JPH06342692A - Organic thin film electroluminescent element - Google Patents

Abstract

PURPOSE:To provide the organic thin film electroluminescent element, which can restrict the rise of the driving voltage and the generation of unevenness of light emission and dark spot and of which pattern accuracy is improved an which can perform the display at a high quality and which can be manufactured easily. CONSTITUTION:An organic thin film electroluminescent element consists of a positive electrode 1, a negative electrode 2 and one or plural organic compound layers pinched between both the electrodes. A positive hole filling preventing layer 3 made of organic material is laminated so as to be overlapped with an edge of the positive electrode 1, which is in contact with the organic compound layer, and/or an electron filling preventing layer 4 made of organic material is laminated so as to be overlapped with an edge of the negative electrode 2, which is in contact with the organic compound layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film electroluminescent device which emits light when an electric field is applied.

[0002]

2. Description of the Related Art In recent years, as a color display device for displaying multi-colors in response to an electric signal, an organic thin film electroluminescent device, which is a completely solid type and can obtain high-luminance light emission, has been recently developed and used as a light emitting device in various display devices. Attention has been paid. Since the organic thin film electroluminescent device is made of an organic substance as a raw material, the material constituting the organic thin film electroluminescent device can be selected from various materials, and since it is a completely solid type, it has excellent impact resistance, and can be applied with a low voltage. It has excellent properties such as the ability to emit light, the emission of light with high brightness and high efficiency, and the capability of multicolor display, and active research is being conducted on the materials and structures that make it up. Has been.

The organic thin film electroluminescent device has a structure such as cathode / light emitting layer / hole transport layer / anode, cathode / electron transport layer / light emitting layer / anode, cathode / electron transport layer / light emitting layer / hole transport. Layer / anode, etc. configurations have been developed. Specifically, for example, on a transparent substrate, a plurality of transparent anodes, if necessary a hole transport layer, a light emitting layer, if necessary an electron transport layer,
A plurality of back cathodes intersecting the transparent electrode are laminated in order.

The hole transport layer has a function of facilitating injection of holes from the anode and a function of blocking electrons, while the electron transport layer has a function of facilitating injection of electrons from the cathode. ing. In the light-emitting layer, excitons are generated by recombination of electrons and holes injected from the pair of electrodes, and the excitons emit light in the process of radiation deactivation, and the light passes through the transparent electrode and the transparent substrate. It is released to the outside and can be displayed.

In such an organic thin film electroluminescent device, it is desired to miniaturize the electrode pattern in order to make the device finer, and an interlayer insulating film is formed between the electrodes to maintain the uniformity of light emission. However, a device having improved pattern accuracy has been proposed (Japanese Patent Laid-Open No. 3-250583). In addition, there is also proposed a structure in which an insulating layer is formed between an organic compound layer and an electrode to improve pattern accuracy and display quality (JP-A-3-274694). Furthermore, there has been proposed a structure in which an insulating layer is formed on the edge of the electrode to reduce crosstalk and bleeding of light emission (Japanese Patent Laid-Open No. 4-51494).

However, these organic thin film electroluminescent devices have high driving voltage, uneven light emission in display, and a non-light emitting portion (dark spot) on the light emitting surface in the vicinity of the cathode edge, which causes deterioration of durability. However, there is a drawback that the manufacturing process is very complicated in manufacturing these organic thin film electroluminescent devices.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the drawbacks of the conventional organic thin film electroluminescent device, improves the pattern accuracy, prevents the driving voltage from rising, and prevents uneven light emission and dark spots. It is an object of the present invention to provide an organic thin-film electroluminescent device capable of high quality display without requiring complicated steps in its manufacture.

[0008]

According to the present invention, in an organic thin film electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, at least the anode There is provided an organic thin film electroluminescent device characterized in that a hole injection blocking layer made of an organic substance is laminated so as to overlap an edge portion on the side in contact with an organic compound layer, and an anode and a cathode, and these In an organic thin film electroluminescent device composed of one or more organic compound layers sandwiched therebetween, an electron injection blocking layer made of an organic substance so as to overlap at least the edge of the cathode in contact with the organic compound layer. An organic thin-film electroluminescent device characterized by being laminated with an organic thin film electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween. In the film electroluminescent device, a hole injection blocking layer made of an organic material is laminated so as to overlap the edge of the anode in contact with the organic compound layer, and overlaps with the edge of the cathode in contact with the organic compound layer. There is provided an organic thin film electroluminescent device characterized by laminating an electron injection blocking layer made of an organic substance, and further, a positive electrode laminated so as to overlap with an edge of the anode or the cathode in contact with the organic compound layer. The width of the overlapping portion of the hole injection blocking layer or the electron injection blocking layer with the anode or the cathode is 10% of the width of the anode or the cathode.
The organic thin film electroluminescent device is provided as described above, and the thin film of the hole injection blocking layer or the electron injection blocking layer is 1000 Å or less. A light emitting device is provided.

The inventors of the present invention have conducted extensive studies on the miniaturization of the electrode pattern for high definition of the organic thin film electroluminescent element (hereinafter simply referred to as EL element), and as a result, the transparent electrode as the anode is Note that the electrical resistance is higher than that of the metal electrode, and the wiring resistance due to fine patterning increases, which causes an increase in driving voltage and uneven light emission, and the increase in resistance can be reduced by utilizing the non-light emitting portion. In addition, the generation of dark spots on the light-emitting surface of the device, particularly the vicinity of the cathode edge, which causes deterioration of durability, can be reduced by enhancing the uniformity of the cathode edge in composition and shape. After finding out that, the present invention has been completed.

Hereinafter, the present invention will be described in more detail with reference to the drawings. 1, 2 and 3 show the structures of the anode, cathode, hole injection blocking layer and electron injection blocking layer of the EL device of the present invention. In these drawings, the light emitting layer, the hole transport layer, and the electron transport layer are omitted.

The structure of the EL device of the present invention shown in FIG. 1 is such that the hole injection blocking layer is provided so as to overlap the edge portion of the anode. With this structure, the resistance of the anode can be reduced. Becomes That is, the transparent electrode as an anode has a higher resistance than a metal and causes a rise in driving voltage and uneven light emission as the pattern becomes finer. However, as in the EL element of the present invention, the anode spacing is narrowed. By stacking the hole injection blocking layer on the edge portion, the resistance can be reduced by utilizing the anode portion of the non-light emitting portion.

The width over which the hole injection blocking layer is overlapped is at least 1/10 of the width of the anode and is effective in reducing the resistance. Also, the film thickness of the hole injection blocking layer differs depending on the material, such as withstand voltage and hole injection blocking ability, and the required film thickness also differs. It becomes a generation factor.

Further, as the material used for the hole injection blocking layer, an appropriate material can be used judging from the energy level for hole injection, but by selecting a material whose color is close to black, the non-light emitting portion can be formed. It can be hidden and the display quality can be improved. Specifically, as a material used for the hole injection blocking layer, a conventionally known material that has been used as an electron transport layer material can be used. For example, the oxadiazole derivative shown in Table 1 below is used as an example. I can name it.

[0014]

[Table 1]

The structure of another EL element of the present invention shown in FIG. 2 is such that an electron injection blocking layer is provided so as to overlap the edge portion of the cathode, but this structure has an effect of a dark spot which is a cause of deterioration. Can be suppressed. That is, EL
Dark spots, which are non-light emitting portions appearing on the light emitting surface of the device, are often generated at the edge of the cathode, which is considered to be due to compositional and shape nonuniformity at the edge of the cathode. In this way, the dark spots can be prevented by interposing the cathode spacing and stacking the electron injection blocking layer on the edge portion.

The overlapping width of the electron injection blocking layer is at least 1/10 or more of the width of the cathode, which is effective for avoiding dark spots. The film thickness of the electron injection blocking layer differs depending on the material, such as the withstand voltage and the electron injection blocking ability, and the required film thickness also differs, but if it is not less than 1000 Å or less, a dark spot is generated in the step portion. Cause.

As the material used for the electron injection blocking layer, an appropriate material can be used, judging from the energy level for electron injection, but by selecting a material whose color is close to black, the non-light emitting portion can be hidden and the display quality can be improved. You can also let it. Specifically, as a material used for the electron injection blocking layer,
Conventionally known materials that have been used as hole transport layer materials can be used, and the derivatives shown in Table 2 below can be given as examples.

[0018]

[Table 2]

The structure of yet another EL element of the present invention shown in FIG. 3 is such that a carrier injection blocking layer is provided on each of the edges of both the cathode and the anode. With this configuration, both the reduction of the wiring resistance and the suppression of the dark spot as described above are effective, and a very good electroluminescent device can be obtained.

In the present invention, conventionally known material constitutions can be applied to the substrate, the electrode, the light emitting layer and the carrier injecting and transporting layer.

The hole injection blocking layer and the electron injection blocking layer of the EL device of the present invention are substantially the same in material as the light emitting layer, the hole transporting layer and the electron transporting layer which are the other constituent parts of the device. Therefore, as a manufacturing method thereof, a thin film having a desired film thickness can be formed by a conventional vacuum vapor deposition method, a solution coating method, or the like, and no complicated operation is required for manufacturing the element, which is extremely advantageous in the manufacturing method.

[0022]

The present invention will be described in more detail with reference to the following examples.

Example 1 Using a glass substrate having an anode pattern made of ITO having a width of 2 mm and a pitch of 3.6 mm, as shown in FIG. 1, first, a hole injection blocking layer was formed so that the overlap with the anode was 0.2 mm. It was formed in a pattern with a film thickness of 500Å. Subsequently, a hole transport layer of 500 Å and a light emitting layer of 500 Å are laminated, and finally, a cathode made of an MgAg alloy (MgAg = 10: 1) is similarly laminated with a width of 2 mm and a pitch of 3.6 mm with a film thickness of 2000 Å. Was produced. The material for the hole injection blocking layer and the light emitting layer is Alq ₃ represented by the following structural formula (Formula 1),
As the material of the hole transport layer, TPD represented by the following structural formula (Formula 2) was used. When the device manufactured in this manner was connected to a power source and driven, the brightness variation of each light emitting portion was very small and it was an excellent device.

[0023]

[Chemical 1]

[Chemical 2]

Example 2 Using the same substrate as that used in Example 1, first, as shown in FIG. 2, a hole transport layer TPD and a light emitting layer Alq ³ were each 500 Å.
Laminated. Next, 500 TPD is used as an electron injection blocking layer.
Å It was formed with a width of 2 mm and a pitch of 3.6 mm. Finally M
A gAg cathode 2000Å was similarly formed with a width of 2 mm and a pitch of 3.6 mm so that the overlap with the electron injection blocking layer would be 0.2 mm to prepare an electroluminescent device. In the case of mask vapor deposition, the electron injection blocking layer and the cathode of this embodiment can be formed by using the same mask and shifting their positions. When the device thus produced was connected to a power source and driven, no dark spots, which often existed at the end of the conventional light emitting portion, were observed, and the device was excellent.

Example 3 Using the same substrate as used in Example 1, first, as shown in FIG. 3, Alq ₃ 500Å as a hole injection blocking layer was patterned so that the overlap with the anode was 0.2 mm. Formed. Next, the hole transport layer TPD500Å and the light emitting layer Alq ₃
Laminate 500 Å, and TP as an electron injection blocking layer on top of it
D500Å was formed with a width of 2 mm and a pitch of 3.6 mm.
Finally, the MgAg cathode 2000 Å is also 2 mm wide, 3.
Overlapping with electron injection blocking layer is 0.2mm at 6mm pitch
And an electroluminescent device was manufactured. When the device manufactured in this manner was connected to a power source and driven, it was an excellent device in which there were very few variations in the brightness of each light emitting portion and very few dark spots.

Comparative Example 1 An electroluminescent device was produced in the same manner as in Example 1 except that the hole injection blocking layer in Example 1 was changed to the following. That is, after uniformly forming a SiO ₂ layer by RF magnetron sputtering on a glass substrate having an ITO anode pattern, a resist layer is provided and patterning is performed by photolithography, and then an etching process is performed to inject holes in Example 1. An insulating layer having the same shape as the blocking layer was formed. The characteristics of the element manufactured in this manner were almost the same as those of Example 1, but in the manufacturing process, Example 1 does not require a new apparatus and materials, whereas this Comparative Example is completely opposite. Therefore, the manufacturing process was very complicated.

Comparative Example 2 An electroluminescent device was produced in the same manner as in Example 2 except that the electron injection blocking layer in Example 2 was changed to the following. That is, the electron injection blocking layer in Example 2 is made of Si.
The insulating layer was made of O. At this time, the insulating layer made of SiO had the same shape as the electron injection blocking layer in Example 2 by mask vapor deposition to fabricate an electroluminescence device. When the device produced in this manner was connected to a power source and driven, dark spots were observed at the end of the light emitting portion, which increased with time and were inferior in durability.

[0028]

As described above, the EL element of the present invention is an EL element composed of an anode, a cathode, and one or more organic compound layers sandwiched therebetween, and at least the organic compound of the anode. By stacking a hole injection blocking layer made of an organic material so as to overlap the edge portion on the side in contact with the compound layer, it is possible to suppress an increase in driving voltage and uneven light emission, or at least an organic compound layer of the cathode. By stacking an electron injection blocking layer made of an organic material so that it overlaps with the edge on the side in contact with, it is possible to suppress the generation of dark spots, improve the pattern accuracy, and provide an excellent display of high quality. It is an EL element. Further, the EL device provided with the hole injection blocking layer and the electron injection blocking layer of the present invention,
It exhibits both effects and is extremely excellent. Also, the manufacturing process does not require complicated steps, and is extremely advantageous in terms of manufacturing method.

[Brief description of drawings]

FIG. 1 is a schematic view of an organic thin film electroluminescent device provided with a hole injection blocking layer of the present invention.

FIG. 2 is a schematic view of an organic thin film electroluminescent device provided with an electron injection blocking layer of the present invention.

FIG. 3 is a schematic view of an organic thin film electroluminescent device having a hole injection blocking layer and an electron injection blocking layer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode 2 ... Cathode 3 ... Hole injection blocking layer 4 ... Electron injection blocking layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nozomi Tamoto 1-3-3 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. An organic thin film electroluminescent device comprising an anode and a cathode, and one or a plurality of organic compound layers sandwiched between the anode and the cathode, and at least an edge portion of the anode in contact with the organic compound layer. An organic thin film electroluminescent device, characterized in that a hole injection blocking layer made of an organic material is laminated so as to overlap. 2. An organic thin film electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, at least at the edge of the cathode which is in contact with the organic compound layer. An organic thin film electroluminescent device, characterized in that an electron injection blocking layer made of an organic material is laminated so as to overlap. 3. In an organic thin film electroluminescent device comprising an anode and a cathode and one or more organic compound layers sandwiched between them, the organic thin film electroluminescent element overlaps with an edge of the anode in contact with the organic compound layer. The organic thin film electric field is characterized in that the hole injection blocking layer made of an organic substance is laminated as described above, and the electron injection blocking layer made of an organic substance is laminated so as to overlap the edge of the cathode in contact with the organic compound layer. Light emitting element. 4. The width of the overlapping portion of the hole injection blocking layer or the electron injection blocking layer, which is laminated so as to overlap the edge portion of the anode or the cathode which is in contact with the organic compound layer, with the anode or the cathode. Alternatively, the width of the cathode is 10% or more, and the organic thin film electroluminescent element according to claim 1, 2 or 3. 5. The organic thin film electroluminescent device according to claim 1, wherein the thin film of the hole injection blocking layer or the electron injection blocking layer is 1000 Å or less.