JP3469734B2 - Organic electroluminescence device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device having at least a light-emitting layer using an organic material between a hole injection electrode and an electron injection electrode. And relates to an organic electroluminescent array in which a plurality of such organic electroluminescent elements are juxtaposed, particularly, even when the area of the light emitting portion in the organic electroluminescent element is large, the organic electroluminescent element is uniform and sufficient from the whole organic electroluminescent element. The present invention relates to an organic electroluminescent element and an organic electroluminescent array in which light having luminance is stably emitted, and the organic EL elements arranged side by side are stably emitted with uniform and sufficient luminance. . 2. Description of the Related Art In recent years, with the diversification of information equipment and the like, the need for a flat display element which consumes less power and occupies less space than a conventionally used CRT has been increased. As one of the flat panel display devices, an electroluminescence device has been attracting attention. [0003] Such an electroluminescent element is roughly classified into an inorganic electroluminescent element and an organic electroluminescent element depending on a material to be used. In the case of an inorganic electroluminescent element, a high electric field is generally applied to a light-emitting portion and an electron is emitted. Is accelerated in this high electric field to collide with the emission center, thereby exciting the emission center to emit light. In order to apply such a high electric field, a driving voltage of 100
A high voltage of ~ 200V was required. On the other hand, in the case of an organic electroluminescence element, electrons and holes are respectively injected into a light emitting portion from an electron injection electrode and a hole injection electrode, and the injected electrons and holes are recombined at the emission center. The organic molecules to an excited state, and emit light when the organic molecules return from the excited state to the ground state.
There is an advantage that it can be driven with a voltage as low as possible. [0005] Further, in this organic electroluminescent device, a light emitting device which emits light of various colors can be obtained by appropriately selecting a light emitting material, and it is expected that the organic electroluminescent device can be used as a full color display device. In recent years, various studies have been conducted on the organic electroluminescence device. [0006] The above-mentioned organic electroluminescent element has a three-layer structure called a DH structure in which a hole transport layer, a light emitting layer and an electron transport layer are laminated between a hole injection electrode and an electron injection electrode. And a two-layer structure called an SH-A structure in which a hole transport layer and a light-emitting layer having a high electron transport property are stacked between a hole injection electrode and an electron injection electrode. In general, a two-layer structure called an SH-B structure in which a light-emitting layer rich in hole transporting property and an electron transporting layer are stacked between an electron-injecting electrode and a light-emitting layer is generally used. Here, in such an organic electroluminescence device, when the area of the light emitting portion is increased, the light emission luminance is greatly different in each portion of the organic electroluminescence device, and a lead for supplying electricity to the hole injection electrode is provided. There is a problem that the light emission luminance decreases as the distance from the line connection position increases. In the case where a plurality of organic electroluminescent elements are arranged side by side with a common hole injection electrode so that each organic electroluminescent element emits light in an organic electroluminescent array, In this case, there is a problem that the emission luminance of the organic electroluminescent element decreases as the distance from the connection position of the lead wire for supplying electricity to the hole injection electrode decreases. SUMMARY OF THE INVENTION The present invention relates to an organic electroluminescent device having at least a light-emitting layer using an organic material between a hole injection electrode and an electron injection electrode, and an organic electroluminescent device. It is an object of the present invention to solve the above-described problem in an organic electroluminescence array in which a plurality of electroluminescence elements are arranged in parallel, and even when the area of the organic electroluminescence elements is increased, the entire organic electroluminescence elements can be reduced. In order to stably emit light having uniform and sufficient luminance, and even in an organic electroluminescence array in which a plurality of organic electroluminescence elements are arranged in parallel, light having uniform and sufficient luminance is obtained from each organic electroluminescence element. But emits light stably It is an object of the present invention to ensure that In order to solve the above-mentioned problems, the organic electroluminescent device according to the present invention uses at least an organic material between the hole injection electrode and the electron injection electrode. In the organic electroluminescence element provided with the light emitting layer, a conductive film having a work function smaller than that of the hole injection electrode is provided so as to overlap with a peripheral portion of the hole injection electrode extending outside from the periphery of the light emitting layer. It becomes. Here, when a conductive film having a work function smaller than that of the hole injection electrode is provided so as to partially overlap with the hole injection electrode as in the organic electroluminescence device of the present invention, the conductive film is thus formed. Electricity flows to the hole injection electrode through the overlapped portion, and if this conductive film is provided so as to overlap around the hole injection electrode, even if the area of the organic electroluminescence element is increased, a large amount of the conductive film will pass through the conductive film. Electricity is sufficiently supplied to the entire hole injection electrode in a constant state, and holes are sufficiently injected from the entire hole injection electrode in a constant state, so that light emission of uniform and sufficient brightness is obtained from the entire organic electroluminescence element. Can be obtained. Further, in the organic electroluminescence array according to the present invention, in order to solve the above problems, an organic electroluminescence array having at least a light emitting layer using an organic material between a hole injection electrode and an electron injection electrode. In the organic electroluminescence array in which a plurality of elements are arranged in parallel, a conductive film having a work function lower than that of the hole injection electrode is provided continuously so as to partially overlap the hole injection electrode in each organic electroluminescence element. is there. As in the organic electroluminescence array of the present invention, a conductive film having a work function lower than that of the hole injection electrode is provided continuously so as to partially overlap the hole injection electrode in each organic electroluminescence element. Through this conductive film, electricity is sufficiently supplied to the hole injection electrodes in each organic electroluminescence element in a state where it is constant, and holes are sufficiently injected in each organic electroluminescence element from the hole injection electrode in a constant state. In addition, uniform and sufficient luminance can be obtained in each organic electroluminescence element. In the organic electroluminescence element and the organic electroluminescence array described above, the conductive film having a small work function provided so as to partially overlap the hole injection electrode is a film made of a metal or a metal compound. In particular, it is preferable to use a metal film having good conductivity, such as aluminum, copper, zinc, nickel, chromium, and tungsten. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an organic electroluminescence device and an organic electroluminescence array according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. According to the electroluminescence element, even when the area thereof is increased, uniform and sufficient luminance can be emitted even in the case where the area is increased, and in the organic electroluminescence array, uniform and sufficient luminance can be emitted from each organic electroluminescence element. Make it clear that you will be. (Reference Example) In the organic electroluminescence array of this reference example, as shown in FIG.
A hole injection electrode 12 having a thickness of 1000 ° made of indium-tin oxide (ITO) is provided along the longitudinal direction of the glass substrate 10 on one side of the surface of the glass substrate 10. A conductive film 13 made of aluminum having a work function lower than that of the hole injection electrode 12 and having a thickness of 1000 ° was provided so as to overlap. Then, on the hole injection electrode 12,
As shown in FIGS. 2 and 3, a hole transport layer 14 composed of a triphenylamine derivative (MTDATA) shown in Chemical Formula 1 below and having a thickness of 600 °, and N,
N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine (T
PD) is composed of a light-emitting layer 15 with a thickness of 400 ° doped with 5% by weight of rubrene shown in Chemical Formula ₃ below and a 10-benzo (h) quinolinol-beryllium complex (BeBq ₂ ) shown in Chemical Formula 4 below. Electron transport layer 1 having a thickness of 500 °
6 and the thickness of the aluminum-lithium alloy was 5000 ° on the electron transport layer 16 at a required interval along the longitudinal direction of the electron transport layer 16.
Three electron injection electrodes 17a, 17b, 17c
Organic electroluminescent elements 10a, 10
An organic electroluminescence array in which b and 10c were juxtaposed was obtained. Embedded image Embedded image Embedded image Embedded image In this organic electroluminescence array, a lead wire 18 is connected to one end of the conductive film 13 in the longitudinal direction, and the lead wires 19a, 1b are connected to the electron injection electrodes 17a, 17b, 17c, respectively.
9b and 19c were connected. Here, in fabricating the above-mentioned organic electroluminescence array, the above-mentioned ITO film is formed on the surface of the glass substrate 11 by sputtering, and this ITO film is etched into a predetermined shape by photolithography. The hole injection electrode 12
Was formed. Then, the glass substrate 11 on which the hole injecting electrode 12 is formed is ultrasonically cleaned in acetone for 20 minutes and in ethanol for 20 minutes, and then taken out in boiling ethanol for 1 minute. Then, the glass substrate 11 is placed in a vacuum evaporation apparatus, and the conductive film 1 is dried using a mask.
3 is formed so as to overlap one long side portion of the hole injection electrode 12 as described above, and then the hole transport layer 14, the light emitting layer 15, and the electron transport layer 16 are sequentially formed on the hole injection electrode 12. Finally, the electron injection electrodes 17a, 17b, and 17c were deposited at predetermined positions using a mask. Each of these depositions was performed by a resistance heating deposition method at a degree of vacuum of 1 × 10 ⁻⁵ Torr, a substrate temperature of 20 ° C.,
The deposition was performed at a deposition rate of 2 ° / sec. Comparative Example 1 In the organic electroluminescence array of Comparative Example 1, FIG.
As shown in (B), in the organic electroluminescence array in Example 1 described above, the conductive film 1 provided so as to overlap one long side of the hole injection electrode 12.
3, an organic electroluminescence array was manufactured in the same manner as in Example 1 except that the lead wire 18 was connected to one end of the hole injection electrode 12 in the longitudinal direction. Then, in each of the organic electroluminescence arrays of Reference Example and Comparative Example 1, the conductive film 1
Each of the electron injection electrodes 17a, 17a, and the lead wire 18 connected to one end of the hole injection electrode 12 in the longitudinal direction is plus.
Leads 19a, 19 connected to 17b, 17c
b, 19c are connected to each other to apply a voltage, and each of the organic electroluminescent elements 10a, 10c
The emission luminances at b and 10c were examined, and the results are shown in Table 1 below. In Table 1, the lead wire 1
A1 is the organic electroluminescent element 10a at the position closest to the portion to which 8 is connected, A2 is the organic electroluminescent element 10b at the next closest position, and A3 is the organic electroluminescent element 10c at the farthest position.
As shown. [Table 1] As is apparent from the results, the organic electroluminescent device according to the first embodiment in which the conductive film 13 is provided so as to overlap with one long side portion of the hole injection electrode 12 common to the organic electroluminescent elements 10a, 10b and 10c. In the electroluminescence array, each organic electroluminescence element 10a, 10
Electricity starts to flow into the hole injection electrode 12 of the organic electroluminescent elements 10a and 10c.
As in the organic electroluminescence array of Comparative Example 1 in which electricity is led to the portion of the hole injection electrode 12 in b and 10c, as the distance from the portion where the lead wire 18 is connected increases, the organic electroluminescence device 10
a, 10b, and 10c, each organic electroluminescent element 10
In a, 10b, and 10c, light emission of uniform and sufficient luminance can be obtained. In the organic electroluminescence array in the above reference example, the hole injection electrode 1
The conductive film 13 is provided on the conductive film 2. On the contrary, the hole injection electrode 12 may be provided on the conductive film 13. Further, in the organic electroluminescence array of this reference example, only the electron injection electrodes 17a, 17b and 17c are separated as described above, and the plurality of organic electroluminescence elements 10a, 10b and 10c are separated.
Are arranged side by side, so that a plurality of organic electroluminescent elements 10a, 10b, 10c can be easily arranged side by side. However, the organic electroluminescence array of the present invention is particularly suitable for a plurality of organic electroluminescence elements 1 as shown in this embodiment.
0a, 10b, and 10c are not limited to those arranged side by side.
Similarly to the electron injection electrodes 17a, 17b, and 17c, the hole transport layer 14, the light-emitting layer 15, the electron transport layer 16, and the like are separated to form a plurality of organic electroluminescent elements 10a,
It is also possible to arrange 10b and 10c side by side. (Embodiment) In the organic electroluminescence device of the embodiment, as shown in FIGS.
The same hole injection electrode 12 as that of the first embodiment is provided thereon, and the same conductive film 13 as that of the first embodiment is provided so as to overlap the peripheral portion of the hole injection electrode 12. Hole transport layer 14 and light emitting layer 1
5 and an electron transport layer 16, and an electron injection electrode 17 was provided on the entire surface of the electron transport layer 16. Then, as described above, the hole injection electrode 12
The lead wire 18 is connected to one short side of the conductive film 13 provided around the electron injection electrode 17.
Was connected to a lead wire 19. Comparative Example 2 In the organic electroluminescence device of Comparative Example 2, as shown in FIGS.
In the organic electroluminescent element in
The conductive film 13 is not provided around the hole injection electrode 12, and the lead wire 18 is connected to one short side of the hole injection electrode 12. In the same manner as in the above, an organic electroluminescence device was produced. Then, in each of the organic electroluminescent elements of the above embodiment and comparative example 2, the conductive film 13
Alternatively, the lead wire 18 connected to the hole injection electrode 12
Lead wire 1 connected to the electron injection electrode 17
9 is connected to the negative side, a voltage is applied, each organic electroluminescence element emits light, and a portion B1 close to the lead wire 18 connected to the conductive film 13 or the hole injection electrode 12, a central portion B2, and a lead wire The light emission luminance in a portion B3 distant from the portion to which 18 is connected is examined,
The results are shown in Table 2 below. [Table 2] As is apparent from the results, in the organic electroluminescence device of the second embodiment in which the conductive film 13 is provided around the hole injection electrode 12, electricity is injected through the conductive film 13 around the hole injection electrode 12. Only the light emission luminance at the central portion B2 was slightly reduced, and the difference in the light emission luminance as a whole was small and uniform light emission with sufficient luminance was obtained. On the other hand, in the organic electroluminescence device of Comparative Example 2, light emission of high luminance was obtained in the portion B1 near the position where the lead wire 18 was connected, but the lead wire 18 was connected. As the position became farther from the position, the light emission luminance was greatly reduced, and light emission of uniform and sufficient luminance was not obtained. As described above in detail, in the organic electroluminescence device according to the present invention, a conductive film having a work function smaller than that of the hole injection electrode is provided so as to partially overlap the hole injection electrode. Therefore, electricity flows to the hole injection electrode through such a portion where the conductive film overlaps, and when the conductive film is provided so as to overlap around the hole injection electrode, the area of the organic electroluminescence element is increased. Also in this case, electricity flows well through the conductive film to the entire large hole injection electrode in a state where it is constant, holes are sufficiently injected from the entire hole injection electrode in a constant state, and uniform and sufficient brightness is obtained from the entire organic electroluminescence element. Light emission can now be obtained. Further, since a conductive film having a work function lower than that of the hole injection electrode is provided continuously so as to partially overlap the hole injection electrode in each organic electroluminescence element, the conductive film in each organic electroluminescence element is passed through this conductive film. Electricity flows to the hole injection electrode in a constant state, and holes are sufficiently injected from the hole injection electrode in each organic electroluminescence element in a constant state, and light emission of uniform and sufficient luminance is obtained in each organic electroluminescence element. Can now be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a state in which a hole injection electrode and a conductive film are provided on a glass substrate in an organic electroluminescence array according to Embodiment 1 of the present invention. FIG. 2 is a plan view showing an organic electroluminescence array according to the first embodiment. FIG. 3 is a schematic diagram showing a stacked state of the organic electroluminescence array in the above-mentioned Example 1. FIGS. 4A and 4B are a plan view and a schematic view showing a stacked state of an organic electroluminescence array in Comparative Example 1. FIGS. FIGS. 5A and 5B are a plan view and a schematic view showing a stacked state of an organic electroluminescence element according to a second embodiment of the present invention. FIGS. 6A and 6B are a plan view and a schematic view showing a stacked state of an organic electroluminescence element in Comparative Example 2. DESCRIPTION OF SYMBOLS 10a, 10b, 10c Organic electroluminescence element 12 Hole injection electrode 13 Conductive film 15 Light emitting layer 17, 17a, 17b, 17c Electron injection electrode

Continuation of the front page (56) References JP-A-5-307997 (JP, A) JP-A-4-82197 (JP, A) JP-A-8-244272 (JP, A) JP-A-5-226076 (JP) , A) Japanese Utility Model 3-107861 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name)

Claims (1)

(57) [Claims 1] Between a hole injection electrode and an electron injection electrode
At least a light emitting layer using an organic material is provided.
In the electroluminescent element,
A conductive film having a smaller work function than that of the
Overlap with the periphery of the hole injection electrode extending outside from the periphery
Organic elect, characterized by being provided so that
Luminescent element .