JPH1187052A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new structure for taking out a cathode to the outside, in an organic EL element having a large amount of the cathodes of fine pitch like the organic EL of, for instance, graphic type. SOLUTION: On a substrate 1, many belt-shaped anodes 2 are provided. The anode 2 is formed by ITO. On the anode 2, a positive hole transport layer 6, organic emitting layer 7, and a cathode 8 are provided. A cathode 8, composed of an alloy of Mg, Ag, has a plurality of belt shapes orthogonal, to the anode 2. On the substrate 1, many belt-shaped take out electrodes 5 are provided. The take out electrodes 5, in parallel to the cathode 8, has a pitch and the number of electrodes corresponding to the cathode 8. In the other end of the cathode 8, a connection end part 9 of width narrower than the cathode 8 is formed, to be connected onto an end part of the corresponding take out electrode 5. Relating to the take out electrode 5 of broad width, by a structure connecting a narrow connection end part corresponding thereto by an equal pitch, even when a position forming the cathode 8 and the connection end part 9 is deviated in a belt width direction, a trouble of electric connection such as changing connection resistance in a connection part between the take out electrode 5 and the cathode 8 is prevented from being easily generated. The structure can correspond to a fine pitch of the cathode, without a position deviation problem relating to taking out of the cathode to outside an element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device having an organic light emitting layer (hereinafter referred to as an organic EL device).
Element). In particular, the present invention generally relates to an organic EL device having a cathode formed by vapor deposition of a metal.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin film containing a fluorescent organic compound is sandwiched between an electron injecting electrode and a hole injecting electrode, and electrons and holes are injected into the thin film and recombined. This is a display element that generates excitons (excitons) and emits light (fluorescence / phosphorescence) when the excitons are deactivated.

One of the basic structures of the organic EL device is shown in FIG.
It was shown to. This organic EL element is made of a glass substrate 100.
The upper anode 101 is provided with ITO (Indium Tin Ox).
ide), a triphenylamine derivative (Diamine) as the hole transport layer 102, and tris (8-quinolilite) aluminum (III) (A) as the organic light emitting layer 103.
lq ₃ ), and an alloy of magnesium and silver is used as the cathode 104. The thickness of each organic layer is about 50 nm. Each layer is formed by vacuum evaporation. This organic EL
In the element, when a DC voltage of 10 V is applied between the cathode 104 and the anode 101, green light emission of about 1000 cd / m ² is obtained.

In the organic EL device, a metal material having a small work function (eg, Li, Na,
Mg, Ca, etc.) as a simple substance, or Al: Li,
It is used as an alloy such as Mg: In and Mg: Ag.
In the organic EL device having the basic structure described above, the anode 10
In order to connect the cathode 1 and the cathode 104 to an external driving circuit, the cathode 104 needs to be drawn out onto the substrate 100.
However, a metal material having a small work function used for the cathode has a high activity and is easily oxidized. Therefore, when used for a terminal portion for connection to an external circuit, peeling, deterioration, and high resistance due to oxidation are likely to occur.

[0005] The thickness of the cathode may be 200 nm or less, but when used as a terminal, the mechanical strength becomes insufficient and disconnection or poor contact may occur due to scratches.

For these reasons, it has been difficult to use the cathode metal as it is as a connection terminal with an external circuit in the conventional organic EL device.

FIG. 4 is a cross-sectional view of an organic EL device described in Japanese Patent Application Laid-Open No. 3-274694. This organic EL has a structure in which a cathode 104 is taken out on a substrate 100 provided with an anode. 4, portions corresponding to the basic structure of the organic EL element described above are denoted by the same reference numerals as in FIG. 3, and description thereof will be omitted. In FIG. 4, an extraction electrode 105 for a cathode 104 is formed on a substrate 100, and the insulating layer 10 covers a part of the anode 101 and the extraction electrode 105.
6 are formed. An opening 107 for extracting light emission and a through hole 108 for connecting the extraction electrode 105 and the cathode 104 are formed in a part of the insulating layer 106. The cathode 104 extends to the through hole 108 and is connected to the extraction electrode 105.

[0008]

As shown in FIG.
According to the structure in which the cathode 104 of the organic EL element and the extraction electrode 105 are connected via the through hole 108, the organic EL element having a large number of cathodes formed at a fine pitch,
For example, in the case of a graphic type organic EL in which a matrix is formed by intersecting a striped anode and a cathode, the following problem occurs. That is, such organic E
In the case of L, a large number of through holes must be formed at a fine pitch corresponding to each cathode and connected to the corresponding extraction electrode via each through hole, which is required for a graphic type organic EL. The pitch of the cathode is quite fine, and it has been technically difficult to form through holes at such a fine pitch in the insulating layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel structure for taking out a cathode in an organic EL device having a large number of fine pitch cathodes, such as a graphic type organic EL.

[0010]

An organic electroluminescence device according to claim 1 comprises a substrate 1, an anode 2 provided on an inner surface of the substrate 1, and a hole formed on the anode 2. In an organic electroluminescence device having a transport layer 6, a light emitting layer 7 formed on the hole transport layer 6, and a cathode 8 formed on the light emitting layer 7, a material different from the cathode 8 And a connection terminal formed on the inner surface of the substrate 1 at an end of the cathode 8 and having a smaller line width than the extraction electrode 5 and connected to an end of the extraction electrode 5. And a part 9.

An organic electroluminescent device according to claim 2, wherein the substrate 1, a plurality of strip-shaped anodes 2 formed on the inner surface of the substrate 1 at predetermined intervals along a predetermined direction, and Hole transport layer 6 formed on layer 2
A plurality of strip-shaped light-emitting layers 7 formed on the hole transport layer 6 at predetermined intervals along a direction intersecting with the anode 2 on the light-emitting layer 7. In the organic electroluminescence device having the cathode 8, a plurality of extraction electrodes 5 made of a material different from the cathode 8 and formed on the inner surface of the substrate 1 substantially in parallel with the cathode 8, A connection end 9 is formed at an end with a smaller line width than the extraction electrode 5 and is connected to an end of each extraction electrode 5.

According to a third aspect of the present invention, there is provided the organic electroluminescence element according to the first or second aspect, wherein the extraction electrode 5 is made of a material having a work function of 4.5 eV or more.

According to a fourth aspect of the present invention, in the organic electroluminescent element according to the third aspect, the material having a work function of 4.5 eV or more is made of ITO (Indium Tin Oxid).
e), ZnO: Al, SnO ₂ : Sb, In ₂ O ₃ , A
u is a substance selected from the group consisting of u.

[0014]

FIG. 1 shows an example of an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIG. 1, an anode 2 is formed on a glass substrate 1. The anode 2 of the present example is in the form of a number of strips arranged at a predetermined pitch in parallel with each other. The anode 2 in this example is made of ITO (Indium)
Tin Oxide). In addition, any material having a work function of 4.5 eV or more can be used as the anode 2. For example, ZnO: Al, SnO ₂ : Sb, In ₂
O ₃ , Au or the like can be used. An insulating layer 3 is formed in a frame shape around the anode 2, and the inside of the frame of the insulating layer 3 provided with the anode 2 is a display area. Each of the anodes 2 is drawn out of the frame of the insulating layer 3 and each of the wiring conductors 4
It is connected to the. The wiring conductor 4 is connected to a negative terminal of an external drive circuit.

On the substrate 1, an extraction electrode 5 is formed in contact with the outer edge of the insulating layer 3. Extraction electrode 5
Are a number of strips arranged in parallel at a predetermined pitch. The number and pitch are adjusted to the cathode 8 described later. The extraction electrode 5 is arranged orthogonal to the anode 2. The extraction electrode 5 is made of a material different from that of a cathode 8 described later. In this example, the extraction electrode 5 is made of the same material as the anode 2, that is, ITO. Therefore, in this example, the anode 2 and the extraction electrode 5 can be patterned by the same process. The extraction electrode 5 is connected to a negative terminal of an external drive circuit.

A hole transport layer 6 is provided on the anode 2. The hole transport layer 6 is made of, for example, a triphenylamine derivative (Diamine). The edge of the hole transport layer 6 is deposited on the insulating layer 3.

On the hole transport layer 6, an organic light emitting layer 7
Is provided. As the organic light emitting layer 7, a substance having a desired emission color may be selected according to the application. In this example, for example, tris (8-quinolilite) aluminum (III)
(Alq ₃ ) was used.

On the organic light emitting layer 7, a cathode 8 is provided. The cathode 8 is made of, for example, an alloy of magnesium and silver. The cathode 8 in the present example is a plurality of strips formed at predetermined intervals along a direction orthogonal to the anode 2.

Therefore, a matrix display area is constituted by a number of strip-shaped anodes 2 and a number of strip-shaped cathodes 8 crossing the anodes. By providing display signals to desired cathodes 8 and anodes 2, it is possible to selectively emit light in the area of the organic light emitting layer 7 corresponding to any intersection of the matrix, thereby performing any graphic display.

One end of each cathode 8 extends over the insulating layer 3 and reaches the upper surface of the extraction electrode 5. As shown in FIG. 2, a connection end 9 having a width smaller than that of the cathode 8 is continuously formed at one end of each of the cathodes 8. It is connected on the end of the electrode 5.

The setting of the dimensions of each part of the extraction electrode 5 and the connection end 9 will be described. First, the interval A between the extraction electrodes 5 is narrowed to the limit in the electrical insulation characteristics and the pattern forming process. Specifically, 10-5
The range of 0 μm is good. On the other hand, the line width B of the connection end 9 formed by mask vapor deposition is set to the minimum line width calculated from electrical characteristics such as voltage drop and heat generation. Specifically, 5
The range of 0 to 100 μm is good.

More specifically, the cathode 8 and the extraction electrode 5
Is assumed to be 0.6 mm. The width of the extraction electrode 5 is 0.55 mm, the interval between adjacent extraction electrodes 5 is 0.05 mm (50 μm), and the width of the connection end 9 of the cathode 8 is 0.1 mm (100 μm). When the cathode 8 and the connection end 9 are formed at the end of the process and connected to the extraction electrode 5, the pattern of the cathode 8 and the connection end 9 is shifted in the width direction (the direction orthogonal to the longitudinal direction of the strip-shaped pattern). . For this reason, as in this example, the wide extraction electrode 5
On the other hand, if the structure is such that the thin connecting ends 9 corresponding to the same pitch are connected to each other, even if the formation positions of the cathode 8 and the connecting end 9 are displaced, the connection resistance of the connection between the extraction electrode 5 and the cathode 8 is reduced. Is less likely to interfere with the electrical connection, such as changes in In the dimension example described above, the positioning tolerance was ± 0.225 mm, and no change was observed in the connection resistance of the connection portion between the extraction electrode 5 and the cathode 8. On the other hand, in the conventional structure, when the pitch between the cathode and the extraction electrode is 0.6 mm, the width of the extraction electrode is 0.3 mm, and the width of the cathode is 0.3 mm, the positioning tolerance is ±.
0.2 mm, and the connection resistance at the connection between the extraction electrode and the cathode always changes.

The thickness of each organic layer of the organic EL device described above is about 50 nm. Each layer is formed by vacuum evaporation. Then, as shown in FIG. 1, except for the end of the extraction electrode 5 and the end of the wiring conductor 4 of the anode 2,
Is covered with a protective layer 10.

[0024]

According to the present invention, in an organic electroluminescence device in which an anode, a hole transport layer, a light emitting layer and a cathode are laminated on a substrate, an extraction electrode is formed on the inner surface of the substrate with a material different from the cathode. Then, a connection end having a line width smaller than that of the extraction electrode was formed at the end of the cathode and connected to the end of the extraction electrode. There is no inconvenience in the connection to, and it is effective as a structure for drawing the cathode of the organic EL element out of the element. In particular, in a graphic type organic EL device having a large number of strip-shaped pattern cathodes, unlike the conventional structure in which the cathode and the extraction electrode are connected via through holes, it is possible to cope with the fine pitch of the cathode,
A particularly remarkable effect is obtained in that there is no problem of displacement of the cathode out of the element.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

FIG. 2 is a plan view showing a connection end portion of a cathode and a connection portion of an extraction electrode in FIG. 1;

FIG. 3 is a cross-sectional view illustrating the structure of a conventional general organic EL element.

FIG. 4 is a cross-sectional view showing an example of the structure of a conventional organic EL element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 5 Extraction electrode 6 Hole transport layer 7 Organic light emitting layer 8 Cathode 9 Connection end

Claims (4)

[Claims] 1. A substrate, an anode provided on an inner surface of the substrate, a hole transport layer formed on the anode, a light emitting layer formed on the hole transport layer, An organic electroluminescence device having a cathode formed on a layer, a lead electrode formed on the inner surface of the substrate with a material different from the cathode, and a line width narrower than the lead electrode at an end of the cathode. And a connection end connected to an end of the extraction electrode. 2. A substrate, a plurality of strip-shaped anodes formed at predetermined intervals on an inner surface of the substrate along a predetermined direction, a hole transport layer formed on the anodes, An organic electroluminescence device having a light emitting layer formed on a hole transport layer, and a plurality of strip-shaped cathodes formed on the light emitting layer at predetermined intervals along a direction intersecting with the anode. In the above, a plurality of extraction electrodes formed of a material different from the cathode and formed substantially in parallel with the cathode on the inner surface of the substrate, and formed at the end of each cathode with a line width smaller than the extraction electrode. An organic electroluminescence element having a connection end connected to an end of each of the extraction electrodes. 3. The extraction electrode has a work function of 4.5 eV.
The organic electroluminescence device according to claim 1, comprising the above material. 4. The material having a work function of 4.5 eV or more,
ITO (Indium Tin Oxide), ZnO:
_{Al, SnO 2: Sb, In} 2 O 3, an organic electroluminescence device according to claim 3, wherein from the group consisting of Au is selected substance.