JP4045656B2 - Method for manufacturing electroluminescent element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method of an electroluminescent device, and more particularly, an organic electroluminescence (hereinafter, organic EL hereinafter) according to the method of manufacturing the light emitting device using the material.
[0002]
[Prior art]
As a conventional electroluminescent device, an anode electrode is formed on a glass substrate, and, for example, an organic layer composed of three layers of a hole transport layer, a light emitting layer, and an electron transport layer is formed thereon. An electroluminescent structure in which a very thin insulating film made of, for example, lithium fluoride (LiF) is deposited on the layer by vapor deposition, and a cathode electrode made of a low work function metal is formed on the insulating film. There are elements. In such an electroluminescent device, by applying a bias voltage positively, the electron injection efficiency is improved, and the light emission starting voltage and the luminous efficiency are improved as compared with an electroluminescent device having a structure without an insulating film. It has been known.
[0003]
An object of the present invention is to provide a manufacturing method for easily manufacturing an electroluminescent element.
[0004]
[Means for Solving the Problems]
The invention described in claim 1 includes a step of forming an electroluminescent layer on a transparent electrode, a step of adsorbing oxygen or ozone on the electroluminescent layer, and a step of forming a counter electrode on the electroluminescent layer. Applying an electric field in a direction opposite to the electric field emitted from the electroluminescent layer between the counter electrode and the transparent electrode to oxidize the interface of the counter electrode joined to the electroluminescent layer to form an insulating thin film And a step of performing.
[0011]
Therefore, in the first aspect of the present invention, oxygen and ozone once adsorbed to the electroluminescent layer need only be electrically chemically reacted with the interface of the counter electrode. An increase in the number can be avoided. In addition, the film thickness of the insulating thin film can be controlled by the amount of oxygen and ozone adsorbed, and an insulating thin film having a very thin film thickness can be formed. Further, since the insulating thin film oxidizes the interface of the counter electrode bonded to the electroluminescent layer, the bonding property of the interface between the insulating thin film and the counter electrode is good, so that a high carrier injection property can be obtained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the details of the electroluminescent device and the method for manufacturing the same according to the present invention will be described based on embodiments shown in the drawings.
[0013]
(Embodiment 1)
1 to 3 show Embodiment 1 of an electroluminescent element according to the present invention. First, the manufacturing method of this embodiment is demonstrated using FIGS. As shown in FIG. 1, a transparent electrode 2 made of ITO (indium tin oxide) or In ₂ O ₃ (ZnO) _m (where m> 0) is formed on a glass substrate 1 as a predetermined electrode pattern. To form. The patterning of the transparent electrode 2 can be performed using a photolithography technique and an etching (dry etching or wet etching) technique after the conductive film is deposited.
[0014]
Thereafter, as shown in the figure, a hole transport layer 3, a light emitting layer 4, and an electron transport layer 5 are sequentially laminated on the transparent electrode 2. In the present embodiment, the electron transport layer 5 is formed of tris (8-hydroxyquinoline) aluminum. The light emitting layer 4 is composed of 96% by weight of 4,4′-bis (2,2-diphenylvinylene) biphenyl and 4% by weight of 4,4′-bis (2-carbazolvinylene) biphenyl. Further, the hole transport layer 5 is formed of N, N′-di (α-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine. The organic EL layer 6 is constituted by the three layers of the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5. In addition, in the organic EL layer 6 of these laminated structures, light in a blue wavelength region is generated when a voltage is applied.
[0015]
Next, as shown in FIG. 1, a metal film 7 having a thickness of 10 nm or less made of MgAg which is a low work function metal is deposited on the electron transport layer 5. In the vapor deposition of the metal film 7, a hard mask on which a desired electrode pattern is formed is used.
[0016]
Subsequently, as shown in FIG. 2, the metal film 7 is oxidized by bringing the metal film 7 into contact with ozone (O ₃ ) and / or oxygen gas, thereby changing to an insulating film 7 A made of MgO: Ag ₂ O. .
[0017]
Thereafter, using a hard mask again, MgAg is vapor-deposited to a predetermined thickness to form a back electrode 7B as a cathode electrode, thereby completing the electroluminescent element 8 of the present embodiment.
[0018]
In this embodiment, since the material before the insulating film 7A is oxidized is the same MgAg as that of the back electrode 7B, the adhesion between the back electrode 7B and the insulating film 7A is extremely high, and oxygen and moisture are prevented from entering the interface. The effect to do becomes high. Further, by interposing an extremely thin (10 nm or less) insulating film 7A between the back electrode 7B as the cathode electrode and the electron transport layer 5, the electron injection efficiency from the back electrode 7B to the electron transport layer 5 is improved. As a result, it is possible to improve the light emission starting voltage and the light emission efficiency as compared with an electroluminescent device having a structure without an insulating film.
[0019]
(Embodiment 2)
FIG. 4 is a cross-sectional view of the main part showing Embodiment 2 of the electroluminescent element according to the present invention. In the present embodiment, the transparent electrode 2 is formed on the glass substrate 1 in the same manner as in the first embodiment, and then the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5 are stacked to form the organic EL layer 6. Form. Thereafter, in the second embodiment, oxygen (O ₂ ) gas and ozone (O ₃ ) gas are brought into contact with the organic EL layer 6 to adsorb O ₂ and O ₃ into the organic EL layer 6.
[0020]
Next, MgAg is vapor-deposited on the electron transport layer 5 to pattern the back electrode material film 9. Thereafter, as shown in FIG. 4, a reverse bias voltage is applied between the transparent electrode 2 and the back electrode material film 9. By applying this reverse bias, O ₂ and O ₃ having a dipole moment in the relatively porous organic EL layer 6 gather at the interface of the back electrode material film 9 with the electron transport layer 5. In the reverse bias state, the electron potential of the back electrode material film 9 is lower than the potential of the outermost electrons of O ₂ and O ₃ , so that oxygen atoms are easily covalently bonded to the back electrode material film 9 and the back electrode material. The film 9 becomes a back electrode 9B and a thin insulating film 9A of 10 nm or less oxidized on the lower surface thereof. In this way, the electroluminescent element 8 in which the very thin insulating film 9A is interposed between the back electrode 9B and the electron transport layer 5 is completed.
[0021]
In the second embodiment, the film thickness of the insulating film 9A formed by oxidation can be controlled by the amount of O ₂ or O ₃ adsorbed in the organic EL layer 6, and the insulating film having an extremely thin film thickness can be controlled. Can be formed uniformly in the plane. In particular, in this embodiment, since the insulating film 9A and the back electrode 9B are continuously formed, it is possible to prevent oxygen and moisture from entering the interface from the outside. Further, the insulating film 9A having a uniform and extremely thin (10 nm or less) film thickness is interposed between the back electrode 9B serving as the cathode electrode and the electron transport layer 5, so that the back electrode 7B is transferred to the electron transport layer 5. The electron injection efficiency can be improved, and the light emission starting voltage and the light emission efficiency can be improved as compared with an electroluminescent device having a structure without an insulating film.
[0022]
As mentioned above, although Embodiment 1 and Embodiment 2 were demonstrated, this invention is not limited to these, The various change accompanying the summary of a structure is possible. For example, in Embodiment 1 and Embodiment 2 described above, MgAg is used as the material of the back electrode 7B and the back electrode material film 9, but in addition to this, a conductive material containing Li, Ca, Mg, Y, etc., Ag Any metal that can form an oxide, such as Al, AlLi (aluminum lithium), is not limited thereto. In the above-described embodiment, the transparent electrode 2 is formed on the glass substrate 1. However, the back electrode 7 </ b> B and the back electrode material film 9 may be formed on the glass substrate 1. In this case, after the back electrode 7B and the back electrode material film 9 are formed of the above-described materials, the electron transport layer 5 is vapor-deposited thereon under an oxygen or ozone atmosphere to thereby provide an interface between the back electrode 7B and the electron transport layer 5. An insulating film 7A can be formed. Furthermore, in the above-described embodiment, the organic EL layer 6 having a three-layer structure is used. However, a single-layer structure or a multilayer structure having three or more layers may be used. In the above-described embodiment, the metal film 7, the back electrode 7B, and the back electrode material film 9 are formed by vapor deposition, but may be formed by sputtering or ion plating.
[0023]
【The invention's effect】
As is apparent from the above description, according to the present invention, an electroluminescent element with improved light emission starting voltage and light emission efficiency can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a principal part showing a manufacturing process of Embodiment 1 of an electroluminescent element according to the present invention.
2 is a cross-sectional view of main parts showing a manufacturing process of Embodiment 1. FIG.
3 is a cross-sectional view of a main part of the electroluminescent element of Embodiment 1. FIG.
FIG. 4 is a cross-sectional view showing a main part of a manufacturing process of Embodiment 2 of the electroluminescent element according to the present invention.
5 is a cross-sectional view of main parts showing a manufacturing process of Embodiment 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent electrically conductive film 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Organic EL layer 7 Metal film 7A Insulating film 7B Back electrode 8 Electroluminescent element 9 Back electrode material film

Claims (1)

Forming an electroluminescent layer on the transparent electrode; adsorbing oxygen or ozone to the electroluminescent layer; forming a counter electrode on the electroluminescent layer; the counter electrode and the transparent electrode Forming an insulating thin film by oxidizing an interface of the counter electrode joined to the electroluminescent layer by applying an electric field in a direction opposite to the electric field emitted from the electroluminescent layer. A method for manufacturing an electroluminescent element.

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