JP2002117984A - Organic el display device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL(electroluminescent) display device having high injection efficiency for injecting holes into a luminescence layer from a buffer layer and efficient luminescence by efficiently increasing the boundary area between the buffer layer and the luminescence layer per unit luminescent face. SOLUTION: A transparent electrode layer 5 is formed as an anode layer 5 on a transparent substrate 3, a sponge-like hole injection layer 8 is formed on it, a luminescent layer 10 is formed on the hole injection layer 8 to fill and cover the hole injection layer 8, and a cathode layer 11 is formed on the luminescent layer 10 to form this organic EL display device 1. The boundary area between the buffer layer 8 and the luminescent layer 10 per unit luminescent face is efficiently increased by forming the hole injection layer 8 into a sponge shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an organic EL display device used for display, illumination and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional organic EL display device 100 is shown in FIG.
As shown in FIG. 5, an anode layer 5, a buffer layer (hole transport layer) 7, a light emitting layer 9 and a cathode layer 11 are sequentially laminated on a transparent substrate 3 as a transparent electrode layer. A constant voltage power supply 13 is connected between the two layers 11 and 11 to form a main structure. In particular, an interface 15 between the buffer layer 7 and the light emitting layer 9 is formed in a planar shape.

[0003] Electrons are injected from the cathode layer 11 into the light emitting layer 9 by the application of a voltage from the constant voltage power supply 13 and are stored in the light emitting layer 9. Is supplied to the buffer layer 7 from
When the holes supplied to the buffer layer 7 are injected into the light emitting layer 9 from the interface 15, the holes are recombined with the electrons stored in the light emitting layer 9 to emit light.

[0004] At this time, the light emission luminance increases in accordance with the amount of holes injected from the buffer layer 7 into the light emitting layer 9 per unit light emitting surface, and is increased from the buffer layer 7 into the light emitting layer 9 per unit light emitting surface. The amount of holes increases according to the size of the area of the interface 15 per unit light emitting surface when the applied voltage is constant. Here, the “light emitting surface” is given by the bottom surface 3 a of the transparent substrate 3.

[0005]

However, as described above, when the interface 15 between the buffer layer 7 and the light emitting layer 9 is formed in a planar shape, the buffer layer 7 and the light emitting layer 9 per unit light emitting surface are not provided. Since the area of the interface 15 is not taken effectively, the injection rate of holes injected from the buffer layer 7 into the light emitting layer 9 is not so good, and light is efficiently emitted with respect to the applied voltage. Absent.

Accordingly, an object of the present invention is to improve the efficiency of hole injection from the buffer layer to the light emitting layer by efficiently increasing the area of the boundary between the buffer layer and the light emitting layer per unit light emitting surface. Accordingly, an object of the present invention is to provide an organic EL display device capable of efficiently emitting light and a method of manufacturing the same.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to an organic EL device in which at least a transparent electrode layer, an organic layer, and a back electrode layer are sequentially laminated on a transparent substrate. In the display device, the organic layer, a sponge-like hole injection layer formed on the transparent electrode layer,
A light emitting layer stacked on the hole injection layer so as to fill the inside of the hole injection layer.

According to a second aspect of the present invention, there is provided the method of manufacturing the organic EL display device according to the first aspect, wherein a hole injection layer solution is applied on the transparent electrode layer formed on the transparent substrate. A step of freezing the applied hole injection layer solution, a step of vacuum-drying the frozen hole injection layer solution in a frozen state to form the sponge-shaped hole injection layer, and a step of forming the hole injection layer. A step of applying a light emitting layer solution onto the hole injection layer so as to fill the inside of the substrate, and a step of drying the applied light emitting layer solution to form the light emitting layer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of an organic EL display device according to a first embodiment of the present invention.
FIGS. 2 to 5 are diagrams for explaining respective manufacturing steps of the main part of the organic EL display device according to the first embodiment of the present invention.

[0010] The organic EL display device 1 according to this embodiment.
As shown in FIG. 1, an anode layer 5 formed as a transparent electrode layer of ITO (indium tin oxide) or the like on a transparent substrate 3 such as a glass substrate, a buffer layer (hole transport layer) 8, A light emitting layer 10 and a cathode layer 11 formed of aluminum, calcium, or the like are sequentially laminated to form an organic E layer.
An L element is formed, and the positive electrode and the negative electrode of the constant voltage power supply 13 are connected to the anode layer 5 and the cathode layer 11, respectively. In this embodiment, an organic layer is formed by the buffer layer 8 and the light emitting layer 10.

The buffer layer 8 is formed of a high-molecular organic material such as polyethylene dioxythiophene (PEDT) into a porous sponge (sponge) having a predetermined thickness (for example, about 0.1 μm).

Since the buffer layer 8 is formed in a porous sponge shape, its entire surface is given by the sum of its outer surface and the inner surface of countless holes formed therein. The surface of the buffer layer having an area much larger than the unit area of the light emitting surface 3a is formed within each unit light emitting surface. That is, the surface area of the buffer layer 8 per unit light emitting surface is efficiently formed to be large.

The light-emitting layer 10 is made of an organic light-emitting material such as polyfluorene or polyphenylenevinylene.
The buffer layer 8 is filled in the innumerable holes formed inside the buffer layer 8 and covers the outer surface of the buffer layer 8.
Is formed to have a predetermined thickness (for example, about 0.1 μm) on the upper surface of the substrate.

In this state, the light emitting layer 10 includes the buffer layer 8
Is bonded to the buffer layer 8 via the outer surface of the substrate and the inner surfaces of the myriad of holes formed therein, whereby the area of the interface between the buffer layer 8 and the light emitting layer 10 per unit light emitting surface is reduced. It is efficiently formed large.

As a result, the holes supplied from the anode layer 5 to the buffer layer 8 by the voltage application of the constant voltage power supply 13 are injected from the entire interface of the buffer layer 8 when injected into the light emitting layer 10. A large amount is efficiently injected into the light emitting layer 10 at once with respect to the applied voltage, and the injection efficiency is improved.

Then, a large number of holes are efficiently injected into the light emitting layer 10 at once from the entire surface of the interface.
The ratio of holes injected into the light emitting layer 10 and recombined with electrons stored in the light emitting layer 10 increases, so that light is efficiently emitted.

Next, a method of manufacturing the organic EL display device 1 will be described with reference to FIGS.

First, an anode layer 5 having an appropriate thickness formed on a transparent substrate 3 is prepared. As shown in FIG. 2, a buffer layer solution (hole injection layer solution) is formed on the anode layer 5. )
8a to a predetermined thickness (for example, 0.1 μm) in a predetermined range by an appropriate method such as spin coating, printing, or injection coating.
About). Here, this buffer layer solution 8a
For the buffer layer, a material obtained by dissolving a polymer organic material such as polyethylene dioxythiophene (PEDT) as a material of the buffer layer 8 in a predetermined organic solvent is used.

Then, the buffer layer solution 8a applied on the anode layer 5 is frozen using liquid nitrogen or the like before it is dried, and dried under vacuum (so-called freeze-drying) in a frozen state to remove the solvent. Sublimate. As a result, the buffer layer solution 8a is removed from the frozen buffer layer solution 8a.
As shown in FIG. 3, only the solvent is removed without disintegrating the distribution state of the high molecular organic material dissolved in a.
The porous spongy buffer layer 8 is formed.

Then, as shown in FIG.
0a is formed into a porous spongy buffer layer 8 by an appropriate method such as spin coating, printing, or injection coating.
Is coated on the buffer layer 8 with a predetermined thickness so as to cover the outer surface of the buffer layer 8 and is dried to form the light emitting layer 10. Here, as the light emitting layer solution 10a, a solution prepared by dissolving an organic light emitting material such as polyfluorene or polyphenylenevinylene as a material of the light emitting layer 10 in a predetermined organic solvent is used.

Then, as shown in FIG. 5, a metal such as aluminum or calcium is deposited on the light emitting layer 10 by a vacuum deposition method or the like to form a cathode layer 11.

In this manner, the organic EL device, particularly, the buffer layer 8 and the light emitting layer 10 are formed.

According to the organic EL display device 1 configured as described above, the buffer layer 8 is formed in a porous sponge shape,
The light emitting layer 10 is filled in the buffer layer 8 and covers the outer surface of the buffer layer 8 so as to cover the buffer layer 8.
By being stacked on the upper surface, the area of the interface between the buffer layer 8 and the light emitting layer 10 per unit light emitting surface is efficiently increased, so that it is efficient with respect to the voltage applied by the constant voltage power supply 13. Many holes can be injected from the buffer layer 8 into the light emitting layer 10 at one time. Accordingly, the efficiency of hole injection from the buffer layer 8 to the light emitting layer 10 with respect to the applied voltage is increased, and light emission can be performed efficiently at a low voltage.

According to the above-described method for manufacturing an organic EL display device, the buffer layer 8 and the light-emitting layer 10 are formed of a high-molecular organic material. A simple film forming method such as coating is applied, whereby an organic EL element can be formed at low cost.

[0025]

According to the first aspect of the present invention, the buffer layer is formed in a porous spongy shape, and the light emitting layer is stacked on the buffer layer so as to fill the inside of the buffer layer. Since the area of the interface between the buffer layer and the light-emitting layer per unit light-emitting surface is efficiently increased, many holes can be efficiently formed at once with respect to the voltage applied by the constant voltage power supply. Injection from the transport layer into the light emitting layer becomes possible. Accordingly, the efficiency of hole injection from the hole transport layer to the light emitting layer with respect to the applied voltage is increased, and light emission can be performed efficiently at a low voltage.

According to the invention described in claim 2, according to claim 1
Can be formed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an E according to a first embodiment of the present invention;
FIG. 3 is a schematic sectional view of an L display device.

FIG. 2 is a block diagram showing an E according to the first embodiment of the present invention;
It is a figure explaining the process of applying a buffer layer solution in the manufacturing process of an L display.

FIG. 3 is a diagram illustrating a process of forming a buffer layer solution applied in FIG. 2 on a sponge-like buffer layer.

FIG. 4 is a view for explaining a step of forming a light emitting layer on the buffer layer formed in FIG. 3;

FIG. 5 is a view for explaining a step of forming a cathode layer on the buffer layer formed in FIG. 4;

FIG. 6 is a schematic sectional view of a conventional organic EL display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic EL display device 3 Transparent substrate 5 Anode layer 8 Buffer layer 8a Buffer layer solution 9,10 Light emitting layer 10a Light emitting layer solution 11 Cathode layer 13 Constant voltage power supply

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Junichi Ono 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (reference) 3K007 AB02 AB06 AB18 CA01 CB01 DA01 DB03 EB00

Claims (2)

[Claims] 1. An organic EL display device in which at least a transparent electrode layer, an organic layer, and a back electrode layer are sequentially laminated on a transparent substrate, wherein the organic layer has a sponge-like hole injection formed on the transparent electrode layer. An organic EL display device comprising: a layer; and a light emitting layer stacked on the hole injection layer so as to fill the inside of the hole injection layer. 2. The method for manufacturing an organic EL display device according to claim 1, wherein a step of applying a hole injection layer solution onto the transparent electrode layer formed on the transparent substrate is performed. Freezing the hole injection layer solution, forming the sponge-like hole injection layer by vacuum drying the frozen hole injection layer solution, and filling the inside of the hole injection layer. A step of applying a light emitting layer solution on the hole injection layer as described above, and a step of drying the applied light emitting layer solution to form the light emitting layer. Production method.