JP2837171B2 - Transparent conductive film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transparent conductive film for an electroluminescent device (electroluminescence (EL) device). More specifically, in an injection-type EL device that operates by injecting electrons from one electrode and holes from the other electrode, it has sufficient light emission luminance with an organic compound thin film layer provided as a layer that expresses a light emitting function. The present invention relates to a transparent conductive film suitably used for an EL element having flexibility provided by using a polymer film as a substrate.

[Background of the Invention]

EL elements are generally classified into injection-type EL elements and intrinsic EL elements. Among them, the operation mechanism of the injection type EL element applies a forward bias to a pn junction such as a diode, injects electrons and holes from electrodes on both sides, respectively, and generates light by recombination. Generally, this EL element has a structure in which a layer exhibiting the above-mentioned light emitting function is arranged between two electrodes, and a voltage is applied between these electrodes to directly convert electric energy into light. It is. The characteristics of injection-type EL devices are that they operate in a wide drive frequency range from DC to AC, can be driven at low voltage, and have good conversion efficiency from electricity to light. Unlike elements, for example, incandescent lamps, fluorescent lamps, etc., thin-film panels, belts, various shapes such as cylinders, for example, lines, diagrams, display materials for images, etc., or large-area panels, etc. That is, there is a possibility that a planar light emitting body can be realized. On the other hand, an intrinsic EL element is provided with a luminescent material such as zinc sulfide doped with a transition metal or a rare earth metal by a method such as sandwiching a dielectric layer between two electrodes or dispersing with a high dielectric polymer. A light-emitting element that converts electric energy directly into light by applying a relatively high AC voltage to the electrodes. These intrinsic types
EL elements are widely used as backlights for thin-film panels and liquid crystal displays, but have had problems such as being unable to operate at low voltage.

Recently, an injection type light emitting diode device in which two organic compound thin films having hole conductivity and electron conductivity are stacked has been reported.
(CWTang: Appl.Phys.Lett.51. (12) .193, (1987))
Light-emitting elements using this organic material have attracted attention because of their features such as various thin film formation methods and the ability to form a thin film with a large area with high accuracy.

However, when an element is formed using only an organic material for EL that is currently known, the intensity of light emission is limited to some extent.
Further, there is a problem that the light emission intensity is unstable and the like, and it has not been practically used.

There is a demand for an EL element that can produce a uniform thin film over a large area, is high in mass productivity, and is cost effective. Moreover, when considering practicality, it is important that the element form has flexibility. The present inventors have assiduously studied, and as a result, have solved the above-mentioned problems, have flexibility, can produce a uniform thin film over a large area, have high mass productivity, and are economically advantageous. In developing a new EL device, we have invented a transparent conductive film that is extremely suitable as a substrate material.

[Disclosure of the Invention]

The present invention is a transparent conductive film in which an oxide film containing tin and antimony as a main component of indium in an amount of 2 to 25 at.% With respect to indium is formed on a polymer film as a thin film, and is particularly suitable as an EL element substrate. . A light emitting element formed by providing the transparent conductive film of the present invention as at least one electrode and providing an organic compound thin film layer as a layer exhibiting a light emitting function between two opposing electrodes has flexibility, It is possible to produce a uniform thin film over a large area,
Moreover, it is rich in mass productivity and advantageous in cost.

As a method for forming the transparent conductive film on the polymer film, various physical or chemical thin film forming methods such as a sol-gel method, a spray method, an evaporation method, and a sputtering method are used. Particularly preferably, a thin film formed by DC or RF magnetron sputtering is a thin film having a thickness of several hundreds of mm and has few pinholes.

The transparent electrode layer in the conductive film of the present invention is composed of a composite oxide containing indium as a main component and tin and antimony, and the ratio of tin and antimony to indium is 2 to 25 at.%. Is important,
More preferably, the ratio of antimony to tin is 5 to 5.
The electrode layer is 50 at.%. The thickness of this transparent electrode layer is 3
The surface resistance is from 1 to 300 Ω / □. More preferably, it is 500-2000 °.

The organic compound thin film layer as a light emitting function exhibiting layer when forming an EL element composed of the transparent conductive film of the present invention comprises 1
It consists of a kind of organic compound thin film or a laminated film of two or more kinds of organic compound thin films. As the organic compound, an organic compound having high emission quantum efficiency, a π-electron system which is easily affected by external perturbation, and which is easily excited is preferably used.

Examples of such organic compounds include condensed polycyclic aromatic hydrocarbons, p-terphenyl, 2,5-diphenyloxazole, 1,4-bis- (2-methylstyryl) -benzene, xanthine, coumarin, acridine, Having a diamine dye, benzophenone, phthalocyanine, and a metal complex compound formed from a metal and an organic ligand, and a heterocyclic compound and a derivative thereof other than the above, an aromatic amine, an aromatic polyamine, and a quino structure Among the compounds, a compound that forms a complex in an excited state, polyacetylene, polysilane, or the like, or a mixture of these compounds is used. More specifically, a metal complex compound formed from a ligand of a metal and an organic substance will be described. As the metal forming the complex, Al, Ga, Ir, Zn, Cd, Mg, Pb, Ta, or the like is used. As the ligand of the organic substance, porphyrin, chlorophyll, 8-hydroxyquinoline (oxin (Ox)), phthalocyanine, salicylaldehyde oxime, 1-nitroso-2-naphthol, kuferon, dithizone, acetylacetone and the like are used. More specifically, the oxine complexes include an oxine complex, a 5,7-dibromooxin complex (hereinafter referred to as diBrOx), a 5,7-diiodoxine complex (hereinafter referred to as diIOx), and a thiooxin complex ( The following metal complex compounds are more specifically represented by Al (Ox) ₃ , Zn (hereinafter represented by ThioOx), selenooxin complex (hereinafter represented by SelOx), methyloxin complex (hereinafter represented by MeOx), and the like. Ox) ₂ , Zn
(DiBrOx) ₂ , Zn (diIOx) ₂ , Zn (ThioOx) ₂ , Zn (SelO
x) ₂ , Bi (MeOX) ₂ or the like is used.

As a method for producing the above organic compound thin film, various physical or chemical thin film forming methods such as a vacuum evaporation method are used, and a sublimation method, a coating method, a spin coating method, a pulling method, etc. are also effectively used. Used.

The polymer film in the present invention is not particularly limited as long as it has good transparency, but may require heat resistance depending on electrode forming conditions. One that is easy to use is polyethylene terephthalate (PE
T), polycarbonate (PC), polyethersulfone (PES), polyetheretherketo (PEEK) and the like, but polyethylene (PE) and polypropylene (PP) can also be used. Further, not only homopolymers but also various copolymers can be used.

In addition, when forming an EL element using the conductive film of the present invention, not only the transparent electrode or a general metal oxide electrode but also a metal, an alloy, a thin film of a metal compound such as a metal silicide, etc. Alternatively, one or two or more of these stacked thin films are used. More preferably, it is preferable to use a material having a high efficiency of injecting electrons into the organic light emitting layer in contact. More specifically, as the electrode material, a metal or alloy thin film having a small work function of electrons, a laminated thin film thereof, or the like is used, and even more specifically, Mg, Li, Na, K, Ca, Rb, Sr, metals such as Ce, alloys such as Mg-Ag, Cs-O- Ag, Cs 3 Sb, Na 2 KSb, (C
s) A thin film of a metal compound such as Na ₂ KSb or a laminated thin film thereof is suitable.

The light emitting element may have a multi-layer structure of electrode layer / layer exhibiting light emitting function / electrode layer / layer exhibiting optical function / electrode layer / layer exhibiting light emitting function / electrode. With this element structure, it is also possible to adjust the color tone and make the color multi-colored. Also,
This element may be arranged in large numbers on a plane. The elements arranged on this plane may be used as a color display member by changing the emission color of each element.

[Application example]

As shown in FIG. 1, a transparent conductive film 2 was formed on a 75 μm thick PET film 1 by DC magnetron sputtering using an indium-tin-antimony target to form a first electrode layer. The atomic composition ratio of indium, tin, and antimony in this transparent conductive film was 87/11/2.
Next, a thin film of aluminum oxine (Al (Ox) ₃ ) having a thickness of 400 A was deposited on the electrode layer by vacuum resistance heating evaporation to form an organic compound thin film layer 3. Further, a Mg metal thin film was deposited on this layer by an electron beam evaporation method to form a second electrode layer 4, thereby obtaining a light emitting device using the transparent conductive film obtained in the present invention. The area of the deposited Mg metal film is
3mm square.

A DC voltage was applied to the light emitting device, and current characteristics with respect to the applied voltage were examined. FIG. 2 shows the characteristics. When the transparent electrode was positive and the Mg side was positive, the current increased with an increase in voltage. With the opposite polarity, current did not flow, so-called diode characteristics were exhibited. When a voltage of 12 V was applied in the forward direction of this diode, an injection current of 100 mA was observed. When this current value is converted to current density, 1.1 A
/ cm ² . The device also operated at DC or AC. Also, under normal indoor fluorescent light,
Moreover, green surface emission was clearly observed. In addition, the same light emission was observed when a cylindrical film was formed by utilizing the flexibility of the polymer film and a similar energization test was performed.

〔The invention's effect〕

As is apparent from the above application examples, the present invention provides a transparent conductive film suitable for a high-performance light-emitting element having flexibility that could not be achieved in the prior art, and a display member and the like. Is industrially useful.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an application example to an EL element using the conductive film of the present invention. FIG. 2 is a graph showing characteristics of a light emitting device using the transparent conductive film of the present invention.
In the figure, 1 ... PET, 2 ... An electrode layer made of a transparent conductive film,
Reference numeral 3 indicates an organic compound thin film layer, and reference numeral 4 indicates a second electrode layer.

Claims (2)

(57) [Claims] 1. A transparent conductive film formed on a polymer film, comprising indium as a main component and tin and antimony in an amount of 2 to 2.
A transparent conductive film characterized by being an oxide film containing 25 at.%. 2. The transparent conductive film according to claim 1, which is for an electroluminescent device.