _S / R _0). That is, it can be said that the closer the rate of change in surface electrical resistance (R _s / R ₀ ) is to 1.0, the more transparent a conductive film with excellent resistance to wear with less resistance change due to wear. Moreover, when the transparent conductive film is used as an electrode of a touch panel as described above,
The rate of change of surface electrical resistance (R _s / R ₀ ) is required to be less than 2. The surface electric resistance (unit: Ω /
□) was measured by the four-terminal method. [Table 1] shows the evaluation results.

[0039]

[Table 1] ^{1) A} part of the silicon oxide layer was peeled off from the transparent polymer film. ^{2) The} appearance was cloudy, and sufficient transparency was not obtained.

As is clear from the results in the above table, the transparent conductive film of the present invention has very excellent abrasion resistance.

[0041]

As described above, in the present invention, at least a silicon oxide layer is formed as a first layer on one main surface of a polymer transparent film, and a transparent conductive layer is formed thereon as a second layer. By forming, it is possible to provide a transparent conductive film having excellent abrasion resistance, which can be suitably used for a touch panel electrode.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a transparent conductive film of the present invention.

[Explanation of symbols]

 10 Transparent Polymer Film 20 Silicon Oxide Layer 30 Transparent Conductive Layer

Claims (3)

[Claims] 1. A first layer (B) made of silicon oxide having a thickness of at least 60 to 500 nm and a second layer made of a transparent conductive film (at least on one main surface of the transparent polymer film (A)). C) and a transparent conductive film formed in a configuration of ABC. 2. The transparent conductive film according to claim 1, wherein the center line average roughness of the transparent polymer film is 0.01 to 1 μm. 3. The transparent conductive film according to claim 1, which can be suitably used for a touch panel electrode.