JP2003308971A - Method of manufacturing organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element in which little development and growth of a dark spot are made, a drive circuit can be simplified, and a long life is obtained. <P>SOLUTION: With respect to a method of manufacturing the organic EL element which has a production process in which an organic EL layer and a transparent electrode are laminated in turn on a transparent electrode (a positive electrode 4) formed on a transparent substrate 2, before the production process in which the organic EL layer and the transparent electrode are laminated in turn, the maximum difference of elevation X on a surface of the transparent electrode (the positive electrode 4) formed on the transparent substrate is ground down to 40 nm or less. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an organic electroluminescent element (organic EL element) which emits light when a voltage is applied, and more specifically, it is a dot-shaped non-light emitting portion (dark spot). The present invention relates to a method for manufacturing an organic EL device having less emission and improved emission life.

[0002]

2. Description of the Related Art Organic EL devices emit light at a relatively low voltage,
In addition, since it is easy to manufacture, it is a light-emitting element that is expected to be promising. The device life, which has been considered to be a problem in practice, has been improved considerably recently.

An example of the structure of a conventional organic EL device is shown in FIG. This organic EL device comprises indium tin oxide (IT) which is a transparent electrode sequentially formed on a transparent substrate 2 such as glass.
O) or the like anode 4, hole injection layer 6, hole transport layer 8,
Electron transporting light emitting layer 10, first cathode layer 14, second cathode layer 1
6 are laminated.

In such an organic EL element, the hole injection layer 6, the hole transport layer 8 and the electron transport light emitting layer 10 constitute an organic EL layer 12. In addition, the first cathode layer 14 and the second cathode layer 16 form a cathode 18.

The thickness of the conventional organic EL layer is usually 1
It is at least 00 nm.

Further, as shown in FIG. 2, an airtight case 90 is attached to the upper surface of the transparent substrate 2 by an adhesive 9 so as to cover the above-mentioned EL element.
2 is used for adhesion to obtain a product organic EL element. Here, a desiccant 9 such as BaO or CaO is formed on the inner surface of the hermetic case 90
4 is attached.

In the above organic EL element, the holes and the electrons respectively injected from the pair of electrodes consisting of the anode 4 and the cathode 18 are recombined in the organic EL layer 12 to emit light, and the light is emitted from the transparent substrate. The light is transmitted through 2 and emitted toward the outside of the organic EL element.

In order to manufacture the above organic EL device, first, the anode 4 made of ITO is formed on the transparent substrate 2. As the forming means, well-known means such as sputtering, EB vapor deposition, and ion plating are used.

Next, the above layers are sequentially laminated.
Laminating means, laminating thickness and the like are known per se to those skilled in the art.

The product organic EL element manufactured as described above may have a dark spot when it emits light. The dark spots continue to grow in proportion to the time for which the organic EL element emits light, and after a certain time, the entire organic EL element suddenly becomes unable to emit light.

Further, the light emission intensity decreases as the light emission becomes longer, so that in order to keep the light emission intensity constant, it is necessary to gradually increase the operating voltage applied to the organic EL element to compensate for this. However, in this case, there is a problem that the drive circuit configuration of the organic EL element becomes complicated.

[0012]

The inventors of the present invention have made various investigations to solve the above-mentioned problems, and as a result, the unevenness of the anode surface, which is a transparent electrode formed on a transparent substrate, causes the above-mentioned problems. I found that. The present invention has been completed based on the above findings, and its purpose is to reduce the generation and growth of dark spots, and as a result, simplify the circuit for increasing the operating voltage and extend the life of the organic EL. It is to provide an element.

[0013]

In order to solve the above problems, the present invention has the constitution described below.

[1] In a method of manufacturing an organic EL device having a step of sequentially stacking an organic EL layer and a transparent electrode on a transparent electrode formed on a transparent substrate, a step of sequentially stacking the organic EL layer and the transparent electrode The maximum height difference of the transparent electrode surface formed on the transparent substrate is 10 to 40 nm.
A method for manufacturing an organic EL device, which comprises a step of polishing.

[2] The method for producing an organic EL device according to [1], wherein the method for polishing the transparent electrode is a mechanical polishing method or a chemical polishing method.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The method for manufacturing an organic EL element according to the present invention goes through substantially the same manufacturing steps as a conventional method for manufacturing an organic EL element. In the manufacturing method of the present invention, the step of polishing the height difference of the anode manufactured on the upper surface of the transparent substrate to 10 to 40 nm is added before the step of laminating the organic EL layer and the cathode on the anode. Different from the manufacturing method.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The organic EL element manufactured by the manufacturing method according to the present invention has the same basic structure as that of the conventional organic EL element. Therefore, the manufacturing method of the present invention will be described below with reference to FIG.

Here, the transparent substrate 2 can be used without particular limitation as long as it can transmit visible light. Specific examples include a glass plate and a plastic plate. The thickness of the transparent substrate is preferably 0.1 to 2 mm.

The anode 4, which is a transparent electrode formed on the transparent substrate 2, is made of a conductive transparent material such as indium tin oxide (ITO). The thickness of the anode is 50-600
nm is preferred. This anode can be manufactured by a conventional method by a known means such as sputtering, EB vapor deposition, and ion plating.

In the case of forming the anode by sputtering, first, a sputtering target made of indium-tin-oxygen is installed in a sputtering apparatus, and an inert gas such as argon and, if necessary, oxygen gas are used as the sputtering gas. Sputtering is performed by applying a DC or RF electric field.

The sputtering conditions are the substrate temperature,
There are control parameters such as the sputtering gas pressure, the oxygen partial pressure in the sputtering gas pressure, and the applied electric field strength. These parameters need to be selected for lower anodic resistivity. The setting of this parameter depends on the type of transparent substrate used, the device used, and the like. Specifically, the substrate temperature is 200 ° C., the sputtering gas (Ar + O ₂ ) pressure is 1.3 × 10 ⁻¹ Pa, and the oxygen concentration is 0.1.
%, DC power 600 W can be shown as an example.
This condition itself is known.

When the anode is formed by EB vapor deposition, for example, a glass substrate and a vapor deposition material (indium tin oxide; 95 mass% indium oxide, 5 mass% tin oxide) tablets are placed in an EB vapor deposition apparatus equipped with an oxygen gas introduction mechanism. Etc. can be exemplified). After that, the inside of the EB evaporation system was exhausted by a rotary pump and a diffusion pump (6.7 × 10 ⁻⁵ P
a), heating the substrate to 300 ° C. Oxygen gas is introduced into the apparatus, and the oxygen gas pressure is 1.3x10 ^{-3 to} 1.3x10 ^-1.
Adjust to Pa and form a film. Film formation rate is 0.5-1 nm
/ Sec.

As shown in FIG. 3, the surface of the anode 4 just formed on the transparent substrate 2 has many minute irregularities. These can be observed by an atomic force microscope (AFM).

Here, of these concave and convex portions, the tip 20 of the highest convex portion (the convex portion most protruding from the anode surface) and the bottom 2 of the deepest concave portion (the concave portion deepest from the anode surface) are shown.
The difference in the direction perpendicular to the anode surface with respect to 2 is defined as the height difference X.

In the present invention, the surface of the anode 4 is polished so that the height difference on the entire surface of the anode is 10 to 40 nm, preferably 20 to 30 nm. Further, as the polishing method, a mechanical polishing method and a chemical mechanical polishing method are preferable.

FIG. 4 shows an example of a mechanical polishing apparatus. In FIG. 4, 40 is a platen that rotates in a horizontal plane,
A polishing cloth 42 is attached to the upper surface. The transparent substrate 44 with the anode 46 facing downward is pressed against the upper surface of the platen 40 by using the holder 45, whereby the surface of the anode 46 can be polished. Incidentally, 48 is a polishing agent, and a polishing cloth 42
Supply on. As the abrasive, cerium oxide, alumina, diamond powder and the like are preferable. After polishing in this manner to make the height difference of the anode surface 10 to 40 nm,
A hole injection layer 6 is laminated on the polished surface of the anode 4.

As the constituent material of the hole injection layer 6, a porphyrin compound (a compound disclosed in JP-A-63-295965 and the like) and an aromatic tertiary amine compound can be used.

Typical examples of the porphyrin compound are porphyrin, 1,10,15,20-tetraphenyl-21H, 23H-porphyrin copper (II), 1,
10,15,20-Tetraphenyl-21H, 23H
-, Porphyrin zinc (II), 5,10,15,20
-Tetrakis (pentafluorophenyl) -21H, 2
3H-porphyrin, silicon phthalocyanine oxide, aluminum phthalocyanine chloride, phthalocyanine (no metal), dilithium phthalocyanine, copper tetramethyl phthalocyanine, copper phthalocyanine (CuP
c), chromium phthalocyanine, zinc phthalocyanine, lead phthalocyanine, titanium phthalocyanine oxide,
Examples thereof include Mg phthalocyanine and copper octamethyl phthalocyanine.

As a typical example of the aromatic tertiary amine compound, 4,4'4 "-tris (3-methylphenylphenylamino) triphenylamine (m-MTDAT) is used.
A), 4,4'4 "-tris (1-naphthylphenylamino) triphenylamine (TNATA), etc.,
N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl, N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine, 2,2-bis (4-di-p
-Tolylaminophenyl) propane, 1,1-bis-4
-Di-p-tolylaminophenyl) cyclohexane,
N, N, N'N'-tetra-p-tolyl-4,4'-diaminophenyl, 1,1-bis- (4-di-p-tolylaminophenyl) -4-phenylcyclohexane, bis (dimethylamino) 2-Methylphenyl) phenylmethane, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N'-diphenyl-N, N'-di (4-
Methoxyphenyl) -4,4'-diaminobiphenyl,
N, N, N, N'-tetraphenyl-4,4'-diaminophenyl ether, 4,4'-bis- (diphenylamino) quadphenyl, 4,4'4 "-tris (3-
Methylphenylamine) triphenylamine and the like.

The hole injection layer 6 has a thickness of 10 to 40 n.
m is preferable, and 20 to 30 nm is particularly desirable.

Next, the hole transport layer 8 is formed on the hole injection layer 6.
Are stacked. The hole transport layer 8 can be made of α-naphthylphenyldiamine (NPD) or the like. The thickness of the hole transport layer 8 is preferably 5 to 45 nm, and 10 to 40 nm.
Is more preferable.

Further, the electron transporting light emitting layer 10 is laminated on the upper surface of the hole transporting layer 8. The electron-transporting light-emitting layer 10 is a tris (8-quinolinolato) aluminum complex (Alq3).
Etc. The thickness of the electron-transporting light emitting layer 10 is preferably 5 to 45 nm, more preferably 10 to 40 nm.

In the present invention, the hole injection layer 6, the hole transport layer 8, the electron transport light emitting layer 10 and the organic EL layer 12 are provided.
Collectively.

A first cathode layer 14 is laminated on the electron transporting light emitting layer 10. The first cathode layer is lithium fluoride (Li
F). The thickness is preferably 0.1 to 2 nm.

A second cathode layer 16 is laminated on the first cathode layer 14. The second cathode layer 16 is preferably aluminum.
The thickness is preferably 15 to 200 nm.

The first cathode layer 14 and the second cathode layer are collectively referred to as the cathode 18. In addition, each layer can be formed by a method known to those skilled in the art, such as a sputtering method or a vacuum deposition method.

In the above description, as the organic EL layer,
Hole injecting layer 6, hole transporting layer 8 and electron transporting light emitting layer 10
However, the present invention is not limited to this, and the present invention includes all of various organic EL layers configured to have functions such as hole transport, electron transport, and light emission.

Hereinafter, the present invention will be described more specifically with reference to Examples.

[0040]

(Examples) (Examples 1 to 4) Organic EL having a structure shown in FIG.
The device was manufactured. Glass transparent substrate thickness 0.7 mm, anode (ITO) thickness 150 nm (transmittance 85%, surface resistance 2
0 Ω / □, hole injection layer (CuPc) thickness 30 nm, hole transport layer (NPD) thickness 35 nm, electron transporting light emitting layer (Alq3) thickness 35 nm, first cathode (LiF) 0.5.
nm, and the thickness of the second cathode (Al) was 100 nm. The anode was formed by the EB vapor deposition method. The cathode was formed by vapor deposition.

The area of the light emitting surface is 5 mm × 5 mm.
The airtight case made of stainless steel as shown in (4) was filled with nitrogen gas and sealed. BaO was attached as a desiccant in the airtight case.

In the production of this organic EL element, after laminating an anode (ITO) on a transparent substrate, the surface of the anode was polished using the polishing apparatus shown in FIG. Cerium oxide was used as the polishing agent.

A DC voltage was applied to the manufactured organic EL device, and the luminance half-life at 200 cd / m ² was measured. The results are shown in Table 1 below and FIGS. (Comparative Examples 1 to 4) In Comparative Examples 1 and 2, an organic EL device was manufactured in the same manner as in Example 2 except that the ITO height difference was not within the range of the present invention. In Comparative Examples 3 and 4, an organic EL device was manufactured in the same manner as in Example 2 except that the step of polishing the surface of the anode was omitted. The luminance half-life was measured in the same manner as in Example 1. The obtained results are shown in Table 1 below and FIGS. In Comparative Example 1, since the height difference of the electrode surface is smaller than 10 nm, the operating voltage is high.
In Comparative Example 4, since the electrode surface was not polished,
The brightness half-life is short even though the height difference of the electrode surface is within the range of the present invention.

[0044]

[Table 1]

[0045]

According to the method of manufacturing an organic EL device of the present invention, the surface of the anode is polished to reduce the height difference of the surface to 40 nm.
The resulting organic EL device has a smoothing step as follows.
The device has few dark spots and growth. Therefore, the organic EL element manufactured by the present invention has a long luminance half-life and a long life. Further, since the growth of dark spots is small, the fluctuation of the operating voltage is small for a long period. Therefore, the drive circuit configuration of the organic EL element can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram showing an example of the configuration of an organic EL element.

FIG. 2 is a schematic explanatory diagram showing an example of the configuration of a product organic EL element.

FIG. 3 is a conceptual diagram showing a height difference on the surface of an anode.

FIG. 4 is a schematic explanatory view showing an example of a polishing apparatus used for polishing the surface of an anode.

FIG. 5 is a graph showing the relationship between the luminance half-life and the height difference of the transparent electrode surface in Examples and Comparative Examples.

FIG. 6 is a graph showing the relationship between the driving voltage and the height difference of the transparent electrode surface in Examples and Comparative Examples.

[Explanation of symbols]

2 transparent substrate 4 anode 6 Hole injection layer 8 Hole transport layer 10 Electron-transporting light-emitting layer 12 Organic EL layer 14 First cathode layer 16 Second cathode layer 18 cathode 90 airtight case 94 Desiccant

Continued front page    (72) Inventor Yoshio Iwata             1-8 Nakase, Nakase, Mihama-ku, Chiba City, Chiba Prefecture             Ico Instruments Co., Ltd. (72) Inventor Mitsuru Suginoya             1-8 Nakase, Nakase, Mihama-ku, Chiba City, Chiba Prefecture             Ico Instruments Co., Ltd. (72) Inventor Yusuke Izumisawa             10-2 Otosetsu-cho, Kanazawa-ku, Yokohama-shi, Kanagawa (72) Inventor Hidefumi Omori             10-3 Otosetsu-cho, Kanazawa-ku, Yokohama-shi, Kanagawa (72) Inventor Toshihiro Koike             2-19-5 Nakanoshima, Tama-ku, Kawasaki City, Kanagawa Prefecture             issue F term (reference) 3K007 AB08 AB11 AB18 CB01 DB03                       FA00

Claims (2)

[Claims] 1. A method of manufacturing an organic EL device, which comprises a step of sequentially laminating an organic EL layer and a transparent electrode on a transparent electrode formed on a transparent substrate, the method comprising the steps of laminating the organic EL layer and the transparent electrode sequentially. A method for manufacturing an organic EL device, which comprises a step of polishing the surface of the transparent electrode formed on the transparent substrate to a maximum height difference of 10 to 40 nm. 2. The method for producing an organic EL device according to claim 1, wherein the method for polishing the transparent electrode is a mechanical polishing method or a chemical polishing method.