JP3476277B2 - Transparent conductive laminate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive laminate, and more particularly, to a transparent conductive material excellent in environmental resistance which can be suitably used as a transparent electrode of an electroluminescence display. The present invention relates to a functional laminate. 2. Description of the Related Art Conventionally, transparent conductive laminates have conventionally been used for electrodes of display elements such as liquid crystal displays, electroluminescence displays and electroluminescence displays, window electrodes of photoelectric conversion elements such as solar cells, and electromagnetic wave shields of electromagnetic wave shields. It is used as an electrode of an input device such as a film or a transparent touch panel. As a conventionally known transparent conductive layer, gold, silver, platinum, a noble metal thin film such as palladium,
Oxide semiconductor thin films such as indium oxide, stannic oxide, and zinc oxide are known. The former noble metal thin film having a low resistance value can be easily obtained, but is inferior in transparency. The latter oxide semiconductor thin film has a slightly lower resistance value than the noble metal thin film,
It is widely used because of its excellent transparency. Among them, an indium oxide thin film containing tin oxide is widely used because of its low resistance and excellent transparency. The resistivity of a tin-doped indium oxide thin film is usually 5 × 10 ⁻⁵ to
About 1 × 10 ⁻³ Ω · cm, transmittance is generally 80 to 90%
It is. An electroluminescent display is based on a transparent conductive substrate having a transparent conductive film formed on a transparent substrate, and a luminescent layer, an insulating layer, and a back electrode are sequentially formed on the transparent conductive film, and the whole is transparent and moisture-proof. Structures coated with layers are known. The transparent conductive film is made of tin oxide, indium oxide, etc., the luminescent layer is made of zinc sulfide, cadmium sulfide, zinc selenide, etc., and the insulating layer is made of yttrium oxide, silicon nitride, thallium oxide, etc. having a high dielectric constant. Aluminum is used for the electrodes. Conventionally, a glass-based substrate has been used as a transparent conductive substrate for an electroluminescent display. The transparent conductive substrate has excellent transparency in order to efficiently emit visible light emitted from the light-emitting layer to the outside. It is required to withstand use, but when glass is used as the substrate, the substrate temperature is set to 400 ° C.
This is because, since it can be heated to about ° C, a chemically stable crystalline transparent conductive layer can be formed, and a transparent conductive substrate excellent in transparency and environmental resistance can be easily obtained. However, when glass is used as the substrate, the glass is fragile, heavy,
There is a problem that there is a limit to thinning. Therefore, there is a strong demand for a transparent electrode using a transparent polymer substrate that is difficult to crack and that is thin and light. [0005] When a transparent polymer substrate is used for a transparent electrode for an electroluminescent display, the heating temperature of the substrate when forming a transparent conductive layer is as follows.
Since the temperature is limited by the heat-resistant temperature of the polymer substrate, the temperature must usually be 200 ° C. or lower. Therefore, it is not easy to form crystalline indium oxide having excellent environmental resistance. For use as a transparent conductive substrate for an electroluminescent display, at least visible light transmittance of 80%
As described above, a sheet resistance of 1000Ω / □ or less is required. If a transparent conductive layer mainly composed of indium oxide is formed on one main surface of the transparent polymer film to have a thickness of 10 nm or more, a transparent conductive film having a visible light transmittance of 80% or more and a sheet resistance of 1000 Ω / □ or less can be produced. If this is used as it is as a transparent electrode for an electroluminescent display, the luminescent layer such as zinc sulfide or cadmium sulfide directly contacts the transparent conductive layer mainly composed of indium oxide. Then, there is a problem that the interface between the light emitting layer and the transparent conductive layer is deteriorated, and the light emission luminance is attenuated relatively early. As a method of suppressing the deterioration of the interface between the light emitting layer and the transparent conductive film, palladium is laminated on the transparent conductive layer mainly composed of indium oxide, which deteriorates, so that the transparent conductive layer does not directly contact the light emitting layer. (Japanese Patent Application Laid-Open No. Sho 62-18254). However, lamination of palladium greatly increases the price because the metal is an expensive material, and there has been a strong demand from the industry for a transparent conductive substrate for an electroluminescent display which is inexpensive and has excellent environmental resistance. Also, other metals including palladium, for example,
There has also been proposed a transparent conductive substrate in which indium, tin, aluminum, chromium, and the like are stacked on a transparent conductive layer mainly composed of indium oxide by a vapor deposition method, as specifically shown in Examples (Japanese Patent Laid-Open No. Hei 6 (1994)). -71804). However, we have found that although these are effective in suppressing the unevenness of light emission in the early stage of electroluminescence display, they are not necessarily effective in suppressing the deterioration with time of light emission luminance. [0007] In view of the above circumstances, the present invention suppresses light emission unevenness, suppresses deterioration of the interface between the light emitting layer and the transparent conductive layer, suppresses deterioration when light emission is continued, and reduces the length of the electroluminescent display. Life can be measured,
The sheet resistance is 100 when the visible light transmittance is 80% or more.
It is intended to provide a transparent conductive laminate of 0Ω / □ or less at low cost. Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that the copper formed by the sputtering method lowers the luminance of the electroluminescent display when the light emission is continued. Is found to have an effect of remarkably suppressing, and at least on one main surface of the transparent polymer substrate, a transparent conductive layer mainly composed of indium oxide having a thickness of 10 to 200 nm is formed, and further thereon, By forming a metal thin film layer made of copper with a thickness of 1 to 20 nm by a sputtering method, it has been found that environmental resistance is significantly improved as compared with laminating a metal thin film layer other than copper, and the present invention is completed. I have reached. That is, according to the present invention, at least one main surface of the transparent polymer substrate (A) has a thickness of at least one.
Transparent conductive layer made of indium oxide 0~200nm (B), and the metal thin film layer of copper formed by sputtering (C), and was formed by ABC becomes configure, suppressed deterioration with time of the emission luminance, electroluminescence luminescence
The present invention relates to a transparent conductive laminate for a display . The present invention will be described with reference to FIG. 1 of the accompanying drawings. As shown in FIG.
First transparent conductive layer mainly composed of indium oxide
A layer (B) (20), a second layer (C) (30) which is a metal thin film layer made of copper formed by a sputtering method,
Are sequentially formed on the transparent conductive laminate. Preferably, the thickness of the transparent conductive film (B) mainly composed of indium oxide is 10 to 200 nm, and the thickness of the metal thin film layer (C) composed of copper formed by a sputtering method is 1 to 200 nm.
The present invention relates to a transparent conductive laminate having a thickness of 20 nm. As the polymer substrate used in the present invention, a plastic molded article having transparency can be used.
Specific examples include polyethylene terephthalate, polyethersulfone, polyetheretherketone, polycarbonate, polypropylene, and polyimide. These polymer substrates may be plate-shaped or film-shaped as long as the main surface on which the transparent conductive layer is formed is smooth.
A plate-shaped polymer substrate is excellent in dimensional stability and mechanical strength, and can be suitably used particularly when such a substrate is required. In addition, since the polymer film is flexible and the transparent conductive layer can be formed continuously by a roll-to-roll method, when this is used, a transparent conductive substrate can be efficiently produced, so that Can also be suitably used. In this case, a film having a thickness of usually 10 to 250 μm is used. When the thickness of the film is 10 μm or less, the mechanical strength as a base material is insufficient, and when the thickness is 250 μm or more, the flexibility is insufficient, so that the film is not suitable for being wound on a roll. [0012] Among the transparent polymer substrates, polyethylene terephthalate is more preferably used because of its excellent transparency and processability. In addition, since polyether sulfone has excellent heat resistance, a heat treatment is required when heat treatment is required after the production of the transparent conductive laminate, and when assembling an electroluminescent display using the transparent conductive laminate. When necessary, it can be used more preferably. This transparent polymer substrate has its surface subjected to sputtering, corona treatment, flame treatment, ultraviolet irradiation,
Etching treatment such as electron beam irradiation, or undercoating treatment may be performed to improve the adhesion of the transparent conductive layer mainly formed of indium oxide to the above-mentioned film to the film. Before forming the transparent conductive layer mainly composed of indium oxide, dust-proofing treatment such as solvent cleaning or ultrasonic cleaning may be performed as necessary. In the present invention, a transparent conductive layer mainly composed of indium oxide is formed as a first layer on one main surface of the transparent polymer substrate. The transparent conductive layer may be mixed with tin to lower the resistivity. Usually, by containing about 3 to 20% by weight of tin, the resistivity can be reduced, and a transparent conductive layer having a required sheet resistance value with a smaller film thickness can be formed. The thickness of the transparent conductive layer mainly composed of indium oxide is usually preferably from 10 nm to 200 nm. The thickness of the transparent conductive layer affects its sheet resistance and visible light transmittance. In order to reduce the sheet resistance value, the thickness of the transparent conductive layer may be increased as much as possible, but if it is increased, the visible light transmittance is reduced. Therefore, the thickness of the transparent conductive layer is determined by the required sheet resistance and visible light transmittance. If the thickness of the transparent conductive layer is 10 nm or less, the sheet resistance becomes higher than 1000 Ω / □, which is not suitable for use as a transparent electrode of an electroluminescent display. In order to lower the sheet resistance value, it is sufficient to increase the film thickness.
If the thickness is more than 200 nm, the visible light transmittance is lowered, which is not preferable. That is, by forming a transparent conductive layer mainly composed of indium oxide having a thickness of 10 to 200 nm on one main surface of a transparent polymer substrate, a sheet resistance required for a transparent electrode of an electroluminescent display is obtained. And a transparent conductive laminate having visible light transmittance is obtained, but the transparent conductive layer is inferior in environmental resistance, and is used as it is for a transparent electrode to form an electroluminescent display, When the light emission is continued by applying the voltage, the light emission intensity is attenuated relatively early. Therefore, in the present invention, after forming the transparent conductive layer mainly composed of indium oxide as described above, a metal thin film layer composed of copper is further formed thereon by sputtering. This layer is provided in order to prevent the deterioration of the transparent conductive layer mainly composed of indium oxide due to direct contact between indium oxide and the light emitting layer such as zinc sulfide or cadmium sulfide. That is, by providing a metal thin film layer mainly made of copper on the indium oxide layer, it is possible to prevent the transparent conductive layer mainly made of indium oxide and the light emitting layer such as zinc sulfide or cadmium sulfide from coming into direct contact with each other. Since the laminated copper has excellent durability with respect to a light emitting layer such as zinc sulfide or cadmium sulfide, it is possible to remarkably suppress deterioration such as a decrease in light emission luminance caused when light emission is continued. It should be noted here that the method of forming the metal thin film layer made of copper must be based on the sputtering method. As a means for forming a metal thin film, a vapor deposition method is known as a simple method other than the sputtering method. However, although the electroluminescence device manufactured using the metal thin film layer made of copper formed by the vapor deposition method can suppress the initial light emission unevenness, it does not show a remarkable effect with respect to the deterioration over time (durability) of the light emission luminance. . That is, it is necessary to form a metal thin film layer made of copper by a sputtering method in order to suppress the deterioration of the electroluminescence element over time when light emission is continued. The thickness of the metal thin film layer made of copper formed by the sputtering method is preferably 1 to 20 nm. More preferably, it is 1 to 10 nm. If the thickness is less than 1 nm, the effect of improving environmental resistance cannot be obtained, which is not preferable. That is, in order to impart environmental resistance as a transparent electrode of an electroluminescence display, a metal thin film layer made of copper having a thickness of at least 1 nm is required. If the thickness is more than 20 nm, the transparency is impaired. In addition, the improvement of the environmental resistance by laminating the layers is sufficient at a thickness of 20 nm or less. It is not preferable to form a layer. Economically, the thickness of the layer is preferably as thin as possible within a range that does not impair the environmental resistance. Since the environmental resistance is sufficiently obtained with a thickness of 10 nm, the thickness of the metal thin film layer is 1 to 1
0 nm is more preferred. It is known that a metal left in the atmosphere has a natural oxide layer of several nm formed on its surface. Therefore, it is considered that a natural oxide layer is also formed on the metal thin film layer (C) made of copper formed by the sputtering method in the present invention. In this case, it is expected that a few nm of the outermost surface of the metal thin film layer is copper oxide. As a method for forming a transparent conductive layer mainly composed of indium oxide, a vacuum evaporation method, a sputtering method,
Any of conventionally known physical vapor deposition methods such as an ion plating method can be adopted. In the sputtering method, indium oxide containing indium oxide or tin is used as a target, and direct current (DC) or radio frequency (RF) is used using an inert gas such as argon as a sputtering gas.
A magnetron sputtering method can be used. Further, in order to increase the transparency and conductivity of the transparent conductive layer, 0.1 to 20 flow% of oxygen gas may be mixed in the sputtering gas.
In addition, indium or a tin-indium alloy is used as a target, an inert gas such as argon is used as a sputtering gas,
Direct current or high frequency reactive sputtering using oxygen gas as the reactive gas can also be suitably used. In this method, the transmittance and the conductivity of the transparent conductive layer very sensitively affect the partial pressure of oxygen gas, which is a reactive gas, and therefore it is preferable to strictly control the partial pressure. In any of the above sputtering methods, a transparent conductive layer having excellent transparency and conductivity can be easily obtained, and thus can be preferably used. On the other hand, as described above, the sputtering method must be used for forming the metal thin film layer made of copper. In the sputtering method, copper is used as a target,
Direct current or high frequency sputtering using an inert gas such as argon as a sputtering gas can be used. The sputtering pressure varies depending on the apparatus, but is not particularly limited as long as it can be discharged, and is usually about 1 to 10 mTorr. The substrate temperature may be within a range where the polymer substrate is not deformed by heat, and is usually room temperature to 150 ° C. The transparent conductive film obtained by the above method may be subjected to heat treatment (annealing) in order to improve environmental resistance. Heat treatment temperature is usually 100 ~
It is about 200 ° C. The atomic composition of the transparent conductive layer formed by the above method is determined by Auger electron spectroscopy (AES), inductively coupled plasma (ICP), Rutherford backscattering (RB).
S) and the like. These film thicknesses can be measured by Auger electron spectroscopy observation in the depth direction, cross-sectional observation by a transmission electron microscope, or the like. As described above, in the present invention, at least one transparent conductive layer mainly composed of indium oxide is formed as a first layer on one principal surface of a polymer transparent film, and a copper conductive layer is formed as a second layer thereon. By forming a metal thin film layer made of, a transparent conductive substrate having excellent environmental resistance and suitable for a transparent electrode of an electroluminescence display can be provided. In the present invention, for example, on the metal thin film layer of the transparent conductive laminate thus formed, for example,
A solution in which zinc sulfide powder or the like is dispersed in an appropriate solution such as acetone is applied, and a heat treatment is performed by a conventional method to form a light-emitting layer, on which a barium titanate powder is dispersed in an acetone solution. Is applied, and a heat treatment is performed in the same manner as in the conventional method to form a dielectric layer (insulating layer). Further, aluminum or the like is overlaid thereon as a back electrode, heat-treated, and sandwiched between two moisture-proof films. A luminous body can be obtained. Next, the present invention will be described in detail with reference to examples. Example 1 On one surface of a polyethylene terephthalate film (188 μm thick), as a first layer, indium oxide containing 5% by weight of tin oxide was used as a target, argon gas as a sputtering gas, and oxygen gas as a reactive gas. Using a (flow ratio, argon: oxygen = 10: 0.1), a transparent conductive layer having a thickness of 50 nm was formed by a DC magnetron reactive sputtering method under an atmosphere of 3 mTorr. Further thereon, a metal thin film layer having a thickness of 5 nm is formed as a second layer by DC magnetron sputtering under an atmosphere of 3 mTorr using copper as a target and argon gas as a sputtering gas.
A two-layer transparent conductive laminate was produced. [Examples 2 to 4] Example 1 was the same as Example 1 except that the thickness of the second metal thin film layer was 1 nm (Example 2), 10 nm (Example 3), and 20 nm (Example 4). A transparent conductive laminate having a two-layer structure was produced in the same manner as described above. [Examples 5 and 6] A two-layer structure was formed in the same manner as in Example 1 except that the thickness of the first transparent conductive layer was changed to 10 nm (Example 5) and 200 nm (Example 6). Was produced. Comparative Example 1 A one-layer transparent conductive laminate was produced in the same manner as in Example 1 except that the second metal thin film layer was not formed. Comparative Example 2 A transparent conductive film having a two-layer structure was formed in the same manner as in Example 1, except that a metal thin film layer made of palladium was formed using palladium as a target when forming the second layer. A laminate was produced. Comparative Example 3 A two-layer transparent conductive film was formed in the same manner as in Example 1 except that a titanium thin film was formed using titanium as a target when forming the second layer. A laminate was produced. Comparative Example 4 A two-layered transparent conductive film was formed in the same manner as in Example 1 except that indium was used as a target and a metal thin film layer made of indium was formed when forming the second layer. A laminate was produced. Comparative Example 5 A two-layer transparent conductive film was formed in the same manner as in Example 1 except that a tin thin film was formed using tin as a target when forming the second layer. A laminate was produced. Comparative Example 6 A two-layer transparent conductive film was formed in the same manner as in Example 1 except that a metal thin film layer made of chromium was formed using chromium as a target when forming the second layer. A laminate was produced. COMPARATIVE EXAMPLE 7 A two-layer transparent conductive film was formed in the same manner as in Example 1, except that aluminum was used as a target to form a metal thin film layer when forming the second layer. A laminate was produced. Comparative Example 8 A two-layer transparent conductive film was formed in the same manner as in Example 1 except that a silver thin metal layer was formed using silver as a target when forming the second layer. A laminate was produced. Comparative Example 9 On one surface of a polyethylene terephthalate film (188 μm thickness), as a first layer, indium oxide containing 5% by weight of tin oxide as a target was used, argon gas as a sputtering gas, and reactive gas. Oxygen gas (flow ratio, argon: oxygen = 10: 0.
Using 1), a transparent conductive layer having a thickness of 50 nm was formed by a DC magnetron reactive sputtering method under an atmosphere of 3 mTorr. Further, as a second layer, a metal thin film layer having a thickness of 5 nm is formed as a second layer by electron beam evaporation under an atmosphere of 5 × 10 ⁻⁵ Torr using copper as an evaporation source. A conductive laminate was produced. Comparative Example 10 A two-layer transparent conductive laminate was produced in the same manner as in Example 1 except that the thickness of the second metal thin film layer was changed to 50 nm. [Comparative Examples 11 to 12] A two-layer structure was formed in the same manner as in Example 1 except that the thickness of the first transparent conductive layer was changed to 5 nm (Comparative Example 11) and 400 nm (Comparative Example 12). Was produced. The thickness of the transparent conductive layer and the metal thin film layer, the sheet resistance, the visible light transmittance, and the environmental resistance of the transparent conductive film prepared as described above were evaluated by the following methods. Thickness of transparent conductive layer [T ₁ (nm)] and thickness of metal thin film layer [T ₂ (nm)]: film formation rate r (nm / m
in) was measured, and the film thickness was changed by controlling the film forming time t (min). The film thickness T (nm) is obtained from the following equation. T = r × t Sheet resistance [R (Ω / □)]: Measured by a four-terminal method. Visible light transmittance [Tvis (%)]: Hitachi, Ltd.
And a spectrophotometer U-3400. Environmental resistance [I / I ₀ ]: An electroluminescent luminous body is prepared by the following steps, and a voltage of 100 V AC (frequency: 1 kHz) is applied under an atmosphere of a temperature of 50 ° C. and a humidity of 60% to emit light. Light emission luminance I ₀ (candela / m ² ) and light emission luminance I (candela / m ² ) after the light emission was continued for 3000 hours as it is, by Minolta Co., Ltd.
Was measured using a luminance meter: LS-110, and the rate of change I / I ₀ was evaluated. The production of the electroluminescent luminescent material was carried out according to Examples 1 to
A solution obtained by dispersing zinc sulfide powder in an acetone solution was applied onto the transparent conductive substrates obtained in Example 6 and Comparative Examples 1 to 12 , and then applied at 60 ° C. for 120 hours and further for 1 hour.
A heat treatment is performed at 20 ° C. for 2 minutes to form a light emitting layer. Thereafter, a liquid obtained by dispersing barium titanate powder in an acetone solution is further applied thereon,
A heat treatment is performed at 120 ° C. for 120 minutes to form a dielectric layer. Furthermore, aluminum having a thickness of 0.2 mm was stacked thereon and heat-treated at 150 ° C. for 2 minutes. This was sandwiched between two moisture-proof films to obtain an electroluminescent luminescent material. Table 1 shows the above results. [Table 1] As is evident from the results in the above table, the transparent conductive laminate of the present invention has a low sheet resistance and a high visible light transmittance. Further, when an electroluminescent display is formed using the same, the emission luminance decreases. It can be seen that the material also has environmental resistance, in which the resistance is significantly reduced. As described above, in the present invention, a transparent conductive layer mainly composed of indium oxide is formed as a first layer on one main surface of a polymer transparent substrate, and a second conductive layer is formed thereon.
By forming a metal thin film layer made of copper formed by a sputtering method as a layer, a transparent conductive laminate excellent in environmental resistance and suitable for an electroluminescent transparent electrode can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an example of the transparent conductive laminate of the present invention. DESCRIPTION OF REFERENCE NUMERALS 10 Transparent polymer substrate 20 Transparent conductive layer 30 mainly composed of indium oxide formed by sputtering. Metal thin film layer made of copper

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 G09F 9/30-9/46 G09F 13/00-13/46 H01B 5/00-5 / 16

Claims (1)

(57) Claims 1. A transparent substrate (A) having at least one main surface having a thickness of at least 10 to 2 mainly composed of indium oxide.
A transparent conductive layer (B) having a thickness of 00 nm and a metal thin film layer (C) made of copper having a thickness of 1 to 20 nm formed by a sputtering method were formed in an ABC configuration. Electroluminescence display
A transparent conductive laminate for lay .