JP4054082B2 - Thin film light emitting device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film light emitting element used for a flat light source, a display device, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
An EL (electroluminescence; electroluminescence) element using an organic substance is composed of a pair of electrode layers, at least one of which is transparent, and a light emitting layer interposed between the pair of electrode layers. The light emitting layer is made of a fluorescent organic material such as anthracene, pyrene, stilbene, or perylene, and recently, a fluorescent organic material that is a metal complex such as tris (8-quinolinolato) aluminum (Alq). An organic EL device in which a formed light emitting layer and an organic material layer formed of an aromatic amine such as triphenyldiamine (TPD) or a derivative thereof are laminated and the laminate is interposed between a pair of electrode layers. Attention has been paid. Furthermore, recently, it has been reported that the light emission characteristics of organic EL elements are improved by interposing a conductive layer made of a metal oxide between the organic light emitting layer and the electrode layer (the 43rd Applied Physics Relationship). (Proceedings of the Joint Lecture Meeting, page 1122, March 27, 1996).
[0003]
According to the above report, an ITO (indium oxide-tin oxide; In ₂ O ₃ -SnO ₂ ) layer, which is a transparent conductive material, is formed on a glass substrate, and vanadium oxide (VOx), ruthenium oxide is formed on the ITO layer. A metal oxide layer of a product (RuOx) and molybdenum oxide (MoOx), a triphenyldiamine (TPD) derivative and a quinolinol aluminum complex (Alq) are laminated on the metal oxide layer, and finally an electrode It is described that an organic EL element was formed by forming magnesium-silver (Mg—Ag (9: 1)) as The metal oxide layer of this organic EL element is formed by RF magnetron sputtering. This organic EL element has been reported to have a reduced emission start voltage and improved luminance characteristics as compared with an element having no metal oxide layer.
[0004]
[Problems to be solved by the invention]
However, even if an attempt is made to form an organic-inorganic hybrid (organic-inorganic composite) in which a metal oxide and an organic material are combined in order to further improve the light emission characteristics, the sputtering method or the vacuum evaporation method is used. Organic-inorganic hybrids are not possible.
[0005]
The present invention has been made in view of the circumstances as described above, and provides a thin-film light-emitting element having further improved light-emitting characteristics and a method for manufacturing such a thin-film light-emitting element. Objective.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a thin-film light-emitting element in which a light-emitting layer made of a fluorescent organic material is interposed between a pair of electrode layers, at least one of which is transparent, and one electrode layer of the pair of electrode layers wherein between the light emitting layer, the organic was formed by the decomposition products and organic polymer metal alkoxy de and - characterized in that was inserted inorganic hybrid conductive layer.
[0007]
The invention according to claim 2, forming an electrode layer made of a transparent conductive material on a glass substrate, the surface of the electrode layer, a solution containing a metal alkoxy de and an organic polymer is applied, it Forming a conductive layer by forming a film, forming a light emitting layer made of a fluorescent organic material on the surface of the conductive layer, and forming an electrode layer made of a conductive material on the light emitting layer. A thin film light emitting device is manufactured by sequentially passing through.
[0008]
Thin-film light emitting device of the invention according to claim 1, the organic conductive layer interposed between the one electrode layer and the light emitting layer were formed by the decomposition products and organic polymer metal alkoxy de - Inorganic Compared to an inorganic conductive layer made of a metal oxide, the conductive layer is a hybrid, and the interface between the conductive layer and the organic light emitting layer is stabilized and the adhesion between the two layers is improved. In addition, the organic-inorganic hybrid conductive layer has improved hole injection efficiency from the electrode layer to the organic light emitting layer due to its porosity, and the thin film light emitting device having this organic-inorganic hybrid conductive layer is a thin film having an inorganic conductive layer. Compared with the light emitting element, the light emission characteristics can be further improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described below with reference to FIG.
[0010]
FIG. 1 is a schematic enlarged longitudinal sectional view showing a structure of a thin film light emitting element, showing an example of an embodiment of the present invention. In this thin film light emitting element, a transparent electrode layer 2 made of a transparent conductive material is formed on a transparent glass substrate 1, and a light-transmitting conductive layer 3 (hole injection layer) is formed on the surface of the transparent electrode layer 2. The organic layer (hole transport layer) 4 formed of an aromatic amine or a derivative thereof and the light emitting layer 5 formed of a fluorescent organic material are laminated on the conductive layer 3, and the back electrode layer is formed on the light emitting layer 5. 6 is formed. As the transparent conductive material for forming the transparent electrode layer 2, for example, ITO, tin oxide-antimony oxide, or the like is used. The conductive layer 3 is formed of an organic-inorganic hybrid having translucency obtained by uniformly blending a metal oxide and an organic polymer. The metal oxide that forms this organic-inorganic hybrid may be any compound that has a light-transmitting property by being thinned. For example, titanium oxide (TiO ₂ ), vanadium oxide (V ₂ O ₅ ), zinc oxide ( ZnO), molybdenum oxide (MoO ₃ ), ruthenium oxide (RuO ₂ ), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), or the like is used. As the organic polymer forming the organic-inorganic hybrid, various types such as acrylic, methacrylic, epoxy, polyurethane, polyether, and polyamide may be used. The material for forming the conductive layer 3 may be crystalline or amorphous as long as the above characteristics are obtained. The thickness of the conductive layer 3 is, for example, 1,000 mm or less, preferably 500 mm or less.
[0011]
For example, TPD or a derivative thereof is used as the aromatic amine or the derivative thereof that forms the organic layer 4. The fluorescent organic material forming the light emitting layer 5 is generally a metal complex such as tris (8-quinolinolato) aluminum (Alq), anthracene, pyrene, stilbene, perylene, quinone, phenanthrene, naphthalene and derivatives thereof. It may be used. As a conductive material for forming the back electrode layer 6, for example, a magnesium-silver (Mg-Ag (9: 1)) alloy or the like is used.
[0012]
Next, a method for manufacturing the above-described thin film light emitting device will be described. First, a transparent electrode layer 2 is formed on a glass substrate 1 by depositing a transparent conductive material such as ITO by sputtering or vacuum deposition. Next, an organic-inorganic hybrid conductive layer 3 is formed on the transparent electrode layer 2 by a sol-gel method. To do this, first, a metal element component, for example, the alkoxy de organic polymer vanadium (V) as a starting material, these are dissolved in a solvent, to prepare a uniform coating solution. Also, as the solvent, a polar solvent such as alcohol or acetonitrile, chloroform, dichloroethane, dichloromethane, hexane, benzene, toluene, from among xylene, may be appropriately selected according to the solubility of the starting material.
[0013]
Next, the coating solution is applied to the surface of the transparent electrode layer 2 on the glass substrate 1 by a coating method such as spin coating or dip coating, and the coating solution is dried at a temperature of about 100 to 200 ° C., for example. A conductive layer 3 is formed on the layer 2. In some cases, the coating solution may be dried under reduced pressure to form a film. Then, the organic material layer 4 and the light emitting layer 5 are laminated on the conductive layer 3 by a vacuum deposition method. First, a solution in which an aromatic amine such as TPD or a derivative thereof is dissolved in an appropriate solvent such as toluene is prepared, and the organic layer 4 is formed on the surface of the conductive layer 3 by a dip coating method or a spin coating method. Next, a solution in which a fluorescent organic material such as Alq is dissolved in an appropriate solvent, for example, a water-alcohol solvent, is prepared, and the photosensitive layer 5 is formed on the surface of the organic layer 4 by a dip coating method or a spin coating method. You may do it. Finally, a conductive material such as Mg—Ag alloy is attached to the surface of the photosensitive layer 5 by vapor deposition or the like, and the back electrode layer 6 is formed on the photosensitive layer 5.
[0014]
【Example】
[Example 1]
Ethanol solution of triethoxyvanadyl (VO (OC ₂ H ₅ ) ₃ ) (V ₂ O ₅ conversion: 40 wt%) and PMMA (polymethyl methacrylate) are 0.4 wt% (V ₂ O ₅ conversion) with chloroform. ) And 0.1 wt% concentration to prepare a coating solution. This coating solution was spin coated (2,350 rpm, 3 seconds) in the air on the surface of the ITO film formed on the glass substrate. Next, the solution applied on the ITO film was dried at a temperature of 100 ° C. for 30 minutes, whereby a 200 mm thick VOx-PMMA hybrid layer was formed on the surface of the ITO film. Subsequently, a 400 mm thick TPD layer is laminated on the VOx-PMMA hybrid layer, and a 600 mm thick Alq layer is further laminated thereon, and an Mg-Ag electrode layer is formed on the surface of the Alq layer. A thin film light emitting device having the device structure of FIG. 1 having a VOx-PMMA hybrid layer as a (hole injection layer) was produced.
[0015]
[Comparative Example 1]
A solution of triethoxyvanadyl (VO (OC ₂ H ₅ ) ₃ ) in ethanol (V ₂ O ₅ equivalent: 40% by weight) is diluted with chloroform to a concentration of 0.4% by weight (V ₂ O ₅ equivalent). A solution was prepared. This coating solution was spin-coated (2,350 rpm, 3 seconds) in the air on the surface of the ITO film formed on the glass substrate. Next, the solution applied on the ITO film was dried at a temperature of 100 ° C. for 30 minutes, whereby a VOx layer having a thickness of 200 mm was formed on the surface of the ITO film. Subsequently, a TPD layer having a thickness of 400 mm on the VOx layer and an Alq layer having a thickness of 600 mm on the VOx layer were laminated by a vacuum deposition method, and an Mg-Ag electrode layer was formed on the surface of the Alq layer. A thin film light emitting device having the device structure as shown in FIG.
[Comparative Example 2]
As Comparative Example 2, a thin film light-emitting element having an element structure of ITO / TPD (400Å) / Alq (600Å) / Mg-Ag without a conductive layer (hole injection layer) was produced.
[0016]
FIG. 2 shows the light emission characteristics (voltage-luminance characteristics) of the respective thin film light emitting devices of Comparative Example 1 and Comparative Example 2. In FIG. 2, ◯: ITO / V ₂ O ₅ (200Å) / TPD (400Å) / Alq (600 −) / Mg-Ag (Comparative Example 1), ●: ITO / TPD (400Å) / Alq (600Å) / Mg -Ag (Comparative Example 2). As can be seen from the results shown in FIG. 2, the thin film light emitting device of Comparative Example 1 starts to emit light at a lower applied voltage than the thin film light emitting device of Comparative Example 2, and the luminance is particularly high in the low voltage portion.
[0017]
FIG. 3 shows the light emission characteristics of the respective thin film light emitting devices of Example 1 and Comparative Example 2. In FIG. 3, ○: ITO / V ₂ O ₅ -PMMA (200Å) / TPD (400Å) / Alq (600Å) / Mg-Ag (Example 1), ●: ITO / TPD (400Å) / Alq (600Å) / Mg-Ag (Comparative Example 2). As can be seen from the results shown in FIG. 3, the thin-film light-emitting device of Example 1 has a further lower emission start voltage than the thin-film light-emitting device of Comparative Example 1, and the luminance is particularly high at the low voltage portion.
[0018]
【The invention's effect】
In the thin film light emitting device of the invention according to claim 1, the interface between the conductive layer and the organic light emitting layer interposed between the electrode layer and the organic light emitting layer is stabilized, and the adhesion between the two layers is improved. Since the hole injection efficiency from the electrode layer to the organic light emitting layer is improved by making the conductive layer porous, the light emitting characteristics are further improved as compared with a thin film light emitting device having an inorganic conductive layer between the electrode layer and the organic light emitting layer. improves.
[0019]
According to the manufacturing method of the invention according to claim 2, the thin-film light emitting device of the invention according to claim 1, which cannot be manufactured by a sputtering method or a vacuum evaporation method, can be manufactured, and the emission characteristics are further improved. Thus, a thin-film light emitting device can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing a structure of a thin-film light emitting device, showing an example of an embodiment of the present invention.
FIG. 2 is a graph showing light emission characteristics (voltage-luminance characteristics) of a thin film light emitting element of a comparative example.
FIG. 3 is a diagram showing light emission characteristics (voltage-luminance characteristics) of a thin film light emitting element according to an example of the present invention and a thin film light emitting element of a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent electrode layer 3 Conductive layer 4 Organic substance layer 5 Light emitting layer 6 Back electrode layer

Claims (2)

In a thin film light emitting device in which a light emitting layer made of a fluorescent organic material is interposed between a pair of electrode layers, at least one of which is transparent,
Between the light emitting layer and one electrode layer of the pair of electrode layers, the organic was formed by the decomposition products and organic polymer metal alkoxy de - that was inserted inorganic hybrid conductive layer A thin-film light emitting device characterized. Forming an electrode layer made of a transparent conductive material on a glass substrate;
On the surface of the electrode layer, a step of a solution containing a metal alkoxy de and an organic polymer coating is then deposited of it form a conductive layer,
Forming a light emitting layer made of a fluorescent organic material on the surface of the conductive layer;
And a step of forming an electrode layer made of a conductive material on the light emitting layer.

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