JPH1110780A - Transfer arent conductive laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent conductive coat which shows an insignificant change in a surface resistance value even under the effects of thermal treatment and can be applied to a use requiring thermal treatment during fabrication. SOLUTION: This transparent conductive laminate has a transparent conductive coat composed mainly of at least, indium, tin and oxygen, formed on one of the main faces of a transparent substrate. When the content of carbon in the transparent conductive coat is N0 (atoms/cm<3> ) and the content of carbon after thermal treatment at 120 deg.C in an atmosphere for six hours or more is N1 (atoms/cm<3> ), it is established that N1 /N0 is 1.0 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive laminate formed by forming a transparent conductive film mainly composed of indium, tin and oxygen on a transparent substrate.
The present invention relates to a transparent conductive laminate which has excellent electric durability and can be suitably used as a transparent electrode of a dispersion-type EL element in addition to a liquid crystal display, a touch panel, and the like.

[0002]

2. Description of the Related Art In recent years, as society has become highly computerized, optoelectronics-related components and equipment have remarkably advanced and spread. Among them, the transparent conductive laminate is used as an electrode of an input device such as a transparent touch panel, and as a transparent electrode of a liquid crystal display, an EL (electroluminescence) luminous body, an EC (electrochromic) display, and a solar cell. Window electrodes of photoelectric conversion elements such as
Widely used such as electromagnetic shielding films for electromagnetic wave shielding.

[0003] The transparent conductive film is usually formed on the surface of a transparent substrate, is a thin film that transmits visible light and has conductivity. Conventionally known transparent conductive films include gold,
A thin film formed of a metal such as silver, platinum, palladium or the like to such a degree that the transparency is not lost;
There are an oxide semiconductor thin film having a wide energy gap, such as tin and zinc oxide, and a multilayer thin film formed by laminating a metal oxide and a metal. A metal thin film has excellent conductivity but poor transparency. The multilayer thin film is excellent in transparency and conductivity, but the lamination process is complicated. On the other hand, the oxide semiconductor thin film is slightly inferior in conductivity but is excellent in transparency. Among oxide semiconductor thin films, a thin film including indium, tin, and oxygen (hereinafter, also referred to as an ITO (Indium Tin Oxide) film) has particularly excellent conductivity and transparency, and can be etched with an acidic solution. Since it can easily form an electrode pattern, it is widely used. The resistivity of the ITO film is usually 5 × 10 ⁻⁵ to 1 ×.
A visible light transmittance of about 10 ⁻³ Ω · cm and a light transmittance of about 80% to 90%, which generally depends on the film thickness, have been put to practical use.

[0004] In order to evaluate the performance of a transparent conductive film, in addition to basic physical properties such as electric resistance and visible light transmittance, heat resistance and moisture resistance, and the durability of the conductive film during energization because it is often used by passing an electric current, are used. It is necessary to evaluate the performance required for practical use when a transparent conductive film is actually used as a transparent electrode, such as performance. The transparent conductive film is rarely used alone, and is ultimately often used as a transparent electrode of an electric product such as a liquid crystal display or a touch panel. It is required for the transparent conductive film that the performance of the transparent conductive film does not change in a heat treatment step or an etching step using a chemical during the manufacture thereof. Furthermore, like the EL luminous body,
When the transparent conductive film is used in contact with another substance such as a light-emitting material, the performance of the transparent conductive film must not change even when the transparent conductive film comes into contact with the substance. Also, if the change in the transparent conductive film with time seems to be large, it also affects the life of the electric product itself in which the transparent conductive film is incorporated as the transparent electrode.

[0005] When an ITO film is used as the transparent conductive film, the electrical resistance usually changes sensitively depending on the amount of oxygen in the film, and there is a concern that the electrical resistance greatly changes due to heat treatment or wet heat treatment. is there. As a means for solving such a problem, there is a method of crystallizing and stabilizing an ITO film. As a method of crystallization, generally, I
There are a method of forming a TO film in a state where the temperature of the base is raised, and a method of subjecting the once formed ITO film to a heat treatment to crystallize it.
No. 36, JP-A-1-100260, JP-A-2
-194943, JP-A-2-276630 and the like. In order to crystallize the ITO film into a stable thin film as described above, any method requires a heat treatment.

The temperature at which the ITO film crystallizes depends on the film forming method and the film forming conditions, but is usually 180 ° C. or higher. A crystalline ITO film formed by heat film formation or heat treatment after film formation is usually composed of crystallites (grains) having a diameter of several μm to several tens μm. Because there are many boundaries, the gas in the atmosphere can easily penetrate therefrom, and the wet heat resistance decreases. In order to prevent this, it is necessary to increase the size of crystallites, and for that purpose, it is necessary to increase the film formation temperature or the heat treatment temperature after film formation. Heat treatment is effective.

However, there is a case where the heat resistance of the transparent substrate is low or the heat for sufficiently crystallizing the ITO film cannot be applied due to the heat resistance of the film forming apparatus. A typical example is a case where a polymer molded product is used for a transparent substrate. The heat-resistant temperature of a general-purpose polymer molded product is lower than the temperature at which the ITO film is sufficiently crystallized.

[0008]

The ITO film, which is a typical example of a transparent conductive film, has excellent conductivity and transparency and is already widely used at present. However, its disadvantages are heat resistance and moisture resistance. I have already mentioned that there are concerns about practical performance. Transparent conductive film for touch panel, liquid crystal display,
In order to use it as a transparent electrode of an EL luminous body, an EC display, or the like, heat treatment is performed in any case in order to combine it with another member. For example, when used in touch panels, heat treatment is required when printing spacers, hardening the adhesive for bonding to the counter electrode, bonding to the terminal for taking out the electrode, etc. When a body is manufactured, heat treatment is required when forming an alignment film on a transparent conductive film. In the case of manufacturing a dispersion-type EL element, a light-emitting layer must be formed on a transparent conductive film. In such a case, a heat treatment is essential.

During the heat treatment, if the electrical characteristics of the transparent conductive film change and the surface resistance increases, power is intensively consumed in the area where the surface resistance is increased, and the power of the area is increased. The transparent conductive film generates heat and further causes a disconnection, resulting in E
A defect occurs in which the L element locally emits no light. Especially,
Such a problem occurs when light emission is performed in a state where the driving voltage and the driving frequency are increased in order to increase the luminance of the dispersion type EL element.

Therefore, as a means for preventing the performance of the ITO film from being changed by the heat treatment, the above-mentioned methods such as crystallization of the ITO film and lamination with a protective film have been proposed. Depending on the transparent substrate, its temperature has an upper limit and a sufficiently stable ITO film cannot be obtained, or when a protective film is laminated, another material is prepared.
The formation process must be performed separately from the formation of the TO film.

In view of the above circumstances, the present invention forms an ITO film without performing heat treatment during film formation,
An object of the present invention is to obtain a transparent conductive film in which the O film itself has high stability and does not change its performance even if a heat treatment process is performed later without forming a protective film or the like. Such an ITO film is particularly suitable for dispersion type EL.
When used as a transparent electrode of an element, the generation of a non-light emitting portion is significantly suppressed, so that a long life can be realized. In addition, the reliability of electrical products that require a process of heating a transparent conductive film such as a touch panel, a liquid crystal display, or an EC display can be improved.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that a thin film mainly composed of indium, tin and oxygen is formed on one main surface of a transparent substrate. By forming the (ITO film) whose carbon content does not decrease by the heat treatment, and by controlling the carbon content in the film to 8 × 10 ²⁰ (atoms / cm ³ ) or less, a transparent film having excellent heat resistance is obtained. The inventors have found that a conductive film can be obtained, and have reached the present invention.

That is, the present invention provides:
At least mainly indium and tin
A transparent conductive laminate formed with a transparent conductive film composed of oxygen
And the carbon content in the transparent conductive film is N₀(Atom
s / cm^Three), 120 ° C in air, 6 hours or more
The carbon content after heat treatment is N₁(Atoms / cm^Three)When
When you do, N₁/ N₀Is 1.0 or more
A transparent conductive laminate, (2) containing carbon in the transparent conductive film.
Amount (N₀) Is 8 × 10²⁰(Atoms / cm ^Three)Less than
(1) The transparent conductive laminate according to (1),
(3) The transparent substrate is a transparent polymer molded product.
The transparent conductive laminate according to (1) or (2),
(4) Used for transparent electrode of dispersion type EL element
(1) The transparent conductive laminate according to any one of (1) to (3),
It is about.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a transparent conductive laminate of the present invention has a transparent conductive film mainly composed of indium, tin and oxygen (ITO) on one main surface of a transparent substrate 10. 20 and the carbon content in the transparent conductive film was N ₀ (atoms / cm ³ ), and the carbon content after heat treatment in air at 120 ° C. for 6 hours or more was N ₁
(Atoms / cm ³ ), N ₁ / N ₀ is 1.0
And the carbon content (N ₀ ) in the film is preferably 8
× 10 ²⁰ (atoms / cm ³ ) or less.

The ITO film does not reduce the amount of carbon in the film even when heat-treated, and has a sufficient heat resistance for practical use even if it is not crystallized if the carbon content is low, and thus the touch panel and the liquid crystal display Since the basic characteristics such as the electric resistance value and the visible light transmittance do not change even through the heat treatment step when manufacturing the body, the EL luminous body, and the EC display body, they can be suitably used as these transparent electrodes.

Further, since there is no need to crystallize the ITO film, there is no need to apply heat during the formation of the ITO film, which facilitates the production. A conductive film can be obtained. Further, in the present invention, since the stability of the ITO film itself is improved, it is not particularly necessary to laminate a protective film or the like. Of course, other materials may be laminated to further improve the reliability. In such a case, the reliability of the ITO film itself is improved, and excellent stability is obtained by forming a protective layer. Will be done.

First, a general method for forming an ITO film will be described. A coating method in which a metal organic material coating solution containing indium is applied on a transparent substrate surface and heated and baked, a vapor deposition method in which an indium oxide / tin oxide raw material is heated and evaporated in a vacuum vessel to deposit on the substrate surface, 2. Description of the Related Art There is known a sputtering method and the like in which an ionized inert gas collides with a raw material of indium oxide and tin oxide in a container to deposit atoms which fly out on a transparent substrate surface. The coating method requires a high baking temperature and can be used when the transparent substrate is glass, but cannot be used for a polymer molded product because the transparent substrate is deformed. Since heat treatment is not necessarily required in the vapor deposition method and the sputtering method, an ITO film can be formed not only on glass but also on the surface of a polymer molded product. In the vapor deposition method and the sputtering method, indium tin metal is used as a raw material, and oxygen is mixed with an inert gas in a vacuum vessel and oxidized during film formation to form an ITO.
A technique for obtaining a film is also effective. Among them, the sputtering method is the most suitable method because a highly conductive ITO film can be obtained.

The sputtering method will be described in further detail. First, a mixed sintered body of indium oxide and tin oxide is placed as a target in a vacuum vessel, a transparent substrate is placed at a position opposite to the sintered body, and the inside of the vessel is evacuated. For example, there is a method in which argon is introduced into a vacuum vessel, ionization is performed by applying a voltage, and the gas is made to collide with a target to eject target atoms and deposit them on a substrate. An appropriate amount of oxygen may be mixed into the gas to control the amount of oxygen in the ITO film.
Also, using an indium tin alloy for the target,
Sputtering is performed in a gas containing an appropriate amount of oxygen, and indium and tin are oxidized while forming a film to form ITO.
A membrane may be obtained. The feature of the sputtering method is that the amount of oxygen can be finely controlled. Since the conductivity of the ITO film changes greatly depending on the amount of oxygen in the film, the ability to finely control the amount of oxygen means that the conductivity of the film can be finely controlled. Suitable for stable production.

Although it has been described that an ITO film formed by a film forming method using a vacuum container can form a transparent conductive film having a high conductivity and a low resistance value, the resistance value increases when a heating process is performed later. Sometimes. The extent to which the resistance value increases varies depending on the transparent substrate and production lot, and it is not possible to check whether the increase in the resistance value is within the allowable range without heat treatment. It was difficult to form a stable ITO film.

The inventors have found that ITO in the heating process
It has been found that the increase in the resistance of the film is caused by the fact that a large amount of carbon is mixed in the ITO film, and that the heat treatment changes the amount of carbon, thereby causing a change in the resistance value. Carbon in the ITO film has been reduced by the heat treatment, that is, it has escaped from the film, suggesting that the decrease in the amount of carbon has led to an increase in the resistance value. The ITO film, which originally has a high carbon content, is a brittle conductive film that easily loses its carbon and has unstable performance.

In view of the above, as a means for forming an ITO film having stable performance, it is sufficient to prevent carbon in the transparent conductive film from coming out of the film even after heat treatment. That is, it is only necessary to reduce the amount of carbon that is originally present. If the carbon content in the transparent conductive film is originally small, carbon does not escape even after the heating process, and an ITO film having stable performance can be obtained. Since carbon easily escapes from the transparent conductive film and does not easily enter the transparent conductive film from the outside, once the transparent conductive film having a low carbon content is formed, an ITO film stable against heat treatment can be obtained.

The transparent conductive film of the present invention has a carbon content of N ₀ (atoms / cm ³ ) and a carbon content of 12% in the air.
The carbon content after heat treatment at 0 ° C. for 6 hours or more is calculated as N ₁ (at
oms / cm ³ ), N ₁ / N ₀ is 1.0 or more. The heat treatment of the present invention assumes a heat treatment required when the transparent conductive laminate of the present invention is used as a transparent electrode of a dispersion-type EL element.
This is performed to check whether the carbon content in the O film increases or decreases particularly. By this heat treatment, an ITO film whose carbon content is reduced, that is, N ₁ /
Those having an N ₀ of less than 1.0 cannot be preferably used as a transparent electrode of a dispersion-type EL element. Therefore, in the present invention, the condition for examining the increase or decrease of the carbon content in the ITO film due to the heat treatment may be carried out in accordance with the heating condition, and may be carried out at 120 ° C. for 6 hours or more in the air.

Next, a method of reducing carbon contamination in the ITO film will be described. The fact that carbon is mixed in the ITO film is mainly taken in during the film formation, and the form is often a volatile organic substance. In a film formation method using a vacuum vessel, the inside of the vessel is first evacuated and then film formation is started, but it is inevitable that a certain amount of gas remains. This residual gas is considered to be generated from the inner wall of the vacuum vessel, the target, the base material, and the like, in addition to the residual air. Above all,
The effect of gas release from the target and the substrate, which are members brought in from outside to the inside of the vacuum vessel, is large. Especially, since the substrate is replaced every production and installed in the vacuum vessel, the amount of gas release is considered to be large. Can be When a polymer molded product is used as the base material, the polymer itself contains a molten organic component, so that when placed in a vacuum vessel, the organic component is volatilized and an organic gas containing carbon is produced. It is likely to be released.

In order to reduce the carbon content in the ITO film, it is sufficient to form the film in such a manner that the residual gas and the released gas in these vacuum vessels are reduced as much as possible. For example, (1) elongate the evacuation time of the vacuum vessel, (2) use a material with less gas adsorption for the inner wall of the vacuum vessel, (3) heat and degas the target before film formation, (4) The substrate is heated and degassed before film formation,
(5) Increasing the film forming speed. (1) reduces the amount of residual gas, (2) to (4) reduces the amount of gas released from an object placed in a vacuum vessel, and (5) captures carbon during film formation. This is to avoid giving time.

In (1), it takes time to exhaust air,
Organic gas components released from the substrate etc. in the vacuum vessel
And reduce the pressure to 1 ×
10 ^-FiveIt is preferable to exhaust the gas until the pressure becomes Torr or less.
In (2), the inner wall of the container is made of a material to which gas does not easily adhere.
Vacuum containers for ultra-high vacuum are commercially available.
It is possible to use. In (3), the target
When heating, it affects the target and surrounding fixing members
It is sufficient to evacuate while performing at a temperature within the range where there is no.

The most important of the methods (1) to (5) is that, in the method (4), the gas released from the base material is most easily taken into the film. Is preferred. In particular, when the base material is a polymer molded product, a large amount of volatile organic components are released from the base material, and it is preferable to sufficiently perform this treatment. It should be noted that when heating the polymer molded body as the base material, the heating temperature is limited to the heat-resistant temperature of the polymer material. The heating temperature of the substrate is preferably as high as possible in order to efficiently achieve the purpose of degassing.
If possible, the temperature is preferably 120 ° C. or higher. However, if the polymer molded body is heated to a temperature higher than the heat-resistant temperature, it will be deformed and cannot be used as a base material. For example, when the material of the polymer molded body is polyethylene terephthalate or polycarbonate, the upper limit is about 150 ° C. The atmosphere when heating these substrates may be in the air,
A reduced-pressure atmosphere is preferred for efficient degassing. By performing heat treatment in a reduced-pressure atmosphere, the treatment time can be shortened without increasing the heating temperature.

The present invention relates to an ITO film having a carbon content of 8 × 10 ²⁰ (atoms / cm ³ ) or less, which is formed by the above-described method, and is a stable ITO film having a small resistance change due to heat treatment. It is.

Next, a method for measuring the carbon content in the film will be described. Since carbon in the film is not usually intentionally contained, but is incorporated into the film as an impurity, the amount of carbon is smaller than that of indium, tin, and oxygen, which are basic elements constituting the film. Means for measuring the trace carbon content include secondary ion mass spectrometry (SIMS: Sec).
onion Ion Mass Spectros
copy) can be adopted. This method irradiates primary ions to the surface of the sample to be measured, then measures the energy of secondary ions emitted from the sample at that time, counts the number of elements in the sample, and determines the content of the elements by counting the number of elements. This is a method for measuring, and the composition of the sample to be measured can be known. The feature of this method is that the sensitivity is extremely high, and it is possible to detect even a trace amount of impurities. Further, when the measurement is performed while shaving the measurement sample from the surface by using it in combination with the ion etching apparatus, the composition change from the surface to the inside of the sample can be known.

When measured by the SIMS method, the content of carbon (atoms / cm ³ ) is determined by detecting the number of secondary ions generated from carbon and counting the number of secondary ions (counts / s).
ec). Therefore, it is necessary to obtain a conversion constant (referred to as a relative sensitivity coefficient) for converting the number of counted secondary ions into a carbon content.
Therefore, prior to the measurement, a known amount of carbon ions is implanted into the ITO film, and the carbon content of the ITO film is measured by the SIMS method. Here, since the amount of carbon contained in the ITO film is known, the relative sensitivity coefficient with the number of measured secondary ions can be determined. Once the relative sensitivity coefficient is determined, the conversion from the number of secondary ions of carbon measured by the SIMS method to the carbon content can be calculated by multiplying the number of secondary ions by the relative sensitivity coefficient.

As described above, when the depth direction distribution of the carbon content in the ITO film is taken, the carbon content is abnormally large in the depth range of 0.01 μm from the surface as compared with other regions. Has become. This is because, after forming the ITO film, the carbon compound contained in the air adheres to the surface because it is once taken out to the atmosphere, and this is what was taken into the film during the formation of the ITO film. is not. This is also true of the vicinity of the interface between the transparent substrate and the ITO film. In the range of 0.01 μm from the interface, the constituent elements of the transparent substrate itself may be detected. Therefore, in the present invention, I
The carbon content in the TO film is 0.0% from the surface of the ITO film.
1 μm or more deep from the interface between the transparent substrate and the ITO film.
A value in a region separated by 01 μm or more is adopted. Although there is a distribution of the carbon content even in this region, the carbon content is 8 × 10 ²⁰ (atoms / cm ³ ) in all the regions in this region.
It is preferable to be as follows.

This will be described with reference to FIG. Where 10
Is a transparent substrate, and 20 is an ITO film. In addition, 2
1 is a surface area within 0.01 μm from the surface of the ITO film,
Reference numeral 29 denotes an interface region within 0.01 μm from the interface between the transparent substrate and the ITO film, and the other region of the ITO film 25 is an ITO film region adopting the carbon content in the present invention.

The tin content relative to indium is 3-50.
% By weight is preferred. By containing tin, carrier electrons in the ITO film are generated, and the conductivity can be increased. If the content of tin is too small, the number of carrier electrons decreases and the electrical conductivity decreases. Conversely, if the tin content is too high, the tin atoms hinder the transfer of carrier electrons, and the conductivity is reduced. That is, in order to obtain an ITO film having high conductivity, the tin content with respect to indium is preferably 3 to 50% by weight.

The indium, tin, and oxygen ratios of the transparent conductive film formed by the above method can be measured by SIMS, as well as Auger electron spectroscopy (AE).
S), inductively coupled plasma method (ICP), Rutherford backscattering method (RBS) and the like. These film thicknesses can be measured by observation in the depth direction of Auger electron spectroscopy, cross-sectional observation by a transmission electron microscope, or the like.

The transparent substrate used in the present invention only needs to be transparent to visible light, and a molded product of an inorganic compound such as glass or quartz, or a molded product of an organic polymer can be used. Above all, the polymer molded article is light and hard to be broken, so that it can be more suitably used. Specifically speaking, the transparent polymer molded product that can be used here is polyethylene terephthalate,
Examples include polyethersulfone, polystyrene, polyethylene-2, polyethylene naphthalate, polyarylate, polyetheretherketone, polycarbonate, polypropylene, polyimide, and triacetylcellulose. These transparent polymer molded products may be in the form of a plate or a film.

When a plate-shaped polymer molded product is used as a transparent substrate, it is excellent in dimensional stability and mechanical strength, so that it is excellent in dimensional stability and mechanical strength. Can be obtained, and particularly when it is required, it can be suitably used. The transparent polymer film has flexibility, and when it is used as a transparent substrate, a bendable transparent conductive film can be obtained. Further, since the thickness of the polymer film is smaller than that of the plate-like molded product, the thickness of the transparent conductive laminate can be reduced. Furthermore, since a flexible polymer film can form a transparent conductive film continuously by a roll-to-roll method, when this is used, a transparent conductive film that efficiently forms a transparent conductive film is used. Since the laminate can be mass-produced, it can be suitably used. In this case, the thickness of the film is usually 10 μm to 250 μm.
m. When the thickness of the film is less than 10 μm, the mechanical strength as a base material is insufficient, and when it exceeds 250 μm, the film is insufficient in flexibility and is not suitable for use by winding the film around a roll.

Among the transparent polymer molded products, polyethylene terephthalate is more preferably used because it has excellent transparency and processability. Further, polyethersulfone is excellent in heat resistance, so that it can be more suitably used particularly when heat treatment at a high temperature or when used under high temperature conditions.

These transparent substrates are preliminarily subjected to an etching process such as a sputtering process, a corona process, a flame process, an ultraviolet irradiation, an electron beam irradiation, etc., or an undercoating process, and are formed mainly on indium, tin and oxygen. May be applied to improve the adhesion of the transparent conductive film made of Before forming the transparent conductive film, dust-proofing treatment such as solvent cleaning or ultrasonic cleaning may be performed as necessary.

In order to enhance the adhesion between the transparent substrate and the transparent conductive film, a metal thin film layer having a thickness that does not impair the transparency may be inserted between the substrate and the film. In particular, when a polymer film is used as the transparent substrate to obtain a bendable transparent conductive film, this is an effective means because the bend resistance can be improved. Since the metal thin film layer is in contact with the ITO film, it is expected that the metal thin film layer is actually almost a metal oxide, but its effect is not affected. Specific examples of metal materials that can be used include nickel, chromium, gold, silver, zinc, zirconium, titanium, tungsten, tin, palladium, and the like, and alloys composed of two or more of these materials. The thickness of the layer may be a thickness that does not significantly impair transparency, and is preferably 0.02 nm.
About 10 nm. In order to improve transparency and release of gas from the substrate during heat treatment, to prevent precipitation of components, etc.
An appropriate thin film layer other than the metal thin film layer may be inserted between the transparent substrate and the transparent conductive film. In the case of a metal thin film layer, if the thickness is small, a sufficient effect of improving the adhesion cannot be obtained, and if it is too thick, transparency is impaired. As a method for forming the metal thin film layer, a conventionally known thin film forming method can be mentioned, and specifically, a sputtering method, a vacuum evaporation method, and the like are suitable methods. In particular, the sputtering method is a method preferably used for forming a transparent conductive film to be laminated after forming the metal thin film layer, so that the two layers can be laminated by the same apparatus, so that the production efficiency is improved. it can.

For the purpose of improving the mechanical strength, a transparent hard coat layer may be provided on the surface of the transparent substrate opposite to the surface on which the ITO film is formed, or the electrical resistance, the transparency, and the like may be increased.
An optional protective layer may be further provided on the ITO film in order to improve environmental resistance and wettability. Preferred materials for the protective layer include various metal materials, for example, aluminum,
Examples include copper, tin, titanium, palladium, gold, platinum, and the like; oxides such as silicon oxide, titanium oxide, aluminum oxide, tin oxide, and zinc oxide; and nitrides such as silicon nitride and titanium nitride. These may be used properly according to the purpose of use of the ITO film.

As described above, the transparent conductive laminate of the present invention can be formed. Next, a dispersion type EL device using the transparent conductive laminate obtained by the present invention will be described. E
The L element has a configuration in which a light emitting layer, a dielectric layer, and a back electrode are laminated on a transparent electrode formed on the surface of a transparent substrate, and emits light by applying an AC electric field between the transparent electrode and the back electrode. The layer emits light. The dispersion-type EL element is called a dispersion-type EL element because the light-emitting layer has a structure in which a phosphor powder is dispersed in a binder resin. The phosphor powder mainly uses zinc sulfide. For the dielectric layer, the same binder resin as that used for the light emitting layer is usually used, but other materials may be used. ITO film on the transparent electrode,
For the back electrode, a conductive paste containing carbon and silver as main components is used. Further, a metal foil such as aluminum may be used for the back surface electrode. In manufacturing a dispersion-type EL element, a light-emitting layer, a dielectric layer, and a back electrode are basically applied on a transparent electrode, printed, dried, and sequentially laminated. This drying requires a heat treatment.

The main performances of the dispersion type EL device are the emission luminance and the life time. A simple means for increasing the light emission luminance is to increase the voltage and frequency of the applied AC electric field as described above, but this tends to shorten the lifetime. The term “life time” here means a dispersion type EL
This refers to the time required for the device to emit light continuously and to generate a non-light-emitting portion, that is, the time during which normal continuous light emission is performed.

The inventors of the present invention have found that the occurrence of the non-light emitting portion increases the surface resistance value of the ITO film used as the transparent electrode, and creates a portion where the power consumption is abnormally high.
It was found that the TO film was destroyed and a non-light emitting portion was generated.

In the transparent conductive film of the present invention, since the change in surface resistance due to the heat treatment is small, the above-mentioned problems relating to the ITO film do not occur, and the life of the dispersion type EL element can be extended. .

[0044]

Next, the present invention will be described in detail with reference to examples. Example 1 A polyethylene terephthalate film (thickness: 125 μm) previously heated at 120 ° C. for 24 hours in a vacuum was used as a transparent substrate in a vacuum vessel as an indium oxide / tin oxide sintered body (composition ratio In ₂ O ₃ : S
(nO ₂ = 80: 20% by weight) was installed at a position facing the target, and the inside of the vacuum vessel was evacuated to a pressure of 2.6 mPa or less by an oil rotary pump and a turbo molecular pump. Pressure 266mP
a: An oxygen partial pressure of 5.3 mPa) is introduced, a DC bias is applied between the target and the electrode to generate plasma, and sputtering is performed to form an ITO having a thickness of 0.11 μm.
A film was formed on a transparent substrate to obtain a transparent conductive laminate of the present invention.

Comparative Example 1 A non-heat-treated polyethylene terephthalate film (thickness: 125 μm) was placed in a vacuum container as a transparent substrate by using indium oxide.
Tin oxide sintered body (composition ratio In ₂ O ₃ : SnO ₂ = 8)
0: 20% by weight)
After evacuating the vacuum container to a pressure of 2.6 mPa or less with an oil rotary pump and a turbo molecular pump, an argon / oxygen mixed gas (total pressure 266 mPa: oxygen partial pressure 5.3 mPa) was introduced as a sputter gas, and a target-electrode gap was introduced. Then, a DC bias was applied to generate a plasma, and an ITO film having a thickness of 0.11 μm was formed on the transparent substrate by sputtering to obtain a transparent conductive laminate.

According to the examples and comparative examples, a transparent conductive film was formed on a transparent substrate, and its surface resistance value R ₀ (Ω / □) was measured and subjected to a heat treatment.
R ₁ (Ω / □) was measured and evaluated by the rate of change in the surface resistance of the ITO film due to the heat treatment: R ₁ / R ₀ . As R ₁ / R ₀ is closer to 1.0, it can be said that a stable transparent conductive film in which the surface resistance of the ITO film does not change by the heat treatment. The heat treatment was performed at 120 ° C. for 6 hours in the air. In addition, the amount of carbon contained in the ITO films was measured while performing ion etching by the SIMS method, and the distribution of the carbon content in the depth direction was measured.

FIG. 3 shows an example of an IT manufactured according to the embodiment and the comparative example.
4 shows the depth distribution of the carbon content before and after the heat treatment of the O film. Table 1 shows the values, surface resistance values, and surface resistance change rates.

[0048]

[Table 1]

As shown in Table 1, the carbon content was low.
Heat treatment does not reduce the carbon content, ie, N
It can be said that an ITO film having ₁ / N ₀ of 1.0 or more (Example) is a stable ITO film having a small change in surface resistance due to heat treatment. On the other hand, an ITO film (comparative example) having a large carbon content and a reduced carbon content when subjected to heat treatment, that is, an N ₁ / N ₀ smaller than 1.0 has a surface resistance value of 1.4 times by heat treatment. It is had.

Example 2, Comparative Example 2 Using the transparent conductive film prepared as described above as a transparent electrode, a dispersion type EL device was prepared by the following method. <Materials> Light emitting layer Per 100 cc of methyl ethyl ketone, 20 g of a fluoroelastomer (trade name: Daiel, manufactured by Daikin Industries, Ltd.) was dissolved and used as a binder resin. For 1 g of this binder resin, a phosphor powder (zinc sulfide powder manufactured by OSRAM Sylvania Co., manufactured by Capsule type # 3)
2) was dispersed in an amount of 2 g to obtain a light emitting layer material. -Dielectric layer The binder resin used for the light emitting layer was used. -Backside electrode Aluminum having a purity of 99.9% was used.

<Manufacturing method> A light-emitting layer material was coated on the ITO film by a bar coater, and this was heated and dried at 120 ° C. for 2 hours in the air. Let dry. At that time ITO
The portion for taking out the membrane electrode was left. The thickness is 3 each
The bar coater was adjusted to be 0 μm and 40 μm. Next, a back electrode material was formed by a resistance heating type vacuum evaporation method. The thickness was 0.3 μm.

A sine wave of 100 Vrms and 400 Hz was applied between the transparent electrode (ITO film) and the back electrode (aluminum vapor-deposited film) of the dispersion-type EL element produced as described above to emit light. The light emission was at a temperature of 40 ° C. and a relative humidity of 90 °.
% In a constant temperature bath. The light was allowed to stand while emitting light, and the emission time up to the point where a non-light emitting portion having a diameter of 1 mm or more was generated was defined as the lifetime. Table 2 shows the results.

[0053]

[Table 2]

[0054]

As described above, it is possible to provide a transparent conductive film having excellent stability with almost no change in surface resistance even when subjected to a heat treatment. Can be extended. In addition, the reliability of electric products that require a process of heating a transparent conductive film such as a touch panel, a liquid crystal display, or an EC display can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a transparent conductive laminate in which a transparent conductive film is formed on a transparent substrate surface.

FIG. 2 is a cross-sectional view illustrating the concept of a surface and an interface of a transparent conductive film according to the present invention.

FIG. 3 is a graph showing a change in carbon content depending on a depth from an ITO film surface.

[Explanation of symbols]

 Reference Signs List 10 transparent substrate 20 transparent conductive film 21 surface region 25 ITO film region 29 interface region

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Suzuki 2-1-1 Tango-dori, Minami-ku, Nagoya-shi, Aichi Mitsui Toatsu Chemicals Co., Ltd.

Claims (4)

[Claims] 1. A transparent conductive laminate having a transparent conductive film made of at least mainly indium, tin and oxygen formed on one main surface of a transparent substrate, wherein the carbon content of the transparent conductive film is N. ₀ (atoms / cm ³ ), the carbon content after heat treatment in air at 120 ° C. for 6 hours or more
₁ (atoms / cm ³ ), N ₁ / N ₀ is 1.
A transparent conductive laminate having a value of 0 or more. 2. The transparent conductive laminate according to claim 1, wherein the carbon content (N ₀ ) in the transparent conductive film is 8 × 10 ²⁰ (atoms / cm ³ ) or less. 3. The transparent conductive laminate according to claim 1, wherein the transparent substrate is a transparent polymer molded product. 4. The transparent conductive laminate according to claim 1, which is used for a transparent electrode of a dispersion-type EL element.