JP2001338757A - Method of manufacturing electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the utilization efficiency of a material for forming an organic EL layer and for forming a uniform organic film over a wide area, in an electroluminescent element having the organic EL layer. SOLUTION: An anode electrode 2, a hole transport layer 3, a light-emitting layer 4, and a cathode electrode 5 are formed on a transparent substrate 1. The hole transport layer 3 and the light-emitting layer 4 are formed through electrodepostion method. The utilization efficiency of the materials for forming the hole transport layer 3 and the light-emitting layer 4 can be enhanced, as compared with the case of formation by over vapor deposition method, and the uniform organic film can be formed over a wide area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing an electroluminescent device having an organic EL (electroluminescence) layer.

[0002]

2. Description of the Related Art An electroluminescent device having an organic EL layer has attracted attention as a device which emits light by itself, has a wide viewing angle, is a solid device, has excellent impact resistance, and realizes a DC low voltage driving device. ing. However, such organic E
An electroluminescent device having an L layer has a practical use such as lack of long-term storage reliability (lifetime) as compared with an inorganic thin film device (organic dispersion type inorganic EL device), for example, a ZnS: Mn based inorganic thin film device. It had problems to prevent.

However, in recent years, the development of a two-layer structure (a hole transport layer and a light emitting layer) and doping of the light emitting layer with a laser dye have improved the light emitting efficiency and have a half-life of 10,000 hours when the element is driven. Have been reported. In this case, the electroluminescent device has a structure in which a first electrode, a hole transport layer, a light emitting layer, and a second electrode are formed in this order on a transparent substrate.

[0004]

However, in the case of manufacturing such a conventional electroluminescent device, the material of the hole transport layer and the light emitting layer is formed in a crucible or the like by a vapor deposition method of heating and vapor deposition. Therefore, the use efficiency of the materials for forming the hole transport layer and the light emitting layer is low, and the cost is increased. In addition, it is difficult to form a uniform organic film over a large area by the vapor deposition method, and there is a limit to increasing the size of the electroluminescent element. An object of the present invention is to improve the efficiency of using a material for forming an organic EL layer and to form a uniform organic film over a large area.

[0005]

According to the present invention, there is provided a method of manufacturing an electroluminescent device in which a first electrode, an organic EL layer, and a second electrode are formed in this order on a transparent substrate.
The layer is formed by an electrodeposition method. According to the present invention, the organic EL layer is formed by the electrodeposition method, so that the organic EL layer is
The utilization efficiency of a material for forming a layer can be improved, and a uniform organic film can be formed over a large area.

[0006]

Next, a method of manufacturing an electroluminescent device according to an embodiment of the present invention will be described with reference to FIG. First, the transparent substrate 1 is prepared. Transparent substrate 1
Is made of resin such as polyester, polyacrylate, polycarbonate, polysulfone, polyetherketone, glass, or the like.

Next, an anode electrode 2 is formed on the upper surface of the transparent substrate 1.
To form The anode electrode 2 is made of Al, Au, Ag, M
g, Ni, Zn, V, In, Sn or the like, a compound selected from these simple substances such as ITO, or a conductive adhesive containing a metal filler, etc., and the light transmittance thereof is 80% or more. Desirably. The anode electrode 2 is preferably formed by a sputtering method, an ion plating method, a vapor deposition method, etc., but a coating method such as a spin coating method, a gravure coating method, a knife coating method, a screen printing method,
A printing method such as a flexographic printing method may be used. In the case of this embodiment, the ITO is deposited to a thickness of 2 by sputtering.
000 °.

Next, a hole transport layer 3 is formed on the upper surface of the transparent substrate 1 including the anode electrode 2. In this case, as a material of the hole transport layer 3, first, polyacrylic acid is made water-soluble in an ammonium salt, and specifically, polyacrylic acid (molecular weight: about 2000, manufactured by Aldrich) is added to 100 g of pure water.
10% w / w and 25% ammonia water (Wako Pure Chemical Industries)
The mixture was stirred at 80 ° C. for 3 hours using a heater to obtain a viscous solution. Next, in this solution,
As a protective colloid, a monomer insoluble in water, for example, a thiophene derivative, specifically, 1 g of 3,4-ethylenedioxythiophene and 0.5 g of 3-methylthiophene are added, mixed by a homomixer, and pre-emulsified. A solution was obtained.

Next, an oxidizing agent such as iron sulfate or persulfate is added to the solution, and pearl polymerization is performed.
2 g of ammonium persulfate dissolved therein and then heated at a temperature of 75 ° C. for 6 hours, followed by a temperature of 90 ° C.
Heated at ℃ for 1 hour, 0.1 ~ 10wt% (solid content concentration)
A clear solution was obtained. Next, 3% of a drying regulator IPA (EL grade, manufactured by Kanto Kagaku) and 0.05 g of γ-glycidoxypropyltrimethoxysilane (SH6040, manufactured by Dow Corning Toray Silicone) were added to the solution. Then, 300 g of pure water was further added, whereby an electrodeposition liquid for forming a hole transport layer was obtained. Then, the transparent substrate 1 is immersed in a tank in which the electrodeposition liquid is stored, electrodeposited on the anode electrode 2 of the transparent substrate 1 so as to have a thickness of 0.01 to 1 μm by an electrodeposition method, and then heated and dried. At a temperature of 60 to 200 ° C. for 1 minute to 2 hours to form a hole transport layer 3.

As described above, polyacrylic acid is made water-soluble in an ammonium salt, a water-insoluble monomer is dispersed as a protective colloid, and pearl polymerization is carried out to form an electrodeposition solution for forming a hole transport layer (a hole transporting layer). Molecular material dispersion).
In this case, when the protective colloid has an anionic property, electrophoresis in a liquid can be imparted. As a result, as described above, the hole transport layer 3 can be formed by the electrodeposition method. Further, since the hole transport layer 3 is made of polythiophene, it has conductivity. As a result, as described below, the light emitting layer 4 can be formed on the upper surface of the hole transport layer 3 by the electrodeposition method.

Next, the light emitting layer 4 is formed on the upper surface of the hole transport layer 3. In this case, as a material of the light emitting layer 4, first, a polymer having a structure composed of thiophene and a monomer copolymerizable with a thiophene monomer, specifically, RGB (red,
Green, blue) A paraphenylene derivative and a thiophene derivative copolymer that emit light are pulverized with a ball mill to have an average diameter of 0.0
Water-insoluble luminescent polymer dispersion fine particles classified to 5 to 0.2 μm (preferably 0.05 to 0.1 μm) were obtained. Next, the luminescent polymer dispersion fine particles were formed into micelles with a surfactant, and specifically, an aqueous solution in which a surfactant was mixed with 200 mg of the luminescent polymer dispersion fine particles,
Specifically, ferrocenylundecyl polyoxyethylene ether (Ferrocenyl-PE manufactured by Dojin Chemical Co., Ltd.)
G) 50 ml of a 5 mmol-0.2 M LiBr aqueous solution was added and stirred, whereby an electrodeposition solution for forming a light emitting layer was obtained.
Next, an electrodeposition method (micelle decomposition method) using this electrodeposition solution was applied to the hole transport layer 3 so as to have a thickness of 0.01 to 1 μm to form a light emitting layer 4.

As described above, when the light-emitting layer 4 is formed, the water-insoluble luminescent polymer dispersion fine particles are formed into micelles with a surfactant, and are solubilized by the micelle decomposition method, that is, inside the micelles. Since the light emitting layer material is electrodeposited by being deposited on the hole transport layer 3, the light emitting polymer insoluble in water can be electrodeposited to form the light emitting layer 4.

Here, the above-mentioned surfactant is an ionic surfactant such as an anion / cation / nonion type. Examples of anionic surfactants include fatty acid salts, alkyl sulfate salts, polyoxyethylene alkyl ether sulfate salts, alkyl allyl sulfate salts, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, and alkyl diphenyl ether diacids. It is a sulfonate, an alkyl phosphate, a naphthalene sulfonic acid formalin condensate, and a special polycarboxylic acid type polymer. Examples of the cationic surfactant include an alkylamine salt, a ferrocenylalkylammonium salt, and a quaternary ammonium salt. The nonionic surfactant is ferrocenylalkyl polyoxyethylene ether. In any case, since the above-mentioned surfactant has polarity, it has excellent electrophoretic properties and is suitable for the electrodeposition method.

Next, a cathode electrode 5 is formed on the upper surface of the light emitting layer 4 or the like.
To form The cathode electrode 4 is made of a metal having a low work function value capable of effectively injecting electrons into the light emitting layer 4, preferably Ca, Mg, Sn, In, Al, Ag, Li,
It is made of a simple substance such as a rare earth element or an alloy selected from these simple substances.

As described above, since the hole transport layer 3 and the light emitting layer 4 are formed by the electrodeposition method, the hole transport layer 3 and the light emitting layer 4 are formed in comparison with the case of forming by the vapor deposition method. In this case, the efficiency of the use of the materials for the purpose can be improved, and the cost can be reduced. In addition, in the electrodeposition method, a uniform organic film can be formed over a large area as compared with the vapor deposition method, and the size of the electroluminescent element can be increased. Furthermore, since a paraphenylene derivative or the like that emits RGB light can be used as a material of the light emitting layer 4,
The present invention can be applied to an additive-mixed white backlight, an RGB full-color display device, a CMY full-color display device, and the like.

[0016]

As described above, according to the present invention, the organic EL layer is formed by the electrodeposition method. The utilization efficiency of the material can be improved, the cost can be reduced, a uniform organic film can be formed over a large area, and the size of the electroluminescent device can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for manufacturing an electroluminescent device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode electrode 3 Hole transport layer 4 Light emitting layer 5 Cathode electrode

Claims (6)

[Claims] 1. A method for manufacturing an electroluminescent device in which a first electrode, an organic EL layer, and a second electrode are formed in this order on a transparent substrate, wherein the organic EL layer is formed by an electrodeposition method. Of manufacturing an electroluminescent device. 2. The organic electroluminescent device according to claim 1, wherein the organic EL layer comprises a hole transport layer formed by an electrodeposition method, and a light emitting layer formed thereon by an electrodeposition method. A method for manufacturing an electroluminescent device. 3. The method according to claim 2, wherein said hole transport layer is formed of a conductive hole transport layer material dispersed with an ionic protective colloid. . 4. The method according to claim 3, wherein the material of the conductive hole transport layer is a conductive polymer. 5. The method according to claim 2, wherein the light emitting layer is formed of a material obtained by converting a material of the light emitting layer into micelles with a surfactant. 6. The method according to claim 5, wherein the light emitting layer is formed by a micellar electrolysis method.