JPH04230906A - Transparent conductive laminated body - Google Patents

Abstract

PURPOSE:To provide a transparent conductive laminated body which has excellent bending resistance, chemical resistance and environment resistance and good conductivity and can be properly utilized for an electrode of a transparent touch panel, a liquid crystal display element and dispersion type electroluminescence, or an anti-static agent or a transparent planar heating element. CONSTITUTION:A thin film layer of indium oxide containing tin is formed on a transparent substrate made of a PET film, and a thin film layer of tin oxide containing antimony is formed on it to obtain a transparent conductive laminated body.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides flexibility, chemical resistance,
This relates to a transparent conductive laminate that has excellent environmental resistance and low resistance. This transparent conductive laminate can be used as electrodes for transparent touch panels, liquid crystal display elements, distributed electroluminescence, etc., as well as antistatic bodies and transparent planar heating elements. It can be suitably used for such purposes.

0002

[Prior art] Transparent conductive laminates are used for transparent touch panels,
It is widely used in electrodes for liquid crystal display devices, distributed electroluminescence, antistatic bodies, transparent heating elements, etc. Such transparent conductive laminates are produced on transparent substrates such as glass or polymer films using vacuum film-forming techniques such as sputtering and vapor deposition.
It was manufactured by forming a transparent thin film made of metal or oxide.

Known examples of such thin films include thin films of tin oxide, indium oxide, zinc oxide, cadmium oxide, indium oxide containing tin (ITO), and tin oxide containing antimony (ATO). Among these, ITO thin films are used especially when thinness and low resistance are required, and ATO thin films are used when somewhat thicker thin films or relatively high resistance are acceptable. It was getting worse.

[0004] Although ITO has particularly excellent transparency and conductivity, it has poor environmental resistance and chemical resistance, and its conductivity decreases in high temperature and humidity environments, or in acidic or alkaline atmospheres. There was a drawback. These properties can be improved by crystallizing ITO, but crystallized IT
O thin films have problems such as poor mechanical properties such as minute cracks occurring in the film due to deformation such as bending, and increased resistance.

[0005] Furthermore, JP-A-56-164852 discloses a transparent conductive laminate with improved chemical resistance and environmental resistance by providing a transparent inorganic silicon compound as a protective layer on an ITO layer. There is. However, the protective layer used here is made of transparent inorganic oxides such as titanium oxide and tin oxide, or organic silicides, and although they have excellent chemical and environmental resistance, they are not insulating. Since it was semiconductive with high resistance, it is possible to lower the resistance when directly contacting the ITO layer by inserting a pin, etc., but when energizing by just touching the surface like a touch panel, the resistance can be lowered. In this case, the protective layer acts as a barrier and the resistance becomes extremely high. Furthermore, when a multilayer film is formed in this way, cracks or peeling occur in some parts of the film due to bending, etc., resulting in an increase in resistance. On the other hand, although ATO has higher resistance than ITO, it is chemically stable and its resistance does not change much under high temperature and humidity environments, acidic/alkaline atmospheres, etc.

[0006]

[Problems to be Solved by the Invention] In view of the above circumstances, an object of the present invention is to provide a material with excellent bending resistance, chemical resistance, and environmental resistance, which incorporates the respective advantages of ITO and ATO.
Another object of the present invention is to provide a transparent conductive laminate having low resistance.

[0007]

[Means for Solving the Problems] As a result of various studies in order to solve the above problems, the present inventors have found that a transparent conductive layer can be
We discovered that the above problem could be achieved by creating a stacked structure with an ATO layer on an ITO layer instead of a single O layer.
We have arrived at the present invention. That is, the gist of the present invention is a transparent conductive laminate characterized in that a thin film layer of ITO is formed on a transparent substrate, and a thin film layer of ATO is further formed on the thin film layer of ITO.

The present invention will be explained in detail below. Examples of the transparent substrate used in the present invention include plastic films and glass plates made of polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate (PET). When properties are required, it is preferable to use a plastic film.

[0009] First, a transparent and highly conductive ITO thin film layer is formed on these substrates, and then A is deposited on this ITO thin film layer.
A thin film layer of TO is formed. As mentioned above, ITO has high conductivity but lacks stability. On the other hand, ATO has higher stability than ITO, but its conductivity is only about one-tenth that of ITO, so if you want to increase the conductivity, you have to make the film considerably thicker. As a result of various studies, we have found that by laminating an ATO layer on an ITO layer, a highly stable laminate can be obtained while maintaining excellent properties such as transparency and conductivity. That is, by laminating a highly stable ATO layer on a highly conductive ITO layer, a highly conductive and highly stable conductive laminate can be obtained. In addition, the ITO layer and A
Since the interface has good matching with the TO layer, good properties can also be obtained from this point of view.

[0010] At this time, the thickness of the ITO layer is preferably several hundred to several thousand Å from the viewpoint of conductivity.
The thickness of the layer is preferably several tens to several hundred angstroms, particularly 20 to 200 angstroms. When the thickness of the ATO layer is less than 20 Å, the effect on chemical resistance and environmental resistance is small, and when it exceeds 200 Å, the bending resistance tends to decrease.

[0011] Furthermore, the tin content in the ITO layer is
The atomic ratio of the metal elements constituting the O layer is preferably 2 to 15%. If the tin content is less than 2%, carrier generation will not be sufficient and it will be difficult to reduce the resistance sufficiently;
If it exceeds , resistance tends to increase due to a decrease in mobility.

[0012] The content of antimony in the ATO layer is A
2 to 20 atomic % of the metal elements constituting the TO layer
It is preferable that This is because in the ATO layer, when the content of antimony increases, the number of carriers increases and the specific resistance decreases, but when the content becomes excessive, the mobility of the carriers is actually inhibited due to the increase in the number of carriers, so the resistance decreases. growing. That is, when the antimony content is less than 2 at %, the effect of antimony inclusion tends to be small and the resistance tends to increase, and when the antimony content exceeds 20 at %, the resistance tends to increase, which is not preferable.

Therefore, when used in devices that recognize electrical signals simply by touching the surface, such as touch panels and resistive transparent coordinate input devices, ATO
The antimony content of the layer is set to 2 to 20 atomic % as the atomic ratio of the metal elements constituting the ATO layer, and the thickness of the ATO layer is set to several 1
The thickness is preferably 0 to several hundreds of angstroms, particularly 20 to 200 angstroms. Furthermore, as the amount of antimony increases, the hardness of the ATO layer tends to increase and the flexibility tends to deteriorate, so from this point of view as well, it is preferable that the antimony content of the ATO layer is 20 at % or less. That is, if the antimony content of the ATO layer is 20 atomic % or less, the surface of the conductive layer will be less likely to be damaged and will be easier to handle during processing.

[0014] In the transparent conductive laminate of the present invention, the ITO layer may be formed directly on the transparent base material, or an intermediate layer may be inserted between the ITO layer and the base material. By providing an intermediate layer, it is possible to improve the adhesion and surface smoothness between the ITO layer and the base material, suppress the reaction between the ITO layer and the base material, and reduce thermal expansion between the layers of the laminate. It is possible to obtain effects such as buffering the accumulation of stress and strain caused by differences in coefficients. Further, a back coat layer may be provided on the surface of the base material on which the conductive layer is not formed. Furthermore, when a soft substrate such as a polymer film is used, the back coat layer protects the transparent conductive layer and the back surface of the substrate when the obtained transparent conductive laminate is rolled up. Furthermore, if necessary for commercialization, a release layer or an adhesive layer may be provided on the back surface of the laminate via an adhesive layer.

The transparent conductive layer can be formed on the substrate by various vapor deposition methods such as vapor deposition, sputtering, and chemical vapor deposition (CVD).
By using the pressure gradient type plasma gun type ion plating apparatus disclosed in Japanese Patent No. 73770, etc., it is possible to obtain products with even more excellent characteristics (examples after Example 5). In this method, direct current plasma obtained by arc discharge is drawn out in the form of a beam using a magnetic field, and the evaporation source is irradiated with the evaporation particles, which are then evaporated and attached to the substrate to form a film. It is characterized by high ionization efficiency and is very effective in creating transparent conductive oxide thin films such as tin oxide, indium oxide, ITO, or ATO. In addition, in the composite cathode type plasma gun of the pressure gradient type plasma gun type ion plating apparatus, LaB6 is used as the main cathode for arc discharge, which has good emission efficiency of thermoelectrons and less wear and tear. In addition, the discharge chamber is approximately 1 torr
On the other hand, the deposition chamber has a high vacuum of about 10-3 torr or less, so there is less back-diffusion of gas from the deposition chamber to the main cathode side, minimizing damage to the plasma gun and improving the equipment performance. Easy to handle. For these reasons, it can be said that a pressure gradient plasma gun type ion plating apparatus is a suitable method for forming a transparent conductive layer on a base material.

[0016]

[Examples] The present invention will be specifically explained below with reference to Examples. Examples 1 to 4, Comparative Example 1 An ITO layer was formed to a thickness of 300 Å on a 125 μm thick PET film by reactive vacuum deposition. At this time, the composition ratio of In2O3:
Using a sintered body with SnO2 = 91:9 (atomic %),
The conditions for film formation were a substrate temperature of 100°C and a film formation rate of 10 Å/min.
sec, the amounts of Ar gas and O2 gas introduced were 20 CCM and 15 CCM, respectively, and the RF output was 80 W. Further, the degree of vacuum was set to 4×10 −4 torr. Next, an ATO layer was formed on the ITO layer to a thickness of 50, 100, 150, 20 mm using the same reactive vacuum evaporation method as described above.
It was formed to have a thickness of 0 Å. At this time, the composition ratio of the vapor deposition source was SnO2:Sb2O3 =95:5 (atomic %)
Using a sintered body, the film forming conditions were a substrate temperature of 100 °C
The deposition rate was 7 Å/sec, the amounts of Ar gas and O2 gas introduced were 20 CCM and 15 CCM, respectively, and the RF output was 80 W. Also, the degree of vacuum is 4 x 10-4 tor.
It was set as r. Note that Comparative Example 1 was one in which only an ITO layer was formed without forming an ATO layer.

The characteristics of each of the obtained transparent conductive laminates were evaluated as described below. The results are shown in Table 1. (1) Parallel light transmittance: Measured at a wavelength of 550 nm using a U-3400 spectrometer manufactured by Hitachi, Ltd.

(2) Surface resistance value (Ω/□): Measurement was carried out by the four-probe method using a K-705RD four-probe surface resistance meter manufactured by Kyowa Riken.

(3) Environmental resistance: After being kept in a Yamato IH-42H constant temperature and humidity chamber adjusted to 60°C and 95% RH for 500 hours, the surface resistance value was measured in the same manner as above. The surface resistance value was compared with that before being placed in the tank. The value before input is R0, the value after extraction is R1, and R1
The value of /R0 was determined.

(4) Acid resistance: Prepare 5 pieces of each laminate, measure the surface resistance value using the method described above, soak it in 3N hydrochloric acid for 5 minutes, take it out, wash it with water, and dry it. , the surface resistance value was measured, and the number of cases where the rate of change in surface resistance value was within 10% among the five points was counted.

[0021]

[Table 1]

[0022] As is clear from Table 1, the transparent conductive laminate provided with the ATO layer is more stable under high temperature, high humidity, and acidic environments than the one consisting of a single ITO layer.

Examples 5 to 9, Comparative Example 2 An ITO layer was deposited on a PET film substrate with a width of 30 cm, a thickness of 125 μm, and a length of 500 m using an ion plating apparatus equipped with a pressure gradient type composite cathode plasma gun. 3
The film was deposited using a roll-to-roll method while adjusting the winding speed so that the film thickness was 0.00 Å. At this time, I
TO sintered body (S in the atomic ratio of metal elements constituting the oxide)
The vacuum chamber was evacuated to 2 x 10-6 torr, and 40 CCM of Ar gas was supplied from the working gas inlet of the plasma gun. O2 gas was supplied at 30 CCM from a manifold installed near the roll, and the inside of the vacuum chamber was set at 1 x 10-3 torr. Furthermore, the plasma gun has 80
A DC voltage of V, 100 A was applied, and the film formation rate was 100 Å.
/sec.

Next, the vapor deposition source was changed to an ATO sintered body (a tin oxide sintered body to which 10 atomic % of Sb was added based on the atomic ratio of the metal elements constituting the oxide), and the thickness of the ATO layer was 0 Å, 1 Å.
A laminate was produced while adjusting the winding speed of the film so that the thickness of the film was 0 Å, 20 Å, 100 Å, 200 Å, and 300 Å. At this time, 40 CCM of Ar gas was supplied from the working gas inlet of the plasma gun, and 80 CCM of O2 gas was supplied from the manifold installed near the main roll in the vacuum chamber. A DC voltage of 80 V and 100 A was applied. In addition, A
Comparative Example 2 was prepared in which the thickness of the TO layer was 0 Å.

The surface resistance values of the obtained laminate and the surface resistance values under the following various conditions were measured. The results are shown in Table 2.

(5) Surface resistance value: The surface resistance value (Ω/□) was determined by the four-probe method using a four-probe surface resistance meter K-705RD manufactured by Kyowa Riken. Surface resistance value by two-probe method (
Ω) is a digital multimeter TR manufactured by Advantest.
-6871 was used. At this time, if there was good electrical contact between the stylus and the sample, the condition was such that the value measured by the two-probe method was approximately twice that of the four-probe method. That is, the measurement was performed with a distance between the probes of 18 mm.

(6) Acid resistance: The sample was immersed in a 1N hydrochloric acid aqueous solution for 5 minutes, and the change in surface resistance before and after immersion was measured.

(7) Environmental resistance: Using a Yamato IH-42H constant temperature and humidity chamber, the change in surface resistance was measured by the four-probe method when the sample was exposed to an environment of 95% humidity and 60°C. .

(8) Flexibility: Cut the sample into a strip of 10 cm long and 3 cm wide, and one short side of the strip was 9 mm in diameter.
A weight of 200 g was suspended from the other end of the sample, and the cylindrical rod was manually rotated clockwise to wind the sample. Changes in surface resistance were measured using the four-probe method after repeating the process 10 times. It was measured.

[0030]

[Table 2]

[0031] From these results, the following things became clear. In the four-point probe method, even if the thickness of the ATO layer changes, the measured value does not change much and remains approximately 200.
It was Ω/□. On the other hand, the results measured by the two-probe method show that when the thickness of the ATO layer is 0 Å, 10 Å, and 20 Å, it is approximately 40 Å.
0Ω, but at 200Å it was 800Ω, and at 300Å it was 2
The resistance was extremely large, 000Ω. This indicates that the electrical contact between the stylus and the ITO layer of the laminate worsens as the ATO layer becomes thicker, since the two-probe method measures point contact with very small stylus pressure. There is. In particular, when the film thickness exceeded 200 Å, the resistance increased significantly. As described above, if the thickness of the ATO layer exceeds 200 Å, the resistance at the time of contact becomes very large, which causes a problem when contact is made by contact, such as in a touch panel.

[0032] In case of only ITO layer without ATO layer, 1N
When the ITO layer was immersed in an aqueous hydrochloric acid solution for 5 minutes, it was completely etched and became an insulator. On the other hand, those with an ATO layer can suppress etching by hydrochloric acid, but
When the film thickness was 10 Å, the surface resistance was 11.5 times that before dipping, which was a very large change. However, as the ATO layer becomes thicker, the change in surface resistance decreases, and
At 100 Å or more, it was 2.2 times or less, and there was almost no change at 1.2 times or less. As described above, the thicker the ATO layer is, the better the acid resistance is, and this effect becomes particularly noticeable at a thickness of 20 Å.

Furthermore, the surface resistance of an ITO layer without an ATO layer after 500 hours under high temperature and high humidity conditions is 1.
The conductivity decreased by 5 times. By forming the ATO layer on the ITO layer, the change in surface resistance becomes smaller and the ATO layer becomes smaller.
When the thickness of the TO layer was 10 Å, it was 1.35 times, when it was 20 Å, it was 1.2 times, and when it was 100 Å or more, it was 1.05 times even after 1000 hours, so almost no change in resistance occurred.

[0034] In the results of the bending resistance test, the surface resistance of the laminate having only an ITO layer without an ATO layer did not change even after the bending test. Even if an ATO layer is provided, if the thickness of the ATO layer is less than 200 Å, the change will be 1.1
Although it is small, less than twice that, it is about 3.3 times larger in the case of 300 Å. Generally, when such a bending process is applied, the thicker the film, the more likely it is that cracks will occur, and especially when the film is hard like an ATO layer, there is a critical thickness between 200 Å and 300 Å at which the film is more likely to crack. Conceivable. From the above results, we found that the thickness of the ATO layer on the ITO layer should be 20~20~
200 Å increases bending resistance, chemical resistance (especially acid resistance),
It is possible to create a transparent conductive thin film that has excellent environmental resistance (particularly moisture and heat resistance) and low resistance even in point contact.

Examples 10 to 12 Next, by changing the antimony composition of the ATO sintered body of the vapor deposition source, ATO layers with different antimony contents were formed.
Formed on the TO layer to create a laminate, Examples 5 to 9,
A test similar to that performed in Comparative Example 2 was conducted. The results are shown in Table 3.

[0036]

[Table 3]

[0037] This result shows that the resistance increases whether the antimony content in the ATO layer is too small or too large. In addition, similar results were obtained in bending tests and heat-and-moisture tests.

[0038]

[Effects of the invention] The transparent conductive laminate of the present invention has excellent bending resistance and
Excellent chemical resistance, environmental resistance, and low resistance. Therefore, this transparent conductive laminate can be used as an electrode for transparent touch panels, liquid crystal display elements, distributed electroluminescence, etc.
Alternatively, it can be suitably used for antistatic bodies, transparent heating elements, and the like. In addition, especially in cases where electricity is supplied by simply touching the surface of the panel, such as a touch panel,
When the content of antimony in the ATO layer is set to 2 to 20 atomic % in terms of the atomic ratio of the metal element, and the film thickness is set to 20 to 200 Å, a low resistance layer can be obtained.

Claims (1)

[Claims] [Claim 1] A transparent conductive material comprising: a thin film layer of indium oxide containing tin formed on a transparent substrate; and a thin film layer of tin oxide containing antimony further formed on the thin film layer of indium oxide containing tin. laminate.